Tree architecture, light interception and water-use related traits are controlled by different genomic regions in an apple tree core collection

Tree architecture shows large genotypic variability, but how this affects water-deficit responses is poorly understood. To assess the possibility of reaching ideotypes with adequate combinations of architectural and functional traits in the face of climate change, we combined high-throughput field phenotyping and genome-wide association studies (GWAS) on an apple tree (Malus domestica) core-collection. We used terrestrial light detection and ranging (T-LiDAR) scanning and airborne multispectral and thermal imagery to monitor tree architecture, canopy shape, light interception, vegetation indices and transpiration on 241 apple cultivars submitted to progressive field soil drying. GWAS was performed with single nucleotide polymorphism (SNP)-by-SNP and multi-SNP methods. Large phenotypic and genetic variability was observed for all traits examined within the collection, especially canopy surface temperature in both well-watered and water deficit conditions, suggesting control of water loss was largely genotype-dependent. Robust genomic associations revealed independent genetic control for the architectural and functional traits. Screening associated genomic regions revealed candidate genes involved in relevant pathways for each trait. We show that multiple allelic combinations exist for all studied traits within this collection. This opens promising avenues to jointly optimize tree architecture, light interception and water use in breeding strategies. Genotypes carrying favourable alleles depending on environmental scenarios and production objectives could thus be targeted.

Alterations in Body Fluid Balance During Fin Swimming in 29 °C Water in a Population of Special Forces Divers

Highly trained "combat swimmers" encounter physiological difficulties when performing missions in warm water. The aim of this study was to assess the respective roles of immersion and physical activity in perturbing fluid balance of military divers on duty in warm water. 12 trained divers performed 2 dives each (2 h, 3 m depth) in fresh water at 29 °C. Divers either remained Static or swam continuously (Fin) during the dive. In the Fin condition, oxygen consumption and heart rate were 2-fold greater than during the Static dive. Core and skin temperatures were also higher (Fin: 38.5±0.4 °C and 36.2±0.3 °C and Static: 37.2±0.3 °C and 34.3±0.3 °C; respectively p=0.0002 and p=0.0003). During the Fin dive, the average mass loss was 989 g (39% urine loss, 41% sweating and 20% insensible water loss and blood sampling); Static divers lost 720 g (84% urine loss, 2% sweating and 14% insensible water loss and blood sampling) (p=0.003). In the Fin condition, a greater decrease in total body mass and greater sweating occurred, without effects on circulating renin and aldosterone concentrations; diuresis was reduced, and plasma volume decreased more than in the Static condition.

Typology of "Fatigue" by Heart Rate Variability Analysis in Elite Nordic-skiers

This study investigated changes in heart rate variability (HRV) in elite Nordic-skiers to characterize different types of "fatigue" in 27 men and 30 women surveyed from 2004 to 2008. R-R intervals were recorded at rest during 8 min supine (SU) followed by 7 min standing (ST). HRV parameters analysed were powers of low (LF), high (HF) frequencies, (LF+HF) (ms(2)) and heart rate (HR, bpm). In the 1 063 HRV tests performed, 172 corresponded to a "fatigue" state and the first were considered for analysis. 4 types of "fatigue" (F) were identified: 1. F(HF(-)LF(-))SU_ST for 42 tests: decrease in LFSU (- 46%), HFSU (- 70%), LFST (- 43%), HFST (- 53%) and increase in HRSU (+ 15%), HRST (+ 14%). 2. F(LF(+) SULF(-) ST) for 8 tests: increase in LFSU (+ 190%) decrease in LFST (- 84%) and increase in HRST (+ 21%). 3. F(HF(-) SUHF(+) ST) for 6 tests: decrease in HFSU (- 72%) and increase in HFST (+ 501%). 4. F(HF(+) SU) for only 1 test with an increase in HFSU (+ 2161%) and decrease in HRSU (- 15%). Supine and standing HRV patterns were independently modified by "fatigue". 4 "fatigue"-shifted HRV patterns were statistically sorted according to differently paired changes in the 2 postures. This characterization might be useful for further understanding autonomic rearrangements in different "fatigue" conditions.

Changes in femoral artery blood flow during thermoneutral, cold, and contrast-water therapy

AIM

The purpose of this study was to examine the changes in femoral artery blood flow during cold water immersion (CWI), contrast water therapy (CWT) and thermoneutral water immersion (TWI).

METHODS

Ten athletes came to the laboratory three times, to complete a 20-min procedure in upright position: 4 min in air (baseline), then 16-min full leg TWI (~35 °C), CWI (~12 °C) or CWT (2:2 ~12 °C to ~35 °C) min ratio, in a random order. Blood flow was measured every 2 min: baseline (i.e. min 3 and 1) and throughout water immersion (i.e. min 1, 3, 5, 7, 9, 11, 13 and 15), using Doppler ultrasound in the superficial femoral artery, distal to the common bifurcation (~3 cm), above the water and stocking.

RESULTS

Compared with baseline, blood flow was significantly higher throughout TWI (min 1 to 15: P<0.001; +74.6%), significantly lower during CWI (from min 7 to 15: P<0.05; -16.2%) and did not change during CWT (min 1 to 15). No changes in blood flow occurred between the hot and cold transitions of CWT.

CONCLUSION

This study shows that external hydrostatic pressure (TWI ~35 °C) significantly increases femoral artery blood flow. We also show that associating hydrostatic pressure with cooling (CWI ~12 °C) decreases femoral artery blood flow after a sufficient duration, whereas associating hydrostatic pressure with alternating brief exposures to contrasted temperatures does not change femoral artery blood flow under resting conditions.

Effects of three postexercice recovery treatments on femoral artery blood flow kinetics

AIM

This study aimed to compare the kinetics of muscle leg blood flow during three recovery treatments following a prolonged exercise: contrast water therapy (CWT), compression stockings (CS) or passive recovery (PR).

