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1.
CNS Neurosci Ther ; 28(6): 922-931, 2022 06.
Artigo em Inglês | MEDLINE | ID: mdl-35238164

RESUMO

AIMS: The molecular genetic mechanisms underlying postoperative nausea and vomiting (PONV) in the brain have not been fully elucidated. This study aimed to determine the changes in whole transcriptome in the nucleus of the solitary tract (NTS) in an animal model of PONV, to screen a drug candidate and to elucidate the molecular genetic mechanisms of PONV development. METHODS: Twenty-one female musk shrews were assigned into three groups: the Surgery group (shrew PONV model, n = 9), the Sham group (n = 6), and the Naïve group (n = 6). In behavioral studies, the main outcome was the number of emetic episodes. In genetic experiments, changes in the transcriptome in the NTS were measured. In a separate study, 12 shrews were used to verify the candidate mechanism underlying PONV. RESULTS: A median of six emetic episodes occurred in both the Sham and Surgery groups. Whole-transcriptome analysis indicated the inhibition of the GABAB receptor-mediated signaling pathway in the PONV model. Baclofen (GABAB receptor agonist) administration eliminated emetic behaviors in the shrew PONV model. CONCLUSIONS: Our findings suggest that the GABAB receptor-mediated signaling pathway is involved in emesis and that baclofen may be a novel therapeutic or prophylactic agent for PONV.


Assuntos
Antieméticos , Animais , Antieméticos/uso terapêutico , Baclofeno/farmacologia , Baclofeno/uso terapêutico , Eméticos , Feminino , Perfilação da Expressão Gênica , Náusea e Vômito Pós-Operatórios/tratamento farmacológico , Musaranhos/fisiologia , Núcleo Solitário , Vômito/tratamento farmacológico , Vômito/prevenção & controle
2.
J Therm Biol ; 104: 103193, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-35180970

RESUMO

Ambient temperature has a substantial influence on the thermoregulation costs of small mammals due to their high surface-to-volume ratio. Shrews are among the smallest of mammals and have adopted different behavioral and physiological strategies to deal with cold temperatures. In this study, we assessed the use of an external heat source in the thermoregulatory strategy of two Crocidurinae species, Crocidura russula and C. suaveolens, and one Soricinae species, Sorex araneus. Crocidura russula inhabits western Europe and is better adapted to a Mediterranean climate; C. suaveolens inhabits central Europe; and S. araneus inhabits northern Europe and is better adapted to a Palearctic climate. We predicted that C. russula (most southern species) would spend larger amounts of time using an external heat source because it is the most cold-sensitive species, while S. araneus (most northern species) would spend less time using an external heat source or not respond to it. Shrews were experimentally tested in captivity inside a terrarium where they had access to a heat rock, which could be turned off (cold) or on (heated), depending on treatment. Our results confirmed our initial prediction: C. russula was the species that spent significantly more time on the heated rock, followed by C. suaveolens. Only a quarter of S. araneus individuals spent large amounts of time on the heat rock, which suggests this thermoregulation strategy is not generally adopted by this species, but may be rather associated with some individual personalities. We also analyzed the influence of the heat rock on rewarming from heterothermy, but heterothermy was not different between rock treatments. Overall, our results show that shrew species use external heat sources for thermoregulation according to their sensitivity to cold.


Assuntos
Regulação da Temperatura Corporal , Musaranhos/fisiologia , Adaptação Fisiológica , Animais , Temperatura Baixa , Europa (Continente) , Feminino , Temperatura Alta , Masculino , Musaranhos/classificação
3.
J Am Assoc Lab Anim Sci ; 61(1): 52-60, 2022 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-34772472

