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seasonal changes in enzymes of aerobic heat production in the white-footed mouse.during seasonal acclimatization in white-footed mice (peromyscus leucopus), there is a substantial increase in the capacity for aerobic heat production under cold stress (mmax) in winter animals. the possibility that increases in levels of enzymes involved in aerobic heat production could be responsible for the increase in mmax was investigated in mice captured in summer and winter. activities of citrate synthase (cs) and beta-hydroxyacyl-coa dehydrogenase (hoad) and concentrations of cytochrome ...19816263112
diurnal rhythm of response to chronic intrahypothalamic melatonin injections in the white-footed mouse, peromyscus leucopus.a pronounced diurnal change in responsiveness to intrahypothalamic melatonin injections was observed in the white-footed mouse, peromyscus leucopus. 7 weeks of chronic daily afternoon (12 h after lights-on) injections of 500 ng melatonin into the vicinity of the suprachiasmatic nuclei (scn) caused a 66% reduction in female reproductive tract weight relative to saline-injected controls (p less than 0.01), with 83% of these animals having an imperforate vagina, and no animals having mature follicl ...19826890151
evidence for a brain site of melatonin action in the white-footed mouse, peromyscus leucopus.a brain site of melatonin action has been determined for the white-footed mouse (peromyscus leucopus). melatonin-beeswax implants releasing small quantities of melatonin (less than 100 ng/day) caused a 50% reduction in reproductive tract weight relative to controls (p less than 0.025) with 83% of these animals having an imperforate vagina, when implanted in the anterior hypothalamic nuclei (ah) and suprachiasmatic nuclei (scn). subcutaneous implants had little effect. implants in the ah and scn ...19827057959
daily melatonin rhythms in photoperiod sensitive and insensitive white-footed mice (peromyscus leucopus). 19827111341
geographic variation in peromyscus leucopus: short-day induced reproductive regression and spontaneous recrudescence.in order to determine if intraspecific differences exist in the photoperiodic control of the reproductive cycle of white-footed mice (peromyscus leucopus), 34 male and 60 female mice from either connecticut (ct), virginia (va), or georgia (ga) laboratory stocks were exposed to either a long (16l:8d) or short (9l:15d) photoperiod for up to 27 weeks. reproductive status (testis length or the presence of a perforate vagina) of these mice was assessed every 1 to 2 weeks. after this time, the males w ...19827126737
preantral intra-ovarian oocyte release in the white-footed mouse, peromyscus leucopus.adult white-footed mice, peromyscus leucopus, were kept either in long photoperiod (lp; ld 16:8) or in short photoperiod (sp; ld 8:16) for six weeks. ovaries were serially sectioned and examined histologically. preantral follicles were observed to release their oocyte into the ovarian stroma. this phenomenon is termed "preantral intra-ovarian oocyte release (pior)". the first step in pior appeared to be the interruption of the basal membrane and the thecal layer. pior was considered incomplete w ...19827127440
intraspecific differences for melatonin-induced reproductive regression and the seasonal molt in peromyscus leucopus. 19827152235
effects of advancing age on the ultrastructure of pinealocytes in the male white-footed mouse (peromyscus leucopus).quantitative comparison of pinealocyte ultrastructure in 3-month-old and 28-month-old male white-footed mice (peromyscus leucopus) revealed decreases both in the area of the golgi apparatus and in the number of dense-core vesicles. in contrast, no differences between these two age groups were noted in the areas of granular endoplasmic reticulum, vacuoles with flocculent content, lysosome-like bodies, or mitochondria. nor were any changes between groups of mice apparent in pinealocyte nuclear or ...19827153722
evidence for turnover of dna in the nucleus and in the cytoplasm of adult post-mitotic neurons in vivo.experiments were designed to determine if turnover of dna occurs in post-mitotic neurons of adult mammals. three-month-old laboratory mice, mus musculus, and white footed mice, peromyscus leucopus, were given three injections of 3h-thymidine (3h-tdr, 16 muci/g body weight) at noon, 4 pm and 8 pm, and were killed serially beginning 1 h after the last injection. the brain stem was removed from the animals and autoradiographed. some of the sections were treated with dnase prior to autoradiography. ...19827160228
daily melatonin injections: their usefulness in understanding photoperiodism in peromyscus leucopus. 19827166440
morphological and morphometric changes in the ovaries of white-footed mice (peromyscus leucopus) following exposure to long or short photoperiod.two experiments were carried out with a total of 36 white-footed mice (peromyscus leucopus) exposed to either long (lp) or short (sp) photoperiod for six weeks. ovaries and uteri were weighed. serial sections of the ovaries were processed for light microscopy. the total number of the interstitial gland cells, preantral and antral follicles with early and advanced stages of atresia as well as corpora lutea, was determined. uteri from lp mice weighed significantly more than those from sp mice in b ...19836682297
photoperiodic regulation of reproduction in the white-footed mouse. neuroendocrine aspects. 19836348509
on the occurrence of a myeloid body in pinealocytes of the white-footed mouse, peromyscus leucopus. an electron-microscopic study.the fine-structural features of pinealocytes of the white-footed mouse, peromyscus leucopus, were examined. a single population of pinealocytes was observed in both superficial and deep components of the gland. cells in both locations are characterized by the presence of an indented nucleus exhibiting a prominent nucleolus. the usual organelles in the perikaryon are the golgi complexes, mitochondria, endoplasmic reticulum, polysomes, microtubules and dense-core vesicles. in addition the perikary ...19836831535
inverse correlation between "synaptic" ribbon number and the density of adrenergic nerve endings in the pineal gland of various mammals.the number of "synaptic" ribbons was inversely correlated with the density of the adrenergic nerve endings of the pineal gland compared among a diverse group of species including the fox, cat, rat, cotton rat, white-footed mouse, djungarian hamster, ground squirrel, and chipmunk. the concentration of norepinephrine paralleled the number of adrenergic nerve terminals in the pineal glands of the cotton rat, rat, and ground squirrel, the only species in which norepinephrine concentrations were meas ...19836837939
