Differences in Fluid, Electrolyte, and Energy Balance in C57BL/6J Mice (Mus musculus) in Metabolic Caging at Thermoneutral or Standard Room Temperatures

The Guide for the Care and Use of Laboratory Animals recommends mice be pair or group housed and provided with nesting materials. These provisions support social interactions and are also critical for thermoregulatory behaviors such as huddling and burrowing. However, studies of fluid and electrolyte balance and digestive function may involve use of metabolic caging (MC) systems in which mice are housed individually on wire-mesh floors that permit quantitative collection of urine and feces. MC housing prevents mice from performing their typical huddling and burrowing behaviors. Housing in MC can cause weight loss and behavioral changes in rodents. Here, we tested the hypothesis that MC housing of mice at standard room temperature (SRT, 22 to 23 °C) exposes them to cold stress, which causes metabolic changes in the mice as compared with standard housing. We hypothesized that performing MC studies at a thermoneutral temperature (TNT, 30 °C) would minimize these changes. Fluid, electrolyte, and energy balance and body composition were assessed in male and female C57BL/6J mice housed at SRT or TNT in MC, static microisolation cages, or a multiplexed metabolic phenotyping system designed to mimic static microisolation cages (Promethion, Sable Systems International). In brief, as compared with MC housing at SRT, MC housing at TNT was associated with lower food intake and energy expenditure, absence of weight loss, and lower urine and fecal corticosterone levels. These results indicate that housing in MC at SRT causes cold stress that can be mitigated if MC studies are performed at TNT.

Btg2 mutation induces renal injury and impairs blood pressure control in female rats

Hypertension (HTN) is a complex disease influenced by heritable genetic elements and environmental interactions. Dietary salt is among the most influential modifiable factors contributing to increased blood pressure (BP). It is well established that men and women develop BP impairment in different patterns and a recent emphasis has been placed on identifying mechanisms leading to the differences observed between the sexes in HTN development. The current work reported here builds on an extensive genetic mapping experiment which sought to identify genetic determinants of salt sensitive (SS) HTN using the Dahl SS rat. BTG anti-proliferation factor 2 (Btg2) was previously identified by our group as a candidate gene contributing to SS HTN in female rats. In the current study, Btg2 was mutated using TALEN targeted gene disruption on the SSBN congenic rat background. The Btg2 mutated rats exhibited impaired BP and proteinuria responses to a high salt diet compared to wild type rats. Differences in body weight, mutant pup viability, skeletal morphology, and adult nephron density suggest a potential role for Btg2 in developmental signaling pathways. Subsequent cell cycle gene expression assessment provides several additional signaling pathways that Btg2 may function through during salt handling in the kidney. The expression analysis also identified several potential upstream targets that can be explored to further isolate therapeutic approaches for SS HTN.

Short-term Housing in Metabolic Caging on Measures of Energy and Fluid Balance in Male C57BL/6J Mice ( Mus musculus)

Metabolic caging is an important tool for quantitative urine and feces collection in rodents, although significant limitations and problems accompany its use. Despite strong opinions among investigators regarding the effects of metabolic caging on energy and fluid homeostasis, careful quantitative analysis of the impact of this caging type-particularly when used for mice-is lacking. The current study assessed the effects of metabolic caging, with or without modifications such as plastic platform inserts, on ingestive behaviors, energy expenditure, accuracy of urine and fecal collection, and ambulatory activities in male C57BL/6J mice. Housing mice in metabolic cages, regardless of platform inclusion, increased energy expenditure without modifying food intake, presumably due to the inability of mice to perform normal thermoregulatory behaviors (burrowing and huddling). Surprisingly, mice in metabolic cages actively avoided platforms, and the inclusion of platforms modified the behavior of the mice and had position-dependent effects that reduced the accuracy of urine collection. Moving mice from cohousing to individual housing in home cages also increased ingestive behaviors and energy expenditure. We conclude that single housing of male C57BL/6J mice increases energy expenditure, that this increase is potentiated in metabolic caging conditions, and that platforms in metabolic cages alter mouse behavior and urine collection. Additional future work is needed to determine the potential benefits of using higher ambient temperature for studies of mice in metabolic caging and whether the above effects occur in females and other strains of mice and other rodent species.

