Muskrats are greater carriers of pathogenic Leptospira than coypus in ecosystems with temperate climates

Knowledge on the possible sources of human leptospirosis, other than rats, is currently lacking. To assess the distribution pattern of exposure and infection by Leptospira serogroups in the two main semi-aquatic rodents of Western France, coypus (Myocastor coypus) and muskrats (Ondatra zibethicus), results of micro-agglutination testing and renal tissue PCR were used. In coypus, the apparent prevalence was 11% (n = 524, CI95% = [9% - 14%]), seroprevalence was 42% (n = 590, CI95% = [38% - 46%]), and the predominant serogroup was Australis (84%). In muskrats, the apparent prevalence was 33% (n = 274, CI95% = [27% - 39%]), seroprevalence was 57% (n = 305, CI95% = [52% - 63%]), and the predominant serogroup was Grippotyphosa (47%). Muskrats should therefore be considered an important source of Grippotyphosa infection in humans and domestic animals exposed in this part of France.

Seasonal expressions of growth hormone receptor, insulin-like growth factor 1 and insulin-like growth factor 1 receptor in the scented glands of the muskrats (Ondatra zibethicus)

The growth hormone (GH)/insulin-like growth factor-1 (IGF-1) system plays an important role in regulating the cellular growth and organ development. The present study investigated the seasonal expressions of growth hormone receptor (GHR), IGF-1 and insulin-like growth factor 1 receptor (IGF-1R) in the scented glands of the muskrats. Morphological changes in the scented glands of the muskrats were observed significantly between the breeding and non-breeding seasons. Immunohistochemically, the expressions of GH, GHR, IGF-1 and IGF-1R were found in glandular cells and epithelial cells of the scented glands in both seasons. The protein and mRNA expression levels of GHR, IGF-1 and IGF-1R in the scented glands during the breeding season were noticeably higher than those of the non-breeding season. In parallel, the levels of GH and IGF-1 in the sera and scented glands were remarkably higher during the breeding season. In addition, small RNA sequencing showed that the predicted targets of the significantly changed hsa-miR-5100 and mmu-miR-6937-5p might regulate the expressions of Ghr, Igf-1 or Igf-1r. These results suggested that the morphological changes in the scented glands of the muskrats during the different seasons might be related to the expression levels of GHR, IGF-1 and IGF-1R. Meanwhile, GHR/IGF-1 system might regulate the scented glandular functions via endocrine or autocrine/paracrine manners.

Chronic exposure to inorganic mercury alters stress responses in male prairie voles (Microtus ochrogaster)

Male, but not female, prairie voles that experience chronic exposure to inorganic mercury display aberrant social behavior - avoiding unfamiliar conspecifics rather than approaching them. The mechanisms that underlie such behavioral changes are unknown, but likely involve the hypothalamus-pituitary-adrenal (HPA) axis. We tested this hypothesis by providing voles of both sexes with mercury chloride in their drinking water for ten weeks and then staging same-sex dyadic encounters after which plasma was assayed for corticosterone as an index of HPA activity. Consistent with sex-specific behavioral responses previously reported, mercury-treated males had lower plasma corticosterone after social encounters than did similarly-treated females or males that consumed normal drinking water. The results suggest that mercury-treated males may be less inclined toward social engagement with conspecifics due to reduced HPA activity.

Telocytes are localized to testis of the bank vole (Myodes glareolus) and are affected by lighting conditions and G-coupled membrane estrogen receptor (GPER) signaling

We aim to explore the presence of a novel cell type, telocytes (TCs), in the bank vole testis interstitium following G-coupled membrane estrogen receptor (GPER) signaling withdrawal. In addition, the involvement of interstitial cells in lipid homeostasis was investigated. Bank voles (actively reproducing or regressed) were administered with GPER antagonist (G-15; 50 μg/kg bw) injections. To examine TC distribution, ultrastructure, function, and their connotation in the interstitial tissue lipid balance, electron microscopic observations were implemented. Immunohistochemistry and Western blot for the TC marker, CD34, and lipid balance molecules: leptin, adiponectin, and perilipin were performed. Photoperiod-regulated testis steroidogenic function was estimated via serum melatonin level and intratesticular cholesterol concentrations in immunoenzymatic assays. We demonstrate the presence of TCs in bank vole testis interstitium. Distinctive TC morphology: small cell bodies with very long, slender prolongations, constituting a three-dimensional network around the interstitial cells was seen. Ultrastructurally, scarce mitochondria, a few cisternae of the endoplasmic reticulum, and lipid droplets indicated possible TC implications in lipid homeostasis. Changes in CD34 expression in TCs were seen in relation to GPER disturbances. In GPER-blocked testis, single TCs were present in the LD interstitium when in SD ones they were occasionally absent. Moreover, in TCs of SD voles, a lack of lipid droplets was revealed, likely reflecting attenuated TC function during regression. However, melatonin levels decreased in GPER-blocked LD and SD. Concomitantly, leptin, adiponectin, and perilipin expressions together with cholesterol content varied after blockage. Based on our results we suggest TCs are an important component of the bank vole testis interstitium as they are implicated in ultramorphology maintenance, protein interactions, and lipid homeostasis.

Seroprevalence of TBEV in bank voles from Poland-a long-term approach

Rodents are known to play a significant role as reservoir hosts for TBEV. During three sequential expeditions at 4-year intervals to three ecologically similar study sites in NE Poland, we trapped bank voles (Myodes glareolus) and then tested their blood for the presence of specific antiviral antibodies to TBEV. The strongest effects on seroprevalence were the extrinsic factors, site of capture of voles and year of sampling. Seroprevalence increased markedly with increasing host age, and our analysis revealed significant interactions among these three factors. Seroprevalence did not differ between the sexes. Therefore, based on the seroprevalence results, the dynamics of TBEV infection differ significantly in time, between local sub-populations of bank voles and with increasing host age. To fully understand the circulation of the virus among these reservoir hosts and in the environment, long-term monitoring is required and should employ a multi-site approach, such as the one adopted in the current study.

Puumala hantavirus infections in bank vole populations: host and virus dynamics in Central Europe

BACKGROUND

In Europe, bank voles (Myodes glareolus) are widely distributed and can transmit Puumala virus (PUUV) to humans, which causes a mild to moderate form of haemorrhagic fever with renal syndrome, called nephropathia epidemica. Uncovering the link between host and virus dynamics can help to prevent human PUUV infections in the future. Bank voles were live trapped three times a year in 2010-2013 in three woodland plots in each of four regions in Germany. Bank vole population density was estimated and blood samples collected to detect PUUV specific antibodies.

RESULTS

We demonstrated that fluctuation of PUUV seroprevalence is dependent not only on multi-annual but also on seasonal dynamics of rodent host abundance. Moreover, PUUV infection might affect host fitness, because seropositive individuals survived better from spring to summer than uninfected bank voles. Individual space use was independent of PUUV infections.

