A novel characterized multi-drug-resistant Pseudocitrobacter sp. isolated from a patient colonized while admitted to a tertiary teaching hospital

BACKGROUND

Reports of nosocomial infections typically describe recognised microorganisms. Here, a novel bacterial species was isolated, based on rectal swab screening for carbapenemases post-admission, then phenotypically and genetically characterized.

METHODS

Sensititre, Vitek and API kits, MALDI and Illumina MiSeq were employed before profiles and phylogeny were compared with other related species.

FINDINGS

Determined to be a possible Enterobacterales, the isolate was found to have 99.7% 16s rRNA identity to Pseudocitrobacter corydidari; an Asian cockroach-associated species. Given the highly conserved/low variability of 16S rRNA genes in Enterobacterales, average nucleotide identity (ANI) analysis compared the new isolate's genome with those of 18 Enterobacteriaceae species, including confirmed species of Pseudocitrobacter and unnamed Pseudocitrobacter species in the SILVA database. Of these, Pseudocitrobactercorydidari had the highest ANI at 0.9562. The published genome of the only known isolate of P.corydidari does not include Antimicrobial Resistance Genes (ARGs), with exception of potential drug efflux transporters. In contrast, our clinical isolate bears recognised antimicrobial resistance genes, including Klebsiella pneumoniae carbapenemase. The associated genome suggests resistance to carbapenems, β-lactams, sulfonamides, fluoroquinolones, macrolides, aminoglycosides and cephalosporins. Phenotypic antimicrobial resistance was confirmed.

CONCLUSION

Evident variations in ARG profiles, human colonization and origin in a clinically relevant niche that is geographically, physically and chemically disparate lend credibility for divergent evolution or, less likely, parallel evolution with P. corydidari. Genome data for this new species have been submitted to GENBANK using the proposed nomenclature Pseudocitrobacter limerickensis. The patient was colonized, rather than infected, and did not require antimicrobial treatment.

Large-scale characterization of hospital wastewater system microbiomes and clinical isolates from infected patients: profiling of multi-drug-resistant microbial species

BACKGROUND

Hospital-acquired infections (HAIs) and infectious agents exhibiting antimicrobial resistance (AMR) are challenges globally. Environmental patient-facing wastewater apparatus including handwashing sinks, showers and toilets are increasingly identified as sources of infectious agents and AMR genes.

AIM

To provide large-scale metagenomics analysis of wastewater systems in a large teaching hospital in the Republic of Ireland experiencing multi-drug-resistant HAI outbreaks.

METHODS

Wastewater pipe sections (N=20) were removed immediately prior to refurbishment of a medical ward where HAIs had been endemic. These comprised toilet U-bends, and sink and shower drains. Following DNA extraction, each pipe section underwent metagenomic analysis.

FINDINGS

Diverse taxonomic and resistome profiles were observed, with members of phyla Proteobacteria and Actinobacteria dominating (38.23 ± 5.68% and 15.78 ± 3.53%, respectively). Genomes of five clinical isolates were analysed. These AMR bacterial isolates were from patients >48 h post-admission to the ward. Genomic analysis determined that the isolates bore a high number of antimicrobial resistance genes (ARGs).

CONCLUSION

Comparison of resistome profiles of isolates and wastewater metagenomes revealed high degrees of similarity, with many identical ARGs shared, suggesting probable acquisition post-admission. The highest numbers of ARGs observed were those encoding resistance to clinically significant and commonly used antibiotic classes. Average nucleotide identity analysis confirmed the presence of highly similar or identical genomes in clinical isolates and wastewater pipes. These unique large-scale analyses reinforce the need for regular cleaning and decontamination of patient-facing hospital wastewater pipes and effective infection control policies to prevent transmission of nosocomial infection and emergence of AMR within potential wastewater reservoirs.

Locomotor play behavior evolves by random genetic drift but not as a correlated response to selective breeding for high voluntary wheel-running behavior

Locomotor play is vigorous and seemingly purposeless behavior, commonly observed in young mammals. It can be costly in terms of energy expenditure, increased injury risk, and predator exposure. The main hypothesized benefit of locomotor play is enhancement of neuromuscular development, with effects persisting into adulthood. We hypothesized that levels of locomotor play would have evolved as a correlated response to artificial selection for increased voluntary exercise behavior. We studied mice from 4 replicate lines bred for voluntary wheel running (High Runner or HR) at 6-8 weeks of age and four non-selected Control (C) lines. Mice were weaned at 21 days of age and play behavior was observed for generations 20 (22-24 days old), 68 (22-23 days old), and 93 (15 days old). We quantified locomotor play as (1) rapid, horizontally directed jerk-run sequences and (2) vertical "bouncing." We used focal sampling to continuously record behavior in cages containing 4-6 individuals during the first 2-3 h of the dark cycle. Observations were significantly repeatable between observers and days. A two-way, mixed-model simultaneously tested effects of linetype (HR vs. C), sex, and their interaction. Contrary to our hypothesis, HR and C lines did not differ in any generation, nor did we find sex differences. However, differences among the replicate HR lines and among the replicate C lines were detected, and may be attributed to the effects of random genetic drift (and possibly founder effects). Thus, play behavior did evolve in this selection experiment, but not as a correlated response to selection for voluntary exercise.

Prone positioning reduces frontal and hippocampal neuronal dysfunction in a murine model of ventilator-induced lung injury

Prone positioning is an established treatment for severe acute lung injury conditions. Neuronal dysfunction frequently occurs with mechanical ventilation-induced acute lung injury (VILI) and clinically manifests as delirium. We previously reported a pathological role for systemic interleukin 6 (IL-6) in mediating neuronal injury. However, currently no studies have investigated the relationship between prone or supine positioning and IL-6 mediated neuronal dysfunction. Here, we hypothesize that prone positioning mitigates neuronal injury, via decreased IL-6, in a model of VILI. VILI was induced by subjecting C57BL/6J mice to high tidal volume (35 cc/kg) mechanical ventilation. Neuronal injury markers [cleaved caspase-3 (CC3), c-fos, heat shock protein 90 (Hsp90)] and inflammatory cytokines (IL-6, IL-1β, TNF-α) were measured in the frontal cortex and hippocampus. We found statistically significantly less neuronal injury (CC3, c-Fos, Hsp90) and inflammatory cytokines (IL-6, IL-1β, TNF-α) in the frontal cortex and hippocampus with prone compared to supine positioning (p < 0.001) despite no significant group differences in oxygen saturation or inflammatory infiltrates in the bronchoalveolar fluid (p > 0.05). Although there were no group differences in plasma IL-6 concentrations, there was significantly less cortical and hippocampal IL-6 in the prone position (p < 0.0001), indicating supine positioning may enhance brain susceptibility to systemic IL-6 during VILI via the IL-6 trans-signaling pathway. These findings call for future clinical studies to assess the relationship between prone positioning and delirium and for investigations into novel diagnostic or therapeutic paradigms to mitigate delirium by reducing expression of systemic and cerebral IL-6.

Reduced Cell Surface Levels of C-C Chemokine Receptor 5 and Immunosuppression in Long Coronavirus Disease 2019 Syndrome

In an exploratory trial treating "long COVID" with the CCR5-binding antibody leronlimab, we observed significantly increased blood cell surface CCR5 in treated symptomatic responders but not in nonresponders or placebo-treated participants. These findings suggest an unexpected mechanism of abnormal immune downmodulation in some persons that is normalized by leronlimab. Clinical Trials Registration. NCT04678830.

Disruption of CCR5 signaling to treat COVID-19-associated cytokine storm: Case series of four critically ill patients treated with leronlimab

Coronavirus disease 2019 (COVID-19) is associated with considerable morbidity and mortality. The number of confirmed cases of infection with SARS-CoV-2, the virus causing COVID-19 continues to escalate with over 70 million confirmed cases and over 1.6 million confirmed deaths. Severe-to-critical COVID-19 is associated with a dysregulated host immune response to the virus, which is thought to lead to pathogenic immune dysregulation and end-organ damage. Presently few effective treatment options are available to treat COVID-19. Leronlimab is a humanized IgG4, kappa monoclonal antibody that blocks C–C chemokine receptor type 5 (CCR5). It has been shown that in patients with severe COVID-19 treatment with leronlimab reduces elevated plasma IL-6 and chemokine ligand 5 (CCL5), and normalized CD4/CD8 ratios. We administered leronlimab to 4 critically ill COVID-19 patients in intensive care. All 4 of these patients improved clinically as measured by vasopressor support, and discontinuation of hemodialysis and mechanical ventilation. Following administration of leronlimab there was a statistically significant decrease in IL-6 observed in patient A (p=0.034) from day 0–7 and patient D (p=0.027) from day 0–14. This corresponds to restoration of the immune function as measured by CD4+/CD8+ T cell ratio. Although two of the patients went on to survive the other two subsequently died of surgical complications after an initial recovery from SARS-CoV-2 infection.

