Effects of chronic heart failure on skeletal muscle capillary hemodynamics at rest and during contractions.

Chronic heart failure (CHF) reduces muscle blood flow at rest and during exercise and impairs muscle function. Using intravital microscopy techniques, we tested the hypothesis that the speed and amplitude of the capillary red blood cell (RBC) velocity (VRBC) and flux (FRBC) response to contractions would be reduced in CHF compared with control (C) spinotrapezius muscle. The proportion of capillaries supporting continuous RBC flow was less (P < 0.05) in CHF (0.66 +/- 0.04) compared with C (0.84 +/- 0.01) muscle at rest and was not significantly altered with contractions. At rest, VRBC (C, 270 +/- 62; CHF, 179 +/- 14 microm/s) and FRBC (C, 22.4 +/- 5.5 vs. CHF, 15.2 +/- 1.2 RBCs/s) were reduced (both P < 0.05) in CHF vs. C muscle. Contractions significantly (both P < 0.05) elevated VRBC (C, 428 +/- 47 vs. CHF, 222 +/- 15 microm/s) and FRBC (C, 44.3 +/- 5.5 vs. CHF, 24.0 +/- 1.2 RBCs/s) in C and CHF muscle; however, both remained significantly lower in CHF than C. The time to 50% of the final response was slowed (both P < 0.05) in CHF compared with C for both VRBC (C, 8 +/- 4; CHF, 56 +/- 11 s) and FRBC (C, 11 +/- 3; CHF, 65 +/- 11 s). Capillary hematocrit increased with contractions in C and CHF muscle but was not different (P > 0.05) between CHF and C. Thus CHF impairs diffusive and conductive O2 delivery across the rest-to-contractions transition in rat skeletal muscle, which may help explain the slowed O2 uptake on-kinetics manifested in CHF patients at exercise onset.     

Effects of surfactant depletion on regional pulmonary metabolic activity during mechanical ventilation

Inflammation during mechanical ventilation is thought to depend on regional mechanical stress. This can be produced by concentration of stresses and cyclic recruitment in low-aeration dependent lung. Positron emission tomography (PET) with (18)F-fluorodeoxyglucose ((18)F-FDG) allows for noninvasive assessment of regional metabolic activity, an index of neutrophilic inflammation. We tested the hypothesis that, during mechanical ventilation, surfactant-depleted low-aeration lung regions present increased regional (18)F-FDG uptake suggestive of in vivo increased regional metabolic activity and inflammation. Sheep underwent unilateral saline lung lavage and were ventilated supine for 4 h (positive end-expiratory pressure = 10 cmH(2)O, tidal volume adjusted to plateau pressure = 30 cmH(2)O). We used PET scans of injected (13)N-nitrogen to compute regional perfusion and ventilation and injected (18)F-FDG to calculate (18)F-FDG uptake rate. Regional aeration was quantified with transmission scans. Whole lung (18)F-FDG uptake was approximately two times higher in lavaged than in nonlavaged lungs (2.9 ± 0.6 vs. 1.5 ± 0.3 10(-3)/min; P < 0.05). The increased (18)F-FDG uptake was topographically heterogeneous and highest in dependent low-aeration regions (gas fraction 10-50%, P < 0.001), even after correction for lung density and wet-to-dry lung ratios. (18)F-FDG uptake in low-aeration regions of lavaged lungs was higher than that in low-aeration regions of nonlavaged lungs (P < 0.05). This occurred despite lower perfusion and ventilation to dependent regions in lavaged than nonlavaged lungs (P < 0.001). In contrast, (18)F-FDG uptake in normally aerated regions was low and similar between lungs. Surfactant depletion produces increased and heterogeneously distributed pulmonary (18)F-FDG uptake after 4 h of supine mechanical ventilation. Metabolic activity is highest in poorly aerated dependent regions, suggesting local increased inflammation.     

Downhill running: a model of exercise hyperemia in the rat spinotrapezius muscle.

To utilize the rat spinotrapezius muscle as a model to investigate the microcirculatory consequences of exercise training, it is necessary to design an exercise protocol that recruits this muscle. There is evidence that the spinotrapezius is derecruited during standard treadmill exercise protocols performed on the uphill treadmill (i.e., 6 degrees incline). This investigation tested the hypothesis that downhill running would effectively recruit the spinotrapezius muscle as assessed by the presence of an exercise hyperemia response. We used radioactive 15-microm microspheres to determine blood flows in the spinotrapezius and selected hindlimb muscles of female Sprague-Dawley rats at rest and during downhill (i.e., -14 degrees incline; 331 +/- 5 g body wt, n = 7) and level (i.e., 0 degrees incline; 320 +/- 11 g body wt, n = 5) running at 30 m/min. Both level and downhill exercise increased blood flow to all hindlimb muscles (P < 0.01). However, in marked contrast to the absence of a hyperemic response to level running, blood flow to the spinotrapezius muscle increased from 26 +/- 6 ml.min(-1).100 g(-1) at rest to 69 +/- 8 ml.min(-1).100 g(-1) during downhill running (P < 0.01). These findings indicate that downhill running represents an exercise paradigm that recruits the spinotrapezius muscle and thereby constitutes a tenable physiological model for investigating the adaptations induced by exercise training (i.e., the mechanisms of altered microcirculatory control by transmission light microscopy).     