METHODS

Fifteen men came to the laboratory three times to perform a 45-min exercise followed 5 min after by a standardized 12-min recovery treatment in upright position, alternating between two vats every 2 min: CWT (cold: ~12 °C to warm: 36 °C), CS (~20 mmHg) or PR. The order of treatments was randomized. Blood flow was measured using Doppler ultrasound during the recovery treatments (i.e., min 3, 5, 7 and 9) in the superficial femoral artery distally to the common bifurcation (~3 cm) (above the water and stocking).

RESULTS

Blood flow was significantly higher during CWT (P<0.01; +22.91%) and CS (P<0.05; +15.26%) than during PR. Although no statistical difference between CWT and CS was observed, effect sizes were larger during CWT (large) than during CS (moderate). No changes in blood flow occurred in the femoral artery between hot and cold transitions of CWT.

CONCLUSION

During immediate recovery of a high intensity exercise, CWT and CS trigger higher femoral artery blood flow than PR. Moreover, effect sizes were greater during CWT than during CS.

The underestimated compression effect of neoprene wetsuit on divers hydromineral homeostasis

This study aimed at demonstrating that the neoprene wetsuit provides not only thermal protection. Compression it exerts on the diver's shell significantly impacts hydromineral homeostasis by restraining the systemic vascular capacity and secondarily increasing urine output on dry land and during scuba diving. 8 healthy divers underwent five 2-h sessions: sitting out of water in trunks (control situation), sitting out of water wearing a wetsuit, and 3 wetsuit scuba-immersed sessions at 1, 6 and 12 msw depth, respectively. Urine volumes and blood samples were collected. Hemoglobin (Hb), hematocrit (Ht) and plasma sodium concentration were measured. Interface pressure between the garment and the skin was measured at 17 sites of the body shell, with a pressure transducer. Mean interface pressures between wetsuit and skin amounted to: 25.8±2.8 mm Hg. Whatever the depth, elastic recoil tension of wetsuit material was unchanged by immersion. Weight loss was respectively 2 and 3 times greater when wetsuit was worn out of water (430 g) and during immersion (710 g) than when divers did not wear any wetsuit out of water (235 g; p<0.05). Urine volume accounted for 85% of weight loss in either session. Weight loss and urine volume were similar whatever immersion depth. The decrease in plasma volume amounted to 8% of urine volume when divers did not wear any wetsuit out of water, and to 30% when wetsuit was worn out of water or during immersion. Diving wetsuit develops a pressure effect that alters diver's hydromineral homeostasis. During immersion, the wetsuit pressure merges into the larger main effect of hydrostatic pressure to reduce water content of body fluids, unrelated to immersion depth.

[COPD in dairy farmers: screening, characterization and constitution of a cohort. The BALISTIC study]

BACKGROUND

A pilot study from our group suggests that the prevalence of chronic obstructive pulmonary disease (COPD) among dairy farmers is higher than in the general population although dairy workers are less frequently smokers.

OBJECTIVES AND METHODS

The study presented here aims at (i) determining the prevalence of COPD in a large and representative population of dairy farmers; (ii) characterizing these patients in terms of smoking habits, dyspnoea, quality of life, lung function, bronchial exhaled nitric oxide, systemic inflammation, arterial stiffness and exercise capacity; (iii) comparing characteristics of dairy farmers' COPD with the characteristics of COPD in patients without any occupational exposure; (iv) identifying the etiological factors of COPD in dairy farmers; and (v) constituting a cohort of COPD patients and control subjects for further longitudinal studies. Two groups of COPD patients (dairy farmers or not) and two groups of controls subjects will be selected among a representative panel of 2000 dairy workers and 2000 subjects without any occupational exposure, all aged 40 to 75 years.

EXPECTED RESULTS

A better knowledge of the epidemiology and pathophysiology of COPD in dairy farmers should guide a specific strategy of prevention. The knowledge of the characteristics of COPD occurring in dairy farmers will help to define the therapeutic modalities that might be different compared with the therapeutic recommendations for COPD secondary to tobacco smoking.

Evaluation of cardiorespiratory functional reserve from arm exercise in the elderly

BACKGROUND

When the subject is not able to satisfy traditional testing procedures, alternative exercises or indices such as arm cranking or the oxygen uptake efficiency slope (OUES) have been proposed. However, the OUES has not yet been used on elderly subjects from an exercise performed with the arms.

OBJECTIVE

The aim of our study was to evaluate the possibility of using the OUES as an index of the cardiorespiratory functional reserve in the elderly when the exercise evaluation test is performed with the arms and when this parameter is estimated from submaximal responses.

METHODS

Seventeen adults (62-82 years) undergoing total joint arthroplasty of the hip took part in this study. Maximal incremental exercise tests were performed on an arm crank ergometer 1 month before (T₁) and 2 months after (T₂) surgery. Gas exchanges were measured continuously to determine oxygen consumption at peak exercise (V˙O₂ peak) and were used to calculate the OUES. The correlation coefficient was calculated between V˙O₂ peak and OUES, and their relative changes between T₁ and T₂.

RESULTS

V˙O₂ peak was not significantly different between T₁ and T₂: 10.3 ± 0.7 and 9.8 ± 0.5 mL/min per kilogramme respectively. The OUES estimated from submaximal responses did not show a significant difference between T₁ and T₂. Significant correlations were observed between individual V˙O₂ peak and OUES, as well as at T₁ and T₂.

CONCLUSION

The use of arm cranking exercises and the calculation of the OUES from the submaximal respiratory response can be used for the objective quantification of cardiorespiratory functional reserve in the elderly.

