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 163 records · Page 9Linked to original sources
PubMed2003

Biochemical and physiological validation of a corticosteroid radioimmunoassay for plasma and fecal samples in oldfield mice (Peromyscus polionotus).

The measurement of fecal steroids provides an increasingly important noninvasive technique for assessing reproduction, environmental stress, and aggression in populations of captive and free-living animals. In this paper, we validated the corticosterone (CORT) 125I-radioimmunoassay (ICN Pharmaceuticals) for plasma and fecal samples in a small rodent species, the oldfield mouse (Peromyscus polionotus subgriseus). The biochemical validations indicated that the assays accurately measured CORT concentrations in the plasma and corticosteroid concentrations in the feces. Physiological validation demonstrated that: (1) blood samples collected within 3 min of disturbing an animal's cage represented "baseline" CORT concentrations, and (2) fecal corticosteroid concentrations collected over a 24-h period closely tracked plasma CORT concentrations approximately 4 h earlier. These results demonstrate that the plasma CORT and fecal corticosteroid assays are sensitive enough to detect biologically meaningful alterations in corticosteroid concentrations in oldfield mice.

Adrenal Cortex Hormones↗
PubMed2005

Corticosteroids as potential mechanism regulating variability in reproductive success in monogamous oldfield mice (Peromyscus polionotus).

Male and female mammals undergo profound hormonal changes during pregnancy, some of which are sufficiently dramatic to influence offspring survival. In order to understand the proximate mechanisms regulating the variability in reproductive success within and between individuals, we monitored changes in fecal corticosteroid concentrations over the reproductive cycle in male and female oldfield mice (Peromyscus polionotus subgriseus) to test whether corticosteroid concentrations during pregnancy were associated with offspring survival. In females that successfully raised litters to weaning, fecal corticosteroid concentrations were low until mid-gestation and increased significantly towards term; in females that did not raise their pups to weaning, fecal corticosteroid concentrations were significantly higher at mid-gestation, and remained high until late gestation. The difference in fecal corticosteroid concentrations at mid-gestation between successful and unsuccessful females can be explained by the fact that successful females were lactating. Lactation has been associated with a down-regulation of the hypothalamic-pituitary-adrenal (HPA) axis and, accordingly, a decrease in plasma corticosterone (CORT) in several species, including humans. Males that successfully raised their litters had low fecal corticosteroid concentrations throughout their partner's pregnancy. Unsuccessful males, however, had significantly higher fecal corticosteroid concentrations at term than males that raised their pups to weaning. While these preliminary data require further investigation, we suggest that pre-partum fecal corticosteroid concentrations in males were responsible for the variability in reproductive success.

Adrenal Cortex Hormones↗
PubMed2006

Prolonged separation delays wound healing in monogamous California mice, Peromyscus californicus, but not in polygynous white-footed mice, P. leucopus.

Social interactions are often stressful, but under certain circumstances, they may be beneficial for health and well-being. In a previous study, wound healing was slowed after mate separation (2 days) in monogamous California mice, Peromyscus californicus, but not polygynous white-footed mice, P. leucopus. Although these results indicate that positive social interaction is critical for immune activity in some species, the extent to which such social effects are enduring remains unspecified. The goal of the present experiments was to determine whether a period representing approximately 20% of expected adult lifespan of these species in the wild (8 weeks) would affect wound healing. Because our experimental design required that the same animals were wounded twice, we were also able to determine the extent to which wound healing is repeatable. Wound healing remained delayed after 8 weeks of separation in P. californicus, and healing scores were not correlated between first and second wounds within individuals. In P. leucopus however, housing conditions did not influence wound healing, but first and second wound healings were correlated indicating repeatability. In sum, our results suggest that positive social interactions may be important for promoting immune activity in some species.

Animals↗
PubMed2005

Replication and immunoactivity of the recombinant Peromyscus maniculatus cytomegalovirus expressing hantavirus G1 glycoprotein in vivo and in vitro.

Previously, we have shown that CMV isolated from deer mouse could be used in vivo and in vitro to express Sin Nombre virus (SNV) glycoprotein G1 in deer mice [Rizvanov AA, van Geelen AG, Morzunov S, et al. Generation of a recombinant cytomegalovirus for expression of a hantavirus glycoprotein. J.Virol. 2003;77(22):12203-10]. In this report, we further characterize replication of wild-type (wt) and recombinant Peromyscus CMV (PCMV) in vivo and in vitro using realtime PCR, and infectious center assays. Our findings indicate that both wt PCMV and recombinant PCMV establish persistent infections in P. maniculatus. In addition, we demonstrated that gamma irradiation of PCMV infected mice resulted in reactivation of recombinant PCMV in persistently infected mice.

