Influence of Chronic Exposure to Simulated Shift Work on Disease and Longevity in Disease-Prone Inbred Mice.

Shift work (SW) is viewed as a risk factor for the development of many serious health conditions, yet prospective studies that document such risks are rare. The current study addressed this void by testing the hypothesis that long-term exposure to repeated diurnal phase shifts, mimicking SW, will accelerate disease onset or death in inbred mice with genetic risk of developing cancer, diabetes, or autoimmune disease. The data indicate that 1) life-long exposure to simulated SW accelerates death in female cancerprone AKR/J mice; 2) a significant proportion of male NON/ShiLtJ mice, which have impaired glucose tolerance but do not normally progress to type 2 diabetes, develop hyperglycemia, consistent with diabetes (that is, blood glucose 250 mg/dL or greater) after exposure to simulated SW for 8 wk; and 3) MRL/MpJ mice, which are prone to develop autoimmune disease, showed sex-related acceleration of disease development when exposed to SW as compared with mice maintained on a stable photocycle. Thus, longterm exposure to diurnal phase shifts that mimic SW reduces health or longevity in a wide variety of disease models. Our approach provides a simple way to assess the effect of chronic diurnal disruption in disease development in at-risk genotypes.

Cytokine and chemokine responses of lung exposed to surrogate viral and bacterial infections.

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 lung's 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.

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.

Metabolic effects of intra-abdominal fat in GHRKO mice.

Mice with targeted deletion of the growth hormone receptor (GHRKO mice) are growth hormone (GH) resistant, small, obese, hypoinsulinemic, highly insulin sensitive and remarkably long-lived. To elucidate the unexpected coexistence of adiposity with improved insulin sensitivity and extended longevity, we examined effects of surgical removal of visceral (epididymal and perinephric) fat on metabolic traits related to insulin signaling and longevity. Comparison of results obtained in GHRKO mice and in normal animals from the same strain revealed disparate effects of visceral fat removal (VFR) on insulin and glucose tolerance, adiponectin levels, accumulation of ectopic fat, phosphorylation of insulin signaling intermediates, body temperature, and respiratory quotient (RQ). Overall, VFR produced the expected improvements in insulin sensitivity and reduced body temperature and RQ in normal mice and had opposite effects in GHRKO mice. Some of the examined parameters were altered by VFR in opposite directions in GHRKO and normal mice, and others were affected in only one genotype or exhibited significant genotype × treatment interactions. Functional differences between visceral fat of GHRKO and normal mice were confirmed by measurements of adipokine secretion, lipolysis, and expression of genes related to fat metabolism. We conclude that in the absence of GH signaling, the secretory activity of visceral fat is profoundly altered and unexpectedly promotes enhanced insulin sensitivity. The apparent beneficial effects of visceral fat in GHRKO mice may also explain why reducing adiposity by calorie restriction fails to improve insulin signaling or further extend longevity in these animals.

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.

Hematology and clinical chemistry values in pregnant Wistar Hannover rats compared with nonmated controls.

BACKGROUND: The Wistar Hannover rat has been considered as an alternative animal model to the Sprague-Dawley rat in the safety evaluation of candidate pharmaceuticals for potential reproductive and developmental toxicity. Hematology and clinical chemistry results may provide useful evidence of maternal toxicity in the absence of fetal effects. OBJECTIVE: The purpose of this study was to evaluate differences in routine laboratory values between nonmated and pregnant (near-term)Wistar Hannover rats during a control developmental study. METHODS: One hundred fifty pregnant female Wistar Hannover rats (Tac:Glx:WlfBR) were dosed orally once per day with distilled water from gestation days (GDs) 6 through 17. An additional 150 nonmated (nonpregnant) females used as age-matched controls were dosed from study days (SDs) 7 through 18. Blood samples were collected on GD 18 or 19 (SD 19 or 20) for routine hematology and plasma clinical chemistry tests. Reference intervals were established for pregnant and nonmated animals. RESULTS: On GD 18/19, pregnant rats had a lower RBC count, hemoglobin concentration, and HCT, and higher MCH, MCHC, reticulocyte percentage, and platelet, WBC, absolute reticulocyte, segmented neutrophil, lymphocyte, and monocyte counts compared with nonmated rats. Pregnant rats had lower albumin, glucose, urea, and chloride concentrations, lower creatine kinase and alkaline phosphatase activities, higher total bilirubin, cholesterol, triglyceride, calcium, phosphorus, and globulin concentrations, and higher ALT activity than nonmated rats. Serum triglyceride concentration was approximately fourfold higher in pregnant rats compared with nonmated controls. CONCLUSION: Differences in hematology and chemistry values in pregnant Wistar Hannover rats are similar to those in Sprague-Dawley rats and support use of the Wistar Hannover rat as an animal model in the assessment of maternal toxicity. Differences in laboratory values of pregnant rats should be considered when interpreting data following exposure to candidate pharmaceuticals.

