scholarly journals Physiological responses to gravity in an insect

2020 ◽  
Vol 117 (4) ◽  
pp. 2180-2186
Author(s):  
Jon F. Harrison ◽  
Khaled Adjerid ◽  
Anelia Kassi ◽  
C. Jaco Klok ◽  
John M. VandenBrooks ◽  
...  
Keyword(s):  
Blood Flow ◽  
Body Position ◽  
Small Body ◽  
Ventilation Rate ◽  
Body Orientation ◽  
Terrestrial Vertebrates ◽  
X Ray Imaging ◽  
Technical Measurement ◽  
Gravity Effects ◽  
Experience Effects

Gravity is one of the most ubiquitous environmental effects on living systems: Cellular and organismal responses to gravity are of central importance to understanding the physiological function of organisms, especially eukaryotes. Gravity has been demonstrated to have strong effects on the closed cardiovascular systems of terrestrial vertebrates, with rapidly responding neural reflexes ensuring proper blood flow despite changes in posture. Invertebrates possess open circulatory systems, which could provide fewer mechanisms to restrict gravity effects on blood flow, suggesting that these species also experience effects of gravity on blood pressure and distribution. However, whether gravity affects the open circulatory systems of invertebrates is unknown, partly due to technical measurement issues associated with small body size. Here we used X-ray imaging, radio-tracing of hemolymph, and micropressure measurements in the American grasshopper, Schistocerca americana, to assess responses to body orientation. Our results show that during changes in body orientation, gravity causes large changes in blood and air distribution, and that body position affects ventilation rate. Remarkably, we also found that insects show similar heart rate responses to body position as vertebrates, and contrasting with the classic understanding of open circulatory systems, have flexible valving systems between thorax and abdomen that can separate pressures. Gravitational effects on invertebrate cardiovascular and respiratory systems are likely to be widely distributed among invertebrates and to have broad influence on morphological and physiological evolution.

Sympathetic modulation of blood flow and O2 uptake in rhythmically contracting human forearm muscles

1992 ◽  
Vol 263 (4) ◽  
pp. H1078-H1083 ◽  
Author(s):  
M. J. Joyner ◽  
L. A. Nauss ◽  
M. A. Warner ◽  
D. O. Warner
Keyword(s):  
Blood Flow ◽  
Body Position ◽  
Maximum Voluntary Contraction ◽  
Sympathetic Nerves ◽  
Work Load ◽  
Voluntary Contraction ◽  
Sympathetic Block ◽  
O2 Uptake ◽  
Fick Principle ◽  
Rhythmic Exercise

This study tested the effects of sympathetically mediated changes in blood flow to active muscles on muscle O2 uptake (VO2) in humans. Four minutes of graded (15-80% of maximum voluntary contraction, MVC) rhythmic handgrip exercise were performed. Forearm blood flow (FBF) (plethysmography) and deep vein O2 saturation were measured each minute. Forearm O2 uptake was calculated using the Fick principle. In protocol 1, exercise was performed while supine and again while upright to augment sympathetic outflow to the active muscles. Standing reduced FBF at rest from 3.6 to 2.2 ml.100 ml-1.min-1 (P < 0.05). During light exercise (15-40% MVC) FBF was unaffected by body position. Standing reduced FBF (P < 0.05) from 36.0 to 25.2 ml.100 ml-1.min-1 and forearm VO2 from 38.2 to 28.1 ml.kg-1.min-1 during the final work load. In protocol 2, exercise was performed while supine before and after local anesthetic block of the sympathetic nerves to the forearm. Sympathetic block increased FBF at rest from 3.1 to 8.9 ml.100 ml-1.min-1 (P < 0.05), and FBF was higher during all work loads At 70-80% of MVC sympathetic block increased FBF from 35.4 to 50.7 ml.100 ml-1.min-1 (P < 0.05), and forearm VO2 from 45.5 to 54.2 ml.kg-1.min-1 (P < 0.05). These results suggest that in humans sympathetic nerves modulate blood flow to active muscles during light and heavy rhythmic exercise and that this restraint of flow can limit O2 uptake in muscles performing heavy rhythmic exercise.

