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 811 records · Page 45Linked to original sources
PubMed2003

Maximal aerobic performance of deer mice in combined cold and exercise challenges.

In nature, animals frequently need to deal with several physiological challenges simultaneously. We examined thermoregulatory performance (body temperature stability) and maximal oxygen consumption of deer mice (Peromyscus maniculatus) during intense exercise at room temperature, acute cold exposure, and exercise during cold exposure. Results with exercise and cold exposure alone were consistent with previous studies: there was little difference between maximal metabolism elicited by exercise alone or cold exposure alone in warm-acclimated mice; after cold acclimation (9 weeks at 5 degrees C), maximal exercise metabolism did not change but maximum thermogenic capacity increased by >60%. Warm acclimated animals did not increase maximal oxygen consumption when exercise was combined with moderate cold (0 degrees C) and had decreased maximal oxygen consumption when exercise was combined with severe cold (-16 degrees C). Combined cold and exercise also decreased thermoregulatory performance and exercise endurance time. Cold acclimation improved thermoregulatory performance in combined cold and exercise, and there was also a slight increase in endurance. However, as for warm-acclimated animals, maximal exercise metabolism did not increase at low temperatures. We interpret these results as an indication of competition between thermoregulatory and locomotor effectors (brown adipose tissue and skeletal muscle) under the combined challenges of cold exposure and maximal exercise, with priority given to the locomotor function.

Adipose Tissue, Brown↗
PubMed2005

Positive effects of testosterone and immunochallenge on energy allocation to reproductive organs.

A number of studies have suggested the incompatibility of simultaneous increases in immune and reproductive functions. Other research has indicated that immune responses may be modulated depending on the relative benefits of increased survival and prospects for current and future reproduction. We tested the hypothesis that energy allocation to reproductive and other organ systems is not affected by testosterone level and energy expenditure on immune functions. Adult male white-footed mice (Peromyscus leucopus) with or without elevated testosterone levels and with or without immunochallenges were tested. Testosterone treatment was associated with reduced humoral immune response indicating immunosuppressive effects, reduced masses of gastrointestinal organs, reduced corticosterone level, increased kidney and seminal vesicle masses, and increased hematocrit. Immunochallenge was associated with increased resting metabolic rate and testes and seminal vesicle masses. Reproductive organ masses were greatest in immunochallenged mice with exogenous testosterone. Simultaneous increases in energy allocation to immune and reproductive structures may be an adaptive response that would enhance survival and current prospects for reproduction.

Animals↗
PubMed2006

Is BMR repeatable in deer mice? Organ mass correlates and the effects of cold acclimation and natal altitude.

Basal metabolic rate (BMR) is probably the most studied aspect of energy metabolism in vertebrate endotherms. Numerous papers have explored its mass allometry, phylogenetic and ecological relationships, and ontogeny. Implicit in many of these studies (and explicit in some) is the view that BMR responds to selection, which requires repeatability and heritability. However, BMR is highly plastic in response to numerous behavioral and environmental factors and there are surprisingly few data on its repeatability. Moreover, the mechanistic underpinnings of variation in BMR are unclear, despite considerable research. We studied BMR repeatability in deer mice (Peromyscus maniculatus) across intervals of 30-60 days, and also examined the influence of birth altitude (3,800 m versus 340 m) and temperature acclimation (to approximately 5 or approximately 20 degrees C) on BMR, and the relationship between BMR and organ size. Neither acclimation temperature nor natal altitude alone influenced BMR, but the combination of birth at high altitude and cold acclimation significantly increased BMR. Few visceral organ masses were correlated to BMR and most were inconsistent across natal altitudes and acclimation temperatures, indicating that no single organ 'controls' variation in BMR. In several treatment groups, the mass of the 'running motor' (combined musculoskeletal mass) was negatively correlated to BMR and the summed mass of visceral organs was positively correlated to BMR. We found no repeatability of BMR in any treatment group. That finding-in sharp contrast to high repeatability of BMR in several other small endotherms-suggests little potential for direct selection to drive BMR evolution in deer mice.

