Analysis of nanoscale fluid inclusions in geomaterials by atom probe tomography: Experiments and numerical simulations.

The spatial correlation between defects in crystalline materials and trace element segregation plays a fundamental role in determining the physical and mechanical properties of a material, which is particularly important in naturally deformed materials. Herein, we combine electron backscatter diffraction, electron channelling contrast imaging, scanning transmission electron microscopy and atom probe tomography on a naturally occurring metal sulphide in an attempt to document mechanisms of element segregation in a brittle-dominated deformation regime. Within APT reconstructions, features with a high point density comprising O-rich discs stacked over As-rich spherules are observed. The combined microscopy data allow us to interpret these as nanoscale fluid inclusions. Our observations are confirmed by simulated APT experiments of core-shell particles with a core exhibiting a very low evaporation field and the shell emulating a segregated layer at the inclusion interface. Our data has significant trans-disciplinary implications to the geosciences, the material sciences, and analytical microscopy.

Goats singly heterozygous for PRNP S146 or K222 orally inoculated with classical scrapie at birth show no disease at ages well beyond 6 years.

Scrapie is a transmissible spongiform encephalopathy of sheep and goats, and scrapie eradication programs in many parts of the world rely on strong genetic resistance to classical scrapie in sheep. However, the utility of putative resistance alleles in goats has been a focus of research because goats can transmit scrapie to sheep and may serve as a scrapie reservoir. Prior work showed that disease-free survival time was significantly extended in orally inoculated goats singly heterozygous for prion amino acid substitutions S146 or K222, but average durations were only around 3 years post-inoculation. The aim of this study was to investigate whether extended survival would exceed 6 years, which represents the productive lifetimes of most commercial goats. While all control homozygotes were clinically affected by an average of <2 years, none of the NS146 or QK222 goats developed clinical scrapie or had PrPSc-positive rectal biopsies. Several NS146 and QK222 goats developed other conditions unrelated to scrapie, but tissue accumulation of PrPSc was not detected in any of these animals. The NS146 heterozygotes have remained disease-free for an average of 2734days (approximately 7.5 years), the longest duration of any classical scrapie challenge experiment with any genotype to date. The QK222 heterozygotes have remained disease-free for an average of 2450days (approximately 6.7 years), the longest reported average duration for QK222 goats challenged with classical scrapie. This research is ongoing, but the current results demonstrate S146 and K222 confer strong resistance to classical scrapie in goats.

Multiplexed, Tethered Particle Microscopy for Studies of DNA-Enzyme Dynamics.

DNA is the carrier of genetic information and, as such, is at the center of most essential cellular processes. To regulate its physiological function, specific proteins and motor enzymes constantly change conformational states with well-controlled dynamics. Twenty-five years ago, Schafer, Gelles, Sheetz, and Landick employed the tethered particle motion (TPM) technique for the first time to study transcription by RNA polymerase at the single-molecule level. TPM has since then remained one of the simplest, most affordable, and yet incisive single-molecule techniques available. It is an in vitro technique which allows investigation of DNA-protein interactions that change the effective length of a DNA tether. In this chapter, we will describe a recent strategy to multiplex TPM which substantially increases the throughput of TPM experiments, as well as a simulation to estimate the time resolution of experiments, such as transcriptional elongation assays, in which lengthy time averaging of the signal is impossible due to continual change of the DNA tether length. These improvements allow efficient study of several DNA-protein systems, including transcriptionally active DNA-RNA polymerase I complexes and DNA-gyrase complexes.

Locally limited inhibition of bone resorption and orthodontic relapse by recombinant osteoprotegerin protein.