a possible mechanism of rapid luteolysis in white-footed mice, peromyscus leucopus.adult female white-footed mice, peromyscus leucopus, were exposed to long (lp) or short (sp) photoperiods for 6 weeks (experiment i). another group of animals was kept for 6 weeks in sp, then injected sc with 30 micrograms prolactin twice daily for 2, 3, 4, or 6 days (experiment ii). ovaries from the mice in both experiments were weighed and serially sectioned for light microscopic examination of regressing corpora lutea. in experiment i, it was observed that vessels supporting corpora lutea wer ...19836864810
spirochetes in ixodes dammini and mammals from connecticut.spirochetes were observed in the midguts of 35% of 147 motile ixodes dammini from three locations in lyme and east haddam, connecticut. positive ticks were removed from eastern chipmunks (tamias striatus), raccoons (procyon lotor), white-footed mice (peromyscus leucopus), and a red squirrel (tamiasciurus hudsonicus). spirochetes were isolated in fortified kelly's medium from nine questing or partially engorged i. dammini adults and nymphs and from the bloods of a raccoon and a white-footed mouse ...19836881431
comparative rates of decline in the primary cloning efficiencies of smooth muscle cells from the aging thoracic aorta of two murine species of contrasting maximum life span potentials.primary cloning assays of thoracic aortic smooth muscle cells from an f1 hybrid strain of mus musculus demonstrated linear regressions of replicative potentials as functions of donor age (6-30 months), with regression coefficients, in two independent cohorts, of -1.69 +/- 0.27 (se) and -1.88 +/- 0.19 (se) clones per milligram wet weight of intima-media per month and correlation coefficients of -0.83 and -0.92 (p less than 0.001). secondary cloning (dilute plating from first passages) also demons ...19836401930
relationship between field strength and arousal response in mice exposed to 60-hz electric fields.white-footed mice, peromyscus leucopus, were exposed to 60-hz electric fields to study the relationship between field strength and three measures of the transient arousal response previously reported to occur with exposures at 100 kv/m. five groups of 12 mice each were given a series of four 1-h exposures, separated by an hour, with each group exposed at one of the following field strengths: 75, 50, 35, 25, and 10 kv/m; 8 additional mice were sham-exposed with no voltage applied to the field gen ...19836409124
radiotelemetric assessment of diel cycles in euthermic body temperature and torpor in a free-ranging small mammal inhabiting man-made nest sites.five free-ranging white-footed mice, peromyscus leucopus, known to inhabit man-made nest boxes were captured during winter, surgically-implanted with temperature-sensitive radiotelemeters, and released at the site of capture. the body temperatures of mice which voluntarily inhabited nest boxes were monitored from a remote location with an am receiver on 17 days.all five mice were able to maintain stable euthermic body temperatures (approximately 35-37°c during the day; 37-39°c at night) during e ...198328310688
the istar 1 serodeme of trypanosoma brucei: development of a new serodeme.an extensive serodeme of sequentially-isolated antigenic variants of african trypanosomes has been produced from both syringe-passaged and cyclically-transmitted trypanosoma brucei of the istar 1 clone derived from eatro 164. the majority of the antigenic variants were isolated from chronically-infected deer mice (peromyscus leucopus). the pattern of parasitemias during the course of infections initiated with syringe-passaged trypanosomes differed from those initiated with cyclically-transmitted ...19846439844
longevity-dependent organ-specific accumulation of dna damage in two closely related murine species.to measure directly the accumulation of dna damage with age, and to understand better the effect of modulators of dna damage in vivo, the dna of brain, liver, and kidney of two mice from different families, mus musculus and peromyscus leucopus, have been examined for age-dependent accumulation of single-strand breaks plus alkali-labile bonds, by the alkaline sucrose sedimentation method. these two species of small rodents are closely related taxonomically, yet differ significantly in maximum ach ...19846492898
vectorial capacity of north american ixodes ticks.ixodes dammini, the vector of lyme disease and babesiosis, is distributed in various locations in the northeastern quadrant of the united states and nearby canada. the life cycle of this tick, which includes larval, nymphal, and adult stages, spans at least two years. the tick over-winters between larval and nymphal feeding. horizontal transmission of pathogens is facilitated by a feeding pattern in which both the larval and nymphal stages feed on the white-footed mouse, peromyscus leucopus, and ...19846516453
avian and mammalian hosts for spirochete-infected ticks and insects in a lyme disease focus in connecticut.spirochetes and their vectors and reservoirs were studied in a lyme disease focus in east haddam, connecticut, from mid-may through september 1983. ixodes dammini subadults were comparable in number on white-footed mice (peromyscus leucopus) (means = 2.9 +/- 3.6 sd) to those on 27 different species of birds (means = 2.3 +/- 4.2 sd) representing 11 families within the order passeriformes. less commonly found ticks on birds (means less than or equal to 0.1) were immature ixodes dentatus and haemap ...19846516460
prevalence of the lyme disease spirochete in populations of white-tailed deer and white-footed mice.the prevalence of the ixodes dammini spirochete (ids) in white-tailed deer (odocoileus virginianus) and white-footed mice (peromyscus leucopus) was studied on the eastern end of long island, new york. both species commonly occur in a variety of habitats, are preferred hosts of ixodes dammini, and can harbor the spirochetes in the blood. each animal was examined for spirochetemia, tick infestation, and ids infection rates in the ticks that were removed from it. the results obtained suggest that i ...19846516461
seasonal changes in glycogen level and size of pinealocytes of the white-footed mouse, peromyscus leucopus: a semiquantitative histochemical study.glycogen level in and size of pinealocytes of the feral, white-footed mouse peromyscus leucopus, were studied by a semiquantitative histochemical method to determine whether seasonal changes exist in them under natural conditions, what temporal pattern they exhibit, and whether 24-hour changes in these parameters exist in different seasons, as shown in the laboratory dd-mice. marked seasonal changes were seen in both glycogen levels and nuclear densities (anova p less than 0.005). the size of pi ...19846545813
an immunocytochemical study of the luteinizing hormone-releasing hormone (lhrh) system in the white-footed mouse: effect of blinding and melatonin.previous studies have provided evidence that pineal-mediated gonadal atrophy involves the luteinizing hormone-releasing hormone (lhrh) system in some rodents. the purpose of the present study was to visualize the lhrh system in the brain of the white-footed mouse by immunocytochemical methods and to assess the influence of blinding or melatonin on the lhrh immunostaining characteristics of the median eminence. six intact adult female mice and six adult males (two intact, two blinded, and two wit ...19846400339
