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The Journal of Physiological Sciences :... Nov 2016The effects of gravitational loading (G load) on humans have been studied ever since the early 20th century. After the dangers of G load in the vertical head-to-leg... (Review)
Review
The effects of gravitational loading (G load) on humans have been studied ever since the early 20th century. After the dangers of G load in the vertical head-to-leg direction (+Gz load) became evident, many animal experiments were performed between 1920 and 1945 in an effort to identify the origins of high G-force-induced loss of consciousness (G-LOC), which led to development of the anti-G suit. The establishment of norms and training for G-LOC prevention resulted in a gradual decline in reports of animal experiments on G load, a decline that steepened with the establishment of anti-G techniques in humans, such as special breathing methods and skeletal muscle contraction, called an anti-G straining maneuver, which are voluntary physiological functions. Because the issue involves humans during flight, the effects on humans themselves are clearly of great importance, but ethical considerations largely preclude any research on the human body that probes to any depth the endogenous physiological states and functions. The decline in reports on animal experiments may therefore signify a general decline in research into the changes seen in the various involuntary, autonomic functions. The declining number of related reports on investigations of physiological autonomic systems other than the circulatory system seems to bear this out. In this review, we therefore describe our findings on the effects of G load on the autonomic nervous system, cardiac function, cerebral blood flow, tissue oxygen level, and other physiological autonomic functions as measured in animal experiments, including denervation or pharmacological blocking, in an effort to present the limits and the mechanisms of G-load response extending physiologically. We demonstrate previously unrecognized risks due to G load, and also describe fundamental research aimed at countering these effects and development of a scientific training measure devised for actively enhancing +Gz tolerance in involuntary, autonomic system functions. The research described here is rough and incomplete, but it is offered as a beginning, in the hope that researchers may find it of reference and carry the effort toward completion. The advances described here include (1) a finding that cerebral arterial perfusion pressure decreases to nearly zero under +5.0 Gz loads, (2) indications that G load may cause myocardial microinjuries, (3) detection of differences between cerebral regions in tissue-oxygen level under +3.0 Gz load, (4) discovery that hypotension is deeper under decreasing +Gz loads than increasing +Gz loads with use of an anti-G system, due in part to suppression of baroreceptor reflex, and (5) revelations and efforts investigating new measures to reduce cerebral hypotension, namely the "teeth-clenching pressor response" and preconditioning with slight but repeated G loads.
Topics: Animals; Autonomic Nervous System; Blood Circulation; Gravitation; Rats
PubMed: 27262847
DOI: 10.1007/s12576-016-0461-4 -
Journal of Physiology and Pharmacology... Feb 2012In recent decades, among many physiological regulatory systems operating as local and central controls, the mechanism of the local regulatory system based on the uptake... (Review)
Review
In recent decades, among many physiological regulatory systems operating as local and central controls, the mechanism of the local regulatory system based on the uptake and retrograde transfer of hormones and other physiological regulators to the places of their secretion or their destination transfer to nearby structures has become precisely understood. The system of the retrograde transfer and local destination transfer of the physiological regulators, situated between endocrine and paracrine regulation, operates primarily on the basis of specific morphological adaptations of the local blood circulatory system and lymphatic system. These adaptations enable the transfer of the regulatory molecules through the walls of blood and lymph vessels and locally increase their concentrations in the arterial blood supplying the organ secreting them (retrograde transfer) or a nearby organ (destination transfer). Extensive studies on the structure and functions of the retrograde and destination transfer system have focused on several key areas: the female and male reproductive organs, the perihypophyseal vascular complex (the venous cavernous sinus and the internal carotid artery or the rete mirabile of the internal carotid artery or maxillary artery), and the periophthalmic vascular complex (the venous ophthalmic sinus or plexus and the rete mirabile of the external ophthalmic artery). The local retrograde transfer of regulatory molecules not only allows them to be reused but also influences their production by a feedback mechanism. The local destination transfer of physiological regulators can selectively supply nearby organs with certain regulatory factors and thereby affect their function. Many observations indicate that the retrograde and local destination transfer of hormones and other biologically active substances may be a universal physiological regulatory mechanism, operating with only minor modifications in various species of animals and in humans. This review evaluates the most important published experimental studies and presents facts and hypothesis on the regulatory role of the retrograde and destination transfer of many steroid hormones, prostaglandins, pheromones, neurotransmitters (neurohormones) and CO in male and female reproductive physiology, in the physiology of the central nervous system and hypophysis and in eye function.
