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1.
Sci Rep ; 12(1): 7350, 2022 05 05.
Artigo em Inglês | MEDLINE | ID: mdl-35513473

RESUMO

The Octodon degus is a South American rodent that is receiving increased attention as a potential model of aging and sporadic late-onset Alzheimer's disease (AD). Impairments in spatial memory tasks in Octodon degus have been reported in relation to either advanced AD-like disease or hippocampal lesion, opening the way to investigate how the function of hippocampal networks affects behavior across AD stages. However, no characterization of hippocampal electrophysiology exists in this species. Here we describe in young, healthy specimens the activity of neurons and local field potential rhythms during spatial navigation tasks with and without objects. Our findings show similarities between the Octodon degus and laboratory rodents. First, place cells with characteristics similar to those found in rats and mice exist in the CA1 subfield of the Octodon degus. Second, the introduction of objects elicits novelty-related exploration and an increase in activity of CA1 cells, with location specific and unspecific components. Third, oscillations of the local field potential are organized according to their spectral content into bands similar to those found in laboratory rodents. These results suggest a common framework of underlying mechanisms, opening the way to future studies of hippocampal dysfunction in this species associated to aging and disease.


Assuntos
Doença de Alzheimer , Octodon , Envelhecimento/fisiologia , Doença de Alzheimer/patologia , Animais , Modelos Animais de Doenças , Hipocampo/patologia , Camundongos , Ratos
2.
Steroids ; 184: 109037, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-35429494

RESUMO

Cortisol resistance has also been reported in the degu, Octodon degus, a New World hystricomorph endemic to central Chile. The degu is used as a model for studies of stress and diurnal rhythms, parental behaviour and female masculinization. Another New World hystricomorph, the guinea pig, also exhibits glucocorticoid resistance, a result of amino acid sequences that differ from other mammalian glucocorticoid receptors (GR). Mutations in the ligand-binding domain of the human GR have been identified in familial or sporadic generalised cortisol resistance as have variants in the guinea pig. To address the possibility that the high levels of cortisol observed in the degu are a result of the same or similar sequence variations observed in the guinea pig GR, we have cloned, expressed and characterised the ligand-binding domain (LBD) of the degu GR. Somewhat unexpectedly, neither the amino acids nor the region involved in the resistance observed in the guinea pig GR are relevant in the degu GR. The relative resistance to cortisol observed in the degu GR is conferred by the substitution of two isoleucine residues, which are highly conserved in the GR across species, with a valine doublet. These amino acids lie in the region between helices 5 and 6 of the GR LBD, a region known to be important in determining the affinity of ligand-binding in steroid receptors.


Assuntos
Octodon , Aminoácidos , Animais , Feminino , Cobaias , Hidrocortisona/metabolismo , Ligantes , Octodon/metabolismo , Receptores de Glucocorticoides/genética
3.
Anim Cogn ; 25(1): 33-41, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34156548

RESUMO

Phobia against spiders or snakes is common in humans, and similar phobia-like behaviors have been observed in non-human animals. Visual images of snakes elicit phobia in humans, but sensory modalities that cause snake aversion in non-human animals are not well examined. In this study, we examined visually induced snake aversion in two rodent species. Using a three-compartment experimental chamber, reactions to images of snakes were compared between the diurnal precocious rodent Octodon degus and nocturnal laboratory mice. The snakes whose images were presented do not live in the original habitats of degus or mice. Snake aversion was assessed by presenting snake vs. no-image, snake vs. flower, snake vs. degu, and snake vs. mouse images. The time spent in a compartment with the snake image and with the non-snake images were measured. Degus avoided images of snakes in every tests. In contrast, mice did not display snake aversion. Degus are diurnal animals, i.e., visual information is important for their survival. Since mice are nocturnal, visual information is less important for survival. Such behavioral differences in the two species may explain the difference in visually induced aversion to snakes. A principal component analysis of the stimulus images suggests that elementary cues, such as color, do not explain the differences in the species' aversion to snakes. Finally, snake aversion in degus suggests that aversion is innate, since the animals were born and raised in a laboratory.