•

Leronlimab is a monoclonal antibody in clinical trials to treat the cytokine storm.

•

Critically ill patients received leronlimab through compassionate use and had remarkable recoveries measured objectively.

•

The CCR5 receptor is important in recruiting inflammatory cells mainly T cells and macrophages.

•

Leronlimab disrupted this signal and may have been responsible for restoration of the immune system, improved survival and decrease in IL-6.

Biological/Genetic Regulation of Physical Activity Level: Consensus from GenBioPAC

PURPOSE

Physical activity unquestionably maintains and improves health; however, physical activity levels globally are low and not rising despite all the resources devoted to this goal. Attention in both the research literature and the public policy domain has focused on social-behavioral factors; however, a growing body of literature suggests that biological determinants play a significant role in regulating physical activity levels. For instance, physical activity level, measured in various manners, has a genetic component in both humans and nonhuman animal models. This consensus article, developed as a result of an American College of Sports Medicine-sponsored round table, provides a brief review of the theoretical concepts and existing literature that supports a significant role of genetic and other biological factors in the regulation of physical activity.

CONCLUSIONS

Future research on physical activity regulation should incorporate genetics and other biological determinants of physical activity instead of a sole reliance on social and other environmental determinants.

Prevention of tumorigenesis in mice by exercise is dependent on strain background and timing relative to carcinogen exposure

Among cancer diagnoses, colorectal cancer (CRC) is prevalent, with a lifetime risk of developing CRC being approximately 5%. Population variation surrounding the mean risk of developing CRCs has been associated with both inter-individual differences in genomic architecture and environmental exposures. Decreased risk of CRC has been associated with physical activity, but protective responses are variable. Here, we utilized a series of experiments to examine the effects of genetic background (strain), voluntary exercise (wheel running), and their interaction on azoxymethane (AOM)-induced intestinal tumor number and size in mice. Additionally, we investigated how the timing of exercise relative to AOM exposure, and amount of exercise, affected tumor number and size. Our results indicated that voluntary exercise significantly reduced tumor number in a strain dependent manner. Additionally, among strains where exercise reduced tumor number (A/J, CC0001/Unc) the timing of voluntary exercise relative to AOM exposure was crucial. Voluntary exercise prior to or during AOM treatment resulted in a significant reduction in tumor number, but exercise following AOM exposure had no effect. The results indicate that voluntary exercise should be used as a preventative measure to reduce risk for environmentally induced CRC with the realization that the extent of protection may depend on genetic background.

Effects of activity, genetic selection, and their interaction on muscle metabolic capacities and organ masses in mice

Chronic voluntary exercise elevates total daily energy expenditure (DEE) and food consumption, potentially resulting in organ compensation supporting nutrient extraction/utilization. Additionally, species with naturally higher DEE often have larger processing organs, which may represent genetic differences and/or phenotypic plasticity. We tested for possible adaptive changes in organ masses of 4 replicate lines of house mice selected (37 generations) for high running (HR lines) compared with 4 non-selected control (C) lines. Females were housed with or without wheel access for 13-14 weeks beginning at 53-60 days of age. In addition to organ compensation, chronic activity may also require an elevated aerobic capacity. Therefore, we also measured hematocrit and both citrate synthase activity and myoglobin concentration in heart and gastrocnemius. Both selection (HR vs. C) and activity (wheels vs. no wheels) significantly affected morphological and biochemical traits. For example, with body mass as a covariate, mice from HR lines had significantly higher hematocrit and larger ventricles, with more myoglobin. Wheel access lengthened the small intestine, increased relative ventricle and kidney size, and increased skeletal muscle citrate synthase activity and myoglobin concentration. As compared with C lines, HR mice had greater training effects for ventricle mass, hematocrit, large intestine length, and gastrocnemius citrate synthase activity. For ventricle and gastrocnemius citrate synthase activity, the greater training was explainable quantitatively as a result of greater wheel running (i.e., “more pain, more gain”). For hematocrit and large intestine length, differences were not related to amount of wheel running and instead indicate inherently greater adaptive plasticity in HR lines.

Long-term exercise in mice has sex-dependent benefits on body composition and metabolism during aging

Aging is associated with declining exercise and unhealthy changes in body composition. Exercise ameliorates certain adverse age‐related physiological changes and protects against many chronic diseases. Despite these benefits, willingness to exercise and physiological responses to exercise vary widely, and long‐term exercise and its benefits are difficult and costly to measure in humans. Furthermore, physiological effects of aging in humans are confounded with changes in lifestyle and environment. We used C57BL/6J mice to examine long‐term patterns of exercise during aging and its physiological effects in a well‐controlled environment. One‐year‐old male (n = 30) and female (n = 30) mice were divided into equal size cohorts and aged for an additional year. One cohort was given access to voluntary running wheels while another was denied exercise other than home cage movement. Body mass, composition, and metabolic traits were measured before, throughout, and after 1 year of treatment. Long‐term exercise significantly prevented gains in body mass and body fat, while preventing loss of lean mass. We observed sex‐dependent differences in body mass and composition trajectories during aging. Wheel running (distance, speed, duration) was greater in females than males and declined with age. We conclude that long‐term exercise may serve as a preventive measure against age‐related weight gain and body composition changes, and that mouse inbred strains can be used to characterize effects of long‐term exercise and factors (e.g. sex, age) modulating these effects. These findings will facilitate studies on relationships between exercise and health in aging populations, including genetic predisposition and genotype‐by‐environment interactions.

The 'Omics' of Voluntary Exercise: Systems Approaches to a Complex Phenotype

Predisposition to engage in exercise is highly variable and simultaneously influenced by the environment, complex genomics, and their interactions. Given the importance of exercise to health, understanding the underlying influences of variability is crucial. Here, we discuss murine systems approaches, focusing on 'omics', relevant to revealing the architecture of voluntary activity.

Genetic approaches in comparative and evolutionary physiology

Whole animal physiological performance is highly polygenic and highly plastic, and the same is generally true for the many subordinate traits that underlie performance capacities. Quantitative genetics, therefore, provides an appropriate framework for the analysis of physiological phenotypes and can be used to infer the microevolutionary processes that have shaped patterns of trait variation within and among species. In cases where specific genes are known to contribute to variation in physiological traits, analyses of intraspecific polymorphism and interspecific divergence can reveal molecular mechanisms of functional evolution and can provide insights into the possible adaptive significance of observed sequence changes. In this review, we explain how the tools and theory of quantitative genetics, population genetics, and molecular evolution can inform our understanding of mechanism and process in physiological evolution. For example, lab-based studies of polygenic inheritance can be integrated with field-based studies of trait variation and survivorship to measure selection in the wild, thereby providing direct insights into the adaptive significance of physiological variation. Analyses of quantitative genetic variation in selection experiments can be used to probe interrelationships among traits and the genetic basis of physiological trade-offs and constraints. We review approaches for characterizing the genetic architecture of physiological traits, including linkage mapping and association mapping, and systems approaches for dissecting intermediary steps in the chain of causation between genotype and phenotype. We also discuss the promise and limitations of population genomic approaches for inferring adaptation at specific loci. We end by highlighting the role of organismal physiology in the functional synthesis of evolutionary biology.

Dose-response effect of fluoride dentifrice on remineralisation and further demineralisation of erosive lesions: A randomised in situ clinical study

OBJECTIVE

The objective was to evaluate the ability of fluoride in a conventional, non-specialised sodium fluoride-silica dentifrice to promote tooth remineralisation and enamel fluoride uptake (EFU), and assess the resistance of the newly formed mineral to attack by dietary acid, across the concentration range used in mass-market dentifrices.

METHODS

Subjects wore a palatal appliance containing eight polished bovine enamel specimens, each including an early erosive lesion. In a randomised full-crossover sequence, 62 healthy subjects were treated with dentifrices containing four different fluoride concentrations: no fluoride; 250ppm, 1150ppm and 1426ppm fluoride. At each treatment visit, under supervision, subjects brushed with 1.5g dentifrice and rinsed once while wearing the appliance; the appliance was removed after a 4-h remineralisation period and effects on the enamel specimens determined. The primary efficacy variable was surface microhardness recovery (SMHR); others included EFU, relative erosion resistance (RER) and comparative erosion resistance.

RESULTS

Highly significant linear and, with the exception of SMHR, quadratic dose-response relationships were observed between all efficacy variables and fluoride concentration. For SMHR, EFU and RER, values for the different fluoride concentrations were statistically resolved from one another, with the exception of the two highest fluoride concentrations. The degree of remineralisation and the acid resistance of enamel after treatment were closely related to EFU.

CONCLUSION

After a single brushing, conventional non-specialised sodium fluoride-silica dentifrices promoted remineralisation of early enamel lesions, and imparted increased acid-resistance to the enamel surface, in a dose-dependent manner at least up to 1500ppm fluoride.

