Isometric Force Exaggeration in Simulated Weightlessness by Water Immersion: Role of Visual Feedback

Endothelium-derived nitric oxide (EDNO) modulates fetal pulmonary vasoactivity. The role of EDNO in regulation of vasomotor tone in fetal pulmonary arteries vs. that in veins is not known. We have investigated the role of EDNO in the responses of pulmonary arteries and veins of full-term fetal lambs. Fourth-generation pulmonary arterial and venous rings were suspended in organ chambers filled with modified Krebs-Ringer bicarbonate solution (95% O2-5% CO2 at 37 degrees C), and their isometric force was measured. N omega-nitro-L-arginine had no effect on the resting tension of pulmonary arteries with endothelium but caused contraction of pulmonary veins with endothelium. The basal level of intracellular guanosine 3',5'-cyclic monophosphate (cGMP) of pulmonary veins with endothelium was higher than that of arteries with endothelium. In pulmonary arteries, bradykinin, but not acetylcholine, induced endothelium-dependent relaxation and an increase in cGMP content. In pulmonary veins, acetylcholine, but not bradykinin, induced endothelium-dependent relaxation and an increase in cGMP content. Agonist-induced maximal relaxation and increases in cGMP content were smaller in pulmonary arteries than in veins. All these endothelium-dependent responses were abolished by N omega-nitro-L-arginine. In tissues without endothelium, nitric oxide induced significantly less relaxation and less increase in cGMP content in pulmonary arteries than in pulmonary veins. All vessels relaxed similarly to 8-bromoguanosine 3',5'-cyclic monophosphate. Our data suggest that the role of EDNO in modulating tone differs between pulmonary arteries and veins in full-term fetal lambs.(ABSTRACT TRUNCATED AT 250 WORDS)

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Role of the Visual Feedback for Stabilization of Vertical Human Posture during Induced Body Oscillations

Motor Control ◽

10.1007/978-1-4615-7508-5_22 ◽

1987 ◽

pp. 129-134

Author(s):

G. N. Gantchev ◽

P. Gatev ◽

N. Tankov ◽

N. Draganova ◽

S. Dunev ◽

...

Keyword(s):

Visual Feedback ◽

Human Posture

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The role of ANP in the reduction of plasma volume during graded exercise with water immersion

Pathophysiology ◽

10.1016/0928-4680(94)90951-2 ◽

1994 ◽

Vol 1 ◽

pp. 469

Author(s):

K. Nagashima ◽

H. Nose ◽

T. Yoshida ◽

T. Kawabata ◽

T. Morimoto

Keyword(s):

Plasma Volume ◽

Water Immersion ◽

Graded Exercise

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Visuomotor tracking with the lower extremity: the role of visual feedback in task performance

Brain Stimulation ◽

10.1016/j.brs.2008.06.169 ◽

2008 ◽

Vol 1 (3) ◽

pp. 311

Author(s):

S. Hotz-Boendermaker ◽

J. Petersen ◽

M. Laubacher ◽

M.-C. Hepp-Reymond ◽

M. Schubert

Keyword(s):

Lower Extremity ◽

Task Performance ◽

Visual Feedback ◽

Visuomotor Tracking

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Effects of vasopressin administration on diuresis of water immersion in normal humans

Journal of Applied Physiology ◽

10.1152/jappl.1981.51.6.1384 ◽

1981 ◽

Vol 51 (6) ◽

pp. 1384-1387 ◽

Cited By ~ 13

Author(s):

M. Epstein ◽

A. G. DeNunzio ◽

R. D. Loutzenhiser

Keyword(s):

Antidiuretic Hormone ◽

Flow Rate ◽

Water Immersion ◽

Normal Subjects ◽

Urinary Flow Rate ◽

Urinary Flow ◽

Relative Role ◽

Normal Humans

Although previous studies have demonstrated that water immersion to the neck (NI) results in a significant diuresis, the mechanisms are incompletely delineated. Because recent studies in our laboratory have demonstrated that NI is associated with a suppression of antidiuretic hormone (ADH), it is possible that such a suppression mediates the encountered diuresis. The present study was undertaken to assess more directly the relative role of ADH suppression by determining the effects of vasopressin administration. Six hydrated normal subjects were studied on two occasions while undergoing 6 h of NI. During the second NI study, aqueous vasopressin (20 mU/h) was infused for the initial 4 h of study (NI + vasopressin). NI resulted in a significant increase in urinary flow rate beginning during hour 1 and persisting throughout NI. In contrast, during NI + vasopressin, the anticipated diuresis was abolished throughout the 4 h of vasopressin administration. Cessation of vasopressin administration during the final 2 h of NI + vasopressin resulted in a marked and prompt diuresis. The present observations are consistent with the formulation that ADH suppression participates importantly in mediating the diuresis of NI in hydrated normal subjects.