Abstract 114: Effect of Body Position on Intracranial Pressure and Carotid Blood Flow During Extracorporeal Cardiopulmonary Resuscitation

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_4) ◽  
Author(s):  
Yaël Levy ◽  
Rocio Fernandez ◽  
Fanny Lidouren ◽  
Matthias Kohlhauer ◽  
Lionel Lamhaut ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cardiac Arrest ◽  
Intracranial Pressure ◽  
Cardiopulmonary Resuscitation ◽  
Body Position ◽  
Spontaneous Circulation ◽  
Systemic Hemodynamics ◽  
Body Tilt ◽  
Whole Body ◽  
Extracorporeal Cardiopulmonary Resuscitation

Introduction: Extracorporeal cardiopulmonary resuscitation (E-CPR) using extracorporeal membrane oxygenation (ECMO) is widely proposed for the treatment of refractory cardiac arrest. Hypothesis: Since cerebral autoregulation is altered in such conditions, body position may modify hemodynamics during ECPR. Our goal was to determine whether a whole body tilt-up challenge (TUC) could lower intracranial pressure (ICP) as previously shown with conventional CPR, without deteriorating cerebral blood flow (CBF). Methods: Pigs were anesthetized and instrumented for the continuous evaluation of CBF, ICP and systemic hemodynamics. After 15 min of untreated ventricular fibrillation they were treated with 30 min of E-CPR followed by sequential defibrillation shocks until resumption of spontaneous circulation (ROSC). ECMO was continued after ROSC to target a mean arterial pressure (MAP) >60 mmHg. Animals were maintained in the flat position (FP) throughout protocol, except during a 2 min TUC of the whole body (+30°) at baseline, during E-CPR and after-ROSC. Results: Four animals received the entire procedure and ROSC was obtained in 3/4. After cardiac arrest, E-CPR was delivered at 29±2 ml/kg/min to maintain a MAP of 57±8 mmHg in the FP. CBF was 28% of baseline and ICP remain stable (12±1 vs 13±1 mmHg during ECPR vs baseline, respectively). Under baseline pre-arrest conditions TUC resulted in a significant decrease in ICP (-63±7%) and CBF (-21±3%) versus the FP, with no significant effect on systemic hemodynamics. During E-CPR and after ROSC, TUC markedly reduced ICP but CBF remained unchanged vs the FP (Figure). Conclusion: During E-CPR whole body TUC reduced ICP without lowering CBF compared with E-CPR flat. Additional investigations with prolonged TUC and selective head and thorax elevation during E-CPR are warranted.

scholarly journals Supine, prone, right and left gravitational effects on human pulmonary circulation

2019 ◽  
Vol 21 (1) ◽  
Author(s):  
Björn Wieslander ◽  
Joao Génio Ramos ◽  
Malin Ax ◽  
Johan Petersson ◽  
Martin Ugander
Keyword(s):  
Blood Flow ◽  
Intensive Care ◽  
Blood Volume ◽  
Pulmonary Blood Flow ◽  
Body Position ◽  
Dependent Lung ◽  
Pulmonary Hemodynamics ◽  
Gravitational Effects ◽  
Volume Variation ◽  
Arterial Blood

Abstract Background Body position can be optimized for pulmonary ventilation/perfusion matching during surgery and intensive care. However, positional effects upon distribution of pulmonary blood flow and vascular distensibility measured as the pulmonary blood volume variation have not been quantitatively characterized. In order to explore the potential clinical utility of body position as a modulator of pulmonary hemodynamics, we aimed to characterize gravitational effects upon distribution of pulmonary blood flow, pulmonary vascular distension, and pulmonary vascular distensibility. Methods Healthy subjects (n = 10) underwent phase contrast cardiovascular magnetic resonance (CMR) pulmonary artery and vein flow measurements in the supine, prone, and right/left lateral decubitus positions. For each lung, blood volume variation was calculated by subtracting venous from arterial flow per time frame. Results Body position did not change cardiac output (p = 0.84). There was no difference in blood flow between the superior and inferior pulmonary veins in the supine (p = 0.92) or prone body positions (p = 0.43). Compared to supine, pulmonary blood flow increased to the dependent lung in the lateral positions (16–33%, p = 0.002 for both). Venous but not arterial cross-sectional vessel area increased in both lungs when dependent compared to when non-dependent in the lateral positions (22–27%, p ≤ 0.01 for both). In contrast, compared to supine, distensibility increased in the non-dependent lung in the lateral positions (68–113%, p = 0.002 for both). Conclusions CMR demonstrates that in the lateral position, there is a shift in blood flow distribution, and venous but not arterial blood volume, from the non-dependent to the dependent lung. The non-dependent lung has a sizable pulmonary vascular distensibility reserve, possibly related to left atrial pressure. These results support the physiological basis for positioning patients with unilateral pulmonary pathology with the “good lung down” in the context of intensive care. Future studies are warranted to evaluate the diagnostic potential of these physiological insights into pulmonary hemodynamics, particularly in the context of non-invasively characterizing pulmonary hypertension.

