Gene expression in lung and basal forebrain during influenza infection in mice

Inbred mice develop strain-dependent changes in sleep during the first few days after inoculation with influenza virus. To identify genes with the potential to differentially modulate sleep under this condition, we performed complementary DNA microarray analysis of both lung and basal forebrain (BF) of infected (I) and uninfected BALB/cByJ (C) and C57BL/6J (B6) mice. This analysis showed significant variation in the expression pattern of 667 and 1217 of the surveyed genes in BF and lung, respectively (P < 0.01). Applying the additional criterion of an effect size >or=2, 495 genes differed in expression in lung compared with 204 in BF. In BF, more genes were differentially expressed as a function of mouse strain, whereas in lung, more genes were differentially expressed as a function of health status. Significant alterations in expression after infection were more numerous and robust in BALB/cByJ vs. C57BL/6J mice. Some genes showed significant variation in both tissues as a function of strain or condition, but the changes in general were not parallel. Genes that showed significant and robust variation as a function of strain, health status or tissue included those related to immune function, metabolism, signal transduction, cell cycle regulation, apoptosis and other miscellaneous categories. Different patterns of gene expression in BF of uninfected mice suggest the possibility of fundamental mechanistic differences in pathways that modulate vigilance in these strains, whereas differences in expression of lung of infected mice suggests different peripherally generated sleep-modulatory stimuli in the two strains.

Effect of environmental temperature on sleep, locomotor activity, core body temperature and immune responses of C57BL/6J mice

Ambient temperature exerts a prominent influence on sleep. In rats and humans, low ambient temperatures generally impair sleep, whereas higher temperatures tend to promote sleep. The purpose of the current study was to evaluate sleep patterns and core body temperatures of C57BL/6J mice at ambient temperatures of 22, 26 and 30 degrees C under baseline conditions, after sleep deprivation (SD), and after infection with influenza virus. C57BL/6J mice were surgically implanted with electrodes for recording electroencephalogram (EEG) and electromyogram (EMG) and with intraperitoneal transmitters for recording core body temperature (T(c)) and locomotor activity. The data indicate that higher ambient temperatures (26 and 30 degrees C) promote spontaneous slow wave sleep (SWS) in association with reduced delta wave amplitude during SWS in C57BL/6J mice. Furthermore, higher ambient temperatures also promote recuperative sleep after SD. Thus, in mice, higher ambient temperatures reduced sleep depth under normal conditions, but augmented the recuperative response to sleep loss. Mice infected with influenza virus while maintained at 22 or 26 degrees C developed more SWS, less rapid eye movement sleep, lower locomotor activity and greater hypothermia than did mice maintained at 30 degrees C during infection. In addition, despite equivalent viral titers, mice infected with influenza virus at 30 degrees C showed less leucopenia and lower cytokine induction as compared with 22 and 26 degrees C, respectively, suggesting that less inflammation develops at the higher ambient temperature.

Spontaneous, homeostatic, and inflammation-induced sleep in NF-kappaB p50 knockout mice

The dimeric transcription factor nuclear factor-kappaB (NF-kappaB) regulates several endogenous sleep-modulatory substances and thereby serves as a pivotal mediator of sleep-wake homeostasis. To further define the role of NF-kappaB in sleep regulation, we monitored sleep and temperature in mice that lack the p50 subunit of NF-kappaB [p50 knockout (KO) mice]. Compared with the control B6129PF2/J strain, p50 KO mice spend more time in slow-wave sleep (SWS) and rapid eye movement sleep (REMS) under normal conditions and show enhanced homeostatic recovery of sleep after sleep loss. p50 KO mice also show increased SWS and reduced REMS and temperature after the administration of lipopolysaccharide, yet they are behaviorally less responsive to challenge with influenza virus. These data support a role for NF-kappaB, and, in particular, for the p50 subunit, in the regulation of sleep in healthy mice and in mice experiencing immune challenge.

Strain differences in sleep patterns of healthy and influenza-infected inbred mice

Influenza-infected C57BL/6J and BALB/cByJ mice respectively develop increased slow-wave sleep (SWS) during the dark phase and reduced SWS during the light phase of the 24 hour circadian cycle. To determine whether similar or alternative variations in SWS develop after influenza infection in other inbred strains of mice, we characterized the sleep patterns of additional strains both before and after influenza infection. Three strains (A/J, BALB/cByJ, and C3H/HeJ) showed light-phase SWS suppression, two strains (C57BL/6J and DBA/2J) showed dark-phase SWS enhancement, and one strain (A/J) showed dark-phase SWS suppression. Three strains (AKR/J, C57BR/cdJ, and FVB/NJ) did not show significant changes in SWS time on day two post-inoculation. Core temperatures were correlated to change in SWS time after infection, but were not correlated to SWS during the baseline period. These data support and expand the existing literature that indicates genetic modulation of sleep both in healthy mice and in mice undergoing viral infection.

Kissimmee River restoration: a case study

Channelization of the Kissimmee River transformed a 167 km meandering river into a 9 metre deep, 75 metre wide, 90 km drainage canal (C-38) that is compartmentalized with levees and water control structures into a series of five stagnant pools. Channelization dramatically changed water level and flow characteristics, drained 21,000 hectares of floodplain wetlands and severely impacted fish and wildlife populations. A $500 million dollar restoration project will restore the ecological integrity of the river-floodplain system by reconstructing the natural river channel and reestablishing hydrologic processes. Sixty expectations have been established to quantify the ecosystem's recovery. The first phase of reconstruction was completed in February 2001 and included movement of 9.2 million cubic metres of earth to backfill 12 km of C-38, the explosive demolition of one water control structure, construction of two sections (2.4 km) of new river channel, and reestablishment of 24 contiguous km of river. Numerous social, political, and technical challenges have been encountered during the project's evolution. Recommendations are provided for future restoration projects.