modification of testicular and thyroid function by chronic exposure to short photoperiod: a comparison in four rodent species.exposure of male syrian hamsters (mesocricetus auratus) for 10 weeks to short photoperiod (sp) providing 10 hr light: 14 hr darkness (10:14 ld) produced a significant reduction in the weights of the reproductive organs, plasma thyroxine (t4) levels and free t4 index (ft4i) compared to the values of animals exposed to long photoperiod (lp, 14:10 ld). c57bl male house mice (mus musculus) kept in sp (10:14 ld) had reproductive organ weights equivalent to those of mice kept in long days (14:10 ld) a ...19846146435
effect of naltrexone on food intake and hoarding in white-footed mice (peromyscus).increases in food consumption and hoarding in mammals have been shown to be immediate and preparative adjustments to the energetic stresses of temperate winters. the sensitivity of these behaviors to the opiate antagonist naltrexone was tested in non-deprived white-footed mice (peromyscus leucopus). mice received naltrexone hydrochloride intraperitoneally (10 mg/kg in saline vehicle) once daily for four consecutive days subsequent to an equivalent period of injection with saline as control. dail ...19846694998
antibodies to rickettsia rickettsii in peromyscus leucopus from a focus of rocky mountain spotted fever in connecticut.during 1980-1982, white-footed mice (peromyscus leucopus) were captured in newtown, connecticut, an area where rickettsia rickettsii, the etiologic agent of rocky mountain spotted fever, is thought to be enzootic. an indirect microimmunofluorescence test identified specific antibodies to this organism in 16 of 237 (7%) sera: titration end points for 14 samples were relatively high (1:128-1:2048). antibodies were detected in mice during 1980 and 1981 with monthly prevalences varying from 8 to 22% ...19846744122
identification of endemic foci of lyme disease: isolation of borrelia burgdorferi from feral rodents and ticks (dermacentor variabilis).borrelia burgdorferi, the etiological agent of lyme disease, was isolated from the blood, kidneys, spleens, eyes, or livers of white-footed mice (peromyscus leucopus) (n = 19 of 22) and from the blood, kidneys, or spleens of eastern chipmunks (tamias striatus) (n = 2 of 2) captured at three foci for lyme disease in eastern connecticut. these bacteria were cultured most frequently from spleens (n = 19) and kidneys (n = 15). b. burgdorferi persisted in one mouse for at least 60 days. one spirochet ...19853926816
photoperiodic regulation of reproductive development in male white-footed mice (peromyscus leucopus) born at different phases of the breeding season.male white-footed mice were maintained from birth in chambers equipped with latitudinal timers programmed to simulate the natural progression of daylengths at 42 degrees n latitude. mice were born into photoperiods starting on 1 april, 15 july, 15 september or 27 october. testes and seminal vesicles of april- and july-born mice were mature at 60 days of age; puberty was delayed by several months in animals born into the september and october photoperiods but these mice became fecund at about 3.5 ...19853968658
organophosphorus insecticide induced decrease in plasma luteinizing hormone concentration in white-footed mice.oral intubation of 50 and 100 mg/kg acephate inhibited brain acetylcholinesterase (ache) activity by 45% and 56%, and reduced basal luteinizing hormone (lh) concentration by 29% and 25% after 4 h in white-footed mice (peromyscus leucopus noveboracensis). dietary exposure to 25, 100, and 400 ppm acephate for 5 days substantially inhibited brain ache activity, but did not affect plasma lh concentration. these preliminary findings suggest that acute exposure to organophosphorus insecticides may aff ...19853975930
temporal patterns of brain cholinesterase activities of white-footed mice (peromyscus leucopus) following dosing with diazinon or parathion. 19853977404
mice as reservoirs of the lyme disease spirochete.in evaluating the white-footed mouse as a reservoir host for the lyme disease spirochete, we compared spirochete infection in vector ticks (ixodes dammini) having different histories of attachment to these mice, estimated their relative importance as hosts for immature i. dammini and compared the seasonality of tick activity and spirochetemia in mice. infection in trapped white-footed mice appears to be universal. prevalence of spirochetal infection in i. dammini correlates with frequency of att ...19853985277
effects of timed melatonin injections on reproduction in pinealectomized peromyscus leucopus.fifty reproductively mature female pinealectomized or sham-operated white-footed mice (peromyscus leucopus) were injected daily for 7 weeks with 50 micrograms melatonin at 12 hr after lights on. the injections started either on the day following surgery or 2 weeks after surgery. all mice were maintained at room temperature under long-day photoperiod (ld 16:8). pinealectomized and sham-operated mice injected immediately following surgery and sham-operated mice injected beginning 2 weeks after sur ...19854007479
two daily melatonin injections differentially induce nonshivering thermogenesis and gonadal regression in the mouse (peromyscus leucopus).female white-footed mice (peromyscus leucopus) were injected twice daily with 5, 10, 50, 100 micrograms melatonin (mel) or saline. injections were given for 7 weeks at 2 and 12 hours after lights-on under a long day (ld 16:8) photoperiod. afternoon administration of mel induced gonadal regression, although a dose of 50 micrograms or more was necessary to obtain a maximal response. a 5 micrograms mel injection in the afternoon resulted in intermediate reproductive tract weights. in white-footed m ...19854021740
pheromone-induced reproductive inhibition in young female peromyscus leucopus.soiled bedding and urine from adult female white-footed mice (peromyscus leucopus) were tested for their capacity to inhibit reproduction of young females. test animals were given either physical or airborne contact with soiled bedding from adult females, adult female urine, clean bedding, or water from 21 to 150 days of age. results indicate that reproductive inhibition is due to an airborne pheromone emitted by the adult females as a component of their urine. in the second experiment, young fe ...19854041520
effects of cold ambient temperatures on acute mortality of peromyscus leucopus dosed with parathion. 19854041648