RESUMO

The Etruscan shrew (Suncus etruscus) is one of the smallest mammals on earth and is used in many fields of research, including physiology, behavioral science and neuroscience. However, establishing and maintaining a breeding colony of this species in the laboratory can be challenging, as it requires specific husbandry conditions that greatly differ from those of more common laboratory species such as mice or rats. Over the past 15 y, we have successfully established a long-term thriving colony of 150 to 200 animals originating from 36 founders. The colony shows longer life expectancy and larger litter sizes than wild conspecifics. Breeding occurs year-round, independent of seasons, and a breeding pair can regularly produce 2 to 6 offspring with an average life expectancy of more than 3 y. The shrews are housed in glass or plastic enclosures on a specific soil-sand-mixture bedding and are provided with hideouts and nesting material consisting of moss, wood, or bark. Due to their high basal metabolic rate, the shrews require food intake greater than their body weight per day, can hunt arthropods as large as themselves, and cannot survive more than a few hours without food. Live feed such as crickets or mealworms is crucial and must be provided daily or, at the very least, every 2 d. Although our husbandry practices have constantly been adapted and refined, shrew husbandry remains challenging, and great care is necessary to meet the specific needs of this species. Here, we describe the establishment of a long-term stable colony of Etruscan shrews in a research animal facility and the specific husbandry requirements for animal wellbeing.


Assuntos
Melhoramento Vegetal , Musaranhos , Animais , Feminino , Tamanho da Ninhada de Vivíparos , Camundongos , Gravidez , Ratos , Musaranhos/fisiologia
4.
Int J Mol Sci ; 22(14)2021 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-34299282

RESUMO

Shrews are small animals found in many different habitats. Like other mammals, adult neurogenesis occurs in the subventricular zone of the lateral ventricle (SVZ) and the dentate gyrus (DG) of the hippocampal formation. We asked whether the number of new generated cells in shrews depends on their brain size. We examined Crocidura russula and Neomys fodiens, weighing 10-22 g, and Crocidura olivieri and Suncus murinus that weigh three times more. We found that the density of proliferated cells in the SVZ was approximately at the same level in all species. These cells migrated from the SVZ through the rostral migratory stream to the olfactory bulb (OB). In this pathway, a low level of neurogenesis occurred in C. olivieri compared to three other species of shrews. In the DG, the rate of adult neurogenesis was regulated differently. Specifically, the lowest density of newly generated neurons was observed in C. russula, which had a substantial number of new neurons in the OB compared with C. olivieri. We suggest that the number of newly generated neurons in an adult shrew's brain is independent of the brain size, and molecular mechanisms of neurogenesis appeared to be different in two neurogenic structures.


Assuntos
Encéfalo/anatomia & histologia , Encéfalo/fisiologia , Neurônios/fisiologia , Musaranhos/anatomia & histologia , Musaranhos/fisiologia , Animais , Peso Corporal , Movimento Celular/fisiologia , Proliferação de Células , Hipocampo/anatomia & histologia , Hipocampo/fisiologia , Ventrículos Laterais/anatomia & histologia , Ventrículos Laterais/fisiologia , Neurogênese , Bulbo Olfatório/anatomia & histologia , Bulbo Olfatório/fisiologia , Tamanho do Órgão
5.
Sci Rep ; 11(1): 12031, 2021 06 08.
Artigo em Inglês | MEDLINE | ID: mdl-34103594

RESUMO

Compared to Northern Carpathians, the small mammal fauna of Southern Carpathian forests is poorly known, with no data on habitat use; our study seeks to fill this gap. To this end, we conducted a survey in the Southern Carpathians for five years, assessing habitat use by small mammals in forests along an elevational gradient. Trapping was done using live traps set in transects at elevations between 820 and 2040 m. For each transect we evaluated variables related to vegetation structure, habitat complexity, and geographical location. We considered abundance, species composition and species richness as response variables. The rodents Apodemus flavicollis and Myodes glareolus and the shrew Sorex araneus were common and dominant. Their abundance were positively correlated with tree cover, the best explanatory variable. Responses to other variables were mixed. The strong divergence in the relative habitat use by the three most abundant species may act as a mechanism that enables their coexistence as dominant species, exploiting the same wide range of habitat resources. Overall, habitat use in our study area was similar to that reported from Northern Carpathians, but we found also important differences probably caused by the differences in latitude and forest management practices.


