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Purpose: We hypothesised that during a rest-to-exercise transient in hypoxia (H), compared to normoxia (N), (i) the initial baroreflex sensitivity (BRS) decrease would be slower and (ii) the fast heart rate (HR) and cardiac output (CO) response would have smaller amplitude (A1) due to lower vagal activity in H than N. Methods: Ten participants performed three rest-to-50 W exercise transients on a cycle-ergometer in N (ambient air) and three in H (inspired fraction of O2 = 0.11). R-to-R interval (RRi, by electrocardiography) and blood pressure profile (by photo-plethysmography) were recorded non-invasively. Analysis of the latter provided mean arterial pressure (MAP) and stroke volume (SV). CO = HR·SV. BRS was calculated by modified sequence method. Results: Upon exercise onset in N, MAP fell to a minimum (MAPmin) then recovered. BRS decreased immediately from 14.7 ± 3.6 at rest to 7.0 ± 3.0 ms mmHg−1 at 50 W (p < 0.01). The first BRS sequence detected at 50 W was 8.9 ± 4.8 ms mmHg−1 (p < 0.05 vs. rest). In H, MAP showed several oscillations until reaching a new steady state. BRS decreased rapidly from 10.6 ± 2.8 at rest to 2.9 ± 1.5 ms mmHg−1 at 50 W (p < 0.01), as the first BRS sequence at 50 W was 5.8 ± 2.6 ms mmHg−1 (p < 0.01 vs. rest). CO-A1 was 2.96 ± 1.51 and 2.31 ± 0.94 l min−1 in N and H, respectively (p = 0.06). HR-A1 was 7.7 ± 4.6 and 7.1 ± 5.9 min−1 in N and H, respectively (p = 0.81). Conclusion: The immediate BRS decrease in H, coupled with similar rapid HR and CO responses, is compatible with a withdrawal of residual vagal activity in H associated with increased sympathetic drive. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the possibility of extracting protein from chicken feathers. We conducted our research in a controlled laboratory environment, where we carefully washed feathers collected from white broiler chickens. The feathers were ground and hydrolyzed using a 1:10 ratio of 0.2 eq/L of standard sodium hydroxide (NaOH) solution and 28.5 % sodium hydrosulfite (NaHSO3) solutions. The hydrolyzed solution was further processed in a 90 °C water bath for 6 h using a rotor stirrer. After this, the solution was neutralized with 99 % acetic acid (CH3COOH) and filtered. The filtrate was dialyzed with distilled water in a cellophane membrane bag for 24 h. Following dialysis, we obtained two samples of the dried and ground protein. The first sample was subjected to physicochemical analysis, while the second sample was treated with 5 % H2O2 before analysis. Our analysis, conducted using the Kjeldahl and liquid chromatography methods, revealed that 68–78 % of proteins were synthesized. The study of free amino acids found that the highest indicator, which belongs to 38–40 % of cysteine, asparagine, glutamine, and tryptophan in the protein, failed because of alkaline hydrolysis. However, samples 1 and 2 of the protein containing 17 free amino acids were comparable, further validating our findings.

In this work, we discuss the existence and approximate controllability results for impulsive fractional differential systems of order 1

Large body mass (Mb) in vertebrates is associated with longer pulse intervals between heartbeats (PI) and thicker arterial walls. Longer PI increases the time for diastolic pressure decay, possibly resulting in loss of cardiac energy as "oscillatory power," whereas thicker arterial walls may affect the transmission of impulses and sensing of pressure fluctuations thus impairing baroreflex function. We aimed to investigate the effect of growth on the relative cardiac energy loss and baroreflex function. We predicted that 1) the relative use of cardiac energy should be preserved with increased time constant for pressure decay (s = vascular resistance X compliance) and 2) if arterial circumferential distensibility does not change, baroreflex function should be unaltered with Mb. To test these hypotheses, we used green iguanas (Iguana iguana) weighing from 0.03 to 1.34 kg (43-fold increment in Mb). PI (P = 0.037) and s (P = 0.035) increased with Mb, whereas the oscillatory power fraction (P = 0.245) was unrelated to it. Thus, the concomitant alterations of s and PI allowed the conservation of cardiac energy in larger lizards. Larger animals had thicker arterial walls (P = 0.0007) and greater relative collagen content (P = 0.022). Area compliance scaled positively to Mb (P = 0.045), though circumferential distensibility (P = 0.155) and elastic modulus (P = 0.762) were unaltered. In addition, baroreflex sensitivity, measured by both the pharmacological (P = 0.152) and sequence methods (P = 0.088), and the baroreflex effectiveness index (P = 0.306) were also unrelated to Mb. Therefore, changes in arterial morphology did not affect circumferential distensibility and presumably sensing of pressure fluctuation, and the cardiovagal baroreflex is preserved across different body mass; law of Laplace; pharmacological method; sequence method; vascular mechanics. [ABSTRACT FROM AUTHOR]

This paper investigates the issue of existence and approximate controllability results for impulsive fractional differential inclusions with delay of order r ∈ (1 , 2 ] in Banach space. To begin, we analyze existence results for impulsive fractional evolution inclusions with delay using fractional calculations, the r-order cosine family, multivalued maps, and Martelli’s fixed point theorem. The approximate controllability results for impulsive fractional evolution inclusions with delay were then derived using Gronwall’s inequality and the sequence method. Then, we investigate the Sobolev fractional integrodifferential inclusions with finite delay. Moreover, we develop the nonlocal conditions in a given system. Finally, an example is presented to illustrate the main results. [ABSTRACT FROM AUTHOR]