eimeria species (apicomplexa: eimeriidae) infecting peromyscus rodents in the southwestern united states and northern mexico with description of a new species.of 198 deermice (peromyscus spp) collected from various localities in the southwestern united states and northern mexico, 106 (54%) had eimerian oocysts in their feces when examined. these included 50 of 106 (47%) peromyscus truei, 34 of 54 (63%) peromyscus maniculatus, 4 of 17 (24%) peromyscus leucopus, and 18 of 21 (86%) peromyscus eremicus. the following eimeria were identified from infected mice: eimeria arizonensis and eimeria langebarteli from p. truei; e. arizonensis, eimeria peromysci, a ...19854057004
mys, a family of mammalian transposable elements isolated by phylogenetic screening.it has recently been demonstrated both emperically and mathematically that transposable elements may spread rapidly throughout a population once introduced even when they dramatically reduce the fitness of individuals that carry them. such events result in pronounced differences in the phylogenetic distribution of genetic elements capable of rapid genome invasion. using a simple and general procedure to screen the genome of the white-footed mouse peromyscus leucopus, we have isolated a family of ...19852993916
comparative anatomy of the retino-hypothalamic tract in photoperiodic and non-photoperiodic rodents.this study examined whether the nearly symmetrical input from each eye to each suprachiasmatic nucleus previously reported in syrian hamsters (mesocricetus auratus) is a universal feature of retino-hypothalamic projections in photoperiodic rodents. intraocular injections of horseradish peroxidase (hrp) were used to trace the retino-hypothalamic tract in three species of photoperiodic rodents, turkish hamster (mesocricetus brandti), deer mouse (peromyscus maniculatus bairdi) and white-footed mous ...19862430681
peromyscus leucopus and microtus pennsylvanicus simultaneously infected with borrelia burgdorferi and babesia microti.borrelia burgdorferi, the etiologic agent of lyme disease, and babesia microti, the causative agent of human babesiosis, were isolated from 71 and 57%, respectively, of 14 specimens of peromyscus leucopus and microtus pennsylvanicus collected from prudence and patience islands, r.i. both pathogens were isolated from five individual rodents. the presence of these two infectious organisms in the same mammal suggests that individual larval ixodes dammini may ingest both pathogens and subsequently t ...19863517038
gonadotropin-releasing hormone neuronal system of the white-footed mouse, peromyscus leucopus.the cytoarchitecture of the gonadotropin-releasing hormone (gnrh) neuronal system of the female white-footed mouse (peromyscus leucopus) was characterized using immunocytochemical procedures on thick vibratome sections. most of the labelled cell bodies are organized loosely into three groups associated with the periventricular region of the medial preoptic area, the diagonal band of broca, and the olfactory peduncle. a small number of cells are scattered throughout the medial septum, retrochiasm ...19863523277
short photoperiod-induced gonadal regression: effects on the gonadotropin-releasing hormone (gnrh) neuronal system of the white-footed mouse, peromyscus leucopus.the peroxidase-antiperoxidase method was used to determine quantitatively the effect of short photoperiod-induced gonadal regression on the immunoreactive gonadotropin-releasing hormone (gnrh) neuronal system of female peromyscus leucopus. in mice exposed to either long (16l:8d) or short (8l:16d) photoperiod, immunoreactive cell bodies were loosely organized into six groups: olfactory peduncle, diagonal band of broca, septum, preoptic area (poa), anterior hypothalamus (ah), and basal hypothalamu ...19863539214
experimental inoculation of dogs with borrelia burgdorferi.to determine if dogs could serve as a reservoir for borrelia burgdorferi, three beagles were inoculated subcutaneously (sq) with 200 laboratory cultured spirochetes which were originally isolated from blood of a peromyscus leucopus from ft. mccoy, wisc. one four month old beagle was inoculated sq with 5 ground ixodes dammini from shelter island, n.y. which came from an area with a 50% b. burgdorferi tick infection rate; and another uninfected four month old beagle was housed loose on the floor w ...19863554844
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. ...19863577490
the prevalence and significance of borrelia burgdorferi in the urine of feral reservoir hosts.live borrelia burgdorferi were isolated from the blood and/or urine of white-footed mice (peromyscus leucopus) collected on shelter island, new york, in 1984 and 1985. prevalence of spirochetes in urine was consistently higher than in blood or both fluids simultaneously. spirochetes remained viable for 18-24 hours in urine and were maintained in culture for one week. mice removed from the field were spirocheturic for at least 13 months. one spirocheturic mouse developed spirochetemia one month a ...19863577491
diurnal detachment of immature deer ticks (ixodes dammini) from nocturnal hosts.to test the possibility that immature deer ticks (ixodes dammini) may concentrate in the nests of their mouse hosts, we recorded their pattern of detachment. in laboratory experiments, most engorged larvae (greater than 90%) and nymphs (greater than 80%) detached from hamsters between 1200-2000 hours when the 14-hr photophase began at 0600 hours. time of drop-off was similar regardless of when ticks attached to hosts, but attachment late in the day delayed drop-off by one full day. ticks detache ...19863946736
photoperiod time measurement for activity, torpor, molt and reproduction in mice.resonance light:dark cycles (ld 6:18, 6:30, 6:42, or 6:54) were used to establish that a circadian rhythm of light sensitivity is involved in the thermoregulatory and reproductive responses to a short day photoperiod in the mouse, peromyscus leucopus. a fifth group was maintained on the long day photoperiod of ld 16:8. after 19 weeks animals presented with ld 6:18 or 6:42 exhibited short day photoperiod responses: gonadal regression, incidence of spontaneous daily torpor and molt to the winter p ...19863952177
a comparative-evolutionary study of lipids in the aging brain of mice.the lipids of aging brain were studied using a comparative-evolutionary model involving two species of mice, mus musculus (mus) and peromyscus leucopus (peromyscus). mus ages 2.5 times faster than does peromyscus. brain weight, water content, cholesterol, and ethanolamine plasmalogen decreased and phosphatidyl ethanolamine increased in both species with age. differences between species included 12% more cholesterol/g total lipid extract in peromyscus than in mus throughout life, a linear increas ...19863785533