PCR testing of a ventilated caging system to detect murine fur mites

Rodents housed in microisolation caging are commonly monitored for infectious agents by the use of soiled bedding sentinels. This strategy relies on the successful transmission of rodent pathogens from the index rodents via soiled bedding to sentinel cages and the subsequent infection or colonization of sentinel rodents. When the prevalence of a pathogen is low or the target agent is not readily transmitted by soiled bedding, alternative testing methodologies should be used. Given the continued prevalence of institutions self-reporting murine fur mites and with the advent of a new sensitive and specific PCR assay for mites, we sought to determine whether the exhaust system of an individual ventilated caging (IVC) system could be used for monitoring the rack's rodent population for mites rather than relying on the responses of sentinels. We deployed single cages of mice (Mus musculus) that were known to be infested with either Radfordia affinis or Myobia musculi on a 70-cage rack, sampled the horizontal exhaust manifolds weekly, and used the new PCR assay to test these samples for mite DNA. We detected the presence of fur mites at a 94.1% probability of detection within 4 wk of placement. Therefore, we recommend swabbing and testing the shelf exhaust manifolds of IVC racks rather than relying on soiled-bedding sentinels as an indicator of the mite status of the rodents on that rack.

A coupled experimental and computational approach to quantify deleterious hemodynamics, vascular alterations, and mechanisms of long-term morbidity in response to aortic coarctation

INTRODUCTION

Coarctation of the aorta (CoA) is associated with morbidity despite treatment. Although mechanisms remain elusive, abnormal hemodynamics and vascular biomechanics are implicated. We present a novel approach that facilitates quantification of coarctation-induced mechanical alterations and their impact on vascular structure and function, without genetic or confounding factors.

METHODS

Rabbits underwent thoracic CoA at 10weeks of age (~9 human years) to induce a 20mmHg blood pressure (BP) gradient using permanent or dissolvable suture thereby replicating untreated and corrected CoA. Computational fluid dynamics (CFD) was performed using imaging and BP data at 32weeks to quantify velocity, strain and wall shear stress (WSS) for comparison to vascular structure and function as revealed by histology and myograph results.

RESULTS

Systolic and mean BP was elevated in CoA compared to corrected and control rabbits leading to vascular thickening, disorganization and endothelial dysfunction proximally and distally. Corrected rabbits had less severe medial thickening, endothelial dysfunction, and stiffening limited to the proximal region despite 12weeks of normal BP (~4 human years) after the suture dissolved. WSS was elevated distally for CoA rabbits, but reduced for corrected rabbits.

DISCUSSION

These findings are consistent with alterations in humans. We are now poised to investigate mechanical contributions to mechanisms of morbidity in CoA using these methods.

Human thrombopoietin reduces myocardial infarct size, apoptosis, and stunning following ischaemia/reperfusion in rats

AIMS

Thrombopoietin (Tpo) is known for its ability to stimulate platelet production. However, it is currently unknown whether Tpo plays a physiological function in the heart.

METHODS AND RESULTS

We assessed the potential protective role of Tpo in vitro and in vivo in two rat models of myocardial ischaemia/reperfusion. Tpo receptor (c-mpl) message was detected in the heart using RT-PCR, and the Tpo receptor protein was detected using western blotting and immunohistochemistry. Tpo treatment immediately before ischaemia reduced myocardial necrosis, apoptosis, and decline in ventricular function following ischaemia/reperfusion in the rat in a concentration- and dose-dependent manner with an optimal concentration of 1.0 ng/mL in vitro and an optimal dose of 0.05 microg/kg iv in vivo. Tpo also reduced infarct size when given after the onset of ischaemia or at reperfusion. Tpo activated JAK-2 (Janus kinase-2) and p44 MAPK (mitogen-activated protein kinase) during reperfusion but not prior to ischaemia. Inhibition of JAK-2 (AG-490), p42/44 MAPK (PD98059), mitochondrial K(ATP) channels (5-HD), and sarcolemmal K(ATP) channels (HMR 1098) abolished Tpo-induced resistance to injury from myocardial ischaemia/reperfusion. AG-490, PD98059, 5-HD, and HMR1098 alone had no effect on cardioprotection. Treatment with a single dose of Tpo (0.05 or 1.0 microg/kg iv) did not result in the elevation of platelet count or haematocrit over a 16-day period.