Purpose: We hypothesised that, during a light-to-moderate exercise transient, compared to an equivalent rest-to-exercise transient, (1) a further baroreflex sensitivity (BRS) decrease would be slower, (2) no rapid heart rate (HR) response would occur, and (3) the rapid cardiac output (CO) response would have a smaller amplitude (A1). Hence, we analysed the dynamics of arterial baroreflexes and the HR and CO kinetics during rest-to-50 W (0-50 W) and 50-to-100 W (50-100 W) exercise transients.Methods: 10 subjects performed three 0-50 W and three 50-100 W on a cycle ergometer. We recorded arterial blood pressure profiles (photo-plethysmography) and R-to-R interval (RRi, electrocardiography). The former were analysed to obtain beat-by-beat mean arterial pressure (MAP) and stroke volume (SV). CO was calculated as SV times HR. BRS was measured by modified sequence method.Results: During 0-50 W, MAP transiently fell (- 9.0 ± 5.7 mmHg, p < 0.01) and BRS passed from 15.0 ± 3.7 at rest to 7.3 ± 2.4 ms mmHg-1 at 50 W (p < 0.01) promptly (first BRS sequence: 8.1 ± 4.6 ms mmHg-1, p < 0.01 vs. rest). During 50-100 W, MAP did not fall and BRS passed from 7.2 ± 2.6 at 50 W to 3.3 ± 1.3 ms mmHg-1 at 100 W (p < 0.01) slowly (first BRS sequence: 5.3 ± 3.1 ms mmHg-1, p = 0.07 vs. 50 W). A1 for HR was 9.2 ± 6.0 and 6.0 ± 4.5 min-1 in 0-50 W and 50-100 W, respectively (p = 0.19). The corresponding A1 for CO were 2.80 ± 1.54 and 0.91 ± 0.55 l∙min-1 (p < 0.01).Conclusion: During 50-100 W, with respect to 0-50 W, BRS decreased more slowly, in absence of a prompt pressure decrease. BRS decrease and rapid HR response in 50-100 W were unexpected and ascribed to possible persistence of some vagal tone at 50 W. [ABSTRACT FROM AUTHOR]

The time course for recovery after anesthesia is poorly described for tricaine methanesulfonate (MS-222). We suggest that the baroreflex and the heart rate variability (HRV) could be used to index the recovery of the autonomic modulation after anesthesia. We analyzed the recovery profile of behavioral and physiological parameters over time to analyze the progression of recovery after anesthesia of American bullfrogs with MS-222. Mean heart rate stabilized after 17 h, whereas the baroreflex efficiency index took 23 h and the baroreflex operating gain, 29 h. Mean arterial pressure recovered after 26 h. Power spectral density peaked at 23 h and again after 40 h. Baroreflex was a relevant component of the first phase of HRV, while autonomic modulation for resting may take longer than 40 h. We suggest that physiological recovery is a complex phenomenon with multiple progressive phases, and the baroreflex may be a useful tool to observe the first substantial recovery of post-instrumentation capacity for autonomic modulation. [Display omitted] • Recovery of autonomic modulation from anesthesia is slower than behavioral recovery • The baroreflex is a component of the heart rate variability (HRV) • Recovery of baroreflex occurs concomitantly with the first peak of HRV [ABSTRACT FROM AUTHOR]

Background: Autonomic disorders are an important non-motor feature of Parkinson's disease (PD). Baroreflex sensitivity (BRS) is often used as an indicator of cardiovascular autonomic function, and it is clinically significant. Several different methods of BRS assessment have been described. We evaluated and compared the efficiency of several methods of BRS assessment for additional insight into the underlying physiology and the determination of its severity in patients with PD. Materials and Methods: Eighty-five patients with PD underwent cardiovascular autonomic testing. The Composite Autonomic Scoring Scale (CASS) was used to grade the severity of autonomic impairment and to define the presence of cardiovascular autonomic neuropathy (CAN). BRS was assessed using the Valsalva maneuver (BRS_VM). In addition, spontaneous BRS was computed using the sequence method and the spectral method. Results and Conclusion: There was considerable agreement between the different methods of BRS assessment. Nevertheless, BRS_VM exhibited a higher degree of correlation with cardiovascular autonomic function than spontaneous BRS indexes obtained by the sequence or spectral method. BRS_VM, rather than spontaneous BRS, also had a predictive value for the presence of CAN to the diagnostic criteria by CASS in patients with PD. [ABSTRACT FROM AUTHOR]

BackgroundAutonomic disorders are an important non-motor feature of Parkinson’s disease (PD). Baroreflex sensitivity (BRS) is often used as an indicator of cardiovascular autonomic function, and it is clinically significant. Several different methods of BRS assessment have been described. We evaluated and compared the efficiency of several methods of BRS assessment for additional insight into the underlying physiology and the determination of its severity in patients with PD.Materials and MethodsEighty-five patients with PD underwent cardiovascular autonomic testing. The Composite Autonomic Scoring Scale (CASS) was used to grade the severity of autonomic impairment and to define the presence of cardiovascular autonomic neuropathy (CAN). BRS was assessed using the Valsalva maneuver (BRS_VM). In addition, spontaneous BRS was computed using the sequence method and the spectral method.Results and ConclusionThere was considerable agreement between the different methods of BRS assessment. Nevertheless, BRS_VM exhibited a higher degree of correlation with cardiovascular autonomic function than spontaneous BRS indexes obtained by the sequence or spectral method. BRS_VM, rather than spontaneous BRS, also had a predictive value for the presence of CAN to the diagnostic criteria by CASS in patients with PD.

We hypothesized that during rapid uptilting at rest, due to vagal withdrawal, arterial baroreflex sensitivity (BRS) may decrease promptly and precede the operating point (OP) resetting, whereas different kinetics are expected during exercise steady state, due to lower vagal activity than at rest. To test this, eleven subjects were rapidly (<2 s) tilted from supine (S) to upright (U) and vice versa every 3 min, at rest and during steady-state 50 W pedaling. Mean arterial pressure (MAP) was measured by finger cuff (Portapres) and R-to-R interval (RRi) by electrocardiography. BRS was computed with the sequence method both during steady and unsteady states. At rest, BRS was 35.1 ms·mmHg-1 (SD = 17.1) in S and 16.7 ms·mmHg-1 (SD = 6.4) in U (P < 0.01), RRi was 901 ms (SD = 118) in S and 749 ms (SD = 98) in U (P < 0.01), and MAP was 76 mmHg (SD = 11) in S and 83 mmHg (SD = 8) in U (P < 0.01). During uptilt, BRS decreased promptly [first BRS sequence was 19.7 ms·mmHg-1 (SD = 5.0)] and was followed by an OP resetting (MAP increase without changes in RRi). At exercise, BRS and OP did not differ between supine and upright positions [BRS was 7.7 ms·mmHg-1 (SD = 3.0) and 7.7 ms·mmHg-1 (SD = 3.5), MAP was 85 mmHg (SD = 13) and 88 mmHg (SD = 10), and RRi was 622 ms (SD = 61) and 600 ms (SD = 70), respectively]. The results support the tested hypothesis. The prompt BRS decrease during uptilt at rest may be ascribed to a vagal withdrawal, similarly to what occurs at exercise onset. The OP resetting may be due to a slower control mechanism, possibly an increase in sympathetic activity. [ABSTRACT FROM AUTHOR]