CONCLUSIONS

Our study provides robust estimations of relevant patterns and processes of the dynamics of PUUV and its rodent host in Central Europe, which are highly important for the future development of predictive models for human hantavirus infection risk.

Antibody detection from Middendorf's vole (Microtus middendorffii) against Tula virus captured in Mongolia

Mongolia in 2010 and 2011. A total of 76 voles belonging to the genera Myodes and Microtus were captured. Most of the voles that were seropositive to Tula virus antigen were Middendorf's voles (Microtus middendorffii (6/31)). Two of the 18 Myodes voles were also seropositive to Tula virus antigen. On the other hand, only one vole was seropositive to Puumala virus antigen. The results suggest that Tula virus was maintained in Middendorf's vole. This is the first report of detection of anti-Tula virus antibody in the central part of the Eurasia continent.

Detecting Methemoglobinemia in Animals with a Drop of Blood

A major concern during pesticide development and use is the impact on non-target species, such as raptors or domestic cats and dogs. Sodium nitrite and para-aminopropiophenone (PAPP) are two toxicants currently being studied for the control of invasive species, such as starlings and feral swine. When given to an animal these compounds oxidize hemoglobin, which renders it unable to carry oxygen resulting in methemoglobinemia. This study developed a method to estimate methemoglobin levels in mammals and birds by examining the efficacy of sodium nitrite to induce the conversion of hemoglobin to methemoglobin. Varying concentrations of sodium nitrite were added to aliquots of coyote, vole, feral swine, starling, and duck blood, collected from captive animals. The blood samples were analyzed spectrophotometrically to determine percent methemoglobin and digitally to determine red color values (RCV) associated with different methemoglobin levels. The avian and mammalian blood reached 100% methemoglobin levels at 200 mM and 15 mM sodium nitrite, respectively. All animals had similar RCV for a given percent methemoglobin. In conclusion, this study developed a procedure to quickly determine methemoglobin levels in mammals and birds. Furthermore, percent methemoglobin can be estimated with one standard curve from any animal species and an image of a blood spot. The technique will be useful during field studies, in agricultural areas, or in a veterinarian’s office for the rapid diagnosis of methemoglobinemia in non-target animals that have eaten toxicants/baits or baited animals.

Long-term spatiotemporal stability and dynamic changes in the haemoparasite community of bank voles (Myodes glareolus) in NE Poland

Long-term field studies on parasite communities are rare but provide a powerful insight into the ecological and evolutionary processes shaping host-parasite interactions. The aim of our study was to identify the principal factors regulating long-term trends in the haemoparasite communities of bank voles, and to this end, we sampled three semi-isolated populations of bank voles (n = 880) in 1999, 2002, 2006 and 2010 in the Mazury lake district region of NE Poland. Overall, 90.8 % of the bank voles harboured at least one of the species of haemoparasites studied. Whilst overall prevalence (all species combined) did not vary significantly between the surveys, different temporal changes were detected among voles in each of the three sites. In voles from Urwitałt, prevalence increased consistently with successive surveys, whereas in Tałty, the peak years were 2002 and 2006, and in Pilchy, prevalence oscillated without a clear pattern. Across the study, bank voles harboured a mean of 1.75 ± 0.034 haemoparasite species, and species richness remained stable with no significant between-year fluctuations or trends. However, each of the five constituent species/genera showed a different pattern of spatio-temporal changes. The overall prevalence of Babesia microti was 4.9 %, but this varied significantly between years peaking in 2006 and declining again by 2010. For Bartonella spp., overall prevalence was 38.7 %, and this varied with year of study, but the temporal pattern of changes differed among the three sites. The overall prevalence of Haemobartonella (Mycoplasma) was 68.3 % with an increase in prevalence with year of study in all three sites. Hepatozoon erhardovae had an overall prevalence of 46.8 % but showed a marked reduction with each successive year of the study, and this was consistent in all three sites. The overall prevalence of Trypanosoma evotomys was 15.4 % varying significantly between sites, but showing temporal stability. While overall prevalence of all haemoparasites combined and species richness remained stable over the period of study, among the five haemoparasites, the pattern of spatiotemporal changes in prevalence and abundance of infections differed depending on parasite species. For some genera, host age was shown to play an important role, but a significant effect of host sex was found only for Haemobartonella spp.

Effect of population density on reproduction in Microtus fortis under laboratory conditions

Between December 2011 and March 2012, the reproductive characteristics of Microtus fortis reared in the laboratory at different population densities were assessed. In all, 258 male and female voles were randomly divided into 4 groups and reared at densities of 2, 4, 6, and 8 animals per cage (sex ratio: 1:1). The results showed that the pregnancy rate (χ2 = 21.671, df = 3, P < 0.001) and first farrowing interval (F = 12.355, df = 3, P < 0.001) were significantly different among the different population density groups, but the mean litter size (mean ± SD) was not (F = 2.669, df = 3, P > 0.05). In particular, the reproductive index and sex hormone levels showed a significant difference among the different density groups studied.

[The application of polymerase chain reaction in real-time operation mode to detect DNA of agents of human granulocytic anaplasmosis and monocytic erlychiosis]

The analysis was applied to detect DNA of agents of human granulocytic anaplasmosis and monocytic erlychiosis. The sampling included 109 ticks of Ixodes species from Novosibirsk oblast and Khabarovsk kray and blood samples of 111 mouse-like rodents from Omsk oblast. The used techniques included polymerase chain reaction in real-time operation mode with set of reagents "RealBest DNA Anaplasma phagocytophilum/Ehrlichia muris, ehrlichia chaffeensis" ("Vector-Best" Novosibirsk) and double round polymerase chain reaction. The DNA of A. phagocytophilum, agent of granulocytic anaplasmosis and/or DNA of E. muris, agent of monocytic erlychiosis was detected in 21 ticks and in blood samples of 52 voles. Both techniques were applied. The DNA of A. phagocytophilum was detected in samples of 2 voles and in 1 tick only after polymerase chain reaction in real-time operation mode was applied. It demonstrated that the set of reagents "RealBest DNA Anaplasma phagocytophilum/Ehrlichia muris, ehrlichia chaffeensis" permits to detect the DNA of isolates of A. phagocytophilum subsumed to different genetic groups. The set can be used for fast and effective detection of the DNA of agents of agents of human granulocytic anaplasmosis and monocytic erlychiosis in suspensions of analyzed ticks and blood samples.