CONCLUSION

A single treatment of Tpo confers cardioprotection through JAK-2, p42/44 MAPK, and K(ATP) channels, suggesting a potential therapeutic role of Tpo in the treatment of injury resulting from myocardial ischaemia and reperfusion.

Evaluation of the pathology, pathogenesis and aetiology of auricular elephantiasis in slaughter pigs

Ears from slaughter pigs with auricular elephantiasis (n = 24) and the corresponding lymph nodes (lnn.) (n = 26) were grossly, histopathologically and microbiologically examined. Immunostaining for IgM, IgG, Cd3epsilon and bacterial antigens of Arcanobacterium pyogenes and Staphylococcus aureus was performed by indirect enzyme-based techniques. Ears were variably thickened depending on the sampled area (basis, centre and apex). However, at all locations the thickness, the length from basis to apex and the weigh of whole ears with elephantiasis were significantly increased (P < 0.01). The corresponding lnn., that is, ln. parotideus superficialis and profundus, had also increased significantly (P < 0.01) in volume. Histopathologically, lesions of the ears and the corresponding lnn. revealed changes characterized by diffuse fibrosis intermingled with multiple pyogranulomatous foci containing asteroid bodies. In the majority of lesions, four distinct zones due to different cellular infiltrates encircled the central core of the asteroid bodies. In several lesions, the pyogranulomatous foci were contained within the lymph vessels. Immunohistochemically, only the bacterial antigen of S. aureus was detected within the cytoplasm of the macrophages and/or in the asteroid bodies of the ears (41.5%) and in the regional lnn. (30.8%). An abundant number of IgM, IgG and CD3epsilon-positive cells were present in all the pyogranulomatous lesions, whereas a positive IgG-staining was observed only in a single asteroid body. Thus, porcine auricular elephantiasis is a chronic pyogranulomatous inflammation that is frequently positive for S. aureus and is lymphogenically spread. Therefore, the lesions of the ears with auricular elephantiasis and the corresponding lnn. should be termed auricular botryomycosis and botryomycotic lymphadenitis, respectively. Moreover, as the disease is observed frequently in slaughter pigs it must also be considered according to the welfare of the animals and in relation to post-mortem meat inspection.

Pre-hospital parenteral antibiotic treatment of meningococcal disease and case fatality: a Danish population-based cohort study

OBJECTIVES

Studies about the efficiency of pre-hospital antibiotic treatment of meningococcal disease are conflicting. We examined the case fatality rate in patients with meningococcal disease treated with pre-hospital antibiotics.

METHODS

A cohort study of 534 patients hospitalized with meningococcal disease from two Danish counties. Clinical data were obtained from referral letters from general practitioners and hospital records. Complete follow-up for all patient until death or discharge.

RESULTS

Seventy-seven patients (16% of the patients seen by a general practitioner) received parenteral antibiotics before hospital admission; 9 (12%) of them died. Of 402 patients who did not receive pre-hospital parenteral antibiotics, 26 (7%) died. The overall risk of case fatality among antibiotic-treated patients was increased with adjusted odds ratio (OR) = 2.4 (95% CI, 1.0-5.6). Meningococcus serogroup B was associated with increased case fatality in patients who received pre-hospital parenteral antibiotics (OR = 2.6; 95% CI, 0.8-8.3) in contrast to other serogroups. In Aarhus County there were no deaths in patients who received pre-hospital parenteral antibiotics, but in North Jutland County the case fatality was high (OR = 2.9; 95% CI, 1.2-6.8).

CONCLUSIONS

The efficiency of pre-hospital parenteral antibiotic treatment seems to be dependent on hospital care and may vary with the serogroup.

