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At least 127 records · Page 7Linked to original sources
PubMed1998

Torpor patterns in the pouched mouse (Saccostomus campestris; Rodentia): a model animal for unpredictable environments.

Patterns of spontaneous and induced daily torpor were measured in the Afrotropical pouched mouse (77-115 g), Saccostomus campestris, in response to photoperiod, temperature, and food deprivation, using temperature telemetry. Photoperiod had no influence on the incidence, depth, or duration of daily torpor in either males and females. Although the testis size index decreased in response to food deprivation and photoperiod by a maximum of 24%, full testis regression did not occur. Torpor bout duration was, on average, 5.3 h, independent of photoperiod and ambient temperature. Males did not enter torpor in response to food deprivation but did in response to low ambient temperature, though significantly less frequently than females. At normothermia, the body temperatures (daily minimum, mean, maximum) of males were significantly lower than those of females. Minimum body temperatures of both males and females during torpor did not fall below 20 degrees C at an ambient temperature of 15 degrees C. The patterns of torpor measured here differ from those observed in species from strongly seasonal environments. They suggest adaptation to an environment rendered unpredictable by the El Niño Southern Oscillations. As an aseasonal, opportunistic breeder capable of year-round adaptive hypothermia, the pouched mouse represents an excellent model animal for research on physiological and behavioral adaptations to unpredictable environments.

Adaptation, Physiological↗
PubMed1997

Litomosoides chagasfilhoi sp. nov. (Nematoda:Filarioidea) parasitizing the abdominal cavity of Akodon cursor (Winge, 1887) (Rodentia:Muridae) from Brazil.

Litomosoides chagasfilhoi sp. nov., a parasite of the abdominal cavity of the wild rodent Akodon cursor (Winge. 1887), is described herein according to investigations conducted by light and scanning electron microscopy. The leading morphological characteristics of the new species are as follows: the buccal capsule is higher than it is wide and has walls thinner than the lumen, and the left spicule presents a handle longer than the blade, whose edges from large membranous wings folded longitudinally. This new species is different from L. silvai Padilha and Faria, 1977, living in the thoracic cavity of the same host.

Abdomen↗
PubMed1999

Calomys callosus (Rodentia : Cricetidae) trophoblast cells as host cells to Toxoplasma gondii in early pregnancy.

The potential of the RH strain of Toxoplasma gondii to invade trophoblast cells of the cricetid rodent Calomys callosus in a congenital infection in the initial third of pregnancy was investigated in this study using morphological and immunocytochemical approaches. The animals were intraperitoneally inoculated on the 1st day of pregnancy and the infection was observed on day 7. Various numbers of parasites could be observed inside the parasitophorous vacuoles in trophoblastic cells under light and electron microscopy. The trophoblast cells showed characteristics of healthy cells, and no alteration other than parasite vacuoles in their cytoplasm could be detected. Polyclonal or monoclonal anti-T. gondii antibodies (respectively, anti-T. gondii components and the major surface parasite antigen p30) labeled both the parasite surface and parasitophorous vacuole membranes, regardless of the number of parasites inside the compartment. In addition, p30-containing trails were detected in the extracellular matrix surrounding trophoblastic cells similar to those found with other parasites during locomotion and the invasion process. Our results show the ability of T. gondii to infect trophoblast cells during the early blastocyst-endometrial relationship and open new possibilities for more accurate study of the invasion process of this parasite and the role of the trophoblast as an embryo defense barrier.

Animals↗
PubMed2006

Chromosome plasticity in Ctenomys (Rodentia Octodontidae): chromosome 1 evolution and heterochromatin variation.

A chromosome 1 (Cr1) pericentric inversion is described in six of seven species in the genus Ctenomys (tuco-tucos) from Uruguay. The inversion was inferred from G-band analyses of subtelocentric Cr1 hypothesised to be derived from the ancestral metacentric condition. Cr1 varies across species in heterochromatin amount and localisation including a metacentric chromosome without positive C-bands in C. torquatus, a subtelocentric chromosome with heterochromatic short arms in C. rionegrensis, and a subtelocentric chromosome negative after C-banding in five of the species analysed here. Pachytene chromosomes from C. rionegrensis, a species with the highest heterochromatin content, and C. torquatus, one of the species with the lowest heterochromatin content, were analysed in order to assess possible mechanisms of heterochromatin evolution. This analysis revealed the presence of three heterochromatic chromocenters in C. rionegrensis where bivalents converge, while in C. torquatus only one chromocenter was observed. In both species, highly repetitive DNA was observed, localised in chromocenters after "in situ" hybridisation. Heterochromatin associated protein M31 was localised in chromocenters of both species after immuno-detection. The spread of heterochromatin in Ctenomys chromosomes could be produced by chromatin exchanges at the chromocenter level. We propose the exchange of this DNA associated proteins between non-homologous chromosomes in pachytene to be the responsible for the spread of heterochromatin through the karyotypes of species like C. rionegrensis.

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↗
PubMed1980

Leishmaniasis in Tuscany (Italy): (II) Leishmania from wild Rodentia and Carnivora in a human and canine leishmaniasis focus.