Reappraisal of the diagnostic and prognostic value of morning stiffness in arthralgia and early arthritis: results from the Groningen EARC,Leiden EARC,ESPOIR, Leiden EAC and REACH

IntroductionMorning stiffness is assessed daily in the diagnostic process of arthralgia and arthritis, but large-scale studies on the discriminative ability are absent. This study explored the diagnostic value of morning stiffness in 5,202 arthralgia and arthritis patients and the prognostic value in early rheumatoid arthritis (RA).MethodsIn arthralgia patients referred to the Early Arthritis Recognition Clinics (EARC) of Leiden (n = 807) and Groningen (n = 481) or included in the Rotterdam Early Arthritis Cohort (REACH) study (n = 353), the associations (cross-sectional analyses) between morning stiffness and presence of arthritis at physical examination were studied. In early arthritis patients, included in the Leiden Early Arthritis Clinic (EAC) (n = 2,748) and Evaluation et Suivi de POlyarthrites Indifférenciées Récentes (ESPOIR) (n = 813), associations with fulfilling the 2010-RA criteria after one year were assessed. In 2010-RA patients included in the EAC (n = 1,140) and ESPOIR (n = 677), association with the long-term outcomes of disease-modifying antirheumatic drug (DMARD)-free sustained remission and radiological progression were determined. Morning stiffness was defined as a duration ≥60 minutes; sensitivity analyses were performed for other definitions.ResultsIn arthralgia, morning stiffness (≥60 minutes) associated with the presence of arthritis; Leiden EARC odds ratio (OR) 1.49 (95% CI 1.001 to 2.20), Groningen EARC OR 2.21 (1.33 to 3.69) and REACH OR 1.55 (0.97 to 2.47) but the areas under the receiver operating characteristic curve (AUCs) were low (0.52, 0.57, 0.54). In early arthritis, morning stiffness was associated with 2010-RA independent of other predictors (Leiden EAC OR 1.72 (95% CI 1.31 to 2.25, AUC 0.68), ESPOIR OR 1.68 (1.03 to 2.74, AUC 0.64)). Duration of ≥30 minutes provided optimal discrimination for RA in early arthritis. Morning stiffness was not associated with radiological progression or DMARD-free sustained remission.ConclusionsMorning stiffness in arthralgia and early arthritis is associated with arthritis and RA respectively. This supports the incorporation of morning stiffness in the diagnostic process.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0616-3) contains supplementary material, which is available to authorized users.     

Re‐targeting of a plant defense protease by a cyst nematode effector

Plants mount defense responses during pathogen attacks, and robust host defense suppression by pathogen effector proteins is essential for infection success. 4E02 is an effector of the sugar beet cyst nematode Heterodera schachtii. Arabidopsis thaliana lines expressing the effector‐coding sequence showed altered expression levels of defense response genes, as well as higher susceptibility to both the biotroph H. schachtii and the necrotroph Botrytis cinerea, indicating a potential suppression of defenses by 4E02. Yeast two‐hybrid analyses showed that 4E02 targets A. thaliana vacuolar papain‐like cysteine protease (PLCP) ‘Responsive to Dehydration 21A’ (RD21A), which has been shown to function in the plant defense response. Activity‐based protein profiling analyses documented that the in planta presence of 4E02 does not impede enzymatic activity of RD21A. Instead, 4E02 mediates a re‐localization of this protease from the vacuole to the nucleus and cytoplasm, which is likely to prevent the protease from performing its defense function and at the same time, brings it in contact with novel substrates. Yeast two‐hybrid analyses showed that RD21A interacts with multiple host proteins including enzymes involved in defense responses as well as carbohydrate metabolism. In support of a role in carbohydrate metabolism of RD21A after its effector‐mediated re‐localization, we observed cell wall compositional changes in 4E02 expressing A. thaliana lines. Collectively, our study shows that 4E02 removes RD21A from its defense‐inducing pathway and repurposes this enzyme by targeting the active protease to different cell compartments.     

The Bacillus subtilis quorum-sensing molecule CSF contributes to intestinal homeostasis via OCTN2, a host cell membrane transporter

Bacteria use quorum-sensing molecules (QSMs) to communicate within as well as across species. However, the effects of QSMs on eukaryotic host cells have received limited attention. We report that the quorum-sensing pentapeptide, competence and sporulation factor (CSF), of the Gram-positive bacterium Bacillus subtilis activates key survival pathways, including p38 MAP kinase and protein kinase B (Akt), in intestinal epithelial cells. CSF also induces cytoprotective heat shock proteins (Hsps), which prevent oxidant-induced intestinal epithelial cell injury and loss of barrier function. These effects of CSF depend on its uptake by an apical membrane organic cation transporter-2 (OCTN2). Thus, OCTN2-mediated CSF transport serves as an example of a host-bacterial interaction that allows the host to monitor and respond to changes in the behavior or composition of colonic flora.     