Assuntos
Arvicolinae/fisiologia , Biodiversidade , Florestas , Roedores/fisiologia , Musaranhos/fisiologia , Animais , Romênia
6.
Eur J Pharmacol ; 900: 174065, 2021 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-33775646

RESUMO

Akt (protein kinase B) signaling is frequently activated in diverse cancers. Akt inhibitors such as perifosine and MK-2206 have been evaluated as potential cancer chemotherapeutics. Although both drugs are generally well tolerated, among their most common side-effects vomiting is a major concern. Here we investigated whether these Akt inhibitors evoke emesis in the least shrew model of vomiting. Indeed, both perifosine and MK-2206 induced vomiting with maximal efficacies of 90% at 50 mg/kg (i.p.) and 100% at 10 mg/kg (i.p.), respectively. MK-2206 (10 mg/kg, i.p.) increased c-Fos immunoreactivity both centrally in the shrew brainstem dorsal vagal complex (DVC) emetic nuclei, and peripherally in the jejunum. MK-2206 also evoked phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) in both the DVC emetic nuclei and the enteric nervous system in the jejunum. The ERK1/2 inhibitor U0126 suppressed MK-2206-induced emesis dose-dependently. We then evaluated the suppressive efficacy of diverse antiemetics against MK-2206-evoked vomiting including antagonists/inhibitors of the: L-type Ca2+ channel (nifedipine at 2.5 mg/kg, subcutaneously (s.c.)); glycogen synthase kinase 3 (GSK-3) (AR-A014418 at 10 mg/kg and SB216763 at 0.25 mg/kg, i.p.); 5-hydroxytryptamine 5-HT3 receptor (palonosetron at 0.5 mg/kg, s.c.); substance P neurokinin NK1 receptor (netupitant at 10 mg/kg, i.p.) and dopamine D2/3 receptor (sulpride at 8 mg/kg, s.c.). All tested antagonists/blockers attenuated emetic parameters to varying degrees. In sum, this is the first study to demonstrate how pharmacological inhibition of Akt evokes vomiting via both central and peripheral mechanisms, a process which involves multiple emetic receptors.


Assuntos
Antieméticos/farmacologia , Sistema Nervoso Central/efeitos dos fármacos , Compostos Heterocíclicos com 3 Anéis , Proteína Oncogênica v-akt/antagonistas & inibidores , Sistema Nervoso Periférico/efeitos dos fármacos , Musaranhos/fisiologia , Vômito/induzido quimicamente , Vômito/fisiopatologia , Animais , Antieméticos/uso terapêutico , Tronco Encefálico/efeitos dos fármacos , Relação Dose-Resposta a Droga , Eméticos/farmacologia , Sistema Nervoso Entérico/efeitos dos fármacos , Compostos Heterocíclicos com 3 Anéis/antagonistas & inibidores , Jejuno/efeitos dos fármacos , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Fosforilação , Proteínas Proto-Oncogênicas c-fos/metabolismo , Vômito/tratamento farmacológico
7.
Hist Philos Life Sci ; 43(1): 31, 2021 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-33629158

RESUMO

More than a century ago, Edward W. Nelson and Edward A. Goldman spent 14 years (1892-1906) traveling across much of Mexico in one of the most critical biological expeditions ever undertaken by two naturalists. This long-term survey was a cornerstone in Mexican mammalogy development; however, their specific role in discovering taxa that were practically unknown before the expedition is not yet necessarily recognized. In a time when the historical aspect of knowledge on mammals is being ignored for the new generations of mammalogists, a detailed analysis of the legacy of the survey is essential. Here I focus on shrews (Eulipotyphla, Soricidae) to analyze how the fieldwork and the specimens they collected have contributed to the current knowledge of shrews in the country. Nelson and Goldman collected 474 specimens of shrews, representing 31 of the 40 species that have currently been recognized. This collection has been key to building taxonomic, evolutionary, and biogeographic knowledge of shrews in the country. The success of the expedition was primarily due to the epistemic role of novel methods and approaches in natural history research at the time. The collection also offers the opportunity to document the loss of species and ecological interactions as indirect consequences of human activities, especially in montane regions. I argue that the value of this expedition can still increase with the use of modern biodiversity study tools and the digitization and access of ancient material such as photographs, field notes, and correspondence.