OBJECTIVES: To determine minimal dose levels required for local inhibition of orthodontic relapse by recombinant OPG protein (OPG-Fc), while also determining effects of injected OPG-Fc on alveolar bone and long bone. SETTING AND SAMPLE POPULATION: The Department of Orthodontics and Pediatric Dentistry at the University of Michigan. Eighteen male Sprague Dawley rats. MATERIALS & METHODS: Maxillary molars were moved with nickel-titanium springs and then allowed to relapse in Sprague Dawley rats. Upon appliance removal, animals were injected with a single dose of 1.0 mg/kg OPG-Fc, 0.1 mg/kg OPG-Fc, or phosphate-buffered saline (vehicle) just distal to the molar teeth. Tooth movement measurements were made from stone casts, which were scanned and digitally measured. Alveolar tissues were examined by histology. Micro-computed tomography was used to quantify changes in alveolar and femur bone. RESULTS: Local injection of OPG-Fc inhibited molar but not incisor relapse, when compared to vehicle-injected animals. No significant differences in alveolar or femur bone were seen between the three treatment groups after 24 days of relapse. CONCLUSIONS: Our results demonstrate that a single local injection of OPG-Fc effectively inhibits orthodontic relapse, with minimal systemic bone metabolic effects. Our results also show that a single injection of OPG-Fc will influence tooth movement only in teeth close to the injection site. These findings indicate that OPG-Fc has potential as a safe and effective pharmacological means to locally control osteoclasts, for uses such as maintaining anchorage during orthodontic tooth movement and preventing orthodontic relapse in humans.

Emerging immune therapies in type 1 diabetes and pancreatic islet transplantation.

In type 1 diabetes (T1D) the immune system attacks insulin-producing pancreatic ß-cells. Unfortunately, our ability to curb this pathogenic autoimmune response in a disease- and organ-specific manner is still very limited due to the inchoate understanding of the exact nature and the kinetics of the immunological pathomechanisms that lead to T1D. None of the clinical immune interventions thus far, which focused primarily on new-onset disease, were successful in producing lasting remission or curbing recurrent autoimmunity. However, these studies do provide us access to a tremendous amount of clinical data and specimens, which will aid us in revising our therapeutical approaches and defining the highly needed paradigm shift in T1D immunotherapy. Analysing the foundation and the results of the most current T1D immunotherapeutic trials, this article gives an outlook for future directions of the field.

Disease-associated prion protein in neural and lymphoid tissues of mink (Mustela vison) inoculated with transmissible mink encephalopathy.

Transmissible spongiform encephalopathies (TSEs) are diagnosed by immunodetection of disease-associated prion protein (PrP(d)). The distribution of PrP(d) within the body varies with the time-course of infection and between species, during interspecies transmission, as well as with prion strain. Mink are susceptible to a form of TSE known as transmissible mink encephalopathy (TME), presumed to arise due to consumption of feed contaminated with a single prion strain of ruminant origin. After extended passage of TME isolates in hamsters, two strains emerge, HY and DY, each of which is associated with unique structural isoforms of PrP(TME) and of which only the HY strain is associated with accumulation of PrP(TME) in lymphoid tissues. Information on the structural nature and lymphoid accumulation of PrP(TME) in mink is limited. In this study, 13 mink were challenged by intracerebral inoculation using late passage TME inoculum, after which brain and lymphoid tissues were collected at preclinical and clinical time points. The distribution and molecular nature of PrP(TME) was investigated by techniques including blotting of paraffin wax-embedded tissue and epitope mapping by western blotting. PrP(TME) was detected readily in the brain and retropharyngeal lymph node during preclinical infection, with delayed progression of accumulation within other lymphoid tissues. For comparison, three mink were inoculated by the oral route and examined during clinical disease. Accumulation of PrP(TME) in these mink was greater and more widespread, including follicles of rectoanal mucosa-associated lymphoid tissue. Western blot analyses revealed that PrP(TME) accumulating in the brain of mink is structurally most similar to that accumulating in the brain of hamsters infected with the DY strain. Collectively, the results of extended passage in mink are consistent with the presence of only a single strain of TME, the DY strain, capable of inducing accumulation of PrP(TME) in the lymphoid tissues of mink but not in hamsters. Thus, mink are a relevant animal model for further study of this unique strain, which ultimately may have been introduced through consumption of a TSE of ruminant origin.

Dynamics of bovine spleen cell populations during the acute response to Babesia bovis infection: an immunohistological study.

The spleen is a critical organ in defence against haemoparasitic diseases like babesiosis. Many in vitro and ex vivo studies have identified splenic cells working in concert to activate mechanisms required for successful resolution of infection. The techniques used in those studies, however, remove cells from the anatomical context in which cell interaction and trafficking take place. In this study, an immunohistological approach was used to monitor the splenic distribution of defined cells during the acute response of naïve calves to Babesia bovis infection. Splenomegaly was characterized by disproportionate hyperplasia of large versus small leucocytes and altered distribution of several cell types thought to be important in mounting an effective immune response. In particular, the results suggest that the initial crosstalk between NK cells and immature dendritic cells occurs within the marginal zone and that immature dendritic cells are first redirected to encounter pathogens as they enter the spleen and then mature as they process antigen and migrate to T-cell-rich areas. The results of this study are remarkably similar to those observed in a mouse model of malarial infection, suggesting these dynamic events may be central to the acute response of naïve animals to haemoparasitic infection.