Acclimatization↗
PubMed1997

Phenotypic variation in seasonal adjustments of testis size, body weight, and food intake in deer mice: role of pineal function and ambient temperature.

We investigated pineal function as well as reproductive and energetic characteristics in male deer mice (Peromyscus maniculatus) that differentially respond to short photoperiod with full, partial or no gonadal regression. In mice at both high (23 degrees C) and low temperature (1 degree C), these phenotypic differences in reproductive responses to short days were not reflected by differences in urinary excretion of 6-sulphatoxy-melatonin, the main metabolite of pineal melatonin. Neither duration nor amplitude or phase-angle of nocturnal peaks in 6-sulphatoxymelatonin significantly differed between reproductive phenotypes at either temperature. Differences in testis size were, however, associated with different energy requirements. In gonadally regressed males only, food intake and body weight were significantly (P < 0.01) reduced by up to 29% and 13% respectively. Chronic cold exposure (5 degrees C) had no effect on the proportion of males undergoing testicular regression under short days, but caused a general elevation in body weights among all mice (P < 0.05). Phenotypic differences in body weight and food intake were maintained in the cold. Together, these results suggest that within-population variation of reproductive responses in male deer mice is based on post-pineal differences in the regulation of gonadal function, and that phenotypic characteristics in reproductive and energetic responses to short days are largely unaffected by ambient temperature.

Animals↗
PubMed2004

Movement and spatial organization of small mammals following vertebrate predator exclusion.

Predation directly changes the demographics of prey, generally through a numerical decrease. An indirect effect of predators is alteration of movements and spatial patterns of prey. The relationship between these direct and indirect effects can be tested by excluding predators. Home range size of white-footed mice (Peromyscus leucopus) decreased and home range overlaps increased in the absence of predators. Home range size and overlaps of meadow voles (Microtus pennsylvanicus) did not change despite an increase in vole density. P. leucopus had significantly lower interspecific home range overlaps with M. pennsylvanicus than intraspecific overlaps. The changes in P. leucopus spatial behavior may be an indirect effect of predator exclusion resulting from the increase in M. pennsylvanicus densities.

Analysis of Variance↗
PubMed2004

Rodents balancing a variety of risks: invasive fire ants and indirect and direct indicators of predation risk.

We used foraging trays to compare how oldfield mice, Peromyscus polionotus, altered foraging in response to the presence of fire ants, Solenopsis invicta, and in the presence of direct (predator urine) and indirect (sheltered or exposed microhabitat, moonlight, and precipitation) indicators of predation risk. Foraging reductions elicited by S. invicta were greater than reductions in response to well-documented indicators of risk (i.e., moonlit nights) and the presence of predator urine. The presence of S. invicta always led to reduced foraging, but the overall impact of S. invicta was dependent upon microhabitat and precipitation. When S. invicta was not present, foraging was greater in sheltered microhabitats compared to exposed microhabitats. S. invicta made sheltered microhabitats equivalent to more risky exposed microhabitats, and this effect was especially pronounced on nights without precipitation. The effect of S. invicta suggests that interactions with S. invicta may entail a potentially heavy cost or that presence of S. invicta may represent a more reliable indicator of imminent competition or predation compared to indirect cues of risk and predator urine. The presence of S. invicta led to reduced foraging under situations when foraging activity would otherwise be greatest (i.show $132#e., under vegetative cover), potentially reducing habitat quality for P. polionotus and the distribution of seeds consumed by rodents.

Analysis of Variance↗
PubMed2005

Reproduction, foraging and the negative density-area relationship of a generalist rodent.

