Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Octodon”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed1982

Contact-promoting behavior, social development, and relationship with parents in sibling juvenile degus (Octodon degus).

This study describes infant socialization in captive parent-young units of the caviomorph rodent Octodon degus. Types of parent-young contact (huddling or squatting) and social interaction (body nosing and accompanying behaviors) are described and their ontogenetic trends examined between postnatal Days 1 and 46. Fathers spent less time than mothers in contact with the young. Mother-young contact decreased postnatally, whereas the amounts of mother-young and father-young social interaction, measured in terms of body-nosing exchanges, showed a continuous increase postnatally; sibling interactions also showed a continuous increase. Father-young interactions tended to be dominated by the father. Young reared with the father cohabiting huddled less with their mother, and engaged in less body-nosing, than young reared in the father's absence. Observations suggested that paternal control of the young may curb juvenile interactions. Young observed without their parents in an unfamiliar enclosure did not groom or "play" as in their home cage with parents present, but engaged in relatively more vocalizing, neck-nosing and forepaw-clasping.

Animals↗
PubMedDate not supplied

Identification of androgen binding-protein (ABP) from testis and epididymis of the seasonal rodent, Octodon degus (Molina, 1872).

ABP, a Sertoli cell secretory product, was identified in the seasonal rodent Octodon degus (Molina, 1872). It was shown to be present in cytosols from the testis and epididymis. It migrated with an Rf of 0.37 on nondenaturing polyacrylamide gels. Ligation of the vas efferens caused the disappearance of ABP from the epididymis and its accumulation in the testis, indicating its testicular origin. Binding to [3H]5 alpha-DHT was specific and completely reversible, with an apparent Kd of 3.5 +/- 0.4 X 10(-9) M. Half-times of association and dissociation were at 15 and 120 minutes, respectively. Binding equilibrium was achieved at 120 minutes. Steroid affinity relative to the best competitor, 5 alpha-DHT, was 0.27 for testosterone, 0.06 for 17 beta-estradiol, and 0.01 for cyproterone acetate. The presence and similar characteristics of ABP in a wide variety of mammals, including those with special reproductive strategies such as seasonal breeding, suggests that this protein may play a general role in the mechanisms regulating spermatogenesis, probably affecting the transport and concentration of androgens in the testis and epididymis.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1995

Photoperiod-induced changes in the proteins secreted by the male genital tract of the rodent Octodon degus.

The proteins secreted by the male genital tract were analyzed in the seasonally breeding rodent Octodon degus. The protein patterns from the fluids collected from sexually active animals were compared with those from animals in resting period, with others which were previously castrated, and with castrated animals which received testosterone replacement treatment. Fluids from cauda epididymides (CE), seminal vesicles (SV) and prostate glands (PG) were collected, and analyzed by polyacrylamide gel electrophoresis followed by different staining methods and densitometry. Modifications were detected in the protein patterns of resting or castrated animals. In CE fluid, the decrease of one protein band (45 Kda) and the uprising of another (210 Kda) were recognized after castration. In animals during resting period the changes were not as marked as in castrated animals. SV secretion demonstrated a similar response to resting phase and castration, because Protein SVS I (200 Kda) decreased or were not observed when these conditions occurred. PG fluid proteins were also modified after castration. In general, the more severe changes in the protein spectrum were induced by castration, despite radioimmunoassay showing that testosterone fall is even higher in resting period animals than in those castrated. Testosterone replacement resulted in recovery of a protein profile which is very similar to that of sexually active males. Results suggest that the androgenic control of male tract secretions would be rather different in this seasonal hystrichomorph when compared to the regulation system described for myomorph rodents.

Animals↗
PubMed1992

Stereotaxic atlas of the brain of Octodon degus.

We present a stereotaxic atlas of the brain of the trumpet-tailed rat or degu (Octodon degus), an hystricomorph rodent native to Chile and one which has become increasingly popular as a research animal, among other things because of its use as a model for diabetic cataracts and its tendency to become hyperglycemic. The atlas contains 38 transverse and two sagittal sections of the brain covering pros-, mes-, and rhombencephalon, as well as diagrams of the brain's surface anatomy. It was constructed from brains of young adult male degus but can be used readily in studies of adult females, since there is no apparent sexual dimorphism in the brain size of this rodent. Ninety percent of 40 experimental lesions used to check the accuracy of the atlas were correctly placed. The fore- and midbrain of the degu are generally more compact than corresponding regions of the brain in the laboratory rat (suborder Myomorpha) and the guinea pig (another hystricomorph). The amygdaloid complex extends further forward in the telencephalon. Major mesencephalic nuclei and fiber tracts are more rostral in position. However, superior and inferior colliculi are much longer in degus than rats. The basic organization of the rhombencephalon is similar in degus and rats, although there are clearcut differences in the length or size of some hindbrain nuclei.