Assuntos
Distribuição Animal , Biodiversidade , Traços de História de Vida , História Natural/história , Musaranhos , Animais , História do Século XIX , História do Século XX , México , Filogenia , Musaranhos/classificação , Musaranhos/fisiologia
8.
Proc Natl Acad Sci U S A ; 117(50): 32136-32144, 2020 12 15.
Artigo em Inglês | MEDLINE | ID: mdl-33257560

RESUMO

Seasonal cycles govern life on earth, from setting the time for the mating season to influencing migrations and governing physiological conditions like hibernation. The effect of such changing conditions on behavior is well-appreciated, but their impact on the brain remains virtually unknown. We investigate long-term seasonal changes in the mammalian brain, known as Dehnel's effect, where animals exhibit plasticity in body and brain sizes to counter metabolic demands in winter. We find large seasonal variation in cellular architecture and neuronal activity in the smallest terrestrial mammal, the Etruscan shrew, Suncus etruscus Their brain, and specifically their neocortex, shrinks in winter. Shrews are tactile hunters, and information from whiskers first reaches the somatosensory cortex layer 4, which exhibits a reduced width (-28%) in winter. Layer 4 width (+29%) and neuron number (+42%) increase the following summer. Activity patterns in the somatosensory cortex show a prominent reduction of touch-suppressed neurons in layer 4 (-55%), the most metabolically active layer. Loss of inhibitory gating occurs with a reduction in parvalbumin-positive interneurons, one of the most active neuronal subtypes and the main regulators of inhibition in layer 4. Thus, a reduction in neurons in layer 4 and particularly parvalbumin-positive interneurons may incur direct metabolic benefits. However, changes in cortical balance can also affect the threshold for detecting sensory stimuli and impact prey choice, as observed in wild shrews. Thus, seasonal neural adaptation can offer synergistic metabolic and behavioral benefits to the organism and offer insights on how neural systems show adaptive plasticity in response to ecological demands.


Assuntos
Hibernação/fisiologia , Plasticidade Neuronal/fisiologia , Musaranhos/fisiologia , Córtex Somatossensorial/fisiologia , Animais , Metabolismo Energético/fisiologia , Feminino , Imageamento por Ressonância Magnética , Masculino , Neurônios/fisiologia , Tamanho do Órgão/fisiologia , Estações do Ano , Córtex Somatossensorial/citologia , Córtex Somatossensorial/diagnóstico por imagem , Percepção do Tato/fisiologia , Vibrissas/fisiologia
9.
PLoS One ; 15(9): e0236155, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32915780

RESUMO

Large brains in prey may select for adoption of anti-predator behavior that facilitates escape. Prey species with relatively large brains have been shown to be less likely to fall prey to predators. This results in the prediction that individuals that have been captured by predators on average should have smaller brains than sympatric conspecifics. We exploited the fact that Eurasian pygmy owls Glaucidium passerinum hoard small mammals and birds in cavities and nest-boxes for over-winter survival, allowing for comparison of the phenotype of prey with that of live conspecifics. In Northern Europe, main prey of pygmy owls are voles of the genera Myodes and Microtus, while forest birds and shrews are the most important alternative prey. Large fluctuations (amplitude 100-200-fold) in vole populations induce rapid numerical responses of pygmy owls to main prey populations, which in turn results in varying predation pressure on small birds. We found, weighed and measured 153 birds in food-stores of pygmy owls and mist-netted, weighed and measured 333 live birds of 12 species in central-western Finland during two autumns with low (2017) and high (2018) pygmy owl predation risk. In two autumns, individuals with large brains were captured later compared to individuals with small brains, consistent with the hypothesis that such individuals survived for longer. Avian prey of pygmy owls had smaller heads than live birds in autumn 2018 when predation risk by pygmy owls was high. This difference in head size was not significant in 2017 when predation risk by pygmy owls was reduced. Finally, avian survivors were in better body condition than avian prey individuals. These findings are consistent with the hypothesis that pygmy owls differentially prey on birds in poor condition with small brains. These findings are consistent with the hypothesis that predation risk imposed by pygmy owls on small birds in boreal forests varies depending on the abundance of the main prey (voles).


Assuntos
Comportamento Predatório , Estrigiformes , Animais , Arvicolinae/fisiologia , Encéfalo/fisiologia , Feminino , Masculino , Tamanho do Órgão , Estações do Ano , Musaranhos/fisiologia , Estrigiformes/fisiologia , Taiga
10.
Dokl Biol Sci ; 492(1): 89-92, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32632834

RESUMO

Thirty-year studies of populations of eight shrew species in the Middle Yenisei taiga have shown that at the late 20th century the population dynamics had a pronounced cyclic character, but in the 21st century cyclic dynamics changed with fluctuating one. The analysis of the dependence of the animal body weight on the population density have revealed that under cyclic dynamics at the peaks of the population, the animal's body weight is significantly higher than that at population decline, i.e., the corollary from the Chitty hypothesis (the Chitty effect) is observed. In populations with fluctuating dynamics such regularity has not been observed.