CLINICAL SIGNIFICANCE

Enamel erosive tissue loss is an increasing concern, associated with modern diets. This study demonstrated that sodium fluoride, in a conventional non-specialised dentifrice formulation, can promote repair of the earliest stages of enamel erosion after a single application, in a dose-dependent fashion across the fluoride concentration range used in mass-market dentifrices. This study is registered in the GlaxoSmithKline Study Register (ID RH01299), available at: www.gsk-clinicalstudyregister.com/study/RH01299.

Quantitative genomics of voluntary exercise in mice: transcriptional analysis and mapping of expression QTL in muscle

Motivation and ability both underlie voluntary exercise, each with a potentially unique genetic architecture. Muscle structure and function are one of many morphological and physiological systems acting to simultaneously determine exercise ability. We generated a large (n = 815) advanced intercross line of mice (G4) derived from a line selectively bred for increased wheel running (high runner) and the C57BL/6J inbred strain. We previously mapped quantitative trait loci (QTL) contributing to voluntary exercise, body composition, and changes in body composition as a result of exercise. Using brain tissue in a subset of the G4 (n = 244), we have also previously reported expression QTL (eQTL) colocalizing with the QTL for the higher-level phenotypes. Here, we examined the transcriptional landscape of hind limb muscle tissue via global mRNA expression profiles. Correlations revealed an ∼1,168% increase in significant relationships between muscle transcript expression levels and the same exercise and body composition phenotypes examined previously in the brain. The exercise trait most often significantly correlated with gene expression in the brain was running duration while in the muscle it was maximum running speed. This difference may indicate that time spent engaging in exercise behavior may be more influenced by central (neurobiological) mechanisms, while intensity of exercise may be largely controlled by peripheral mechanisms. Additionally, we used subsets of cis-acting eQTL, colocalizing with QTL, to identify candidate genes based on both positional and functional evidence. We discuss three plausible candidate genes (Insig2, Prcp, Sparc) and their potential regulatory role.

Exercise training effects on hypoxic and hypercapnic ventilatory responses in mice selected for increased voluntary wheel running

NEW FINDINGS

What is the central question of this study? We used experimental evolution to determine how selective breeding for high voluntary wheel running and exercise training (7-11 weeks) affect ventilatory chemoreflexes of laboratory mice at rest. What is the main finding and its importance? Selective breeding, although significantly affecting some traits, did not systematically alter ventilation across gas concentrations. As with most human studies, our findings support the idea that endurance training attenuates resting ventilation. However, little evidence was found for a correlation between ventilatory chemoreflexes and the amount of individual voluntary wheel running. We conclude that exercise 'training' alters respiratory behaviours, but these changes may not be necessary to achieve high levels of wheel running. Ventilatory control is affected by genetics, the environment and gene-environment and gene-gene interactions. Here, we used an experimental evolution approach to test whether 37 generations of selective breeding for high voluntary wheel running (genetic effects) and/or long-term (7-11 weeks) wheel access (training effects) alter acute respiratory behaviour of mice resting in normoxic, hypoxic and hypercapnic conditions. As the four replicate high-runner (HR) lines run much more than the four non-selected control (C) lines, we also examined whether the amount of exercise among individual mice was a quantitative predictor of ventilatory chemoreflexes at rest. Selective breeding and/or wheel access significantly affected several traits. In normoxia, HR mice tended to have lower mass-adjusted rates of oxygen consumption and carbon dioxide production. Chronic wheel access increased oxygen consumption and carbon dioxide production in both HR and C mice during hypercapnia. Breathing frequency and minute ventilation were significantly reduced by chronic wheel access in both HR and C mice during hypoxia. Selection history, while significantly affecting some traits, did not systematically alter ventilation across all gas concentrations. As with most human studies, our findings support the idea that endurance training (access to wheel running) attenuates resting ventilation. However, little evidence was found for a correlation at the level of the individual variation between ventilatory chemoreflexes and performance (amount of individual voluntary wheel running). We tentatively conclude that exercise 'training' alters respiratory behaviours, but these changes may not be necessary to achieve high levels of wheel running.

Quantitative trait loci for bone mineral density and femoral morphology in an advanced intercross population of mice

Osteoporosis, characterized by low levels of bone mineral density (BMD), is a prevalent medical condition in humans. We investigated its genetic and environmental basis by searching for quantitative trait loci (QTLs) affecting six skeletal (including three BMD) traits in a G10 advanced intercross population produced from crosses of mice from the inbred strain C57BL/6J with mice from a strain selected for high voluntary wheel running. The mice in this population were fed either a high-fat or a matched control diet throughout the study, allowing us to test for QTL by diet interactions for the skeletal traits. Our genome scan uncovered a number of QTLs, the great majority of which were different from QTLs previously found for these same traits in an earlier (G4) generation of the same intercross. Further, the confidence intervals for the skeletal trait QTLs were reduced from an average of 18.5 Mb in the G4 population to an equivalent of about 9 Mb in the G10 population. We uncovered a total of 50 QTLs representing 32 separate genomic sites affecting these traits, with a distal region on chromosome 1 harboring several QTLs with large effects on the BMD traits. One QTL was located on chromosome 5 at 4.0 Mb with a confidence interval spanning from 4.0 to 4.6 Mb. Only three protein coding genes reside in this interval, and one of these, Cyp51, is an attractive candidate as others have shown that developing Cyp51 knockout embryos exhibit shortened and bowed limbs and synotosis of the femur and tibia. Several QTLs showed significant interactions with sex, although only two QTLs interacted with diet, both affecting only mice fed the high-fat diet.

Genetic determinants of voluntary exercise

Variation in voluntary exercise behavior is an important determinant of long-term human health. Increased physical activity is used as a preventative measure or therapeutic intervention for disease, and a sedentary lifestyle has generally been viewed as unhealthy. Predisposition to engage in voluntary activity is heritable and induces protective metabolic changes, but its complex genetic/genomic architecture has only recently begun to emerge. We first present a brief historical perspective and summary of the known benefits of voluntary exercise. Second, we describe human and mouse model studies using genomic and transcriptomic approaches to reveal the genetic architecture of exercise. Third, we discuss the merging of genomic information and physiological observations, revealing systems and networks that lead to a more complete mechanistic understanding of how exercise protects against disease pathogenesis. Finally, we explore potential regulation of physical activity through epigenetic mechanisms, including those that persist across multiple generations.

Mice from lines selectively bred for high voluntary wheel running exhibit lower blood pressure during withdrawal from wheel access

Exercise is known to be rewarding and have positive effects on mental and physical health. Excessive exercise, however, can be the result of an underlying behavioral/physiological addiction. Both humans who exercise regularly and rodent models of exercise addiction sometimes display behavioral withdrawal symptoms, including depression and anxiety, when exercise is denied. However, few studies have examined the physiological state that occurs during this withdrawal period. Alterations in blood pressure (BP) are common physiological indicators of withdrawal in a variety of addictions. In this study, we examined exercise withdrawal in four replicate lines of mice selectively bred for high voluntary wheel running (HR lines). Mice from the HR lines run almost 3-fold greater distances on wheels than those from non-selected control lines, and have altered brain activity as well as increased behavioral despair when wheel access is removed. We tested the hypothesis that male HR mice have an altered cardiovascular response (heart rate, systolic, diastolic, and mean arterial pressure [MAP]) during exercise withdrawal. Measurements using an occlusion tail-cuff system were taken during 8 days of baseline, 6 days of wheel access, and 2 days of withdrawal (wheel access blocked). During withdrawal, HR mice had significantly lower systolic BP, diastolic BP, and MAP than controls, potentially indicating a differential dependence on voluntary wheel running in HR mice. This is the first characterization of a cardiovascular withdrawal response in an animal model of high voluntary exercise.

Exercise and diet affect quantitative trait loci for body weight and composition traits in an advanced intercross population of mice

Driven by the recent obesity epidemic, interest in understanding the complex genetic and environmental basis of body weight and composition is great. We investigated this by searching for quantitative trait loci (QTLs) affecting a number of weight and adiposity traits in a G(10) advanced intercross population produced from crosses of mice in inbred strain C57BL/6J with those in a strain selected for high voluntary wheel running. The mice in this population were fed either a high-fat or a control diet throughout the study and also measured for four exercise traits prior to death, allowing us to test for pre- and postexercise QTLs as well as QTL-by-diet and QTL-by-exercise interactions. Our genome scan uncovered a number of QTLs, of which 40% replicated QTLs previously found for similar traits in an earlier (G(4)) generation. For those replicated QTLs, the confidence intervals were reduced from an average of 19 Mb in the G(4) to 8 Mb in the G(10). Four QTLs on chromosomes 3, 8, 13, and 18 were especially prominent in affecting the percentage of fat in the mice. About of all QTLs showed interactions with diet, exercise, or both, their genotypic effects on the traits showing a variety of patterns depending on the diet or level of exercise. It was concluded that the indirect effects of these QTLs provide an underlying genetic basis for the considerable variability in weight or fat loss typically found among individuals on the same diet and/or exercise regimen.