The bovine spleen: interactions among splenic cell populations in the innate immunologic control of hemoparasitic infections.

Over the past several years, innate immunity has been recognized as having an important role as a front-line defense mechanism and as an integral part of the adaptive immune response. Innate immunity in cattle exposed to hemoparasites is spleen-dependent and age-related. In this review, we discuss general aspects of innate immunity and the cells involved in this aspect of the response to infection. We also provide examples of specific splenic regulatory and effector mechanisms involved in the response to Babesia bovis, an important tick-borne hemoparasitic disease of cattle. Evidence for the regulatory and effector role of bovine splenic monocytes and DC both in directing a type-1 response through interaction with splenic NK cells and γδT-cells will be presented.

Ovine progressive pneumonia virus capsid antigen as found in CD163- and CD172a-positive alveolar macrophages of persistently infected sheep.

In situ detection of ovine progressive pneumonia virus (OPPV) and the phenotypic identification of the cells that harbor OPPV have not been described for the OPPV-affected tissues, which include lung, mammary gland, synovial membranes of the carpal joint, and choroid plexus of the brain. In this study, the authors first developed a single enzyme-based automated immunohistochemical (IHC) analysis for detection of OPPV capsid antigen (CA) on OPPV-affected tissues, using 2 anti-CAEV CA monoclonal antibodies, 5A1 and 10A1, and 2 enzyme-based IHC systems. Out of 10 naturally and persistently OPPV-infected ewes, OPPV CA was detected in intercellular regions of the carpal synovial membrane of 1 ewe, in cells resembling alveolar macrophages and pulmonary interstitial macrophages in lung tissue of 3 ewes, and in mammary alveolar cells of 1 ewe. Furthermore, dual enzyme-based automated IHC analyses revealed that OPPV CA was predominantly detected in CD172a- or CD163-positive alveolar macrophages of the lungs and mammary gland. That anti-inflammatory (CD163) and downregulatory (CD172a) types of alveolar macrophage harbor OPPV CA leads to the possibility that during persistent infection with OPPV, the host alveolar macrophage might serve to limit inflammation while OPPV persists undetected by the host adaptive immune response in the lung and mammary gland.

Delayed onset muscle soreness does not alter O2 uptake kinetics during heavy-intensity cycling in humans.

The purpose of this study was to determine if exercise-induced delayed onset muscle soreness (DOMS) would alter O2 uptake kinetics during heavy cycling in 9 untrained females. O2 uptake kinetics were characterised during 8-min of constant-load cycling performed with and without DOMS. DOMS was caused by completing 30 min of bench-stepping at a rate of 15 steps.min(-1). Two days after bench stepping, all subjects reported significant leg muscle soreness. Both phase II kinetics (without DOMS tau1: 26.6 +/- 2.4 s; with DOMS tau1: 27.2 +/- 3.7 s) and the slow component amplitude (without DOMS: 277 +/- 15 mL.min(-1); with DOMS: 291 +/- 21 mL.min(-1)) were unaffected by DOMS. The change in blood lactate concentration from rest to end-exercise was significantly greater during exercise performed with DOMS. Eccentric exercise causing a moderate degree of DOMS does not appear to impact upon the mechanisms mediating phase II or the slow component of O2 uptake kinetics.

Verbal numerical scales are as reliable and sensitive as visual analog scales for rating dyspnea in young and older subjects.