Assuntos
Aprendizagem da Esquiva , Octodon , Animais , Ritmo Circadiano , Camundongos , Camundongos Endogâmicos C57BL , Serpentes
4.
J Vet Diagn Invest ; 34(1): 126-129, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34515595

RESUMO

A 5-y-old, male degu (Octodon degus) was presented with a subcutaneous mass in the ventral aspect of the cervical area. The mass was removed surgically. Histologically, the mass was a densely cellular, expansile neoplasm, with compression of thymic tissue to the periphery. The neoplasm consisted of solid sheets of polygonal cells, mixed with fewer small lymphocytes. Rare Hassall bodies were scattered throughout the mass. Polygonal cells were positive for anti-keratin/cytokeratin AE1/AE3 antibody, and small lymphocytes were positive for anti-CD3 antibody. The histopathologic and immunohistochemical findings were consistent with a thymoma. In addition, an autopsy revealed myxosarcoma of the right thoracic wall with metastasis to the lung. To our knowledge, thymoma originating from the cervical component of the thymus has not been documented previously in a rodent species.


Assuntos
Octodon , Doenças dos Roedores , Timoma , Neoplasias do Timo , Animais , Masculino , Roedores , Timoma/cirurgia , Timoma/veterinária , Neoplasias do Timo/cirurgia , Neoplasias do Timo/veterinária
5.
J Vet Med Sci ; 83(12): 1805-1811, 2021 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-34670920

RESUMO

The degu has drawn increasing attention for use as an experimental animal in stress response studies due to its physiological features, such as diurnality and seasonal breeding, which differ from conventional laboratory rodents. Stress response is elicited by steroid hormones secreted by the adrenal gland, whose functions are controlled by pituitary hormones reaching through the adrenal arteries. However, knowledge of the arterial anatomy of the degu adrenal gland remains insufficient. To address this issue, we observed adrenal arteries in 20 male degus injected with red-colored latex. Adrenal arterial branching patterns were classified into Types 1-4, which respectively have 1 to 4 parent arteries that give rise to the adrenal arteries. Based on the combination of the parent arteries, Types 2 and 3 were categorized into subtypes a to c, while Type 4 was categorized into subtypes a and b. On the left side, Type 2 (45%) and Type 3 (45%) were predominant, whereas Type 1 (5%) and Type 4 (5%) were infrequent. On the right side, Type 2 (50%) and Type 3 (45%) were predominant, whereas Type 4 (5%) was infrequent. Type 1 was not present. There were 0 to 4 cranial, 1 to 4 middle and 1 to 4 caudal adrenal arteries, with the total number varying from 2 to 9. The present observation provides knowledge of comparative anatomical features of the degu adrenal arteries, which can serve as an anatomical basis for comparative endocrinological studies.


Assuntos
Octodon , Abdome , Glândulas Suprarrenais , Animais , Artérias , Masculino , Roedores
6.
Horm Behav ; 134: 105011, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34130042

RESUMO

Because residents and immigrants from group living species may experience fitness costs associated with permanent changes in group membership, we examined the hypothesis that females experiencing socially unstable or socially stable conditions during development compensate these costs by shaping the phenotype of their own offspring differently. Groups of adult females experiencing either socially stable or unstable conditions in the early social environment were assigned to either socially stable or unstable conditions in the social environment as adults. We quantified affiliative and agonistic interactions among the females during pregnancy and lactation of the focal female, maternal and allomaternal care, hypothalamic-anterior pituitary-adrenal axis (HPA) acute stress response, and early offspring growth. Social instability during breeding enhanced agonistic interactions among adult females, and offspring that experienced socially unstable conditions exhibited enhanced offspring care, regardless of adult environments. Neither social behavior, offspring care, acute stress physiology, nor early growth was influenced by early or adult social stability conditions. These findings imply that socially unstable conditions prime developing females to shape the phenotype of their offspring to prevent negative effects of socially unstable environments.