Effects of the cold pressor test on cardiac autonomic control in normal subjects

The cold pressor test (CPT) triggers in healthy subjects a vascular sympathetic activation and an increase in blood pressure. The heart rate (HR) response to this test is less well defined, with a high inter-individual variability. We used traditional spectral analysis together with the non-linear detrended fluctuation analysis to study the autonomic control of HR during a 3-min CPT. 39 healthy young subjects (23.7+/-3.2 years, height 180.4+/-4.7 cm and weight 73.3+/-6.4 kg) were divided into two groups according to their HR responses to CPT. Twenty subjects have a sustained increase in HR throughout the test with reciprocal autonomic interaction, i.e. increase in sympathetic activity and decrease vagal outflow. In the 19 remainders, HR decreased after an initial increase, with indication of involvement of both sympathetic and vagal outflow. Baseline evaluation of the subjects revealed no difference between the two groups. Nevertheless, a higher sympathetic activity at the skin level during CPT was present in the group with decreased HR. Further studies are needed to explain why healthy subjects react differently to the CPT and if this has potential clinical implications.

[Physiological assessment of a gaseous cryotherapy device: thermal effects and changes in cardiovascular autonomic control]

PURPOSE

The aim of the study was to assess thermal effects and cardiovascular autonomic control with application of a gaseous cryotherapy device to the hand.

MATERIAL AND METHODS

Before, during and after cooling of the left hand, we continuously evaluated cutaneous temperature of the right and left hands, as well as heart rate (HR) and arterial blood pressure (BP) and their neurovegetatif control (HR and BP variability) in 8 healthy subjects. Comparison of cooling caused by projection of CO(2) microcrystals (2 min) under high pressure (75 bar) and low temperature (-78 degrees C) to that with application of a latex ice pack (15 min). Assessment of whether cooling triggered any changes in cardiovascular autonomic control, especially as compared with responses by the hand cold-pressure test (2 min).

RESULTS

CO(2) projection in the left hand induced a steep decrease (-26 degrees C) in temperature followed by a rapid increase and a cutaneous vasoconstriction of the right hand, with significant increases in BP and cardiac parasympathetic activity. Cardiovascular responses were similar to those with application of the hand cold-pressure test. Application of an ice pack decreased cutaneous temperature to a lesser extent (-19 degrees C) and more slowly, without changing BP or indices of HR and BP variability.

CONCLUSION

CO(2) projection caused "thermal shock" and triggered a systemic cutaneous vasoconstriction response, with activation of indices of both ortho- and parasympathetic activity, as with the hand cold-pressure test. Vascular responses during ice pack cooling appeared solely localised to the cooled area, without any significant change in autonomic cardiovascular control.

Impaired cardiovascular autonomic control in newly and long-term-treated patients with Parkinson's disease: involvement of L-dopa therapy

In idiopathic Parkinson's disease (PD), autonomic dysfunction is frequent, causing orthostatic hypotension. The respective roles of disease progression and dopaminergic treatment remain unclear. In this study, we investigated the autonomic control of cardiovascular functions and its relation to L-dopa therapy in both newly diagnosed (ND) and long-term-treated (LT) patients. Study subjects were: (1) nine ND patients never having undergone treatment with L-dopa; (2) 18 LT patients who had been receiving L-dopa treatment for a long period. ND patients were investigated before L-dopa treatment and after stabilization of their L-dopa dosage. LT patients were investigated once with their regular treatment and once after a 12-h interruption of L-dopa treatment; (3) nine healthy subjects served as controls. At each test session, blood pressure (BP), heart rate (HR), plasma catecholamines, heart rate variability (HRV), and spontaneous baroreflex sensitivity were assessed in the supine and upright positions. Before receiving L-dopa medication, ND patients had reduced E/I ratios (HR response/deep breathing) and lowered HRV when compared to controls; this was evidence of early effects of the disease on autonomic HR control. Introduction of L-dopa treatment reduced BP, HR, and plasma levels of adrenaline and noradrenaline. Similar changes were found in LT patients when contrasting the short-term treatment interruption and the usual L-dopa dosage. The treatment-linked increase in plasma dopamine also correlated with the decrease in noradrenaline. These results showed that mild impairment of autonomic cardiovascular control occurred early in the course of PD. They also provided evidence that the side effects of L-dopa aggravated the impairment of the autonomic control of BP and HR.

Short-term vasomotor adjustments to post immersion dehydration are hindered by natriuretic peptides

Many studies have described the physiology of water immersion (WI), whereas few have focused on post WI physiology, which faces the global water loss of the large WI diuresis. Therefore, we compared hemodynamics and vasomotor tone in 10 trained supine divers before and after two 6h sessions in dry (DY) and head out WI environments. During each exposure (DY and WI) two exercise periods (each one hour 75W ergometer cycling) started after the 3rd and 5th hours. Weight losses were significant (-2.24 +/- 0.13 kg and -2.38 +/- 0.19 kg, after DY and WI, respectively), but not different between the two conditions. Plasma volume was reduced at the end of the two conditions (-9.7 +/- 1.6% and -14.7 +/- 1.6%, respectively; p < 0.05). This post-WI decrease was deeper than post DY (p < 0.05). Cardiac output (CO) and mean arterial blood pressure were maintained after the two exposures. Plasma levels of noradrenaline, antidiuretic hormone and ANP were twofold higher after WI than after DY (p < 0.05). After DY total peripheral resistances (TPR) were increased (p < 0.05) and heart rate (HR) was reduced (p < 0.05). After WI there was a trend for a decrease in stroke volume (p = 0.07) with unchanged TPR and HR, despite more sizeable increases in plasma noradrenaline and vasopressin than after DY. We hypothesized that the higher levels of plasma natriuretic peptides after WI were likely counteracting the dehydration-required vasomotor adjustments.