This study compared the use of a simple verbal 0-10 numerical rating scale (verbal NRS) and a visual analog scale (VAS) for the rating of dyspnea during exercise in a group of young and older subjects. Twelve younger (32+/-9 yr) and 12 older (71+/-7 yr) subjects used either the verbal NRS or the VAS in a randomised fashion to rate dyspnea during 60 s of uphill treadmill walking (range 5.6-8.8 km h(-1)) performed at either a low (17% grade) or high workload (26% grade) and then during recovery. Rating scales were evaluated twice on separate days (day 1 and day 2) at each workload. While the verbal NRS scores proved to be reliable throughout exercise and recovery, VAS scores were significantly (p<0.05) lower on day 2 during the low workload test (younger group) and the high workload test (older group). Verbal NRS ratings were consistently greater than VAS ratings at both workloads (p<0.001) for both young and older groups. The intra-class correlation coefficients for rating peak dyspnea using either the VAS or verbal NRS were consistently lower for the older subjects (range: r=0.54-0.67) than the younger subjects (range: r=0.70-0.86). Overall, subjects preferred the verbal NRS to the VAS. These results suggest that the verbal NRS compares favourably with the VAS for rating dyspnea during exercise without mask or mouthpiece. However, when rating peak dyspnea both scales appear less reliable when used by the older compared to young subjects.

RNA polymerase II elongation factors Spt4p and Spt5p play roles in transcription elongation by RNA polymerase I and rRNA processing.

Previous investigations into the mechanisms that control RNA Polymerase (Pol) I transcription have primarily focused on the process of transcription initiation, thus little is known regarding postinitiation steps in the transcription cycle. Spt4p and Spt5p are conserved throughout eukaryotes, and they affect elongation by Pol II. We have found that these two proteins copurify with Pol I and associate with the rDNA in vivo. Disruption of the gene for Spt4p resulted in a modest decrease in growth and rRNA synthesis rates at the permissive temperature, 30 degrees C. Furthermore, biochemical and EM analyses showed clear defects in rRNA processing. These data suggest that Spt4p, Spt5p, and, potentially, other regulators of Pol I transcription elongation play important roles in coupling rRNA transcription to its processing and ribosome assembly.

Ventilatory and gas-exchange responses to incremental exercise performed with reduced muscle glycogen content.

This study examined the relationship between minute ventilation (VE), CO2 production (VCO2), and blood lactate concentration ([La-]) during incremental exercise performed with reduced muscle glycogen stores. Nine untrained female subjects (25.3+/-4.2 year) performed incremental cycling in a normal glycogen (NG) state and under conditions of reduced muscle glycogen (RG) content. To reduce muscle glycogen stores, subjects cycled to exhaustion (124+/-33 min) at a power output corresponding to their gas-exchange anaerobic threshold. Peak oxygen uptake (VO2peak) was unchanged with glycogen reduction, even though subjects achieved a significantly lower maximal power output in the RG state (p<0.05). Peak blood [La-] decreased significantly by 37% in the RG state (p<0.001). At any percentage of VO2peak, O2 uptake and VE were similar for both treatment conditions, whereas VCO2 and respiratory exchange ratio values were lower during the RG trial than under NG conditions. Therefore, VE/VCO2 tended to be higher and end-tidal CO2 partial pressure tended to be lower during exercise performed in the RG state. VE was significantly correlated with VCO2 under both treatment conditions (NG: r=0.99, p<0.01; RG: r=0.99, p<0.01). However, the slope of the VE-VCO2 relationship was significantly elevated during the RG trial (p<0.01). VE during exercise was similar under both treatment conditions, even though VCO2 and blood [La-] were lower during the RG trial compared to the NG trial. This suggests that factors other than CO2 delivery to the lung and metabolic acidosis play an important role in regulating VE during exercise.

Expression of sodium channel Nav1.6 in cholinergic myenteric neurons of guinea pig proximal colon.

We wished to establish the functional identity of Na(v)1.6-expressing myenteric neurons of the guinea pig proximal colon by determining the extent of colocalization of Na(v)1.6 and selected neurochemical markers. Na(v)1.6-like immunoreactivity (-li) was primarily localized to the hillock and initial segments of myenteric neurons located near junctions with internodal fiber tracts. Immunoreactivity for Na(v)1.6 was co-localized with choline-acetyltransferase-li, representing 96% of Na(v)1.6-immunoreactive neurons; about 5% of these neurons showed co-localization with calretinin-li, but none with substance-P-li. Cholinergic neurons expressing Na(v)1.6 were amongst the smallest (somal area <300 mum(2)) of all cholinergic myenteric neurons observed. Only three of 234 Na(v)1.6-immunoreactive neurons exhibited nNOS-li, and none co-localized with calbindin-li. These data suggest that Na(v)1.6 is expressed in a small uniform population of cholinergic myenteric neurons that lie within the guinea pig proximal colon and that are likely to function as excitatory motor neurons.