Animals↗
PubMed2004

Effect of neonatal handling and paternal care on offspring cognitive development in the monogamous California mouse (Peromyscus californicus).

In the laboratory rat and mouse, neonatal handling enhances hippocampal-dependent learning in adulthood, an effect mediated by changes in maternal behavior toward the handled young. In the present study, we examined the interaction between neonatal handling and biparental care during the early postnatal period and its effect on cognitive function in adult California mice (Peromyscus californicus). We characterized the parental behavior of handled and nonhandled father-present and father-absent families over the first 15 days of life. We then assessed cognitive performance of male and female offspring in the Barnes maze and object recognition test after they were 60 days of age. We found that the amount of licking and grooming received by pups was decreased in father-absent families. By postnatal days 12-15, licking and grooming in handled, father-absent families were equivalent to that of nonhandled, father-present families. Handling enhanced novel object recognition in father-present male mice with no effect in females. In the nonhandled group, the presence of the father had no effect on object recognition learning in male or female mice. Handling also enhanced spatial learning in the Barnes maze. In nonhandled families, the presence of the father appeared to have no effect on spatial learning in the male offspring. Interestingly, spatial learning in nonhandled, father-absent, female offspring was similar to that of handled animals. The average amount of licking and grooming received by pups was negatively correlated with the average number of errors made on the first day of reversal training in the Barnes maze. These data support previous findings that neonatal handling facilitates learning and memory in adulthood, suggest that under certain environmental conditions, there is a sex difference in the response of pups to paternal care, and further demonstrate the importance of active parental investment for offspring cognitive development.

Animals↗
PubMed2004

Microsatellite variation and evolution in the Peromyscus maniculatus species group.

Variation at 12 pure-repeat dinucleotide microsatellites from Peromyscus maniculatus was analyzed for samples of all species in the P. maniculatus species group and P. leucopus. Except for one locus (Pml08) that amplified a product only for P. maniculatus, these microsatellites yielded reliable estimates of variation across these species; per-locus polymorphism and allele-size distribution were not significantly different among or between any of the species sampled from mainland populations. Significantly lower levels of variation and the distribution of alleles in the two populations of the insular-endemic P. sejugis were consistent with the expectation of substantial founder effect and suggest a lack of recent gene flow between these populations. Phenetic analyses of genetic distances based on shared allele frequencies uniformly produced well-supported trees that were entirely concordant with the a priori corroborated relationships within the P. maniculatus species group; this result was not obtained with analyses of a genetic distance computed from differences in allele sizes. The microsatellite data do not support the hypothesis that P. sejugis should be considered conspecific with P. maniculatus but yield a strongly supported sister-group association between P. sejugis and P. keeni.

Animals↗
PubMed1998

Immunohistochemical demonstration of serotonin-containing axons in the hypothalamus of the white-footed mouse, Peromyscus leucopus.

The wild white-footed mouse, Peromyscus leucopus, is commonly used for photoperiod studies utilizing physiological, behavioral, and other biological measures indicative of hypothalamic functions. Indoleamines, like melatonin and serotonin, are implicated in regulating these hypothalamic functions. Although neurochemical analyses of hypothalamic serotonin and its receptors have been reported for this species, the relevant neuroanatomy of the serotonin system within mouse hypothalamus has not been studied. A sensitive immunohistochemical method was used to detect serotonin within axons of coronal sections of formaldehyde fixed forebrain from P. leucopus. Large, medium and small diameter serotonin axons were evaluated in most regions, or nuclei, of the hypothalamus rostral to the mammillary region. A fourth type of serotonin axon was observed to have morphology characteristic of terminal arbors. The density of serotonin axons ranged from no staining to very high density similar to other species for which reports exist, i.e., rat, cat, and monkey. The ventromedial hypothalamic nucleus had distinctively lesser density of serotonin axons in this mouse than other species. Evidence of terminal arborization in hypothalamic nuclei and regions was evident. Neuroendocrine, autonomic, and behavioral functions of the hypothalamus are suggested to be regulated by input from serotonin terminals in this wild species of mouse, in correlation with receptor localization as reported by others.

Animals↗
PubMed2002

Adrenal gland differences associated with puberty and reproductive inhibition in Peromyscus maniculatus.