Estimation of Noise-Free Variance to Measure Heterogeneity

Variance is a statistical parameter used to characterize heterogeneity or variability in data sets. However, measurements commonly include noise, as random errors superimposed to the actual value, which may substantially increase the variance compared to a noise-free data set. Our aim was to develop and validate a method to estimate noise-free spatial heterogeneity of pulmonary perfusion using dynamic positron emission tomography (PET) scans. On theoretical grounds, we demonstrate a linear relationship between the total variance of a data set derived from averages of n multiple measurements, and the reciprocal of n. Using multiple measurements with varying n yields estimates of the linear relationship including the noise-free variance as the constant parameter. In PET images, n is proportional to the number of registered decay events, and the variance of the image is typically normalized by the square of its mean value yielding a coefficient of variation squared (CV ²). The method was evaluated with a Jaszczak phantom as reference spatial heterogeneity (CV_r ²) for comparison with our estimate of noise-free or ‘true’ heterogeneity (CV _t ²). We found that CV _t ² was only 5.4% higher than CV _r ². Additional evaluations were conducted on 38 PET scans of pulmonary perfusion using ¹³NN-saline injection. The mean CV _t ² was 0.10 (range: 0.03–0.30), while the mean CV ² including noise was 0.24 (range: 0.10–0.59). CV _t ² was in average 41.5% of the CV ² measured including noise (range: 17.8–71.2%). The reproducibility of CV _t ² was evaluated using three repeated PET scans from five subjects. Individual CV _t ² were within 16% of each subject''s mean and paired t-tests revealed no difference among the results from the three consecutive PET scans. In conclusion, our method provides reliable noise-free estimates of CV _t ² in PET scans, and may be useful for similar statistical problems in experimental data.     

Arterial blood gases and acid-base status of dogs during graded dynamic exercise

The objective of this study was to determine whether arterial PCO2 (PaCO2) decreases or remains unchanged from resting levels during mild to moderate steady-state exercise in the dog. To accomplish this, O2 consumption (VO2) arterial blood gases and acid-base status, arterial lactate concentration ([LA-]a), and rectal temperature (Tr) were measured in 27 chronically instrumented dogs at rest, during different levels of submaximal exercise, and during maximal exercise on a motor-driven treadmill. During mild exercise [35% of maximal O2 consumption (VO2 max)], PaCO2 decreased 5.3 +/- 0.4 Torr and resulted in a respiratory alkalosis (delta pHa = +0.029 +/- 0.005). Arterial PO2 (PaO2) increased 5.9 +/- 1.5 Torr and Tr increased 0.5 +/- 0.1 degree C. As the exercise levels progressed from mild to moderate exercise (64% of VO2 max) the magnitude of the hypocapnia and the resultant respiratory alkalosis remained unchanged as PaCO2 remained 5.9 +/- 0.7 Torr below and delta pHa remained 0.029 +/- 0.008 above resting values. When the exercise work rate was increased to elicit VO2 max (96 +/- 2 ml X kg-1 X min-1) the amount of hypocapnia again remained unchanged from submaximal exercise levels and PaCO2 remained 6.0 +/- 0.6 Torr below resting values; however, this response occurred despite continued increases in Tr (delta Tr = 1.7 +/- 0.1 degree C), significant increases in [LA-]a (delta [LA-]a = 2.5 +/- 0.4), and a resultant metabolic acidosis (delta pHa = -0.031 +/- 0.011). The dog, like other nonhuman vertebrates, responded to mild and moderate steady-state exercise with a significant hyperventilation and respiratory alkalosis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of training/detraining on submaximal exercise responses in humans

Human subjects participated in a training/detraining paradigm which consisted of 7 wk of intense endurance training followed by 3 wk of inactivity. In previously sedentary subjects, training produced a 23.9 +/- 7.2% increase in maximal aerobic power (V02max) (group S). Detraining did not affect group S V02max. In previously trained subjects (group T), the training/detraining paradigm did not affect V02max. In group S, training produced an increase in vastus lateralis muscle citrate synthase (CS) activities (nmol.mg protein-1. min-1) from 67.1 +/- 14.5 to 106.9 +/- 22.0. Detraining produced a decrease in CS activity to 80 +/- 14.6. In group T, pretraining CS activity (139.5 +/- 14.9) did not change in response to training. Detraining, however, produced a decrease in CS activity (121.5 +/- 7.8 to 66.8 +/- 5.9). Group S respiratory exchange ratios obtained during submaximal exercise at 60% V02max (R60) decreased in response to training (1.00 +/- 0.02 to 0.87 +/- 0.02) and increased (0.96 +/- 0.02) after detraining. Group T R60 (0.91 +/- 0.01) was not affected by training but increased (0.89 +/- 0.02 to 0.95 +/- 0.02) after detraining. R60 was correlated to changes in CS activity but was unrelated to changes in V02max. These data support the hypothesis that the mitochondrial content of working skeletal muscle is an important determinant of substrate utilization during submaximal exercise.