Assuntos
Octodon , Animais , Feminino , Sistema Hipotálamo-Hipofisário , Fenótipo , Sistema Hipófise-Suprarrenal , Gravidez , Comportamento Social
7.
Physiol Behav ; 238: 113487, 2021 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-34087278

RESUMO

Parents in many animal species provide care to their offspring as a mechanism to enhance their own fitness. In mammals, this behavior is expressed mostly by the females, but also by males of some species. Proximally, rates of paternal offspring care have been linked to organizational and activational effects of testosterone. Specifically, intrauterine position of male fetuses is associated with differential exposure to testosterone, leading to development of males with different levels of masculinization (assessed through differences in the length of the anogenital distance (AGD). The relative roles played by organizational and activational effects of testosterone on male parental care remain unclear. In this study, we aimed to determine if male sex-biased uterine environment and testosterone levels across the breeding period explain variation in paternal care in the social rodent, Octodon degus. Neither quantity (time with the offspring) nor quality (frequency of grooming and retrieving) of paternal care was affected by male sex-biased uterine environment, nor did paternal care significantly differ across the different stages of male reproduction. In contrast, paternal care was associated with maternal care. Quantity of male care decreased with increasing quantity of maternal care, and quality of male care increased with increasing quality of maternal care. While serum testosterone did not differ between males with different sex-biased uterine environment, male testosterone tended to increase during mating and decrease when pregnant females or offspring were present.


Assuntos
Octodon , Animais , Feminino , Masculino , Gravidez , Reprodução , Roedores , Testosterona
8.
PLoS One ; 16(4): e0250219, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33882104

RESUMO

Many animals become more motivated to interact after a period of isolation. This phenomenon may involve general drives, e.g. for social touch or companionship, as well as drives that are specific to particular peers, and which ultimately serve to reestablish relationships between the individuals. Female degus are known to be affiliative with multiple other individuals, including unrelated and unfamiliar conspecifics, offering an opportunity to study social motivation independent from exclusive pair-bonds or overt, same-sex competition. We attempted to disentangle factors driving peer interaction by examining reunion behavior across several social isolation and separation manipulations. High levels of interaction were observed between adult females who had been separated even without isolation, revealing a drive to re-establish relationships with specific peers. The content of separation-only reunions differed from isolation, with the latter involving more early-session interaction, higher levels of allogrooming before rear-sniffing, and a higher ratio of chitter vocalizations. To assess whether post-isolation behavior was related to stress, we examined reunions following a non-social (footshock) stressor. Like isolation, footshock increased early-session interactions, but did not increase allogrooming before rear-sniffing or chittering, as compared with controls. To test whether separation-only reunion behavior shared qualities with relationship formation, we also examined reunions of new (stranger) dyads. Strangers exhibited higher levels of interaction than cagemates, with particularly high levels of late-session rear-sniffing. Like separation-only reunions, strangers showed more non-chitter vocalizations and lower levels of allogrooming before rear-sniffing. Across experiments, an exploratory clustering method was used to identify vocalizations that differed between conditions. This yielded promising leads for future investigation, including a chaff-type syllable that may have been more common during relationship renewal. Overall, results are consistent with the hypothesis that female degu reunions are supported by both general and peer-stimulus specific drives, expressed through the structure of physical and vocal interactions over time.


Assuntos
Comportamento Animal/fisiologia , Motivação/fisiologia , Octodon/fisiologia , Animais , Feminino , Ligação do Par , Grupo Associado , Comportamento Social , Isolamento Social
9.
Int J Mol Sci ; 22(9)2021 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-33919373

RESUMO

The diurnal rodent Octodon degus (O. degus) is considered an attractive natural model for Alzheimer's disease and other human age-related features. However, it has not been explored so far if the O. degus could be used as a model to study Parkinson's disease. To test this idea, 10 adult male O. degus were divided into control group and MPTP-intoxicated animals. Motor condition and cognition were examined. Dopaminergic degeneration was studied in the ventral mesencephalon and in the striatum. Neuroinflammation was also evaluated in the ventral mesencephalon, in the striatum and in the dorsal hippocampus. MPTP animals showed significant alterations in motor activity and in visuospatial memory. Postmortem analysis revealed a significant decrease in the number of dopaminergic neurons in the ventral mesencephalon of MPTP animals, although no differences were found in their striatal terminals. We observed a significant increase in neuroinflammatory responses in the mesencephalon, in the striatum and in the hippocampus of MPTP-intoxicated animals. Additionally, changes in the subcellular expression of the calcium-binding protein S100ß were found in the astrocytes in the nigrostriatal pathway. These findings prove for the first time that O. degus are sensitive to MPTP intoxication and, therefore, is a suitable model for experimental Parkinsonism in the context of aging.