While many species show positive relationships between population density and habitat patch area, some species consistently show higher densities in smaller patches. Few studies have examined mechanisms that may cause species to have negative density-area relationships. We tested the hypothesis that greater reproduction in edge versus interior habitats and small versus large fragments contributes to higher densities of white-footed mice (Peromyscus leucopus) in small versus large forest fragments. We also examined vegetation structure and foraging tray utilization to evaluate if greater reproduction was a result of higher food availability. There were greater number of litters and proportion of females producing litters in the edge versus interior of forest fragments, which may have contributed to greater population growth rates and higher densities in edge versus interior and small versus large fragments. Data on vegetation structure and giving-up densities of seeds in artificial patches suggest that food availability may be higher in edge versus interior habitats and small versus large fragments. These results, in an area with few or no long-tailed weasels, provide a distinct contrast to the findings of Morris and Davidson (Ecology 81:2061, 2000) who observed lower reproduction in forest edge habitat as a result of high weasel predation, suggesting that specialist predators may be important in affecting the quality of edge habitat. While we cannot exclude the potential contributions of immigration, emigration, and mortality, our data suggest that greater reproduction in edge versus interior habitat is an important factor contributing to higher densities of P. leucopus in small fragments.

Analysis of Variance↗
PubMed1988

Identification of P-450ALC in microsomes from alcohol dehydrogenase-deficient deermice: contribution to ethanol elimination in vivo.

Isozyme 3a of rabbit hepatic cytochrome P-450, also termed P-450ALC, was previously isolated and characterized and was shown to be induced 3- to 5-fold by exposure to ethanol. In the present study, antibody against rabbit P-450ALC was used to identify a homologous protein in alcohol dehydrogenase-negative (ADH-) and -positive (ADH+) deermice, Peromyscus maniculatus. The antibody reacts with a single protein having an apparent molecular weight of 52,000 on immunoblots of hepatic microsomes from untreated and ethanol-treated deermice from both strains. The level of the homologous protein was about 2-fold greater in microsomes from naive ADH- than from naive ADH+ animals. Ethanol treatment induced the protein about 3-fold in the ADH+ strain and about 4-fold in the ADH- strain. The antibody to rabbit P-450ALC inhibited the microsomal metabolism of ethanol and aniline. The homologous protein, termed deermouse P-450ALC, catalyzed from 70 to 80% of the oxidation of ethanol and about 90% of the hydroxylation of aniline by microsomes from both strains after ethanol treatment. The antibody-inhibited portion of the microsomal activities, which are attributable to the P-450ALC homolog, increased about 3-fold upon ethanol treatment in the ADH+ strain and about 4-fold in the ADH- strain, in excellent agreement with the results from immunoblots. The total microsomal P-450 content and the rate of ethanol oxidation were induced 1.4-fold and 2.2-fold, respectively, by ethanol in the ADH+ strain and 1.9-fold and 3.3-fold, respectively, in the ADH- strain. Thus, the total microsomal P-450 content and ethanol oxidation underestimate the induction of the P-450ALC homolog in both strains. A comparison of the rates of microsomal ethanol oxidation in vitro with rates of ethanol elimination in vivo indicates that deermouse P-450ALC could account optimally for 3 and 8% of total ethanol elimination in naive ADH+ and ADH- strains, respectively. After chronic ethanol treatment, P-450ALC could account maximally for 8% of the total ethanol elimination in the ADH+ strain and 22% in the ADH- strain. Further, cytochrome P-450ALC appears to be responsible for about one-half of the increase in the rate of ethanol elimination in vivo after chronic treatment with ethanol. These results indicate that the contribution of P-450ALC to ethanol oxidation in the deermouse is relatively small. Desferrioxamine had no effect on rates of ethanol uptake by perfused livers from ADH-negative deermice, indicating that ethanol oxidation by a hydroxyl radical-mediated mechanism was not involved in ethanol metabolism in this mutant.(ABSTRACT TRUNCATED AT 400 WORDS)

Alcohol Dehydrogenase↗
PubMed1985

Role of alcohol dehydrogenase in the swift increase in alcohol metabolism (SIAM). Studies with deer mice deficient in alcohol dehydrogenase.

