Murine gammaherpesvirus (MuGHV) is a natural pathogen of wild rodents that has been studied extensively in terms of host immune responses to herpesviruses during acute infection, latency, and reactivation from latency. Although herpesvirus infections in people can be associated with fatigue and excessive sleepiness during both acute and latent infection, MuGHV has not been assessed extensively as a model for studying the behavioral consequences of chronic latent herpesvirus infections. To assess MuGHV infection as a model for evaluating fatigue and assessing potential mechanisms that underlie the exacerbation of fatigue during chronic viral disease, we evaluated sleep, temperature, and activity after exposure of healthy and latently MuGHV-infected mice to sleep fragmentation and social interaction. Neither treatment nor infection significantly affected temperature. However, at some time points, latently infected mice that underwent sleep fragmentation had less locomotor activity and more slow-wave sleep than did mice exposed to social interaction. In addition, delta-wave amplitude during slow-wave sleep was lower in infected mice exposed to sleep fragmentation compared with uninfected mice exposed to the same treatment. Both reduced locomotor activity and increased time asleep could indicate fatigue in infected mice after sleep fragmentation; reduced delta-wave amplitude during slow-wave sleep indicates a light plane of sleep from which subjects would be aroused easily. Identifying the mechanisms that underlie sleep responses of mice with chronic latent MuGHV infection may increase our understanding of fatigue during infec- tions and eventually contribute to improving the quality of life for people with chronic viral infections.
Many people in our society experience curtailment and disruption of sleep due to work responsibilities, care-giving, or life style choice. Delineating the health effect of acute and chronic disruptions in sleep is essential to raising awareness of and creating interventions to manage these prevalent concerns. To provide a platform for studying the health impact and underlying pathophysiologic mechanisms associated with inadequate sleep, we developed and characterized an approach to creating chronic disruption of sleep in laboratory mice. We used this method to evaluate how 3 durations of sleep fragmentation (SF) affect sleep recuperation and blood and lung analyte concentrations in male C57BL/6J mice. Mice housed in environmentally controlled chambers were exposed to automated SF for periods of 6, 12, or 24 h or for 12 h daily during the light (somnolent) phase for 4 sequential days. Sleep time, slow-wave amplitude, or bout lengths were significantly higher when uninterrupted sleep was permitted after each of the 3 SF durations. However, mice did not recover all of the lost slow-wave sleep during the subsequent 12- to 24-h period and maintained a net loss of sleep. Light-phase SF was associated with significant changes in serum and lung levels of some inflammatory substances, but these changes were not consistent or sustained. The data indicate that acute light-phase SF can result in a sustained sleep debt in mice and may disrupt the inflammatory steady-state in serum and lung.
This overview and data-based example indicate how large families of recombinant inbred (RI) strains can be used to identify genetic loci and genes that underlie complex phenotypic differences among inbred mice. The RI approach requires no a priori expectations or assumptions about mechanisms that influence the phenotype, other than that variability is partly heritable. RI strains, which are produced by inbreeding the F2 progeny of two parental strains for at least 20 generations, have two major advantages. First, numerous subjects with identical genotypes can be analyzed to determine the average phenotype associated with that genotype, and second, it becomes practical to systematically accumulate large genome and phenome data sets for entire RI families, including sequence data, transcriptomes for many organs, and cell types and extensive data on gene-by-pathogen interactions. This enables the construction of far more sophisticated models of disease cause and progression. To illustrate the use of the systems genetics approach to infectious disease, we designed a simple study using three complementary families of RI strains (CXB, BXD, and AXB/BXA) that are differentially susceptible to intravenous challenge with the yeast Candida albicans.