In humans, physical exercise imposes narrower limits for the heart rate (fH) response of the baroreflex, and vascular modulation becomes largely responsible for arterial pressure regulation. In undisturbed reptiles, the baroreflex-related fH alterations at the operating point (Gop) decreases at elevated body temperatures (Tb) and the vascular regulation changes accordingly. We investigated how the baroreflex of rattlesnakes, Crotalus durissus, is regulated during an activity at different Tb, expecting that activity would reduce the capacity of the cardiac baroreflex neural pathway to buffer arterial pressure fluctuations while being compensated by the vascular neural pathway regulation. Snakes were catheterized for blood pressure assessment at three different Tb: 15, 20 and 30 °C. Data were collected before and after activity at each Tb. Baroreflex gain (Gop) was assessed with the sequence method; the vascular limb, with the time constant of pressure decay (τ), using the two-element Windkessel equation. Both Gop and τ reduced when Tb increased. Activity also reduced Gop and τ in all Tb. The relationship between τ and pulse interval (τ/PI) was unaffected by the temperature at resting snakes, albeit it reduced after activity at 20 °C and 30 °C. The unchanged τ/PI and normalized Gop at different Tb indicated those variables are actively adjusted to work at different fH and pressure conditions at rest. Our data suggest that during activity, the baroreflex-related fH response is attenuated and hypertension is buffered by a disproportional increase in the rate which pressure decays during diastole. This compensation seems especially important at higher Tb where Gop is already low. [ABSTRACT FROM AUTHOR]

The most commonly used technique to study the barostatic regulation of blood pressure in ectothermic vertebrates consists of determining the heart rate response to pharmacological manipulations of blood pressure, the so‐called "Oxford method." Although well established, the Oxford method has some important limitations, such as induction of hypervolemia in small animals and undesired effects of vasoactive drugs on central and peripheral baroreflex components. As an alternative, the sequence method, which consists in the computerized evaluation of naturally‐occurring baroreflex adjustments of heart rate without the need for pharmacological administrations, was developed to study baroreflexes. In the present study, we compare this sequence method with the Oxford technique in two teleost species with different life styles, and we assess the optimal software configuration for the employment of the sequence method in fish. Calculation of baroreflex gain through the sequence method was adequate and reliable when the software was configured to search for baroreflex sequences with a minimum length of three cardiac cycles with a delay of one cardiac cycle between fluctuations in mean ventral aortic blood pressure and reflex changes in pulse interval. When properly configured, the sequence and the Oxford methods yielded similar determinations of the baroreflex gain in fish. Research Highlights: The nonpharmacological sequence method was validated to study the baroreflex function of fish.When properly configured, the sequence method yielded determinations of baroreflex gain similar to that of the Oxford method. [ABSTRACT FROM AUTHOR]

Purpose: We analysed the characteristics of arterial baroreflexes during the first phase of apnoea (φ1).Methods: 12 divers performed rest and exercise (30 W) apnoeas (air and oxygen). We measured beat-by-beat R-to-R interval (RRi) and mean arterial pressure (MAP). Mean RRi and MAP values defined the operating point (OP) before (PRE-ss) and in the second phase (φ2) of apnoea. Baroreflex sensitivity (BRS, ms·mmHg-1) was calculated with the sequence method.Results: In PRE-ss, BRS was (median [IQR]): at rest, 20.3 [10.0-28.6] in air and 18.8 [13.8-25.2] in O2; at exercise 9.2[8.4-13.2] in air and 10.1[8.4-13.6] in O2. In φ1, during MAP decrease, BRS was lower than in PRE-ss at rest (6.6 [5.3-11.4] in air and 7.7 [4.9-14.3] in O2, p < 0.05). At exercise, BRS in φ1 was 6.4 [3.9-13.1] in air and 6.7 [4.1-9.5] in O2. After attainment of minimum MAP (MAPmin), baroreflex resetting started. After attainment of minimum RRi, baroreflex sequences reappeared. In φ2, BRS at rest was 12.1 [9.6-16.2] in air, 12.9 [9.2-15.8] in O2. At exercise (no φ2 in air), it was 7.9 [5.4-10.7] in O2. In φ2, OP acts at higher MAP values.Conclusion: In apnoea φ1, there is a sudden correction of MAP fall via baroreflex. The lower BRS in the earliest φ1 suggests a possible parasympathetic mechanism underpinning this reduction. After MAPmin, baroreflex resets, displacing its OP at higher MAP level; thus, resetting may not be due to central command. After resetting, restoration of BRS suggests re-establishment of vagal drive. [ABSTRACT FROM AUTHOR]

To evaluate the photobiomodulation (PBM) effect on the cardiovascular autonomic control, analyzed by baroreflex sensitivity (sequence method), during constant load exercise and recovery in diabetic men, we evaluated 11 men with type 2 diabetes (DM2) (40-64 years). The constant workload exercise protocol (TECC) was performed on two different days, 14 days apart from each other, to guarantee PBM washout period. After PBM by light-emitting diode (LED) irradiation (150 J or 300 J or placebo), 10 min of rest (REST) was performed. After this period, the volunteer was positioned on a cycloergometer to start the test (1-min rest, 3-min free-load heating, 6-min constant workload-EXERCISE, 6-min free-load cool-down, 1-min rest) followed by a sitting period of 10 min (RECOVERY). The constant workload corresponded to 80%VO2GET (gas exchange threshold) identified by a previous cardiopulmonary exercise test (CPET). PBM was applied in continuous mode, contact technique, bilaterally, on both femoral quadriceps and gastrocnemius muscle groups. The electrocardiogram R-R intervals (BioAmp FE132) and the peripheral pulse pressure signals (Finometer PRO) were collected continuously throughout the protocol. Stable sequences of 256 points were chosen at REST, EXERCISE, and RECOVERY. The baroreflex sensitivity (BRS) was computed in time domain according to the sequence method (αseq). The comparison between therapies (150 J/300 J/placebo) and condition (REST, EXERCISE, and RECOVERY) was performed using the ANOVA two-way repeated measures test. There was no interaction between therapy and conditions during the TECC. There was only the condition effect (p < 0.001), showing that the behavior of αseq was similar regardless of the therapy. Photobiomodulation with 150 J or 300 J applied previously to a moderate-intensity TECC in DM2 was not able to promote cardiovascular autonomic control changes leading to an improvement in BRS. [ABSTRACT FROM AUTHOR]