Identification of quantitative trait loci influencing skeletal architecture in mice: emergence of Cdh11 as a primary candidate gene regulating femoral morphology

Bone strength is influenced by many properties intrinsic to bone, including its mass, geometry, and mineralization. To further advance our understanding of the genetic basis of bone-strength-related traits, we used a large (n = 815), moderately (G(4) ) advanced intercross line (AIL) of mice derived from a high-runner selection line (HR) and the C57BL/6J inbred strain. In total, 16 quantitative trait loci (QTLs) were identified that affected areal bone mineral density (aBMD) and femoral length and width. Four significant (p < .05) and one suggestive (p < .10) QTLs were identified for three aBMD measurements: total body, vertebral, and femoral. A QTL on chromosome (Chr.) 3 influenced all three aBMD measures, whereas the other four QTLs were unique to a single measure. A total of 10 significant and one suggestive QTLs were identified for femoral length (FL) and two measures of femoral width, anteroposterior (AP) and mediolateral (ML). FL QTLs were distinct from loci affecting AP and ML width, and of the 7 AP QTLs, only three affected ML. A QTL on Chr. 8 that explained 7.1% and 4.0% of the variance in AP and ML, respectively, was mapped to a 6-Mb region harboring 12 protein-coding genes. The pattern of haplotype diversity across the QTL region and expression profiles of QTL genes suggested that of the 12, cadherin 11 (Cdh11) was most likely the causal gene. These findings, when combined with existing data from gene knockouts, identify Cdh11 as a strong candidate gene within which genetic variation may affect bone morphology.

How to run far: multiple solutions and sex-specific responses to selective breeding for high voluntary activity levels

The response to uniform selection may occur in alternate ways that result in similar performance. We tested for multiple adaptive solutions during artificial selection for high voluntary wheel running in laboratory mice. At generation 43, the four replicate high runner (HR) lines averaged 2.85-fold more revolutions per day as compared with four non-selected control (C) lines, and females ran 1.11-fold more than males, with no sex-by-linetype interaction. Analysis of variance indicated significant differences among C lines but not among HR for revolutions per day. By contrast, average speed varied significantly among HR lines, but not among C, and showed a sex-by-linetype interaction, with the HR/C ratio being 2.02 for males and 2.45 for females. Time spent running varied among both HR and C lines, and showed a sex-by-linetype interaction, with the HR/C ratio being 1.52 for males but only 1.17 for females. Thus, females (speed) and males (speed, but also time) evolved differently, as did the replicate selected lines. Speed and time showed a trade-off among HR but not among C lines. These results demonstrate that uniform selection on a complex trait can cause consistent responses in the trait under direct selection while promoting divergence in the lower-level components of that trait.

Functional significance of genetic variation underlying limb bone diaphyseal structure

Limb bone diaphyseal structure is frequently used to infer hominin activity levels from skeletal remains, an approach based on the well-documented ability of bone to adjust to its loading environment during life. However, diaphyseal structure is also determined in part by genetic factors. This study investigates the possibility that genetic variation underlying diaphyseal structure is influenced by the activity levels of ancestral populations and might also have functional significance in an evolutionary context. We adopted an experimental evolution approach and tested for differences in femoral diaphyseal structure in 1-week-old mice from a line that had been artificially selected (45 generations) for high voluntary wheel running and non-selected controls. As adults, selected mice are significantly more active on wheels and in home cages, and have thicker diaphyses. Structural differences at 1 week can be assumed to primarily reflect the effects of selective breeding rather than direct mechanical stimuli, given that the onset of locomotion in mice is shortly after Day 7. We hypothesized that if genetically determined diaphyseal structure reflects the activity patterns of members of a lineage, then selected animals will have relatively larger diaphyseal dimensions at 1 week compared to controls. The results provide strong support for this hypothesis and suggest that limb bone cross sections may not always only reflect the activity levels of particular fossil individuals, but also convey an evolutionary signal providing information about hominin activity in the past.

Exercise, weight loss, and changes in body composition in mice: phenotypic relationships and genetic architecture

The regulation of body weight and composition is complex, simultaneously affected by genetic architecture, the environment, and their interactions. We sought to analyze the complex phenotypic relationships between voluntary exercise, food consumption, and changes in body weight and composition and simultaneously localize quantitative trait loci (QTL) controlling these traits. A large (n = 815) murine advanced intercross line (G(4)) was created from a reciprocal cross between a high-running line and the inbred strain C57BL/6J. Body weight and composition (% fat, % lean) were measured at 4, 6, and 8 wk of age. After measurements at 8 wk of age, mice were given access to running wheels, during which food consumption was quantified and after which body weight and composition were assessed to evaluate exercise-induced changes. Phenotypic correlations indicated that the relationship between exercise and overall change in weight and adiposity depended on body composition before the initiation of exercise. Interval mapping revealed QTL for body weight, % fat, and % lean at 4, 6, and 8 wk of age. Furthermore, QTL were observed for food consumption and changes in weight, % fat, and % lean in response to short-term exercise. Here we provide some clarity for the relationship between weight loss, reduction in adiposity, food consumption, and exercise. Simultaneously, we reinforce the genetic basis for body weight and composition with some independent loci controlling growth at different ages. Finally, we present unique QTL providing insight regarding variation in weight loss and reduction in adiposity in response to exercise.

Genetic architecture of voluntary exercise in an advanced intercross line of mice

Exercise is essential for health, yet the amount, duration, and intensity that individuals engage in are strikingly variable, even under prescription. Our focus was to identify the locations and effects of quantitative trait loci (QTL) controlling genetic predisposition for exercise-related traits, utilizing a large advanced intercross line (AIL) of mice. This AIL (G(4)) population originated from a reciprocal cross between mice with genetic propensity for increased voluntary exercise [high-runner (HR) line, selectively bred for increased wheel running] and the inbred strain C57BL/6J. After adjusting for family structure, we detected 32 significant and 13 suggestive QTL representing both daily running traits (distance, duration, average speed, and maximum speed) and the mean of these traits on days 5 and 6 (the selection criteria for HR) of a 6-day test conducted at 8 wk of age, with many co-localizing to similar genomic regions. Additionally, seven significant and five suggestive QTL were observed for the slope and intercept of a linear regression across all 6 days of running, some representing a combination of the daily traits. We also observed two significant and two suggestive QTL for body mass before exercise. These results, from a well-defined animal model, reinforce a genetic basis for the predisposition to engage in voluntary exercise, dissect this predisposition into daily segments across a continuous time period, and present unique QTL that may provide insight into the initiation, continuation, and temporal pattern of voluntary activity in mammals.

Erythropoietin elevates VO2,max but not voluntary wheel running in mice

Voluntary activity is a complex trait, comprising both behavioral (motivation, reward) and anatomical/physiological (ability) elements. In the present study, oxygen transport was investigated as a possible limitation to further increases in running by four replicate lines of mice that have been selectively bred for high voluntary wheel running and have reached an apparent selection limit. To increase oxygen transport capacity, erythrocyte density was elevated by the administration of an erythropoietin (EPO) analogue. Mice were given two EPO injections, two days apart, at one of two dose levels (100 or 300 microg kg(-1)). Hemoglobin concentration ([Hb]), maximal aerobic capacity during forced treadmill exercise (VO2,max) and voluntary wheel running were measured. [Hb] did not differ between high runner (HR) and non-selected control (C) lines without EPO treatment. Both doses of EPO significantly (P<0.0001) increased [Hb] as compared with sham-injected animals, with no difference in [Hb] between the 100 microg kg(-1) and 300 microg kg(-1) dose levels (overall mean of 4.5 g dl(-1) increase). EPO treatment significantly increased VO2,max by approximately 5% in both the HR and C lines, with no dosexline type interaction. However, wheel running (revolutions per day) did not increase with EPO treatment in either the HR or C lines, and in fact significantly decreased at the higher dose in both line types. These results suggest that neither [Hb] per se nor VO2,max is limiting voluntary wheel running in the HR lines. Moreover, we hypothesize that the decrease in wheel running at the higher dose of EPO may reflect direct action on the reward pathway of the brain.