Assuntos
1-Metil-4-Fenil-1,2,3,6-Tetra-Hidropiridina/efeitos adversos , Comportamento Animal/efeitos dos fármacos , Modelos Animais de Doenças , Inflamação/patologia , Intoxicação por MPTP/patologia , Neurotoxinas/toxicidade , Transtornos Parkinsonianos/patologia , Animais , Neurônios Dopaminérgicos/efeitos dos fármacos , Neurônios Dopaminérgicos/patologia , Inflamação/etiologia , Intoxicação por MPTP/etiologia , Masculino , Neostriado/efeitos dos fármacos , Neostriado/patologia , Octodon , Transtornos Parkinsonianos/etiologia
10.
Vet Parasitol ; 293: 109430, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33901932

RESUMO

Ectoparasite infestations are not common in degus. Two cases are presented here where use of Stronghold® Plus/Revolution® Plus (selamectin and sarolaner topical solution) was successfully administered to a degu (Octodon degus) for treatment of naturally-occurring mite infesations. Selamectin (Stronghold®/Revolution®) has been demonstrated to be effective against naturally-occurring mite infections in dogs and selamectin is approved for use in dogs for the treatment of sarcoptic mange (caused by Sarcoptes scabiei) at a dose of 6 mg/kg. In the first case, a 2.6-years-old female degu housed in a group with four other degus was presented with pruritic skin reactions, restlessness and hairloss. Mites morphologically similar to Demodex sp. were detected in the deep skin scrapings. All four degus were treated with Stronghold® Plus/Revolution® Plus (30 mg/kg selamectin and 5 mg/kg sarolaner) once a week for a total of six treatments. The spot-on was administered topically on the dorsal cervical region. Following treatment the degu presenting with clinical signs showed a rapid improvement with the pruritus and overall dermatitis resolving within 2 weeks of treatment. Skin scrapes and microscopic examination of epidermal debris collected from the affected degu were negative for mites from day 14 onwards. In the second case, a group of four 4-6.5-years-old female and male degus that were housed together were infested with Ornithonyssus bacoti. All animals were treated with 30 mg/kg selamectin and 5 mg/kg sarolaner in four total weekly doses. One week later no living mites were found on the patients or in their environment. The four degus improved visibly, and within three weeks of treatment the skin lesions associated with the infestation subsided. The antiparasiticides showed a satisfactory efficacy and were well tolerated (n = 9 animals treated in a total).


Assuntos
Azetidinas , Ivermectina/análogos & derivados , Infestações por Ácaros , Octodon , Doenças dos Roedores , Compostos de Espiro , Administração Tópica , Animais , Antiparasitários/farmacologia , Antiparasitários/uso terapêutico , Azetidinas/farmacologia , Azetidinas/uso terapêutico , Feminino , Ivermectina/farmacologia , Ivermectina/uso terapêutico , Masculino , Infestações por Ácaros/tratamento farmacológico , Infestações por Ácaros/veterinária , Ácaros/efeitos dos fármacos , Octodon/parasitologia , Doenças dos Roedores/tratamento farmacológico , Compostos de Espiro/farmacologia , Compostos de Espiro/uso terapêutico , Resultado do Tratamento
11.
Biochem Biophys Res Commun ; 551: 54-62, 2021 04 30.
Artigo em Inglês | MEDLINE | ID: mdl-33721831

RESUMO

Octodon degus is said to be one of the most human-like rodents because of its improved cognitive function. Focusing on its high sociality, we cloned and characterized some sociality-related genes of degus, in order to establish degus as a highly socialized animal model in molecular biology. We cloned degus Neurexin and Neuroligin as sociality-related genes, which are genetically related to autism spectrum disorder in human. According to our results, amino acid sequences of Neurexin and Neuroligin expressed in degus brain, are highly conserved to that of human sequences. Most notably, degus Neuroligin4 is highly similar to human Neuroligin4X, which is one of the most important autism-related genes, whereas mouse Neuroligin4 is known to be poorly similar to human Neuroligin4X. Furthermore, our work also indicated that testosterone directly binds to degus Neurexin and intercepts intercellular Neurexin-Neuroligin binding. Moreover, it is of high interest that testosterone is another key molecule of the higher incidence of autism in male. These results indicated that degus has the potential for animal model of sociality, and furthermore may promote understanding toward the pathogenic mechanism of autism.