Persistent transmission of mouse hepatitis virus by transgenic mice

Variation in susceptibility to viral infection is well documented across mouse strains. Specific combinations of viral strains and murine hosts may favor viral infection and disease, and could potentially allow the unexpected development of chronic, persistent, or latent infections. In some genetically modified strains of mice, immune function and perhaps other physiologic or metabolic systems may be substantially or marginally impaired. In the case study reported here, we document the apparent persistent transmission of mouse hepatitis virus (MHV) over a two-year period by MHV-seropositive transgenic mice. Transmission occurred via direct contact with seropositive mice and exposure to contaminated bedding. However, MHV was not detected at diagnostic laboratories by use of viral isolation or reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of tissues from MHV-seropositive animals. Our observation, together with the constantly expanding varieties of immune-impaired or poorly characterized murine hosts and the burgeoning dissemination of these animals throughout the biomedical research community, indicate that unexpected pathophysiologic presentations of common murine viral diseases may present new challenges to the biomedical research community in the future.

Cytokine- and microbially induced sleep responses of interleukin-10 deficient mice

Interleukin (IL)-1 and tumor necrosis factor (TNF) promote slow-wave sleep (SWS), whereas IL-10 inhibits the synthesis of IL-1 and TNF and promotes waking. We evaluated the impact of endogenous IL-10 on sleep-wake behavior by studying mice that lack a functional IL-10 gene. Under baseline conditions, C57BL/6-IL-10 knockout (KO) mice spent more time in SWS during the dark phase of the light-dark cycle than did genetically intact C57BL/6 mice. The two strains of mice showed generally comparable responses to treatment with IL-1, IL-10, or influenza virus, but differed in their responses to lipopolysaccharide (LPS). In IL-10 KO mice, LPS induced an initial transient increase and a subsequent prolonged decrease in SWS, as well as profound hypothermia. These responses were not observed in LPS-treated C57BL/6 mice. These data demonstrate that in the absence of endogenous IL-10, spontaneous SWS is increased and the impact of LPS on vigilance states is altered. Collectively, these observations support a role for IL-10 in sleep regulation and provide further evidence for the involvement of cytokines in the regulation of sleep.

Identifying genetic influences on sleep: an approach to discovering the mechanisms of sleep regulation

Comparisons of sleep patterns of various inbred strains of mice have revealed differences in daily amounts of slow-wave sleep and rapid-eye movement sleep, in circadian patterns of sleep, and in some parameters of the electroencephalograms both in healthy mice and in mice undergoing microbial infections. Technical considerations will probably be an important variable in achieving consensus between different independent studies that use a genetic approach to identify sleep-regulatory genes or mechanisms. However, despite such differences, current data suggest that both normal sleep and various sleep disorders either have a genetic basis or are influenced by genetically determined physiologic or environmental predispositions. Excessive sleepiness, abnormal sleep patterns, nonrestorative sleep, and fatigue are becoming increasingly pervasive in modern society. Identifying genes that influence vigilance may ultimately contribute to a better understanding of the processes that control normal sleep and contribute to sleep disorders and may eventually promote the development of interventions to prevent or alleviate these disabling medical conditions.

Food and water restriction protocols: physiological and behavioral considerations

Food and water restriction protocols are common in animal research, yet they often elicit discussion and controversy among institutional animal care and use committee members who review them. Determining a single standard by which all restriction protocols can be evaluated or performed may not be realistic. However, information about the physiologic and behavioral impact of food and water restriction can provide a basis for making rational judgments about these issues in general. This review will discuss the physiologic and behavioral consequences of food or water deprivation periods of 24 h or less and of chronic restriction schedules, with special reference to protocols that use food or water restriction as a motivational tool for behavioral training.

An evaluation of analgesic regimens for abdominal surgery in mice

This study was designed to evaluate the efficacy of several analgesic regimens for use after intraperitoneal implantation of telemetry transmitters in mice. The lengths of time required for postoperative recovery of food and water intake, locomotor activity, and core temperature of mice that did not receive postsurgical analgesic medication were compared to those of mice that were given either an analgesic in the drinking water or buprenorphine injections. Many measured variables were not substantially altered by analgesic medications. However, ibuprofen-treated mice demonstrated significantly greater locomotor activity on days 2 through 5 after surgery and a more rapid return to stable postsurgical levels of activity and water intake as compared to those in untreated mice. These changes are consistent with potential analgesic efficacy of the ibuprofen treatment regimen. Buprenorphine injections elicited hyperactivity, hyperthermia, and reduced food and water intake during both the immediate postsurgical recovery period and after apparent recuperation from surgery, as compared to effects observed in saline-treated mice. Evaluating the effect of analgesic regimens on postsurgical changes in physiologic and behavioral variables can be useful in assessing the efficacy of analgesic treatments, but some changes may indicate pharmacologic effects that do not reflect pain relief.

Systemic bacterial invasion induced by sleep deprivation

Profound sleep disruption in humans is generally believed to cause health impairments. Through comparative research, specific physical effects and underlying mechanisms altered by sleep deprivation are being elucidated. Studies of sleep-deprived animals previously have shown a progressive, chronic negative energy balance and gradual deterioration of health, which culminate in fatal bloodstream infection without an infectious focus. The present study investigated the conditions antecedent to advanced morbidity in sleep-deprived rats by determining the time course and distribution of live microorganisms in body tissues that are normally sterile. The tissues cultured for microbial growth included the blood, four major organs, six regional lymph nodes, the intestine, and the skin. The principal finding was early infection of the mesenteric lymph nodes by bacteria presumably translocated from the intestine and bacterial migration to and transient infection of extraintestinal sites. Presence of pathogenic microorganisms and their toxins in tissues constitutes a septic burden and chronic antigenic challenge for the host. Bacterial translocation and pathogenic sequelae provide mechanisms by which sleep deprivation appears to adversely affect health.