Accurate detection of acne plays a crucial role in acquiring precise diagnosis and conducting proper therapy. However, the ambiguous boundaries and arbitrary dimensions of acne lesions severely limit the performance of existing methods. In this study, we address these challenges via a novel Decoupled Sequential Detection Head (DSDH), which can be easily adopted by mainstream two-stage detectors. DSDH brings two simple but effective improvements to acne detection. Firstly, the offset and scaling tasks are explicitly introduced, and their incompatibility is settled by our task-decouple mechanism, which improves the capability of predicting the location and size of acne lesions. Second, we propose the task-sequence mechanism, and execute offset and scaling sequentially to gain a more comprehensive insight into the dimensions of acne lesions. In addition, we build a high-quality acne detection dataset named ACNE-DET to verify the effectiveness of DSDH. Experiments on ACNE-DET and the public benchmark ACNE04 show that our method outperforms the previous sophisticated methods by significant margins. Our DSDH and ACNE-DET are pioneering works in acne detection, establishing the state-of-the-art architecture and benchmark, respectively. • The task-decouple mechanism alleviates the incompatibility between the offset and scaling tasks. • The task-sequence mechanism facilitates scaling by split bounding box refinement into two steps. • The ACNE-DET dataset surpasses the previous acne detection dataset for its high-quality. • Decoupled Sequential Detection Head outperforms the previous state-of-the-art methods. [ABSTRACT FROM AUTHOR]

The sequence method is an important approach to assess the baroreflex function, mainly because it is based on the spontaneous fluctuations of beat-by-beat arterial pressure (for example, systolic arterial pressure or SAP) and pulse interval (PI). However, some studies revealed that the baroreflex effectiveness index (BEI), calculated through the sequence method, shows an intriguing oscillatory pattern as function of the delay between SAP and PI. It has been hypothesized that this pattern is related to the respiratory influence on SAP and/or PI variability, limiting the SAP ramps to 3 or 4 beats of length. In this study, this hypothesis was tested by assessing the sequence method using raw (original) and filtered series. Results were contrasted to the well-established transfer function, estimated between SAP and PI. Continuous arterial pressure recordings were obtained from healthy rats (N = 61) and beat-by-beat series of SAP and PI were generated. Low-pass (LP) and high-pass (HP) filtered series of SAP and PI were created by filtering the original series with a cutoff frequency of 0.8 Hz. Original series were analyzed by either the sequence method or cross-spectral analysis (transfer function) at low- (LF) and high- (HF) frequency bands, while filtered series were evaluated only by the sequence method. Baroreflex sensitivity (BRS) and BEI of original series, calculated by sequence method, was highly (85–90%) determined by HP series, with no significant association between original and LP series. A high correlation (>0.7) was found between the BRS estimated from original series (sequence method) and HF band (transfer function), as well as for LP series (sequence method) and LF band (transfer function). These findings confirmed the hypothesis that the sequence method quantifies only the high-frequency components of the baroreflex, neglecting the low-frequency influences, such as the Mayer waves. Therefore, we propose using both the original and LP filtered time series for a broader assessment of the baroreflex function using the sequence method.

The sequence method is an important approach to assess the baroreflex function, mainly because it is based on the spontaneous fluctuations of beat-by-beat arterial pressure (for example, systolic arterial pressure or SAP) and pulse interval (PI). However, some studies revealed that the baroreflex effectiveness index (BEI), calculated through the sequence method, shows an intriguing oscillatory pattern as function of the delay between SAP and PI. It has been hypothesized that this pattern is related to the respiratory influence on SAP and/or PI variability, limiting the SAP ramps to 3 or 4 beats of length. In this study, this hypothesis was tested by assessing the sequence method using raw (original) and filtered series. Results were contrasted to the well-established transfer function, estimated between SAP and PI. Continuous arterial pressure recordings were obtained from healthy rats (N = 61) and beat-by-beat series of SAP and PI were generated. Low-pass (LP) and high-pass (HP) filtered series of SAP and PI were created by filtering the original series with a cutoff frequency of 0.8 Hz. Original series were analyzed by either the sequence method or cross-spectral analysis (transfer function) at low- (LF) and high- (HF) frequency bands, while filtered series were evaluated only by the sequence method. Baroreflex sensitivity (BRS) and BEI of original series, calculated by sequence method, was highly (85–90%) determined by HP series, with no significant association between original and LP series. A high correlation (>0.7) was found between the BRS estimated from original series (sequence method) and HF band (transfer function), as well as for LP series (sequence method) and LF band (transfer function). These findings confirmed the hypothesis that the sequence method quantifies only the high-frequency components of the baroreflex, neglecting the low-frequency influences, such as the Mayer waves. Therefore, we propose using both the original and LP filtered time series for a broader assessment of the baroreflex function using the sequence method. [ABSTRACT FROM AUTHOR]

