13 research outputs found
THE TIMEKEEPING SYSTEM: A KEY ORGANIZATIONAL ELEMENT
No full textLife has evolved in a cyclic environment, and consequently, during evolution the time dimension was incorporated in the inner organization of every single biological structure. This incorporation is evident in the biological rhythms detected in the whole phylogenetic range, from unicellular organisms to humans, and at all organizational level within an organism, from molecular to behavioral variables. ?Doing the right thing at the right time? enhances reproduction, health, survival and longevity. Biological clocks generate such rhythms, afferent pathways synchronize them with the cyclic environment, and efferent pathways convey this time information to the organism as a whole. In mammals, the main biological clocks are localized in the hypothalamus, the suprachiasmatic nuclei, which receive direct specialized inputs from the retinas allowing synchronization to the external night-day maintaining the organism in tune with its environment. A particular and refined set of photoreceptors allows this light perception. A network of peripheral clocks in other neural, as well as non-neural tissues throughout the organism, receives this time information assuring precise temporal relationship between every system within the organism, the so-called internal temporal order. When considering any biological system, time of sampling should always be tracked, and the use of basic and simple chronobiological methods considered so avoiding misinterpretations.Fil: Valentinuzzi, Verónica Sandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de Catamarca. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Secretaría de Industria y Minería. Servicio Geológico Minero Argentino. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Provincia de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; ArgentinaFil: Oda, Gisele Akemi. Universidade de Sao Paulo. Departamento de Fisiología. Instituto de Biociencias; Brasi
Variação circadiana na habituação da resposta exploratoria a estimulos sonoros em pombos (Columba livia), submetidos a condições de claro-escuro e de claro constante
No full textOrientador : Elenice A. de Moraes FerrariDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de BiologiaResumo: Este trabalho analisou a habituação a sons no contexto da organização temporal do comportamento. O processo de habituação da resposta exploratória ao som foi analisado em três experimentos. O objetivo principal desses experimentos foi a análise dessa resposta em função do horário das sessões de habituação, i.e., matutinas ou vespertinas Os experimentos diferiram quanto aos ciclos de iluminação aos quais pombos adultos foram expostos: ciclo claro-escuro de 12:12h, no Experimento 1; claro continuo, no Experimento 2; e dois dias de claro continuo, interposto a um ciclo claro-escuro de 12:12h, no Experimento 3. Os três experimentos foram igualados quanto aos horários de teste. Os testes matutinos foram realizados às 7:30h, uma hora após o acender da luz, e às 19:30h. uma hora após o desligar da luz. Os pombos foram submetidos a apresentações de um som de 1000-Hz, 83-dB, 1s (estimulo A), a cada 30 s, até habituação das respostas exploratórias ou até um máximo de 100 estimulos, quando o critério de aprendizagem não era observado O critério de aprendizagem estabelecia a ocorrência de 10 estimulos sem o registro de respostas exploratórias. Uma segunda sessão de habituação, com a apresentação de um som de 500-Hz, 85-dB, 1s (estimulo B>, foi realizada 24h depois. O reteste, com a mesma sequência de procedimentos e inversão do horário de teste. foi realizado 18 dias ap6s a segunda sessão. Os resultados do Experimento 1 mostraram que nos testes noturnos, em comparação com os matutinos. houve um maior número de estimulações até habituação (p(O.05), tanto para o estímulo A quanto para o estimulo B. No Experimento 2 foram observadas diferenças na velocidade da habituação nos testes matutinos e noturnos, apenas nas sessees com o estimulo A (p(0,05). Os pombos expostos a dois dias de iluminação continua antes dos testes do Experimento 3 também mostraram uma di~erença noite-dia embora não significante. O conjunto de dados desses exxperimentos sugerem uma organização temporal dos processos de habituação e colocam questões relativas ao significado biológico da estimulação sonora em condições de claro e de escuro. As diferenças observadas entre os três experimentos também sugerem uma função para a melatonina na regulação desses processos. Os pombos mantidos sob iluminação constante e aqueles que ~oram expostos a dois dias de luz continua antes do teste. provavelmente caracterizados por baixos niveis de melatonina plasmática. mostraram menor velocidade de habituação em comparação com os pombos mantidos em ciclo claroescuro. Os baixos níveis de melatonina poderiam atuar no sentido de uma facilitação da