Evaluation of an anesthetic regimen for retroorbital blood collection from mice

Many Institutional Animal Care and Use Committees require anesthetization of mice for retroorbital blood collection procedures. Optimal anesthetic regimens should provide chemical restraint and adequate analgesia for a sufficient but otherwise minimal duration. This study was conducted to evaluate the effectiveness, safety, and practical utility of the general anesthetic combination of ketamine and medetomidine with and without the topical anesthetic proparacaine. In addition, we sought to evaluate the reversal of general anesthesia with atipamezole. The findings suggest that the combination of ketamine, medetomidine, proparacaine, and atipamezole is a safe and humane anesthetic regimen for retroorbital collection of blood samples from mice.

Lipopolysaccharide effects on neuronal activity in rat basal forebrain and hypothalamus during sleep and waking

Peripheral administration of lipopolysaccharide (LPS) is associated with alterations in sleep and the electroencephalogram. To evaluate potential neuronal mechanisms for the somnogenic effects of LPS administration, we used unanesthetized rats to survey the firing patterns of neurons in various regions of rat basal forebrain (BF) and hypothalamus during spontaneous sleep and waking and during the epochs of sleep and waking that occurred after the intraperitoneal administration of LPS. In the brain regions studied, LPS administration was associated with altered firing rates in 39% of the neurons examined. A larger proportion of LPS-responsive units showed vigilance-related alterations in firing rates compared with nonresponsive units. Approximately equal proportions of LPS-responsive neurons showed increased and decreased firing rates after LPS administration, with some units in the lateral preoptic area of the hypothalamus showing particularly robust increases. These findings are consistent with other studies showing vigilance-related changes in neuronal activity in various regions of BF and hypothalamus and further demonstrate that peripheral LPS administration alters neuronal firing rates in these structures during both sleep and waking.

Toxicity evaluation of prophylactic treatments for mites and pinworms in mice

The detection of external and internal parasites in laboratory mice is a particularly problematic aspect of animal health evaluation. Because these organisms must be detected by direct examination of the feces or hair coat, low-level infestation or sporadic shedding can make them difficult to detect, thereby undermining confidence that negative reports are truly negative. Prophylactic treatment of suspect colonies with anthelminthics and/or insecticides may therefore be indicated under some circumstances. However, when considering the use of prophylactic treatments, the potential for toxicity is an important factor, especially in genetically modified strains of mice. To evaluate the potential toxicity of prophylactic anti- parasitic treatments on strains of mice that are commonly used as experimental models and in genetic engineering in our facility, we surveyed a number of strains and ages of mice for toxic reactions during treatment regimens that combine anthelminthic and anti-acaricidal agents. Three experimental protocols (ivermectin, piperazine, and dichlorvos in combination; ivermectin alone; and fenbendazole/permethrin or fenbendazole/dichlorvos) were evaluated. Our data suggest a potential for toxicity associated with these treatments and indicate to us that prophylactic treatment regimens should be initiated with caution.

A quantitative genetic analysis of slow-wave sleep in influenza-infected CXB recombinant inbred mice

Influenza-infected C57BL/6J mice spend increased amounts of time in slow-wave sleep (SWS) during the dark phase of the circadian cycle compared to healthy mice. In contrast, infected BALB/cByJ mice show a normal or reduced time in SWS, particularly during the light phase. To identify genetic loci with linkage to these traits, we measured sleep in 13 CXB recombinant inbred (RI) strains derived from a cross between C57BL/6ByJ and BALB/cByJ mice. The probability density distribution of sleep patterns of influenza-infected CXB RI mice showed modes that correspond roughly with the parental modes during the dark phase of the circadian cycle and are intermediate or C57BL/6-like during the light phase. These patterns are consistent with the presence of a low number of major effect quantitative trait loci (QTLs). Chromosomal regions with provisional association to strain variation in influenza-induced SWS patterns were identified. In particular, a 10- to 12-cM interval on Chr 6 between D6Mit74 and D6Mit188 contains a QTL (LRS = 16.6 at 1 cM proximal to D6Mit316; genomewide p < .05) that influences the SWS response to influenza infection during the light phase. We have provisionally named this QTL Srilp1 (sleep response to influenza, light phase 1). Candidate genes for mediation of this phenotype include Ghrhr (growth hormone releasing hormone receptor), Crhr2 (corticotropin releasing hormone receptor 2), and Cd8a (an epitope on cytotoxic T lymphocytes). Several other intervals achieved suggestive probability scores that are sufficient to warrant further analysis either with additional RI strains or with F2 panels. The analysis also suggests that dark phase and light phase responses are regulated by different genetic factors.

A quantitative genetic analysis of locomotor activity in CXB recombinant inbred mice

Recent studies have identified genes that influence the length of the circadian period maintained by mice housed under constant lighting conditions. However, a less studied circadian activity variable is the amplitude of daily oscillations in locomotor activity. This parameter reflects spontaneous activity exhibited under standard lighting and housing conditions and, therefore, differs conceptually from assessments of exploratory or open-field activity, voluntary wheel-running, or circadian period during exposure to constant light or constant darkness conditions. We recently observed a greater daily amplitude of oscillation in spontaneous locomotor activity in C57BL/6 mice compared to BALB/cBy mice. To identify genetic loci with potential linkage to circadian variation in the amount of locomotor activity, we measured the spontaneous activity of 13 CXB recombinant inbred (RI) strains of mice. The probability density distributions of locomotor activity phenotypes for the 13 CXB RI strains were consistent with the presence of a low number of major quantitative trait loci affecting this trait. Regions of chromosomes 3, 8, 12, 13, and 19 showed provisional linkage to strain variation in locomotor activity. Probabilities of linkage were not sufficient for declaration of an activity-related quantitative trait locus but were sufficient to warrant further analysis either with additional RI strains or with F2 panels.