Topics: Animals; Biological Transport; Blood Circulation; Humans; Lymphatic System; Reproduction
PubMed: 22460455
DOI: No ID Found -
The American Journal of Cardiology Apr 1992Inhibitors of angiotensin-converting enzyme (ACE) exert favorable regional hemodynamic effects at various sites. In patients with essential hypertension, ACE inhibitors... (Review)
Review
Inhibitors of angiotensin-converting enzyme (ACE) exert favorable regional hemodynamic effects at various sites. In patients with essential hypertension, ACE inhibitors reduce renal vascular resistance while enhancing renal blood flow, glomerular filtration rate, and acute and sustained natriuresis. Whereas these agents may either reduce or have no effect on hepatic blood flow, they are associated with reduced splanchnic resistance. ACE inhibitors reduce total peripheral resistance and may maintain limb blood flow. In normal subjects, they augment blood flow to skeletal muscle and skin and reduce peripheral resistance in vessels supplying these regions. ACE inhibitors appear to exert a vasodilatory effect on large arteries as well as arterioles. Dilatation is often accompanied by significant improvements in arterial compliance, possibly due to direct effects of the renin-angiotensin system on the arterial wall. Reduction of blood pressure is generally not accompanied by reduced cerebral blood flow. Enhanced tissue effects of newer ACE inhibitors such as quinapril may result in improved regional hemodynamic effects.
Topics: Angiotensin-Converting Enzyme Inhibitors; Blood Circulation; Cerebrovascular Circulation; Humans; Liver Circulation; Regional Blood Flow; Renal Circulation; Vascular Resistance
PubMed: 1546638
DOI: 10.1016/0002-9149(92)90280-c -
Chang Gung Medical Journal 2010The therapeutic effect of cardiac glycosides for congestive heart failure lies in their reversible inhibition on Na+, K+-ATPase located in human myocardium. Several... (Review)
Review
The therapeutic effect of cardiac glycosides for congestive heart failure lies in their reversible inhibition on Na+, K+-ATPase located in human myocardium. Several steroid-like compounds containing a core structure similar to cardiac glycosides have been found in many Chinese herbs and medicinal animal products conventionally used to promote blood circulation. They are putatively responsible for the therapeutic effect of those medicinal products via the same mechanism of inhibiting Na+, K+-ATPase. Inhibitory potency on Na+, K+-ATPase by ginsenosides, one of the identified steroid-like compounds, is significantly affected by sugar attachment that might cause steric hindrance of their binding to Na+, K+-ATPase. Ginsenosides with sugar moieties attached only to the C-3 position of the steroid-like structure, equivalent to the sugar position in cardiac glycosides, substantially inhibit Na+, K+-ATPase. However, their inhibitory potency is abolished when sugar moieties are linked to the C-6 or C-20 position of the steroid-like structure. In contrast, no appreciable contents of steroid-like compounds are found in danshen, a well-known Chinese herb traditionally regarded as an effective medicine promoting blood circulation. Instead, magnesium lithospermate B (MLB), the major soluble ingredient in danshen, is assumed to be responsible for the therapeutic effect by inhibiting Na+, K+-ATPase in a manner comparable to cardiac glycosides. Neuroprotective effects of cardiac glycosides, ginsenosides and MLB against ischemic stroke were accordingly observed in a cortical brain slice-based assay model. Whether the neuroprotection is also triggered by inhibition of Na+, K+-ATPase remains to be investigated. Molecular modeling suggests that cardiac glycosides, ginsenosides and MLB presumably bind to the same extracellular pocket of the Na+, K+-ATPase alpha subunit.
Topics: Animals; Blood Circulation; Drugs, Chinese Herbal; Humans; Sodium-Potassium-Exchanging ATPase
PubMed: 20438664
DOI: No ID Found -
Current Biology : CB Jun 2010The primitive blood circulation requires intravascular plasma flow. However, it remains unclear whether the onset of earliest blood circulation is dependent solely on...
The primitive blood circulation requires intravascular plasma flow. However, it remains unclear whether the onset of earliest blood circulation is dependent solely on establishment of a functional circulatory organ or whether it also requires active processes inherent in blood cells. In this study, we present novel mechanisms for the onset of blood circulation by monitoring fluorescently labeled blood precursors and blood vessels in zebrafish. The earliest blood circulation occurs synchronously. This synchrony is achieved by the retention of erythroid precursors on the lumen of the vasculature after their invasion from the subaortic region, and then by simultaneous release of these precursors into the flow. Morphological and biochemical analyses suggest that the onset of blood circulation accompanies disruption of blood cell-to-vessel adhesion and requires metalloprotease-dependent processes. ADAM8, a member of the a disintegrin and metalloprotease (ADAM) family, mediates the onset of blood circulation. In ADAM8-depleted embryos, erythroid cells fail to detach from the vascular lumen and stagnate. Expression of a protease-defective ADAM8 in erythroid cells causes dominant-negative effects on blood circulation, suggesting cell-autonomous roles of ADAM8. Based on these findings, we propose that the first erythroid cells require both flow-dependent passive and proteolysis-dependent active processes to enter the circulation.