Anatomy, Artistic↗
PubMed2000

Testicular hormones modulate circadian rhythms of the diurnal rodent, Octodon degus.

Sex differences have been identified in a variety of circadian rhythms, including free-running rhythms, light-induced phase shifts, sleep patterns, hormonal fluctuations, and rates of reentrainment. In the precocial, diurnal rodent Octodon degus, sex differences have been found in length of free-running rhythm (tau), phase response curves, rates of reentrainment, and in the use of social cues to facilitate reentrainment. Although gonadal hormones primarily organize circadian rhythms during early development, adult gonadal hormones have activational properties on various aspects of circadian rhythms in a number of species examined. Gonadectomy of adult female O. degus did not influence tau, phase angle of entrainment, or activity patterns in previous experiments. The present experiment examined the role of gonadal hormones in adult male degus' circadian wheel-running rhythms. We predicted that male gonadal hormones would have an activational effect on some aspects of circadian rhythms, particularly those in which we see sex differences. Phase angles of entrainment, tau, length of the active period (alpha), maximum and mean activity levels, and activity amplitude were examined for intact and castrated males housed in LD 12:12. Responses to light pulses while housed in constant darkness (DD) were also compared. Castration had no significant effect on tau or light-induced phase shifts. However, castration significantly increased phase angle of entrainment and decreased activity levels. The data indicate that adult gonadal steroids are not responsible for the sex differences in endogenous circadian mechanisms of O. degus (tau, PRC), although they influence activity level and phase angle of entrainment. This is most likely due to masking properties of testosterone, similar to the activity-increasing effects of estrogen during estrus in O. degus females.

Animals↗
PubMed2003

Visual adaptations in a diurnal rodent, Octodon degus.

The degu (Octodon degus) is a diurnal rodent, native to Chile. Basic features of vision and visual organization in this species were examined in a series of anatomical, electrophysiological and behavioral experiments. The lens of the degu eye selectively absorbs short-wavelength light and shows a progressive increase in optical density as a function of age. Electroretinograms recorded using a flicker-photometric procedure reveal three spectral mechanisms: a rod with peak sensitivity of about 500 nm and two types of cone having respective spectral peaks of about 362 nm and 507 nm. Opsin antibody labeling was used to determine the retinal distributions of the three receptor types. A total of about one-third of the approximately 9 million photoreceptors of the degu retina are cones with the two types (507 nm/362 nm) represented in a ratio of about 13:1. The contributions to vision of all three receptor types were examined in a series of behavioral experiments. A consistent feature of both the electrophysiological and behavioral results is that relatively high levels of light adaptation are required to effect the full transition from rod-based to cone-based vision. In behavioral tests degus were shown to be able to make color discriminations between ultraviolet and visible lights.

Adaptation, Ocular↗
PubMed1982

The lack of recognition of lactating females by infant Octodon degus.

A series of tests were conducted to determine whether infant degus (Octodon degus) will (a) show sensitivity to maternal olfactory cues and/or (b) discriminate between a novel adult lactating female and their mother. The pups showed no preferences when exposed to an array of different olfactory stimuli but did spend significantly more time in proximity with the novel lactating female than with their mothers. It is hypothesized that the communal rearing systems which are apparently characteristic of degus in the wild, coupled with the novelty of the lactating female, may account for these results.

Animals↗
PubMed1995

Sex differences and effects of social cues on daily rhythms following phase advances in Octodon degus.

Two experiments were designed to determine whether social cues could enhance the rate of resynchronization in body temperature and general activity rhythms in male or female Octodon degus following a 6 h phase advance. The first experiment examined average resynchronization rates for animals in each condition. The second experiment examined resynchronization rates for a smaller group of animals, each treated as its own control. Female phase-shifters resynchronized temperature and activity rhythms significantly faster when housed with an entrained (donor) female than those females housed with another phase-shifting female or housed alone. Females housed with entrained males resynchronized their temperature rhythms significantly slower than females housed with entrained females. No differences in resynchronization rate for phase-shifting males existed between test conditions. However, activity rhythms of male controls (housed alone) reentrained significantly faster than those of female controls. These experiments demonstrate a sex difference in (i) reentrainment rate by photic cues alone; (ii) donors' effect on female phase-shifters' resynchronization; and (iii) phase-shifters' resynchronization response to donor cues. In these studies, resynchronization in the presence of another animal could either have been achieved by entrainment of the pacemaker or by masking of the circadian rhythms.