Serological evidence of tick-borne encephalitis virus infection in rodents captured at four sites in Switzerland

In a previous study, the presence of tick-borne encephalitis virus (TBEV) in questing Ixodes ricinus L. ticks and in field derived ticks that engorged on small mammals (n = 9,986) was investigated at four sites located in a TBE area in Switzerland. Two of these sites were already recognized as TBE foci (Thun and Belp) and the screening of ticks revealed the presence of TBEV in ticks at a third site, Kiesen, but not at the fourth one, Trimstein. The aim here was to test another approach to detect TBE endemic areas. Sera from 333 small mammals (Apodemus flavicollis, A. sylvaticus, Myodes glareolus) captured in 2006 and 2007 at the four sites were examined for the presence of antibodies against TBEV using immunofluorescence and avidity tests. Overall the prevalence of antibodies against TBEV in rodents reached 3.6% (12/333). At two sites known as TBE foci, Thun and Belp, anti-TBEV antibodies were detected in 9.9% (9/91) and 1.6% (1/63) of rodent sera, respectively. At the third site, Kiesen, recently identified as a TBE focus by the detection of TBEV in ticks, anti-TBEV antibodies were detected in 1.8% (2/113) of rodent sera. Finally, at Trimstein, none of the examined rodent sera had antibodies against TBEV (0/66). This study shows another approach to detect TBE foci by testing antibodies in small mammal sera that is less time-consuming and less expensive than molecular tools.

[Characteristics of erythrocyte lipids in blood of tundra voles (Microtus oeconomus Pall.) inhabiting areas with increased natural radioactivity]

Interrelations between the lipid characteristics of the blood erythrocytes and 226Ra accumulation in the body of tundra voles (Microtus oeconomus Pall.) inhabiting areas with different levels of the radiation background were investigated. It is shown that the ratio of the phospholipid (PL) fractions which cause the blood erythrocyte structure depends on the phase of the population cycle, as well as on the sex and age of tundra voles. The statistically significant interrelation between lysoforms and the sphingomielin content has been revealed in the blood erythrocyte PL of tundra voles; its scale somewhat differs for the animals from the reference and Ra areas. The peroxide concentration in the blood erythrocyte lipids of tundra voles from the Ra area exceeded the control values in all mature groups of the animals trapped at the depression phase of the population density. The 226Ra content in the bodies of the tundra voles which were trapped in the Ra area at the increased phase of the population cycle is for certain higher than that for the animals from the reference area. Interrelations between the lipid peroxidation parameters in the blood erythrocytes and the body 226Ra content for separate sex-age groups of tundra voles have been revealed.

[Comparative analysis of phospholipid composition in erythrocytes of mouse-like rodents of different species]

Comparative analysis of phospholipid quantitative composition of blood erythrocytes has been performed in white (laboratory mice and rats) and wild (tundra voles) mouse-like rodents. A non-characteristic of mammals low relative content of sphingomyelin is revealed in erythrocyte phospholipids in tundra voles. A hypothesis is put forward that the unique composition of erythrocyte lipids is a peculiar evolutionary developed strategy of adaptation aimed at survival under condition of constant circulation of agents of leptospirosis in populations of this species.

Metal exposure and effects in voles and small birds near a mining haul road in Cape Krusenstern National Monument, Alaska

Voles and small passerine birds were live-captured near the Delong Mountain Regional Transportation System (DMTS) haul road in Cape Krusenstern National Monument in northwest Alaska to assess metals exposure and sub-lethal biological effects. Similar numbers of animals were captured from a reference site in southern Cape Krusenstern National Monument for comparison. Histopathological examination of selected organs, and analysis of cadmium, lead, and zinc concentrations in liver and blood samples were performed. Voles and small birds captured from near the haul road had about 20 times greater blood and liver lead concentrations and about three times greater cadmium concentrations when compared to those from the reference site, but there were no differences in zinc tissue concentrations. One vole had moderate metastatic mineralization of kidney tissue, otherwise we observed no abnormalities in internal organs or DNA damage in the blood of any of the animals. The affected vole also had the greatest liver and blood Cd concentration, indicating that the lesion might have been caused by Cd exposure. Blood and liver lead concentrations in animals captured near the haul road were below concentrations that have been associated with adverse biological effects in other studies; however, subtle effects resulting from lead exposure, such as the suppression of the activity of certain enzymes, cannot be ruled out for some individual animals. Results from our 2006 reconnaissance-level study indicate that overall, voles and small birds obtained from near the DMTS road in Cape Krusenstern National Monument were not adversely affected by metals exposure; however, because of the small sample size and other uncertainties, continued monitoring of lead and cadmium in terrestrial habitats near the DMTS road is advised.

[Comparison of hemogram changes under chronic intermittent hypoxia in Lasiopodomys mandarinus and Kunming Mus musculus]

Mandarin vole (Lasiopodomys mandarinus) spends almost all of its life underground and must have evolved remarkable adaptations to cope with the subterranean hypoxic stress. The aim of present study is to explore the adaptation mechanism through the comparison of hemogram changes under chronic intermittent hypoxia in Mandarin vole and Kunming (KM) mouse (Mus musculus). Mandarin vole and KM mouse were treated with chronic intermittent hypoxia (10.0% oxygen), which was maintained by an oxygen cabin, for 4 h per day during four weeks. Then blood samples from the animals with and without hypoxia treatment were analyzed by a hematology analyzer. The results showed that under normoxic condition mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), white blood cell count (WBC) and platelet (PLT) in Mandarin vole were significantly lower than those in KM mouse. On the contrast, red blood cell count (RBC) and mean corpuscular hemoglobin concentration (MCHC) in Mandarin vole were higher than that in KM mouse. After four-week chronic intermittent hypoxia treatment, the hemogram changes were as following. MCV and HCT were elevated in Mandarin vole, not affected in KM mouse. Both hemoglobin (HGB) content and MCH in KM mouse increased, while only MCH increased in Mandarin vole. No obvious changes of WBC and PLT were found in two species. These results suggest that the adaptive mechanism of blood system in Mandarin vole responding to hypoxic conditions is different from that of KM mouse. As a subterranean vole, the Mandarin vole has a better tolerance to hypoxia.

Response to chronic intermittent hypoxia in blood system of Mandarin vole (Lasiopodomys mandarinus)

Mandarin voles (Lasiopodomys mandarinus) spend almost all their lives underground and must have evolved remarkable physiological adaptations to subterranean hypoxic stress. To understand the response to hypoxia in blood system of this rodent in a region with lower altitude, we tested and compared the responding characteristics between Mandarin vole and Kunming mouse (Mus musculus) under chronic normobaric hypoxic treatment (10.0% O(2), 4 w). The results showed that: 1) as for responses to chronic hypoxia, HIF-1 alpha, EPO and VEGF exhibited similar patterns in two species. The expression of HIF-1 alpha and VEGF significantly increased while EPO decreased significantly, and HIF-1 alpha showed a greater increase at 10.0% oxygen level in Mandarin voles; 2) both rodents responded to chronic hypoxia mainly by increasing MCH, though KM mouse responded more acutely; 3) the change in MCHC in Mandarin vole was ignorable though it is significantly higher than that in KM mouse whose MCHC changed extensively and 4) both before and after hypoxic treatment, the capillary density in Mandarin vole was significantly higher than that in KM mouse, and it increased sharply in KM mouse after treatment. Our results indicated that, compared to KM mice, Mandarin voles did respond effectively to hypoxia stress after long-term adaptation to subterranean life environment.

