Effects of daily artificial gravity training on orthostatic tolerance following 60-day strict head-down tilt bedrest.

PURPOSE: Orthostatic intolerance commonly occurs following immobilization or space flight. We hypothesized that daily artificial gravity training through short-arm centrifugation could help to maintain orthostatic tolerance following head-down tilt bedrest, which is an established terrestrial model for weightlessness. METHODS: We studied 24 healthy persons (eight women; age 33.3 ± 9.0 years; BMI 24.3 ± 2.1 kg/m2) who participated in the 60-days head-down tilt bedrest (AGBRESA) study. They were assigned to 30 min/day continuous or 6 × 5 min intermittent short-arm centrifugation with 1Gz at the center of mass or a control group. We performed head-up tilt testing with incremental lower-body negative pressure until presyncope before and after bedrest. We recorded an electrocardiogram, beat-to-beat finger blood pressure, and brachial blood pressure and obtained blood samples from an antecubital venous catheter. Orthostatic tolerance was defined as time to presyncope. We related changes in orthostatic tolerance to changes in plasma volume determined by carbon dioxide rebreathing. RESULTS: Compared with baseline measurements, supine and upright heart rate increased in all three groups following head-down tilt bedrest. Compared with baseline measurements, time to presyncope decreased by 323 ± 235 s with continuous centrifugation, by 296 ± 508 s with intermittent centrifugation, and by 801 ± 354 s in the control group (p = 0.0249 between interventions). The change in orthostatic tolerance was not correlated with changes in plasma volume. CONCLUSIONS: Daily artificial gravity training on a short-arm centrifuge attenuated the reduction in orthostatic tolerance after 60 days of head-down tilt bedrest.

Streambed immobilization controls the transport of antibiotic resistance genes in flowing water.

Antibiotic resistance is a serious global health issue, resulting in at least 1.2 million deaths in 2019. The environment is a potentially important reservoir of antibiotic resistance; however, the fate of Antibiotic Resistance Genes (ARGs) in the environment remains poorly characterized. One important environmental source of ARGs is manure used as a soil amendment. ARGs from manure may then enter nearby flowing waterbodies, where the factors governing their downstream transport remain unknown. To address this, we conducted experiments by spiking cattle manure in an artificial stream to estimate removal rates (k; m-1) for three ARGs (mefA, tetQ, and tetW) and a ruminant fecal marker (bacR). We then used a Stochastic Mobile-Immobile Model (SMIM) to separate the overall removal into two components, rs, and rh, corresponding to immobilizations in the surface (i.e., water column) and subsurface (i.e., streambed), respectively. Finally, we applied the SMIM across four model streams to predict the downstream travel distance of ARGs and bacR. Our results showed measurable removal for all targets in all experimental replicates (n = 3) and no differences were found in the removal rates among replicates for any target (ANCOVA; p > 0.05). We found that the removal of bacR was significantly lower than tetW (p < 0.05) and slightly lower than mefA (p = 0.088), while tetQ removal was slightly different from tetW's (p = 0.072). We also found that rh values were orders of magnitude larger than rs for ARGs and bacR (t-test; p < 0.05). These findings suggest that ARGs and bacR are being removed from the water column through immobilization reactions occurring in the streambed. Additionally, we predicted that the 90 % removal (or D90) of targets occurs within the first 500 m in all model streams except in a slow-flow pastoral stream, which required 1400 m of downstream transport for 90 % removal. Our findings and model stand out as promising tools to predict the fate of ARGs in streams and will contribute to improving and managing agricultural practices that employ animal manure.

Cardiopulmonary deconditioning and plasma volume loss are not sufficient to provoke orthostatic hypertension.