Variation in within-bone stiffness measured by nanoindentation in mice bred for high levels of voluntary wheel running

The hierarchical structure of bone, involving micro-scale organization and interaction of material components, is a critical determinant of macro-scale mechanics. Changes in whole-bone morphology in response to the actions of individual genes, physiological loading during life, or evolutionary processes, may be accompanied by alterations in underlying mineralization or architecture. Here, we used nanoindentation to precisely measure compressive stiffness in the femoral mid-diaphysis of mice that had experienced 37 generations of selective breeding for high levels of voluntary wheel running (HR). Mice (n = 48 total), half from HR lines and half from non-selected control (C) lines, were divided into two experimental groups, one with 13-14 weeks of access to a running wheel and one housed without wheels (n = 12 in each group). At the end of the experiment, gross and micro-computed tomography (microCT)-based morphometric traits were measured, and reduced elastic modulus (E(r)) was estimated separately for four anatomical quadrants of the femoral cortex: anterior, posterior, lateral, and medial. Two-way, mixed-model analysis of covariance (ancova) showed that body mass was a highly significant predictor of all morphometric traits and that structural change is more apparent at the microCT level than in conventional morphometrics of whole bones. Both line type (HR vs. C) and presence of the mini-muscle phenotype (caused by a Mendelian recessive allele and characterized by a approximately 50% reduction in mass of the gastrocnemius muscle complex) were significant predictors of femoral cortical cross-sectional anatomy. Measurement of reduced modulus obtained by nanoindentation was repeatable within a single quadrant and sensitive enough to detect inter-individual differences. Although we found no significant effects of line type (HR vs. C) or physical activity (wheel vs. no wheel) on mean stiffness, anterior and posterior quadrants were significantly stiffer (P < 0.0001) than medial and lateral quadrants (32.67 and 33.09 GPa vs. 29.78 and 30.46 GPa, respectively). Our findings of no significant difference in compressive stiffness in the anterior and posterior quadrants agree with previous results for mice, but differ from those for large mammals. Integrating these results with others from ongoing research on these mice, we hypothesize that the skeletons of female HR mice may be less sensitive to the effects of chronic exercise, due to decreased circulating leptin levels and potentially altered endocannabinoid signaling.

Parent-of-origin effects on voluntary exercise levels and body composition in mice

Despite the health-related benefits of exercise, many people do not engage in enough activity to realize the rewards, and little is known regarding the genetic or environmental components that account for this individual variation. We created and phenotyped a large G(4) advanced intercross line originating from reciprocal crosses between mice with genetic propensity for increased voluntary exercise (HR line) and the inbred strain C57BL/6J. G(4) females (compared to males) ran significantly more when provided access to a running wheel and were smaller with a greater percentage of body fat pre- and postwheel access. Change in body composition resulting from a 6-day exposure to wheels varied between the sexes with females generally regulating energy balance more precisely in the presence of exercise. We observed parent-of-origin effects on most voluntary wheel running and body composition traits, which accounted for 3-13% of the total phenotypic variance pooled across sexes. G(4) individuals descended from progenitor (F(0)) crosses of HRfemale symbol and C57BL/6Jmale symbol ran greater distances, spent more time running, ran at higher maximum speeds/day, and had lower percent body fat and higher percent lean mass than mice descended from reciprocal progenitor crosses (C57BL/6Jfemale symbol x HRmale symbol). For some traits, significant interactions between parent of origin and sex were observed. We discuss these results in the context of sex dependent activity and weight loss patterns, the contribution of parent-of-origin effects to predisposition for voluntary exercise, and the genetic (i.e., X-linked or mtDNA variations), epigenetic (i.e., genomic imprinting), and environmental (i.e., in utero environment or maternal care) phenomena potentially modulating these effects.

An unclassifiable cellular myofibroblastic proliferation with an unusual clinical presentation

We present a case of a 50-year-old man with unusual extensive linear lesions on the right leg that had been present from the age of 2 years. As a child he had been treated with oral steroids under a working diagnosis of linear scleroderma. He went on to undergo multiple operations and skin-grafting procedures under the care of the plastic surgeons and presented to the dermatology department in 2004 because of itchy, scaly and painful lesions extending from the original area. Multiple biopsies had been taken, all showing similar histopathological features of a poorly differentiated dermal lesion composed of fibrohistiocytic cells arranged in a whorled pattern, similar to that seen in dermatofibroma. There was positive staining with vimentin and SMA, and negative staining with caldesmon, D33, CD34, S100 and factor 13a, indicating that the cell of origin was a myofibroblast. Clinically this extensive lesion does not fit the characteristics of a dermatofibroma. It also does not fit readily into any previously described fibrous tissue tumour condition, and, to our knowledge, is a unique case. The patient remains under close clinical observation given that there is no way of predicting the long-term prognosis, but to date no suspicious features have been seen.

Glycogen storage and muscle glucose transporters (GLUT-4) of mice selectively bred for high voluntary wheel running

To examine the evolution of endurance-exercise behaviour, we have selectively bred four replicate lines of laboratory mice (Mus domesticus) for high voluntary wheel running (;high runner' or HR lines), while also maintaining four non-selected control (C) lines. By generation 16, HR mice ran approximately 2.7-fold more than C mice, mainly by running faster (especially in females), a differential maintained through subsequent generations, suggesting an evolutionary limit of unknown origin. We hypothesized that HR mice would have higher glycogen levels before nightly running, show greater depletion of those depots during their more intense wheel running, and have increased glycogen synthase activity and GLUT-4 protein in skeletal muscle. We sampled females from generation 35 at three times (photophase 07:00 h-19:00 h) during days 5-6 of wheel access, as in the routine selection protocol: Group 1, day 5, 16:00 h-17:30 h, wheels blocked from 13:00 h; Group 2, day 6, 02:00 h-03:30 h (immediately after peak running); and Group 3, day 6, 07:00 h-08:30 h. An additional Group 4, sampled 16:00 h-17:30 h, never had wheels. HR individuals with the mini-muscle phenotype (50% reduced hindlimb muscle mass) were distinguished for statistical analyses comparing C, HR normal, and HR mini. HR mini ran more than HR normal, and at higher speeds, which might explain why they have been favored by the selective-breeding protocol. Plasma glucose was higher in Group 1 than in Group 4, indicating a training effect (phenotypic plasticity). Without wheels, no differences in gastrocnemius GLUT-4 were observed. After 5 days with wheels, all mice showed elevated GLUT-4, but HR normal and mini were 2.5-fold higher than C. At all times and irrespective of wheel access, HR mini showed approximately three-fold higher [glycogen] in gastrocnemius and altered glycogen synthase activity. HR mini also showed elevated glycogen in soleus when sampled during peak running. All mice showed some glycogen depletion during nightly wheel running, in muscles and/or liver, but the magnitude of this depletion was not large and hence does not seem to be limiting to the evolution of even-higher wheel running.

Selective breeding as a tool to probe skeletal response to high voluntary locomotor activity in mice

We present a novel mouse-model for the study of skeletal structure and evolution, based on selective breeding for high levels of voluntary wheel running. Whereas traditional models (originally inbred strains, more recently knockouts and transgenics) rely on the study of mutant or laboratory-manipulated phenotypes, we have studied changes in skeletal morphometrics resulting from many generations of artificial selection for high activity in the form of wheel running, in which mice engage voluntarily. Mice from the four replicate High Runner (HR) lines run nearly three times as many revolutions during days 5 and 6 of a 6-day exposure to wheels (1.12 m circumference). We have found significant changes in skeletal dimensions of the hind limbs, including decreased directional asymmetry, larger femoral heads, and wider distal femora. The latter two have been hypothesized as evolutionary adaptations for long-distance locomotion in hominids. Exercise-training studies involving experimental groups with and without access to wheels have shown increased diameters of both femora and tibiafibulae, and suggest genetic effects on trainability (genotype-by-environment interactions). Reanalysis of previously published data on bone masses of hind limbs revealed novel patterns of change in bone mass associated with access to wheels for 2 months. Without access to wheels, HR mice have significantly heavier tibiafibulae and foot bones, whereas with chronic access to wheels, a significant increase in foot bone mass that was linearly related to increases in daily wheel running was observed. Mice exhibiting a recently discovered small-muscle phenotype ("mini-muscle," [MM] caused by a Mendelian recessive gene), in which the mass of the triceps surae muscle complex is ∼50% lower than in normal individuals, have significantly longer and thinner bones in the hind limb. We present new data for the ontogenetic development of muscle mass in Control, HR, and MM phenotypes in mice of 1-7 weeks postnatal age. Statistical comparisons reveal highly significant differences both in triceps surae mass and mass-corrected triceps surae mass between normal and MM mice at all but the postnatal age of 1 week. Based on previously observed differences in distributions of myosin isoforms in adult MM mice, we hypothesize that a reduction of myosin heavy-chain type-IIb isoforms with accounts for our observed ontogenetic changes in muscle mass.

Fine mapping of "mini-muscle," a recessive mutation causing reduced hindlimb muscle mass in mice

Prolonged selective breeding of Hsd:ICR mice for high levels of voluntary wheel running has favored an unusual phenotype (mini-muscle [MM]), apparently caused by a single Mendelian recessive allele, in which hindlimb muscle mass is reduced by almost 50%. We recently described the creation and phenotypic characterization of a population suitable for mapping the genomic location of the MM gene. Specifically, we crossed females from a high-runner line fixed for the MM allele with male C57BL/6J. F1 males were then backcrossed to the MM parent females. Backcross (BC) mice exhibited a 50:50 ratio of normal to MM phenotypes. Here, we report on linkage mapping of MM in this BC population to a 2.6335-Mb interval on MMU11. This region harbors approximately 100 expressed or predicted genes, many of which have known roles in muscle development and/or function. Identification of the genetic variation that underlies MM could potentially be very important in understanding both normal muscle function and disregulation of muscle physiology leading to disease.