Azurocytes in wild field voles: factors associated with their occurrence

The occurrence of azurocytes (AZ), a type of leukocyte unique to voles and previously described for three Microtus species, is now reported in Microtus agrestis. The goal of this study was to shed new light on the possible function and significance of these cells and on how they play a role in the natural history of rodent species. Individuals from three vole populations were sampled monthly for 2 years. A hemogram was produced for each individual, and AZ counts estimated. The counts of AZ were much higher in pregnant females, and these levels were higher the higher the past vole density. Males had low prevalences and counts, both for breeding and nonbreeding individuals, but they showed a seasonality that varied with age, body condition, and current and past vole density. Also, the occurrence of AZ in males was more likely after they had had low levels of indicators of condition, suggesting that azurocytes may result from a response to infection. Hence, overall our results suggest that, in females, these cells may be important for reproduction and may have a role in inducing abortion when conditions are not favorable, while in males they might be a response to infection.

[Effect of IgG3 antibody purified from sera of Microtus fortis against Schistosoma japonicum]

IgG3 antibody reaction to soluble antigens prepared from schistosomula (SSA), adult worms (SAWA) and eggs (SEA) in laboratory-bred Microtus fortis (Mf), BALB/c mice and Kunming (Km) mice challenged by cercariae of Schistosoma japonicum was detected by indirect ELISA. The effect of purified IgG3 antibody on in vitro killing schistosomula and protecting mice from infection of S. japonicum was evaluated. The IgG3 antibody level in Mf against SSA and SAWA increased significantly by 79.6 percent and 49.6 percent after the fourth week of challenge infection, but no significant increase in BALB/c mice. Purified IgG3 antibody from laboratory-bred Mf and wild Mf effectively killed schistosomula, and that of the wild Mf induced higher worm-reduction rate. The death rate of schistosomula due to IgG3 antibody purified from sera of laboratory-bred Mf and wild Mf was 2.35 and 5.88 times as high as that of Km mice respectively. The results suggest that IgG3 antibody from Microtus fortis may play an important role in immunity against S. japonicum.

[Annual variation in hematological indices in a fluctuating population of bank vole (Clethrionomys glareolus)]

The quantitative and structural hematological indices were studied in bank vole in different reproductive states (overwintered individuals, mature underyearlings, and immature underyearlings) in different years corresponding to different phases of the population cycle. The annual changes in certain hematological indices have been revealed for each reproductive state irrespective of the population cycle phase.

Early experience affects the traits of monogamy in a sexually dimorphic manner

The goal of this study was to examine the effects of early life experiences on the subsequent expression of traits characteristic of social monogamy in prairie voles (Microtus ochrogaster). During cage changes parents and their offspring were either transferred between cages in a cup (zero manipulation, MAN0) or with a gloved hand (one manipulation, MAN1). Following weaning the offspring were tested for alloparental behavior. In adulthood they were tested for the capacity to form partner preferences, behavior in an elevated plus-maze (EPM), and corticosterone levels. MAN0 males (but not females) showed lower levels of alloparental behavior than MAN1 males. MAN0 females (but not males) were less likely to form pair bonds than MAN1 females. MAN0 animals of both sexes were less exploratory in the EPM than MAN1 counterparts. These experiments support the hypothesis that behaviors used to characterize monogamy are vulnerable in a sex-specific manner to early experience.

Photoperiod and Temperature Can Regulate Body Mass, Serum Leptin Concentration, and Uncoupling Protein 1 in Brandt’s Voles (Lasiopodomys brandtii) and Mongolian Gerbils (Meriones unguiculatus)

Environmental factors play an important role in the seasonal adaptation of body mass and thermogenesis in wild small mammals. In this study, we performed a factorial experiment (temperature x photoperiod) in which Brandt's voles and Mongolian gerbils were acclimated to different photoperiods (long photoperiod, 16L : 8D; short photoperiod, 8L : 16D) and temperatures (warm, 23 degrees C; cold, 5 degrees C) to test the hypothesis that photoperiod, temperature, or both together can trigger seasonal changes in serum leptin level, body mass, thermogenesis, and energy intake. Our data demonstrate that Brandt's voles showed a remarkable decrease in body mass in both the cold and a short photoperiod. However, no significant changes in body mass were found for gerbils exposed to similar conditions. The short photoperiod induced a decrease in serum leptin levels for both voles and gerbils that might contribute to an increase in energy intake. Furthermore, the short photoperiod induced an increase of uncoupling protein 1 (UCP1) content for both voles and gerbils, and cold can further enhance the increase in voles. No interactions between photoperiod and temperature were detected for the two species. Brandt's voles can decrease their body mass through changes in energy intake and expenditure, while Mongolian gerbils can keep body mass relatively stable by balancing energy metabolism under winterlike conditions. Leptin was potentially involved in the regulation of body mass and thermogenic capacity for the two species.

[Seasonal variation in hematological indices in bank vole (Clethrionomys glareolus) in different reproductive states]

Hematological and hematopoietic indices were studied in various seasons in bank vole in different reproductive states. The seasonal variation in the indices demonstrated patterns typical of each state and reflecting the adaptive response to changed habitat conditions.

Social environment regulates corticotropin releasing factor, corticosterone and vasopressin in juvenile prairie voles

Stressful social conditions, such as isolation, that occur during sensitive developmental periods may alter present and future social behavior. Changes in the neuroendocrine mechanisms closely associated with affiliative behaviors and stress reactivity are likely to underlie these changes in behavior. In the present study, we assessed the effects of post-weaning social housing conditions on the neuropeptides arginine vasopressin (AVP) and oxytocin (OT), and components of the hypothalamic-pituitary-adrenal axis (corticotropin releasing factor: [CRF], and corticosterone: [CORT]) in the prairie vole (Microtus ochrogaster), a socially monogamous bi-parental rodent. Following weaning at 21 days of age, prairie voles were maintained in one of three housing conditions: social isolation (isolate), paired with a same sex sibling (sibling) or paired with a stranger (stranger) of the same sex and age. Housing conditions were maintained for either 4 or 21 days. Central CRF, AVP and OT immunoreactivity (ir) were quantified and circulating plasma CORT, AVP and OT were assayed. Isolated voles had higher CRF-ir in the paraventricular nucleus of the hypothalamus (PVN) compared with sibling and stranger housed voles. Plasma CORT was significantly higher in isolates. AVP-ir was significantly lower in the PVN of isolate females compared to either sibling females or stranger females. However, AVP-ir was significantly higher in the supraoptic nucleus (SON) of isolates compared to siblings. There were no differences in central OT-ir or plasma OT. These results identify neuroendocrine mechanisms which respond to isolation and potentially modulate behavior.