A quantitative genetic analysis of slow-wave sleep and rapid-eye movement sleep in CXB recombinant inbred mice

Various inbred strains of mice show different daily amounts of slow-wave sleep (SWS) and rapid-eye movement sleep (REMS), suggesting the possibility of genetic influences on sleep propensity. Previous work by others studying the spontaneous sleep patterns of seven strains of CXB recombinant inbred (RI) mice suggested several candidate quantitative trait loci (QTLs) associated with variation in REMS. Extending this approach, we evaluated the sleep patterns of 13 CXB RI strains and conducted linkage analyses based on 223 discrete informative loci. The probability density distribution of light phase REMS for the CXB RI strains showed deflections that correspond approximately to the parental phenotypes. This type of pattern is consistent with the presence of a low number of major effect quantitative trait loci. Regions of chromosomes 4, 16, and 17 showed provisional linkage to strain variation in REMS. The distribution of loci further suggested that dark phase and light phase REMS may be regulated by different genetic factors. Probabilities of linkage were not sufficient for declaration of a quantitative trait locus for REMS but were sufficient to warrant further analysis either with additional RI strains or with F2 panels.

Rodent quarantine programs: purpose, principles, and practice

In animal research, validity and reproducibility of data are critically influenced by the microbial status of the experimental animals. One of the most crucial aspects of assuring quality in animal research is providing research personnel with confidence that experimental results will not be invalidated due to interference caused by infectious disease. An effective quarantine program is essential to providing this assurance. Quarantine programs are generally instituted to prevent the introduction of rodent pathogens into established specific-pathogen-free colonies in a facility. Therefore, programs should be designed to isolate newly acquired rodents until their health status can be determined and to maximize the probability that microorganisms of interest will be detected before the animals are introduced into (and thus, could potentially contaminate) established colonies. Important principles that are critical to designing an effective quarantine program will be discussed here, as will the practical implementation of these principles. Although quarantine programs may be costly in terms of time and effort, these costs must be balanced against the potential costs of disease outbreaks that could invalidate long-term studies, alter normal biological baselines, and cause the loss or necessitate re-derivation of rare or valuable strains of rodents. Reducing the incidence of quarantine failures through appropriate program design and implementation helps to maintain the confidence of research personnel in the value of quarantine programs and in our competence as specialists in laboratory animal management and as partners in the research process.

Effects of sleep deprivation and other stressors on the immune and inflammatory responses of influenza-infected mice

Many stressors have well-documented effects on host immune competence. However, two important stressors that have not been extensively characterized in terms of their immune-modulatory properties are sleep deprivation and alterations in light:dark cycles. We therefore evaluated the effects of these stressors on the immune and inflammatory responses of mice inoculated intranasally with influenza virus. In contrast to a previous report, sleep deprivation did not significantly alter viral clearance or antibody titers of either virus-naive or immunized mice. Exposure to constant light also failed to affect these variables. However, repeated overnight restraint, a well-characterized stressor, reduced the pulmonary inflammatory response elicited by influenza virus, as previously reported. The data indicate that sleep deprivation and altered light cycles do not markedly influence selected host defense responses to influenza infection under the conditions tested.

Developmental alterations in auditory arousal from sleep in healthy and virus-infected cats

To investigate the impact of respiratory-tract infections on arousability from sleep, we evaluated the auditory arousal responses of healthy and virus-infected cats in two age groups. Arousability was positively associated with stimulus intensity but negatively associated with experimental day. Infected animals were more responsive to auditory stimuli than were uninfected ones, and younger cats were less responsive than older animals. Within the younger groups, infected cats demonstrated increased arousability across the entire range of stimulus volumes during quiet sleep but not during active sleep. Young infected cats also demonstrated lower EEG delta-wave amplitudes than did uninfected animals. These effects on arousability and EEG amplitudes were not observed in older cats. Thus, under the conditions studied, cats with mild viral infections show an age-related enhancement of auditory arousability from sleep, suggesting that they sleep less deeply than do healthy, age-matched animals. The generalization of these observations to other arousing stimuli, such as hypoxia or hypercapnia, and possible implications for the pathogenesis of sudden infant death syndrome remain to be determined.

Somnogenic and pyrogenic effects of interleukin-1beta and lipopolysaccharide in intact and vagotomized rats

The vagus nerve appears to serve a role in mediating peripheral immunologic influences on CNS processes. Previous work demonstrates that subdiaphragmatic vagotomy prevents or attenuates many of the behavioral and physiological responses to exogenous interleukin-1 (IL-1) or lipopolysaccharide (LPS). We determined whether the somnogenic effects of IL-1 and LPS were altered in vagotomized rats, and whether the effects of vagotomy on IL-1- and LPS-induced alterations in sleep would vary as a function of circadian phase. The data indicate that vagotomy does not influence the normal circadian patterns of sleep and wakefulness in untreated rats, or modify the pyrogenic or somnogenic effects of intracerebroventricular administration of IL-1. However, in unchallenged animals vagotomy reduces basal brain temperatures, increases delta wave amplitudes during slow-wave sleep (SWS), and induces a reduced rate of weight gain, gastric distension, and adrenal hypoplasia. Vagotomy attenuates the febrile effects of IL-1 during both light and dark phases, attenuated IL-1-induced sleep enhancement during the dark phase, and attenuated IL-1-induced increases in delta wave amplitudes within SWS during the light period. In LPS-treated rats, vagotomy attenuates the febrile and SWS responses to LPS after administration at light onset, but not after administration at dark onset. These results indicate that subdiaphragmatic vagotomy attenuates several of the somnogenic and pyrogenic effects of IL-1beta and LPS, although the effectiveness of the vagal transection in modulating these responses is influenced by circadian factors.