life shortening in mice exposed to fission neutrons and gamma rays. vi. studies with the white-footed mouse, peromyscus leucopus.some of the studies on late effects of neutron and gamma radiation previously carried out with the c57bl6 x balb/c f1 hybrids of mus musculus have been repeated with the white-footed mouse, peromyscus leucopus, a cricetid rodent of a different subfamily, with differing physiological characteristics and a different spectrum of pathologies. among the more important findings were the following: for both species, the life shortening per rad at low doses of either radiation was the same percentage of ...19863786676
proximate and ultimate controls on life-history variation: the evolution of litter size in white-footed mice (peromyscus leucopus).recruitment of litter-mates of nest-box-inhabiting white-footed mice was monitored to study the evolution of litter size. the frequency distribution of litter sizes was nonsymmetrical, and the most frequent litter size was less than the optimum. this was not the result of differential parental survival, which was independent of litter size produced. recruitment remained constant or increased slightly to a peak in litters of five young, and then dropped precipitously for larger litters. the singl ...198628564119
demography of a habitat generalist, the white-footed mouse, in a heterogeneous environment.a population of white-footed mice (peromyscus leucopus) in southeastern massachusetts was lived-trapped monthly in five habitat types for 5 yr in order to study the demography of a habitat generalist. we identified three demographic groups (two of low density and one of high density), which differed primarily in density, adult survival, proportion of males breeding, and variability in the proportion of males. the low-density segments of this population were at times able to achieve demographic p ...198729357183
mitochondrial dna and protein differentiation between hybridizing cytotypes of the white-footed mouse, peromyscus leucopus.restriction-enzyme analysis of mitochondrial dna and protein electrophoresis were used to document patterns of gene flow across a hybrid zone between chromosomal races of peromyscus leucopus. chromosomal markers (three inversions) are such that individuals can be classified as potential f1 's, backcrosses, or parental types. allozymic characterization of the hybrid zone is congruent with the chromosomal data (stangl, 1986) and indicates an assymetrical distribution of markers, with the northeast ...198728564355
reservoir competence of white-footed mice for lyme disease spirochetes.using the vector tick, ixodes dammini, we described the reservoir competence of the white-footed mouse, peromyscus leucopus, for the lyme disease spirochete, borrelia burgdorferi. nymphal i. dammini were used to infect mammals, and larval ticks were used to diagnose infection (a form of xenodiagnosis). one tick was nearly as efficient as more than 1 in transmitting the spirochete to mice. the duration of the prepatent period was about 1 week. prevalence of infection approached 100% in ticks that ...19873812887
lyme disease ecology in wisconsin: distribution and host preferences of ixodes dammini, and prevalence of antibody to borrelia burgdorferi in small mammals.lyme disease recently has been recognized in wisconsin. trapping studies were conducted at four geographically separate and ecologically distinct regions in wisconsin to elucidate the distribution and host preferences of ixodes dammini on small and medium sized mammals, and the occurrence of antibodies to borrelia burgdorferi in these wild mammals. peak i. dammini larval activity occurred from june-september. nymphs were most active from may-august. white-footed mice (peromyscus leucopus) and ch ...19873605501
genomic 5-methyldeoxycytidine decreases with age.significant losses of dna 5-methyldeoxycytidine residues in old age could disrupt cellular gene expression and contribute to the physiological decline of the animal. thus, the 5-methyldeoxycytidine content of dnas, isolated from the tissues of two rodent species of various ages, were determined. mus musculus lost dna methylation sites at a rate of about 4.7 x 10(4) (approximately 0.012% of the newborn level)/month. peromyscus leucopus lost dna 5-methyldeoxycytidine residues at a rate of only 2.3 ...19873611071
duration of the melatonin pulse in the hypothalamus controls testicular function in pinealectomized mice (peromyscus leucopus).forty-four pinealectomized white-footed mice (peromyscus leucopus) were stereotaxically implanted with a guide tube-cannula assembly in the area of the preoptic/anterior hypothalamus. easy insertion and removal of the melatonin-loaded cannula in the basal medial hypothalamus made it possible to examine whether duration of the melatonin pulse at the putative target site controls reproduction in mice. mice receiving melatonin every day for 10 h during either the day or night underwent gonadal regr ...19873620557
neurons in the suprachiasmatic area are labelled after intravenous injections of horseradish peroxidase.intravenous injections of horseradish peroxidase (hrp) produced labelled neurons in the suprachiasmatic area of house mice (mus musculus), deer mice (peromyscus maniculatus bairdi), and white-footed mice (peromyscus leucopus). in the two species of peromyscus, a significant proportion of the labelled cells was found within the suprachiasmatic nucleus (scn). these results suggest that when hrp is injected in the eyes to trace retinal inputs to the hypothalamus, some of the reaction product seen i ...19873622673
seasonal prevalence of borrelia burgdorferi in natural populations of white-footed mice, peromyscus leucopus.borrelia burgdorferi, the etiologic agent of lyme disease, was isolated from 111 of 237 peromyscus leucopus captured during all seasons of the year. borreliae were cultured from tissues of the spleen (101 mice), left kidney (76 mice), and right kidney (73 mice), from blood (12 mice), and from one fetus. mice were infected during the winter, when immature ixodes dammini were inactive. the prevalence of infection during the winter (less than or equal to 33%) was more than twofold lower than that d ...19873624451
effect of age and torpor on the circadian rhythms of body temperature, activity, and body weight in the mouse (peromyscus leucopus).age-related alterations in homeostatic mechanisms, as measured by changes in circadian rhythms, have been reported in the literature. the purpose of the present study was to determine if changes in the circadian rhythms of motor activity, body temperature, and body weight occur with age in the long-lived mouse, peromyscus leucopus, and to determine if the incidence of torpor (hypothermia) was age-dependent. young and old mice were entrained to an ld 12:12 cycle, and then physiological and behavi ...19873628326
dichlorvos toxicity in the white-footed mouse (peromyscus leucopus).the organophosphate pesticide, dichlorvos (ddvp), is used commonly to control ectoparasites in laboratory rodents colonies. this compound is relatively nontoxic to mus musculus at dosages several times the therapeutic level. however, usage of a similar therapeutic level in the white-footed mouse (peromyscus leucopus) resulted in substantial mortality. to determine whether p. leucopus is more susceptible than m. musculus to the toxic effects of ddvp, both species were exposed to 0, 3 and 6 g of p ...19873669600