Laboratory populations of the prairie deermouse (Peromyscus maniculatus) reach a growth asymptote due primarily to the failure of more than 90% of the young born into the population to mature sexually. This inhibition is reversible; when young are removed from the inhibiting influence of the population more than 75% will reproduce within 80 days of pairing. Interestingly, the mechanism of this inhibition does not involve the degree of adrenal hypertrophy as reported in rats and housemice. We report here that the adrenal morphology of reproductively inhibited deermice raised within laboratory populations is different from patterns seen with normal puberty; namely in the area, histology, and apparent activity of the weak androgen-secreting zona reticularis. Our data indicate that the frequency of adrenal cortex cellular apoptosis is not different between the adrenal zones or between reproductively capable versus inhibited animals and therefore does not account for the differences in the numbers of cells with pycnotic nuclei in the zona reticularis of inhibited animals. We also found that the concentration of serum DHEA is significantly reduced in reproductively inhibited animals suggesting that the zona reticularis of inhibited animals may be less active than in controls. We present data to indicate that the adrenal zona reticularis of 30-day-old control animals is likely to be more active than reproductively inhibited animals of the same age. Our data also indicate that older reproductively inhibited animals of both sexes are also likely to have a much less active zona reticularis. These differences may be implicated in the mechanism of reproductive inhibition.

Adrenal Cortex↗
PubMed2003

The progesterone challenge: steroid hormone changes following a simulated territorial intrusion in female Peromyscus californicus.

There is a growing body of evidence that the rapid but transient increase in male androgens, particularly testosterone (T), following a single social encounter such as a territorial intrusion occurs in a wide array of vertebrate taxa. Yet, this phenomenon, often called the Challenge Hypothesis, has rarely been investigated in females. Moreover, when studying male challenge effects, researchers have rarely investigated other hormones that can be important to the expression of aggression, such as progesterone (P4) and estradiol (E2). We conducted 10-min aggression trials using the resident-intruder paradigm in cycling female California mice, Peromyscus californicus, a species in which both sexes show territorial behavior. By comparing the hormone levels of test females to control females, we found a decrease in P(4) and the P4/T ratio, but no change in T, E2, corticosterone, E2/P4, or E2/T. Interestingly, these hormone changes were observed even when the resident was not aggressive toward the intruder, suggesting that the stimulus cueing the hormone changes was the mere presence of the intruder and not the amount of aggression displayed by the resident. Generally, T has a positive relationship with aggression, whereas P4 inhibits male and nonmaternal female aggression. Thus, decreasing the P4/T ratio following an encounter may serve to increase future aggression in females. These results suggest that females may use different hormonal mechanisms than do males to mediate aggression in a challenge situation.

Aggression↗
PubMedDate not supplied

Sex differences in conditioned taste aversion and in the effects of exposure to a specific pulsed magnetic field in deer mice Peromyscus maniculatus.

Although conditioned taste aversion (CTA) has been investigated and described in laboratory rodents and domestic animals, less is known regarding wild rodents. Here, we describe CTA in males and females of a "wild" species of rodent, the deer mouse (Peromyscus maniculatus). In addition, as CTA has often been induced by exposure to intense electromagnetic, X or gamma, radiation, in a second study, we also investigated the effects of a specifically designed, pulsed extremely low-frequency and low-intensity magnetic field on the flavor preferences of male and female deer mice. The results of these investigations showed that: (i) deer mice quickly developed a marked CTA for a novel flavor after a single pairing with LiCl; (ii) although the intensity of the CTA was the same in males and females, there was a sex difference in the duration of the flavor aversion, with males displaying it for a longer period (4 days) than females (3 days); (iii) both males and females showed a rapid and complete extinction of the aversion, in contrast to what has been reported for laboratory rodents; (iv) there was no recovery of CTA on re-test 10 days after extinction; (v) neither male or female deer mice developed a taste aversion as a consequence of exposure to a weak electromagnetic field; and (vi) there was a sex difference in response to the magnetic field, with exposure to the magnetic field significantly enhancing novel taste preference in male but not in female deer mice. Overall, our results show that there are several sex differences in the behavior of deer mice, both in the characteristics of the CTA and in the response to magnetic field exposure. The sex differences are discussed in terms of a sexually dimorphic sensitivity to experimental manipulation and the induction of stress and/or anxiety.

Animals↗
PubMed1997

Metabolic fuel availability influences thermoregulation in deer mice (Peromyscus maniculatus).