Previous studies have shown that rates of ethanol metabolism increase markedly 2-4 hr after the administration of ethanol in rats and in four inbred strains of mice. This phenomenon, called the swift increase in alcohol metabolism (SIAM), also exists in humans. To determine whether alcohol dehydrogenase (ADH) is necessary for the SIAM response, we compared ethanol metabolism in two strains of the deer mouse, Peromyscus maniculatus. One strain lacks alcohol dehydrogenase (ADH-negative), whereas the other strain has normal ADH levels (ADH-positive). Rates of ethanol elimination were determined after a single intraperitoneal injection of ethanol at different doses (0.5 to 3.0 g/kg) and also after both strains were exposed to various levels of ethanol vapor for 4 hr. The ADH-positive strain exhibited up to a 72% increase in the rate of ethanol elimination after exposure to ethanol vapor compared to the ethanol-injected controls. In contrast, treatment with ethanol vapor did not alter rates of ethanol elimination in the ADH-negative strain. These data demonstrate clearly that ADH is required for SIAM in the deer mouse. In addition, in both the ADH-positive and the ADH-negative strain, rates of ethanol elimination increased in both the ethanol-injected and vapor-treated groups 2- to 3-fold as the dose of ethanol was increased from 100 to 500 mg/100 ml. Thus, it is concluded that this "concentration effect" of ethanol on rates of ethanol metabolism does not involve ADH in the . deer mouse.

Alcohol Dehydrogenase↗
PubMed1993

Dehydrogenase-dependent metabolism of alcohols in gastric mucosa of deer mice lacking hepatic alcohol dehydrogenase.

Deer mice (Peromyscus maniculatus) lacking hepatic alcohol dehydrogenase (ADH) have been used as a model for studies of ethanol elimination catalysed by non-ADH systems like catalase and cytochrome P450. However, in an in vivo study on these animals (ADH- deer mice), we detected reversibility in the oxidation of [2H]ethanol, indicating that a major part of the ethanol elimination was due to a dehydrogenase (Norsten et al., J Biol Chem 264: 5593-5597, 1989). In the present investigation, we found significant ethanol oxidizing activity in the gastric mucosa of the deer mice. Reversibility was demonstrated by the use of [2H]acetaldehyde and gas chromatography-mass spectrometry of the products. The kinetic 2H isotope effect of the gastric system was about 3.0 and the system was comparatively insensitive to inhibition by 4-methylpyrazole. The behavior of the deer mice gastric ADH in isoelectric focusing and its higher activity with longer alcohols as substrates indicated similarity with the previously described human class IV enzymes. Our data are in agreement with results obtained in vivo and indicate that ethanol is oxidized extrahepatically in ADH- deer mice. This has to be taken into account when deer mice are used to study non-ADH-dependent ethanol oxidation in vivo.

Acetaldehyde↗
PubMed1987

Stress-induced opioid analgesia and activity in deer mice: sex and population differences.

We compared restraint stress-induced opioid, analgesic and locomotory responses of 4 different populations of male and female deer mice, Peromyscus maniculatus artemisiae and P. m. nebrascensis from mainlands, and P. m. angustus and P. m. triangularis from small islands. All of the deer mice displayed immobilization-induced analgesia which was blocked by the prototypical mu-opiate antagonist, naloxone (1.0 mg/kg). In all of the populations males displayed significantly greater levels of analgesia than females. In addition, the levels of opioid-induced analgesia were significantly greater in the insular than in the mainland male and female deer mice. Restraint also induced significant increases in the locomotor activity of the mainland deer mice, while significantly decreasing the activity of the insular animals. Males displayed significantly greater stress-induced changes in locomotor activity than did females. The stress-induced increases in activity were blocked by the delta-opiate antagonist, ICI 154, 129 (10 mg/kg), while the decreases in activity were inhibited by naloxone. These results demonstrate that there are marked sex and population differences in the stress-induced, opioid-mediated responses of deer mice. These 'pharmaco-ecological' findings also suggest that the island-mainland population differences in behavioral responses and ecological characteristics may, in part, be related to differences in the activity of mu-, delta- and possibly other opioid systems.

Animals↗
PubMed1990

Developmental changes in opiate-induced analgesia in deer mice: sex and population differences.