habituação. Também foi argumentado um possivel efeito de estresse devido à exposição a dois dias de luz continua. Nesta condição provavelmente não haveria tempo suficiente para adaptações à nova situação de iluminação. A caracterização precisa dessas diferenças noite-dia na habituação ao som como expressão de um ritmo circadiano necessita ainda de outros estudosAbstract: The present work investigated habituation learning to acoustic stimulation in the context of temporal organization of behavior. The process of habituation of the exploratory responses to sound was analvsed in three experiments. The main purpose of these experiments was the analysis of these responses as function of the time of habituation sessions, i.e., mornins or nisht tests. The experiments differed in relation to the light cycles to which adult pigeons were exposed : 12:12h light-dark cycle in Experiment 1; continuous ilumination in Experiment 2 and twodays of continuous ilumination interposedto a 12:12 light-dark cycle, in Experiment3. Time for testins was matched for the three experimentswith morning tests at 7:30 a.m., one hour after light onset. and night tests at 7:30 p.m., one hour after turn out of light. Piseons were exposed to 1000-Hz.83-dB. ls sound (stimulus A) at 30 seconds intervals until habituation of the exploratory and startle response or until a maximum of 100 stimulus when the learning criterion was not observed. The learnins criterionwas 10 trials without the occurrence of these responses. Twenty-fourhours after habituation to stimulus A the birds were tested with a SOO-Hz, 8S-dB, 1s sound (stimulus B). Retesting. with the same sequence of proceduresbut reversal of the time of test was carried out 18 days after stimulus B habituation. Results from Experiment 1 showed an increased number of habituation trials in nocturnal (p(0,05) as compared to the morning tests for both stimulus A and B. The number of trials until habituation in the Experiment 2 showed differences between morning-night test onlv for stimulus A session. Pigeons exposed to two-davs Df continuous ilumination in Experiment 3 also showed a morning-night difference. although it was not significant. Taken together the data from these experiments suggest one temporal organization of the habituation learning processes and raises issues concerning the biological meaning of sound stimulation in light and dark environmental conditions. The differences observed between the three experiments also sugsest a role for the melatonin hormone in these processes. Pigeons maintained under continuous lisht or exposed to two-days of continuous il1umination prior to tests. which were probably characterized by decreased levels of melatonin, showed facilitation of habituationwhen compared to pigeons maintained under light-darkcycle. The lower levels of melatonin may act toward a facilitation of habituation. lt was also arsued a possible stress variable due to exposition to two-days ofcontinuous lisht. In this condition the animaIs probablv did not have enough time for adaptation to the new situation of constant light. Further studies are necessary for a precise characterization of those morning-night differences in habituation to sound as expression of a circadian rhvthmiticyMestradoFisiologiaMestre em Ciências Biológica
Modelação temporal de processos de aprendizagem : Implicações praticas e teoricas
No full textOrientador: Elenice A. de Moraes Ferrari, Fred W. TurekTese (doutorado) - Universidade Estadual de Campinas, Instituto de BiologiaResumo: Estudos da variação temporal de processos de aprendizagem e memória são relativamente escassos e inconsistentes, fundamentalmente, devido à falta de uma padronização dos métodos utilizados e especificação dos tipos de controles necessários, que permitam isolar componentes temporais endógenos da aprendizagem propriamente dita. Assim, no presente trabalho discutimos as dificuldades deste tipo de estudo e sugerimos estratégias que poderiam ajudar a controlar alguns dos fatores mascaradores. Foram realizados três estudos tentando aplicar algumas destas estratégias. No primeiro, analisamos o efeito da hora do dia na habituação a um contexto novo em camundongos, quantificando o comportamento ambulatório por meio de observação direta. Em condições de claroescuro um ritmo diurno foi detectado, porém nenhum efeito temporal foi observado em animais submetidos a um fotoperíodo esqueleto, situação em que se evita os efeitos mascaradores de um ciclo claro-escuro. Estes resultados demonstram que o ciclo de iluminação pode alterar significativamente a resposta a um contexto, reafirmando a necessidade de um controle preciso desta condição externa. Em estudos de ritmicidade de aprendizagem, devido à elevada freqüência de amostragem necessária e à necessidade de testes em horários pouco convenientes, a automatização da medida comportamental resulta indispensável. Assim, no segundo estudo foi