Validity of microgravity simulation models on earth

Many studies have used water immersion and head-down bed rest as experimental models to simulate responses to microgravity. However, some data collected during space missions are at variance or in contrast with observations collected from experimental models. These discrepancies could reflect incomplete knowledge of the characteristics inherent to each model. During water immersion, the hydrostatic pressure lowers the peripheral vascular capacity and causes increased thoracic blood volume and high vascular perfusion. In turn, these changes lead to high urinary flow, low vasomotor tone, and a high rate of water exchange between interstitium and plasma. In contrast, the increase in thoracic blood volume during a space mission is combined with stimulated orthosympathetic tone and lowered urine flow. During bed rest, body tissues are compressed by pressure from gravity, whereas microgravity causes a negative pressure around the body. The differences in renal function between space and experimental models appear to be explained by the physical forces affecting tissues and hemodynamics as well as by the changes secondary to these forces. These differences may help in selecting experimental models to study possible effects of microgravity.

Revised hypothesis and future perspectives

Results from space have been unexpected and not predictable from the results of ground-based simulations. Therefore, the concept of how weightlessness and gravity modulates the regulation of body fluids must be revised and a new simulation model developed. The main questions to ask in the future are the following: Does weightlessness induce a diuresis and natriuresis during the initial hours of space flight leading to an extracellular and intravascular fluid volume deficit? Can sodium in excess be stored in a hitherto unknown way, particularly during space flight? Why are fluid and sodium retaining systems activated by spaceflight? Why are the renal responses to saline and water stimuli in space attenuated compared with those of ground simulations? How can the effects of weightlessness on fluid and electrolyte regulation be correctly simulated on the ground? The information obtained from space may be of relevance to fluid and electrolyte balance in edematous patients.

Neural-epithelial cell interplay: in vitro evidence that vagal mediators increase PGE2 production by human nasal epithelial cells

During inflammatory states, airway epithelial cells are stimulated by various proinflammatory mediators to synthesize paracrine mediators including prostaglandin E2, which likely contributes to the recurrence of allergic inflammation. We studied the effects of acetylcholine (ACh) and substance P (SP) on PGE2 release because these two neuromediators are widely involved in airway inflammation, e.g., to trigger mucosal vasodilation and plasma exudation. PGE2 release was studied at baseline and after addition of ACh and SP (10(-10) to 10(-7) M) in primary cultures of human nasal epithelial cells from control mucosa, inflammatory non-atopic mucosa, and inflammatory atopic mucosa. The mediators' effects on COX 2 mRNA were assessed by Northern blotting. We also tested the effect of atropine and SR140333, inhibitors of ACh and SP, respectively. The spontaneous release of PGE2 was about three times higher in cells from atopic subjects. ACh and SP markedly increased PGE2 release (by more than 1.5 times) and this effect was similar whether the sampled tissues were inflammatory or not. In cells from atopic subjects this neuromediator effect led to a fivefold increase in PGE2 release, as compared to baseline production by cells from control mucosa. This stimulation of PGE2 release by neural mediators was inhibited by specific antagonists. ACh and SP increased COX 2 mRNA in the three groups. Thus, neuromediators can bolster PGE2 production in the airway, likely reinforcing inflammation. In conclusion, these data provide evidence that the interplay of nerve fibers and airway epithelial cells is likely important in inflammatory conditions as, e.g., allergy and asthma.

An in vitro model for the study of human bone marrow angiogenesis: role of hematopoietic cytokines

This study describes a human bone marrow endothelial cell culture in which endothelial cells are organized into capillary tubes. These endothelial cells were positive for von Willebrand Factor, expressed CD34, CD31, and L-fucose residues, took up acetylated low-density lipoproteins, contained Weibel-Palade bodies, and were ensheathed in a basal lamina (which included laminin beta1, EDa+ and EDb+ fibronectin, and collagen type iv). Pericytes expressing alpha-smooth muscle (alpha-SM) actin were spatially associated with the capillary tubes and there was a highly significant correlation between the number of capillary tubes and pericytes. In this model, basal angiogenesis was found to be vascular endothelial growth factor (VEGF)-dependent, because neutralization of endogenous VEGF induced a dramatic regression in the number of tubes. However, the presence of alpha-SM actin-expressing pericytes in the linings of endothelial tubes partially prevented the VEGF-neutralized tube regression. We also observed that nitric oxide production contributed to basal angiogenesis and that upregulation of nitric oxide increased the number of tubes. Tube numbers also decreased when antibodies neutralizing the integrin alphavbeta5 were applied to the cultures. Moreover, addition of any of the hematopoietic cytokines, erythropoietin, stem cell factor, granulocytic colony stimulating factor, or granulomonocytic colony stimulating factor induced a highly significant increase in tube formation. When erythropoietin and granulocytic colony stimulating factor were added, this increase was larger than the maximum increase observed with VEGF. Thus, we have described an in vitro model for human bone marrow angiogenesis in which pericytes and basal lamina matrix were associated with endothelial cells and formed fully organized capillary tubes. In this model, cytokines known to regulate hematopoiesis also seemed to be mediators of angiogenesis. This culture system may therefore prove to be a valuable tool for the study of hematopoietic cytokines on angiogenesis.