Assuntos
Peso Corporal/fisiologia , Densidade Demográfica , Dinâmica Populacional , Musaranhos/fisiologia , Animais , Taiga
11.
J Mol Neurosci ; 70(3): 308-319, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31845102

RESUMO

Tree shrews, possessing higher developed motor function than rats, were more suitable to study neurological behavior after spinal cord injury (SCI). Here, we established a feasible behavioral assessment method to detect the degree of ethology recovery in tree shrew subjected to spinal cord transection (SCT). Tree shrews were divided into normal group, sham group, and SCT group. The tree shrew in sham group was subjected to laminectomy without SCI, while the tree shrews in the SCT group were subjected to a complete SCT in thoracic 10 (T10). A novel neurobehavior assessment scale was established, in which, the behavior index including slow advancement, fast advancement, standing, shaking head, voluntary jump, lateral movement, and tail status, was determined, respectively. Meanwhile, magnetic resonance imaging (MRI) was applied to observe the structure of the spinal cord, and diffusion tensor imaging (DTI)-based white matter mapping was used to show the fibers of the spinal cord. As a result, a marked decrease in locomotor function and consciousness was seen in tree shrews with SCT, and the detection of MRI showed the collapsing of nerve fibers after SCT is completely cut and there is corresponding to the behavior change. Together, the present study provided a novel and feasible method that can be used to assess the neurobehavior in SCT model from tree shrews, which may be useful to the SCI translational study in future preclinic trial.


Assuntos
Modelos Animais de Doenças , Musaranhos/fisiologia , Traumatismos da Medula Espinal/fisiopatologia , Animais , Movimento , Medula Espinal/diagnóstico por imagem , Medula Espinal/patologia , Medula Espinal/cirurgia , Traumatismos da Medula Espinal/etiologia
12.
Proc Natl Acad Sci U S A ; 116(51): 25745-25755, 2019 12 17.
Artigo em Inglês | MEDLINE | ID: mdl-31772017

RESUMO

Venom systems are key adaptations that have evolved throughout the tree of life and typically facilitate predation or defense. Despite venoms being model systems for studying a variety of evolutionary and physiological processes, many taxonomic groups remain understudied, including venomous mammals. Within the order Eulipotyphla, multiple shrew species and solenodons have oral venom systems. Despite morphological variation of their delivery systems, it remains unclear whether venom represents the ancestral state in this group or is the result of multiple independent origins. We investigated the origin and evolution of venom in eulipotyphlans by characterizing the venom system of the endangered Hispaniolan solenodon (Solenodon paradoxus). We constructed a genome to underpin proteomic identifications of solenodon venom toxins, before undertaking evolutionary analyses of those constituents, and functional assessments of the secreted venom. Our findings show that solenodon venom consists of multiple paralogous kallikrein 1 (KLK1) serine proteases, which cause hypotensive effects in vivo, and seem likely to have evolved to facilitate vertebrate prey capture. Comparative analyses provide convincing evidence that the oral venom systems of solenodons and shrews have evolved convergently, with the 4 independent origins of venom in eulipotyphlans outnumbering all other venom origins in mammals. We find that KLK1s have been independently coopted into the venom of shrews and solenodons following their divergence during the late Cretaceous, suggesting that evolutionary constraints may be acting on these genes. Consequently, our findings represent a striking example of convergent molecular evolution and demonstrate that distinct structural backgrounds can yield equivalent functions.