EEG delta power and auditory arousal in rested and sleep-deprived rabbits

Slow-wave activity in the electroencephalogram is thought to reflect the depth or intensity of sleep. This hypothesis is primarily derived from studies of rats or humans. However, some characteristics of sleep of rabbits differ from those of rats or humans. To determine whether slow-wave activity (power density in the delta frequency band of 0.5-5.0 Hz) correlates with arousability in rabbits, we presented auditory stimuli (72-90 dB) to control or sleep-deprived animals during slow-wave sleep. The resulting behavioral responses, defined by changes in eye state and body posture, and the latency to return to sleep were used as measures of arousability. Behavioral responsiveness to auditory stimuli increased with increasing stimulus intensity in both control and sleep-deprived animals. Overall, however, sleep-deprived animals exhibited fewer postural changes and eye openings than did control rabbits. Sleep-deprived rabbits also more rapidly returned to sleep after the stimulus presentation than did control animals. Latency to return to sleep was correlated with delta power before stimulus presentation, but behavioral responsiveness was not. These data suggest that, in this rabbit model, delta power may not be predictive of behavioral arousability but may reflect sleep propensity.

Strain differences in the somnogenic effects of interferon inducers in mice

Increased slow-wave sleep accompanies influenza infection in C57BL/6 mice but not BALB/c mice. These strains of mice possess different alleles of the genetic lucus If-1, which codes for high (If-1h; C57BL/6) and low (If-1(1); BALB/c) production of interferon (IFN), a putative sleep-inducing cytokine. To evaluate the contribution of the If-1 gene to differences in murine sleep propensity, sleep patterns were evaluated in mice treated with the IFN inducers polyinosinic:polycytidilic acid (pIC) or Newcastle disease virus (NDV), with influenza virus, or with murine interferon (IFN-alpha) or IFN-alpha/beta. As compared with baseline values, C57BL/6 mice exhibited increased slow-wave sleep after all three challenges, but BALB/c mice did not. Congenic B6.C-H28c mice, which bear the BALB/c allele for low IFN production on the C57BL/6 genetic background, showed enhanced slow-wave sleep after influenza infection but not after NDV. Exogenous IFN did not enhance slow-wave sleep in either C57BL/6 or BALB/c mice. These data suggest that the If-1 allele may influence the somnogenic responsiveness of mice under some conditions but that additional mechanisms may contribute to sleep enhancement during infectious disease.

Evaluation of anaesthetic regimens in guineapigs

To establish reliable methods of chemical restraint and anaesthesia for mildly painful procedures in guineapigs, we compared the effects of the following anaesthetics and combinations of anaesthetics: tiletamine-zolazepam (two dosages), pentobarbital, methoxyflurane, ketamine-xylazine (three dosages), and ketamine-xylazine with methoxyflurane. Tiletamine-zolazepam induced a short period of chemical restraint but lacked analgesic effects at the doses tested. Although pentobarbital induced prolonged chemical restraint, the loss of responsiveness to painful stimuli was brief. Methoxyflurane alone induced transient anaesthesia and analgesia. Ketamine-xylazine combinations induced analgesia and chemical restraint of comparable durations, and some dosages were suitable for mildly painful procedures. The addition of methoxyflurane significantly potentiated the anaesthetic and analgesic properties of the high dosage ketamine-xylazine combination.

Lighting conditions alter Candida albicans-induced sleep responses in rabbits

To evaluate the influence of light on sleep patterns after microbial challenge, we studied rabbits housed in 12:12-h light-dark (LD), constant light (LL), or constant darkness (DD) before and after intravenous Candida albicans inoculation. Compared with the LD group, uninoculated LL rabbits sporadically increased slow-wave sleep and delta-wave amplitudes during the circadian period previously associated with the dark phase. In contrast, uninfected DD rabbits showed reduced sleep during the circadian period previously associated with the light phase. Inoculation of LD rabbits with Candida approximately 2 h after light onset increased slow-wave sleep and delta-wave amplitudes during hours 4-8 postinoculation and reduced these parameters during hours 20-46. In contrast, Candida-inoculated LL rabbits demonstrated increased slow-wave sleep for up to 28 h after inoculation, with little subsequent reduction; delta-wave amplitudes were similar to those of LD rabbits. Candida-inoculated DD rabbits demonstrated attenuated increases in slow-wave sleep and delta-wave amplitudes, but the suppression phase was not altered. We conclude that lighting conditions modulate microbially induced sleep alterations.

Immune-modulatory drugs alter Candida albicans-induced sleep patterns in rabbits

To evaluate the influences of immune responsiveness on sleep alteration during infectious disease, sleep was monitored during Candida albicans infection in rabbits treated with immune-modulating drugs. Intravenous administration of C. albicans to normal rabbits initially increased and subsequently decreased both the amount of slow-wave sleep (SWS) and delta-wave amplitudes (DWA) during SWS. Cortisone treatment attenuated these effects. The immunosuppressive drug cyclosporine did not alter the initial enhancement of SWS, but did attenuate the C. albicans-induced reduction in SWS time and potentiate the reduction in DWA. In contrast, administration of incomplete Freund's adjuvant and prior immunization with killed C. albicans, which were expected to enhance immune responsiveness, did not markedly alter C. albicans-induced alterations in SWS. However, the immune stimulant levamisole potentiated the effects of C. albicans on SWS. These data indicate that pharmacologic treatments expected to alter immune responsiveness modulate microbially induced sleep, and are consistent with the hypothesis that facets of the immune response mediate sleep changes during infectious disease.