Period prevalence and case-fatality rate associated with distinctive clone complexes of Neisseria meningitidis serogroups B and C

In a recent 20-year Danish survey, Neisseria meningitidis phenotypes B:15:P1.7,16 and C:2a:P1.2,5 were associated with an increased case-fatality rate of meningococcal disease - 15% and 23% - compared to the case-fatality rate of 8% for any other strain. The aim of the present study was to investigate (i) the mutual genetic relatedness of strains with phenotype B:15:P1.7,16, phenotype C:2a:P1.2,5 or serologically related phenotypes; (ii) the changes in the prevalence of distinctive clone complexes over time; and (iii) whether distinctive clone complexes are associated with an increased case-fatality rate. During the period 1980-1999, 181 of a total of 315 invasive strains obtained in North Jutland County, Denmark, were chosen on the basis of serological characteristics for characterization by multilocus enzyme electrophoresis and ribotyping. Two major complexes were identified on the basis of electrophoretic type (ET): the ET-4/23 complex ( n=111), which included all B:15:P1.7,16 strains ( n=100), and the ET-15/25 complex ( n=44), which included all C:2a:P1.2,5 strains ( n=31). Two ribotype complexes were identified within the ET-4/23 complex and one within the ET-15/25 complex, all of which were designated clone complexes. All three clone complexes were associated with an increased case-fatality rate (13-20%). The results show that, among invasive Neisseria meningitidis B:15:P1.7,16, C:2a:P1.2,5 and phenotypically related strains, three distinctive clone complexes are more virulent than any other ET/ribotype combination.

Birth outcome of 1886 pregnancies after exposure to phenoxymethylpenicillin in utero

OBJECTIVE

To examine the risk of congenital abnormalities, preterm birth and low birth weight after exposure to phenoxymethylpenicillin in utero.

METHODS

A population-based follow-up study in the County of North Jutland, Denmark. Birth outcome for 1886 women, who redeemed prescriptions for phenoxymethylpenicillin during pregnancy was compared with the outcome for 9263 women who did not redeem any prescription during pregnancy.

RESULTS

The prevalence of congenital abnormalities in 654 users of phenoxymethylpenicillin with or without other drugs during the first trimester was 4.6% compared with 3.6% in the reference group, giving a prevalence odds ratio of 1.25 (95% CI: 0.84-1.86). The prevalence odds ratio was 1.35 (95% CI: 0.59-3.08) in 131 women who were exposed to phenoxymethylpenicillin only. Nine cardiovascular abnormalities were found, giving an adjusted prevalence odds ratio of 1.74 (95% CI: 0.83-3.65). The prevalence odds ratios of preterm birth and low birth weight were 0.83 (95% CI: 0.66-1.04) and 1.02 (95% CI: 0.71-1.47), respectively.

CONCLUSION

We found no significantly increased risk of congenital abnormalities, including cardiovascular abnormalities, preterm birth, or low birth weight in women who purchased phenoxymethylpenicillin during pregnancy.

Influence of plant growth on degradation of linear alkylbenzene sulfonate in sludge-amended soil

Widespread application of sewage sludge to agricultural soils in Denmark has led to concern about the possible accumulation and effects of linear alkylbenzene sulfonate (LAS) in the soil ecosystem. Therefore, we have studied the uptake and degradation of LAS in greenhouse pot experiments. Sewage sludge was incorporated into a sandy soil to give a range from very low to very high applications (0.4 to 90 Mg dry wt. ha(-1)). In addition, LAS was added as water solutions. The soil was transferred to pots and sown with barley (Hordeum vulgare L. cv. Apex), rape (Brassica napus L. cv. Hyola 401), or carrot (Daucus carota L.). Also, plant-free controls were established. For all additions there was no plant uptake above the detection limit at 0.5 mg LAS kg(-1) d.w, but plant growth stimulated the degradation. With a growth period of 30 d, LAS concentrations in soil from pots with rape had dropped from 27 to 1.4 mg kg(-1) dry wt., but in plant-free pots the concentration decreased only to 2.4 mg kg(-1) dry wt. When LAS was added as a spike, the final concentration in soil from planted pots was 0.7 mg kg(-1) dry wt., but in pots without plants the final concentration was much higher (2.5 mg kg(-1) dry wt.). During degradation, the relative fraction of homologues C10, C11, and C12 decreased, while C13 increased.

