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At least 127 records · Page 7Linked to original sources
PubMed2006

Circadian chronotypes among wild-captured west Andean octodontids.

Rest activity pattern was studied in wild-captured males of Octodon degus (n=9), Octodon bridgesi (n=3), and Spalacopus cyanus (n=6) (Rodentia: Octodontidae). Ten-minute resolution actograms were constructed from data obtained by an automated acquisition system. After two months of habituation to a stable light-dark schedule, recordings were performed in isolation chambers under a 12: 12 Light Dark schedule. A free-running period (constant darkness) was recorded for O. bridgesi and S. cyanus. O. degus displayed a crepuscular pattern of rest activity rhythm. Entrained O. bridgesi and S. cyanus displayed nocturnal preference, with rest anticipating light phase and without crepuscular activity bouts. Under constant darkness, active phase occurred at subjective night in O. bridgesi and S. cyanus. Wild-captured O. bridgesi and S. cyanus possess a circadian driven nocturnal preference, while wild O. degus displays a crepuscular profile. Diurnal active phase preference of wild S. cyanus colonies observed in the field could not be explained solely by photic entrainment, since social and/or masking processes appear to be operative. The genus Octodon includes species with diverse chronotypes. We propose that crepuscular diurnal pattern observed in O. degus is a recent acquisition among the octodontid lineage.

Adaptation, Physiological↗
PubMed1981

Visuo-limbic interactions. Evidence for a pathway from the pulvinar to the cingulate cortex.

Synaptic-terminal degeneration was analyzed in 18 specimens of Octodon degus after stereotaxic lesions in the pulvinar nucleus. Aside from the cortical targets of the pulvinar (Kuljis et al. 1979), a conspicuous projection towards the nucleus lateralis dorsalis of the thalamus (LD) was observed. The LD is known to receive fibers from the fornix (Valenstein and Nauta 1959), and to project heavily over the cingulate cortex (Locke et al. 1964; Ajmone Marsan 1965; Graybiel 1974); we have confirmed the latter projection in 3 operated specimens of Octodon degus. The possibility is discussed, in the light of these findings, that the pulvino-LD pathway may be important for the purposes of visuo-limbic interactions.

Animals↗
PubMed1983

Cholinergic transmission in vas deferens.

Prazosin, haloperidol, propranolol or timolol had no effect on the electrically evoked muscular twitch. Atropine was able to antagonize competitively acetylcholine (pA2 = 9.29 +/- 0.30). The muscular twitch of the Octodon degus vas deferens was only partially abolished by atropine (53.2 +/- 0.72). The present results can be interpreted assuming that the Octodon degus vas deferens has one component muscarinic in its innervation.

Acetylcholine↗
PubMed2004

Blood glucose concentration in caviomorph rodents.

Hystricomorph rodents are a group of species that belong to the suborder Hystricognathi. They mainly inhabit South American (caviomorph) and African (phiomorph) habitats. This group of rodents has a divergent insulin structure. For example, insulin in this group of rodents exhibits only 1-10% of biological activity in comparison to other mammals. Therefore, hystricomorph rodents may hypothetically be unable to regulate blood glucose concentration as non-hystricomorph mammals. In this work we evaluated blood glucose concentration in nine species of caviomorph rodents, with emphasis on species belonging to the families Abrocomidae, Ctenomyidae and Octodontidae. Specifically we: (1) measured glucose concentrations after a fasting period; and (2) conducted a glucose tolerance test. In the latter assay we used Octodon degus as a representative species of the genus Octodon. Results showed that blood glucose concentration values after fasting, and in the glucose tolerance test, were within the expected range for mammals. We postulate that this group of rodents has compensatory traits that may permit the maintenance of standard values of plasma glucose.

Animals↗
PubMed1999

Non-random distribution of the pericentromeric heterochromatin in meiotic prophase nuclei of mammalian spermatocytes.