Orthostatic hypertension, defined by an increase of systolic blood pressure (SBP) of ≥20 mmHg upon standing, harbors an increased cardiovascular risk. We pooled data from two rigorously conducted head-down tilt bedrest studies to test the hypothesis that cardiopulmonary deconditioning and hypovolemia predispose to orthostatic hypertension. With bedrest, peak VO2 decreased by 6 ± 4 mlO2/min/kg (p < 0.0001) and plasma volume by 367 ± 348 ml (p < 0.0001). Supine SBP increased from 127 ± 9 mmHg before to 133 ± 10 mmHg after bedrest (p < 0.0001). In participants with stable hemodynamics following head-up tilt, the incidence of orthostatic hypertension was 2 out of 67 participants before bedrest and 2 out of 57 after bedrest. We conclude that in most healthy persons, cardiovascular deconditioning and volume loss associated with long-term bedrest are not sufficient to cause orthostatic hypertension.

Impact of daily artificial gravity on autonomic cardiovascular control following 60-day head-down tilt bed rest.

Impaired cardiovascular autonomic control following space flight or immobilization may limit the ability to cope with additional hemodynamic stimuli. Head-down tilt bedrest is an established terrestrial analog for space flight and offers the opportunity to test potential countermeasures for autonomic cardiovascular deconditioning. Previous studies revealed a possible benefit of daily artificial gravity on cardiovascular autonomic control following head-down tilt bedrest, but there is a need for efficiency in a long-term study before an artificial gravity facility would be brought to space. We hypothesized that artificial gravity through short-arm centrifugation attenuates functional adaptions of autonomic function during head-down tilt bed rest. 24 healthy persons (8 women, 33.4 ± 9.3 years, 24.3 ± 2.1 kg/m2) participated in the 60-day head-down tilt bed rest (AGBRESA) study. They were assigned to three groups, 30 min/day continuous, or 6(5 min intermittent short-arm centrifugation, or a control group. We assessed autonomic cardiovascular control in the supine position and in 5 minutes 80° head-up tilt position before and immediately after bed rest. We computed heart rate variability (HRV) in the time (rmssd) and frequency domain, blood pressure variability, and baroreflex sensitivity (BRS). RR interval corrected rmssd was reduced supine (p = 0.0358) and during HUT (p = 0.0161). Heart rate variability in the high-frequency band (hf-RRI; p = 0.0004) and BRS (p < 0.0001) decreased, whereas blood pressure variability in the low-frequency band (lf-SBP, p = 0.0008) increased following bedrest in all groups. We did not detect significant interactions between bedrest and interventions. We conclude that up to daily 30 min of artificial gravity on a short-arm centrifuge with 1Gz at the center of mass do not suffice to prevent changes in autonomic cardiovascular control following 60-day of 6° head-down tilt bed rest. Clinical Trial Registration: https://drks.de/search/en/trial/DRKS00015677, identifier, DRKS00015677.

Predicting nitrous oxide emissions through riverine networks.

Nitrous oxide (N2O) is currently the leading ozone-depleting gas and is also a potent greenhouse gas. Predictions of N2O emissions from riverine systems are difficult and mostly accomplished via regression equations based on dissolved inorganic nitrogen (DIN) concentrations or fluxes, although recent studies have shown that hydromorphological characteristics can influence N2O emissions in riverine reaches. Here, we propose a predictive model for N2O riverine concentrations and emissions at the reach scale. The model is based on Damköhler numbers and captures the primary effects of reach-scale biogeochemical and hydromorphological characteristics in flowing waters. It explains the change in N2O emissions from small streams to large rivers under varying conditions including biome, land use, climate, and nutrient availability. The model and observed data show that dimensionless N2O concentrations and emission rates have higher variability and mean values for small streams (reach width <10 m) than for larger streams due to high spatial variability of stream hydraulics and morphology.

Control of nitrogen export from watersheds by headwater streams.

A comparative (15)N-tracer study of nitrogen dynamics in headwater streams from biomes throughout North America demonstrates that streams exert control over nutrient exports to rivers, lakes, and estuaries. The most rapid uptake and transformation of inorganic nitrogen occurred in the smallest streams. Ammonium entering these streams was removed from the water within a few tens to hundreds of meters. Nitrate was also removed from stream water but traveled a distance 5 to 10 times as long, on average, as ammonium. Despite low ammonium concentration in stream water, nitrification rates were high, indicating that small streams are potentially important sources of atmospheric nitrous oxide. During seasons of high biological activity, the reaches of headwater streams typically export downstream less than half of the input of dissolved inorganic nitrogen from their watersheds.