Animals↗
PubMed1995

Estrus- and steroid-induced changes in circadian rhythms in a diurnal rodent, Octodon degus.

Diurnal Octodon degus exhibited marked alterations in activity and temperature in conjunction with the 3 wk estrous cycle when housed in LD12:12 light cycle. On the day of estrus, mean daily activity increases 109%, mean core temperature rises .4 degree C, activity onset is advanced 2 h, and amplitudes of both rhythms decline compared with the 3 days prior to estrus. On the day following estrus, activity onset was delayed 4.9 h, and mean activity and core temperature fell below that of the preestrus period. Ovariectomy significantly reduced mean temperature (.98 degree C) but did not significantly alter mean activity, and eliminated cyclic effects of estrus. Estrogen replacement led to a nonsignificant elevation in mean activity and core temperature with no change in the phase angle of entrainment. Progesterone replacement significantly reduced mean core temperature and mean activity, while only the phase angle difference between temperature minimum and activity onset was significantly altered. Intact degus maintained in constant darkness displayed only transient fluctuations in activity onset and temperature minimum during and after estrus. Estrogen or progesterone treatment of ovariectomized, free-running degus altered mean temperature and activity levels, but did not influence tau. Changes in phase angle of entrainment during estrus are not the result of hormone effects on the circadian clock but likely reflect increased or decreased levels of activity.

Animals↗
PubMedDate not supplied

Relationship of circadian activity and social behaviors to reentrainment rates in diurnal Octodon degus (Rodentia).

Previous experiments with female Octodon degus showed that entrained males (donors) inhibited and entrained females accelerated female phase-shifters' teentrainment rates of temperature and activity rhythms following 6-h advances. In this experiment, entrained males were housed with other entrained males or with phase-shifting females (experiencing a phase advance of the light-dark (LD) cycle) and entrained females were housed with other entrained females or with phase-shifting females. Pairs separated by a barrier were videotaped for 66 h to identify the behavioral interactions that underlie the opposite effects of donor social cues on reentrainment rates in females. As reported previously, female phase-shifters housed with entrained females reentrained faster than those "housed with entrained males following 6-h advances. Despite accelerated reentrainment, the timing or total durations of general activity, sleep, cage investigation, barrier investigation, and scent marking did not differ between female phase-shifters housed with male or female donors, although all phase-shifters increased investigatory behaviors compared to entrained animals. In contrast, male and female donors housed with female phase-shifters increased the frequency of scent marking and the duration of cage and barrier investigation compared with those housed with entrained same-sex conspecifics. Changes in scent marking and sniffing investigation suggest olfactory cues, not alterations in sleep or other daily rhythms, supply the critical social influence necessary to alter reentrainment rates in females. Daily and/or specific phase increases in motor activity did not correlate with accelerated reentrainment. We suggest that the salience of social cues perceived by female phase-shifters, female phase-shifters' sensitivity to cues and/or the strength of emitted donor cues may contribute to differential responses of the circadian system in females housed with male vs. female donors.

Animals↗
PubMed1996

Rhythms of body temperature and temperature selection are out of phase in a diurnal rodent, Octodon degus.

Individual Chilean degus (Octodon degus) were maintained in a thermal gradient (14 degrees C to 33 degrees C) for two or more weeks under a 14L:10D light-dark cycle. All animals showed robust daily rhythms of body temperature and locomotor activity consistent with the diurnal habits of the species. They also showed a robust daily rhythm of temperature selection 180 degrees out of phase with the rhythms of body temperature and locomotor activity. These results in a diurnal species extend previous findings of a 180 degrees phase difference between the rhythms of body temperature and temperature selection in nocturnal rodents. The asynchrony between these two rhythms implies an opposition between the circadian system (responsible for the generation of the body temperature rhythm) and the homeostatic system (responsible for the behavioral response of temperature selection that opposes the body temperature rhythm.

Animals↗
PubMed1992

Fibre digestion and digesta retention time in guinea-pigs (Cavia porcellus), degus (Octodon degus) and leaf-eared mice (Phyllotis darwini).