Graded vascular autonomic control versus discontinuous cardiac control during gradual upright tilt

Indexes of heart rate variability (HRV) and the slope of cardiac baroreflex are extensively used for non invasive assessment of circulatory autonomic control in pathophysiology. We performed this study (1) to assess the sensitivity of these indexes towards small graded postural stimulations and (2) to delineate the informations provided about the settings of both vascular tone and cardiac activity. Twenty healthy subjects were randomly tilted for eight minutes at each of the six angles: -10 degrees, 0 degrees (supine), 10 degrees, 30 degrees, 45 degrees, and 60 degrees. Instant RR-interval and finger blood pressure (BP) were continuously recorded, and venous blood was collected at the end of each 8 min position for catecholamines determination. Group average heart rate, noradrenaline and diastolic BP (DBP) increased linearly with head-up tilt angle from 10 degrees. Systolic BP (SBB) ranked only two distinct series -10 degrees, 0 degrees, 10 degrees versus 30 degrees, 45 degrees, 60 degrees, as did the number of spontaneous baroreflex (SBR) sequences. The spectral power of the low-frequency (LF) and high-frequency (HF) of RR variability and the ratio LF/HF changed rather abruptly from either 30 degrees or 45 degrees, depending on each individual. Both HF/tot i.e. the ratio of HF to total spectral RR variability and the slope of SBR decreased markedly from 10 degrees to 30 degrees and less but more gradually from 30 degrees to 60 degrees. Thus, our observations argue for gradual adjustments of vascular tone as reflected by highly consistent changes in plasma noradrenaline and diastolic arterial pressure, contrasting with a main discontinuous autonomic setting of cardiac activity as reflected by changes in the harmonic components of spectral RR variability and in the slope of cardiac baroreflex. The pattern of changes in systolic arterial pressure attested the discontinuous cardiac autonomic control rather than the gradual setting of arterial tone. We submit that these different patterns of autonomic adjustments should be considered when assessing pathophysiological states.

Acute dysautonomia secondary to autoimmune diseases: efficacy of intravenous immunoglobulin and correlation with a stimulation of plasma norepinephrine levels

Acute dysautonomia is a disorder characterized by severe sympathetic and parasympathetic failure with relative preservation of motor and sensory function. The disease is considered to be idiopathic in most cases, but there is now a trend towards considering the disorder as an uncommon variant of Guillain Barré syndrome. We report two cases of acute dysautonomia which did not fulfill the criteria of the idiopathic form. The first case was associated with Sjögren's syndrome and the second with thyroiditis and antiganglioside antibodies which were correlated with the severity of the disease. Intravenous gammaglobulin (IVGG) was effective in both cases, as has been reported for the idiopathic form, and in one case the treatment was associated with an increase in the supine and standing plasma norepinephrine levels, thus substantiating the positive effects of IVGG on the orthostatic blood pressure and heart rate. We conclude that the spectrum of acute dysautonomia is superimposable on that of the inflammatory peripheric neuropathies and should include both the idiopathic form and dysautonomia with autoimmune associated disorders. IVGG are effective and seems to act by increasing plasma norepinephrine levels.

Abnormal autonomic cardiovascular control in ankylosing spondylitis

OBJECTIVE

This study was aimed at assessing the contribution of the autonomic nervous system to adjustments of cardiovascular function in patients with ankylosing spondylitis (AS).

METHODS

In 18 AS patients (mean age: 34.9; mean disease duration: 6.4 years) and 13 healthy controls (mean age: 31.7) the changes of heart rate (HR) with deep breathing (E/I ratio) and standing up (30/15 ratio) were recorded. The slope of cardiac baroreflex, the times series of blood pressure and HR values upon lying and standing, and venous plasma concentrations of catecholamines were also analysed. Erythrocyte sedimentation rate (ESR), plasma C reactive protein (CRP) concentration and a clinical index (BASDAI score) were used to assess the degree of disease activity in patients.

RESULTS

In the standing patients, blood pressure was found to decrease progressively (p< 0.001). Furthermore, the patients with a BASDAI score > 5 had a higher heart rate than patients with a BASDAI score < 5 (p<0.02), and there was a trend for a similar difference when patients were classified according to their ESR and CRP. Plasma catecholamine concentrations and the E/I ratio were not different in patients from controls. The 30/15 ratio and the slope of the spontaneous baroreflex during standing were both lower in AS patients than controls (p< 0.01).

CONCLUSIONS

This study demonstrated a change in autonomic nervous system function of AS patients, with a decreased parasympathetic activity, as evidenced by higher HR and lower baroreflex slope. As these significant deviances were mainly observed in patients with more active (or more inflammatory) disease, the autonomic nervous system involvement could be related to the inflammatory process. This autonomic strain may be related to the cardiac involvement in AS patients.

Influence of immersion on respiratory requirements during 30-min cycling exercise

Immersion is considered to facilitate exercise-based rehabilitation. However, the drag effect of moving limbs in water, likely to increase the respiratory requirements at exercise, is not mentioned in many reports. The energetic and ventilatory requirements of 30 min steady state cycling exercise performed by healthy male subjects in air and during immersion up to the xiphoid in 33 degrees C water were compared. In the first experimental series nine subjects exercised at the same 60% maximal oxygen consumption (V'O2,max) in air and water. In the two ambient conditions, ventilatory variables had similar values, but the ergometric setting had to be reduced during water immersion so that the workload rated only 69+/-20 W (mean+/-SD) in water versus 121+/-32 W (p<0.001) in air. In the second experimental series, the same ergometric work load (122 W) was achieved by nine subjects with an average V'O2 of 2,210+/-300 mL x min(-1) in air versus 2,868+/-268 mL x min(-1) in water (p<0.001). Resting water immersion caused a marked trend for decreasing vital capacity (p=0.06), but no modification of other ventilatory variables. During exercise at similar V'O2, the average values of minute ventilation (V'E), tidal volume (VT), respiratory frequency (fR), tidal inspiratory time (VT/tI) were not different between water and air. However, at similar ergometric workload, V'E, VT, fR, VT/tI and plasma lactate levels were significantly higher in water than in air. Such consequences of the drag effect of water upon limb movements have not been reported in previous studies relying on shorter exercise bouts. Thus, maintaining steady exercise levels in water either led to a decrease in the workload or required a 25% higher oxygen consumption than in air. These findings may be relevant to the prescription of water immersion rehabilitation programmes.