Histological and serological evidence of experimental paracoccidioidomycosis in Calomys callosus (Rodentia: Cricetidae)

The responses of animal experimental models related to the infectivity, virulence and pathogenicity of Paracoccidioides brasiliensis is constantly used to develop new perspectives of investigation. The rodent Calomys callosus, Rengger 1830 (Rodentia: Cricetidae) is an indigenous inhabitant of the savannah environment found in the central regions of Brazil. The aim of the present work was to evaluate the histopathological and serological features of C. callosus after inoculation with the Pb18 strain of P. brasiliensis. Furthermore, A/Sn and B10.A mice strains were also tested to compare the results obtained in C. callosus to these well-established experimental models of resistance and susceptibility respectively. In every instance, survival analysis was performed, and histopathological study of the lungs, liver and spleen was employed to investigate tissue involvement, degree of inflammation and fungal presence. Levels of antibodies to P. brasiliensis were measured by using an enzyme-linked immunosorbent assay after 4 weeks and at the advanced stage of infection. The mortality rate was proportional to inoculation dose in all groups, but overall it was much superior in C. callosus than in the B10.A-susceptible mice. Macroscopical and microscopical pathological alterations were also more extensive and remarkable for C. callosus, once again proportional to inoculation dose, but more noticeable differences among the studied groups were found with 0.6x10(5) inoculum. In addition, the serological profile of C. callosus was similar to that found for B10.A-susceptible mice. Infection of C. callosus with 0.6x10(8) Pb18 inoculum resulted in more serious illness, and it decreased in severity in proportion to the inoculum dose. This difference was more pronounced in C. callosus, and the clinical, serological and pathological findings in this animal were more intense and precocious compared with the B10.A-susceptible mice. The present results suggest that C. callosus is a potentially alternative experimental animal model for paracoccidioidomycosis infection.

Cowpox virus infection in natural field vole Microtus agrestis populations: delayed density dependence and individual risk

1. Little is known about the dynamics of pathogen (microparasite) infection in wildlife populations, and less still about sources of variation in the risk of infection. Here we present the first detailed analysis of such variation. 2. Cowpox virus is an endemic sublethal pathogen circulating in populations of wild rodents. Cowpox prevalence was monitored longitudinally for 2 years, in populations of field voles exhibiting multiannual cycles of density in Kielder Forest, UK. 3. The probability that available susceptible animals seroconverted in a given trap session was significantly positively related to host density with a 3-month time lag. 4. Males were significantly more likely to seroconvert than females. 5. Despite most infection being found in young animals (because transmission rates were generally high) mature individuals were more likely to seroconvert than immature ones, suggesting that behavioural or physiological changes associated with maturity contribute to variation in infection risk. 6. Hence, these analyses confirm that there is a delayed numerical response of cowpox infection to vole density, supporting the hypothesis that endemic pathogens may play some part in shaping vole cycles.

Short photoperiod influences energy intake and serum leptin level in Brandt's voles (Microtus brandtii)

Photoperiod cues play important roles in the regulation of seasonal variations in body mass (BM) and energy balance for many small mammals. The present study was designed to examine the effects of photoperiod acclimation on BM, energy intake, and serum leptin levels in Brandt's voles (Microtus (Lasiopodomys) brandtii). After 4 weeks of acclimation to either long (LD; light:dark, 16:8) or short (SD; 8:16) photoperiod, SD voles had lower BM, body fat mass, and dry mass of liver and kidneys, but higher digestible energy intake in comparison to LD voles. SD voles also showed a lower level of serum leptin than did LD voles. Furthermore, the level of serum leptin was correlated positively with body fat mass and negatively with gross energy intake. Together, these data suggest that Brandt's voles employ a strategy of minimizing body growth, increasing energy intake, and mobilizing fat deposition in response to cues associated with short photoperiod. Furthermore, leptin seems to be involved in the regulation of BM and energy balance mediated by photoperiod.

Regulation of body weight and thermogenesis in seasonally acclimatized Brandt's voles (Microtus brandti)

Seasonal changes in an animal's morphology, physiology, and behavior are considered to be an adaptive strategy for survival and reproductive success. In the present study, we examined body weight and several behavioral, physiological, hormonal, and biochemical markers in seasonally acclimatized Brandt's voles (Microtus brandti) to test our hypothesis that Brandt's voles can decrease energy intake associated with decrease in body weight, body fat content, serum leptin level, and increasing thermogenesis in winter conditions. We found that the body weight of Brandt's voles was lowest in winter (December to February) and highest in spring and early summer (May to June). This seasonal variation in body weight was associated with changes in other markers examined. For example, the winter decrease in body weight was accompanied by increased energy intake and enhanced nonshivering thermogenesis (NST) as well as by decreased body fat mass and reduced levels of circulating leptin. Further, circulating levels of leptin were positively correlated with body weight and body fat mass, and negatively correlated with energy intake and uncoupling protein 1 contents. Together, these data do not support our hypothesis and suggest that leptin may be involved in this process and serve as a starvation signal in Brandt's voles.

[The parameters of antioxidant status of tissues in the offspring of tundra vole (Microtus oeconomus Pall.) inhabiting areas with increased natural radioactivity]

The parameters of the lipid peroxidation regulatory system (the antioxidative and antiperoxidant activities, the peroxide content, the lipid peroxidation intensity) in the tissues and the activities of the antioxidative defence enzymes (the peroxidase activity in blood, the superoxide dismutase activity in the blood erythrocytes) are studied in progeny of tundra vole which are reproduced from parent inhabiting areas with different radioecological environment during a long time. The progeny had the preservation of the changed antioxidant status. The scale of the changing of the investigating parameters depend on the state of radionucleoids contamination of areas where tundra voles are caught, sex of rodents, the content of antioxidants in lipids of tissues of parents.

Use of comet and micronucleus assays to measure genotoxicity in meadow voles (Microtus pennsylvanicus) living in golf course ecosystems exposed to pesticides

The purpose of this study was to conduct a biomonitoring study to measure the effects of pesticide exposure in meadow voles (Microtus pennsylvanicus) living in golf courses of the Ottawa/Gatineau region of Canada. In this article we present the results from the comet and micronucleus assay. Voles were captured in 2001 and 2002 at five golf courses and two reference sites. Blood was collected from sedated voles. Three animals from each course were euthanized to determine body burdens of historically used organochlorine (OC) and metal-based pesticides. Exposure to in-use pesticides was determined from detailed golf course pesticide use records. Comet tail length and tail moment were not related to body burdens of OC pesticides and metals historically used on these golf courses. In generally, tail length and moment significantly decreased in relation to days since last application of a pesticide, and to days since the last application of a specific fungicide (Daconil) containing a potentially genotoxic active ingredient (chlorothalonil). The slopes of these curves in 2002 were not significantly different than the half-life decay curve of chlorothalonil on vegetation. Both comet assay parameters appeared to increase in a dose-dependent manner with the amount of the last application Daconil. The number of micronucleated polychromatic erythrocytes was not related to any pesticide application parameter.