High dietary sodium intake has been linked to alterations in neurally mediated cardiovascular function, but the effects of high sodium on cardiovagal baroreflex sensitivity (cBRS) in healthy adults are unknown. The purpose of this study was to determine whether high dietary sodium alters cBRS and heart rate variability (HRV) and whether acute intravenous sodium loading similarly alters cBRS and HRV. High dietary sodium (300 mmol/day, 7 days) was compared with low dietary sodium (20 mmol/day, 7 days; randomized) in 14 participants (38 ± 4 yr old, 23 ± 1 kg/m² body mass index, 7 women). Acute sodium loading was achieved via a 23-min intravenous hypertonic saline infusion (HSI) in 14 participants (22 ± 1 yr old, 23 ± 1 kg/m² body mass index, 7 women). During both protocols, participants were supine for 5 min during measurement of beat-to-beat blood pressure (photoplethysmography) and R-R interval (ECG). cBRS was evaluated using the sequence method. Root mean square of successive differences in R-R interval (RMSSD) was used as an index of HRV. Serum sodium (137.4 ± 0.7 vs. 139.9 ± 0.5 meq/l, P < 0.05), plasma osmolality (285 ± 1 vs. 289 ± 1 mosmol/kgH2O, P < 0.05), cBRS (18 ± 2 vs. 26 ± 3 ms/mmHg, P < 0.05), and RMSSD (62 ± 6 vs. 79 ± 10 ms, P < 0.05) were increased following high-sodium diet intake compared with low-sodium diet intake. HSI increased serum sodium (138.1 ± 0.4 vs. 141.1 ± 0.5 meq/l, P < 0.05) and plasma osmolality (286 ± 1 vs. 290 ± 1 mosmol/kgH2O, P < 0.05) but did not change cBRS (26 ± 5 vs. 25 ± 3 ms/mmHg, P = 0.73) and RMSSD (63 ± 9 vs. 63 ± 8 ms, P = 0.99). These data suggest that alterations in dietary sodium intake alter cBRS and HRV but that acute intravenous sodium loading does not alter these indexes of autonomic cardiovascular regulation. [ABSTRACT FROM AUTHOR]

This study tests the spontaneous sequence method for the evaluation of the cardiac, vasomotor, and myocardial branches of the baroreflex. Systolic blood pressure (SBP), interbeat interval (IBI), stroke volume (SV), preejection period (PEP), and total peripheral resistance (TPR) were continuously recorded in 33 physically active and 25 sedentary participants at rest and during a mental arithmetic task. Sequences of spontaneous covariation between SBP and IBI (for the cardiac branch), SV and PEP (for the myocardial branch), and TPR (for the vasomotor branch) were located. The slope of the regression line between values in the sequences produced an estimate of baroreflex sensitivity (BRS), and the proportion of progressive SBP changes that elicited reflex modulations yielded an estimate of baroreflex effectiveness (BEI). The active group showed greater BRS in all three branches than the sedentary group. Cardiac and vasomotor BEI decreased during the arithmetic task in the sedentary group but not in the active one. Only cardiac BRS decreased during the arithmetic task. In conclusion, the method appears appropriate for the simultaneous assessment of the three baroreflex branches. The assessment of the vascular branch of the baroreflex may have prognostic relevance in the development of hypertension or other cardiometabolic diseases. [ABSTRACT FROM AUTHOR]

Key points The integrity of the baroreflex control of sympathetic activity in heart failure (HF) remains under debate., We proposed the use of the sequence method to assess the baroreflex control of renal sympathetic nerve activity (RSNA)., The sequence method assesses the spontaneous arterial pressure (AP) fluctuations and their related changes in heart rate (or other efferent responses), providing the sensitivity and the effectiveness of the baroreflex. Effectiveness refers to the fraction of spontaneous AP changes that elicits baroreflex-mediated variations in the efferent response., Using three different approaches, we showed that the baroreflex sensitivity between AP and RSNA is not altered in early HF rats. However, the sequence method provided evidence that the effectiveness of baroreflex in changing RSNA in response to AP changes is markedly decreased in HF., The results help us better understand the baroreflex control of the sympathetic nerve activity., Abstract In heart failure (HF), the reflex control of the heart rate is known to be markedly impaired; however, the baroreceptor control of the sympathetic drive remains under debate. Applying the sequence method to a series of arterial pressure (AP) and renal sympathetic nerve activity (RSNA), we demonstrated a clear dysfunction in the baroreflex control of sympathetic activity in rats with early HF. We analysed the baroreflex control of the sympathetic drive using three different approaches: AP vs. RSNA curve, cross-spectral analysis and sequence method between AP and RSNA. The sequence method also provides the baroreflex effectiveness index (BEI), which represents the percentage of AP ramps that actually produce a reflex response. The methods were applied to control rats and rats with HF induced by myocardial infarction. None of the methods employed to assess the sympathetic baroreflex gain were able to detect any differences between the control and the HF group. However, rats with HF exhibited a lower BEI compared to the controls. Moreover, an optimum delay of 1 beat was observed, i.e. 1 beat is required for the RSNA to respond after AP changing, which corroborates with the findings related to the timing between these two variables. For delay 1, the BEI of the controls was 0.45 ± 0.03, whereas the BEI of rats with HF was 0.29 ± 0.09 ( P < 0.05). These data demonstrate that while the gain of the baroreflex is not affected in early HF, its effectiveness is markedly decreased. The analysis of the spontaneous changes in AP and RSNA using the sequence method provides novel insights into arterial baroreceptor reflex function. [ABSTRACT FROM AUTHOR]

The objective of this paper is to present some sufficient conditions for approximate controllability of semilinear fractional control system of order $${\alpha \in (1, 2]}$$ with infinite delay. The results are obtained by the theory of strongly continuous $${\alpha}$$ -order cosine family and sequence method. At the end, an example is given to illustrate the theory. [ABSTRACT FROM AUTHOR]

