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At least 91 records · Page 5Linked to original sources
PubMed2003

Testosterone suppresses circadian responsiveness to social cues in the diurnal rodent Octodon degus.

The diurnal, social rodent Octodon degus displays a robust sex difference in the ability to use social cues to facilitate reentrainment following a phase advance of the light cycle. Adult females housed with a female social cue donor reentrained 25% to 40% faster than did females reentraining alone. However, reentrainment rates of males were unaffected by exposure to female social cues during reentrainment. The authors hypothesized that males were less sensitive to the reentrainment-enhancing effects of social cues and that their higher threshold to the stimuli could be overcome if the social cues were either increased in strength or salience. Housing a male with two females significantly shortened the time to reentrain following a 9-h phase advance (p = 0.002). Housing with a sister had no effect on reentrainment. Therefore, male degus are able to respond to social cues but require the stimulus to be stronger than that for females. The effect of testosterone was tested by comparing reentrainment rates of castrated males before and after testosterone replacement both with and without a female social cue donor. Castrated males responded to a single female social cue donor, reentraining 35% faster than when housed alone (p = 0.006), whereas the time to reentrainment of intact males and males with testosterone capsule implants did not differ. Intact females were also implanted with testosterone and phase shifted with and without donors. Testosterone treatment eliminated the increase in reentrainment rates in the presence of social cues. The authors conclude that the rate of recovery from odor-enhanced phase shifts is modulated by activational effects of testosterone in male degus. Testosterone is also effective in suppressing social cue responsiveness in females, suggesting that testosterone's effects on responsiveness are not sexually dimorphic. This hormonal effect likely occurs by altering sensory system functions or CNS response to sensory information.

Animals↗
PubMed1997

Olfactory bulbectomy impedes social but not photic reentrainment of circadian rhythms in female Octodon degus.

Recent studies demonstrated that nonphotic (social) cues markedly accelerate reentrainment to large phase shifts of the light-dark (LD) cycles in female Octodon degus and that such changes are likely effected by chemosensory stimuli. This experiment investigated the effects of olfactory bulbectomies on (1) socially facilitated reentrainment rates of circadian rhythms following a 6-h phase advance of the LD cycle, (2) photic reentrainment rates of circadian rhythms following a 6-h advance of the LD cycle, (3) photic entrainment, and (4) the circadian period (tau) of activity rhythms in constant darkness (DD). olfactory bulbectomies (BX) blocked socially facilitated reentrainment rates but did not alter reentrainment rates of circadian rhythms to photic cues alone. In addition, BX lowered mean daily locomotor activity levels and decreased the amplitude of the activity rhythm in degus housed in entrained (LD 12:12) conditions but did not alter the phase of activity onset or offset, duration (alpha) of activity, or mean daily core body temperature. Bulbectomies also failed to modify tau of free-running activity rhythms. This experiment confirms that the olfactory bulbs and chemosensory cues are necessary for socially facilitated reentrainment. In contrast to their effects in nocturnal rodents, BX do not produce significant circadian photic changes in diurnal degus. This is the first experiment to determine that chemosensory stimuli modulate the circadian system in a diurnal rodent.

Animals↗
PubMed1997

The induction of Fos-like proteins in the suprachiasmatic nuclei and intergeniculate leaflet by light pulses in degus (Octodon degus) and rats.