Assuntos
Moléculas de Adesão Celular Neuronais/metabolismo , Octodon/metabolismo , Receptores de Superfície Celular/metabolismo , Testosterona/metabolismo , Animais , Transtorno do Espectro Autista/genética , Transtorno do Espectro Autista/metabolismo , Proteínas de Ligação ao Cálcio/química , Moléculas de Adesão Celular Neuronais/química , Moléculas de Adesão Celular Neuronais/genética , Hipocampo/metabolismo , Humanos , Masculino , Moléculas de Adesão de Célula Nervosa/química , Ligação Proteica/efeitos dos fármacos , Domínios Proteicos , Receptores de Superfície Celular/química , Globulina de Ligação a Hormônio Sexual/química , Testosterona/farmacologia
12.
Mol Phylogenet Evol ; 159: 107111, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33607277

RESUMO

As currently understood, the genus Octodon contains five species degus, lunatus, bridgesii, pacificus, and ricardojeda. Previous phylogenetic studies suggest that genus specific diversity is underestimated. In order to evaluate the taxonomic diversity of Octodon, we implemented unilocus (cytochrome-b) and multilocus (cytochrome-b + 4 nuclear genes) species delimitation methods. Octodon degus was recovered as a sister of the other species of the genus. The unilocus bGMYC and mPTP methods, based on cytochrome-b sequences, delimits 11 and 7 candidate species respectively, and both methods fail to recognize O. pacificus from O. ricardojeda. Results of the multilocus analysis (BPP) vary as a function of the dataset used. When the five genes are used 11 species are delimited, while eight species are delimited when only the nuclear genes are used. Octodon bridgesii is shown as comprising at least two species (one on the Pacific coast and the typical form found on the Andean slopes), while O. ricardojeda may comprise two species (one on the Chilean side of the Andes and the other in Argentina). Likewise, both multilocus matrices recover O. pacificus as a distinct species. This shows that species diversity of Octodon is underestimated. Remarkably, many of the delimited species based on genetic data are morphologically differentiated in cranio-dental characteristics. However, a pair of species has not achieved morphological differentiation, being cryptic species. Finally, the incongruence between mitochondrial and nuclear phylogenies suggests that processes such as incomplete lineage sorting and/or introgression have been present during the radiation of the genus.


Assuntos
Especiação Genética , Octodon/classificação , Filogenia , Animais , Argentina , Teorema de Bayes , Chile , Funções Verossimilhança , Tipagem de Sequências Multilocus , Filogeografia
13.
J Exp Zool A Ecol Integr Physiol ; 335(2): 239-249, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33184965

RESUMO

Environmental conditions experienced by developing animals have an impact on the development and maturity of the immune system. Specifically, the diet experienced during early development influences the maintenance and function of the immune system in young and adult animals. It is well known that exposure to low-protein diets during early development are related to an attenuation of immunocompetence in adulthood. While this functional linkage has been widely studied in altricial models' mammals, it has been little explored how the nutritional history modulates the immune function in precocial animals. We evaluated the effect of dietary protein consumed during early development on the immune function and the oxidative costs in the precocial Caviomorph rodent Octodon degus, or degu. We evaluated components of the acute phase response (APR) and oxidative parameters before and after immune challenge. We found that after the immune challenge, the juveniles on the low-protein dietary treatment exhibited an attenuation of body temperature but showed higher levels of lipid peroxidation than juvenile degus on the high-protein diet. We did not find a significant effect of the interaction between diet and immune challenge on body mass, levels of inflammatory proteins, nor in the total antioxidant capacity. Our results suggest that some components of the immune function and the oxidative status in the degu can be modulated by diet during development. However, the modulation would depend on the immune variables analyzed, and the characteristics of the immune system of precocial rodents.