Evidence for a dorso-medial parietal system involved in mental transformations of the body

1996 ◽  
Vol 76 (3) ◽  
pp. 2042-2048 ◽  
Author(s):  
E. Bonda ◽  
S. Frey ◽  
M. Petrides
Keyword(s):  
Blood Flow ◽  
Parietal Cortex ◽  
Human Subjects ◽  
Body Position ◽  
The Body ◽  
Right Hand ◽  
Positron Emission ◽  
Superior Parietal Cortex ◽  
The Right ◽  
Mental Transformations

1. The neural systems underlying body-space mental representation were studied by measuring changes in regional cerebral blood flow (CBF) with positron emission tomography in human subjects. 2. The experimental paradigm involved identification of the left or the right hand of the experimenter presented in different orientations or the palm of the subject's right hand. The subjects were required to decide whether it was the left or the right hand that was presented. To perform this task, the subjects had to move mentally the position of their own arm to adopt that of the experimenter's arm. The control condition involved the same type of tactual stimulation without the requirement of mental transformations of the subject's body position. The distribution of CBF was measured by means of the water bolus H2(15)O methodology during the performance of these tasks. 3. Comparison of the distribution of CBF between the experimental and control tasks was carried out to reveal changes specific to the mental transformations of the subject's body. Significant blood flow increases were observed in the caudal superior parietal cortex, including the intraparietal sulcus, and the adjacent medial parietal cortex. These findings demonstrated that there is a dorsomedially directed parietal system underlying mental transformations of the body in interactive relation with external space.

Insufflation profile and body position influence portal venous blood flow during pneumoperitoneum

2003 ◽  
Vol 17 (12) ◽  
pp. 1951-1957 ◽  
Author(s):  
C. -G. Schmedt ◽  
O. Heupel ◽  
V. Riemer ◽  
C. N. Gutt
Keyword(s):  
Blood Flow ◽  
Body Position ◽  
Venous Blood ◽  
Venous Blood Flow ◽  
Portal Venous Blood Flow ◽  
Portal Venous Blood

scholarly journals Hummingbirds control turning velocity using body orientation and turning radius using asymmetrical wingbeat kinematics

2016 ◽  
Vol 13 (116) ◽  
pp. 20160110 ◽  
Author(s):  
Tyson J. G. Read ◽  
Paolo S. Segre ◽  
Kevin M. Middleton ◽  
Douglas L. Altshuler
Keyword(s):  
Body Position ◽  
The Body ◽  
Body Orientation ◽  
Total Force ◽  
Aerodynamic Forces ◽  
Turning Radius ◽  
Multiple Species ◽  
Dependent Mechanism

Turning in flight requires reorientation of force, which birds, bats and insects accomplish either by shifting body position and total force in concert or by using left–right asymmetries in wingbeat kinematics. Although both mechanisms have been observed in multiple species, it is currently unknown how each is used to control changes in trajectory. We addressed this problem by measuring body and wingbeat kinematics as hummingbirds tracked a revolving feeder, and estimating aerodynamic forces using a quasi-steady model. During arcing turns, hummingbirds symmetrically banked the stroke plane of both wings, and the body, into turns, supporting a body-dependent mechanism. However, several wingbeat asymmetries were present during turning, including a higher and flatter outer wingtip path and a lower more deviated inner wingtip path. A quasi-steady analysis of arcing turns performed with different trajectories revealed that changes in radius were associated with asymmetrical kinematics and forces, and changes in velocity were associated with symmetrical kinematics and forces. Collectively, our results indicate that both body-dependent and -independent force orientation mechanisms are available to hummingbirds, and that these kinematic strategies are used to meet the separate aerodynamic challenges posed by changes in velocity and turning radius.

Improved Computational Fluid Dynamic Simulations of Blood Flow in Membrane Oxygenators from X-ray Imaging

2013 ◽  
Vol 41 (10) ◽  
pp. 2088-2098 ◽  
Author(s):  
Cameron C. Jones ◽  
James M. McDonough ◽  
Patrizio Capasso ◽  
Dongfang Wang ◽  
Kyle S. Rosenstein ◽  
...  
Keyword(s):  
Blood Flow ◽  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Dynamic Simulations ◽  
X Ray ◽  
X Ray Imaging ◽  
Membrane Oxygenators

scholarly journals About interrelation of intracranial pressure and cerebral blood flow when positioning at patients with acute brain damage