validado um equipamento computadorizado para a medida do comportamento de imobilização em situações de condicionamento aversivo. As medidas comportamentais obtidas por este método automático mostraram uma elevada correlação com as medidas obtidas por observação direta. Conseqüentemente, este sistema foi utilizado no terceiro estudo onde se analisou o condicionamento aversivo durante as fases de atividade e de inatividade de camundongos submetidos a um fotoperíodo esqueleto. Uma diferença significativa entre os testes matutinos e os testes vespertinos foi detectada na expressão e extinção do condicionamento aversivo a um contexto, enquanto que nenhum efeito temporal foi observado no condicionamento aversivo a um som. O fato de que estes dois tipos de aprendizagens envolvem estruturas neurais diferentes sugere que o relógio biológico estaria tendo um efeito modulatório nas vias responsáveis pelo condicionamento a um contextoAbstract: Studies that analyze a temporal variation in learning and memory processes are relatively scattered and inconsistent, mainly due to the lack of systematic methods and specifications of the necessary controls that would allow the dissection of a temporal component in the learning process per se. Here we analyze the difficulties of this kind of study and suggest a few strategies that could help control some of the masking factors. Three studies were performed applying some of these strategies. In the first study we analyzed habituation to a novel environment in mice by quantifying ambulation in an open field through direct observation. Mice submitted to a light-dark cycle showed a
diurnal rhythm in learning however, no temporal effect was observed in animals submitted to a skeleton photoperiod (tw015-minute bright light pulses separated by 12 h of green dim light). Under these conditions the masking effects of a light-dark cyc1e are avoided. These results demonstrate that the response to a novel environment is strongly affected by the illumination cycle, thus reinforcing the need for precise control and specification of this condition. When analyzing learning at different times of the day automation of behavioral sCO1:ing becomes essential due to the need for high frequency in data collection and testing which occurs around the clock. Therefore, a second study was performed where a computer-assisted system for scoring freezing behavior in mice during fear conditioning situations was validated. The computer measures obtained during fear conditioning tests showed high correlations with hand-scored freezing. Consequently, this data collection system was used in a third study where fear conditioning was analyzed during the active and inactive phases of mice submitted to a skeleton photoperiod. A significant difference in the expression and extinction rate of context-dependent fear conditioning was observed between mice trained and tested in the morning versus the evening. In contrast, no diurnal rhythm was detected for tone-cued fear conditioning. The biological clock may have a modulating effect on the hippocampal-dependent pathway which underlies context fear conditioning and no effect on the hippocampal-independent pathway underlying tone-fear conditioningDoutoradoFisiologiaDoutor em Ciências Biológica
Seasonality in Reproduction and Reproductive Physiology of Caviomorphs
No full textGuenther A, Tachinardi P, Valentinuzzi VS, Sobrero R, Eberhardt AT, Trillmich F. Seasonality in Reproduction and Reproductive Physiology of Caviomorphs. Mammal Review. 2024.Animals experience seasonal fluctuations of photoperiod, food availability, temperature and precipitation. This affects their energy budget, often leading to seasonal reproduction. We review available literature and (re)-analyse existing datasets on seasonal reproduction of South American caviomorph rodents that are characterised by long pregnancies, typically precocial young and short lactation. While births occur nearly year-round in many species, reproductive investment and reproductive output (litter size, offspring mass and growth) vary seasonally, with largest litters often occurring in spring/summer. Male, as well as female, reproductive physiology varies across seasons in most of the investigated species. Experimental studies manipulating environmental aspects that usually change seasonally (photoperiod, nutrition, density) indicate a slightly different mechanistic basis driving seasonal reproduction in caviomorphs than in rodents of the Northern Hemisphere. Caviomorphs are a key component of various ecosystems and knowledge of their reproduction and how it might be influenced by climate change (i.e., mean and variance of temperature and rainfall) is urgently needed to predict future population trends
Social modulation of the daily activity rhythm in a solitary subterranean rodent, the tuco-tuco (Ctenomys sp)