Assuntos
Eutérios , Evolução Molecular , Genoma/genética , Musaranhos , Peçonhas/genética , Animais , Eutérios/classificação , Eutérios/genética , Eutérios/fisiologia , Duplicação Gênica , Masculino , Filogenia , Proteômica , Musaranhos/classificação , Musaranhos/genética , Musaranhos/fisiologia , Calicreínas Teciduais/genética
13.
Sci Rep ; 9(1): 2489, 2019 02 21.
Artigo em Inglês | MEDLINE | ID: mdl-30792434

RESUMO

The growth of the vertebrate skull and brain is usually unidirectional and more or less stops when animals are adult. Red-toothed shrews break this rule. They seasonally shrink and regrow brain and skull size by 20% or more, presumably to save energy when conditions are harsh. The size change is anticipatory of environmental change and occurs in all individuals, but it is unknown whether its extent can be modulated by environmental conditions. We kept shrews under different conditions, monitored seasonal changes in skull size with series of X-rays, and compared them with free ranging animals. We found extensive differences in the pattern of skull size change between experimental groups. Skull size of shrews kept at constant temperature showed a steady decline, while the skull size changes of free ranging shrews and captive individuals exposed to natural temperature regimes were identical. In contrast, body mass never reached the spring values of free ranging shrews in either captive regime. The extent of this adaptive seasonal pattern can thus be flexibly adapted to current environmental conditions. Combining reversible size changes with such strong phenotypic plasticity may allow these small, non-hibernating predators with high metabolic rates to continue being successful in today's changing environments.


Assuntos
Encéfalo/anatomia & histologia , Musaranhos/fisiologia , Crânio/anatomia & histologia , Adaptação Fisiológica , Animais , Encéfalo/fisiologia , Estações do Ano , Musaranhos/anatomia & histologia , Crânio/fisiologia , Raios X
14.
Anat Rec (Hoboken) ; 302(6): 1010-1023, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30376699

RESUMO

Moles are a strictly fossorial Soricomorpha species and possess a suite of specialized adaptations to subterranean life. However, the contractile function of skeletal muscles in moles remains unclear. We compared muscle fiber-type distribution in two mole species (the large Japanese mole and lesser Japanese mole) with that in four other Soricomorpha species that are semi-fossorial, terrestrial, or semi-aquatic (the Japanese shrew-mole, house shrew, Japanese white-toothed shrew, and Japanese water shrew). For a single species, the fiber-type distribution in up to 38 muscles was assessed using immunohistochemical staining and/or gel electrophoresis. We found that slow and fatigue-resistant Type I fibers were absent in almost all muscles of all species studied. Although, the two methods of determining the fiber type did not give identical results, they both revealed that fast Type IIb fibers were absent in mole muscles. The fiber-type distribution was similar among different anatomical regions in the moles. This study demonstrated that the skeletal muscles of moles have a homogenous fiber-type distribution compared with that in Soricomorpha species that are not strictly fossorial. Mole muscles are composed of Type IIa fibers alone or a combination of Type IIa and relatively fast Type IIx fibers. The homogenous fiber-type distribution in mole muscles may be an adaptation to structurally simple subterranean environments, where there is no need to support body weight with the limbs, or to move at high speeds to pursue prey or to escape from predators. Anat Rec, 302:1010-1023, 2019. © 2018 Wiley Periodicals, Inc.


Assuntos
Adaptação Fisiológica , Toupeiras/fisiologia , Contração Muscular/fisiologia , Fibras Musculares de Contração Rápida/fisiologia , Fibras Musculares de Contração Lenta/fisiologia , Animais , Toupeiras/anatomia & histologia , Musaranhos/anatomia & histologia , Musaranhos/fisiologia
15.
J Comp Neurol ; 526(15): 2388-2405, 2018 10 15.
Artigo em Inglês | MEDLINE | ID: mdl-30004584

RESUMO

Of the 18 sub-Saharan elephant-shrew species, only eastern rock elephant-shrews reproduce seasonally throughout their distribution, a process seemingly independent of photoperiod. The present study characterizes gonadal status and location/intensity of gonadotrophin-releasing hormone-1 (GnRH-1) and kisspeptin immunoreactivities in this polyovulating species in the breeding and nonbreeding seasons. GnRH-1-immunoreactive (ir) cell bodies are predominantly in the medial septum, diagonal band, and medial preoptic area; processes are generally sparse except in the external median eminence. Kisspeptin-ir cell bodies are detected only within the arcuate nucleus; the density of processes is generally low, except in the septohypothalamic nucleus, ventromedial bed nucleus of the stria terminalis, arcuate nucleus, and internal and external median eminence. Kisspeptin-ir processes are negligible at locations containing GnRH-1-ir cell bodies. The external median eminence is the only site with conspicuously overlapping distributions of the respective immunoreactivities and, accordingly, a putative site for kisspeptin's regulation of GnRH-1 release in this species. In the nonbreeding season in males, there is an increase in the rostral population of GnRH-1-ir cell bodies and density of GnRH-1-ir processes in the median eminence. In both sexes, the breeding season is associated with increased kisspeptin-ir process density in the rostral periventricular area of the third ventricle and arcuate nucleus; at the latter site, this is positively correlated with gonadal mass. Cross-species comparisons lead us to hypothesize differential mechanisms within these peptidergic systems: that increased GnRH-1 immunoreactivity during the nonbreeding season reflects increased accumulation with reduced release; that increased kisspeptin immunoreactivity during the breeding season reflects increased synthesis with increased release.