Assuntos
Ração Animal/análise , Dieta/veterinária , Proteínas na Dieta/administração & dosagem , Octodon/imunologia , Octodon/fisiologia , Fenômenos Fisiológicos da Nutrição Animal , Animais , Comportamento Alimentar , Octodon/crescimento & desenvolvimento , Estresse Oxidativo
14.
Ageing Res Rev ; 64: 101204, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-33152453

RESUMO

Integrating the multifactorial processes co-occurring in both physiological and pathological human conditions still remains one of the main challenges in translational investigation. Moreover, the impact of age-associated disorders has increased, which underlines the urgent need to find a feasible model that could help in the development of successful therapies. In this sense, the Octodon degus has been indicated as a 'natural' model in many biomedical areas, especially in ageing. This rodent shows complex social interactions and high sensitiveness to early-stressful events, which have been used to investigate neurodevelopmental processes. Interestingly, a high genetic similarity with some key proteins implicated in human diseases, such as apolipoprotein-E, ß-amyloid or insulin, has been demonstrated. On the other hand, the fact that this animal is diurnal has provided important contribution in the field of circadian biology. Concerning age-related diseases, this rodent could be a good model of multimorbidity since it naturally develops cognitive decline, neurodegenerative histopathological hallmarks, visual degeneration, type II diabetes, endocrinological and metabolic dysfunctions, neoplasias and kidneys alterations. In this review we have collected and summarized the studies performed on the Octodon degus through the years that support its use as a model for biomedical research, with a special focus on ageing.


Assuntos
Doença de Alzheimer , Diabetes Mellitus Tipo 2 , Octodon , Envelhecimento , Animais , Modelos Animais de Doenças , Multimorbidade
15.
Sci Rep ; 10(1): 18315, 2020 10 27.
Artigo em Inglês | MEDLINE | ID: mdl-33110163

RESUMO

Social isolation is considered a stressful situation that results in increased physiological reactivity to novel stimuli, altered behaviour, and impaired brain function. Here, we investigated the effects of long-term social isolation on working memory, spatial learning/memory, hippocampal synaptic transmission, and synaptic proteins in the brain of adult female and male Octodon degus. The strong similarity between degus and humans in social, metabolic, biochemical, and cognitive aspects, makes it a unique animal model that can be highly applicable for further social, emotional, cognitive, and aging studies. These animals were socially isolated from post-natal and post-weaning until adulthood. We also evaluated if re-socialization would be able to compensate for reactive stress responses in chronically stressed animals. We showed that long-term social isolation impaired the HPA axis negative feedback loop, which can be related to cognitive deficits observed in chronically stressed animals. Notably, re-socialization restored it. In addition, we measured physiological aspects of synaptic transmission, where chronically stressed males showed more efficient transmission but deficient plasticity, as the reverse was true on females. Finally, we analysed synaptic and canonical Wnt signalling proteins in the hypothalamus, hippocampus, and prefrontal cortex, finding both sex- and brain structure-dependent modulation, including transient and permanent changes dependent on stress treatment.


Assuntos
Encéfalo/fisiologia , Cognição/fisiologia , Octodon/fisiologia , Isolamento Social , Animais , Feminino , Hipocampo/fisiologia , Estudos Longitudinais , Masculino , Memória de Curto Prazo/fisiologia , Octodon/psicologia , Teste de Campo Aberto/fisiologia , Isolamento Social/psicologia , Aprendizagem Espacial/fisiologia
16.
Sci Rep ; 10(1): 16220, 2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-33004866