No full textAbstractSouth American subterranean rodents are mainly described as solitary and mutual synchronization was never observed among individuals maintained together in laboratory. We report that a single birth event was capable of disrupting the robust nocturnal activity rhythm of singly housed tuco-tucos from north-west Argentina. “Around-the-clock activity” was displayed by 8 out of 13 animals whose cages were closer to the newborn pups. However, experimental exposure to a pup vocalization did not produce a similar effect on the rhythms of adult animals. Our results indicate an effect of social interaction in the expression of biological rhythms even in solitary animals
Circadian phase and intertrial interval interfere with social recognition memory
No full textA modified version of the social habituation/dis-habituation paradigm was employed to examine social recognition memory in Wistar rats during two opposing (active and inactive) circadian phases, using different intertrial intervals (30 and 60 min). Wheel-running activity was monitored continuously to identify circadian phase. To avoid possible masking effects of the light-dark cycle, the rats were synchronized to a skeleton photoperiod, which allowed testing during different circadian phases under identical lighting conditions. In each trial, an infantile intruder was introduced into an adult`s home-cage for a 5-minute interaction session, and social behaviors were registered. Rats were exposed to 5 trials per day for 4 consecutive days: oil days I and 2, each resident was exposed to the same intruder; on days 3 and 4, each resident was exposed to a different intruder in each trial. I he resident`s social investigatory behavior was more intense when different intruders were presented compared to repeated presentation of the same intruder, suggesting social recognition memory. This effect was stronger when the rats were tested during the inactive phase and when the intertrial interval was 60 min, These findings Suggest that social recognition memory, as evaluated in this modified habituation/dis-habituation paradigm, is influenced by the circadian rhythm phase during which testing is performed, and by intertrial interval. (C) 2008 Elsevier Inc. All rights reserved.CAPESCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)FAPESPFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)CNPqConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq
Circadian Pattern of Wheel-Running Activity of a South American Subterranean Rodent (Ctenomys cf knightii)
No full textCircadian rhythms are regarded as essentially ubiquitous features of animal behavior and are thought to confer important adaptive advantages. However, although circadian systems of rodents have been among the most extensively studied, most comparative biology is restricted to a few related species. In this study, the circadian organization of locomotor activity was studied in the subterranean, solitary north Argentinean rodent, Ctenomys knightii. The genus, Ctenomys, commonly known as Tuco-tucos, comprises more than 50 known species over a range that extends from 12S latitude into Patagonia, and includes at least one social species. The genus, therefore, is ideal for comparative and ecological studies of circadian rhythms. Ctenomys knightii is the first of these to be studied for its circadian behavior. All animals were wild caught but adapted quickly to laboratory conditions, with clear and precise activity-rest rhythms in a light-dark (LD) cycle and strongly nocturnal wheel running behavior. In constant dark (DD), the rhythm expression persisted with free-running periods always longer than 24h. Upon reinstatement of the LD cycle, rhythms resynchronized rapidly with large phase advances in 7/8 animals. In constant light (LL), six animals had free-running periods shorter than in DD, and 4/8 showed evidence of splitting. We conclude that under laboratory conditions, in wheel-running cages, this species shows a clear nocturnal rhythmic organization controlled by an endogenous circadian oscillator that is entrained to 24h LD cycles, predominantly by light-induced advances, and shows the same interindividual variable responses to constant light as reported in other non-subterranean species. These data are the first step toward understanding the chronobiology of the largest genus of subterranean rodents.Consejo Nacional de Investigaciones Científicas y Técnicas de Argentina (CONICET)National Research Council (CONICET)Natural Sciences and Engineering Research COuncil of CanadaNatural Sciences and Engineering Research Council of CanadaFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundacao de Amparo do Estado de Sao Paulo (FAPESP)Funfacao de Amparo a Pesquisa do Estado de Rio Grande do Norte (FAPERN)Funfacao de Amparo a Pesquisa do Estado de Rio Grande do Norte (FAPERN
Form and function of long-range vocalizations in a Neotropical fossorial rodent: the Anillaco Tuco-Tuco (Ctenomys sp.)