In nocturnal rodents, exposure to light results in an increase in Fos expression in two regions that receive direct retinal input: the suprachiasmatic nuclei (SCN) of the hypothalamus and the intergeniculate leaflet (IGL) of the thalamus. The induction of Fos within the SCN of nocturnal rodents is phase dependent, with light presented during the subjective night increasing Fos expression and light presented during the subjective day having little effect. By contrast, Fos expression increases in the IGL when light is presented during the subjective day or night. It is unclear whether Fos is part of the pathway mediating light-induced phase shifts in diurnal rodents. In the present study, the ability of light to induce immunostaining for Fos in the SCN and IGL was compared in diurnal rodents, Octodon degus (degus), and nocturnal rats. Degus and rats were either maintained in constant darkness or exposed to a 1-h light pulse at circadian time (CT) 4 or 16. Degus exhibit robust phase shifts at each of those circadian hours, whereas rats demonstrate phase shifts only at CT 16. In degus, exposure to a 1-h light pulse at CT 16 resulted in an increase in the number of Fos-immunopositive (Fos+) cells in the ventrolateral SCN. By contrast, a 1-h light pulse at CT 4 resulted in a decrease in the number of Fos+ cells in the dorsomedial portion of the SCN. In rats, a light pulse presented at CT 16 resulted in an increase in Fos+ cells throughout the SCN, and a pulse at CT 4 had no effect on Fos staining. Both degus and rats showed increases in Fos expression in the IGL after light exposure at CTs 4 and 16. The authors conclude that light pulses presented at times that produce phase shifts in activity rhythms also alter Fos expression in the SCN and IGL of degus. Although these effects of light exposure on Fos expression are not identical in diurnal and nocturnal rodents, it is likely that Fos and other immediate early genes are part of the pathway mediating the effects of light in both diurnal and nocturnal rodents.

Animals↗
PubMed1990

Cloning of complementary DNAs encoding islet amyloid polypeptide, insulin, and glucagon precursors from a New World rodent, the degu, Octodon degus.

The degu, Octodon degus, is a South American hystricomorph rodent that is of interest because it develops spontaneous diabetes mellitus and has been found to have islet amyloidosis. To help clarify these problems we have cloned cDNAs encoding islet amyloid polypeptide (IAPP), insulin, and glucagon precursors from this species. The predicted amino acid sequence of degu IAPP is very similar to that of nonamyloid-forming guinea pig IAPP. In contrast, degu insulin and the C-terminal region of degu glucagon are highly divergent from those of other mammals, as is also the case in the guinea pig, suggesting the existence of some form of positive evolutionary pressure on these hormones of carbohydrate metabolism in the hystricomorph rodents.

Amino Acid Sequence↗
PubMed1979

Early postnatal physical and behavioural development of degus (Octodon degus).

6 litters of Octodon degus were studied from birth to 10 days of age. Newly-born degus (mean weight 14.6 g) had open eyes, upper and lower pigment, fur, and teeth. Within 3-4 hours of birth they were able to walk supporting their full weight, right themselves rapidly, sit upright on their haunches, or rear upright with support, and vocalize. By the 1st or 2nd day, the young animals displayed functional grooming (face washing, hind-paw scratching, rapid head-shake). Solid food was ingested from day 6, although newborns chewed wood chips and 3-day olds gnawed dried faeces. Young degus were tested daily in an open field apparatus and showed increased activity and exploration, with repeated testing while decreasing distress vocalization after the 4th or 5th day. Degus are proposed for the study of developmental topics since their degree of development at birth allows for immediate testing. The degus studied here seem to be more fully developed at birth than those studied in Britain.

Animals↗
PubMed1989

Cataract prevention in diabetic Octodon degus with Pfizer's sorbinil.

The Octodon degus has been reported to have higher aldose reductase activity in the lens compared to the gerbil and rat. When made diabetic the degus develop cataracts within 4 weeks. We have been able to completely prevent cataract formation in diabetic degus using Pfizer's sorbinil for up to 6 months. This is further evidence of the role of aldose reductase in the formation of cataracts in diabetes.

Aldehyde Reductase↗
PubMed1990

Bronchioalveolar carcinoma with renal and hepatic metastases in a degu (Octodon degus).

A primary bronchioloalveolar carcinoma with renal and hepatic metastases was diagnosed in a mature male degu (Octodon degus) that was found dead in a zoological exhibit (Buffalo Zoological Gardens, Buffalo, New York, USA). Grossly, a discrete 0.5 cm diameter nodule was seen in the lung. Smaller, but similar nodules were present scattered in the liver and kidneys. Histologically, nests and sheets of an infiltrating population of cuboidal to low columnar neoplastic epithelial cells partially effaced pulmonary architecture. Vascular invasion was evident. Similar nests and sheets of neoplastic cells were present within the renal cortex and medulla, and a small nest was present within the hepatic parenchyma. This is the first record of this neoplasm in a degu.