RESUMO

The parabigeminal nucleus (PBG) is the mammalian homologue to the isthmic complex of other vertebrates. Optogenetic stimulation of the PBG induces freezing and escape in mice, a result thought to be caused by a PBG projection to the central nucleus of the amygdala. However, the isthmic complex, including the PBG, has been classically considered satellite nuclei of the Superior Colliculus (SC), which upon stimulation of its medial part also triggers fear and avoidance reactions. As the PBG-SC connectivity is not well characterized, we investigated whether the topology of the PBG projection to the SC could be related to the behavioral consequences of PBG stimulation. To that end, we performed immunohistochemistry, in situ hybridization and neural tracer injections in the SC and PBG in a diurnal rodent, the Octodon degus. We found that all PBG neurons expressed both glutamatergic and cholinergic markers and were distributed in clearly defined anterior (aPBG) and posterior (pPBG) subdivisions. The pPBG is connected reciprocally and topographically to the ipsilateral SC, whereas the aPBG receives afferent axons from the ipsilateral SC and projected exclusively to the contralateral SC. This contralateral projection forms a dense field of terminals that is restricted to the medial SC, in correspondence with the SC representation of the aerial binocular field which, we also found, in O. degus prompted escape reactions upon looming stimulation. Therefore, this specialized topography allows binocular interactions in the SC region controlling responses to aerial predators, suggesting a link between the mechanisms by which the SC and PBG produce defensive behaviors.


Assuntos
Comportamento Animal/fisiologia , Reação de Fuga/fisiologia , Medo/fisiologia , Vias Neurais/fisiologia , Octodon/fisiologia , Colículos Superiores/fisiologia , Teto do Mesencéfalo/fisiologia , Animais , Mapeamento Encefálico , Feminino , Masculino , Optogenética
17.
Exp Parasitol ; 215: 107931, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32464222

RESUMO

Chagas disease is a public health problem in America. Its parasite, Trypanosoma cruzi, presents different discrete typing units (DTUs), colonizes organs of mammalian hosts in chronic infections, and presents tropism for particular organs in experimental infections. We evaluated T. cruzi tropism towards organs on the naturally infected rodent Octodon degus, identifying the parasites' DTUs, by means of conventional PCR and hybridization. Almost all the analyzed organs presented T. cruzi. More than 42% of the tested oesophagus, skin, skeletal muscle, brain and intestine showed T. cruzi DNA. Other nine types of organs were infected in over 15%. These results suggest that there is some tropism by T. cruzi in chronically infected O. degus. DTU TcV was present in 92.5% of infected organs with identified DTUs; this DTU is frequently reported in human infections in the Southern Cone of South America. Few organs showed mixed DTU infections. This is one of the few reports on the outcome of chronic natural T. cruzi-infection in wild mammal hosts exposed to naturally infected vectors.


Assuntos
Doença de Chagas/veterinária , Octodon/parasitologia , Doenças dos Roedores/patologia , Doenças dos Roedores/parasitologia , Animais , Animais Selvagens , Doença de Chagas/parasitologia , Doença de Chagas/patologia , DNA de Protozoário/isolamento & purificação , Feminino , Masculino , Trypanosoma cruzi/classificação , Trypanosoma cruzi/genética
18.
Sci Rep ; 10(1): 5888, 2020 04 03.
Artigo em Inglês | MEDLINE | ID: mdl-32246090

RESUMO

Amyloid plaques composed of Aß amyloid peptides and neurofibrillary tangles are a pathological hallmark of Alzheimer's disease. In situ identification of early-stage amyloid aggregates in Alzheimer's disease is relevant for their importance as potential targets for effective drugs. Synchrotron-based infrared imaging is here used to identify early-stage oligomeric/granular aggregated amyloid species in situ in the brain of APP/PS1 transgenic mice and Octodon degus for the first time. Also, APP/PS1 mice show fibrillary aggregates at 6 and 12 months whereas very little formation of fibrils is found in aged Octodon degus. Finally, significant decreased burden of early-stage aggregates and fibrillary aggregates is obtained following treatment with G4-His-Mal dendrimers (a neurodegenerative protector) in 6-month-old APP/PS1 mice, thus demonstrating putative therapeutic properties of G4-His-Mal dendrimers in AD models. Identification, localization, and characterization using infrared imaging of these non-fibrillary species in the cerebral cortex at early stages of AD progression in transgenic mice point to their relevance as putative pharmacological targets. No less important, early detection of these structures may be useful in the search for markers for non-invasive diagnostic techniques.


