Linda A. Toth

The nature and identification of quantitative trait loci: a community’s view

This white paper by eighty members of the Complex Trait Consortium presents a communitys view on the approaches and statistical analyses that are needed for the identification of genetic loci that determine quantitative traits. Quantitative trait loci (QTLs) can be identified in several ways, but is there a definitive test of whether a candidate locus actually corresponds to a specific QTL?

Sleep as a prognostic indicator during infectious disease in rabbits

Abstract 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.

Cytokine involvement in the regulation of sleep

Conclusions Sleep can clearly be modulated by exogenous administration of cytokines, and is also likely to be regulated, in part, by endogenous cytokines. The synthesis of small peptide fragments from cytokines and the development of specific receptor antagonists and antibodies provide promising new tools with which to further examine the mechanisms reponsibile for cytokine-induced changes in vigilance. Although the mechanisms and sites of action mediating these somnogenic properties are not yet fully elucidated, the somnogenic responses to microbial challenge may represent amplifications of normal, physiological processes.

Genetic susceptibility and resistance to influenza infection and disease in humans and mice

Although genetic risk factors for influenza infection have not yet been defined in people, differences in genetic background and related variation in the response to infection, as well as viral virulence, are all likely to influence both the likelihood of infection and disease severity. However, apart from characterization of viral binding sites in avian and mammalian hosts, relatively little investigation has focused on host genetic determinants of susceptibility or resistance to infection, or the severity of the associated disease in humans or other species. Similarly, the role of genetic background in the generation of an efficacious immune response to either infection or vaccination has not been extensively evaluated. However, genetic influences on susceptibility and resistance to numerous infectious agents and on the resultant host inflammatory and immune responses are well established in both humans and other animals. Mouse-adapted strains of human influenza viruses and the use of inbred strains of laboratory mice have supported extensive characterization of the pathogenesis and immunology of influenza virus infections. Like individual humans, inbred strains of mice vary in their reactions to influenza infection, particularly with regard to the inflammatory response and disease severity, supporting the potential use of these mice as a valuable surrogate for human genetic variation. Relying heavily on what we have learned from mice, this overview summarizes existing animal, human and epidemiologic data suggestive of host genetic influences on influenza infection.

Sleep during experimental trypanosomiasis in rabbits.

Abstract Trypanosoma brucel 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 brucel brucel. 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 [P.S.E.B.M. 1994, Vol 205]

In vitro lung slices: a powerful approach for assessment of lung pathophysiology

This review summarizes the existing literature on the use of in vitro lung slices to study pulmonary physiology, pharmacology, pathogenesis and toxicity. Since in vitro lung slices maintain cell–cell and cell–matrix relationships in a highly controllable and accessible setting, they offer many advantages over both in vivo and single-cell culture systems. With the advent of high-production slicers, lung slices can be rapidly and reproducibly generated, including from animals treated in vivo. Slices can then be treated in vitro and analyzed using high-throughput technology. Therefore, the lung-slice system offers broad, current and unrealized potential for the detection of toxicity and the delineation of pathophysiologic and therapeutic mechanisms.

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.

Macrophage participation in influenza-induced sleep enhancement in C57BL/6J mice

Mice develop changes in sleep during the nonspecific immune response that occurs during the initial few days after inoculation with influenza virus. T lymphocytes, neutrophils, macrophages, and natural killer (NK) cells all participate in the early host response to influenza infection. All of these cell types are potential sources of endogenous substances that modulate sleep, but the contributory role of each cell type to the alteration of somnolence during infection has not been determined. To investigate which cell types contribute to the sleep enhancement that develops during influenza infection in mice, the sleep patterns of C57BL/6J mice with perturbations of particular facets of host immune response capabilities were assessed before and after influenza infection. Targeted mutation of the gene Ccl3 (macrophage inflammatory protein 1 alpha) prevented development of the dark phase sleep enhancement that is characteristic of C57BL/6J mice after influenza infection. Other experimental treatments that impair macrophage or monocyte function also produced significant (administration of pentoxifylline or CNI-1493) or marginally significant (deletion of the interferon-gamma gene or intranasal administration of carrageenan) changes in influenza-induced sleep enhancement in C57BL/6J mice. In contrast, functional impairments of NK cells, neutrophils, and T lymphocytes did not significantly influence sleep responses. These data therefore support a contributory role for macrophages, but not for NK cells, neutrophils, and T lymphocytes, in eliciting the sleep response typical of influenza-infected C57BL/6J mice.

Host genetic background and the innate inflammatory response of lung to influenza virus

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.

The influence of the cage environment on rodent physiology and behavior: Implications for reproducibility of pre-clinical rodent research.

The reproducibility of pre-clinical research is an important concern that is now being voiced by constituencies that include the National Institutes of Health, the pharmaceutical industry, Congress, the public and the scientific community. An important facet of performing and publishing well-controlled reproducible pre-clinical research is to stabilize and more completely define the environment of the animal subjects. Scientists who use rodents in research generally recognize the importance of maintaining a stable animal environment. However, despite a theoretical and general awareness of these issues, many may lack a true appreciation of how significantly even seemingly minor variations in the environment can affect research outcomes. The purpose of this article is to help investigators gain a more comprehensive and substantiated understanding of the potentially significant impact of even seemingly minor environmental changes on the animals and the data. An important caveat to this article is that the examples presented were selected from a very large literature, admittedly in order to illustrate certain points. The goal of this article is not to provide an overview of the entire literature on how the environment affects rodents but rather to make preclinical scientists more aware of how these factors can potentially influence the experimental data and contribute to poor reproducibility of research.