The effects of season and agriculture on nitrous oxide production in headwater streams.

Streams and rivers are a globally significant source of nitrous oxide (N(2)O), a potent greenhouse gas. However, there remains much uncertainty in the magnitude of N(2)O emissions from these sources, partly due to an incomplete understanding of the factors that control microbial N(2)O production in lotic sediments. During 2004-2005 we measured sediment N(2)O production in 12 headwater streams across an agricultural land use gradient. Stream water nitrate (NO(3)(-)) concentrations were positively related to the proportion of agricultural land use in the basin and frequently exceeded 20 mg N L(-1) in the stream draining the most agricultural basin. Stream sediments were nearly always a net source of N(2)O, and production rates were positively related to stream water NO(3)(-) concentrations and sediment carbon content. There were no seasonal patterns in N(2)O production rates during 2004, but stream water NO(3)(-) and N(2)O production both peaked during the winter of 2005. The spike in NO(3)(-) concentrations likely resulted from winter rain and snowmelt that flushed NO(3)(-) from the soils following a dry summer and fall. In turn, the elevated stream water NO(3)(-) concentrations stimulated in-stream N(2)O production rates. Overall, we were only able to explain 29% of the variation in N(2)O production rates on a log scale. The unexplained variation may be due to differences in the fraction of denitrified NO(3)(-) that is converted to N(2)O among the study sites, or that our measures of substrate availability in the water column were not reflective of substrate availability in the porewater used by denitrifiers.

[Leiomyoma of the esophagus : A further indication for robotic surgery?] / Das Leiomyom des Ösophagus : Eine weitere Indikation für den Roboter?

BACKGROUND: Leiomyomas of the esophagus are rare tumors but the most common benign lesion of the esophagus originating from smooth muscle cells. The symptoms are mainly determined by the size of the tumor and are caused by dysphagia and/or retrosternal pain. The majority of patients are however asymptomatic. The diagnostics include esophagoscopy, endosonography and chest computed tomography. Surgery is considered the treatment of choice and ideally involves enucleation of the tumor but may lead to esophagectomy. In addition to the classical open procedures, minimally invasive procedures are also used. Regardless of the selected procedure, a lesion of the mucosa should be avoided. OBJECTIVE: A review of the literature on thoracoscopic and robotic resections in the treatment of leiomyomas was carried out and an illustration of a clinical case is presented. MATERIAL AND METHODS: A review of minimally invasive surgical treatment of esophageal leiomyomas is presented. The literature search was carried out in PubMed for publications of thoracoscopic and robotic-assisted thoracic enucleation of leiomyomas of the esophagus. In addition, the robotic-assisted thoracic enucleation of a horseshoe-shaped leiomyoma in the middle third of the esophagus is described. RESULTS: The enucleation of the esophageal leiomyoma was carried out through a right-sided robotic-assisted operation with one lung ventilation. The surgery time was 143 min. There were no intraoperative or postoperative complications. On the 3rd postoperative day a light diet was started and the thorax drainage was removed. Histopathology confirmed a leiomyoma. The patient was discharged on the 5th postoperative day and free of complaints. CONCLUSION: Robotic-assisted surgery for leiomyomas of the esophagus is a safe procedure. Taking the available data into account, robotic-assisted thoracic enucleation of leiomyomas was characterized by less mucosal lesions, general complications and a lower conversion rate as well as a shorter hospital stay compared to classical thoracoscopic enucleation. Thus, robotic-assisted surgery can be the method of choice for leiomyomas of the esophagus.

Sorption of imidazolium-based ionic liquids to aquatic sediments.