From April 1977 to February 1978, wild mammals were trapped in a focus of low leishmanial endemicity (Baccinello) in the Province of Grosseto (Tuscany, Italy). Spleen homogenates of the trapped animals were injected i.p. into hamsters, from which spleen biopsies were taken after 60 days and impression smears carefully observed for the presence of Leishmania. Positive spleens were subinoculated into hamsters. 404 animals of 12 species were trapped: 31 insectivores, 317 rodents and 56 carnivores. Black rats (Rattus rattus) and field mice (Apodemus sylvaticus) were the rodent species most frequently trapped--160 and 139 respectively--of which 143 and 134 respectively were tested in hamsters for Leishmania. 35 foxes (Vulpes vulpes) were caught, of which 16 were tested for Leishmania. Four hamsters were found infested with Leishmania. Three of them had been injected with spleen homogenates from R. rattus and one from V. vulpes although liver and spleen impression smears of all trapped animals were negative for Leishmania on direct microscopical examination. The significance of Leishmania infection in wild animals in the leishmanial focus of Baccinello is discussed.

Animal Population Groups↗
PubMed1978

Protein variation and systematics in Malayan rats of the subgenus Lenothrix (Rodentia: Muridae, genus Rattus Fischer).

1. Electrophoretic variations of 9 erythrocyte proteins, coded by a separate gene locus each, were analysed in and among the 5 Malayan species of Rattus belonging to the subgenus Lenothrix. 2. The average proportion of loci heterozygous per individual for the taxa analysed is 0.037. 3. The results obtained confirm the specific status of the 5 taxa studied. With respect to the relative affinities among the species studied, the present results could resolve the discrepancies between conclusions based on morphological evidence and those based on cytological evidence. 4. The 5 species of Rattus studied may be assigned to 4 groups and comparative data suggest that these groups are relatively distantly related to one another.

Animals↗
PubMed2006

Seasonal changes in body composition of Ctenomys talarum (Rodentia: Octodontidae): an herbivore subterranean rodent.

Ctenomys talarum is a subterranean herbivorous rodent whose burrow systems exhibit particular characteristics, distinct from other subterranean environments. We studied seasonal variation in body composition of C. talarum in relation to energetic requirements. Body lipid content seasonally changed in C. talarum, related to reproductive cycle and thermorregulatory mechanisms. A decrease in protein body content was found only in spring. Ash content of females was lowest when most of them are in post partum estro. Observed variations in water body content could be associated with plant water content and/or metabolic regulation. Our results show the occurrence of seasonal variations in body composition in C. talarum, which could be related to the high cost of reproduction and the subterranean life style of this species.

Animals↗
PubMed2004

Differences in ingestive balance of two populations of neotropical Thrichomys apereoides (Rodentia, Echimyidae).

Thrichomys apereoides is widely distributed in the Caatinga, a semi-arid region in Brazil, but is presumed to lack capabilities for water conservation. In the present study, we compared two populations of adult individuals living under different precipitation conditions (700 and 450 mm year(-1)). Animals from the less dry area were twice as heavy as those from the drier locality. Under ad libitum water regimen, there were differences between populations in relative food intake as well as in water intake and urine concentration, but not in normalized body mass water intake. Under short-term water deprivation, both populations presented similar body mass loss. Whereas individuals from the more arid locality maintained food consumption, urine volume and urine osmolality, Thrichomys from the less dry locality reduced food consumption and urine volume. The occurrence of anuria in 75% of animals from this population indicates that the limits of their ability to deal with water shortage had been reached. The morphological and physiological difference and the non-allometric similarities found between the two populations of T. apereoides fulfill the criteria for physiological adaptations to differences in annual rainfall. Our data challenge the hypothesis that the irregularity of annual rainfall in the Caatinga precludes the evolution of adaptations to this semi-arid climate.

Adaptation, Physiological↗
PubMedDate not supplied

Trypanosoma cruzi in a caviomorph rodent: parasitological and pathological features of the experimental infection of Trichomys apereoides (Rodentia, Echimyidae).

To understand the interaction of Trypanosoma cruzi with caviomorph rodents, which supposedly have an ancient co-evolutionary history with this parasite, experimental infection of laboratory reared Trichomys apereoides with several isolates of both genotypes of the parasite was studied. Parasitemia, pattern of hematic cells, specific humoral immune response, histopathological features and parasite clearance were appraised. T. apereoides maintained stable infections independent of the T. cruzi genotype as demonstrated by positive PCR results in analyses of several tissues after a 5 months follow-up. The acute phase was characterized by abundant and disseminated presence of amastigotes, vacuolization and/or myocytolysis. Lymphocytosis was a common feature. The chronic phase was characterized mainly by lymphomacroeosinophilic infiltrates independent of the inoculated T. cruzi isolate. T. cruzi of different genotypes did not show any tissular preference in T. apereoides.

Animals↗
PubMed2005

Trypanosoma cruzi: distinct patterns of infection in the sibling caviomorph rodent species Thrichomys apereoides laurentius and Thrichomys pachyurus (Rodentia, Echimyidae).

Thrichomys apereoides, a caviomorph rodent species common in a highly endemic area for Chagas disease in Brazil, may act as reservoir of the parasite. However, no information is available concerning its sibling species Thrichomys pachyurus, found in the Pantanal region, where Trypanosoma cruzi is found only in the enzootic cycle. We followed up the cross infection of these cryptic species with two isolates derived from naturally infected T. pachyurus and Thrichomys apereoides laurentius. No regional co-adaptation between Thrichomys species and the regional isolates were noticed. However, significant differences in the outcome of the infection were observed. T. a. laurentius was more resistant than T. pachyurus, as expressed by lower parasitemia and less histopathological damage. The routine biochemical markers used for laboratory rodents were unsuitable for follow up of infection in Thrichomys spp, since they did not correlate with the histopathological findings or allowed the kinetic follow-up of tissue colonization by the parasite.

Alanine Transaminase↗