[Variations of some physiological and biochemical indices in the population of red-backed vole (Clethrionomys rutilus)]

We studied the changes in the population density of the red-backed vole (Clethrionomys rutilus Pall.) on the northern coast of the Sea of Okhotsk (60 degrees N) during three population cycles (1980-1990). A total of 3111 animals were studied, including 1006 alive voles. For evaluation of the population stress and food deficit, a complex of biochemical (blood level of glucose and liver levels of glycogen and lipids) and physiological (blood content of leucocytes, spleen weight, etc.) indices was used. At a high population density, the influence of stress continues during the reproductive period, after its termination, and, supposedly, until the beginning of a new reproductive period, while at a low population density, the consequences of stress were expressed only in the second half of the reproductive period. The signs of starvation were recorded only in some semiadult voles in a high density population. It has been confirmed that stress acts as a mechanism involved in regulation of the population density of small rodents.

Susceptibility of common voles to experimental toxoplasmosis

Common voles (Microtus arvalis) in groups of nine to 10 animals were inoculated per os with a dose of 1, 10, 1x10(2), 1x10(3), and of the K1 strain of Toxoplasma gondii. All the common voles inoculated with 1 to 1 x 10(3) oocysts remained subclinical and survived. Three of the 10 voles inoculated with 1 x 10(4) oocysts died between days 7 and 12 post inoculation (p.i.). Antibodies were demonstrated in all the infected voles killed on day 60 p.i. The highest antibody titres in voles detected by the dye test (DT) and latex agglutination test (LAT) were 1,024 and 1,280, respectively.

Influence of a natural stressor (predator odor) on locomotor activity in the meadow vole (Microtus pennsylvanicus): modulation by sex, reproductive condition and gonadal hormones

Sex differences in a variety of non-reproductive behaviors have been indicated to occur in seasonally breeding polygynous promiscuous rodents such as the meadow vole, Microtus pennsylvanicus. The present study was designed to assess the effects of reproductive and hormonal status on the locomotor responses of meadow voles following brief exposure to the odors of a natural predator, the Red fox (Vulpes vulpes). Adult male and female meadow voles, which are seasonal photoperiodically-induced breeders, were housed in either mixed sex pairs under a long, reproductively stimulatory photoperiod (simulating breeding: long light cycle, paired: LLC + P) or in same-sex pairs under a short, reproductively inhibitory photoperiod (simulated non-breeding: short light cycle, non-paired: SLC-NP). On 2 consecutive days following 1 day of baseline activity monitoring, voles were exposed individually for 3 min to fox odor and a novel pungent control odor (extract of almond). The levels of various measures of activity that were displayed by the voles were assessed by an automated Digiscan activity monitoring system. LLC + P (simulated breeding) voles displayed higher basal levels of activity relative to SLC + NP (simulated non-breeding) voles, with males displaying greater activity than females. LLC + P (simulated breeding) males displayed a significant reduction in activity levels following exposure to fox odor relative to control odor. The reductions in activity following fox odor exposure were related to plasma testosterone levels such that a larger behavioral response (i.e. greater reduction) was associated with higher levels of testosterone. Furthermore, dividing males into high and low testosterone groups based on the median levels of testosterone revealed that high but not low testosterone males displayed reductions in activity following exposure to fox odor relative to control odor. No changes in activity levels following exposure to fox odor were noted in SLC-NP males, and either SLC-NP or LLC + P females. These results show that this sexually dimorphic non-reproductive behavior is significantly influenced by reproductive condition and gonadal hormone levels.

Role of steroid hormones in Trichinella spiralis infection among voles

Males are generally more susceptible to parasite infection than females. This sex difference may reflect the suppressive effects of testosterone and enhancing effects of estradiol on immune function. This study characterized the role of circulating steroid hormones in sex differences after infection with the nematode Trichinella spiralis. Because testosterone suppresses immune function and because polygynous males have higher circulating testosterone concentrations than monogamous males, sex differences in parasite burden were hypothesized to be exaggerated among polygynous meadow voles compared with monogamous prairie voles. As predicted, sex differences in response to T. spiralis infection were increased among meadow voles; males had higher worm numbers than females. Male and female prairie voles had equivalent parasite burden. Overall, prairie voles had higher worm numbers than meadow voles. Contrary to our initial prediction, differences in circulating estradiol concentrations in females, testosterone concentrations in males, and corticosterone concentrations in both sexes were not related to the observed variation in T. spiralis infection. Taken together, these data suggest that not all sex differences in parasite infection are mediated by circulating steroid hormones and that adaptive-functional explanations may provide new insight into the causes of variation in parasite infection.

[DNA-protein cross-links in leukocytes of the field mouse (Apodemus agrarius) and the bank vole (Clethrionomys glareolus) dwelling in the territory of a radioactive waste storage station]

DNA-protein cross-links in white blood cells of Apodemus agrarius and Clethrionomys glareolus dwelling in the territory of the guarded zone of the radioactive waste storage in Sergievo Posad (area with gamma-background 50-400 microR/h) have been determined. As a control the animals from sanitary protected area of Sergievo Posadsky department (gamma-background on the soil surface is 8-10 microR/h) was used. It was found that the doses received by Apodemus agrarius and Clethrionomys glareolus, resulted in increasing of the DNA-protein cross-link level in the Apodemus agrarius white blood cells by a factor of 1.8, and in Clethrionomys glareolus by a factor of 1.4, in comparison with control. The increase of DNA-protein cross-link number reliably correlates with the beta-emitting nuclide content in animal bodies. The changes in the number white of cells and in the white blood composition were not observed.