Assuntos
Doença de Alzheimer/patologia , Placa Amiloide/patologia , Fatores Etários , Doença de Alzheimer/diagnóstico , Animais , Encéfalo/patologia , Modelos Animais de Doenças , Masculino , Camundongos , Camundongos Transgênicos , Octodon , Espectroscopia de Infravermelho com Transformada de Fourier , Síncrotrons
19.
Behav Processes ; 174: 104102, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32145271

RESUMO

Group-living animals vary in social behavior across multiple dimensions, including in the selectivity of social interactions with familiar versus unfamiliar peers. Standardized behavioral tests can be used to tease apart different dimensions of behavior. These serve a dual function-on one hand, helping to isolate behavioral factors that may support collective behavior in natural habitats, and, on another, providing a basis for comparative approaches to understanding physiological mechanisms of behavior. Degus (Octodon degus) are South American caviomorph rodents that nest and forage in groups with relatively low genetic relatedness. Flexibility in group membership is likely supported by gregariousness toward strangers, but the relative preference for strangers compared with familiar individuals has not been systematically tested. We assessed the specificity of social preferences in female degus using a same-sex partner preference test. Degus huddled extensively with both familiar and unfamiliar peers, with no average preference for one over the other. Detailed analysis of social interactions demonstrated an effect of familiarity on social investigation and aggressive behaviors, indicating that degus distinguished between familiar and unfamiliar conspecifics, even though it did not impact huddling. This behavioral profile is thus far unique to degus; in similar tests, meadow and prairie voles exhibit strong partner preferences for known peers, while mice exhibit low social huddling and spend relatively less time in social chambers. Understanding how group-living species differ in specific aspects of social behavior such as familiarity/novelty preference and propensity for social contact will offer a foundation to interpret differences in neural systems supporting sociality.


Assuntos
Comportamento de Escolha , Octodon/psicologia , Reconhecimento Psicológico , Comportamento Social , Animais , Comportamento Animal , Feminino , Camundongos
20.
Ticks Tick Borne Dis ; 11(3): 101385, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32014466

RESUMO

A new argasid (Argasidae) tick is herein described based on morphology and molecular data obtained from larvae parasitizing Octodon degus and from ticks collected inside burrows in northern Chile. Unfed laboratory-reared larvae were mounted in slides for morphometrical and morphological analyses. Larvae of Ornithodoros octodontus n. sp. share morphological traits with Ornithodoros quilinensis and Ornithodoros xerophylus, two species associated with rodents in the Argentinean Chaco. However, a longer hypostome with two rows of 21 and 22 denticles each one, and conspicuous leaf-shaped anal plates separate O. octodontus. While nymphal stages of O. octodontus lack cheeks and possess a micromammillated dorsal integument, adults have cheeks and exhibit markedly irregular mammillae along their dorsal surface. Phylogenetic analyses of neotropical Argasidae based on mitochondrial 16S rDNA sequences point that O. octodontus forms a monophyletic group with O. xerophylus and an unidentified Ornithodoros sp. from Bolivia, all of them associated with burrow-dweller rodents. Ornithodoros aragaoi and Ornithodoros davisi, two rare species collected once only in the Peruvian Andean Plateau during 1955 are morphologically closely related with adults and nymphs of O. octodontus. Biological observations of O. octodontus revealed autogenic females. For the moment, subgeneric classification of this new species depends on further biological studies. The fauna of ticks occurring in Chile is now represented by 22 species, 11 belonging to the Argasidae family.


Assuntos
Octodon , Ornithodoros/classificação , Doenças dos Roedores/parasitologia , Infestações por Carrapato/veterinária , Animais , Chile , Feminino , Larva/anatomia & histologia , Larva/classificação , Larva/crescimento & desenvolvimento , Larva/ultraestrutura , Masculino , Microscopia Eletrônica de Varredura/veterinária , Ninfa/anatomia & histologia , Ninfa/classificação , Ninfa/crescimento & desenvolvimento , Ninfa/ultraestrutura , Ornithodoros/anatomia & histologia , Ornithodoros/crescimento & desenvolvimento , Ornithodoros/ultraestrutura , Infestações por Carrapato/parasitologia
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