Adenocarcinoma, Bronchiolo-Alveolar↗
PubMed1975

Congenital cataracts associated with disorganized meridional rows in a new laboratory animal: the degu (Octodon degus).

A new laboratory animal, Octodon degus, a hystricomorph rodent, was found to display a naturally occurring congenital cataract. Histological examination of the lens epithelium revealed that a marked disorganization of the meridional rows is associated with the opacity. Studies of offspring of cataractous parents indicates that the disorganization precedes cataract appearance. These findings are discussed in reference to a general theory of meridional row involvement in a number of types of cataracts.

Animals↗
PubMed2003

Separation-induced receptor changes in the hippocampus and amygdala of Octodon degus: influence of maternal vocalizations.

Relatively little is known about the basic mechanisms that play a role in the vulnerability of the developing brain toward adverse environmental influences. Our study in the South American rodent Octodon degus revealed that repeated brief separation from the parents and exposure to an unfamiliar environment induces in the hippocampal formation of male and female pups an upregulation of D1 and 5-HT1A receptor density in the stratum radiatum and stratum lacunosum moleculare of the CA1 region. In the CA3 region, only the 5-HT1A receptors were upregulated; no changes were observed for D1 receptors in this region. GABA(A) receptor density in the hippocampus and amygdala was downregulated (nonsignificant trend) after parental separation. The acoustic presence of the mother during parental separation suppressed the D1 and 5-HT1A receptor upregulation in some regions of the hippocampus; no such suppressing influence was observed for the GABA(A) receptors. In the basomedial amygdala, the maternal calls enhanced the separation-induced 5-HT1A receptor upregulation in the male pups, whereas in the female pups the separation-induced receptor densities were not only suppressed by the maternal call but further downregulated, compared with the control group. These results demonstrate that early adverse emotional experience alters aminergic function within the hippocampus and amygdala and that the mother's voice, a powerful emotional signal, can modulate these effects in the developing limbic system.

Acoustic Stimulation↗
PubMed1978

Hematologic and serum protein reference values of the Octodon degus.

Blood and serum from normal degus (Octodon degus) that ranged in age from 3 to 48 months were analyzed to determine reference hematologic and serum protein values. Both sexes were evaluated and were similar. The hematologic and serum protein values for males were: erythrocytes, 8.69 +/- 0.19 X 10(6) /microliter; packed cell volume, 42.1% +/- 0.59%; hemoglobin, 12.0 +/- 0.15 g/dl; leukocytes, 8.50 +/- 0.39 X 10(3)/microliter; neutrophil-to-lymphocyte ration, 40:60; and total protein, 5.70 +/- 0.20 g/dl. The hematologic and serum protein values for females were: erythrocytes, 8.94 +/- 0.16 X 10(6)/microliter; packed cell volume, 40.0% +/- 0.61%; hemoglobin, 11.7 +/- 0.17 g/dl; leukocytes, 8.20 +/- 0.36 X 10(3)/microliter; neutrophil-to-lymphocyte ratio, 40:60; and total protein, 5.62 +/- 0.18 g/dl. The hematologic and serum protein values for the degu were similar in some respects to values reported for guinea pigs and rats.

Animals↗
PubMed1997

Functional organization of the auditory cortex in a native Chilean rodent (Octodon degus).