The central or peripheral distribution of condensed chromatin (CC) was studied in pachytene spermatocyte nuclei in Mus domesticus, 2n = 40; Pudu puda, 2n = 70; Ctenomys opimus, 2n = 26 and Octodon degus, 2n = 58. Species were chosen according to the morphological characteristics of their chromosomal complements and in particular, the terminal or medial chromosomal localisation of the pericentromeric constitutive heterochromatin. Counts were made by defining the areas corresponding to peripheral and central location in each nuclear section from a series. The null hypothesis (i.e. random distribution of CC) was rejected. In the nuclear sections of Mus domesticus and Pudu puda, 69% and 74% of CC, respectively, was found in the peripheral nuclear space, while in those of Octodon degus and Ctenomys opimus, 69% and 65% of CC, respectively, was found in the central nuclear space. We estimate that if the CC measured in spermatocyte nuclei corresponds mainly to pericentromeric constitutive heterochromatin, the distribution found is consistent with that expected in accordance with the nuclear architecture model for meiocytes (Fernández-Donoso, 1982; Fernández-Donoso & Berrios, 1985). This model proposes a peripheral nuclear localisation for pericentromeric heterochromatin of telocentric bivalents and a relatively central nuclear localisation for pericentromeric heterochromatin of metacentric bivalents. We also discuss some of the biological consequences that could arise from the conservation of such distributions.

Animals↗
PubMed2003

Lupus-erythematosus-like eruption induced by Trichophyton mentagrophytes infection.

BACKGROUND: Several factors are known to trigger acute manifestations of lupus erythematosus (drugs, ultraviolet radiation, bacterial or viral infections, pregnancy), but fungal infections have never been reported to induce lupus-like lesions. We describe 2 children with tinea capitis caused by Trichophyton mentagrophytes(TM), who developed transient skin and serological manifestations of systemic lupus erythematosus. PATIENTS: Case 1, a 3-year-old girl, had a kerion due to TM transmitted by an octodon, and a facial skin eruption suggestive of systemic lupus erythematosus. Antinuclear antibodies (ANA) were positive at 1:250. After griseofulvin treatment, the lupus-like rash completely regressed, and the ANA titre decreased. Case 2, a 4-year-old girl, had occipital kerion and an annular scaly erythema on the shoulder caused by TM. She also had a non-scaly rash on the face and a recent history of photosensitivity. The ANA titre was positive at 1:8,000. Cutaneous lesions disappeared after an 8-week griseofulvin therapy, and ANA titres decreased progressively. CONCLUSIONS: 'New pets' are usually the vectors of TM, especially familiar rodents like the degu of Chile (also named octodon). In our 2 cases, lupus-like rashes began before the onset of griseofulvin treatment, suggesting a pathogenic role of the dermatophyte. A wide variety of lesions named 'mycides' was described several decades ago associated with TM infections. We hypothesize that these mycides and the TM-induced lupus-like lesions reported in our 2 cases could represent the same entity.

Animals↗
PubMed2005

Early social environment interferes with the development of NADPH-diaphorase-reactive neurons in the rodent orbital prefrontal cortex.

The influence of early parental deprivation on the development of NADPH-diaphorase-(NO-synthase) reactive neuron numbers in subregions of the orbital prefrontal cortex (ventrolateral orbital, lateral orbital, and agranular insular cortex) was quantitatively investigated in the precocious lagomorph Octodon degus. Forty-five-day-old degus from three groups were compared: (1) repeated parental separation: degus that were repeatedly separated from their parents during the first three postnatal weeks and thereafter raised in undisturbed social conditions; (2) chronic isolation: degus that were raised under undisturbed social conditions until postnatal day 21, and then were reared in chronic social isolation; and (3) control: degus that were reared undisturbed in their families. Compared to the control animals the ventrolateral orbital prefrontal cortex and agranular insular cortex of the two deprived groups displayed significantly decreased density of NADPH-diaphorase-reactive neurons (down to 62% in the ventrolateral orbital prefrontal cortex of males, 70% in the agranular insular cortex, and in the lateral orbital prefrontal cortex 80% in both genders). These results confirm that early changes of social environment interferes with the development of limbic circuits, which might determine normal or pathological behaviors in later life.

Animals↗
PubMed2006

Early neonatal and postweaning social emotional deprivation interferes with the maturation of serotonergic and tyrosine hydroxylase-immunoreactive afferent fiber systems in the rodent nucleus accumbens, hippocampus and amygdala.