The use of in vitro models of complex in vivo systems has yielded many insights into the molecular mechanisms that underlie normal and pathologic physiology. However although the reduced complexity of these models is advantageous with regard to some research questions, the simplification may obscure or eliminate key influences that occur in vivo. We sought to examine this possibility with regard to the lungs response to infection, which may be inherent to resident lung cells or related to the systemic response to pulmonary infection. We used the inbred mouse strains C57BL/6J, DBA/2J, and B6.129S2-IL6(tm1Kopf), which differ in their response to inflammatory and infectious challenges, to assess in vivo responses of lung to surrogate viral and bacterial infection and compared these with responses of cultured lung slices and human A549 cells. Pulmonary cytokine concentrations were measured both after in vivo inoculation of mice and in vitro exposure of lung slices and A549 cells to surrogate viral and bacterial infections. The data indicate similarities and differences in early lung responses to in vivo compared with in vitro exposure to these inflammatory substances. Therefore, resident cells in the lung appear to respond to some challenges in a strain-independent manner, whereas some stimuli may elicit recruitment of peripheral inflammatory cells that generate the subsequent response in a genotype-related manner. These results add to the body of information pointing to host genotype as a crucial factor in mediating the severity of microbial infections and demonstrate that some of these effects may not be apparent in vitro.
The development of so-called "sickness behaviors" (e.g., anorexia, anhedonia, reduced social interaction, fatigue) during infectious and inflammatory disease has been linked to facets of the immune response. Such problems can be particularly troublesome during chronic latent infection, as the host immune system must employ continual vigilance to maintain viral latency. Epstein-Barr virus (EBV) is a ubiquitous human gamma-herpesvirus that causes acute disease and establishes life-long latency in people. Murine gammaherpesvirus (MuGHV) is a natural pathogen of wild rodents that provides an experimental model for studying the pathophysiology of an EBV-like gamma-herpesvirus in mice. To evaluate this model with regard to sickness behavior and its exacerbation during a chronic latent viral disease, we exposed uninfected and MuGHV-infected C57BL/6J and BALB/cByJ mice to novel and potentially stressful environmental perturbations and measured the impact of these challenges on behavior and markers of inflammation. The data indicate that exposure of mice to environmental perturbations during the normal somnolent phase is associated with reduced activity during the subsequent active phase, despite an intervening rest period. Effects on inflammatory mediators were complex due to independent and interactive effects of infection status, mouse strain, and exposure to stressful environment. However, GCSF and MCP1 were consistently elevated in lung both immediately after and 12h after exposure to a "dirty" cage containing the resident mouse (DCR); this increase occurred in both C57BL/6J and BALB/cByJ mice and was independent of infection status. At 12h after DCR, IL1? and IP10 were also consistently elevated in lung. In response to DCR, BALB/cByJ mice showed a greater number of significant cytokine effects than did C57BL/6J mice. With regard to infection status, IP10 was consistently elevated in lung at both time points regardless of mouse strain or DCR exposure. Several analytes were affected by mouse strain in serum or lung at one or both time points, with most strain differences present in serum at E18. Taken together, the data show that exposure of mice to environmental perturbations is associated with systemic inflammation that is in part independent of genetic background or latent MuGHV infection and with reduced activity that could represent fatigue, depression, or other facets of sickness behavior.
Ginseng is a widely consumed aromatic herb that is purported to have health benefits. Several studies report a beneficial impact of ginseng or its derivatives on Candida albicans infection in mice and suggest that its immune-modulatory properties contribute to this effect. However, these studies generally administered ginseng to experimental animals by injection, whereas people typically ingest ginseng. Furthermore, although disseminated candiasis is typically a disease of immune-impaired hosts, previous studies have generally used immune competent host species in the assessments.
Many studies of influenza severity have focused on viral properties that confer virulence, whereas the contributory role of the host genetic background on infection severity remains largely unexplored. In this study, we measure the impact of inoculation with influenza virus in four strains of inbred mice - BALB/cByJ, C57BL/6J, A/J, and DBA/2J. To evaluate the extent to which responses are inherent to lung per se, as opposed to effects of the systemic response to lung infection, we also measured cytokines and chemokines in lung slices exposed to the virus in vitro. Finally, we evaluate the in vivo responses of recombinant inbred (RI) and select consomic strains of mice to search for genomic loci that contribute to phenotypic variance in response to influenza infection. We found marked variation among mouse strains after challenge with virus strain A/HKX31(H3N2), consistent with previous reports using more virulent strains. Furthermore, response patterns differ after in vivo versus in vitro exposure of lung to virus, supporting a predominant role of the systemic host inflammatory response in generating the strain differences. These results add to the body of information pointing to host genotype as a crucial factor in mediating the severity of influenza infections.