Body temperature (Tb) was monitored telemetrically in adult deer mice kept in an environmental chamber at low ambient temperature (Ta = 15 degrees C). Mice were challenged with various doses of 2-deoxy-D-glucose (2DG, a glycolysis inhibitor) or mercaptoacetate (MA, a fatty acid oxidation inhibitor) or a combination of the two drugs. A preliminary study suggested that higher doses of 2DG and MA, either individually or together, tended to produce a transient decrease in Tb. In the main experiment, either 2DG or MA or the two drugs together was sufficient to induce a significant, temporary hypothermia. In neither experiment, however, did any treatment affect 24-h food intake or induce daily torpor. The latter outcome contrasts with Siberian hamsters, in which torpor is readily triggered by similar 2DG treatments. Apparently, glucoprivation and lipoprivation resulting from 2DG and MA treatments, respectively, sufficient to produce significant hypothermia, are inadequate to instigate torpor in Peromyscus.

Animals↗
PubMed1997

The effects of photoperiod and food intake on reproductive development in male deer mice (Peromyscus maniculatus).

Seasonal breeding is a tactic that has evolved in rodents that limits reproduction to specific times of the year to increase reproductive success. In order to time breeding accurately, many animals respond to changes in daily photoperiod. Short day lengths inhibit breeding in many nontropical rodent species. Restricted food availability can also inhibit reproductive function among some individuals in these so-called "photoperiodic" populations. Rodents born at the end of the breeding season typically delay sexual maturation until the following spring. Prepubertal rodents exposed to day lengths that are < 12 h light/day will not undergo puberty for 4-7 months in the laboratory. Food restriction can also affect the timing of puberty onset. Reproductive function of food-restricted juvenile mice may remain inhibited until food availability improves. Alternatively, reproductive function of food-restricted juvenile mice might eventually develop despite restricted food intake. This study examined the effects of chronic food restriction and photoperiod on reproductive development in male deer mice (Peromyscus maniculatus bairdii). Short-day mice fed ad lib delayed gonadal development for 5-7 months, but eventually achieved reproductive maturity. The reproductive function of short-day mice fed ad lib was indistinguishable from long-day control animals when assessed at week 32. Long-day food-restricted mice exhibited an intermediate level of gonadal development and function. Short-day food-restricted deer mice also inhibited reproductive growth, but failed to demonstrate reproductive maturity by week 32 of the study. Taken together, these results suggest that retardation of reproductive development by food restriction is only superficially similar to the delay in reproductive maturation imposed by short day exposure. It does not appear that male deer mice escape from the inhibitory effects of food restriction to attain sexual development.

Animals↗
PubMed2003

Testicular histopathology in deer mice (Peromyscus maniculatus) following exposure to polychlorinated biphenyl.

Adult deer mice testes were subjected to routine histopathology following exposure to Aroclor 1254 supplemented diet (5 ppm), for 30 days. Body and testicular weight revealed no statistical significance between the control and treated animals. From a histological standpoint the testes of the controls were similar to normal murids and other animals. In contrast, the testes from treated animals displayed seminiferous tubules with significant degenerative alterations. These alterations included fewer layers of seminiferous epithelium exaggerated intercellular spaces and appearance of pyknotic nuclei. Most tubules displayed subluminal nuclei that morphologically could be identified as part of spermatozoa heads and these usually lacked tails, indicating that the treatment interfered with spermiogenesis. Therefore, we concluded that Aroclor 1254 as an environmental contaminant is highly destructive to seminiferous tubules, and that these histological alterations undoubtedly are responsible for the depressed fertility in Peromyscus following chronic exposure to PCBs, that has been reported in the literature.

Administration, Oral↗
PubMed1997

Age and temperature related changes in behavioral and physiological performance in the Peromyscus leucopus mouse.

Age-related and ambient temperature-related changes in motor activity, body temperature, body weight (b.w.), and food consumption were studied in the long-lived Peromyscus leucopus mouse at environmental temperatures of 29 and 21 degrees C. Major changes in physiological performance were observed between the young (6 months) and old (60-72 month) age groups. The number of daily activity episodes, and total activity output was significantly lower in old mice. Maximum, average and minimum daily body temperature was lower in the old mice and a significant ambient temperature-by-age interaction was found. Maximum, minimum, and average daily b.w. was higher in old mice. Motor activity was evenly distributed over the active (night) phase in young mice but in old mice activity was significantly greater in the late night partition of the active cycle than in the early night partition. Both groups were significantly more active at night than during the day. Most of the food consumption in both groups occurred at night, but young mice consumed significantly more during the late night partition than the early night partition, and the consumption rates for old mice were not significantly different between early and late night partitions. The percentage of activity episodes involved with food consumption in both groups was significantly higher during the night partition, but the percentage during the early night partition was significantly higher in old mice than in young mice. Significant episodes of circadian torpor occurred in a high percentage of old mice at 06:00, on consecutive days, at both environmental temperatures, but young mice expressed no evidence of torpor.