suppression of pineal melatonin in peromyscus leucopus by different monochromatic wavelengths of visible and near-ultraviolet light (uv-a).the purpose of this study was to examine the effects of monochromatic visible and near-ultraviolet radiation (uv-a) on pineal melatonin suppression in the white-footed mouse, peromyscus leucopus. to this end, mice were entrained to a daily cycle of 8 h of light and 16 h of darkness. during the night when pineal melatonin contents were high, mice were individually exposed for 5 min to specific wavelengths of monochromatic light (10 nm half-peak bandwidths). control animals received the same handl ...19873676772
lyme disease and babesiosis: acaricide focused on potentially infected ticks.permethrin-treated cotton, intended as rodent nesting material, was distributed in wooded sites in which the agents of lyme disease and babesiosis were enzootic, in order to kill immature ixodes dammini, the ticks that transmit these human pathogens. such ticks feed most abundantly on white-footed mice (peromyscus leucopus), apparently the main reservoir hosts of these agents, and tend to concentrate in mouse burrows. mice captured after permethrin-treated cotton was distributed, were infested b ...19873555140
prevalence of borrelia burgdorferi and babesia microti in mice on islands inhabited by white-tailed deer.borrelia burgdorferi and babesia microti were isolated from 35 of 51 white-footed mice (peromyscus leucopus) and meadow voles (microtus pennsylvanicus) captured on two narragansett bay, r.i., islands inhabited by deer, the principal host for the adult stages of the vector tick, ixodes dammini. immature ticks parasitized mice from both islands. from 105 mice captured on four other islands not inhabited by deer neither pathogen was isolated, nor were i. dammini found.19873555339
accelerated wound repair in old deer mice (peromyscus maniculatus) and white-footed mice (peromyscus leucopus).the closure of bilateral full thickness cutaneous wounds, made over the back with a sharp paper punch, was measured and assessed histologically in outbred deer mice (peromyscus maniculatus) and white-footed mice (peromyscus leucopus). in contrast to inbred c57bl/6j laboratory mice (mus musculus), in which the rate of wound repair was more rapid in young than in mature or aged mice (cohen et al., 1987), wound repair in peromyscus was most rapid in aged animals. aged peromyscus (45 to 70 months) a ...19873571866
immunoreactive luteinizing hormone-containing neurons in the brain of the white-footed mouse, peromyscus leucopus.the distribution of immunoreactive lh in the brain of the white-footed mouse (peromyscus leucopus) was determined using immunocytochemical procedures. immunoreactive fibers are located in the hypothalamus, preoptic area, septum and amygdala. stained cell bodies are seen in the arcuate nucleus and preoptic area. gonadectomy enhances staining for lh in the brain.19873545894
prospective seroepidemiology of hantaviruses and population dynamics of small mammal communities of baltimore, maryland.we used a prospective seroepidemiological study, in conjunction with a mark-release-recapture protocol, to investigate the transmission of hantaviruses in four rodent species from baltimore, maryland, from june 1984 to june 1986. a total of 1,208 captures of 762 rodents provided 984 individual blood samples. the antibody prevalence, as determined by frequency of reciprocal indirect fluorescent antibody (ifa) titers greater than or equal to 32, was 33.9% in rats (rattus norvegicus, n = 466), 28.3 ...19872891308
effects of chronic polychlorinated biphenyls exposure on reproductive success of white-footed mice (peromyscus leucopus). 19873111392
a brain site for the antigonadal action of melatonin in the white-footed mouse (peromyscus leucopus): involvement of the immunoreactive gnrh neuronal system.quantitative assessment of immunocytochemical staining for gonadotropin-releasing hormone (gnrh) was undertaken to determine the effects of an intracranial implant of melatonin on the gnrh neuronal system in the male white-footed mouse (peromyscus leucopus). melatonin-containing pellets stereotaxically placed in the anterior hypothalamic area (ah) caused a 60% reduction in testes weight relative to control mice with melatonin-free pellets in the ah (p less than 0.01). subcutaneous melatonin-cont ...19873302747
new infectious spirochete isolated from short-tailed shrews and white-footed mice.a spirochete with two periplasmic flagella was isolated from the blood or tissues of spleens and kidneys from short-tailed shrews (blarina brevicauda) and white-footed mice (peromyscus leucopus) in connecticut and minnesota. after inoculation, the shrew-mouse spirochete infected swiss mice and syrian hamsters. this spirochete is morphologically and serologically distinct from the species of treponema, borrelia, leptospira, and spirochaeta examined.19873305565
prevalence of borrelia burgdorferi in white-footed mice and ixodes dammini at fort mccoy, wis.borrelia burgdorferi, the causative agent of lyme disease, was isolated from 15 of 17 white-footed mice (peromyscus leucopus) and 54 of 82 subadult ixodes dammini from fort mccoy, wis. of the 47 isolates tested, all reacted in indirect fluorescent-antibody tests with monoclonal antibodies directed against a surface protein of b. burgdorferi (approximate molecular weight, 31,000) and flagellins that are common to all borrelia species. indirect fluorescent-antibody reactions were variable when an ...19873305566
chromosomal aberrations in native small mammals (peromyscus leucopus and sigmodon hispidus) at a petrochemical waste disposal site: i. standard karyology. 19873314736
learning in mature mice (peromyscus leucopus) subjected to deep hypothermia as neonates.in certain species of nonhibernating rodents, although young nestlings cease breathing and heart action when their body temperature is lowered to near freezing, the nestlings need only be rewarmed to recover. this remarkable capacity for immediate recovery has been known many years, but long-range consequences of deep neonatal hypothermia have never before been investigated. mice (peromyscus leucopus) that had been exposed to four 2.5-hr episodes of deep (2-4 degrees c) hypothermia when 4-10 day ...19883365944
a novel postcopulatory block of reproduction in white-footed mice.female white-footed mice (peromyscus leucopus) fail to produce offspring when paired with a male from weaning until 150 days of age if an adult female or her odor is also present. the present study delineates more clearly which stage of the young female's reproductive cycle is inhibited by the chemosignal of the older female. age at vaginal opening and first estrus are delayed by the presence of the older female, but only for about 10 days. the presence of a male counteracts this delay. thus, th ...19883378075