Expression of the sodium channel Na(v)1.2 in chemically identified myenteric neurons in the guinea pig.

Our purpose was to identify Na(v)1.2-expressing myenteric neurons of the small and large intestine of the guinea pig by using antibodies directed against Na(v)1.2 and selected neurochemical markers. Na(v)1.2-like immunoreactivity (-li) co-localized with immunoreactivity for choline acetyltransferase in all regions, representing 45%-67% of Na(v)1.2-positive neurons. Na(v)1.2-li co-localized with immunoreactivity for the neural form of nitric oxide synthase more frequently in the colon (20% of neurons exhibiting Na(v)1.2-li) than in the ileum (8%). Co-localization of Na(v)1.2-li with immunoreactivity for a form of neurofilament (NF145) was infrequently observed in the ileum and colon. Enkephalin-immunoreactive cell bodies co-localized with Na(v)1.2-li in all regions. Few myenteric cell bodies immunoreactive for neuropeptide Y were observed in the ileum, but all co-localized with Na(v)1.2-li. This and our previous data suggest that Na(v)1.2 is widely expressed within the guinea pig enteric nervous system, including the three main classes of myenteric neurons (sensory, motor, and interneurons), and is involved in both excitatory and inhibitory pathways. Notable exceptions include the excitatory motor neurons to the longitudinal smooth muscle, the ascending interneurons of the ileum, and the myenteric neurons immunoreactive for NF145, few of which are immunoreactive for Na(v)1.2.

Continuous and intermittent exercise responses in individuals with chronic obstructive pulmonary disease.

BACKGROUND: While the acute physiological responses to continuous exercise have been well documented in individuals with chronic obstructive pulmonary disease (COPD), no previous study has examined the response to intermittent exercise in these patients. METHODS: We examined the physiological responses of 10 individuals with moderate COPD (forced expiratory volume in 1 second 52 (15)% predicted) who performed both an intermittent (1 min exercise and rest intervals) and a continuous cycle ergometer test on separate days. Both intermittent and continuous exercise tests were performed at the same power output, calculated as 70% of the peak power attained during an incremental exercise test. RESULTS: Intermittent exercise was associated with significantly lower values for oxygen uptake, carbon dioxide output, expired ventilation, heart rate, plasma lactate concentration, and ratings of breathlessness than continuous exercise. Subjects were able to complete a significantly greater total amount of work during intermittent exercise (71 (32) kJ) than during continuous exercise (31 (24) kJ). The degree of dynamic lung hyperinflation (change in end expiratory lung volume) was significantly lower during intermittent exercise (0.23 (0.07) l) than in continuous exercise (0.52 (0.13) l). CONCLUSIONS: The greater amount of work performed and lower measured physiological responses achieved with intermittent exercise may allow for greater peripheral training adaptations in individuals with more limited lung function. The results suggest that intermittent exercise may be superior to continuous exercise as a mode of training for patients with COPD.

Effect of ramp slope on ventilation thresholds and VO2peak in male cyclists.

This study investigated the effect of 10 W*min(-1) (Slow ramp, SR), 30 W*min(-1) (Medium ramp, MR) and 50 W*min(-1) (Fast ramp, FR) exercise protocols on assessments of the first (VT1) and second (VT2) ventilation thresholds and peak oxygen uptake (VO(2)peak) in 12 highly-trained male cyclists (mean +/- SD age = 26 +/- 6 yr). Expired gas sampled from a mixing chamber was analyzed on-line and VT1 and VT2 were defined as two break-points in 20-s-average plots of pulmonary ventilation (V(E)), ventilatory equivalents for O(2) (V(E)/VO(2)) and CO(2) (V(E)/VCO(2)), and fractions of expired O(2) (F(E)O(2)) and CO(2) (F(E)CO(2)). Arterialized-venous blood samples were analyzed for blood-gas and acid-base status. VO(2)peak was significantly lower (p < 0.05) for SR (4.65 +/- 0.53 l small middle dot min(-1)) compared to MR (4.89 +/- 0.56 l *min(-1)) and FR (4.88 +/- 0.57 l *min(-1)) protocols. CO(2) output and blood PCO(2) were lower (p < 0.05), and V(E)/VCO(2) was higher (p < 0.05), above VT1 for SR compared to MR and FR protocols. No significant differences were observed among the protocols for VO(2), % VO(2)peak, V(E), plasma lactate ([La(-)]) and blood hydrogen ion concentration ([H(+)]), and heart rate (HR) values at VT1 or VT2. The work rate (WR) measured at VT1, VT2 and VO(2)peak increased (p < 0.05) with steeper ramp slopes. It was concluded that, in highly-trained cyclists, assessments of VT1 and VT2 are independent of ramp rate (10, 30, 50 W*min(-1)) when expressed as VO(2), % VO(2)peak, V(E), plasma [La(-)], blood [H(+)] and HR values, whereas VO(2)peak is lower during 10 W*min(-1) compared to 30 and 50 W*min(-1) ramp protocols. In addition, the WR measured at VT1, VT2 and VO(2)peak varies with the ramp slope and should be utilized cautiously when prescribing training or evaluating performance.