1. Digestibilities of feed and turnover time (1/k), Transit time (TT) and mean retention time (MRT: 1/k + TT) of fluid and particle markers were measured in the guinea-pig (Cavia porcellus), degu (Octodon degus) and leaf-eared mouse (Phyllotis darwini) fed a diet containing 50% alfalfa. 2. The digestibility of fibre and the retention time of digesta were highest in the guinea-pig followed by the degu and lowest in the leaf-eared mouse. 3. The difference in the retention time of digesta, resulting from the variation in the digestibility of fibre, between the three animals can be considered to be related to their body mass.

Animals↗
PubMed2004

Cost of living in free-ranging degus (Octodon degus): seasonal dynamics of energy expenditure.

Animals process and allocate energy at different seasons at variable rates, depending on their breeding season and changes in environmental conditions and resulting physiological demands. Overall total energy expenditure, in turn, should either increase in some seasons due to special added demands (e.g. reproduction) or it could simply remain at about the same level, in which case the animals must show compensatory rebalancing of other expenditures that can be reduced. To test for the alternative hypotheses of seasonal variability or compensation, we measured total daily energy expenditure (DEE) in free-living degus (Octodon degus) at four seasons and followed this with determinations of basal metabolic rate (BMR) in the laboratory in the same individuals. DEE varied seasonally but was only significantly different (lower) in summer (non-breeding season), with a DEE:BMR ratio of only 1.6, whereas autumn, winter and spring DEE values were statistically indistinguishable from one another and showed DEE:BMR ratios ranging from 1.9 to 2.2. Our values of DEE in the field fall within the broad range of allometric expectation for herbivorous mammals in general, but the ratios of DEE:BMR are lower than expected. This, together with the lack of strong major shifts in total levels of DEE, suggests that degus are showing compensatory shifts among various categories of energy expenditure that allow them to manage their overall energy balance by minimizing total expenditure.

Animals↗
PubMed2000

Effects of intergeniculate leaflet lesions on circadian rhythms in Octodon degus.

The intergeniculate leaflet (IGL) modulates photic and nonphotic entrainment of circadian rhythms in nocturnal species, but nothing is known about its role in diurnal species. We investigated the significance of the IGL for circadian rhythm function in the diurnal rodent, Octodon degus, by determining the effects of bilateral electrolytic IGL lesions (IGL(X)) on: (i) photic entrainment; (ii) reentrainment rates to photic cues following a 6-h phase advance of the light-dark (LD) cycle; (iii) reentrainment rates to nonphotic social and photic cues following a 6-h phase advance of the LD cycle; and (iv) the circadian period (tau) of the activity rhythm in constant darkness (DD). IGL(X) significantly lengthened the duration (alpha) of the entrained activity rhythm and produced a significantly earlier phase of activity onset under entrained (LD 12:12) conditions, but did not change phase of activity offset, rhythm amplitude or mean daily activity levels. IGL(X) failed to modify tau of free-running activity rhythms in DD or alter reentrainment rates of circadian rhythms to nonphotic social and photic cues or photic cues alone. Thus, the IGL modulates two parameters of photic entrainment, but is not necessary for reentrainment to either nonphotic social or photic cues. Our results contribute to the growing comparative database on the neural mechanisms controlling circadian rhythms and indicate that the role of the IGL varies across species with no apparent relationship between diurnality-nocturnality and circadian function.

Animals↗
PubMed1996

Early auditory filial learning in degus (Octodon degus): behavioral and autoradiographic studies.

Degu mothers (Octodon degus) utter specific maternal calls during nursing which presumably stimulate and reinforce suckling. Pups from surgically muted mothers show a reduced gain of body weight during postnatal development compared to pups from normally vocalizing mothers. Our behavioral studies suggest that the pups have to learn the meaning of the maternal calls during the first two weeks of life. Two-week-old pups from normally vocalizing mothers expressed a preference for the maternal call in a behavioral discrimination test, in contrast to pups from surgically muted mothers. Investigation of brain activities using the 2-[14C]fluoro-deoxyglucose (2-FDG) method revealed that pups from normal mothers display a significantly higher 2-FDG uptake in precentral medial, anterior cingulate cortex and a slight, non-significant increase in the prelimbic cortex and orbital PFC upon presentation of the maternal call, compared to pups from muted mothers, for which the maternal call was unfamiliar and meaningless. These prefrontal cortical areas are known to be involved in associative learning processes and our data suggest that they are involved in the association between the maternal call and the positive emotional situation during nursing.