serologic analyses of peromyscus leucopus, a rodent reservoir for borrelia burgdorferi, in northeastern united states.an enzyme-linked immunosorbent assay (elisa) and indirect fluorescent-antibody test were used to detect antibodies to borrelia burgdorferi, the causative agent of lyme disease, in peromyscus leucopus (white-footed mouse). of the 661 mice captured in connecticut, rhode island, and new york during 1980 and 1983 to 1987, 166 (25.1%) had antibodies to b. burgdorferi by elisa. comparative analyses of 210 serum specimens, collected in areas where lyme disease is endemic, revealed a threefold differenc ...19883384925
changes in infectivity and plasmid profile of the lyme disease spirochete, borrelia burgdorferi, as a result of in vitro cultivation.in vitro cultivation of borrelia burgdorferi, the etiologic agent of lyme spirochetosis, allows for the isolation and growth of this bacterium from infected tissues. however, continuous cultivation in modified kelly medium causes a reduction in the number of detectable plasmids and the loss of infectivity in the white-footed mouse, peromyscus leucopus. in an unpassaged culture of b. burgdorferi, nine plasmids were present, including seven linear plasmids ranging in size from 49 to 16 kilobases ( ...19883397175
effects of chronic polychlorinated biphenyls exposure on growth and reproduction of second generation white-footed mice (peromyscus leucopus). 19883122670
brief exposure to a natural predator, the short-tailed weasel, induces benzodiazepine-sensitive analgesia in white-footed mice.exposure to a natural predator, the short-tailed weasel, mustela erminea, elicited significant increases in the nociceptive responses of wild male white-footed mice, peromyscus leucopus. a short (30 sec), ecologically relevant, nonvisual exposure to a weasel elicited a relatively brief (15 min) analgesia that was insensitive to the opiate antagonist, naloxone (1.0 mg/kg), and was blocked by either pre- or post-exposure injections of the benzodiazepine antagonist, ro15-1788 (10 mg/kg), or agonist ...19883145512
ticks and biting insects infected with the etiologic agent of lyme disease, borrelia burgdorferi.members of 18 species of ticks, mosquitoes, horse flies, and deer flies were collected in southeastern connecticut and tested by indirect fluorescent-antibody staining methods for borrelia burgdorferi, the etiologic agent of lyme disease. an infection rate of 36.2% (116 tested), recorded for immature ixodes dammini, exceeded positivity values for all other arthropod species. prevalence of infection for hematophagous insects ranged from 2.9% of 105 hybomitra lasiophthalma to 14.3% of seven hybomi ...19883170711
new borrelia burgdorferi antigenic variant isolated from ixodes dammini from upstate new york.a previously undescribed borrelia burgdorferi antigenic variant was isolated from each of four ixodes dammini larvae removed from white-footed mice, peromyscus leucopus, captured in millbrook, n.y. this site is in the northern range of the known distribution of the tick in the northeastern united states. the molecular weights of approximately 32,500 and 35,500 for outer surface a and outer surface b proteins, respectively, were distinctly higher than those for previously characterized isolates f ...19883183008
borrelia burgdorferi infection surrounding la crosse, wis.this investigation defined the extent of borrelia burgdorferi infection surrounding la crosse, wis. white-footed mice, peromyscus leucopus or p. maniculatis, were captured from sites in wisconsin, minnesota, and iowa and cultured for b. burgdorferi to define the local boundaries of the midwestern lyme disease area. all foci of b. burgdorferi infection (n1, n2, n3, and n4) were located north of interstate highway 90 except focus s2, which was south of the highway near fort mccoy, wis. the interst ...19883230137
the urinary bladder, a consistent source of borrelia burgdorferi in experimentally infected white-footed mice (peromyscus leucopus).white-footed mice, peromyscus leucopus, were experimentally infected in the laboratory with borrelia burgdorferi, the causative agent of lyme disease. after mice were infected by intraperitoneal or subcutaneous inoculation or by tick bite, attempts were made to culture spirochetes from the urinary bladder, spleen, kidney, blood, and urine. spirochetes were most frequently isolated from the bladder (94%), followed by the kidney (75%), spleen (61%), and blood (13%). no spirochetes were isolated fr ...19883290239
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 darknes ...19882899500
melatonin acts in the brain to mediate seasonal steroid inhibition of luteinizing hormone secretion in the white-footed mouse (peromyscus leucopus).a melatonin-induced supersensitivity of the gonadotropin-secretory system to the negative feedback action of sex steroids is thought to be important to the timing of seasonal reproduction. however, little is known concerning this action of melatonin. in the present study the antigonadal action of melatonin in the anterior hypothalamus (ah) of the white-footed mouse, peromyscus leucopus, was used to examine the neuroendocrine mechanism whereby melatonin enhances the sensitivity to sex steroid neg ...19882969112
effects of photoperiod, beta-endorphin, and naloxone on in vitro secretion of testosterone in white-footed mouse (peromyscus leucopus) testes.the effects of the pro-opiomelanocortin-derived beta-endorphin (b-ep) and the opioid antagonist naloxone on in vitro secretion (accumulation of testosterone (t) in the medium) of t by testicular cells were assessed in adult white-footed mice (peromyscus leucopus). animals were housed under long days (16l:8d) to maintain testicular function or under short days (8l:16d) to induce gonadal regression. in vitro treatment with b-ep or naloxone did not affect basal secretion of t in dispersed cells fro ...19882974731
mys retrotransposons in peromyscus leucopus and transgenic mus musculus.the mys family of retrotransposons exhibits an interesting phylogenetic distribution with 500-1000 copies per haploid genome in the white-footed mouse peromyscus leucopus and no copies detectable in the house mouse mus musculus, even though most other repeated sequences are shared by these two species. comparison of the dna sequences from the 3' ends of five mys elements show that insertion occurs just upstream of a well-conserved 11 bp target sequence. transcription patterns of the elements in ...19882836794
melatonin does not affect in vitro secretion of testosterone in white-footed mouse testis.there is evidence that melatonin may exert its antigonadal effect by acting in the gonad to inhibit steroidogenesis. to explore this possibility a hormonally sensitive in vitro system of dispersed peromyscus leucopus testis was used to assess the effects of melatonin on human chorionic gonadotropin (hcg)- and dibutyryl-camp (dbcamp)-stimulated secretion of testosterone (t). at near-maximally stimulating doses of hcg and dbcamp, melatonin in concentrations of 2 x 10(-12) m to 2 x 10(-7) m did not ...19882852242