Phenotypic effects of the "mini-muscle" allele in a large HR x C57BL/6J mouse backcross

From outbred Hsd:ICR mice, we selectively bred 4 replicate lines for high running (High-Runner [HR] lines) on wheels while maintaining 4 nonselected lines as controls (C lines). An apparent Mendelian recessive, the "mini-muscle" (MM) allele, whose main phenotypic effect is to reduce hindlimb muscle mass by 50%, was discovered in 2 HR lines and 1 C line. This gene of major effect has gone to fixation in one selected line, remains polymorphic in another, and is now undetectable in the one C line. Homozygotes exhibit various pleiotropic effects, including a doubling of mass-specific muscle aerobic capacity, and larger hearts, livers, and spleens. To create a population suitable for mapping the genomic location of the MM allele and to better characterize its pleiotropic effects, we crossed females fixed for the MM allele with male C57BL/6J. F(1) males were then backcrossed to the MM parent females. Backcross (BC) mice (N = 404) were dissected, and a 50:50 ratio of normal to MM phenotype was observed with no overlap in relative muscle mass. In the BC, analysis of covariance revealed that MM individuals ran significantly more on days 5 and 6 of a 6-day exposure to running wheels (as in the routine selective-breeding protocol), were smaller in body mass, and had larger ventricles and spleens.

Phenotypic plasticity and experimental evolution

Natural or artificial selection that favors higher values of a particular trait within a given population should engender an evolutionary response that increases the mean value of the trait. For this prediction to hold, the phenotypic variance of the trait must be caused in part by additive effects of alleles segregating in the population, and also the trait must not be too strongly genetically correlated with other traits that are under selection. Another prediction, rarely discussed in the literature, is that directional selection should favor alleles that increase phenotypic plasticity in the direction of selection, where phenotypic plasticity is defined as the ability of one genotype to produce more than one phenotype when exposed to different environments. This prediction has received relatively little empirical attention. Nonetheless, many laboratory experiments impose selection regimes that could allow for the evolution of enhanced plasticity (e.g. desiccation trials with Drosophila that last for several hours or days). We review one example that involved culturing of Drosophila on lemon for multiple generations and then tested for enhanced plasticity of detoxifying enzymes. We also review an example with vertebrates that involves selective breeding for high voluntary activity levels in house mice, targeting wheel-running behavior on days 5+6 of a 6-day wheel exposure. This selection regime allows for the possibility of wheel running itself or subordinate traits that support such running to increase in plasticity over days 1–4 of wheel access. Indeed, some traits, such as the concentration of the glucose transporter GLUT4 in gastrocnemius muscle, do show enhanced plasticity in the selected lines over a 5–6 day period. In several experiments we have housed mice from both the Selected (S) and Control (C) lines with or without wheel access for several weeks to test for differences in plasticity (training effects). A variety of patterns were observed, including no training effects in either S or C mice, similar changes in both the S and C lines, greater changes in the S lines but in the same direction in the C lines, and even opposite directions of change in the S and C lines. For some of the traits that show a greater training effect in the S lines, but in the same direction as in C lines, the greater effect can be explained statistically by the greater wheel running exhibited by S lines (`more pain, more gain'). For others, however, the differences seem to reflect inherently greater plasticity in the S lines (i.e. for a given amount of stimulus, such as wheel running/day, individuals in the S lines show a greater response as compared with individuals in the C lines). We suggest that any selection experiment in which the selective event is more than instantaneous should explore whether plasticity in the appropriate (adaptive) direction has increased as a component of the response to selection.

Evaluation of a desensitizing test dentifrice using an in situ erosion remineralization model

OBJECTIVE

To evaluate, in an in situ remineralization model, the ability of a low abrasion fluoride dentifrice containing potassium nitrate to enhance the remineralization of enamel that was previously subjected to an in vitro dietary erosion challenge.

METHODOLOGY

Thirteen subjects completed a single-blind (to specimen analyst) crossover design study with four randomly assigned dentifrice treatments: placebo dentifrice (0 ppm F; PD); dose response control dentifrice (250 ppm F; DD); clinically tested fluoride dentifrice (1100 ppm F; FD); and test dentifrice (1150 ppm F + 5% KNO3; TD). Each subject wore a palatal appliance holding eight bovine enamel blocks that were previously exposed for 25 minutes to an in vitro erosive challenge with grapefruit juice. Surface microhardness (SMH) was determined prior to the erosive challenge (baseline), after the in vitro erosive challenge, after in situ remineralization, and after a second in vitro erosive challenge. Statistical analyses included ANOVA and pair-wise comparisons between treatments, testing at a 5% significance level.

RESULTS

The mean percent SMH recovery (SD) was 20.4 (7.7)a for PD; 27.4 (5.9)b for DD; 29.5 (8.9)bc for FD; 33.4 (6.7)c for TD. The mean percent net erosion resistance (SD) was -57.7 (10.8)a for PD; -41.3 (11.6)b for DD; -28.7 (9.7)c for FD; -23.6 (7.3)c for TD. Different superscript letters following the means imply statistically significant differences between groups for each response.

CONCLUSION

The test dentifrice was shown to significantly enhance the remineralization of enamel previously subjected to an erosion challenge.

Experimental evolution and phenotypic plasticity of hindlimb bones in high-activity house mice

Studies of rodents have shown that both forced and voluntary chronic exercise cause increased hindlimb bone diameter, mass, and strength. Among species of mammals, "cursoriality" is generally associated with longer limbs as well as relative lengthening of distal limb segments, resulting in an increased metatarsal/femur (MT/F) ratio. Indeed, we show that phylogenetic analyses of previously published data indicate a positive correlation between body mass-corrected home range area and both hindlimb length and MT/F in a sample of 19 species of Carnivora, although only the former is statistically significant in a multiple regression. Therefore, we used an experimental evolution approach to test for possible adaptive changes (in response to selective breeding and/or chronic exercise) in hindlimb bones of four replicate lines of house mice bred for high voluntary wheel running (S lines) for 21 generations and in four nonselected control (C) lines. We examined femur, tibiafibula, and longest metatarsal of males housed either with or without wheel access for 2 months beginning at 25-28 days of age. As expected from previous studies, mice from S lines ran more than C (primarily because the former ran faster) and were smaller in body size (both mass and length). Wheel access reduced body mass (but not length) of both S and C mice. Analysis of covariance (ANCOVA) revealed that body mass was a statistically significant predictor of all bone measures except MT/F ratio; therefore, all results reported are from ANCOVAs. Bone lengths were not significantly affected by either linetype (S vs. C) or wheel access. However, with body mass as a covariate, S mice had significantly thicker femora and tibiafibulae, and wheel access also significantly increased diameters. Mice from S lines also had heavier feet than C, and wheel access increased both foot and tibiafibula mass. Thus, the directions of evolutionary and phenotypic adaptation are generally consistent. Additionally, S-line individuals with the mini-muscle phenotype (homozygous for a Mendelian recessive allele that halves hindlimb muscle mass [Garland et al., 2002, Evolution 56:1,267-1,275]) exhibited significantly longer and thinner femora and tibiafibulae, with no difference in bone masses. Two results were considered surprising. First, no differences were found in the MT/F ratio (the classic indicator of cursoriality). Second, we did not find a significant interaction between linetype and wheel access for any trait, despite the higher running rate of S mice.

Effects of size, sex, and voluntary running speeds on costs of locomotion in lines of laboratory mice selectively bred for high wheel-running activity

Selective breeding for over 35 generations has led to four replicate (S) lines of laboratory house mice (Mus domesticus) that run voluntarily on wheels about 170% more than four random-bred control (C) lines. We tested whether S lines have evolved higher running performance by increasing running economy (i.e., decreasing energy spent per unit of distance) as a correlated response to selection, using a recently developed method that allows for nearly continuous measurements of oxygen consumption (VO2) and running speed in freely behaving animals. We estimated slope (incremental cost of transport [COT]) and intercept for regressions of power (the dependent variable, VO2/min) on speed for 49 males and 47 females, as well as their maximum VO2 and speeds during wheel running, under conditions mimicking those that these lines face during the selection protocol. For comparison, we also measured COT and maximum aerobic capacity (VO2max) during forced exercise on a motorized treadmill. As in previous studies, the increased wheel running of S lines was mainly attributable to increased average speed, with males also showing a tendency for increased time spent running. On a whole-animal basis, combined analysis of males and females indicated that COT during voluntary wheel running was significantly lower in the S lines (one-tailed P=0.015). However, mice from S lines are significantly smaller and attain higher maximum speeds on the wheels; with either body mass or maximum speed (or both) entered as a covariate, the statistical significance of the difference in COT is lost (one-tailed P> or =0.2). Thus, both body size and behavior are key components of the reduction in COT. Several statistically significant sex differences were observed, including lower COT and higher resting metabolic rate in females. In addition, maximum voluntary running speeds were negatively correlated with COT in females but not in males. Moreover, males (but not females) from the S lines exhibited significantly higher treadmill VO2max as compared to those from C lines. The sex-specific responses to selection may in part be consequences of sex differences in body mass and running style. Our results highlight how differences in size and running speed can account for lower COT in S lines and suggest that lower COT may have coadapted in response to selection for higher running distances in these lines.

