Mouse Models of Escherichia coli O157:H7 Infection and Shiga Toxin Injection

Escherichia coli O157:H7 has been responsible for multiple food- and waterborne outbreaks of diarrhea and/or hemorrhagic colitis (HC) worldwide. More importantly, a portion of E. coli O157:H7-infected individuals, particularly young children, develop a life-threatening sequela of infection called hemolytic uremic syndrome (HUS). Shiga toxin (Stx), a potent cytotoxin, is the major virulence factor linked to the presentation of both HC and HUS. Currently, treatment of E. coli O157:H7 and other Stx-producing E. coli (STEC) infections is limited to supportive care. To facilitate development of therapeutic strategies and vaccines for humans against these agents, animal models that mimic one or more aspect of STEC infection and disease are needed. In this paper, we focus on the characteristics of various mouse models that have been developed and that can be used to monitor STEC colonization, disease, pathology, or combinations of these features as well as the impact of Stx alone

The Influence of Prediction Error Strength on Reconsolidation

It has been well established that consolidated memories can be reactivated and enter a labile state where they are once again vulnerable to modification. Reactivated memories, therefore, need to be restabilized or reconsolidated. Prediction error (PE) is one of the most common ways of reactivating consolidated memories, yet no studies have examined how varying the strength of PE influences reconsolidation. The present study aimed to determine if the strength of PE is an important factor for triggering reconsolidation and if so, how PE strength influences the reconsolidation process, whether through strengthening or weakening the memory. To vary PE strength, participants were presented with triplets of images on Day 1. The first two images created a predictable context for the following target image. The context and target images repeated together either 4 times (high PE), 1 time (low PE), or not at all (no PE), to vary the strength of prediction. On Day 2, PE was introduced by replacing the expected Day 1 targets with novel targets for the reactivation group. A control group was presented with a new sequence of images and experienced no PE. Finally, on Day 3 all participants were tested on their memory of Day 1 and Day 2 targets using a recognition memory test. We predicted that high PE would result in better memory for both Day 1 and Day 2 targets. We also predicted that the reactivation group would remember more Day 1 and Day 2 targets compared to the control group. We did not find the predicted pattern of results. Participants in the reactivation group showed significantly worse memory for items in the high PE and low PE conditions compared to the NoPE conditions. We also did not find evidence of reconsolidation. There was no difference in memory performance between the reactivation group (experienced PE) and the control group (did not experience PE). Keywords: reconsolidation, prediction error, memor

The Influence of Prediction Error Strength on Recognition Memory

An important feature of learning and memory is being able to make predictions about our environments based on past experiences. However, our predictions are not always accurate. We may experience a prediction error (a mismatch between what was predicted and what actually occurred). Research has found that PE enhances learning and memory. The Predictive Interactive Multiple Memory Signals (PIMMS) suggests that PE facilitates learning and memory because it triggers a need to update our representation to reduce errors in the future. This study aims to replicate Greve et al., (2017), who found that PE enhances declarative memory of learned associations. A successful replication would result in better memory for items associated with PE compared to items consistent with expectations.https://digitalscholarship.unlv.edu/durep_posters/1147/thumbnail.jp

Recognition Memory for Auditory and Visual Objects

Visual object memory is superior to auditory object memory. Our past research showed that auditory memory was less sensitive to divide attention during study, which may be attributable to representational differences between auditory memory and visual memory. In the present study, we attempted to equate auditory and visual memory representations in order to adequately investigate the impact of dividing attention on recognition memory. Recognition memory is thought to rely on two distinct processes, recollection and familiarity. Recollection involves the retrieval of precise qualitative detail and is the most sensitive to dividing attention.https://digitalscholarship.unlv.edu/durep_posters/1086/thumbnail.jp

Investigating the impact of dividing attention on auditory and visual object memory

Recently, we found that dividing attention reduced recollection and familiarity for visual objects, but a different pattern emerged for auditory object memory: auditory object recollection was not affected by dividing attention. This could be attributable to differing levels of baseline performance with visual memory far exceeding auditory memory. Thus, we attempted to equate baseline performance in both modalities in order to adequately investigate the previous findings.https://digitalscholarship.unlv.edu/durep_posters/1133/thumbnail.jp

Serotonin and corticosterone rhythms in mice exposed to cigarette smoke and in patients with COPD:implication for COPD-associated neuropathogenesis

The circadian timing system controls daily rhythms of physiology and behavior, and disruption of clock function can trigger stressful life events. Daily exposure to cigarette smoke (CS) can lead to alteration in diverse biological and physiological processes. Smoking is associated with mood disorders, including depression and anxiety. Patients with chronic obstructive pulmonary disease (COPD) have abnormal circadian rhythms, reflected by daily changes in respiratory symptoms and lung function. Corticosterone (CORT) is an adrenal steroid that plays a considerable role in stress and anti-inflammatory responses. Serotonin (5-hydroxytryptamine; 5HT) is a neurohormone, which plays a role in sleep/wake regulation and affective disorders. Secretion of stress hormones (CORT and 5HT) is under the control of the circadian clock in the suprachiasmatic nucleus. Since smoking is a contributing factor in the development of COPD, we hypothesize that CS can affect circadian rhythms of CORT and 5HT secretion leading to sleep and mood disorders in smokers and patients with COPD. We measured the daily rhythms of plasma CORT and 5HT in mice following acute (3 d), sub-chronic (10 d) or chronic (6 mo) CS exposure and in plasma from non-smokers, smokers and patients with COPD. Acute and chronic CS exposure affected both the timing (peak phase) and amplitude of the daily rhythm of plasma CORT and 5HT in mice. Acute CS appeared to have subtle time-dependent effects on CORT levels but more pronounced effects on 5HT. As compared with CORT, plasma 5HT was slightly elevated in smokers but was reduced in patients with COPD. Thus, the effects of CS on plasma 5HT were consistent between mice and patients with COPD. Together, these data reveal a significant impact of CS exposure on rhythms of stress hormone secretion and subsequent detrimental effects on cognitive function, depression-like behavior, mood/anxiety and sleep quality in smokers and patients with COPD

The circadian clock, metabolism and obesity

In the last decades, obesity has been on the rise becoming a burden for health care systems. The reasons behind this rise are most likely caused by lifestyle rather than by an increase in gene mutations, because manifestations of genetic alterations would take longer than just a few decades. Lifestyle has a great impact on the circadian system and therefore on the body internal organization of physiological and biochemical processes, regulating various aspects of behavior and metabolism. In the following, I will discuss recent studies delineating relationships between metabolic processes and the circadian system, how metabolites and nutrients regulate the circadian clock and how nuclear receptors can act as metabolic sensors and clock regulators. Finally, I will discuss how clock modulation and feeding patterns influence the development of obesity