We examined developmental changes in nociception and mu (morphine) and kappa (U-50,488) opiate-induced analgesia in male and female deer mice of two different populations; Peromyscus maniculatus artemisiae from a mainland region and P. m. angustus from a small island. Both populations displayed significant developmental changes in nociception and morphine (10 mg/kg) and U-50,488 (10 mg/kg)-induced analgesia. Basal thermal response latencies (nociceptive responses) and the levels of mu and kappa opiate-induced analgesia increased over 14-35 days of age, with maximum analgesic responses in adults (35+ days of age). In both of the populations, young (neonatal-weaning) male mice displayed significantly higher thermal response latencies and greater levels of naloxone (1.0 mg/kg) antagonized opiate-induced analgesia than young females. There were also population differences in the levels of analgesia, the insular mice displaying greater mu and lower kappa opiate-induced analgesic responses than the mainland animals. The population differences in mu and kappa opiate-induced analgesia were evident in young and adult mice of both sexes. These results show that there are significant sex and population differences in nociception and opiate-induced analgesia in young (neonatal-weaning) and adult deer mice.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1994

Sexually dimorphic spatial learning varies seasonally in two populations of deer mice.

Spatial learning in photoperiodically induced breeding (reproductive) and non-breeding (non-reproductive) adult male and female deer mice (Peromyscus maniculatus) was examined in a Morris water-maze task. Sexually mature, adult male and female deer mice that were derived from either a mainland population (P. m. artemisiae) or an island population (P. m. angustus) were required to learn the spatial position of a hidden, submerged platform in a water maze. Deer mice were tested either during the breeding season (summer; long day photoperiod) or during the non-breeding season (winter; short day photoperiod) with a total of six blocks of four trials conducted in a single day. Retention was tested with two probe trials which occurred one and three days after acquisition. During the breeding season male spatial task acquisition was superior to female spatial task acquisition for both populations. In contrast, during the non-breeding season there were no significant sex differences in spatial acquisition for either population. This change in sexually dimorphic spatial learning was due to female spatial-performance decreasing from non-breeding season to the breeding season and male spatial-performance increasing over the same period. Both populations displayed similar seasonal variations in sexually dimorphic water-maze task performance. There were, however, overall population differences in water-maze task performance that were related to the ecology of the mice, with the insular mice displaying shorter latencies to reach the hidden platform than did the mainland deer mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Differential testicular responses to short daylength in deer mice are reflected by regional and morphological differences in the GnRH neuronal system.

Male deer mice (Peromyscus maniculatus) respond to short photoperiod with a range of spermatogenic responses. About one-third of all short day exposed mice exhibit a complete cessation of spermatogenesis (reproductive responsive), while about an equal number remain reproductively competent (reproductive nonresponsive). These differential spermatogenic responses are mirrored by endocrine measures; reproductive responsive males exhibit reduced circulating levels of testosterone and luteinizing hormone, while reproductive nonresponsive males exhibit long day levels of both hormones. A variety of evidence indicates that despite individual differences in reproductive responses, all short day exposed mice detect and respond to the change in photoperiod at the level of the hypothalamus, irrespective of gonadal response. We investigated whether deer mice exhibiting disparate gonadal responses to short days differed in aspects of the GnRH neuronal system, as revealed by immunocytochemistry. Reproductively mature males were maintained on either long (16L:8D) or short (8L:16D) photoperiod for 8 weeks. Thereafter, regional and morphological differences in GnRH-containing neurons were compared among long day (n = 8) and short day reproductive responsive (n = 8) and nonresponsive (n = 8) deer mice. Results demonstrate both an effect of photoperiod and reproductive state on the number, location and morphology of immunoreactive-GnRH neurons. Short days caused immunoreactive GnRH cell number to increase in both short day phenotypes relative to long day mice. Significant differences among treatment groups in the numbers of cells per region were confined to the lateral hypothalamus and lateral preoptic area. Both short day phenotypes exhibited an increase in cell number in the lateral preoptic area, compared to long day mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1990

Borrelia burgdorferi and Babesia microti: efficiency of transmission from reservoirs to vector ticks (Ixodes dammini).