Strain differences in sleep and other pathophysiological sequelae of influenza virus infection in naive and immunized mice

To characterize behavioral and physiological alterations induced by viral respiratory infection, C57BL/6 and BALB/c strains of mice were monitored for 2 days before and 4 days after intranasal inoculation with influenza virus. Both strains developed hypothermia, decrease locomotor activity, and decreased delta-wave amplitude during sleep within 24 h after inoculation. However, infected C57BL/6 mice also spent more time in slow-wave sleep, but infected BALB/c mice did not. The increased SWS in C57BL/6 mice occurred during the lights-off phase of the circadian cycle, and resulted in loss of the normal circadian rhythmicity of sleep. Increased sleep also occurred after viral challenge of immunized C57BL/6 mice, but was not observed after secondary challenge of immunized BALB/c mice. These data indicate that sleep alterations may accompany viral infections in some, but not all, strains of mice. The dissimilar sleep patterns seen in C57BL/6 and BALB/c mice after influenza infection may reflect differences in their immune response to influenza virus.

Somnogenic effects of sleep deprivation and Escherichia coli inoculation in rabbits

To evaluate the impact of sleep deprivation (SD) on microbially induced alterations in sleep, we used gentle handling to deprive rabbits of sleep for 4 h before or after intravenous inoculation with Escherichia coli (EC). Sleep was monitored for the next 20 h. EC inoculation alone increased slow-wave sleep (SWS) time, delta-wave amplitude (DWA) during sleep and SWS bout length during the initial 2-4 h after inoculation. During the following 8-20 h, DWA during SWS was reduced relative to control values. SD alone increased SWS time and SWS bout length for 2 h after the end of the SD period. Rabbits subjected to SD for 4 h prior to EC inoculation demonstrated increases in SWS time, DWA during SWS and SWS bout length 2-4 h postinoculation. At some time points, these effects were greater in magnitude than those induced by either manipulation alone, but they were generally equivalent to the additive effects of the individual treatments. Rabbits subjected to SD after EC inoculation (i.e. during the period in which EC increases sleep) demonstrated increases in SWS time and DWA during SWS for only 2 h after the end of the SD period, suggesting that these animals maintained a sleep deficit as compared to rabbits inoculated with EC alone. SD alone elicited hyperthermia in rabbits, and EC-inoculated rabbits subjected to SD developed fevers greater than those induced by either treatment alone. Other clinical indices were not significantly affected by the combined treatments. These data indicate that the sleep changes that occur subsequent to bacterial inoculation are altered in sleep-deprived rabbits, but that SD does not exacerbate clinical illness in this model.

Sleep, sleep deprivation and infectious disease: studies in animals

Common perceptions that the desire for sleep is increased during mild infectious diseases like colds and 'the flu' have fostered beliefs that sleep promotes recovery from infectious disease and that lack of sleep increases susceptibility to infections. However, until recently, the relationship between infectious disease and vigilance received relatively little systematic study. At present, several model systems provide evidence that infectious disease is accompanied by alterations in sleep. Indeed, increased sleepiness, like fever and anorexia, may be viewed as a facet of the acute phase response to infectious challenge. Recent studies also suggest that sleep, sleep deprivation and infectious disease may be related via mechanisms of the immune system (Fig. 1). Data are now accumulating to address questions such as whether immune processes alter sleep, whether sleep or sleep deprivation influences immune competence, and whether sleep facilitates recovery from infectious disease.

Comparison of acute phase responses induced in rabbits by lipopolysaccharide and double-stranded RNA

Infection of injury results in several systemic and central reactions termed the acute phase response (APR). Substantial evidence suggests that cytokines induced by microbes initiate the APR. We compared the APR induced in rabbits by a model bacterial stimulus, lipopolysaccharide (LPS), to that induced by a model viral stimulus, polyriboinosinic:polyribocytidylic acid (poly I:C). The cytokine mRNA responses in a mouse macrophage cell line (RAW 264.7) to LPS or poly I:C were also determined. Rabbits were injected intravenously or intracerebroventricularly with different doses of LPS or poly I:C. Colonic temperatures (Tco) and blood samples were taken at the time of injection and at 3, 6, and 24 h after injection. Leukocyte numbers, serum antiviral activity, serum ceruloplasmin, and plasma fibrinogen were analyzed. Both intravenously injected LPS and poly I:C increased Tco, decreased leukocytes, and increased ceruloplasmin. Only LPS by the intravenous route increased fibrinogen, whereas only intravenously injected poly I:C induced antiviral activity. Intracerebroventricular injections of LPS and poly I:C also elicited dose-dependent febrile responses but did not change the hematologic APR significantly except for fibrinogen. The primary distinctions between LPS and poly I:C with respect to cytokine induction in the RAW 264.7 macrophage cell line were that LPS failed to induce interferon (IFN)-alpha, poly I:C induced interleukin (IL)-6 mRNA minimally and for a shorter time period than did LPS, and LPS induced IL-1 alpha and IFN-beta more rapidly than did poly I:C.(ABSTRACT TRUNCATED AT 250 WORDS)

Somnogenic effects of rabbit and recombinant human interferons in rabbits

Interferons (IFNs) are antiviral cytokines that possess several central nervous system activities. IFN therapy is associated with sleepiness, and the IFNs expressed during viral infection may be involved in the excess sleep associated with these infections. Most viruses stimulate the production of both IFN-alpha and IFN-beta. Although large doses of human IFN-alpha 2 are somnogenic in rabbits, the effects of species-specific IFNs on sleep in the rabbit have not been documented. We compared the somnogenic and antiviral effects of IFNs derived from rabbits to the effects of recombinant human (rh) IFN-alpha and IFN-beta. When injected intracerebroventricularly, rhIFN-alpha A/D, rabbit IFN-alpha/beta, and rabbit reference IFN induced non-rapid-eye-movement sleep and fever in a dose-dependent manner. However, the doses of rabbit IFNs required to induce sleep were much lower than those of human IFNs. Heat treatment of both rabbit IFNs and human IFNs greatly reduced their in vitro antiviral effects. The in vivo activities of rabbit IFNs and rhIFN-alpha A/D were significantly attenuated after heat treatment. However, rhIFN-beta retained its sleep-promoting action after heat treatment, suggesting that microbial contaminants were responsible for its somnogenic and pyrogenic activities. We conclude that IFN-alpha is somnogenic.