Assuntos
Hormônio Liberador de Gonadotropina/fisiologia , Kisspeptinas/fisiologia , Estações do Ano , Comportamento Sexual Animal/fisiologia , Musaranhos/fisiologia , Animais , Núcleo Arqueado do Hipotálamo/citologia , Núcleo Arqueado do Hipotálamo/fisiologia , Mapeamento Encefálico , Feminino , Imuno-Histoquímica , Masculino , Núcleos da Linha Média do Tálamo/citologia , Núcleos da Linha Média do Tálamo/fisiologia , Neurônios/fisiologia , Reprodução/fisiologia
16.
Proc Biol Sci ; 285(1880)2018 06 13.
Artigo em Inglês | MEDLINE | ID: mdl-29899069

RESUMO

All small mammals have prominent facial whiskers that they employ as tactile sensors to guide navigation and foraging in complex habitats. Nocturnal, arboreal mammals tend to have the longest and most densely packed whiskers, and semi-aquatic mammals have the most sensitive. Here we present evidence to indicate that many small mammals use their whiskers to tactually guide safe foot positioning. Specifically, in 11, small, non-flying mammal species, we demonstrate that forepaw placement always falls within the ground contact zone of the whisker field and that forepaw width is always smaller than whisker span. We also demonstrate commonalities of whisker scanning movements (whisking) and elements of active control, associated with increasing contact with objects of interest, across multiple small mammal species that have previously only been shown in common laboratory animals. Overall, we propose that guiding locomotion, alongside environment exploration, is a common function of whisker touch sensing in small, quadrupedal mammals.


Assuntos
Locomoção/fisiologia , Roedores/fisiologia , Musaranhos/fisiologia , Percepção do Tato , Vibrissas/fisiologia , Animais
17.
J Comp Physiol B ; 188(4): 707-716, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29623412

RESUMO

Much of our knowledge of the thermoregulation of endotherms has been obtained from species inhabiting cold and temperate climates, our knowledge of the thermoregulatory physiology of tropical endotherms is scarce. We studied the thermoregulatory physiology of a small, tropical mammal, the large treeshrew (Tupaia tana, Order Scandentia) by recording the body temperatures of free-ranging individuals, and by measuring the resting metabolic rates of wild individuals held temporarily in captivity. The amplitude of daily body temperature (~ 4 °C) was higher in treeshrews than in many homeothermic eutherian mammals; a consequence of high active-phase body temperatures (~ 40 °C), and relatively low rest-phase body temperatures (~ 36 °C). We hypothesized that high body temperatures enable T. tana to maintain a suitable gradient between ambient and body temperature to allow for passive heat dissipation, important in high-humidity environments where opportunities for evaporative cooling are rare. Whether this thermoregulatory phenotype is unique to Scandentians, or whether other warm-climate diurnal small mammals share similar thermoregulatory characteristics, is currently unknown.


