Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Peromyscus”

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 973 records · Page 54Linked to original sources
PubMed1988

Photoperiodic adjustments in hypothalamic amines, gonadotropin-releasing hormone, and beta-endorphin in the white-footed mouse.

This study was undertaken to examine short photoperiod (SD; 8 h of light, 16 h of darkness)-induced alterations in reproductive endocrine and neuroendocrine parameters in the male white-footed mouse, Peromyscus leucopus. Exposure to SD for 8 weeks caused dramatic reductions in testis and seminal vesicle weights, decreased circulating LH and testosterone levels, and lowered the content of LH in the pituitary gland relative to those in mice under long photoperiod (LD; 16 h of light, 8 h of darkness). These changes were associated with significant increases in content of radioimmunoassayable GnRH in the mediobasal hypothalamus (MBH) and anterior hypothalamus at two time points in the light/dark cycle: 2100 h (dark phase) and 0900 h (light phase), respectively. Exposure to SD also caused an increase in radioimmunoassayable beta-endorphin in the MBH and preoptic area of the hypothalamus (POA) at 2100 h, but not at 0900 h. Mice exposed to SD also had a significantly higher metabolism of serotonin in the MBH at 0900 and 2100 h compared to mice under LD. The concentration of noradrenaline in the hypothalamus was unaffected by exposure to SD. However, the metabolism of dopamine (DA) in the POA at 0900 h was significantly increased relative to that in mice maintained under LD at this time. This increase in DA metabolism was associated with enhanced immunocytochemical staining for tyrosine hydroxylase in nerve fibers of the POA. Conversely, staining for tyrosine hydroxylase in tuberoinfundibular DA cell bodies of the arcuate nucleus was less intense under SD exposure. From these data it is concluded that exposure to SD caused regional and time-dependent alterations in the activities of hypothalamic amines (serotonin and DA) and neuropeptides (beta-endorphin and GnRH). These changes may be part of the neuroendocrine mechanism for SD-induced seasonal adaptations.

Amines↗
PubMed2003

Age and aerobic performance in deer mice.

Age impacts the phenotype of all multicellular animals, but lifetime changes in physiological traits are poorly understood for all but a few species. Here, we describe a cross-sectional study of age effects on body composition, aerobic performance and ventilation in deer mice Peromyscus maniculatus. This species lives considerably longer in captivity (in excess of 5 years) than most laboratory rodents, and the adaptational biology of its aerobic physiology is well studied. Our deer mice grew throughout life, and, as is typical for mammals, their basal metabolic rate (BMR) and maximal oxygen consumption in exercise ((VO(2)max)) and thermogenesis ((VO(2)sum)) increased as power functions of mass. Age did not affect BMR, but we found abrupt decreases in growth rate, (VO(2)max) and (VO(2)sum) at approximately 485 days of age, and the mass-adjusted maximal aerobic performance of old mice (5 years of age) was 20% ((VO(2)max)) to 35% ((VO(2)sum)) less than that of young animals. Breathing frequency (f) and oxygen extraction (E(O(2))) also declined with age but did not change abruptly. However, there were no consistent age-related changes in tidal volume (V(T)) or minute volume ((Vmin)) after accounting for the effects of mass and (VO(2)sum). Age influenced several aspects of body composition (lean and fat mass). However, these changes were insufficient to explain the age-related declines in aerobic performance, suggesting that mass-specific oxidative capacity of lean tissue decreased with age. The performance changes we found could engender substantial reductions in the mobility and thermal tolerances of old deer mice. However, very few wild mice are likely to survive to ages where substantial performance decreases occur, so these declines are probably not subjected to strong selection in natural populations.

Acclimatization↗
PubMed2001

A novel mechanism of body mass regulation.

While significant attention has been devoted to the identification of hormonal factors that control body mass, little attention has been paid to the role of mechanical loading on animal mass. Here, we provide evidence that intraperitoneal implantation of metabolically inert mass results in a compensatory reduction in tissue mass. Deer mice (Peromyscus maniculatus) were surgically implanted with weights of 1, 2 or 3 g. There was a resulting loss of tissue mass (total body mass minus implant mass) that was proportional to the mass of the implant. This reduction in tissue mass followed a reduction in food intake in animals with 3 g implants. Evaluation of body composition failed to identify any single component that contributed to the loss of tissue mass. Removal of implants led to a transient restoration of body mass to levels similar to the total body mass of those control animals in which the implant had not been removed. However, within 12 days of implant removal, body mass again declined to the level seen before implant removal. These results suggest the existence of a set point that is sensitive to changes in the perception of mass and that is transduced via neural pathways.