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Atrial natriuretic factor and renal function during head-out water immersion in conscious dogs

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1986.251.5.r1000 ◽

1986 ◽

Vol 251 (5) ◽

pp. R1000-R1004

Author(s):

K. Miki ◽

G. Hajduczok ◽

M. R. Klocke ◽

J. A. Krasney ◽

S. K. Hong ◽

...

Keyword(s):

Sodium Excretion ◽

Atrial Natriuretic Factor ◽

Time Course ◽

Water Immersion ◽

Base Line ◽

Peripheral Tissues ◽

Natriuretic Factor ◽

Peak Value ◽

Atrial Natriuretic

The potential role of atrial natriuretic factor (ANF) in the renal response to head-out water immersion (WI) was studied. Five female mongrel dogs, trained to stand for 100 min in air followed by 100 min of thermoneutral WI at 37 degrees C or 200 min in air (timed control, TC), were chronically instrumented with arterial and venous catheters. The animals were hydrated with a volume of 0.45% NaCl solution equivalent to 2% of their body weight. Prehydration levels of arterial ANF were 243 +/- 15 (SE), and venous ANF levels were 211 +/- 21 pg/ml. WI resulted in an increase in urine flow from 0.7 +/- 0.1 ml/min to a peak flow of 2.2 +/- 0.3 ml/min (P less than 0.05). On immersion, plasma venous and arterial ANF levels increased significantly by 29 and 21% from the preimmersion values of 183 +/- 14 and 222 +/- 20 pg/ml, respectively. The arterial-venous difference for plasma ANF was maintained at 35 +/- 14 pg/ml (P less than 0.05) during WI; therefore venous sampling may suffice as a measure of circulating ANF levels. Sodium excretion increased linearly during WI to a peak value of 228 +/- 32 mu eq/min from a base line of 52 +/- 12 mu eq/min (P less than 0.05). These data indicate that peripheral tissues extract ANF and that WI is a physiological stimulus for the release of ANF. However, the time course and magnitude of the changes in plasma ANF and urine sodium excretion during WI are not comparable, and other mechanisms are likely responsible for the WI natriuresis.(ABSTRACT TRUNCATED AT 250 WORDS)

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The Role of Online Visual Feedback for the Control of Target-Directed and Allocentric Hand Movements

Journal of Neurophysiology ◽

10.1152/jn.00743.2010 ◽

2011 ◽

Vol 105 (2) ◽

pp. 846-859 ◽

Cited By ~ 6

Author(s):

Lore Thaler ◽

Melvyn A. Goodale

Keyword(s):

Visual Feedback ◽

Visual Information ◽

Sensory Feedback ◽

Sensory Information ◽

Movement Control ◽

Sensorimotor Control ◽

Hand Movements ◽

Cast Doubt ◽

Target Locations

Studies that have investigated how sensory feedback about the moving hand is used to control hand movements have relied on paradigms such as pointing or reaching that require subjects to acquire target locations. In the context of these target-directed tasks, it has been found repeatedly that the human sensory-motor system relies heavily on visual feedback to control the ongoing movement. This finding has been formalized within the framework of statistical optimality according to which different sources of sensory feedback are combined such as to minimize variance in sensory information during movement control. Importantly, however, many hand movements that people perform every day are not target-directed, but based on allocentric (object-centered) visual information. Examples of allocentric movements are gesture imitation, drawing, or copying. Here we tested if visual feedback about the moving hand is used in the same way to control target-directed and allocentric hand movements. The results show that visual feedback is used significantly more to reduce movement scatter in the target-directed as compared with the allocentric movement task. Furthermore, we found that differences in the use of visual feedback between target-directed and allocentric hand movements cannot be explained based on differences in uncertainty about the movement goal. We conclude that the role played by visual feedback for movement control is fundamentally different for target-directed and allocentric movements. The results suggest that current computational and neural models of sensorimotor control that are based entirely on data derived from target-directed paradigms have to be modified to accommodate performance in the allocentric tasks used in our experiments. As a consequence, the results cast doubt on the idea that models of sensorimotor control developed exclusively from data obtained in target-directed paradigms are also valid in the context of allocentric tasks, such as drawing, copying, or imitative gesturing, that characterize much of human behavior.

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