The impact of early emotional experience on the development of serotonergic and dopaminergic fiber innervation of the nucleus accumbens, hippocampal formation and the amygdala was quantitatively investigated in the precocious rodent Octodon degus. Two animal groups were compared: 1) degus which were repeatedly separated from their parents during the first three postnatal weeks, after weaning they were individually reared in chronic social isolation and 2) controls which were reared undisturbed with their families. In the deprived animals 5-hydroxytryptamine-immunoreactive fiber densities were increased in the core region of the nucleus accumbens (up to 126%), in the central nucleus of the amygdala (up to 112%) and in the outer subregion of the dentate gyrus stratum moleculare (up to 149%), whereas decreased fiber densities were detected in the dentate subgranular layer (down to 86%) and in the stratum lacunosum of the hippocampal cornu ammonis region 1 (down to 86%). Tyrosine hydroxylase-immunoreactive fiber densities were increased in the core (up to 115%) and shell region (up to 113%) of the nucleus accumbens of deprived animals, whereas decreased fiber densities (down to 84%) were observed in the hilus of the dentate gyrus. In the stratum granulosum and subgranular layer the fiber densities increased up to 168% and 127% respectively. In summary, these results indicate that the postnatal establishment of the monoaminergic innervation of limbic areas is modulated in response to early emotional experience, and that this environmental morphological adaptation is highly region specific.

Adaptation, Physiological↗
PubMed2004

Inhibiting cortisol response accelerates recovery from a photic phase shift.

Jetlag results when a temporary loss of circadian entrainment alters phase relationships among internal rhythms and between an organism and the outside world. After a large shift in the light-dark (LD) cycle, rapid recovery of entrainment minimizes the negative effects of internal circadian disorganization. There is evidence in the existing literature for an activation of the hypothalamic-pituitary-adrenal (HPA) axis after a photic phase shift, and it is possible that the degree of HPA-axis response is a determining factor of reentrainment time. This study utilized a diurnal rodent, Octodon degus, to test the prediction that the alteration of cortisol levels would affect the reentrainment rate of circadian locomotor rhythms. In experiment 1, we examined the effects of decreased cortisol (using metyrapone, an 11beta-hydroxylase inhibitor) on the rate of running-wheel rhythm recovery after a 6-h photic phase advance. Metyrapone treatment significantly shortened the length of time it took animals to entrain to the new LD cycle (11.5% acceleration). In experiment 2, we examined the effects of increased cortisol on the rate of reentrainment after a 6-h photic phase advance. Increasing plasma cortisol levels increased the number of days (8%) animals took to reentrain running-wheel activity rhythms, but this effect did not reach significance. A third experiment replicated the results of experiment 1 and also demonstrated that suppression of HPA activity via dexamethasone injection is capable of accelerating reentrainment rates by approximately 33%. These studies provide support for an interaction between the stress axis and circadian rhythms in determining the rate of recovery from a phase shift of the LD cycle.

Adaptation, Physiological↗
PubMed2005

Restraint stress delays reentrainment in male and female diurnal and nocturnal rodents.

A temporary loss of normal circadian entrainment, such as that associated with shift work and transmeridian travel, can result in an array of detrimental symptoms, making rapid reentrainment of rhythmicity essential. While there is a wealth of literature examining the effects of stress on the entrained circadian system, less is known about the influence of stress on circadian function following a phase shift of the light: dark (LD) cycle. The authors find that recovery of locomotor activity synchronization is altered by restraint stress in the diurnal rodent Octodon degus (degu) and the nocturnal rat. In the first experiment, degus were subjected to a 6-h phase advance of the LD cycle. Sixty minutes after the new lights-on, animals underwent 60 min of restraint stress. The number of days it took each animal to reentrain its activity rhythms to the new LD cycle was recorded and compared to the number of days it took the animal to reentrain under control conditions. When subjected to restraint stress, degus took 30% longer to reentrain their activity rhythms (p < 0.01). In a second experiment, rats underwent a similar experimental paradigm. As with the degus, stress significantly delayed the reentrainment of rats' activity rhythms (p < 0.01). There was no interaction between sex and stress on the rate of reentrainment for either rats or degus. Furthermore, there was no effect of stress on the free-running activity rhythm of degus, suggesting that the effect of stress on reentrainment rate is not secondary to alterations of period length. Together, these data point to a detrimental effect of stress on recovery of entrainment of circadian rhythms, which is independent of activity niche and sex.