Fatigue and disturbed sleep are common problems for cancer patients and affect both quality of life and compliance with treatment. Fatigue may be associated with cancer itself and with the treatment, particularly for therapies with neurotoxic side effects. To develop a model system for evaluation of chemotherapy-related fatigue, we studied mice treated with either a commonly used formulation of the chemotherapeutic agent paclitaxel (paclitaxel; Taxol), which is known to have neurotoxic properties, or a nano- particle formulation of paclitaxel (nab-paclitaxel; Abraxane) that is reported to have greater potency and efficacy yet fewer side effects than does paclitaxel. Mice were treated with 1 of these 2 agents (10 mg/kg IV daily for 5 consecutive days) and were monitored from 1 wk before through 4 wk after treatment. Dependent measures included running wheel activity, locomotor activity on the cage floor, core temperature, sleep patterns, CBC count, serum cytokine and chemokine concentrations, and neurologic assessment. For both drugs, mice showed the most severe perturbations of activity during the first recovery week after drug administration. Mice treated with paclitaxel showed greater neutropenia and motor deficits than did mice treated with nab-paclitaxel. However, deficits had largely resolved by 4 wk after administration of either drug. We conclude that these measures provide an assessment of chemotherapy-related fatigue that potentially can distinguish toxicity associated with different formulations of the same agent.
Our goal in this study was to identify objective criteria that could be used to predict an outcome of death in mice subjected to experimental inoculation with infectious organisms. We conducted a retrospective analysis of data collected from 4 independent studies that used several infectious agents (influenza virus strains A/HK/x31[H3N2] and A/Puerto Rico/8/34[H1N1], Streptococcus pneumoniae, and Candida albicans) and mouse strains (A/J, DBA/2J, C57BL/6J, BALB/cByJ). Postinoculation periods ranged from 5 to 21 d, with survival of 30% to 60% of the subjects. In all studies, mice were implanted with either a subcutaneous identification microchip or an intraabdominal radiofrequency transmitter to allow remote measurement of body temperature. After inoculation, mice were weighed and monitored regularly until death occurred or euthanasia was performed. Hypothermia was the most valuable characteristic for distinguishing mice that would survive or succumb to the infection. In addition, weight loss was useful in some of the models. In some cases, the derived measure of the product of temperature and body weight provided the best differentiation of mice in the 2 outcome categories. Therefore, the utility of these measures varied substantially depending on the specific model. This study demonstrates that specific endpoint markers are not uniformly applicable to different models. Rather, such markers should be developed and tested in the context of the model in which they will be used. The use of validated markers for eventual death can signal the need for preemptive euthanasia to alleviate terminal distress and permit timely collection of biologic samples.
The nucleotide substitution C797T in the Chrm2 gene causes substitution of leucine for proline at position 266 (P266L) of the CHRM2 protein. Because Chrm2 codes for the type 2 muscarinic receptor, this mutation could influence physiologic and behavioral phenotypes of mice. Chrm2 mRNA was not differentially expressed in 2 brain regions with high cholinergic innervation in a mouse strain that does (BALB/cByJ) or does not (C57BL/6J) have the mutation. In addition, strains of mice with and without the C797T point mutation in Chrm2 did not differ significantly in muscarinic binding properties. Variation across strains was detected in terms of acoustic startle, prepulse inhibition, and the physiologic effects of the muscarinic agonist oxotremorine. However, interstrain differences in these measures did not correlate with the presence of the mutation. Although we were unable to associate a measurable phenotype with the Chrm2 mutation, assessment of the mutation on other genetic backgrounds or in the context of other traits might reveal differential effects. Therefore, despite our negative findings, evaluation of characteristics that involve muscarinic function should be undertaken with caution when comparing mice with different alleles of the Chrm2 gene.