Fluoride intake from foods, beverages and dentifrice by young children in communities with negligibly and optimally fluoridated water: a pilot study

While the level of fluoride intake that affords optimal cariostatic efficacy without causing dental fluorosis is not precisely known, it has been suggested that the threshold of fluoride exposure above which fluorosis may occur is between 0.05 and 0.07 mg/kg/day.

OBJECTIVE

To monitor and compare fluoride intake from diet and dentifrice use (theoretical F: 0.10-0.11%) by three groups of 16- to 40-month-old children: two groups living in the negligibly water-fluoridated communities of San Juan, Puerto Rico, and Connersville, Indiana, and the third group residing in the optimally water-fluoridated region of Indianapolis, Indiana.

METHODS

Fluoride intake from diet was monitored by the "duplicate plate" method, and fluoride ingested from dentifrice was determined by subtracting the amount of fluoride recovered after brushing from the amount originally placed on the child's toothbrush.

RESULTS

The mean combined amount of fluoride ingested daily by children living in the negligibly fluoridated communities was not significantly different from that ingested by children in the fluoridated community. The major component of fluoride ingested by children in the negligibly fluoridated communities came from fluoridated dentifrice, and in the fluoridated area children ingested as much fluoride from toothpaste as they did from beverages. In San Juan mean daily fluoride intake was within the estimated range for safe fluoride exposure; however, in the "halo" community of Connersville and in Indianapolis, daily fluoride ingested by many of the children may have exceeded this level.

CONCLUSION

Attention needs to be given, in negligibly water-fluoridated as well as in optimally water-fluoridated communities, to reducing the daily intake of fluoride by young children in order to avoid putting them at risk of developing dental fluorosis.

Dental fluorosis in children residing in communities with different water fluoride levels: 33-month follow-up

PURPOSE

The purpose of these examinations was to monitor changes, in the prevalence of dental fluorosis.

METHODS

In February 1992 and December 1994, children who were residents of one of three communities with varying levels of fluoride in their communal water supply were examined for dental fluorosis. Since some children were available at both examination periods, it was also possible to determine changes in the incidence of dental fluorosis.

RESULTS

The prevalence of fluorosis increased by approximately 14%, 20%, and 6% in the negligibly, optimally, and 4X optimally fluoridated communities, respectively. In the negligibly and optimally fluoridated communities, the incidence of dental fluorosis increased by 12% and 7%, respectively. In the 4X optimally fluoridated community, all the children examined had evidence of fluorosis at both examinations.

CONCLUSION

Fluoride continues to be the primary therapeutic agent for the prevention of dental caries in adults and children. With the downward adjustment in the fluoride supplement schedule, continued monitoring of the prevalence of dental fluorosis in young children is needed to determine if any additional steps are even necessary to restrict fluoride intake during the years that enamel formation is occurring.

Ambient but not incremental oxidant generation effects intercellular adhesion molecule 1 induction by tumour necrosis factor alpha in endothelium

Proinflammatory cytokines upregulate endothelial adhesion molecule expression, thereby initiating the microvascular inflammatory response. We re-evaluated the reported role of reactive oxygen metabolites (ROMs) in signalling upregulation of intercellular adhesion molecule 1 (ICAM-1) on endothelial cells by tumour necrosis factor alpha (TNF-alpha) in vitro. TNF-alpha upregulation of endothelial-cell ICAM-1 expression was inhibited by the cell-permeable antioxidants, or by the adenovirus-mediated intracellular overexpression of Cu,Zn-superoxide dismutase, but not by the exogenous (extracellular) administration of the cell-impermeable antioxidants, superoxide dismutase and/or catalase. This ICAM-1 upregulation was also inhibited by inhibitors of NADH dehydrogenase, cytochrome bc1 complex and NADPH oxidase. However, a measurable increase in net cellular ROM generation in response to TNF-alpha was not seen using four disparate sensitive ROM assays. Moreover, the stimulation of exogenous or endogenous ROM generation did not upregulate ICAM-1, nor enhance ICAM-1 upregulation by TNF-alpha. These findings suggest that an ambient background flux of ROMs, generated intracellularly, but not their net incremental generation, is necessary for TNF-alpha to induce ICAM-1 expression in endothelium in vitro.

Protein tyrosine phosphorylation mediates TNF-induced endothelial-neutrophil adhesion in vitro

Proinflammatory cytokines initiate the vascular inflammatory response via the upregulation of adhesion molecules on the luminal endothelial surface. We investigated directly the role of protein tyrosine phosphorylation in the upregulation of the endothelial adhesion molecules, intercellular adhesion molecule 1 (ICAM-1) and E-selectin, and the consequent adhesion of neutrophils, after tumor necrosis factor (TNF)-alpha-stimulation of human aortic endothelial cells in vitro. Time- and dose-dependent TNF-alpha-stimulated ICAM-1 and E-selectin upregulation and neutrophil adhesion each were suppressed by tyrosine kinase inhibitors, including genistein (200 microM), but not genistein, its isoflavone analog without tyrosine kinase inhibitory activity. Tyrphostin AG 126, a synthetic selective tyrosine kinase inhibitor, also suppressed ICAM-1 and E-selectin upregulation and neutrophil adhesion, each in a dose-dependent manner, whereas tyrphostin AG 1288 had no effect. Tyrosine phosphorylation of two proteins (85 and 145 kDa in the cytoskeleton fraction) found minutes after TNF-alpha-stimulation was also inhibited by genistein. These findings suggest that, in endothelial cells, TNF-alpha upregulates ICAM-1 and E-selectin expression and consequent neutrophil adhesion via protein tyrosine phosphorylation.

An in situ interproximal model for studying the effect of fluoride on enamel

This crossover study determined the ability of an interproximal, intra-oral model to demonstrate a fluoride dose response to 0-, 250- and 1,100-ppm fluoride (sodium fluoride) dentifrices with respect to fluoride uptake into, and remineralization of, incipient subsurface enamel lesions. Following a 1 week 'lead in' period during which 30 panelists were randomly assigned to use one of the products, two enamel specimens with artificial carious lesions were mounted into a specially designed functional partial denture worn by each panelist. Panelists continued to brush three times daily with their test dentifrice for 4 weeks, after which the specimens were removed and analyzed for fluoride uptake and remineralization. The procedure was repeated until each panelist had followed all three treatment regimens. Fluoride analyses were performed using a microdrill biopsy technique, and mineral content changes were determined by transverse microradiography. Fluoride uptake data were significantly different (p < 0.01) for all three products with the effect of 1,100 ppm F > 250 ppm F > placebo. The 1,100 ppm F dentifrice also effected significantly greater remineralization (p < 0.01) than did the 250-ppm-F or placebo dentifrices. Relative efficacy of the three fluoride dentifrices tested in this study was similar to that established in a clinical trial, and, therefore, supports the use of this model for in situ studies of the effects of fluoride-containing products on enamel lesions.

Orientation anisotropy and strabismus

Monocular contrast sensitivity (CS) measurements were obtained in the two principal meridians of eight constant unilateral strabismic subjects and four subjects diagnosed with alternating strabismus. The results indicated that: (1) the CS of both the fellow and deviating eyes of patients with a constant unilateral deviation is significantly less than that of visually normal eyes at high spatial frequencies; (2) both the fellow and deviating eyes reveal a significant reduction in CS to vertically oriented gratings. This effect is frequency-specific, occurring only at the highest spatial frequencies; (3) the magnitude of the orientation anisotropy did not vary systematically with the degree of amblyopia; and (4) a mild orientation anisotropy was observed in only three of the eight alternating strabismic eyes tested. The etiology of the vertical effect is examined with respect to the role of anomalous binocular competition, suppression and abnormal eye movements.