Acoustic Stimulation↗
PubMed1998

Removal of the olfactory bulbs delays photic reentrainment of circadian activity rhythms and modifies the reproductive axis in male Octodon degus.

The diurnal rodent, Octodon degus, exhibits robust sex differences in several circadian measures, including circadian period (tau) and reentrainment rates to photic and nonphotic (social) zeitgebers. The neural substrates underlying such physiological differences remain unknown. In female degus, olfactory bulbectomies (BX) inhibit socially-facilitated reentrainment, but do not alter photic reentrainment, entrained measures, or tau in constant darkness (DD). This experiment investigated the effects of BX in male degus on (i) photic reentrainment rates of circadian rhythms following a 6-h phase advance of the light-dark (LD) cycle; (ii) photic entrainment; (iii) tau of free-running activity rhythms in DD; and (iv) body weight, paired testis weight, and the reproductive hormones, testosterone, androstenedione and follicle stimulating hormone (FSH). BX significantly delayed photic reentrainment rates. They did not, however, modify tau, the phase of activity onset or offset, amplitude or duration (alpha) of the activity rhythm, mean daily locomotor activity levels, or body weight. FSH, testosterone and androstenedione were unaffected by BX, whereas paired testis weights were significantly greater in BX degus compared with shams. Thus, the olfactory bulbs influence photic reentrainment of circadian rhythms and modestly affect the reproductive axis in male degus. Our results suggest that the olfactory bulbs may be a neural source of observed sex differences in photic reentrainment in degus, and highlight interspecies variation in the olfactory bulbs' effects on entrained and free-running circadian rhythms and on reproduction.

Animals↗
PubMed1997

Feeding and digesting fiber and tannins by an herbivorous rodent, Octodon degus (Rodentia:Caviomorpha).

Differences in feeding rates and digestive efficiency of alternative experimental diets differing in cellulose or fiber and a secondary metabolite (the hydrolyzable tannin, tannic acid [TA]) were assessed with the herbivorous burrowing caviomorph rodent Octodon degus (degu). Degus live in open scrub subjected to summer droughts. The in vitro activity of the digestive enzyme sucrase was not significantly different between treatments with high and low TA. Analysis of the whole organism allowed us to conclude that in vitro analyses of enzymatic digestive activity and plant defenses cannot be used to explain and fully understand the physiological and behavioral effects of plant defenses on mammalian herbivores. We observed no body mass reduction due to effects of dietary treatments. O. degus seemed to compensate for nutritionally poor food by increasing gut content volume. We conclude that fiber and secondary compounds may influence feeding and digestive strategies and vice versa.

Animals↗
PubMed2000

Quantitative changes in reduced nicotinamide adenine dinucleotide phosphate-diaphorase-reactive neurons in the brain of Octodon degus after periodic maternal separation and early social isolation.

The influence of preweaning maternal separation and postweaning social isolation on the development of reduced nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase-reactive neurons in prefrontal cortical areas, in subdivisions of the nucleus accumbens and in the corpus callosum was quantitatively investigated in the precocious rodent Octodon degus. Forty-five-day-old degus from three animal groups were compared: (i) degus that were reared under normal undisturbed social conditions; (ii) degus that were repeatedly separated from their mothers during the first three postnatal weeks and thereafter reared with their family; and (iii) degus that remained undisturbed with the family until weaning (postnatal day 21) and thereafter were reared in social isolation. Preweaning maternal separation led to a significant decrease in NADPH-diaphorase-containing neurons in the corpus callosum in both genders (down to 33%) compared with the social control group. No significant changes were found in the subregions of the medial prefrontal cortex and nucleus accumbens. Postweaning social isolation led to a reduced density of NADPH-diaphorase-containing neurons in the corpus callosum in both genders (down to 52%) compared with the social control group. Furthermore, in the precentral medial cortex of female pups, a significant reduction in NADPH-diaphorase-reactive neurons (down to 72%) was detectable. All other regions of the medial prefrontal cortex and the nucleus accumbens remained unchanged. The observed deprivation-induced changes may reflect either an excessive reduction in NADPH-diaphorase-positive neurons or a down-regulation of the enzyme in neurons that normally express it.Our results indicate a link between early adverse socio-emotional experience and the maturation of NADPH-reactive neurons. Further studies are required to analyse the functional implications of this experience-induced brain pathology.

Animals↗