A decerebrate rattlesnake, Crotalus durissus, has previously been used as a model Squamate for cardiovascular studies. It enabled instrumentation for concomitant recordings of diverse variables that showed autonomic responses. However, to validate the preparation and its scope for use, it is necessary to assess how close its cardiovascular variables are to non-decerebrate snakes and the effectiveness of its autonomic responses. Similarly, it is important to analyze its recovery profile after instrumentation and observe if it maintains stability throughout the duration of experimental protocol. Here we have objectively assessed these points by comparing decerebrate preparations and non-decerebrate snakes, after the occlusive cannulation of the vertebral artery. We have assessed cardiovascular variables and the baroreflex to analyze the presence, magnitude and stability of complex autonomic-controlled parameters as indicators of autonomic nervous system (ANS) functionality. After instrumentation, mean heart rates were high but recovered to stable values within 24 h. Mean arterial pressure stabilized within 24 h in control snakes and 48 h in decerebrate preparations. After that, both parameters remained stable. The operational gain and effectiveness index of the baroreflex recovered within the first 6 h after instrumentation in both experimental groups. In addition, the baroreflex capacities and its limits were also equivalent between the groups. These experiments demonstrated that decerebrate preparations and inactive, non-decerebrate snakes showed comparable recovery profiles following anesthesia and cannulation, maintained similar values of cardiovascular variables during experimental manipulation and exhibited functional, ANS modulated reflexes. Accordingly, the present results attest the relevance of this decerebrate preparation for studies on cardiovascular modulation. [Display omitted] • A decerebrate rattlesnake preparation (DP) has been pointed out as relevant for cardiovascular studies. • DP and inactive, intact snakes (IS) have comparable recovery profiles following instrumentation. • DP and IS maintained similar values of cardiovascular variables. • DP has a functional ANS modulated reflexes. • DP baroreflex capacities and limits were equivalent to IS'. [ABSTRACT FROM AUTHOR]

Low baroreflex sensitivity (BRS) is associated with elevated cardiovascular risk. However, the evidence is based primarily on measurements of cardiac BRS. It cannot be assumed that cardiac or sympathetic BRS alone represent a true reflection of baroreflex control of blood pressure. The aim of this study was to examine the relationship between spontaneous sympathetic and cardiac BRS in healthy, young individuals. Continuous measurements of blood pressure, heart rate, and muscle sympathetic nerve activity (MSNA) were made under resting conditions in 50 healthy individuals (18-28 years). Sympathetic BRS was quantified by plotting MSNA burst incidence against diastolic pressure (sympathetic BRSinc), and by plotting total MSNA against diastolic pressure (sympathetic BRStotal). Cardiac BRS was quantified by plotting R-R interval against systolic pressure using the sequence method. Significant sympathetic BRSinc and cardiac BRS slopes were obtained for 42 participants. A significant positive correlation was found between sympathetic BRSinc and cardiac BRS (r = 0.31, P = 0.049). Among this group, significant sympathetic baroreflex slopes were obtained for 39 participants when plotting total MSNA against diastolic pressure. In this subset, a significant positive correlation was observed between sympathetic BRStotal and cardiac BRS (r = 0.40, P = 0.012). When males and females were assessed separately, these modest relationships only remained significant in females. Analysis by gender revealed correlations in the females between sympathetic BRSinc and cardiac BRS (r = 0.49, P = 0.062), and between sympathetic BRStotal and cardiac BRS (r = 0.57, P = 0.025). These findings suggest that gender interactions exist in baroreflex control of blood pressure, and that cardiac BRS is not appropriate for estimating overall baroreflex function in healthy, young populations. This relationship warrants investigation in aging and clinical populations. [ABSTRACT FROM AUTHOR]

INTRODUCTION: The dose-effect relationships between different levels of hypergravity (> +1.0 Gz) and steady-state hemodynamic parameters have been reported in several studies. However, little has been reported on the dose-effect relationship between hypergravity levels and estimates of autonomic circulatory regulation, such as heart rate variability, arterial pressure variability, and spontaneous cardiac baroreflex sensitivity. We investigated dose-effect relationships between hypergravity levels from +1.0 Gz to +2.0 Gz (Δ0.5 Gz) and autonomic circulatory regulation to test our hypothesis that autonomic circulatory regulation has a linear relationship with hypergravity levels. METHODS: Using a short-arm human centrifuge, 10 healthy seated men were subjected to+1.0Gz, +1.5 Gz, and +2.0 Gz hypergravity. We evaluated steady-state hemodynamic parameters and autonomic circulatory regulation indices. Heart rate variability, arterial pressure variability, and spontaneous cardiac baroreflex sensitivity between arterial pressure and R-R interval variabilities were assessed by spectral analysis, sequence analysis, and transfer function analysis. RESULTS: Steady-state heart rate, stroke volume, and sequence slope (indicating spontaneous cardiac baroreflex sensitivity in response to rapid changes In arterial pressure) showed linear correlations with increases in gravity (from +1.0 Gz to +2.0 Gz). On the other hand, steady-state cardiac output, steady-state systolic arterial pressure, and low-frequency power of diastolic arterial pressure (indicating peripheral vasomotor sympathetic activity) remained unchanged with gravity increases. CONCLUSION: Contrary to our hypothesis, the present study suggested that autonomic circulatory regulations show complex changes with hypergravity levels. Spontaneous cardiac baroreflex sensitivity reduces In a dose-dependent manner from +1.0 Gz to +2.0 Gz, whereas peripheral vasomotor sympathetic activity seems to be maintained. [ABSTRACT FROM AUTHOR]

Head-to-foot gravitational force > 1 G (+ Gz hypergravity) augments venous pooling in the lower body and reduces central blood volume during exposure, compared with 1 Gz. Central hypovolemia has been reported to reduce spontaneous cardiac baroreflex sensitivity. However, no investigations have examined spontaneous cardiac baroreflex sensitivity during exposure to sustained mild + Gz hypergravity. We therefore hypothesized that mild + Gz hypergravity would reduce spontaneous cardiac baroreflex sensitivity, compared with 1 Gz. To test this hypothesis, we examined spontaneous cardiac baroreflex sensitivity in 16 healthy men during exposure to mild + Gz hypergravity using a short-arm centrifuge. Beat-to-beat arterial blood pressure (tonometry) and R–R interval (electrocardiography) were obtained during 1 Gz and 1.5 Gz exposures. Spontaneous cardiac baroreflex sensitivity was assessed by sequence slope and transfer function gain. Stroke volume was calculated from the arterial pressure waveform using a three-element model. All indices of spontaneous cardiac baroreflex sensitivity decreased significantly (up slope: 18.6 ± 2.3 → 12.7 ± 1.6 ms/mm Hg, P < 0.001; down slope: 19.0 ± 2.5 → 13.2 ± 1.3 ms/mm Hg, P = 0.002; transfer function gain in low frequency: 14.4 ± 2.2 → 10.1 ± 1.1 ms/mm Hg, P = 0.004; transfer function gain in high frequency: 22.2 ± 7.5 → 12.4 ± 3.5 ms/mm Hg, P < 0.001). Stroke volume decreased significantly (88 ± 5 → 80 ± 6 ml, P = 0.025). Moreover, although systolic arterial pressure variability increased, R–R interval variability did not increase. These results suggest that even mild + Gz hypergravity reduces spontaneous cardiac baroreflex sensitivity, increasing the risk of cardiovascular disturbance during the exposure. [ABSTRACT FROM AUTHOR]