In endemic regions, Peromyscus leucopus, the mouse reservoir of the Lyme disease spirochete (Borrelia burgdorferi) and the piroplasm causing human babesiosis (Babesia microti), is nearly universally infected with both agents. Paradoxically, spirochetal infection is nearly twice as prevalent as is babesial infection in populations of field-collected nymphal Ixodes dammini, the tick vector. In the laboratory, a similarly disproportionate rate of infection was observed among nymphal ticks, feeding as larvae, on either B. burgdorferi- or B. microti-infected mice. Ticks which fed on mice with concurrent spirochetal and babesial infections also exhibited twice the incidence of spirochetal infection over that of the piroplasm. These data suggest that the efficiency of acquisition and transstadial passage of B. burgdorferi and B. microti infection differ by a factor of two. This discrepancy may explain differences observed both in the prevalence of infection in ticks collected in the field, as well as the apparently greater risk of spirochetal infection to humans in endemic areas.

Animals↗
PubMed1984

Naloxone inhibition of stress-induced daily torpor.

Peromyscus maniculatus, deermice , were induced into daily torpor by restricting food to one-half daily ration. Intraperitoneal injection of naloxone (20 mg/kg) into mice habituated to daily IP injections of saline inhibited or modified the expression of daily torpor. In those individuals demonstrating long duration/deep bouts (greater than 300 min/body temperature 20 degrees C or below) naloxone administration resulted in 1) a significant decrease in the duration of torpor, 2) a significant elevation in minimum body temperatures attained during torpor and 3) a significant delay in the initiation time of torpor. In those individuals demonstrating short duration/shallow bouts (less than 300 min/body temperatures above 20 degrees C), naloxone administration resulted only in a significant delay of initiation time. Upon subsequent return to saline administration, however, these mice displayed a significant increase in the duration and depth of torpor. The results suggest that the endogenous opiates modulate the state of daily torpor.

Acclimatization↗
PubMed1983

Rhythms of barbiturate-induced sleep time in deermice entrained to non-twenty-four hour photocycles.

The present experiment examined whether entrainment to twenty-four hour days is advantageous for physiological and behavioral adaptations to a pharmacological challenge. Adult, male deermice (Peromyscus maniculatus) were injected with sodium pentobarbital at 8.5, 14.5, 20.5, 2.5 and again at 8.5 hr after light onset while entrained to a 24 hr day (light/dark (LD) 14:10). Time to recover from anesthesia was recorded. Subsequently, the dark phase of the LD cycle was reduced 15-20 min every 10 days until a 23 hr photocycle was achieved, (LD 14:9; T = 23 hr). Injections of sodium pentobarbital were again administered at 8.5, 14.5, 20.5 and 2.5 hr after light onset and sleep times recorded. This procedure was repeated at T = 21 hr (LD 14:7) and T = 18 hr (LD 14:4). A variation in sleep time was observed during entrainment to all T-cycles except T = 18 hr. Sleep time after drug administration was generally longer during the light than during the dark phase of each photocycle. Recovery from anesthesia was not compromised in mice entrained to photocycles with periods of 23 or 21 hr; however, entrainment to very short days disrupted the normal pattern of response to barbiturate administration. Entrainment to a range of daylengths that deviate appreciably from 24 hr is consistent with normal physiological function.

Animals↗
PubMed1985

Effects of laryngeal denervation on ultrasound production and male sexual behavior in rodents.

Adult male house mice (Mus musculus) and deer mice (Peromyscus maniculatus bairdi) were used to investigate the effects of partial denervation of the larynx on ultrasound production. In addition the masculine sexual behavior of vocalizing and muted males was assessed on tests with receptive females. For both species, unilateral transections of the inferior laryngeal nerve (ILN) significantly reduced the proportion of males that emitted ultrasonic vocalizations. However, the inability to vocalize did not prevent the display of male sexual behavior. Bilateral transections of the superior laryngeal nerve (SLN) failed to abolish ultrasound production in males of both species. These nerve transections, however, reduced the amount of ultrasound recorded during postsurgical tests, and in the case of deer mice, cuts of the SLN increased the latency to the first vocalization. The present results confirm the importance of the ILN in the neural control of ultrasonic vocalizations and indicate that, at least in laboratory tests, the ability to emit ultrasounds is not a necessary condition for the display of mating behavior in male rodents.

Animals↗