Aging↗
PubMed1988

Novelty-induced opioid analgesia in deer mice (Peromyscus maniculatus): sex and population differences.

Exposure to a new environment elicited significant, naloxone (1.0 mg/kg) reversible analgesic responses in three different populations of deer mice; Peromyscus maniculatus artemisiae from the mainland, and P. m. angustus and P. m. triangularis from small marine islands. In all cases male deer mice displayed significantly greater levels of analgesia than females. In addition, the levels of analgesia were significantly greater in the insular than in the mainland populations. These results indicate that there are substantial sex and population differences in the novelty-induced analgesia displayed by natural and laboratory populations of deer mice.

Analgesia↗
PubMed1986

Culturing Borrelia burgdorferi from spleen and kidney tissues of wild-caught white-footed mice, Peromyscus leucopus.

Borrelia burgdorferi was isolated most frequently from tissue of spleen (n = 13) and kidney (n = 10) and less often from blood (n = 5) of wild-caught Peromyscus leucopus. Prevalence of infection tended to be highest at sites where Lyme disease was most common (e.g., 5 of 6 mice were positive in East Haddam, Connecticut). Spirochetes were not isolated in Danbury or New Hartford, areas where this malady is rare. However, in Fairfield, where the disease is also uncommon, 4 of 9 mice were infected. Larval and nymphal I. dammini, containing borreliae, parasitized P. leucopus at all sites where B. burgdorferi was cultured from mice. Borreliae were also detected in D. variabilis feeding on hosts at two of the sites. P. leucopus appears to be an excellent animal to identify focal areas of B. burgdorferi.

Animals↗
PubMed2001

Mercury concentrations in deer mouse (Peromyscus maniculatus) tissues from Isle Royale National Park.

We used deer mice (Peromyscus maniculatus) to investigate variation in mercury exposure across the terrestrial ecosystem of Isle Royale National Park (Michigan, USA). Although previous work suggested that mercury (Hg) levels may be higher inside the Sargent Lake watershed of Isle Royale than outside the watershed, Hg concentrations in livers were higher outside the Sargent Lake watershed (100.13 ng Hg/g dry tissue) than inside the watershed (35.50 ng Hg/g dry tissue; P = 0.06). Mercury levels in kidneys did not differ significantly (P = 0.57) between samples collected outside (443.23 ng Hg/g dry tissue) and inside (360.62 ng Hg/g dry tissue) the Sargent Lake watershed. Mean Hg concentrations in the livers of mice at some sites in Isle Royale are not significantly lower (P = 0.62) than Hg concentrations considered by some government agencies to be unhealthy for human consumption. Although Hg concentrations in mouse tissues were not remarkably high (compared to heavily polluted sites), concern is warranted because: (1) Isle Royale National park is a protected area in a remote location; (2) any exposure in deer mice represents a path for biomagnification in the terrestrial food web; and (3) the source of this mercury remains unidentified.

Animals↗
PubMed2002

Immunological and physiological effects of chronic exposure of Peromyscus leucopus to Aroclor 1254 at a concentration similar to that found at contaminated sites.

Polychlorinated biphenyls (PCBs) are environmental contaminants known to cause adverse health effects to biological systems. Limited data are available on their effects on the immune system of wildlife species. Previously, we found that 4 and 6-week-old white-footed mice (Peromyscus leucopus) born from dams injected with a single dose (300 mg/kg) of Aroclor 1254, had altered immunological, hematological, and biochemical responses. Here, we examined the effect of transplacental, lactational and postnatal exposure to Aroclor 1254, at a concentration similar to that found at contaminated sites, on various physiological parameters of 22-week-old white-footed mice. Liver weight and liver somatic index of PCB treated animals were significantly higher, the combined weights of the adrenal glands were significantly lower and EROD and BROD enzyme activity was significantly higher compared to control values. The number of thymocytes of the treated mice was significantly lower than that of the controls; however, thymocytes of treated mice had a higher proliferative response to the mitogen Con A. These alterations were correlated with the PCBs body burdens. Some toxic effects of chronic exposure to PCBs, at levels comparable to exposure found in contaminated sites in the USA, are still evident in adult P. leucopus.

Animals↗