Ionic liquids (ILs) have received much attention as "green" alternatives to traditional solvents because they do not evaporate, eliminating concerns over fugitive emissions. However, if ionic liquids are used in industrial applications, they may enter aquatic systems via effluent, and their fate and transport may be influenced by sorption to sediments. In this study, we conducted batch mixing experiments with four alkylmethylimidizolium-based ILs and four types of aquatic sediments to asses the capacity for natural aquatic sediments to remove these chemicals from the water column. The concentration isotherms were non linear with point estimates of the distribution coefficient (K(d)) decreasing with increasing concentration. Apparent distribution coefficients ranged from 7.9 to 95.7l kg(-1) at an initial concentration of 0.5mM and were positively related to sediment organic matter (SOM) content. These K(d) values indicate that the ILs did not sorb strongly to the tested sediments. Increased alkyl chain length did not lead to increased sorption suggesting that hydrophobic interactions were not the most important sorption mechanism. We conclude that aquatic sediments have a limited capacity to sorb alkylmethylimidazolium ILs and that the transport of these contaminants in aquatic systems will not be strongly attenuated by sediments.

Yohimbine in neurally mediated syncope. Pathophysiological implications.

In this study, we evaluated if increased sympathetic stimulation is an essential requirement for the development of neurally mediated syncope (NMS) by manipulating overall sympathetic outflow in subjects susceptible to tilt-induced syncope. Eight previously characterized patients with recurrent NMS (five females and three males; 34+/-2 yr) were recruited from the Vanderbilt Syncope Unit and eight age-matched controls underwent initial administration of clonidine (CLO) or yohimbine (YHO). This was done, prospectively, to determine doses of these agents that would increase or decrease plasma norepinephrine levels by >/= 30%. On a different day, in all subjects we determined intraarterial blood pressure, EKG and muscle sympathetic nerve activity (MSNA) both supine and during upright tilt. After this, subjects randomly received either CLO or YHO, and 3 h later another tilt was performed. After 1 wk, a similar procedure with the other drug was performed. During the two basal tilts, all the control subjects completed the study, whereas all the NMS patients developed syncope. Reduction in sympathetic tone by CLO resulted in a decreased tolerance to tilt in three out of eight controls and in all the NMS patients. In contrast, YHO not only increased basal plasma NorEpi levels and MSNA, but also prevented syncope in seven out of eight patients. In a selected population of patients, increased sympathetic activity is not a prerequisite for the development of syncope. Yohimbine-induced enhancement of sympathetic tone in patients with NMS improves orthostatic tolerance and raises the possibility that this drug may be a useful agent in the treatment of NMS.

Correction to 'On the possibility (or lack thereof) of agreement between experiment and computation of flows over wings at moderate Reynolds number'.

[This corrects the article DOI: 10.1098/rsfs.2016.0076.].

On the possibility (or lack thereof) of agreement between experiment and computation of flows over wings at moderate Reynolds number.

The flight of many birds and bats, and their robotic counterparts, occurs over a range of chord-based Reynolds numbers from 1 × 104 to 1.5 × 105. It is precisely over this range where the aerodynamics of simple, rigid, fixed wings becomes extraordinarily sensitive to small changes in geometry and the environment, with two sets of consequences. The first is that practical lifting devices at this scale will likely not be simple, rigid, fixed wings. The second is that it becomes non-trivial to make baseline comparisons for experiment and computation, when either one can be wrong. Here we examine one ostensibly simple case of the NACA 0012 aerofoil and make careful comparison between the technical literature, and new experiments and computations. The agreement (or lack thereof) will establish one or more baseline results and some sensitivities around them. The idea is that the diagnostic procedures will help to guide comparisons and predictions in subsequent more complex cases.

Efficient bridging of 20 mm rat sciatic nerve lesions with a longitudinally micro-structured collagen scaffold.