Active standing and passive tilting similarly reduce the slope of spontaneous baroreflex in healthy subjects

Non-invasive assessment of the sensitivity of cardiac baroreflex was performed by recording each RR-interval and each blood pressure cycle (Finapres). In sequences of at least three cardiac cycles in which systolic blood pressure and RR-interval had changed in the same direction, the slope of linear regression of RR duration as a function of the change in systolic arterial pressure was taken for estimating the sensitivity of the spontaneous cardiac baroreflex. This technique was used in healthy humans to examine how a postural change from supine to upright by either active standing up or 60 degrees head-up tilting modified the sensitivity of the spontaneous baroreflex. We observed that the slope of the spontaneous baroreflex averaged 14.6 +/- 2 ms.mm Hg-1 during rest in the supine position, and decreased to 7.8 +/- 1.2 ms.mm Hg-1 (p < 0.05) after active standing, while the number of sequences was significantly increased in the upright as compared to the supine position. Head-up tilting by 60 degrees led to values similar to those following active standing. The adjustment of baroreflex slope to either postural change occurred in a few seconds, so that posture-characteristic values were obtained from five-minute records. We conclude that non-invasive recording of spontaneous sequences of related changes in blood pressure and RR-interval during several minutes provides reproducible values of the slope of cardiac baroreflex in the supine and upright position. This easy and reliable determination of the sensitivity of the cardiac baroreflex might prove to be useful when assessment of baroreflex function is needed.

Insulin-like growth factor-I and insulin-like growth factor binding protein-3 serum levels in ankylosing spondylitis

OBJECTIVE

Low bone mass, vertebral osteopenia and fractures have been described in patients with ankylosing spondylitis (AS), but the aetiology of this osteoporosis (OP) remains unknown. Insulin-like growth factor-I (IGF-I), a bone-promoting peptide, may be considered as reflecting osteoblast function as well as its main binding protein, insulin-like growth factor binding protein-3 (IGFBP-3). Both were found to be decreased in post-menopausal women and male patients with idiopathic OP. In this study, we aimed to measure the circulating IGF-I and IGFBP-3 in AS patients.

METHODS

Thirty-three AS patients were compared to 23 healthy controls. Bone mineral density (dual X-ray absorptiometry) was measured at the spine and the femoral neck. We determined the serum levels of growth hormone (GH), insulin, glycaemia, and the IGF-I and IGFBP-3 serum concentrations.

RESULTS

A lowered lumbar spine bone mineral density was found in the AS group (AS: 0.946 g/cm2, controls: 1.02 g/cm2; P = 0.05). AS patients had a higher glycaemia than controls, but results were in the normal range. There were no significant differences in the mean values for GH and insulin. Mean IGF-I serum levels were 218.3 ng/ml (+/-72.4) in patients and 212.1 (+/-71.1) in controls (P = 0.75). The serum concentrations of IGFBP-3 were significantly lower in AS (3.29+/-0.6 microg/ml) than in healthy subjects (3.63+/-0.6 microg/ml; P = 0.05). There was a negative correlation between the serum IGFBP-3 concentration and erythrocyte sedimentation rate (r = -0.39; P = 0.025).

CONCLUSIONS

Since IGFBP-3 is an important cofactor for IGF-I and modulates its bioavailability and activity in bone, these data suggest that osteoblast cell function could be impaired in AS. Inflammation could play a role in this IGFBP-3/IGF-I axis involvement. However, further studies are warranted to determine the role of the other growth factors and their binding proteins in the OP of AS.

Influence of exercise duration on serum insulin-like growth factor and its binding proteins in athletes

The changes in circulating concentrations of insulin-like growth factors during exercise have to date remained incomplete in their documentation. Therefore, we examined in 25 healthy athletes the effects of three different durations of three types of exercise -- incremental ergometer cycling exercise (ICE), long-distance Nordic ski race (NSR) and a treadmill-simulated soccer game (TSG) lasting 20 min, 3 h, and 2 x 45 min separated by a 15-min half-time rest respectively, on plasma concentrations of growth hormone ([GH]), insulin-like growth factor-1 ([IGF-I]) and its binding proteins 1 and 3 ([IGFBP-1], [IGFBP-3]). Compared to baseline, serum [GH] increased by 15.2-fold after ICE (P < 0.001), 2.9-fold after NSR (P < 0.01) and 4.6-fold after TSG. Serum [IGF-I] rose by 11.9% after ICE (P < 0.001), while it decreased by -14.6% after NSR (P < 0.001) and was unchanged after TSG. Serum [IGFBP-1] was slightly increased (1.7-fold) after ICE (P < 0.01), but increased markedly (11.8-fold) after NSR (P < 0.001) and by 6.3-fold after the second session of TSG (P < 0.01) (it remained unchanged at the end of the first period of TSG, i.e. after 45-min exercise). The [IGFBP-3] increased by 14.7% after ICE (P < 0.001) and by 6% after TSG (P < 0.05) while it did not change after NSR. From our results it would appear that [IGFBP-1] increase to bind free IGF and hinder their insulin-like action during long-term exercise (lasting beyond 45 min). It is suggested that IGFBP-1 might thus contribute both to preventing hypoglycaemic action of IGF and to facilitating glucose uptake by muscle cells when muscle glycogen stores become deplete.

Oxygen tolerance in patients with acute respiratory failure

OBJECTIVE

To search for a threshold of pulmonary oxygen toxicity in patients with acute respiratory failure.

DESIGN

Retrospective study over a 10-year period.

SETTING

Three intensive care units of two university hospitals.

PATIENTS AND PARTICIPANTS

Seventy-four patients with acute respiratory failure ventilated continuously with a FIO2 > or = 0.9 for at least 48 h were selected.