Animals↗
PubMed2006

What explains the trot-gallop transition in small mammals?

The transition from trot to gallop in quadruped mammals has been widely hypothesized to be a strategy to minimize the energetic costs of running. This view, however, has been challenged by some experimental evidence suggesting instead that this transition might be triggered by mechanical cues, and would occur when musculoskeletal stresses reach a certain critical value. All previous experiments to test those hypotheses have used relatively large species and their results, therefore, may not be applicable to small mammals. In this study we evaluated the effect of carrying loads on the locomotor energetics and gait transitions of the rodent Octodon degus running on a treadmill. Metabolic rate and cost of transport increased about 30% with a 20% increment in body mass. This increment was higher than expectations based on other mammals, where energy consumption increases in proportion to the added mass, but similar to the response of humans to loads. No abrupt change of energy consumption between gaits was observed and therefore no evidence was found to support the energetic hypothesis. The trot-gallop transition speed did not vary when subjects were experimentally loaded, suggesting that the forces applied to the musculoskeletal system do not trigger gait transition.

Animals↗
PubMed1996

Comparison of the body temperature rhythms of diurnal and nocturnal rodents.

The daily rhythm of body temperature of six rodent species, three of them nocturnal (Rattus norvegicus, Mesocricetus auratus, and Meriones unguiculatus) and three diurnal (Octodon degus, Spermophilus tridecemlineatus, and S. richardsoni), was studied by telemetry under a 14L:10D light-dark cycle. Significant interspecies differences were found in the mean level (range: 36.0-37.4 degrees C), amplitude (range: 2.1 degrees-4.3 degrees C), robustness (range: 115-185 Qp), and acrophase (range: 8.5-16.0 hr) of the temperature rhythm. In addition, a positive correlation (r = 0.79) was found between body mass and robustness of the rhythm across species. However, the only consistent difference between the diurnal and nocturnal species was the acrophase, which occurred during the day in the diurnal species (range: 8.5-11.5 hr) and during the night in the nocturnal species (range: 13.5-16.0 hr).

Animals↗
PubMed2000

Lung morphology in rodents (Mammalia, Rodentia) and its implications for systematics.

A new nomenclature of the lung lobes and of the bronchial tree is presented, with which the lungs in 40 species of 11 rodent families are described. Whole, fixed lungs and silicone casts of the bronchial tree are tested for 23 characters, based on the distribution of lung lobes, the number and geometry of first order bronchi, the pulmonary blood supply, and lung symmetry. Ten lung morphotypes are recognized, seven of them representing one or more families: Castor type (Castoridae), Cryptomys type (Bathyergidae), Ctenodactylus type (Ctenodactylidae), Eliomys type (Gliridae), Myocastor type (Myocastoridae), Octodon type (Octodontidae and Echimyidae) and Rattus type (Sciuridae, Muridae pt. and Dipodidae). The Hydromys type is found only in Hydromys chrysogaster (Muridae), while Galea type A and B both appear in Galea musteloides (Caviidae). The data are phylogenetically analyzed by the program PAUP 4.0 using as outgroup Lagomorpha or Insectivora. On the species level, there are no well-resolved cladograms. On the family level, the cladograms do not contradict traditional rodent systematics with one exception: the Caviidae do not fall within Caviomorpha or even within the Hystricomorpha, but form a sister group to Dipodidae (Myomorpha). This appears to be a result of convergence. The lungs of Gliridae are more similar to those of Muridae than to those of Sciuridae. Included in the ingroup, Oryctolagus (Lagomorpha) forms a clade with Caviidae + Dipodidae. Thus, the "Glires hypothesis" is neither supported nor refuted.

Animals↗