An increasing number of biomaterial nerve guides has been developed that await direct comparative testing with the 'gold-standard' autologous nerve graft in functional repair of peripheral nerve defects. In the present study, 20 mm rat sciatic nerve defects were bridged with either a collagen-based micro-structured nerve guide (Perimaix) or an autologous nerve graft. Axons regenerated well into the Perimaix scaffold and, the majority of these axons grew across the 20 mm defect into the distal nerve segment. In fact, both the total axon number and the number of retrogradely traced somatosensory and motor neurons extending their axons across the implant was similar between Perimaix and autologous nerve graft groups. Implantation of Schwann cell-seeded Perimaix scaffolds provided only a beneficial effect on myelination within the scaffold. Functional recovery supported by the implanted, non-seeded Perimaix scaffold was as good as that observed after the autologous nerve graft, despite the presence of thinner myelin sheaths in the Perimaix implanted nerves. These findings support the potential of the Perimaix collagen scaffold as a future off-the-shelf device for clinical applications in selected cases of traumatic peripheral nerve injury.

Oscillatory patterns in sympathetic neural discharge and cardiovascular variables during orthostatic stimulus.

BACKGROUND: We tested the hypothesis that a common oscillatory pattern might characterize the rhythmic discharge of muscle sympathetic nerve activity (MSNA) and the spontaneous variability of heart rate and systolic arterial pressure (SAP) during a physiological increase of sympathetic activity induced by the head-up tilt maneuver. METHODS AND RESULTS: Ten healthy subjects underwent continuous recordings of ECG, intra-arterial pressure, respiratory activity, central venous pressure, and MSNA, both in the recumbent position and during 75 degrees head-up tilt. Venous samplings for catecholamine assessment were obtained at rest and during the fifth minute of tilt. Spectrum and cross-spectrum analyses of R-R interval, SAP, and MSNA variabilities and of respiratory activity provided the low (LF, 0.1 Hz) and high frequency (HF, 0.27 Hz) rhythmic components of each signal and assessed their linear relationships. Compared with the recumbent position, tilt reduced central venous pressure, but blood pressure was unchanged. Heart rate, MSNA, and plasma epinephrine and norepinephrine levels increased, suggesting a marked enhancement of overall sympathetic activity. During tilt, LF(MSNA) increased compared with the level in the supine position; this mirrored similar changes observed in the LF components of R-R interval and SAP variabilities. The increase of LF(MSNA) was proportional to the amount of the sympathetic discharge. The coupling between LF components of MSNA and R-R interval and SAP variabilities was enhanced during tilt compared with rest. CONCLUSIONS: During the sympathetic activation induced by tilt, a similar oscillatory pattern based on an increased LF rhythmicity characterized the spontaneous variability of neural sympathetic discharge, R-R interval, and arterial pressure.

Severely impaired baroreflex-buffering in patients with monogenic hypertension and neurovascular contact.

BACKGROUND: We identified a family with a monogenic syndrome of hypertension, brachydactyly, and neurovascular contact of the brain stem. Neurovascular contact of the ventrolateral medulla may lead to arterial hypertension by interfering with baroreflex function. METHODS AND RESULTS: In 5 patients with monogenic hypertension (18 to 34 years old), we conducted detailed autonomic function tests. Blood pressure during complete ganglionic blockade was 134+/-4.9/82+/-4.1 mm Hg and 90+/-6/49+/-2.4 mm Hg in patients and in control subjects, respectively. During ganglionic blockade, plasma vasopressin concentration increased 24-fold in control subjects and <2-fold in patients. In patients, cold pressor testing, hand-grip testing, and upright posture all increased blood pressure excessively. In contrast, muscle sympathetic nerve activity was not increased at rest or during cold pressor testing. The phenylephrine dose that increased systolic blood pressure 12.5 mm Hg was 8.0+/-2.0 microg in patients and 135+/-35 microg in control subjects before ganglionic blockade and 5.4+/-0.4 microg in patients and 13+/-4.8 microg in control subjects during ganglionic blockade. CONCLUSIONS: In patients with monogenic hypertension and neurovascular contact, basal blood pressure was increased even during sympathetic and parasympathetic nerve traffic interruption. However, sympathetic stimuli caused an excessive increase in blood pressure. This excessive response cannot be explained by increased sympathetic nerve traffic or increased vascular sensitivity. Instead, we suggest that baroreflex buffering and baroreflex-mediated vasopressin release are severely impaired.

A review of ecological effects and environmental fate of illicit drugs in aquatic ecosystems.