Lack of effect of long-term fluoride ingestion on blood chemistry and frequency of sister chromatid exchange in human lymphocytes

Two studies were conducted to assess the potential for adverse physiologic and genotoxic effects of long-term fluoride ingestion in adults residing in three communities with varying water fluoride levels (0.2 ppm, 1.0 ppm, and 4.0 ppm). All were long-time (> or = 30 years) residents of their respective communities. Plasma and urine samples were collected for fluoride analyses. Additional plasma was collected to determine blood chemistry, and plasma lymphocytes were examined to determine the frequency of sister chromatid exchange. Significant differences in urine (P = 0.001) and plasma (P = 0.0001) fluoride levels were found in the three communities. Seven of the blood parameters were statistically different among the communities, although all were within the defined normal range of the pathology laboratory. Sister chromatid exchange frequency was statistically higher in the 4.0 ppm fluoride community as compared to the other communities. Because of the higher SCE frequency in the 4.0 ppm fluoride community, a second study was performed to determine if the increased frequency was potentially related to the fluoride level of the communal water supply. Of the 58 adults recruited; 30 had used city water and 28 had used well water (< or = 0.3 ppm fluoride) as their principal water source for 30 years. Data analyses showed that the sister chromatid exchange frequency did not differ between the groups, indicating that the increased sister chromatid exchange frequency was not related to the fluoride level of the communal water. The investigation provided evidence that the long-term ingestion of water containing 4.0 ppm fluoride did not have any clinically important physiologic or genotoxic effects in healthy adults.

Active minimisation of radiation scatter during breast radiotherapy: management implications for young patients with good-prognosis primary neoplasms

BACKGROUND AND PURPOSE

Radiotherapy is used to reverse or prevent local tumour growth but is also a carcinogen in its own right. A recent audit of post-radiotherapy second malignancies in this institution revealed a striking preponderance of tumours originating near the outside edge of the treatment field. Since this finding suggests the existence of a critical subtherapeutic dose range predisposing to tumourigenesis, we attempted to define and reduce this radiation scatter dose.

MATERIALS AND METHODS

We undertook a dosimetric review of 6 MV scatter from a linear accelerator in sites matching the putative tumourigenic region, and then extended this analysis to patients and tissue phantoms.

RESULTS

A wide range of radiation scatter doses was confirmed-for example, doses 3 cm from the field edge varied from 1.7 to 22% of the therapeutic dose depending upon the field parameters. Scatter doses were then assessed in a sample of eight patients undergoing standard breast radiotherapy. Contralateral breast sites 4-12 cm from the midline received 4-10% of the therapeutic dose, or 200-500 cGy for a 50 Gy treatment, approximating historical estimates of the tumourigenic range. The deep component of this scatter dose from medial field breast irradiation was reduced 19% simply by replacing the 15 degrees medial tangential field wedge with a 30 degrees lateral wedge. Other manoeuvres which reduced contralateral breast dose by up to 46% included making the posterior field edges co-planar and shielding the breast during medial field irradiation.

CONCLUSIONS

These results suggest that the risk of radiogenic second malignancies could be significantly decreased by careful attention to the treatment details. Greater awareness of these measures may prove particularly relevant to the conservative management of young patients with good-prognosis breast neoplasms such as ductal carcinoma in situ.

Activated clotting time differential is a superior method of monitoring anticoagulation following coronary angioplasty

The standard high-range activated clotting time (sHR ACT) is used to monitor anticoagulation postangioplasty (PTCA), but may be unreliable. We assessed the accuracy of a new method we termed the ACT differential (ACT Diff), obtained by measuring the difference between an sHR ACT and a heparinase ACT from the same sample. Heparinase removes heparin from its sample and provides a current heparin-free baseline. For phase 1 of the study, the sHR ACT, ACT Diff, and laboratory APTT were measured in 250 samples from 75 PTCA patients. In 125 samples with an APTT prolonged but within measurement range, linear regression against the APTT was performed. The correlation coefficient was 0.74 for the ACT Diff and 0.24 for the sHR ACT. An ACT Diff of 15-25 sec was found to equal an APTT of 2.5-3.5 x control. In 50 samples with a normal activated partial thromboplastin time (APT), there was good differentiation by the ACT Diff of results from those adequately heparinized, with a value of 0.9 +/- 4.4 sec. The sHR ACT was 114 +/- 15.5 sec, and could not reliably distinguish between anticoagulated and nonanticoagulated samples. In 75 samples obtained with a high APTT (above measurement range), the ACT Diff was > 30 sec in 95% of samples, and again this allowed differentiation from therapeutic samples. The equivalent sHR ACT was 148 sec, and could not reliably distinguish between anticoagulated and overanticoagulated samples as the ACT Diff could. In phase 2, to examine the clinical usefulness of the ACT Diff, 286 patients were managed post-PTCA by starting heparin when ACT Diff fell to < 50 sec, maintaining ACT Diff at 15-25 sec during heparin infusions, and following cessation of heparin, by removing sheaths when the ACT Diff was < 7 sec. These patients were compared to a control group of 250 patients. Major bleeding (5% vs. 0.5%, P < 0.005) and minor bleeding (30% vs. 13%, P < 0.001) were significantly reduced in the group managed using the ACT Diff. The reduction in bleeding was thought to be due to the rapid availability of reliable results. Abrupt closure was low in both groups (0% with ACT Diff vs. 0.8%). No other thrombotic events occurred. Following phases 1 and 2, the ACT Diff replaced the APTT in all PTCA patients at this institution. In the 18 mo from July 1993, 1,104 patients were managed this way. Incidence of major bleeding (0.2%), transfusion requirement (0.1%), false anneurysm (0.6%), and abrupt closure during heparin infusion (0.1%) remained low. In conclusion, the ACT Diff is more accurate than an sHR ACT, and its clinical use in PTCA patients is associated with a very low incidence of complications from anticoagulation. Its routine use should be considered by units unable to obtain rapid APTT results.

Elemental analysis of femoral bone from patients with fractured neck of femur or osteoarthrosis

The elemental composition of bone has been determined by inductively coupled atomic emission and mass spectrometry to test the hypothesis that changes in major or minor elemental concentrations may contribute to the risk of fracture. Femoral bone was obtained from patients at operation for the treatment of fracture and compared with that of patients with osteoarthrosis and a necropsy control group. The data suggest that there are no major differences in bone elemental composition in patients with fractures compared with the control group. Bone adjacent to joints with osteoarthrosis tends to be less mineralized (per unit trabecular bone volume) than control bone and bone from fracture patients, and has significantly lower concentrations of boron, lead and, zinc. These observations may reflect the more rapid turnover of bone close to the arthritic joint.

Palliation of obstructive nephropathy due to malignancy

OBJECTIVE

To conduct a prospective study of patients with malignant obstructive uropathy treated actively by percutaneous nephrostomy and J-J ureteric stents.

PATIENTS AND METHODS

Forty-two patients (27 men, 15 women, median age 62 years, range 29-83) with obstructive nephropathy secondary to malignancy underwent urinary diversion followed, where appropriate, by active treatment of the underlying cancer.

RESULTS

The median survival of all patients was 133 (range 7-712) days. Seventeen patients (40%) survived for > 6 months and five (12%) for < 1 month. Patients who had received no prior therapy and for whom further therapeutic options were available were more likely to benefit from urinary diversion. In nine patients (21%) nephrostomy insertion failed to relieve renal failure. In 20 patients (48%) obstructive nephropathy recurred. The procedure was complicated by urinary tract or nephrostomy site infection in 16 patients, by septicaemia in six patients, by percutaneous urine leak in 13 patients and by pelvi-calyceal perforation in two patients, but not by haemorrhage or death. The median percentage of the patients' remaining life which was spent in hospital was 23.6% (range 2.2-100).

CONCLUSIONS

Patients likely to benefit from nephrostomy were those for whom there were therapeutic options available for the treatment of their malignancy. Prolonged survival is possible in obstructive nephropathy secondary to malignancy, which should no longer be cited as an absolute contra-indication to urinary diversion. Patients unlikely to benefit from urinary diversion can also be identified and they should not routinely undergo this intervention.

Dental fluorosis and caries prevalence in children residing in communities with different levels of fluoride in the water

OBJECTIVES

This study investigated the prevalence of dental fluorosis and caries in 7-14-year-old children residing in communities with negligible (NF: 0.2 ppm), optimal (OPF: 1.0 ppm), and four-times optimal (4X OPF: 4.0 ppm) naturally occurring fluoride in their water systems.

METHODS

Examinations were performed on 344 children who were lifetime residents of their communities.

RESULTS

Whether using the tooth surface index of fluorosis or Dean's index, children examined in the 4X OPF community had the highest prevalence of dental fluorosis. While the severity of fluorosis seen in the OPF and NF communities was mild in appearance, the results indicate that fluorosis does occur in optimally and negligibly fluoridated communities. Compared to the NF community, DMFT and DMFS scores in the OPF community were 9.2 percent and 21.2 percent lower, respectively.

CONCLUSIONS

The ingestion of water containing 1 ppm or less fluoride during the time of tooth development may result in dental fluorosis, albeit in its milder forms. However, in these times of numerous products containing fluoride being available, children ingesting water containing 1 ppm fluoride continue to derive caries protection compared to children ingesting water with negligible amounts of fluoride. Thus, the potential for developing a relatively minor unesthetic condition must be weighed against the potential for reducing dental disease.