Sex and seasonal differences in the rate of cell proliferation in the dentate gyrus of adult wild meadow voles

In order to study the neurobiological basis of seasonal changes in hippocampal structure and function, the rate of cell proliferation was examined in male and female wild meadow voles captured during different seasons. We found that the number of [3H]thymidine-labeled cells varied across the seasons and across sex in the meadow vole. Non-breeding female meadow voles had a higher rate of cell proliferation and cell death than males captured during either season or breeding females. These seasonal changes in the female meadow vole were associated with both fluctuating levels of adrenal steroids and gonadal steroids. Estradiol level was highly correlated with both the number of [3H]thymidine-labeled cells and the number of pyknotic cells in female meadow voles, with high levels of estradiol being associated with low levels of cell proliferation and cell death. Corticosterone level was associated with the number of [3H]thymidine-labeled cells in the hilus of female meadow voles. This seasonal change in the number of [3H]thymidine-labeled cells was also related to the overall volume of the hippocampus. At variance with past literature, there was no statistically significant sex difference favoring males in hippocampal volume, although the means were in the predicted direction. In male meadow voles, the number of pyknotic cells was related to testosterone level, with high levels of testosterone being associated with greater levels of cell death in the granular cell layer. There was also a suggestion that the number of [3H]thymidine-labeled cells in the hilus varied seasonally in males, with higher rates of cell proliferation during the breeding season than during the non-breeding season. In summary, we found that there were large fluctuations across the season in the rate of cell proliferation in the dentate gyrus of adult female meadow voles. Females captured during the non-breeding season had higher rates of cell proliferation in the granule cell layer than females captured during the breeding season. This seasonal fluctuation was related to hormone levels, with high levels of corticosterone and estradiol being related to lower levels of cell proliferation. These seasonal changes in cell proliferation may be related to known changes in spatial learning in the meadow vole and provide insights into changes in the hippocampus that occur in other species, including primates.

Stress affects corticosteroid and immunoglobulin concentrations in male house mice (Mus musculus) and prairie voles (Microtus ochrogaster)

Glucocorticoids, secreted in response to perceived stress, can suppress immunoglobulin (Ig) levels and compromise immune function in mice and rats. Prairie voles (Microtus ochrogaster) have been reported to exhibit basal corticosterone concentrations that would cause pathological changes in the immune function of most other rodents. The goals of the present study were to verify that serum corticosterone concentrations are high in prairie voles, as compared with house mice (Mus musculus), by measuring serum corticosterone with the same RIA; to examine the effects of mild stressors on corticosterone response in both species and to examine the effects of elevated corticosterone levels on IgM and IgG levels in prairie voles and house mice. After 2 weeks of randomly timed 15-min daily restraint or cold-water swim sessions, animals were injected with sheep red blood cells. The data confirmed that basal blood concentrations of corticosterone were higher in prairie voles than house mice, but these high levels doubled after the first swim session in prairie voles, indicating that the adrenals can respond to stressors by producing increased corticosterone. After stress, antibody production (both IgM and IgG) was reduced in house mice but not in prairie voles, despite higher blood concentrations of glucocorticoids in prairie voles. Although body mass was statistically equivalent between species, prairie voles and mice differed dramatically in adrenal and splenic masses. Average adrenal mass of prairie voles was approximately three times the average mass of these organs in house mice; in contrast, the average splenic mass of house mice was approximately three times that of prairie voles. These data may be relevant to seasonal changes in immune function and survival.

Spontaneous and radiation-induced micronuclei in erythrocytes from four species of wild rodents: a comparison with CBA mice

Almost 100 animals of 4 different species of small wild rodents (bank vole, Clethrionomys glareolus; field vole, Microtus agrestis; yellow-necked mouse, Apodemus flavicollis; and wood mouse, Apodemus sylvaticus) were trapped in central Sweden and used in experiments to determine the spontaneous and radiation-induced frequencies of polychromatic (fMPCE) and normochromatic erythrocytes (fMNCE) from bone marrow (bm) and peripheral blood (pb) using flow cytometric analysis. The results were compared with those from similar experiments with CBA mice. The saving of time and labour by the use of the flow cytometer-based analysis was a prerequisite for this study in which about 135 million PCE were analysed. The two species of voles had a mean background fMPCE (bm) of about the same value as CBA mice, while the yellow-necked mice had about five times higher fMPCE (bm). Wood mice had more than twice the fMPCE (bm) compared to CBA mice. Between individual animals in each of the 4 species, the background fMPCE (bm) varied more than between individual CBA mice, and the elimination of micronucleated erythrocytes was considerable. When exposed to ionizing radiation, the voles did not show a significant response. The response of the two Apodemus species was similar to that of the CBA mice, although it varied between individual animals and was not correlated to their background fMPCE. This study indicates that bank voles and field voles are unsuitable testing objects in the in vivo micronucleus assay. On the other hand, yellow-necked mice and wood mice seem to be useful in this test. Since the variation between individuals is considerable in wild Apodemus mice, large groups will be needed for obtaining statistically significant results when exposure to a genotoxic agent is low. Alternatively, repeated samples can be taken from individual wild mice to study the effect of a decreased exposure after keeping the animals for a period of time in an uncontaminated environment.

Cellular immunity is not compromised by high serum corticosterone concentrations in prairie voles

Glucocorticoids compromise immune function in glucocorticoid-sensitive species (e.g., mice), but these immunosuppressive effects may be reduced in glucocorticoid-resistant species. Prairie voles (microtus ochrogaster) have been characterized as glucocorticoid-resistant to their high circulating levels of corticosterone. Because glucocorticoid-sensitive species display suppressed lymphocyte proliferation in response to elevated blood glucocorticoid levels, proliferative values were hypothesized to be reduced in house mice (Mus musculus) compared with prairie voles. Prairie voles exhibited significantly higher splenocyte proliferative responses to the T cell mitogen, Concanavalin A, despite having higher basal total and free serum corticosterone levels than mice. Neither total nor free serum corticosterone correlated with proliferative responses from either species. These data provide further evidence for glucocorticoid resistance in prairie voles and suggest that the interactions between the hypothalamic-pituitary-adrenal axis and the immune system in prairie voles may differ from those in mice or other glucocorticoid-sensitive species. Therefore, prairie voles may serve as a valuable animal model for the syndrome of glucocorticoid resistance in humans and the role of glucocorticoids in conditions characterized by a hyperactive immune system.

Brief characterization of muskrat (Ondatra zibethicus) immunoglobulin G (IgG) separated from serum on protein A

Muskrat (Ondatra zibethicus) immunoglobulin fraction was separated from whole serum by Protein A Sepharose chromatography. In serum electrophoresis, this fraction had a gamma motility; when electrophoresed on a polyacrylamide gel with sodium dodecyl sulfate it resolved into two protein bands of approximately 52 and 25 kilodaltons, respectively. These bands were consistent with molecular weights of known heavy and light chains of immunoglobulin G (IgG) in other closely related species. Furthermore, the putative muskrat immunoglobulins had a strong cross-reactivity with mouse IgG1, IgG3, and kappa chain in an enzyme-linked immunosorbent assay. We propose, that the proteins bound to the Protein A Sepharose represent muskrat immunoglobulins of the IgG class.