Animals↗
PubMed2001

Effects of altitude and temperature on organ phenotypic plasticity along an altitudinal gradient.

Small mammals living in high-altitude environments must endure decreased ambient temperatures and hypoxic conditions relative to sea-level environments. Previously, it was noted that heart, lung and digestive tract masses and blood hematocrit increase along an altitudinal gradient in small mammals. Increases in digestive organ mass were attributed to lower ambient temperatures and greater food intake, and increases in lung mass and hematocrit were attributed to hypoxia, but these assumptions were not explicitly tested. In addition, it was not clear whether changes in heart and lung mass were a function of an increase in organ blood content or of an increase in organ tissue mass. We used captive deer mice (Peromyscus maniculatus sonoriensis) to determine the relative effects of ambient temperature and oxygen concentration (PO2) on organ mass and blood hematocrit along an altitudinal gradient. We also exsanguinated hearts and lungs to determine whether changes in mass were associated with the blood content or with increases in tissue mass. We found that small intestine mass was, as expected, correlated positively with energy intake and negatively with ambient temperature. Heart mass was also negatively correlated with temperature. Lung mass and hematocrit were, as expected, positively correlated with altitude (and PO2). Interestingly, the masses of both small intestine and kidney were negatively correlated with altitude. For kidney mass, this correlation was apparent in cold-exposed mice but not in warm-exposed mice. We also found that changes in both heart and lung mass were mainly a function of changes in tissue mass rather than blood content. These data show that different abiotic variables have different effects on organ masses at high altitude, but also that phenotypic plasticity in response to cold temperatures and low oxygen pressures at altitude is widespread across several different organ systems, suggesting a general elevated whole-body response.

Altitude↗
PubMed1994

Toxicological foundations of ecological risk assessment: biomarker development and interpretation based on laboratory and wildlife species.

Ecological risk assessments based on chemical residue analysis and species demographics tend to ignore the bioavailability and bioaccumulation of the chemicals of concern. This study describes the incorporation of mechanistically based biomarkers into an ecological risk assessment of a poly-cyclic aromatic hydrocarbon (PAH)-contaminated site. A combination of soil residue analysis, tissue residue analysis, biomarkers in one-site trapped animals and biomarkers in animals confined to enclosures was used. In particular, the use of captured deer mice (Peromyscus maniculatus) for these studies is compared to the use of laboratory-raised deer mice placed in enclosures. This study indicates that the higher degree of variability in the responses of wild deer mice make the use of enclosure studies advantageous. Positive control studies performed by dosing laboratory-raised deer mice with the same PAHs as found on the site were used to validate this approach. These studies indicate that immune suppression occurred at PAH concentrations an order of magnitude below those required for the induction of ethoxyresorufin-O-dealkylase activity.

Animals↗
PubMed2006

Climate, deer, rodents, and acorns as determinants of variation in lyme-disease risk.

Risk of human exposure to vector-borne zoonotic pathogens is a function of the abundance and infection prevalence of vectors. We assessed the determinants of Lyme-disease risk (density and Borrelia burgdorferi-infection prevalence of nymphal Ixodes scapularis ticks) over 13 y on several field plots within eastern deciduous forests in the epicenter of US Lyme disease (Dutchess County, New York). We used a model comparison approach to simultaneously test the importance of ambient growing-season temperature, precipitation, two indices of deer (Odocoileus virginianus) abundance, and densities of white-footed mice (Peromyscus leucopus), eastern chipmunks (Tamias striatus), and acorns (Quercus spp.), in both simple and multiple regression models, in predicting entomological risk. Indices of deer abundance had no predictive power, and precipitation in the current year and temperature in the prior year had only weak effects on entomological risk. The strongest predictors of a current year's risk were the prior year's abundance of mice and chipmunks and abundance of acorns 2 y previously. In no case did inclusion of deer or climate variables improve the predictive power of models based on rodents, acorns, or both. We conclude that interannual variation in entomological risk of exposure to Lyme disease is correlated positively with prior abundance of key hosts for the immature stages of the tick vector and with critical food resources for those hosts.