The tonotopic organization of primary auditory cortex (AI) and surrounding secondary regions has been studied in the Octodon degus using standard microelectrode mapping techniques. The results confirm and extend previous observations made in other species. The tonotopic organization of the largest field (AI) apparently covered the hearing range of O. degus. Low tonal frequencies were represented rostroventrally and high frequencies caudally, with isofrequency contours orientated dorsoventrally in a ventrocaudal slant. There were additional tonotopic representations adjacent to AI. Rostral to AI, a small field with a tonotopic gradient reversed with respect to that in AI (mirror image representation) was mapped and termed rostral auditory field (R). Best frequencies (BF's) in a range from 0.1-30.0 kHz were found in AI and R, with higher spatial resolution for the representation of lower BF's up to 10.0 kHz. Responses obtained in AI as well as in R were strong, with narrow tuning and short latencies. Caudal to AI, two small additional, tonotopically organized fields, the dorsoposterior field (DP) and the ventroposterior field (VP), could be distinguished. In fields VP and DP, high BF's were situated rostrally, adjacent to the high frequency representation in AI. Low frequency representations were found in caudal part of DP and VP fields. Responses to tone burst within DP and VP were mostly weak, with longer latencies and broader tuning compared to those found in AI and R.

Acoustic Stimulation↗
PubMed2006

Placentation in the degu (Octodon degus): analogies with extrasubplacental trophoblast and human extravillous trophoblast.

This study examined the placentation in the degu, the origin of the extrasubplacental trophoblast (EST) (extravillous trophoblast in human), and the activity of Na+/K+ ATPase in the placental barrier during different gestational ages, as part of a wider effort to understand the reproductive biology of this species. Fifteen degus at the first stage of gestation, midgestation and at term of pregnancy were studied. At day 27 of gestation, the subplacenta is formed under the wall of the central excavation. Simultaneously, the outermost trophoblast of the ectoplacental cone differentiated into secondary trophoblast giant cells that lie on the outside of the placenta, forming an interface with the maternal cells in the decidua. These giant cells immunostained positive for cytokeratin (CK) and placental lactogen (hPL) until term. During this period, the EST merged from the subplacenta to the decidua and immunostained negative for CK, but at term, immunostained for CK and hPL in the maternal vessels. The vascular mesenchyme of the central excavation invaded the chorioallantoic placenta during this period, forming two fetal lobules of labyrinthine-fine syncytium, the zone of the placental barrier. The activity of Na+/K+ ATPase in the placental barrier was constant during the gestational period. The residual syncytium at the periphery of the placental disc and between the lobules was not invaded by fetal mesenchyme and formed the marginal and interlobular labyrinthine syncytium that immunostained first for CK, and later for hPL, as in the labyrinthine fine syncytium. The presence of intracytoplasmic electron-dense material in the interlobular labyrinthine syncytium suggested a secretory process in these cells that are bathed in maternal blood. Placentas obtained from vaginal births presented a large, single lobe, absence of the subplacenta, and a reduced interlobular labyrinthine syncytium. At day 27, the inverted visceral yolk sac is observed and its columnar epithelium immunostained for CK and hPL. This suggests that the yolk sac is an early secretory organ. The epithelium of the parietal yolk sac covers the placenta. The origin of the EST in the degu placenta and its migration to maternal vessels allows us to present this animal model for the study of pregnancy pathologies related to alterations in the migration of the extravillous trophoblast.

Animals↗
PubMed1997

Influence of experience on the representation of the "mothering call" in frontoparietal and auditory cortex of pups of the rodent Octodon degus: FDG mapping.

Several types and subtypes of vocalizations which have a behavioral impact on degu pups were identified. Among these the complex "mothering call" which is exclusively uttered by females and first during extensive nursing periods in the nest is a candidate for filial learning. In 14C-2-fluoro-2-deoxyglucose (FDG) experiments two-weeks-old pups raised by normal mothers showed higher metabolic activity in somatosensory frontoparietal and frontal cortex upon play back of a mothering call than pups raised by muted mothers. It is suggested that pups learn to associate the mothering call with close body contact with their mother early in life. In addition, FDG representation of the call, of its components and of tone and noise stimuli were studied in degu auditory cortex. Five fields and some aspects of tonotopic organization were identified. The mothering call activated all fields, but with more spatial extent of labeling in normally raised pups. A rostral field was activated by play-back of the mothering call, noise, and two-tone sequences, but hardly by single-frequency tones and the narrow-band component of the mothering call.

Acoustic Stimulation↗