Enterotoxigenic Escherichia coli (ETEC) infections are a significant cause of diarrheal disease and infant mortality in developing countries. Studies of ETEC pathogenesis relevant to vaccine development have been greatly hampered by the lack of a suitable small-animal model of infection with human ETEC strains. Here, we demonstrate that adult immunocompetent outbred mice can be effectively colonized with the prototypical human ETEC H10407 strain (colonization factor antigen I; heat-labile and heat-stable enterotoxin positive) and that production of heat-labile holotoxin provides a significant advantage in colonization of the small intestine in this model.Enterotoxigenic Escherichia coli (ETEC) infections are a significant cause of diarrheal disease worldwide. Infections caused by this heterogeneous group of pathogens remain major causes of diarrheal morbidity and infant mortality in developing countries (11,33,61), are perennially associated with disease in travelers (4, 7, 43) and in soldiers deployed to developing countries (8, 32), and have recently been associated with large outbreaks in developed countries, including the United States (1, 13).In the presently accepted paradigm for ETEC pathogenesis, fimbrial (or fibrillar) colonization factors (CFs) (10,22,27) mediate colonization of the small intestine, where organisms elaborate heat-labile enterotoxin (LT) and/or heat-stable enterotoxin (ST) (21, 68). Vaccine development has largely focused on the CFs; however, development of a broadly protective ETEC vaccine has been hampered due to the considerable heterogeneity of the known CFs (6,52,58,62).While a number of other surface antigens of ETEC have been described (20,25,51), their utility as potential vaccine candidates has not been effectively explored, largely due to the lack of a suitable animal model for testing. Animal models that have been used in previous studies of ETEC include infant (3, 16-18, 28, 47) and adult (9) mice, rats (34, 35), and rabbits (19,46,51). All of these models have inherent difficulties in utilization or require anesthesia and/or significant surgical manipulation. Some of the models have not been thoroughly evaluated.We sought to develop a murine model of small-intestinal colonization with human ETEC isolates using adult immunocompetent mice. Here, we report our initial use of this model using the prototypical human ETEC H10407 strain. Furthermore, similar to recent studies of porcine ETEC infection of gnotobiotic piglets (2), we demonstrate that elaboration of the heat-labile toxin provides a distinct advantage to the organism in establishing early colonization of the small-intestinal mucosa.

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Maternal cocaine abuse may increase the incidence of perinatal asphyxia. In nonexposed asphyxiated neonates, decreased cerebrospinal fluid (CSF) cAMP concentrations are associated with poor neurological outcome. On the other hand, cocaine increases central nervous system (CNS) cAMP. Therefore, we hypothesized that in utero cocaine exposure may increase brain cAMP and thereby preserve cerebrovascular responses to cAMP-dependent stimuli following asphyxia. Pregnant pigs received either cocaine (1 mg/kg, i.v.) twice weekly during the last trimester or normal saline vehicle (sham-control) and were allowed to deliver vaginally at term. Cranial windows were implanted in the newborn pigs within the first week of life and used to collect CSF for cAMP determinations and to assess changes in pial arteriolar diameters (PAD). In the first part of the study, pial arteriolar responses to different vasodilator and vasoconstrictor stimuli were evaluated in piglets prior to asphyxia (n = 20). In newborn pigs exposed to cocaine, cerebrovascular responses to hypercapnia and norepinephrine were significantly exaggerated compared to controls. Then, piglets were randomly selected for the second part of the study that involved prolonged asphyxia (n = 12). In cocaine-exposed but not sham-control piglets, CSF cAMP increased markedly during asphyxia. In the sham piglets, but not the cocaine-exposed piglets, CSF cAMP fell progressively below the baseline during recovery. Cerebrovascular reactivity to cAMP-dependent stimuli (hypercapnia and isoproterenol) was preserved during recovery from asphyxia in the cocaine-exposed piglets but significantly attenuated in the sham controls. We conclude that piglets with chronic prenatal exposure to cocaine show exaggerated cerebrovascular responses to vasogenic stimuli and preserved cAMP-dependent cerebral vasoreactivity following asphyxia.

Drug developers worldwide assess compound safety and efficacy using measures that include mouse core temperature andlocomotor activity. Subtle differences in animal housing conditions between institutions can alter these values, impacting scientific rigor and reproducibility. In these studies, adult male NIH Swiss mice were surgically implanted with radiotelemetry probes that simultaneously monitored core temperature and locomotor activity across various housing conditions. In the first study, ambient temperature was varied between 20 °C and 28 °C in groups of singly housed mice. Additional studies held the mice at a constant ambient temperature and examined the effects of cage density (housing animals singly or in groups of 3 or 6), bedding change and provision of nesting material, and the availability of a running wheel on core temperature and locomotor activity. Mice overwhelmingly maintained species-typical core temperatures across all ambient temperatures,across all housing conditions, when bedding was fresh or old, and with or without the provision of cotton squares as nesting material. However, engaging in wheel running and the combination of fresh bedding and cotton squares transiently increased core temperatures beyond the species-typical range. Similarly, the circadian distribution of locomotor activity was significantly disrupted by placing animals in cages with fresh bedding or nesting material, or by performing both of these manipulations concurrently during the light period. These findings suggest that standard husbandry practices and common housing conditions may transiently affect core temperature in adult mice. Furthermore, these practices may have profound and relatively long-lasting effects on motor activity and the regulation of circadian rhythms.