Although illicit drugs are detected in surface waters throughout the world, their environmental fate and ecological effects are not well understood. Many illicit drugs and their breakdown products have been detected in surface waters and temporal and spatial variability in use translates into "hot spots and hot moments" of occurrence. Illicit drug occurrence in regions of production and use and areas with insufficient wastewater treatment are not well studied and should be targeted for further study. Evidence suggests that illicit drugs may not be persistent, as their half-lives are relatively short, but may exhibit "pseudo-persistence" wherein continual use results in persistent occurrence. We reviewed the literature on the ecological effects of these compounds on aquatic organisms and although research is limited, a wide array of aquatic organisms, including bacteria, algae, invertebrates, and fishes, have receptors that make them potentially sensitive to these compounds. In summary, illicit drugs occur in surface waters and aquatic organisms may be affected by these compounds; research is needed that focuses on concentrations of illicit drugs in areas of production and high use, environmental fate of these compounds, and effects of these compounds on aquatic ecosystems at the concentrations that typically occur in the environment.

Interaction between beta-adrenergic receptor stimulation and nitric oxide release on tissue perfusion and metabolism.

Nitric oxide (NO) may be an important modulator of sympathetic tone. We used im and sc microdialysis in humans to characterize the interaction of NO synthase inhibition and adrenoreceptor stimulation on tissue perfusion, metabolism, and norepinephrine release. Microdialysis probes were perfused with L- or D-nitro-L-arginine-methyl-ester (100 micromol/L) followed by incremental doses of isoproterenol, epinephrine, or nitroprusside. Blood flow was estimated based on the ethanol dilution technique. In muscle, the increase in blood flow with isoproterenol was abolished by L-NAME. The ethanol ratio was 0.03 +/- 0.011 with D-NAME and 0.075 +/- 0.014 with L-NAME during isoproterenol treatment (1 micromol/L). The effect was less pronounced in adipose tissue. The vasodilatory effect of nitroprusside was similar with D- and L-NAME. L-NAME augmented isoproterenol- and epinephrine-induced glycerol release. Dialysate glycerol during 1 micromol/L isoproterenol was 47 +/- 6.7 micromol/L with D-NAME and 72 +/- 15 micromol/L with L-NAME. In skeletal muscle, dialysate norepinephrine during 1 micromol/L isoproterenol treatment was 0.73 +/- 0.17 and 1.3 +/- 0.15 nmol/L with D- and L-NAME, respectively. We conclude that NO synthase inhibition attenuates beta(2)-adrenoreceptor-mediated vasodilation and enhances beta-adrenoreceptor-mediated lipolysis. These effects are in part mediated through an increase in interstitial norepinephrine concentrations. The data are consistent with the idea that in humans, NO is important in modulating and ameliorating sympathetic effects in peripheral tissues.

Reference values of indices of spontaneous baroreceptor reflex sensitivity.

Spontaneous baroreceptor reflex sensitivity (BRS) is a well established method for determining baroreflex function, which can be used to assess the potential impact on survival after myocardial infarction, to detect autonomic dysfunction in diabetic patients and in human essential hypertension. The assessment of impaired spontaneous baroreflex function in individual patients contains important clinical information, but age-dependent reference values are still lacking. In the present study we evaluated spontaneous BRS in healthy human controls to determine reference values as a function of age. Two hundred and sixty-two healthy volunteers divided into six age groups (I: <20 years, f = 11, m = 9, II: 20-29 years, f = 42, m = 37, III: 30-39 years, f = 23, m = 37, IV: 40-49 years, f = 27, m = 22, V: 50-59 years, f = 19, m = 17, VI: 60-69 years, f = 5, m = 13). Electrocardiograms (ECG) and finger arterial BP were measured with each subject in the supine position (sup, 7 min) and during deep breathing (dB, 6/min, 15 cycles). BRS was assessed using the sequence technique and the alpha coefficients as obtained from a power spectrum density estimate. Due to the normal logarithmic distribution of the BRS, the limits for impaired baroreflex function at rest were defined from logarithmic data. The limits for the BRS at rest (P = .025) were calculated as (-0.0283 x age) + 2.5198 for the sequence technique. We did not find significant differences in BRS among the female and male healthy volunteers. Our analysis of the six age groups showed the expected significant decrease in BRS, which was most prominent at the transition from group III (<40 years) to group IV (<50 years). BRS at rest and during deep breathing as well as sequential and spectral BRS indices did differ significantly. The results underline the necessity of reference values to evaluate impaired baroreflex function in individual patients.