Reliability of MAOD measured at 110% and 120% of peak oxygen uptake for cycling.

PURPOSE: The purpose of this study was to examine the test-retest reliability of maximal accumulated oxygen deficit (MAOD) measured at 110% and 120% of peak oxygen uptake (VO2) for cycling in seven untrained male and seven untrained female subjects. METHODS: After one familiarization trial, all subjects performed two MAOD tests at a power output corresponding to 110% and two tests at 120% of VO2peak in random order. MAOD was calculated for each subject as the difference between O2 demand during exercise and the measured VO2. RESULTS: The mean (+/-SEM) time to exhaustion for the group was not significantly different between trial 1 (226 +/- 13 s) and trial 2 (223 +/- 14 s) of the 110% test. Likewise, the difference in the time to exhaustion between trial 1 (158 +/- 11 s) and trial 2 (159 +/- 10 s) was not significant for the 120% test. The intraclass correlation coefficients for the time to exhaustion were 0.95 for the 110% test and 0.98 for the 120% test. The mean MAOD value obtained in trial 1 (2.62 +/- 0.17 L) was not significantly different from the mean value obtained in trial 2 (2.54 +/- 0.19 L) for the 110% test. Additionally, the mean values for the two trials did not differ significantly for MAOD (2.64 +/- 0.21 L for trial 1 and 2.63 +/- 0.19 L for trial 2) in the 120% test. The intraclass correlation coefficients for MAOD were 0.95 for the 110% test and 0.97 for the 120% test. All intraclass correlation coefficients were significant at P < 0.001. CONCLUSIONS: When conducted under standardized conditions, the determination of MAOD for cycling was highly repeatable at both 110% and 120% of VO2peak in untrained male and female subjects.

Tracheobronchial mucus viscoelasticity during environmental challenge in horses with recurrent airway obstruction.

The goal of this study was to compare the rheological properties of mucus from horses with recurrent airway obstruction (RAO) to that from healthy controls during environmental challenge by stabling in stalls with straw as bedding and hay as feed. We determined viscoelasticity (log G* dyn/cm2, at 10 radian/s) and calculated mucociliary clearability index (MCI) and cough clearability index (CCI), which are derivative parameters of G* and the ratio of viscosity and elasticity measured at 1 and 100 radian/s, respectively. We also investigated the solids content of mucus, and cytology of bronchoalveolar lavage fluid (BALF). Samples were obtained before (0 h) and 6, 24 and 48 h after environmental challenge. The central findings were rheological changes in airway mucus, which occurred over time in RAO-affected animals, but not in controls. Mucus rheology was similar in both groups at 0 and 6 h. In RAO-affected horses, mucus viscoelasticity, as measured by log G*, increased from 2.49 +/- 0.18 dyn/cm2 (mean +/- s.e.) at 0 h to 3.05 +/- 0.13 dyn/cm2 at 24 h after environmental challenge, and was accompanied by significant decreases in MCI and CCI. Percent solids of mucus did not differ significantly between the 2 groups, nor over time. Rheological values did not correlate with BALF cytology. We conclude that viscoelastic properties of tracheal mucus samples from RAO horses in remission do not differ from those of normal horses. However, environmental challenge causes clinical signs of small airway disease and a concurrent increase in mucus viscoelasticity only in RAO horses. Therefore, we infer that unfavourable changes in mucus rheology may contribute to stasis and accumulation of mucus in RAO horses in exacerbation, but not in clinical remission.