2019 ◽  
Vol 18 (4) ◽  
pp. 4-10
Author(s):  
V. I. Gorbachev ◽  
N. V. Bragina ◽  
S. V. Gorbachev
Keyword(s):  
Blood Flow ◽  
Intensive Care ◽  
Cerebral Blood Flow ◽  
Intracranial Pressure ◽  
Brain Damage ◽  
Perfusion Pressure ◽  
Body Position ◽  
Slope Angle ◽  
Cerebral Damage ◽  
Bed Position

Changing of «head – of – the bed» position is a routine method of positioning the patient to correct intracranial hypertension. In intensive care units, the «head – of – the bed» position vary from 0 to 60 °, and there is no consensus on which of them is most effective. The review of the major publications in the domestic and foreign literature about the problem of interrelation between positioning and changes of intracranial pressure, system and cerebral hemodynamic in patients with brain damage including databases eLibrary, PubMed, with the key words «hyperthermia», « positioning», «slope angle of the head of bed», «intracranial pressure», «cerebral perfusion pressure», «cerebral blood flow», «brain damage», and their combination. It is believed that the majority of patients with cerebral damage, regardless of the etiological factor, is preferable to 15–30° «head – of – the bed» position. In some cases manipulation of the head of the bed can lead to irreversible ischemic damage, due to the reduction of system and perfusion pressure, and cerebral blood flow. Thus, the selection of the optimal body position in acute cerebral pathology remains a debated issue. In this way, individual tactics of positioning in patients with cerebral damage allows choosing the correct intensive care and improving the treatment results.

scholarly journals Function of the heterocercal tail in sharks: quantitative wake dynamics during steady horizontal swimming and vertical maneuvering

2002 ◽  
Vol 205 (16) ◽  
pp. 2365-2374 ◽  
Author(s):  
C. D. Wilga ◽  
G. V. Lauder
Keyword(s):  
Body Position ◽  
Classical Model ◽  
Center Of Mass ◽  
Critical Role ◽  
Force Balance ◽  
Body Orientation ◽  
Vortex Rings ◽  
Direct Reaction ◽  
Body Angle ◽  
Tail Function

SUMMARYThe function of the heterocercal tail in sharks has long been debated in the literature. Previous kinematic data have supported the classical theory which proposes that the beating of the heterocercal caudal fin during steady horizontal locomotion pushes posteroventrally on the water, generating a reactive force directed anterodorsally and causing rotation around the center of mass. An alternative model suggests that the heterocercal shark tail functions to direct reaction forces through the center of mass. In this paper,we quantify the function of the tail in two species of shark and compare shark tail function with previous hydrodynamic data on the heterocercal tail of sturgeon Acipenser transmontanus. To address the two models of shark heterocercal tail function, we applied the technique of digital particle image velocimetry (DPIV) to quantify the wake of two species of shark swimming in a flow tank. Both steady horizontal locomotion and vertical maneuvering were analyzed. We used DPIV with both horizontal and vertical light sheet orientations to quantify patterns of wake velocity and vorticity behind the heterocercal tail of leopard sharks (Triakis semifasciata) and bamboo sharks (Chiloscyllium punctatum) swimming at 1.0Ls-1, where L is total body length. Two synchronized high-speed video cameras allowed simultaneous measurement of shark body position and wake structure. We measured the orientation of tail vortices shed into the wake and the orientation of the central jet through the core of these vortices relative to body orientation. Analysis of flow geometry indicates that the tail of both leopard and bamboo shark generates strongly tilted vortex rings with a mean jet angle of approximately 30 ° below horizontal during steady horizontal swimming. The corresponding angle of the reaction force is much greater than body angle (mean 11 °) and the angle of the path of motion of the center of mass (mean approximately 0 °), thus strongly supporting the classical model of heterocercal tail function for steady horizontal locomotion. Vortex jet angle varies significantly with body angle changes during vertical maneuvering, but sharks show no evidence of active reorientation of jet angle relative to body angle, as was seen in a previous study on the function of sturgeon tail. Vortex jet orientation is significantly more inclined than the relatively horizontal jet generated by sturgeon tail vortex rings, demonstrating substantial differences in function in the heterocercal tails of sharks and sturgeon.We present a summary of forces on a swimming shark integrating data obtained here on the tail with previous data on pectoral fin and body function. Body orientation plays a critical role in the overall force balance and compensates for torques generated by the tail. The pectoral fins do not generate lift during steady horizontal locomotion, but play an important hydrodynamic role during vertical maneuvering.

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