Autonomic nervous system function in patients with monogenic hypertension and brachydactyly: a field study in north-eastern Turkey.

Laboratory studies in patients with autosomal-dominant hypertension and brachydactyly showed increased sensitivity to sympathetic stimuli and severe abnormalities in baroreflex buffering. To further elucidate the mechanisms by which impaired baroreflex sensitivity could influence blood pressure (BP), we conducted autonomic testing under field conditions. We studied 17 hypertensive affected (13 to 48 years, BMI 22.7 +/- 6.5 kg/m(2), 160 +/- 23/98 +/- 15 mm Hg) and 12 normotensive non-affected (9 to 60 years, BMI 24.0 +/- 4.7 kg/m(2), 120 +/- 16/70 +/- 10 mm Hg) family members. Pulse intervals and finger BP were measured using the Portapres device. Valsalva ratio, the blood pressure overshoot during phase IV of the Valsalva manoeuver, the Ewing coefficient (RR30/15 ratio), and heart rate and BP variability were similar in affected and non-affected family members. Overall, baroreflex sensitivity calculated using the cross-spectral (BRSLF, BRSHF) and sequence techniques (BRS+, BRS-) was not different between the groups. However, in younger family members, BRS+ was 12 +/- 3.7 and 22 +/- 13 msec/mm Hg in affected and in non-affected family members, respectively. The decline in BRS with age and with increasing blood pressure was absent in affected family members. We conclude that autonomic reflex testing conducted under field conditions is not impaired in patients with monogenic hypertension and brachydactyly. However, noninvasive testing showed impaired baroreflex control of heart rate at a young age. The reduced BRS in young family members with moderate arterial hypertension may suggest that the impaired baroreflex function is not secondary to the hypertension but rather a primary abnormality, which aggravates the progression of hypertension.

Spontaneous baroreflex sensitivity and heart rate variability are not superior to classic autonomic testing in older patients with type 2 diabetes.

BACKGROUND: Early detection of cardiac autonomic neuropathy (CAN) permits individual risk stratification. Spontaneous heart rate variability (HRV) and baroreflex sensitivity (BRS) are suggested to be superior to classic autonomic testing in that they detect CAN earlier, with greater reliability, and do not require the patient's undue attention. METHODS: To test that hypothesis, we studied 53 diabetic patients (mean age, 55 years) and 38 age-matched healthy control subjects (HC). Subjects underwent deep breathing, Valsalva maneuver, and orthostatic testing. Each abnormal test was counted as 1 point. A change in systolic blood pressure during standing of more than 10 mm Hg was graded with a single point; a decrease of more than 20 mm Hg received 2 points. A total score of zero was regarded as no CAN (noCAN), a score > or =4 as severe CAN (sCAN), and scores of 1 to 3 as mild CAN (mCAN). Spontaneous BRS was determined using the sequence technique. HRV was calculated as coefficient of variation (CV), high frequency power (HF) and low frequency power (LF). RESULTS: Mean group values for HRV and BRS were: CV = 3.9+/-1.3; 4.0+/-1.3; 2.4+/-1.1; and 1.2+/-0.4; BRS = 8+/-3; 8+/-5; 5+/-2; and 2+/-2 msec/mm Hg for HC n = 38, noCAN n = 15, mCAN n = 26, and sCAN n = 12, respectively. BRS was similar in HC and patients with noCAN. In sCAN, BRS detected only 10 of 12 patients. HRV and BRS did not improve reclassification based on discriminant analysis. CONCLUSION: BRS and HRV did not detect CAN in older diabetic patients better than classic autonomic testing.