Abstract: Fibromyalgia (FM) is characterized by chronic non-inflammatory widespread pain (CWP) and changes in sympathetic function. In attempt to elucidate the pathophysiological mechanisms of FM we used a well-established CWP animal model. We aimed to evaluate changes in cardiac autonomic balance and baroreflex function in response to CWP induction in rats. CWP was induced by two injections of acidic saline (pH 4.0, n =8) five days apart into the left gastrocnemius muscle. Control animals were injected twice with normal saline (pH 7.2, n =6). One day after the second injection of acidic saline or normal saline, the animals had pulse interval (PI) and systolic arterial pressure (SAP) variability, and spontaneous baroreflex sensitivity (BRS) evaluated. After induction of CWP, there was an increase of power in the low frequency (LF) band of PI spectrum (12.75±1.04nu), a decrease in the high frequency (HF) band (87.25±1.04nu) and an increase of LF/HF ratio (0.16±0.01), when compared to control animals (7.83±1.13nu LF; 92.16±1.13nu HF; 0.08±0.01 LF/HF). In addition, there was an increase of power in the LF band of SAP spectrum (7.93±1.39mmHg2) when compared to control animals (2.97±0.61mmHg2). BRS was lower in acidic saline injected rats (0.59±0.06ms/mmHg) when compared to control animals (0.71±0.03ms/mmHg). Our results showed that induction of CWP in rats shifts cardiac sympathovagal balance towards sympathetic predominance and decreases BRS. These data corroborate findings in humans with FM. [Copyright &y& Elsevier]

The effect of emotional stress on the spontaneous baroreceptor reflex (sBRR) in freely moving rats was investigated. Six male Wistar rats equipped with an intra-arterial polyethylene catheter were exposed to a 2-min air-jet stress. For time course analysis of the sBRR response to stress, the records of systolic blood pressure (SBP) and pulse interval (PI) were divided into five regions: baseline (BASELINE), acute exposure to air-jet stress (STRESS), immediate recovery (IMMED. RECOVERY), remaining recovery (RECOVERY), and delayed response (DELAYED RESPONSE). In addition to sBRR sensitivity and effectiveness, we introduce the sequence coverage area and its median for evaluation of the sBRR operating range and set point. During exposure to STRESS and IMMED. RECOVERY, sBRR sensitivity was preserved, its effectiveness was decreased, its operating range was enlarged, and the set point was shifted towards higher SBP and lower PI values. According to the joint symbolic dynamics analysis, the SBP and PI relationship became less predictable hence more prone to respond to stress. In RECOVERY the parameters regained baseline values and DELAYED RESPONSE occurred during which re-setting of sBRR was noted. It follows that emotional stress modulates sBRR differentially during the time course of stress and recovery, affecting both linearity and unpredictability of the BP and PI relationship. [ABSTRACT FROM AUTHOR]

In this paper we improve the result obtained by Chen and Qi in 2005 about the inequalities for the Wallis ratio. [ABSTRACT FROM AUTHOR]

Assessment of baroreceptor reflex sensitivity (BRS) in the ovine fetus provides insight into autonomic cardiovascular regulation. Currently, assessment of BRS relies on vasoactive drugs, but this approach is limited by feasibility issues and by the nonphysiologic nature of the stimulus. Thus we aimed to validate the method of spontaneous BRS assessment against the reference method of using vasoactive drugs in preterm (0.76 gestation, n = 16) and near-term (0.86 gestation, n = 16) chronically instrumented ovine fetuses. The BRS measures derived from the spontaneous and reference methods correlated at both gestational ages (R = 0.67 ± 0.03). The sequence method of spontaneous BRS measures also correlated both to the root mean square of standard deviations (RMSSD), which is a measure of fetal heart rate variability reflecting vagal modulation (R = 0.69 ± 0.03), and to fetal body weight (R = 0.65 ± 0.03), which is a surrogate for growth trajectory of each fetus. The methodology presented may aid in developing new models to study BRS and cardiovascular control in ovine fetus in the last trimester of pregnancy. [ABSTRACT FROM AUTHOR]

Abstract: Spontaneous baroreflex function can be altered by acute changes in central blood volume. Both a reduction in spontaneous baroreflex function at central hypovolemia and augmentation at hypervolemia suggest a dose–effect relationship between central blood volume and spontaneous baroreflex function. However, this relationship has not been quantified over stepwise widespread changes in central blood volume. Twelve individuals underwent central hypovolemia at two levels of lower body negative pressure (LBNP) (−15 mm Hg, LBNP15; −30 mm Hg, LBNP30) and hypervolemia with two discrete infusions of normal saline (NS) (15 ml·kg−1, NS15; total 30 ml·kg−1, NS30). Spontaneous baroreflex function was assessed using transfer function analysis and the sequence method between blood pressure and R–R interval. Both central venous pressure (−0.6–7.9 mm Hg) and left ventricular end-diastolic volume (72.4–133.1 ml) decreased during LBNP and increased after saline infusion. Both spontaneous baroreflex indices of high-frequency transfer function gain (LBNP30, 17.4±3.2; LBNP15, 22.3±3.8; baseline, 25.6±4.1; NS15, 28.5±4.2 ms·mm Hg−1, ANOVA P =0.001) and of the sequence slope (LBNP30, 14.4±2.2; LBNP15, 17.2±2.5; baseline, 20.5±2.8; NS15, 24.5±3.1 ms·mm Hg−1, ANOVA P =0.001) increased stepwise from hypovolemia of LBNP30 to hypervolemia of NS15. However, these indices were lower at NS30 (high-frequency transfer function gain, 22.0±2.2 ms·mm Hg−1, post-hoc P =0.071; sequence slope, 17.7±1.7 ms·mm Hg− 1, post-hoc P <0.05) than NS15 during hypervolemia. These results indicated that the relationship between central blood volume and spontaneous baroreflex function is apparently bell-shaped, with maximal augmentation at moderate hypervolemia. [Copyright &y& Elsevier]