The goal of this study was to identify objective criteria that would reliably predict imminent death in aged mice. Male and female ICR mice (age, 8 mo) were subcutaneously implanted with an identification chip for remote measurement of body temperature. Mice then were weighed and monitored regularly until spontaneous death occurred or until euthanasia was administered for humane reasons. Clinical signs that signaled implementation of euthanasia included inability to walk, lack of response to manipulation, large or ulcerated tumors, seizures, and palpable hypothermia. In mice that died spontaneously, gradual weight loss was the most frequent and earliest sign of imminent death. Hypothermia developed during the 2 wk prior to death. Slow or labored breathing were observed in about half of the mice before death. A composite score of temperature x weight can be used to provide an objective benchmark to signal increased observation or euthanasia of individual mice. Such assessment may allow the collection of terminal tissue samples without markedly altering longevity data, although application of this criterion may not be appropriate for all studies of longevity. Timely euthanasia of mice based on validated markers of imminent death can allow implementation of endpoints that alleviate terminal distress in aged mice, may not significantly affect longevity data, and can permit timely collection of biologic samples.
Mite infestation of mice remains a persistent problem for many institutions, leading to numerous health problems and creating unknown and unwanted variables for research. In this study, mice with mite infestation demonstrated significantly higher levels of inflammatory cytokines, both at draining lymph nodes (axillary) and systemically, as compared with mice without mites. In addition, histologic evaluation revealed significant inflammation in mite-infested mice. Inflammatory changes were still present in the skin of mice at 6 to 8 wk after treatment, despite absence of detectable infestation at that time. Because these significant and lasting local and systemic changes have the potential to alter research findings, eradication of mites infestations should be an important goal for all institutions.
Our previous work revealed that mice lacking the p50 subunit of transcription factor nuclear factor kappa B (NF-kappaB) (p50 KO mice) and genetically intact F2 mice have similar locomotion under basal conditions, yet p50 KO mice show greater locomotor activation after caffeine ingestion. In this report, we test whether KO mice display altered caffeine pharmacokinetics or increased caffeine-induced DA turnover relative to F2 mice, and evaluate the impact of intraperitoneal administration of specific adenosine and DA receptor antagonists on locomotor activity.
The goal of this pilot study was to determine the magnitude and direction of intervention effect sizes for inflammatory-related serum markers and relevant health outcomes among breast cancer survivors (BCSs) receiving a physical activity behavior change intervention compared with usual care.
The goal of this study was to identify objective criteria that would reliably predict spontaneous death in aged inbred mice. We evaluated male and female AKR/J mice, which die at a relatively young age due to the development of lymphoma, as well as male C57BL/6J and BALB/cByJ mice. Mice were implanted subcutaneously with an identification chip that also allowed remote measurement of body temperature. Temperatures and body weights were measured weekly until spontaneous death occurred or until euthanasia was performed for humane reasons. In AKR/J mice, hypothermia and weight loss began about 4 wk prior to death and increased gradually during that antemortem interval. In C57BL/6J and BALB/cByJ mice, these declines began earlier and were more prolonged prior to death. However, C57BL/6J and BALB/cByJ mice developed a relatively precipitous hypothermia during the 2 wk prior to death. For all 3 strains, the derived composite score of temperature × weight, expressed as a percentage of stable values for each mouse, was similarly informative. These changes in individual and composite measures can signal the need for closer observation or euthanasia of individual mice. Validated markers of clinical decline or imminent death can allow the use of endpoints that reduce terminal distress, do not significantly affect longevity or survival data, and permit timely collection of biologic samples.
Examine mediators of fatigue response to an exercise intervention for breast cancer survivors (BCS) in a pilot randomized controlled trial.
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