Animals↗
PubMed2000

A comparative study of mammalian and reptilian alternative pathway of complement-mediated killing of the Lyme disease spirochete (Borrelia burgdorferi).

The potential bactericidal activity of the alternative complement pathway of mammalian and reptilian sera to Borrelia burgdorferi sensu stricto (s.s.) was evaluated in vitro. Complement-mediated killing was observed when cultured spirochetes were inoculated into sera from the western fence lizard (Sceloporus occidentalis) and from the southern alligator lizard (Elgaria multicarinata), but not when they were inoculated into serum from either the deer mouse (Peromyscus maniculatus) or from humans. Spirochetes were still alive after 4 hr in lizard serum that had been preheated at 56 C for 30 min to inactivate complement. Furthermore, when lizard serum was chelated with 10 mM ethylenediaminetetraacetic acid to block all complement activation, borreliacidal activity was arrested. When lizard serum was chelated with 10 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid plus 4 mM MgCl2 to block only classical complement pathway activation, >85% of spirochetes were immobilized within 1 hr. Differences in B. burgdorferi s.s. mortality were not observed when chelators with or without MgCl2 were added to serum from either deer mice or humans. Proteins comprising the alternative complement pathway are responsible for the borreliacidal activity observed in the blood of S. occidentalis and E. multicarinata.

Animals↗
PubMed2001

Phylogenetic position of Eimeria antrozoi, a bat coccidium (Apicomplexa: Eimeriidae) and its relationship to morphologically similar Eimeria spp. from bats and rodents based on nuclear 18S and plastid 23S rDNA sequences.

Partial plastid 23S and nuclear 18S rDNA genes were amplified and sequenced from 2 morphologically similar Eimeria species. E. antrozoi from a bat (Antrozous pallidus) and E. arizonensis from deer mice (Peromyscus spp.), as well as some other Eimeria species from bats and rodents. The phylogenetic trees clearly separated E. antrozoi from E. arizonensis. The phylogenies based on plastid 23S rDNA data and combined data of both plastid and nuclear genes grouped 2 bat Eimeria and 3 morphologically similar Eimeria species from rodents into 2 separate clades with high bootstrap support (100%, 3 rodent Eimeria species; 72-97%, 2 bat Eimeria species), which supports E. antrozoi as a valid species. The rodent Eimeria species did not form a monophyletic group. The 2 bat Eimeria species formed a clade with the 3 morphologically similar rodent Eimeria species (E. arizonensis, E. albigulae, E. onychomysis, all from cricetid rodents) with 100% bootstrap support, whereas 2 other rodent Eimeria species (E. nieschulzi, E. falciformis, from murid rodents) formed a separate clade with 100% bootstrap support. This suggests that the 2 Eimeria species from bats might be derived from rodent Eimeria species and may have arisen as a result of lateral host transfer between rodent and bat hosts.

Animals↗
PubMed2004

Life-history studies on two molecular strains of mesocestoides (Cestoda: Mesocestoididae): identification of sylvatic hosts and infectivity of immature life stages.

Life-cycle studies were conducted on 2 molecular strains of Mesocestoides tapeworms that represent different evolutionary lineages (clades A and B). Wild carnivores, reptiles, and rodents were examined for tapeworm infections at 2 enzootic sites: (1) San Miguel Island (SMI), a small island off the coast of southern California and (2) Hopland Research and Extension Center (HREC), a field station in northern California. Results indicate that deer mice (Peromyscus maniculatus) and coyotes (Canis latrans) may play an important role in the life cycles of Mesocestoides (clades A and B) in California. Over half the coyotes at HREC and at least a third of the population of island fox (Urocyon littoralis) at SMI were found to harbor clade A adult Mesocestoides spp. One of every 4 Mesocestoides-infected coyotes had tapeworms representing both clades A and B. Experimental inoculations revealed that proglottids (clades A and B) were not directly infectious to rodents, reptiles, or dogs. On the other hand, mice, lizards, and hamsters fed tetrathyridia of Mesocestoides spp. (clades A or B) developed peritoneal tetrathyridial infections. A dog that was fed tetrathyridia (clade B) developed an adult tapeworm infection. Acephalic metacestodes given orally to western fence lizards, laboratory mice, or domestic dogs did not result in metacestode or adult tapeworm infections. Whereas most clade A acephalic metacestodes from dogs were asexually proliferative, clade A tetrathyridia isolated from wild deer mice did not show evidence of asexual replication. Our study supports the hypothesis that a second, as of yet unidentified, intermediate host is necessary to complete the life cycles of Mesocestoides spp., and that acephalic metacestodes represent an aberrant form, incapable of further development.