24-hour intravenous infusion via the marginal ear vein in the New Zealand white rabbit.

A method was needed to conduct a 24-h intravenous infusion procedure in rabbits that minimized animal restraint and allowed unlimited access to the animal by research staff. We catheterized 16 male and 16 female New Zealand White rabbits (Oryctolagus cuniculus) by inserting an indwelling human infant catheter into the marginal ear vein. The catheter was connected, via an extension set, to a small, lightweight, ambulatory pump with predetermined pump rates; the pump was placed in a Lycra jacket that the rabbit was wearing. Toxicokinetic samples, electrocardiograms, and clinical pathology samples were collected at multiple time points. Pump accuracy was verified by collecting the pre- and post-dose weights of the pumps as well as infusion start and stop times. Depending on the infusion rate, pumps were changed every 5 or 10 h or at the end of 24 h. The accuracy of these pumps was between 5% and 10% of the calculated target volume from 0 to 20 h. The lack of need for surgery or long-term restraint and tethering is a refinement in infusion technology and animal use.

An oral (gavage) control embryo-fetal development study in the Wistar Hannover rat.

Many of the studies conducted to examine the developmental and reproductive toxicity potential of candidate pharmaceuticals use the Sprague-Dawley rat as the animal model. This is due in part to the large database for this outbred rat available for comparison of litter data, and the low incidence of fetal malformations and variations. The following study was conducted to generate information on potential embryo-fetal developmental defects and litter data in another outbred stock of rat, the Wistar Hannover. One hundred fifty pregnant female Wistar Hannover rats (Tac:Glx:WIfBR) were dosed orally once per day with distilled water from Gestation Days (GD) 6 through 17 covering the time from implantation to closure of the hard palate (GD0 = day of insemination). Caesarean sections were performed on Day 20 of gestation. All fetuses were examined for external, visceral and skeletal malformations and variations. Macroscopic and histomorphologic examinations were also completed for the F0 females at termination. The percent pregnant (88%) and litter size (average 10.6) were found to be lower than that commonly reported for the Sprague-Dawley rat (Crl:CD (SD)BR; 95.4% and 14.6, respectively). Pre-implantation loss (14.1%), post-implantation loss (7.4%) and percent resorptions (7.2%) occurred at a higher incidence than typically seen in the Sprague-Dawley rat (5.9, 5.6 and 5.1%, respectively). The average fetal body weights for both the female and male rats were lower than those typically seen in the Sprague-Dawley rat. External, visceral and skeletal examination of the F1 fetuses revealed numerous malformations and variations which also occurred at higher incidences than those reported for the Sprague-Dawley rat. Routine macroscopic and histomorphologic examination showed there were no changes that would be interpreted to have impaired mating performance, fertility or gestation. Thus, this study provides information on the reproductive effects and the background incidence of embryo-fetal development defects that could be used for comparison to those identified when using this outbred rat for developmental and reproductive toxicity studies, as well as for comparison to the more commonly used rat stock, the Sprague-Dawley rat. For the parameters evaluated, the Wistar Hannover rat had greater variability and an increased incidence of spontaneous malformations as compared to the Crl:CD (SD)BR Sprague-Dawley rat. These findings should be considered if this stock of rat is selected in the conduct of developmental and reproductive toxicity studies.