incompetence of catbirds as reservoirs for the lyme disease spirochete (borrelia burgdorferi).we compared the relative infectivity to vector ticks of gray catbirds (dumetella carolinensis) and white-footed mice (peromyscus leucopus) for the lyme disease spirochete (borrelia burgdorferi). of 28 catbirds captured in a site enzootic for this agent, 18 were infested by immature ixodes dammini, the tick vector. by comparison, each of 32 mice sampled concurrently from the same site was infested, and by about 10 times as many ticks as were found infesting the 3 most commonly netted bird species ...19892918445
molecular characterization of sylvatic isolates of trichinella spiralis.genetic relationships of 20 trichinella isolates from indiana wildlife were assessed and compared to trichinella isolated from an infected swine herd. trichinella larvae were isolated from coyotes, mink, raccoons, and red foxes. the larvae were maintained and amplified in white mice (icr) and wild mice (peromyscus leucopus). differences in phenotypic characters of sylvatic isolates in the 2 laboratory hosts included an approximately 10-30-fold increase in parasite fecundity in wild mice. dna for ...19892542508
polymorphism in the major histocompatibility complex class ii genes of peromyscus leucopus. 19892570749
geographic differences for delay of sexual maturation in peromyscus leucopus: effects of photoperiod, pinealectomy, and melatonin.effects of short-day photoperiod, pinealectomy, and melatonin on sexual maturation were tested in peromyscus leucopus from either connecticut (ct) or georgia (ga). laboratory reared-stocks from ct and ga were exposed to short daylength (photoperiod) from birth or 25 days of age. at 12 wk of age, delay in sexual maturation was indicated in most ct mice by decreased testis length, combined testes weight, and seminal vesicle weight. conversely, ga animals did not delay sexual maturation when expose ...19892624861
efficacy of the urinary bladder for isolation of borrelia burgdorferi from naturally infected, wild peromyscus leucopus.the efficacy of culturing urinary bladder tissue for borrelia burgdorferi from naturally infected, wild peromyscus leucopus mice was determined. the urinary bladder cultures were as efficient as spleen, kidney, and blood tissue cultures. the rapid b. burgdorferi isolation (mean, 6 days) from mouse urinary bladders should aid in defining new lyme disease foci.19892656749
ecology of lyme disease.borrelia burgdorferi is transmitted from wild animals to humans by the bite of ixodes dammini. this tick is common in many areas of southern connecticut where it parasitizes three different host animals during its two-year life cycle. larval and nymphal ticks have parasitized 31 different species of mammals and 49 species of birds. white-tailed deer (odocoileus virginianus) appear to be crucial hosts for adult ticks. all three feeding stages of the tick parasitize humans, though most infections ...19892667888
white-footed mice: tick burdens and role in the epizootiology of potomac horse fever in maryland.one hundred ten white-footed mice (peromyscus leucopus) were captured on horse farms in south-central maryland, examined for ticks, and tested for specific antibodies to ehrlichia risticii, the causative agent of potomac horse fever. peromyscus leucopus were consistently infested with immature american dog ticks (dermacentor variabilis), with monthly prevalences as high as 80%. sera from all 97 p. leucopus tested for antibodies to e. risticii were negative. this indicates that p. leucopus is not ...19892668569
differential distribution of immature ixodes dammini (acari: ixodidae) on rodent hosts.ectoparasites such as ixodid ticks that remain attached to hosts for several days while feeding on blood are able to overcome the inflammatory and immune responses of some hosts and not others. the immature stages of the deer tick ixodes dammini are found more frequently on the white-footed mouse, peromyscus leucopus, than on other rodents. we propose that p. leucopus is more tolerant to i. dammini than is a less common host, the meadow vole, microtus pennsylvanicus. to test this hypothesis, the ...19892693676
isospora peromysci davis, 1967 (apicomplexa: eimeriidae) in peromyscus leucopus and p. maniculatus (rodentia: cricetidae) from texas.oocysts of isospora peromysci (davis, 1967) (apicomplexa: eimeriidae) were recovered from the feces of 1/30 (3.3%) white-footed mice, peromyscus leucopus, in johnson county, texas. this report represents a new host and geographic record for the parasite. the coccidium was also found in 1/20 (5.0%) deer mice, p. maniculatus, from the same locale. morphological data are provided on the sporulated oocyst of i. peromysci and comparisons are made with previously published information on the species f ...19892724183
habitat distribution of ixodes dammini (acari: ixodidae) an lyme disease spirochetes on fire island, new york.the distributions of ixodes dammini spielman, clifford, piesman, and corwin and lyme disease spirochetes were studied on fire island, n.y. adult ticks were more common in high-shrub habitats (shrubby vegetation greater than or equal to 1 m high) than in grassy and lowshrub habitats (vegetation less than 1 m) in spring and fall. in the fall, adults were also common in the woods. adults were more abundant on narrow trails than in nearby vegetation. during the summer, questing nymphs and larvae wer ...19892724316
ear punch biopsy method for detection and isolation of borrelia burgdorferi from rodents.an ear punch biopsy method for the detection and isolation of borrelia burgdorferi from rodents was developed. the ear punch biopsy proved to be extremely sensitive, detecting spirochetes in 100% (11 of 11) of laboratory hamsters infected by tick bite and 95.8% (23 of 24) of hamsters infected by intraperitoneal inoculation. when cultured at 4 to 6 weeks postinfection, 92 to 100% of the ear punches taken from individual hamsters yielded viable spirochetes. b. burgdorferi was detected in sequentia ...19892768461
comparing the relative potential of rodents as reservoirs of the lyme disease spirochete (borrelia burgdorferi).the authors compared the contribution of white-footed mice (peromyscus leucopus), chipmunks (tamias striatus), and meadow voles (microtus pennsylvanicus) to infection of vector ticks with the lyme disease spirochete, borrelia burgddorferi. at one massachusetts location where lyme disease is endemic, all three species of rodents were found to be infected. prevalence of infection, however, varied from 90% for mice, and 75% for chipmunks to just 5.5% for meadow voles. infectivity of these hosts for ...19892787105
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