Animals↗
PubMed2003

Bacteriolytic activity of selected vertebrate sera for Borrelia burgdorferi sensu stricto and Borrelia bissettii.

An in vitro assay to evaluate the bacteriolytic activity of the complement pathway was applied to 2 strains of Borrelia bissettii, CO501 and DN127, and compared with that of B. burgdorferi sensu stricto B31. Sera from mule deer (Odocoileus hemionus) and the Western Fence lizard (Sceloporus occidentalis) were completely borreliacidal for B. burgdorferi and for both strains of B. bissettii. Serum from Bobwhite quail (Colinus virginianus) was nonlytic for B. burgdorferi and partially lytic for B. bissettii strains, CO-501 and DN127. Serum from a New Zealand White rabbit (Oryctolagus cuniculus) was partially lytic for all 3 strains of Borrelia, whereas serum from white-footed mice (Peromyscus leucopus) were nonlytic for all 3 Borrelia strains. The spectrum of complement sensitivity of B. bissettii appears to be similar to that of European B. afzelii in that tested rodent serum is not lytic to these 2 genospecies. Interestingly, both B. bissettii and B. afzelii have been found to be closely associated with rodents. Complement sensitivity demonstrated in these experiments may suggest and possibly predict specific reservoir-host associations.

Animals↗
PubMed2004

Ectoparasites and other epifaunistic arthropods of sympatric cotton mice and golden mice: comparisons and implications for vector-borne zoonotic diseases.

Ectoparasite and epifaunistic arthropod biodiversity and infestation parameters were compared between 2 sympatric small rodent species, the cotton mouse (Peromyscus gossypinus (Le Conte)) and golden mouse (Ochrotomys nuttalli (Harlan)), in southern Georgia from 1992 to 2003. Because the cotton mouse is known to be a reservoir of more vector-borne zoonotic pathogens than the golden mouse, we hypothesized that it would be parasitized by more ectoparasites that are known to be vectors of these pathogens. Cotton mice (n = 202) were parasitized by 19 species of arthropods, whereas golden mice (n = 46) were parasitized by 12 species. Eleven species of arthropods were recovered from both host species, whereas 7 were recorded only from cotton mice, and 1 species only from golden mice. Infestation prevalences (percent of mice parasitized) were significantly higher for 1 species of arthropod (the tropical rat mite Ornithonyssus bacoti (Hirst)) infesting cotton mice and for 4 species (the flea Peromyscopsylla scotti Fox and the mites Glycyphagus hypudaei Koch, Androlaelaps casalis (Berlese), and Androlaelaps fahrenholzi (Berlese)) infesting golden mice. Mean intensities (mean per infested mouse) were significantly higher for 2 species (the flea Orchopeas leucopus (Baker) and the blacklegged tick Ixodes scapularis Say) infesting cotton mice and for 2 species (G. hypudaei and A. fahrenholzi) infesting golden mice. Ectoparasites that are known to be vectors of zoonotic pathogens were significantly more common on cotton mice than on golden mice. These ectoparasites included the rhopalopsyllid flea Polygenis gwyni (Fox), a vector of the agent of murine typhus; I. scapularis, the principal vector of the agents of Lyme borreliosis, human granulocytic ehrlichiosis, and human babesiosis; and O. bacoti, a laboratory vector of several zoonotic pathogens. However, 2 species of ixodid ticks that can transmit zoonotic pathogens were recovered from both host species. These were the American dog tick Dermacentor variabilis (Say), the principal vector of the agent of Rocky Mountain spotted fever in eastern North America, and Ixodes minor Neumann, an enzootic vector of the agent of Lyme borreliosis. Overall, the cotton mouse was parasitized by significantly more ectoparasites that are known to be vectors of zoonotic pathogens than was the golden mouse. These data support the hypothesis that the cotton mouse has greater epidemiological importance for zoonotic vector-borne pathogen transmission than does the golden mouse.