Sleep, microbes and cytokines

Dynamic changes in sleep in response to infectious challenge are a facet of the acute phase response. Changes in sleep induced by infection seem to be of recuperative value to the host. Furthermore, loss of sleep is associated with changes in immune function. Specific components of microbes such as muramyl peptides or endotoxin from bacteria or double-stranded RNA from virus induce sleep responses. These microbial-induced responses are mediated via enhanced cytokine and hormone production. Interleukin-1, tumor necrosis factor and interferon-alpha are somnogenic. Interleukin-1-enhanced sleep involves growth hormone-releasing hormone. Microbial-cytokine-altered sleep results from an amplification of physiological sleep mechanisms.

Sleep during experimental trypanosomiasis in rabbits

Trypanosoma brucei subspecies cause the human condition known as "sleeping sickness." In rabbits, these organisms induce a chronic and ultimately fatal disease characterized by periodic parasitemia. To characterize sleep alterations during a chronic infectious condition and to determine how immune stimulation of the host, as reflected by cyclic parasitemia, is related to altered somnolence, we monitored sleep and other clinical indices in rabbits inoculated subcutaneously with Trypanosoma brucei brucei. Within four days, infected rabbits developed fever, reduced food intake, and other signs of infectious illness concurrent with the onset of parasitemia were evident. The initial febrile episodes were transient, recurring in temporal correlation with parasitemia. Time spent in slow-wave sleep and delta-wave amplitude during slow-wave sleep increased significantly in association with the onset of febrile episodes, despite an overall trend toward decreases in these parameters. Because each episode of parasitemia presents an immune stimulus to the infected host, the periodic enhancement of sleep observed in this model is consistent with the hypothesis that immune stimulation is correlated with increased somnolence. The data further indicate that sleep alterations occur not only during acute infections, as previously reported, but during chronic infections as well.

Sleep as a prognostic indicator during infectious disease in rabbits

Infectious disease alters sleep patterns in rabbits, but the recuperative value of enhanced sleep during infectious disease has not been experimentally verified. To evaluate the relationship between specific sleep patterns and the clinical response to infectious disease, we classified sleep patterns in rabbits inoculated with E. coli, S. aureus, or C. albicans on the basis of the duration of the period of enhanced sleep. Patterns characterized by a long period of enhanced sleep were associated with a more favorable prognosis and less severe clinical signs than were patterns characterized by relatively short periods of enhanced sleep followed by prolonged sleep suppression. A contrasting analysis of these data indicated that animals that eventually died demonstrated reduced sleep compared to rabbits that survived the infection. These observations are consistent with the hypothesis that dynamic changes in sleep over the course of an infectious disease aid in recuperation.

Modulation of sleep by cortisone in normal and bacterially infected rabbits

Infectious disease is known to alter both sleep patterns and hydrocortisone (cortisol) concentrations in rabbits. Moreover, the sleep-altering effects of microbial infections are likely to be mediated via endogenous immune modulators whose actions are attenuated by glucocorticoids. To evaluate the relationships between sleep and glucocorticoids during infectious disease, the effects of cortisone administration (20 mg/kg, im) on sleep were examined before and after inoculation of rabbits with Staphylococcus aureus or Escherichia coli. When administered alone, cortisone did not alter the amount of time spent in slow-wave sleep (SWS) but did reduce electroencephalographic (EEG) slow-wave amplitudes during SWS, the number of bouts of SWS and the amount of time spent in rapid-eye-movement sleep. The duration of individual bouts of SWS was increased after cortisone treatment. Bacterially infected rabbits developed biphasic changes in sleep patterns that were characterized by an initial increase and a subsequent decrease both in SWS time and in EEG slow-wave amplitudes during sleep. Cortisone treatment attenuated these effects in S. aureus-inoculated rabbits. In contrast, cortisone treatment did not alter the initial phase of enhanced sleep in E. coli-inoculated rabbits but did attenuate the subsequent sleep suppression. These data indicate that glucocorticoid administration is associated with an attenuated sleep response in bacterially inoculated rabbits.

The role of double-stranded RNA in induction of the acute-phase response in an abortive influenza virus infection model

The inducer of the acute-phase response in "flu-like" viral infections is not defined. The hypothesis that virus-associated double-stranded (ds) RNA serves this function was investigated by comparison of several acute-phase responses (fever and sleep patterns, white and nucleated red blood cell levels, serum antiviral activity and ceruloplasmin) induced by the synthetic dsRNA polyriboinosinic:polyribocytidylic acid (poly[rI:rC]) with those induced by influenza virus in rabbits. The capacity of either dsRNA or influenza virus to induce hyporesponsiveness with respect to these acute-phase parameters upon rechallenge with the same agent or cross-challenge 24 h later was also examined. Poly(rI:rC) induced only minimal hyporesponsiveness to itself but was a potent inducer of hyporesponsiveness to virus with respect to fever, sleep, leukograms, and antiviral activity. Therefore, poly(rI:rC) can substitute for virus in terms of induction of acute-phase hyporesponsiveness, suggesting that dsRNA of viral origin triggers the acute-phase response in this model of influenza.