Braga VA, Burmeister MA, Sharma RV, Davisson RL. Cardiovascular responses to peripheral chemoreflex activation and comparison of different methods to evaluate baroreflex gain in conscious mice using telemetry. Am J Physiol Regul Integr Comp Physiol 295: Ri 168-RI 174, 2008. First published July 30, 2008; doi: 10.1 152/ajpregu.90375.2008.Peripheral chemoreceptors located in the carotid bodies are the primary sensors of systemic hypoxia. Although the pattern of responses elicited by peripheral chemoreceptor activation is well established in rats, lambs, and rabbits, the cardiovascular responses to peripheral chemoreflex activation in conscious mice have not been delineated. Here we report that stimulation of peripheral chemoreceptors by potassium cyanide (KCN) in conscious mice elicits a unique biphasic response in blood pressure that is characterized by an initial and robust rise followed by a decrease in blood pressure, which is accompanied by a marked reduction in heart rate. The depressor and bradycardic responses to KCN were abolished by muscarinic receptor blockade with atropine, and the pressor response was abolished by ci-adrenergic receptor blockade with prazosin, suggesting that vagal and sympathetic drive to the heart and sympathetic drive to the vasculature mediate these cardiovascular responses. These studies characterized the chemoreflex in conscious mice and established the reliability of using them for studying hypoxia-related diseases such as obstructive sleep apnea. In another series of experiments, two methods for analyzing baroreflex sensitivity were compared: the classical pharmacological approach using phenylephrine and sodium nitroprusside (i.e., the Oxford technique) or the sequence method for analyzing spontaneous baroreflex activity. Our findings indicate that both methods are reliable, and the sequence method certainly has its benefits as a predictive tool in the context of long-term noninvasive studies using telemetry. However, for absolute determination of barorefiex function, analysis of spontaneous baroreflex activity should be complemented by the classical pharmacological method. [ABSTRACT FROM AUTHOR]

Abstract: While experimental baroreceptor stimulation is known to elicit hypoalgesia in healthy individuals, the impact of spontaneous baroreflex sensitivity (BRS) on acute pain responses is not known. We tested for associations between BRS and pain responses in healthy individuals, whether these associations are altered in chronic low back pain (CLBP), and the role of alpha-2 adrenergic (ADRA2) mechanisms in these effects. Twenty-five healthy controls and 21 CLBP subjects completed three acute pain tasks after receiving placebo or an intravenous ADRA2 antagonist (yohimbine hydrochloride, 0.4mg/kg) across two sessions in counterbalanced order. Resting pre-drug spontaneous BRS was assessed using the sequence method. CLBP subjects displayed lower resting BRSDown than controls (p <.05). Drug×BRSDown interactions indicated that significant BRS-related hypoalgesia on thermal pain threshold and tolerance was eliminated with yohimbine (p’s<.05). Subject Type×BRSUp interactions on finger pressure (MPQ-Sensory) and ischemic tasks (MPQ-Sensory, pain threshold, intra-task numeric intensity ratings) indicated that inverse BRS/pain associations in controls (p’s<.05) were absent in CLBP subjects. Subject Type×Drug×BRSDown interactions on finger pressure MPQ-Sensory and intra-task numeric intensity ratings (p’s<.05) indicated that for controls, yohimbine attenuated the significant inverse BRS/pain sensitivity associations noted under placebo. In contrast, CLBP subjects displayed a nonsignificant positive BRS/pain association under placebo, with yohimbine producing an inverse association similar to controls (significant for MPQ-Sensory). Results suggest presence of spontaneous BRS-related hypoalgesia in healthy individuals that is partially mediated by ADRA2 mechanisms, and that CLBP blunts BRS-related hypoalgesia. As a group, the CLBP subjects do not manifest baroreceptor-induced antinociception. [Copyright &y& Elsevier]

Background: Baroreflex sensitivity assessments have been considered to be important to evaluate cardiac autonomic neuropathy. The phenylephrine method, Valsalva maneuver or sequence method at rest caused several problems. We evaluated the usefulness of the sequence method during deep respiration. Method: Baroreflex sensitivity was evaluated in 20 normal volunteers and 50 patients with Parkinson’s disease. R–R intervals and systolic blood pressures were obtained by electrocardiogram and tonometry using a continuous blood pressure monitoring system. The sequence method is an evaluation of baroreflex sensitivity using sequences of 3 or more consecutive beats for 4 min. Baroreflex sensitivity was also assessed by the Valsalva maneuver at 5 beats before the peak systolic blood pressure of phase IV. The slope of the linear interrelationship between systolic blood pressure and the following R–R interval, i.e. baroreflex sensitivity (ms/mm Hg), was calculated with a correlation coefficient greater than 0.8. Result: The mean value of baroreflex sensitivity obtained by the Valsalva maneuver was 7.91 in normal volunteers and 5.35 in patients with Parkinson’s disease; the one obtained by the sequence method at rest was 9.10 in normal volunteers and 8.42 in patients with Parkinson’s disease, and the one obtained by the sequence method during deep respiration was 10.23 in normal volunteers and 6.73 in patients with Parkinson’s disease. In some cases with Parkinson’s disease, baroreflex sensitivities could not be found, whereas in all patients with Parkinson’s disease, the sequence method during deep respiration could be used for evaluations. Significant correlations were found among the baroreflex sensitivities obtained by the Valsalva maneuver, and the sequence method at rest or during deep respiration in normal volunteers and patients with Parkinson’s disease. Conclusions: The baroreflex sensitivity obtained by the sequence method during deep respiration could be investigated noninvasively in all cases with PD, being thus a useful method for clinical evaluation of baroreflex sensitivity.Copyright © 2003 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]