INTERVENTIONS

Information regarding status, scoring, diagnosis and therapeutic interventions upon admission and ICU course were extracted from the patients' charts.

MEASUREMENTS AND RESULTS

We found that total exposure [mean (standard error of the mean)] to a FIO2 of 0.9 (TE 90) or more was 5.6 (1.1) days in the 17 survivors (S) versus 5.9 (0.5) days in the 57 non-survivors (D) (NS). Total exposure time to a FIO2 more than 0.5 (TE 50) was 16.5 (2.6) days in S and 11.2 (1) days in D (p < 0.05). The PaO2/FIO2 ratio became significantly higher in S only 5 days after beginning FIO2 of 0.9 or more. Hypoxemia was not frequent at the time of death, whereas in 70% of the non-survivors there were at least three organ failures in the last 48 h. In univariate analysis, the duration of exposure to FIO2 of 0.9 or more was not different in survivors and non-survivors, and the average total duration of exposure to FIO2 of more than 0.5 was even longer in survivors. In multivariate analysis, exposure shorter than 10 days to FIO2 more than 0.5 and exposure longer than 4 days to a FIO2 of 0.9 or more were significantly associated with death. However, despite a larger exposure to a FIO2 of 0.9 or more during the last 5 years of the study, the trend moved towards a higher survival rate during this period compared with the first 5 years of the study.

CONCLUSIONS

Thus, our data provide circumstantial evidence that the lungs of patients with acute respiratory failure might exhibit some relative resistance to prolonged oxygen exposure. Therefore, it might be worthwhile carrying out a prospective study of different FIO2 strategies in such patients.

Effects of i.v. insulin bolus on urinary calcium and oxalate excretion in healthy subjects

Oral glucose load increases urinary excretion of calcium (Ca) and oxalate. Although this increase in calciuria is commonly ascribed to insulin, the role of glucose on Ca excretion remains unclear. In order to assess the role of glucose changes on calciuric response to insulin and oxalate excretion, hypoglycemia induced by insulin (hypo) and hyperglycemia induced by oral glucose load (hyper) were studied in 7 healthy subjects on two separate days. As expected, glycemia dropped in hypo (-70%, p<0.001) and increased in hyper (+67%, p<0.001). Calciuria increased on the two days,+205%, p<0.001 (hypo) vs + 43%, p < 0.05 (hyper) as a result of both a rise in calcium filtered load (FCa) and a decrease in tubular reabsorption of calcium (TRCa). While the increase in FCa was similar in the two situations, the higher increased calciuria in hypo (p<0.01) was linked to a deeper decrease in TRCa, - 2.1 % (hypo) vs - 1.4% (hyper), p < 0.01. Although the estimated amounts of insulin were similar in the two situations, the insulin kinetics were different. Thus, after insulin injection, the putative role of the high initial insulin spike in triggering the increase in calciuria cannot be ruled out. The deeper decrease in TRCa (hypo) was also likely due to both hypoglycemia and changes in counter-regulation hormones. In conclusion, calciuria increased after either hypo or hyperglycemia and the higher increase in calciuria observed in hypo was subsequent to a deeper decrease in tubular Ca reabsorption. Oxaluria did not change in hypo, while it increased in hyper.

Aspartame ingestion increases urinary calcium, but not oxalate excretion, in healthy subjects

Aspartame is the artificial sweetener most extensively used as a substitute for glucose or sucrose in the food industry, particularly in soft drinks. As glucose ingestion increases calciuria and oxaluria, the two main determinants of urinary calcium-oxalate saturation, we considered it worthwhile to determine whether aspartame ingestion also affects calcium-oxalate metabolism. Our study compares the effects of the ingestion of similarly sweet doses of aspartame (250 mg) and glucose (75 g) on calcium and oxalate metabolisms of seven healthy subjects. Urinary calcium excretion increased after the intake of both aspartame (+86%; P < 0.01) and glucose (+124%; P < 0.01). This may be due to the rise in calcemia observed after both aspartame (+2.2%; P < 0.05) and glucose ingestion (+1.8%; P < 0.05). The increased calcemia may be linked to the decrease in phosphatemia that occurred after both aspartame (P < 0.01) and glucose (P < 0.01) load. Aspartame did not alter glycemia or insulinemia, whereas glucose intake caused striking increases in both glycemia (+59%; P < 0.001) and insulinemia (+869%; P < 0.01). Although insulin was considered the main calciuria-induced factor after glucose load, it is unlikely that this mechanism played a role with aspartame. Urinary oxalate excretion did not change after aspartame, whereas it increased (+27%; P < 0.05) after glucose load. Thus, as aspartame induced a similar increase in calciuria as did glucose but, conversely, no change in oxaluria, substituting glucose by aspartame in soft drinks may appear to be of some potential benefit.

Nasal mucosa inflammation induced by oxygen administration in humans

BACKGROUND

The effect of oxygen toxicity in human airways is still poorly documented. We prospectively evaluated the inflammatory reaction induced by nasal oxygen exposure in an experimental setting.

METHODS

Healthy subjects without nasal symptoms were exposed to high FIO2 during 5 h. Oxygen was delivered from a tank at a flow of 4 l/min to one nostril of each subject and both nostrils were studied. Mucociliary clearance was measured as saccharine nasal transit time (SNTT). Nasal lavage was performed with 5 ml normal saline and the fluid recovered was processed for cytology and measurements of cytokines concentrations: TNF alpha, IL-6, IL-8 and soluble ICAM-1. Under local anaesthesia, biopsies were performed for immunochemistry and electron microscopy.