Influenza virus-induced changes in rabbit sleep and acute phase responses

Systematic investigations of sleep after viral inoculation have not previously been described. In the present study, rabbits were inoculated intravenously (iv) with control allantoic fluid followed by two sequential inoculations of influenza virus at intervals of 24 h. After each i.v. inoculation, sleep and brain temperature (Tbr), as well as leukocyte distributions and serum levels of antiviral activity and ceruloplasmin, were monitored. The first viral inoculation elicited several acute phase responses, including increased non-rapid-eye-movement sleep (NREMS), Tbr, serum antiviral activity, and serum ceruloplasmin levels, as well as neutrophilia and lymphopenia. In contrast to the effects of the first inoculation, after the second inoculation of virus, all these acute phase parameters were diminished or absent (the hyporesponsive state). Inoculation of naive rabbits with heat-inactivated virus was similarly ineffective; however, inoculation of this group of rabbits with viable virus 24 h later did induce full-scale acute phase responses. The possible role of cytokines in mediating the acute phase response after influenza viral challenge is discussed. Results support the hypothesis that sleep is a facet of the acute phase response involved in host defense mechanisms.

Serum amylase activity and calcium and magnesium concentrations in young cattle grazing fescue and Bermuda grass pastures

The study reported here was part of a long-term investigation of the effects of genotype on growth, reproduction, and metabolism in cattle grazing common Bermuda grass and endophyte-infected fescue pastures. In June 1990, blood samples were collected from the tail vein of yearling heifers and steers (Angus [AA], Brahman [BB], and their reciprocal crosses [AB, BA], n = 97). Serum amylase activity was assayed enzymatically; serum Ca and Mg concentrations were determined by atomic absorption spectrophotometry. The effects of endophyte-infected fescue depended on genotype (P less than 0.001). In yearlings having at least 1 Angus parent (AA, AB, BA), grazing endophyte-infected fescue was associated with higher serum amylase activity than was grazing Bermuda grass. But serum amylase activities of BB yearlings consuming either forage were similar. Moreover, for either forage, substantial differences were related to genotype (P less than 0.007) and gender (P less than 0.05). Angus yearlings had higher serum amylase activity than did Brahman yearlings; AB and BA yearlings had intermediate values. Heifers had higher amylase activity than did steers. The relationship among serum values of amylase, Ca, and Mg depended on forage. Yearlings consuming endophyte-infected fescue and having at least 1 Angus parent had a moderate negative correlation between serum amylase activity and Ca concentration (r = -0.53; P less than 0.0005); that is, in calves of genotypes with increased amylase activity while consuming endophyte-infected fescue (AA, AB, BA), the higher the amylase activity, the lower the serum Ca concentration. However, in yearlings consuming Bermuda grass, serum amylase and Ca values were not correlated.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathophysiologic correlates of experimental trypanosomiasis in rabbits

Rabbits inoculated subcutaneously with Trypanosoma brucei brucei developed parasitemia, fever, and reduced food and water intake within 4 to 6 days postinoculation. Subsequent alterations in clinicopathologic parameters included anemia and increased circulating nucleated red blood cells, fibrinogenemia, hypertriglyceridemia, and hyperproteinemia. Transient alterations in the numbers of neutrophils and lymphocytes were detected sporadically; however, leukocytosis was not a characteristic of this chronic infectious condition in rabbits.

Lymphocytic leukemia and lymphosarcoma in a rabbit

Lymphocytic leukemia and lymphosarcoma were diagnosed in a rabbit with lethargy, emaciation, and pallor. The diagnosis was made on the bases of results of hematologic analysis, cytologic evaluation of a bone marrow specimen, and histologic examination. The lymphosarcoma was identified to be of T-cell origin. Leukemia is rarely diagnosed in rabbits, although lymphosarcoma is fairly common in this species.

Physiological stabilization of rabbits after shipping

Significant physiological variations that could influence experimental outcomes have been described in laboratory animals following shipping. The objective of the present study was to monitor a variety of physiologic parameters in rabbits after shipping, and to evaluate the time necessary for stabilization of these variables in the new environment. Data indicate that rabbits develop anorexia, hyperglycemia, neutrophilia, lymphopenia and elevated plasma cortisol concentrations immediately after shipping. Most of these effects abate within 2 days after arrival, suggesting that a minimum stabilization period of 48 hours after shipping is advisable prior to use of rabbits in experimental paradigms.

Somnogenic, pyrogenic, and hematologic effects of experimental pasteurellosis in rabbits

Previous work has demonstrated that intravenous inoculation of rabbits with various microorganisms induces complex time-dependent alterations in sleep as well as other pathophysiological effects typically associated with infectious disease. To evaluate the effects of bacterial challenge that more closely resembles naturally developing disease, we inoculated rabbits with Pasteurella multocida, a common pathogen of this species, using routes of administration that mimic normal routes of exposure. Biphasic sleep alterations characterized initially by enhanced slow-wave sleep and later by decreased slow-wave sleep occurred after intravenous, intramuscular, subcutaneous, or intranasal inoculation. Rapid-eye-movement sleep was inhibited for most of the 48-h period after inoculation. Inoculation by all four routes also induced fever and qualitatively similar hematologic changes. However, the magnitude and specific temporal patterns of both somnogenic changes and other pathophysiological effects varied with the route of inoculation.

Somnogenic, pyrogenic, and hematologic effects of bacterial peptidoglycan

Bacterial infections and certain muramyl peptides elicit a variety of pathophysiological effects including increases in body temperature and slow-wave sleep. Bacterial cell wall peptidoglycan is composed of muramyl peptides. To investigate the ability of isolated bacterial cell walls to enhance slow-wave sleep, rabbits were injected intravenously with cell walls isolated from Staphylococcus aureus or with soluble peptidoglycan prepared from Neisseria gonorrhoeae. These injections increased slow-wave sleep, electroencephalographic delta-wave amplitudes, and body temperature, reduced rapid-eye-movement sleep, and induced neutrophilia and lymphopenia. The somnogenic and pyrogenic effects of S. aureus cell walls developed within 1 h and persisted throughout the recording period. Injections of N. gonorrhoeae peptidoglycan induced similar effects but of larger magnitude and shorter duration. We conclude that peptidoglycan is a bacterial component that mediates the increased sleep observed during infectious disease.