Casein and soya-bean protein have different effects on whole body protein turnover at the same nitrogen balance

The present study examined whether different proteins have different effects on whole-body protein turnover in adult rats. The rats were either starved, given a protein-free but energy-sufficient diet (1 MJ/kg body weight (BW) per d) or a diet containing intact casein, hydrolysed casein, or hydrolysed soya-bean protein at a level of 9.1 g/kg BW per d. The diets, which were isoenergetic with the same carbohydrate: fat ratio, were given as a continuous intragastric infusion for at least 4 d. During the last 19 h 15N-glycine (a primed continuous infusion) was given intragastrically and 15N was recovered from urinary ammonia and urea during isotope steady state for measurement of protein synthesis and protein degradation. Compared with starvation the protein-free diet decreased N excretion by 75%, probably by increasing the rate of reutilization of amino acids from endogenous proteins for protein synthesis. The protein diets produced a positive N balance which was independent of the protein source. Intact and hydrolysed casein increased protein synthesis 2.6- and 2.0-fold respectively, compared with the protein-free diet. Protein degradation increased 1.4- and 1.2-fold respectively. Hydrolysed soya-bean protein did not increase protein synthesis but decreased protein degradation by 35% compared with the protein-free diet. Compared with the hydrolysed soya-bean protein, intact casein resulted in 2.2- and 2.8-fold higher rates of protein synthesis and degradation respectively. These results are not easily explained by known sources of misinterpretation associated with the 15N-glycine method. Hydrolysed casein and hydrolysed soya-bean protein produced similar concentrations of insulin-like growth factor-1, insulin, glucagon, and corticosterone. The difference in amino acid composition between the dietary proteins was reflected in plasma amino acid composition and this is suggested to be responsible for the different effect on protein turnover. Preliminary results from this study have previously been published in abstract form (Nielsen et al. 1991).

A general approach for PCR-amplification and sequencing of chloroplast DNA from crude vascular plant and algal tissue

A universal and reliable sequencing approach suitable for evolutionary and phylogenetic studies of most plant species has been developed. The initial step in the approach is PCR with primers from conserved regions in the chloroplast genome. Prior to PCR a simple DNA extraction is carried out where lysed tissue is embedded in agarose and dialyzed. Due to the use of one biotinylated primer in the PCR, the PCR products can be bound to magnetic streptavidin-coated beads and then sequenced directly by the solid-phase approach. The regions used for sequencing and subsequent analyses are the intron of the trnL gene and the intergenic spacer between the trnL and the trnF genes in the chloroplast DNA. Comparisons of the sequences obtained from closely and distantly related species show that the different chloroplast DNA regions harbor variations suitable for phylogenetic inference from the subspecific to the interfamiliar level. The strategy can be used both for manual and automated sequencing.

Hyphal transport of 15 N-labelled nitrogen by a vesicular-arbuscular mycorrhizal fungus and its effect on depletion of inorganic soil N

Hyphal transport of nitrogen from a ¹⁵ N-labelled ammonium source by a VA-mycorrhizal fungus was studied under controlled experimental conditions. Cucumis sativus L. cv. Aminex (F1 hybrid) was grown alone or together with Glomus intraradices Schenck and Smith in containers with a hyphal compartment separated from the rooting medium by a fine nylon mesh. Lateral movement of the applied ¹⁵ N towards the roots was minimized by using a nitrification inhibitor (N-serve) and a hyphal buffer compartment. Recovery of ¹⁵ N by mycorrhizal and non-mycorrhizal plants was 6 and 0%, respectively, after a labelling period of 23 days. The corresponding figures, without N-serve added, were 4 and 7%. A prolongation of the labelling period by 8 days (N-serve applied) resulted in an increase in the ¹⁵ N recovery by mycorrhizal plants to 30% of the applied ¹⁵ N. Non-mycorrhizal plants contained only traces of ¹⁵ N. The external hyphae depleted the soil in the hyphal compartment efficiently for inorganic N. In contrast, hyphal compartments of control containers still contained considerable amounts of inorganic N. The ¹⁵ N assimilated by the external hyphae in one hyphal compartment was not translocated in significant amounts to the external hyphae in another hyphal compartment. The possible implication of this for inter-plant N transfer by VA hyphal connections is discussed.