Sexually dimorphic spatial learning in meadow voles Microtus pennsylvanicus and deer mice Peromyscus maniculatus

A number of studies examining developmental, neural and hormonal aspects of sexually dimorphic spatial learning (Morris water-maze) in meadow voles (Microtus pennsylvanicus) and deer mice (Peromyscus maniculatus) are described. We found that, in adult deer mice, female spatial performance decreased during the breeding season relative to the non-breeding season, whereas the reverse pattern was observed in male performance. There was a sex difference favouring males in spatial learning during the breeding season, but not during the non-breeding season. In adult meadow voles, females with low levels of oestradiol and males performed better in the water-maze than females with high levels of oestradiol. Postweaning voles (20 and 25 days after birth) acquired the water-maze task more quickly than preweaning voles (day 10). No sex difference in water-maze performance was evident at any of these juvenile ages. When these same voles were tested again as adults to investigate retention and re-acquisition of the water-maze, both males and females from male-biased litters re-acquired the task better than males and females from female-biased litters. Together, the results of these studies indicate that sexually dimorphic spatial ability is dependent on the organization (in utero) and activational effects of gonadal hormones. These studies provide the first demonstration of the influence of natural changes in reproductive status on spatial learning of deer mice and meadow voles. The results also demonstrate that spatial performance of males and females is differentially affected by changes in reproductive status and that group differences in the laboratory are associated with group differences in space utilization in the wild. These findings help to clarify previous apparently contradictory findings about sex differences in spatial ability.

Normal hematologic values of various age groups of Calomys callosus (Rodentia Cricetidae)

Hematologic values for Calomys callosus, a wild rodent, were established. Males and females from a colony raised in Animal Housing of the Institute of Tropical Medicine of São Paulo were examined individually. For the red blood cell series, the number of erythrocytes, hemoglobin concentration, hematocrit, and platelet and reticulocyte numbers were measured. All values except hemoglobin concentration were slightly higher in aged animals than in young animals. The white blood cell series had a predominance of lymphocytes, with no age-associated changes.

Photoperiodic effects on steroid negative feedback in female prairie voles (Microtus ochrogaster)

Breeding in prairie voles is mainly restricted to the autumn and winter of most years. The organization of estrus in female prairie voles is unusual because behavioral estrus is induced by chemosensory stimuli from the urine of adult conspecific males. Isolated females exhibit undetectable levels of estradiol and never display estrous behavior, yet exposure to male urine causes a cascade of endocrine changes that evoke estrogen secretion from the ovaries and estrous behavior within 24 hr. In the prairie vole, the extreme dependence of estrus on chemosensory stimuli raises the possibility that their ovaries may be less prominent in the regulation of gonadotropin secretion than in species with more endogenously organized estrous cycles. The present study examined the contribution of the ovaries in luteinizing hormone (LH) regulation in prairie voles. Females were maintained for 9 weeks in either long (LD 16:8) or short (LD 8:16) photoperiodic conditions, a blood sample was obtained, and then animals were either ovariectomized or received a sham procedure. Another blood sample was obtained a week later and assayed for serum LH. Blood serum LH levels were significantly reduced in short-day voles, compared to long-day animals. After ovariectomy both long-day and short-day voles exhibited equivalent elevations in LH levels. This study provides evidence that photoperiod is measured in female voles and the ovaries appear to produce sufficient steroids to suppress LH release.

[A quantitative morphological study of the blood system in the common field mouse and the red-backed vole living in the area of the eastern Urals radioactive trace]

A number of quantitative morphological indices of blood system of two mice-like rodent species caught in radioactive contaminated areas was studied. Certain deviation in haemopoiesis and in blood characteristics were noted. The degree of deviations was not similar in the species with different radiosensitivity. It depends most probably on the total effect of the factors influenced animals in surroundings.

[A comparative analysis of the oxygen-binding and antioxidant properties of the blood of laboratory animals and the muskrat Ondatra zibethica]

Close correlation of oxygen-binding properties of haemoglobin and the content of malonyl dialdehyde (MDA) in animal blood plasma was shown. The higher the affinity of haemoglobin to O2, the lower MDA level in the blood plasma. For the muskrat Ondatra zibethica, representing diving animals, MDA content is lower and catalase activity is higher compared with the laboratory rat.

Luteinizing hormone and prolactin in mated female meadow voles housed in long and short day lengths

Fertility differs dramatically between female meadow voles (Microtus pennsylvanicus) housed in long (LD; 14 h light/day) and short (SD; 10 h light/day) day lengths. All mated LD females ovulate, and 75-100% produce litters. In contrast, 40% of SD females that mate only after long contact with a male do not ovulate, and fertility for SD females is much lower (30-40% produce litters overall). Because copulation causes the surge in LH required for ovulation and the increase in prolactin (PRL) needed to maintain corpora lutea, we hypothesized that SD females might have lower ovulation rates and litter production because of inadequate hormonal responses. Serum LH was measured 24 h before, and 30, 60, 90, 120, and 180 min after, mating. Prolactin was measured before, and 24 and 48 h after, copulation. LD and SD females that ovulated demonstrated a sharp increase in LH levels at 30 and 60 min post mating, but LH in non-ovulating females was approximately 50% lower than that of ovulating females at 30 and 60 min post mating. PRL in LD females was double baseline levels at 24 and 48 h after mating. PRL in SD females increased at 24 h, but declined to pre-mating levels by 48 h post mating. These data suggest that reduced fertility in short day lengths in female voles may be related to two separate problems: 1) The rise in LH following copulation is insufficient in some females to cause ovulation. 2) PRL may not remain elevated long enough to support functional corpora lutea in some females that ovulate.

Modifications of a cholinesterase method for determination of erythrocyte cholinesterase activity in wild mammals

A method to determine erythrocyte cholinesterase (ChE) activity was modified for use in wild mammals. Erythrocyte ChE of California voles (Microtus californicus) was primarily acetylcholinesterase (AChE), which was similar to the brain and unlike plasma which was primarily butyrylcholinesterase (BChE). Triplicate erythrocyte AChE analyses from individual animals of several species of wild rodents revealed a mean coefficient of variation of 8.7% (SD = 4.3%). Erythrocyte ChE activity of several wild mammals of California revealed that mule deer (Odocoileus hemionus) had the highest erythrocyte AChE activity (1,514.5 mU/ml) and dusky-footed woodrats (Neotoma fuscipes) had the lowest activity (524.3 mU/ml). No ChE activity was found in erythrocytes of several species of birds and fish.

Blood gases, pH and hematology of montane and lowland coot embryos

Blood gases, air cell-blood gas differences, blood pH, and hematology were compared in embryonic coots (Fulica americana peruviana) at 4150 m and sea level in Peru. Neither arterialized nor venous O2 tensions differed significantly between montane and lowland groups but blood CO2 tensions of the two groups differed significantly. The air cell PO2-arterialized blood PO2 difference of montane eggs was less than half the value in lowland eggs. Both arterialized and venous CO2 tensions differed substantially between montane and lowland groups. Despite these differences, plasma pH at both altitudes was statistically indistinguishable, due in part to variation in plasma [HCO3-]. Hematocrits of montane embryos were significantly higher than that of their lowland counterparts.