RESULTS

After oxygen exposure mucociliary clearance decreased and SNTT increased from 16 [9-21] to 20.5 [14-32] min (median and extremes; P < 0.1). In the lavage fluid, concentration of IL-6 was higher in the oxygen-exposed nostril (40.5 [11-128] pg/ml) than in the non-exposed one (7 [0-34] pg/ml; P < 0.05). There was also a trend for a higher IL-8 in the exposed than in the non-exposed nostril, (respectively 501 [214-587] pg/ml and 214 [122-616] pg/ml, P < 0.08), and for a higher number of polymorphonuclear cells in exposed nostril. In the mucosal biopsies substance P was not found, but ICAM-1 expression was higher in the mucosa and submucosa of the exposed nostrils where mast cells were also more abundant and showed piecemeal degranulation.

CONCLUSION

In summary, we found clinical, functional and biological evidence of ongoing nasal inflammation following high FIO2 inhalation for 5 h. Since the histology and behaviour of nasal and bronchi mucosa are very similar, the same inflammatory events are likely to be occurring in the bronchi upon high concentrations of inhaled oxygen.

No trend toward a spontaneous improvement of hyperparathyroidism and high bone turnover in normocalcemic long-term renal transplant recipients

Although hyperparathyroidism is a common feature in renal transplant recipients, the long-term course of parathyroid hormone (PTH) secretion in these patients is not well established, and the actual contribution of PTH to posttransplant bone disease remains incompletely understood. Therefore, we studied calcium-regulating hormones and serum osteocalcin, as a marker of bone remodeling, in 82 normocalcemic renal transplant recipients with good renal function who had received a graft 6 to 73 months previously and in 82 healthy subjects matched for age and sex. In all subjects, fasting serum and 24-hour urinary samples were collected. The transplant recipients had excessive PTH secretion (serum PTH, 6.9 +/- 0.5 pmol/L in recipients v 3.0 +/- 0.1 pmol/L in healthy subjects; P < 0.001) and high bone turnover (osteocalcin, 16.6 +/- 0.8 microg/L v 8.0 +/- 0.3 microg/L; P < 0.001). (Values are mean +/- SEM.) In addition, transplant recipients had a slightly higher ionized calcium than the healthy subjects, providing definite evidence of an inappropriate PTH secretion in renal transplant recipients. Furthermore, in subgroups of 25 recipients and 25 healthy controls matched for creatinine clearance, the results superimposed those obtained in the whole groups, suggesting that excessive PTH secretion and high bone turnover in renal transplant recipients did not merely reflect the moderately reduced renal function of some recipients. In the whole group of transplant recipients, PTH correlated positively with osteocalcin (r = 0.40; P < 0.001), suggesting that PTH contributes at least partly to posttransplant bone disease. Conversely, there was no correlation between serum PTH or osteocalcin and the delay from grafting. Therefore, our results provide no evidence for a spontaneous improvement of either persistent hyperparathyroidism or high bone turnover in normocalcemic long-term renal transplant recipients.

Lack of increased urinary calcium-oxalate supersaturation in long-term kidney transplant recipients

Nephrolithiasis is uncommon after kidney transplantation. However, calcium (Ca) supplementation, which has been proposed as a treatment of post-transplant osteopenia, might increase calciuria and bolster Ca stone formation. Therefore, in 24-hour urine of 82 normocalcemic long-term renal transplant recipients (RT) and in 82 healthy subjects (HS), we assessed some Ca nephrolithiasis risk factors and the Ca-salt saturation estimated by the ion-activity product index (AP) and relative supersaturation (RS). In RT, calciuria was lower (mean +/- SD, 3.20 +/- 2.25 vs. 4.61 +/- 1.71 mmol/day; P < 0.001), urinary volume higher (2.41 +/- 0.83 vs. 1.39 +/- 0.53 liter/day; P < 0.001), oxaluria higher (419 +/- 191 vs. 311 +/- 79 mumol/day; P < 0.001) and citraturia lower (1.40 +/- 1.36 vs. 3.77 +/- 1.36 mmol/day; P < 0.001) than in HS. As a result, Ca-oxalate supersaturation was lower in RT than HS (AP, 1.07 +/- 0.69 vs. 2.07 +/- 1.13, P < 0.001; and RS, 0.62 +/- 0.26 vs. 0.94 +/- 0.21, P < 0.001), and was similar in subgroups of RT (N = 37) and HS (N = 37) matched for urinary volume, demonstrating that even without any larger urinary volume, Ca-oxalate saturation was not higher in RT than HS, and suggesting that opposite changes in Ca and oxalate in RT likely canceled their effects on lithogenic risk. In RT which had similar urinary pH and phosphate (P) than HS, Ca-P supersaturation was lower than in HS for brushite (AP, 3.25 +/- 6.67 vs. 6.01 +/- 4.85, P < 0.001; RS, -0.33 +/- 0.76 vs. 0.48 +/- 0.53, P < 0.001) and octacalcium phosphate (RS, -0.95 +/- 0.72 vs. 0.21 +/- 0.85, P < 0.001), and similar for apatite. Finally, fasting calciuria and calciuric response to a single oral Ca load were similar in RT (N = 19) and HS (N = 8). Together, these results argue strongly against a higher risk of Ca stone formation in RT than HS, even in case of Ca supplementation.

Characterization of human platelet receptors for atrial natriuretic peptide: evidence for clearance receptors

Characterization of human platelet receptors for atrial natriuretic peptide (ANP) has been performed using two different methods. First, intracellular cGMP levels were measured after platelet stimulation with humanANP (hANP) and CNP, in order to detect the presence of ANP-A or ANP-B receptors. The intracellular cGMP content was not modified either after hANP or CNP platelet stimulation and thus indicated the lack of biological active receptors on these cells. Second, displacements of 125I-hANP were similar when induced by hANP or C4-23ANP (specific ligand of clearance receptor). Consequently, these results confirmed that human platelet membranes bore only clearance receptors for atrial natriuretic peptide.