Assuntos
Regulação da Temperatura Corporal , Musaranhos/fisiologia , Animais , Metabolismo Basal , Ritmo Circadiano , Feminino , Temperatura Alta , Umidade , Malásia , Masculino
18.
PLoS One ; 13(1): e0189471, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29298313

RESUMO

For decades, ecologists have debated the importance of biotic interactions (e.g., competition) and abiotic factors in regulating populations. Competition can influence patterns of distribution, abundance, and resource use in many systems but remains difficult to measure. We quantified competition between two sympatric small mammals, Keen's mice (Peromyscus keeni) and dusky shrews (Sorex monticolus), in four habitat types on Prince of Wales Island in Southeast Alaska. We related shrew density to that of mice using standardized regression models while accounting for habitat variables in each year from 2010-2012, during which mice populations peaked (2011) and then crashed (2012). Additionally, we measured dietary overlap and segregation using stable isotope analysis and kernel utilization densities and estimated the change in whole community energy consumption among years. We observed an increase in densities of dusky shrews after mice populations crashed in 2012 as expected under competitive release. In addition, competition coefficients revealed that the influence of Keen's mice was dependent on their density. Also in 2012, shrew diets shifted, indicating that they were able to exploit resources previously used by mice. Nonetheless, increases in shrew numbers only partially compensated for the community energy consumption because, as insectivores, they are unlikely to utilize all food types consumed by their competitors. In pre-commercially thinned stands, which exhibit higher diversity of resources compared to other habitat types, shrew populations were less affected by changes in mice densities. These spatially and temporally variable interactions between unlikely competitors, observed in a relatively simple, high-latitude island ecosystem, highlight the difficulty in assessing the role of biotic factors in structuring communities.


Assuntos
Ecossistema , Peromyscus/fisiologia , Musaranhos/fisiologia , Animais , Camundongos
19.
Acta Physiol (Oxf) ; 222(2)2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-28786555

RESUMO

AIM: Stomach contractions show two types of specific patterns in many species, that is migrating motor contraction (MMC) and postprandial contractions (PPCs), in the fasting and fed states respectively. We found gastric PPCs terminated with migrating strong contractions in humans, dogs and suncus. In this study, we reveal the detailed characteristics and physiological implications of these strong contractions of PPC. METHODS: Human, suncus and canine gastric contractions were recorded with a motility-monitoring ingestible capsule and a strain-gauge force transducer. The response of motilin and ghrelin and its receptor antagonist on the contractions were studied by using free-moving suncus. RESULTS: Strong gastric contractions were observed at the end of a PPC in human, dog and suncus models, and we tentatively designated this contraction to be a postprandial giant contraction (PPGC). In the suncus, the PPGC showed the same property as those of a phase III contraction of MMC (PIII-MMC) in the duration, motility index and response to motilin or ghrelin antagonist administration. Ghrelin antagonist administration in the latter half of the PPC (LH-PPC) attenuated gastric contraction prolonged the duration of occurrence of PPGC, as found in PII-MMC. CONCLUSION: It is thought that the first half of the PPC changed to PII-MMC and then terminated with PIII-MMC, suggesting that PPC consists of a digestive phase (the first half of the PPC) and a discharge phase (LH-PPC) and that LH-PPC is coincident with MMC. In this study, we propose a new approach for the understanding of postprandial contractions.


Assuntos
Motilidade Gastrointestinal/fisiologia , Grelina/metabolismo , Motilina/metabolismo , Período Pós-Prandial/fisiologia , Musaranhos/fisiologia , Animais , Cães , Humanos , Contração Muscular/fisiologia , Estômago/fisiologia
20.
J Exp Biol ; 221(Pt 2)2018 01 22.
Artigo em Inglês | MEDLINE | ID: mdl-29170257

RESUMO

In a rare phenomenon, shrews and a few other species cope with seasonal environments by reducing and regrowing brain size, potentially at the cost of changes in cognitive abilities. Here, we confirm an extensive seasonal shrinkage (21.4%) and regrowth (17.0%) of brain mass in winter and spring, respectively, in the common shrew (Sorex araneus L.) in Southern Germany. In a spatial learning task experiment, individuals with reduced winter brain size covered larger distances to find food, compared with the relatively large-brained summer juveniles and regrown spring adults. By reducing their brain mass, these shrews may reduce their energetic demands, but at the cost of cognitive performance, implying a complex trade-off for coping with seasonally fluctuating resources. These results are relevant for our understanding of evolution and the dynamics of mammalian nervous systems in response to environmental changes.


Assuntos
Encéfalo/fisiologia , Cognição , Musaranhos/psicologia , Crânio/anatomia & histologia , Fatores Etários , Animais , Feminino , Alemanha , Masculino , Estações do Ano , Musaranhos/anatomia & histologia , Musaranhos/fisiologia
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