No full textThe underground environment poses particular communication challenges for subterranean rodents. Some loud and low-pitched acoustic signals that can travel long distances are appropriate for long-range underground communication and have been suggested to be territorial signals. Long-range vocalizations (LRVs) are important in long-distance communication in Ctenomys tuco-tucos. We characterized the LRV of the Anillaco Tuco-Tuco (Ctenomys sp.) using recordings from free-living individuals and described the behavioral context in which this vocalization was produced during laboratory staged encounters between individuals of both sexes. Long-range calls of Anillaco tuco-tucos are low-frequency, broad-band, loud, and long sounds composed by the repetition of two syllable types: series (formed by notes and soft-notes) and individual notes. All vocalizations were initiated with series, but not all had individual notes. Males were heavier than females and gave significantly lower-pitched vocalizations, but acoustic features were independent of body mass in males. The pronounced variation among individuals in the arrangement and number of syllables and the existence of three types of series (dyads, triads, and tetrads), created a diverse collection of syntactic patterns in vocalizations that would provide the opportunity to encode multiple types of information. The existence of complex syntactic patterns and the description of soft-notes represent new aspects of the vocal communication of Ctenomys. Long-distance vocalizations by Anillaco Tuco-Tucos appear to be territorial signals used mostly in male-male interactions. First, emission of LRVs resulted in de-escalation or space-keeping in male-male and male-female encounters in laboratory experiments. Second, these vocalizations were produced most frequently (in the field and in the lab) by males in our study population. Third, males produced LRVs with greater frequency during male-male encounters compared to male-female encounters. Finally, males appear to have larger home ranges that were more spatially segregated than those of females, suggesting that males may have greater need for long-distance signals that advertise their presence. Due to their apparent rarity, the function and acoustic features of LRV in female tuco-tucos remain inadequately known
Nocturnal to Diurnal Switches with Spontaneous Suppression of Wheel-Running Behavior in a Subterranean Rodent.
No full textSeveral rodent species that are diurnal in the field become nocturnal in the lab. It has been suggested that the use of running-wheels in the lab might contribute to this timing switch. This proposition is based on studies that indicate feed-back of vigorous wheel-running on the period and phase of circadian clocks that time daily activity rhythms. Tuco-tucos (Ctenomys aff. knighti) are subterranean rodents that are diurnal in the field but are robustly nocturnal in laboratory, with or without access to running wheels. We assessed their energy metabolism by continuously and simultaneously monitoring rates of oxygen consumption, body temperature, general motor and wheel running activity for several days in the presence and absence of wheels. Surprisingly, some individuals spontaneously suppressed running-wheel activity and switched to diurnality in the respirometry chamber, whereas the remaining animals continued to be nocturnal even after wheel removal. This is the first report of timing switches that occur with spontaneous wheel-running suppression and which are not replicated by removal of the wheel
Modeling natural photic entrainment in a subterranean rodent (Ctenomys aff. knighti), the Tuco-Tuco.
No full textSubterranean rodents spend most of the day inside underground tunnels, where there is little daily change in environmental variables. Our observations of tuco-tucos (Ctenomys aff. knighti) in a field enclosure indicated that these animals perceive the aboveground light-dark cycle by several bouts of light-exposure at irregular times during the light hours of the day. To assess whether such light-dark pattern acts as an entraining agent of the circadian clock, we first constructed in laboratory the Phase Response Curve for 1 h light-pulses (1000lux). Its shape is qualitatively similar to other curves reported in the literature and to our knowledge it is the first Phase Response Curve of a subterranean rodent. Computer simulations were performed with a non-linear limit-cycle oscillator subjected to a simple model of the light regimen experienced by tuco-tucos. Results showed that synchronization is achieved even by a simple regimen of a single daily light pulse scattered uniformly along the light hours of the day. Natural entrainment studies benefit from integrated laboratory, field and computational approaches