Animals↗
PubMed2005

A new dicrocoeliid (Digenea: Dicrocoeliinae) parasite of rodents from Tlaxcala, Mexico.

Caballerolecythus ibunami n. gen., n. sp. is described from the intestine of 2 species of rodents (Liomys irroratus [Gray, 1868] and Peromyscus difficilis [Allen, 1891]) from Piñonal, El Carmen Tequexquitla, Tlaxcala state, Mexico. These specimens represent a new genus and a new species of Dicrocoeliinae by possession of an extremely short ceca (ending at equatorial level of ovary); vitelline follicles that begin posterior to these structures, without overlapping; and a body that is long and slender (length/width ratio 1:17-21). To the best of our knowledge, this combination of characters has not been reported in other genera of this subfamily (Athesmia Looss, 1899; Unilaterilecithum Oshmarin in Skrjabin and Evranova, 1952; and Pseudathesmia Travassos, 1942).

Animals↗
PubMed2006

Refractoriness of the western fence lizard (Sceloporus occidentalis) to the Lyme disease group spirochete Borrelia bissettii.

The western fence lizard, Sceloporus occidentalis, is refractory to experimental infection with Borrelia burgdorferi sensu stricto, one of several Lyme disease spirochetes pathogenic for humans. Another member of the Lyme disease spirochete complex, Borrelia bissettii, is distributed widely throughout North America and a similar, if not identical, spirochete has been implicated as a human pathogen in southern Europe. To determine the susceptibility of S. occidentalis to B. bissettii, 6 naïve lizards were exposed to the feeding activities of Ixodes pacificus nymphs experimentally infected with this spirochete. None of the lizards developed spirochetemias detectable by polymerase chain reaction for up to 8 wk post-tick feeding, infected nymphs apparently lost their B. bissettii infections within 1-2 wk after engorgement, and xenodiagnostic L. pacificus larvae that co-fed alongside infected nymphs did not acquire and maintain spirochetes. In contrast, 3 of 4 naïve deer mice (Peromyscus maniculatus) exposed similarly to feeding by 1 or more B. bissettii-infected nymphs developed patent infections within 4 wk. These and previous findings suggest that the complement system of S. occidentalis typically destroys B. burgdorferi sensu lato spirochetes present in tissues of attached and feeding I. pacificus nymphs, thereby potentially reducing the probability of transmission of these bacteria to humans or other animals by the resultant adult ticks.

Animals↗
PubMed2004

Effects of trichloroethylene and perchloroethylene on wild rodents at Edwards Air Force Base, California, USA.

Effects of inhalation of volatilized trichloroethylene (TCE) or perchloroethylene (PCE) were assessed based on the health and population size of wild, burrowing mammals at Edwards Air Force Base (CA, USA). Organic soil-vapor concentrations were measured at three sites with aquifer contamination of TCE or PCE of 5.5 to 77 mg/L and at two uncontaminated reference sites. Population estimates of kangaroo rats (Dipodomys merriami and D. panamintinus) as well as hematology, blood chemistry, and histopathology of kangaroo rats and deer mice (Peromyscus maniculatus) were compared between contaminated and uncontaminated populations. Maximum soil-gas concentrations associated with groundwater contamination were less than 1.5 microl/L of TCE and 0.07 microl/L of PCE. Population estimates of kangaroo rats were similar at contaminated and reference sites. Hematology, blood chemistry, and histopathology of kangaroo rats and deer mice indicated no evidence of health effects caused by exposure. Trichloroethylene or PCE in groundwater and in related soil gas did not appear to reduce the size of small mammal populations or impair the health of individuals.

Animals↗
PubMed2005

Hepatic porphyria induced by the herbicide tralkoxydim in small mammals is species-specific.

Tralkoxydim is the active ingredient in a postemergent herbicide used in cereal crops. During preregistration trials, tralkoxydim was observed to cause hepatic porphyria and cholestasis in laboratory mice. Porphyria was not seen in similarly exposed rats or hamsters, but data were not collected regarding the susceptibility of any wild small mammal species to the tralkoxydim-induced porphyria. To address this data gap, we exposed small mammals to tralkoxydim, to 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC; a known porphyrinogenic chemical), or to sunflower oil alone. We studied small mammal species that might be exposed following agricultural applications of the herbicide, including the white-footed mouse (Peromyscus leucopus), the deer mouse (P. maniculatus), and the meadow vole (Microtus pennsylvanicus). Because of their known susceptibility to both tralkoxydim- and DDC-induced porphyria, commercially supplied Mus musculus (CD-1 Swiss mice) were exposed as positive-control animals. We also exposed offspring of wild-caught M. musculus to compare their responses to those of the commercially supplied animals. Potential hepatotoxicity was determined by assessing the accumulation of liver protoporphyrin. Of the species tested, only M. musculus was susceptible to the porphyrinogenic action of tralkoxydim, and no significant accumulation of protoporphyrin was observed in any of the other species exposed to the herbicide.

Animals↗
PubMed2006

Thyroid function and reproductive success in rodents exposed to perchlorate via food and water.

The purpose of the present study was to determine if exposure to perchlorate via food items would have effects on mammals similar to those caused by exposure through drinking water at approximately equivalent doses. Prairie voles (Microtus ochrogaster) and deer mice (Peromyscus maniculatus) were used to assess the potential toxicity of perchlorate-contaminated food items. Voles and mice were divided randomly into three treatment groups--perchlorate-contaminated food (PCF), perchlorate-contaminated water (PCW), and control groups--such that each treatment group contained equal numbers of males and females. Rodents in PCF treatment groups were fed chow formulated with soybean plant matter that had been grown with perchlorate-contaminated irrigation water. Individuals in the control and PCF groups were provided distilled/deionized drinking water, whereas the PCW group received drinking water containing sodium perchlorate. Only slight differences among treatment groups were observed in a variety of endpoints, including reproductive success, tissue perchlorate concentrations, thyroid hormone concentrations, and thyroid histology. However, trends observed in the present study suggest that perchlorate exposure via water may result in slightly greater effects than exposure to perchlorate via food. These data and recent reports of perchlorate in a wide variety of food items indicate that exposure via food intake is an important consideration when examining cumulative risk among humans, livestock, and wildlife.

Animal Feed↗
PubMedDate not supplied

Seroepidemiologic studies of hantavirus infection among wild rodents in California.

A total of 4,626 mammals were serologically tested for antibodies to Sin Nombre virus. All nonrodent species were antibody negative. Among wild rodents, antibody prevalence was 8.5% in murids, 1.4% in heteromyids, and < 0.1% in sciurids. Of 1,921 Peromyscus maniculatus (deer mice), 226 (11.8%) were antibody positive, including one collected in 1975. The highest antibody prevalence (71.4% of 35) was found among P. maniculatus on Santa Cruz Island, off the southern California coast. Prevalence of antibodies among deer mice trapped near sites of human cases (26.8% of 164) was significantly higher than that of mice from other sites (odds ratio = 4.5; 95% confidence interval = 1.7, 11.6). Antibody prevalence increased with rising elevation (> 1,200 meters) and correlated with a spatial cluster of hantavirus pulmonary syndrome cases in the Sierra Nevada.

Animals↗
PubMedDate not supplied

Long-term hantavirus persistence in rodent populations in central Arizona.

For 35 months, we monitored hantavirus activity in rodent populations in central Arizona. The most frequently captured hantavirus antibody-positive rodents were Peromyscus boylii and P. truei. Antibody-positive P. boylii were more frequently male (84%), older, and heavier, and they survived longer on trapping web sites than antibody-negative mice. The number of antibody-positive P. boylii was greater during high population densities than during low densities, while antibody prevalence was greater during low population densities. Virus transmission and incidence rates, also related to population densities, varied by trapping site. The spatial distribution of antibody-positive P. boylii varied by population density and reflected the species preference for dense chaparral habitats. The focal ranges of antibody-positive P. boylii also demonstrated a patchy distribution of hantavirus.

Animals↗