Topics: Animals; Blood Circulation; Metalloproteases; Zebrafish
PubMed: 20605457
DOI: 10.1016/j.cub.2010.04.052 -
Minerva Anestesiologica Sep 2011Therapeutich hypothermia (TH) has been shown to improve neurological outcome and survival after witnessed cardiac arrest (CA) that is due to ventricular fibrillation.... (Review)
Review
Therapeutich hypothermia (TH) has been shown to improve neurological outcome and survival after witnessed cardiac arrest (CA) that is due to ventricular fibrillation. Although TH is widely used following witnessed CA as well as all forms of initial rhythm, the mortality rate after CA remains unacceptably high, and additional study is needed to understand when and how to implement hypothermia in the post-resuscitation phase. Experimental studies have emphasized the importance of initiating cooling soon after the return of spontaneous circulation (ROSC) or even during cardiopulmonary resuscitation (CPR). Clinical studies have shown that pre-hospital induction of hypothermia is feasible and has no major adverse events-even when used intra-arrest-and may provide some additional benefits compared to delayed in-hospital cooling. Thus, hypothermia use should not be limited to the Intensive Care Unit but can be initiated in the field/ambulance or in the Emergency Department, then continued after hospital admission- even during specific procedures such as coronary angiography-as part of the global management of CA patients. Various methods (both non-invasive and invasive) are available to achieve and maintain the target temperature; however, only some of these methods-which include cold fluids, ice packs, iced pads and helmet and trans-nasal cooling- are easily deployed in the pre-hospital setting.
Topics: Adult; Blood Circulation; Body Temperature; Cardiopulmonary Resuscitation; Critical Care; Emergency Medical Services; Heart Arrest; Humans; Hypothermia, Induced; Infusions, Intravenous; Middle Aged; Time Factors
PubMed: 21878875
DOI: No ID Found -
Journal of Cellular and Molecular... May 2010This review addresses the use of the different antihypertensive agents currently available and some in development, and their effects on the vasculature. The different... (Review)
Review
This review addresses the use of the different antihypertensive agents currently available and some in development, and their effects on the vasculature. The different classes of agents used in the treatment of hypertension, and the results of recent large clinical trials, dosing protocols and adverse effects are first briefly summarized. The consequences on blood vessels of the use of antihypertensive drugs and the differential effects on the biology of large and small arteries resulting in modulation of vascular remodelling and dysfunction in hypertensive patients are then described. Large elastic conduit arteries exhibit outward hypertrophic remodelling and increased stiffness, which contributes to raise systolic blood pressure and afterload on the heart. Small resistance arteries undergo eutrophic or hypertrophic inward remodelling, and impair tissue perfusion. By these mechanisms both large and small arteries may contribute to trigger cardiovascular events. Some antihypertensive agents correct these changes, which could contribute to improved outcome. The mechanisms that at the level of the vascular wall lead to remodelling and can be beneficially affected by antihypertensive agents will also be addressed. These include vasoconstriction, growth and inflammation. The molecular pathways contributing to growth and inflammation will be summarily described. Further identification of these signalling pathways should allow identification of novel targets leading to development of new and improved medications for the treatment of hypertension and cardiovascular disease.
Topics: Animals; Antihypertensive Agents; Blood Circulation; Blood Vessels; Humans
PubMed: 20345850
DOI: 10.1111/j.1582-4934.2010.01056.x -
Journal of the American College of... May 1985The administration of digitalis glycosides causes a variety of extracardiac effects. In both normal human subjects and in other species, digitalis increases smooth... (Review)
Review
The administration of digitalis glycosides causes a variety of extracardiac effects. In both normal human subjects and in other species, digitalis increases smooth muscle tone of resistance and capacitance vessels. The vasoconstriction is mediated, in part, by a direct action of these glycosides on smooth muscle and, in part, by an increase in alpha-adrenergic tone. Constriction of coronary and splanchnic vessels may lead to myocardial or mesenteric ischemia. In contrast to normal subjects, patients with congestive heart failure demonstrate arteriolar and venodilation in response to these glycosides, possibly because the myocardial effect, to increase cardiac output and peripheral blood flow, overcomes the vasoconstrictor properties of these drugs. Other important actions of digitalis glycosides occur in the central and peripheral nervous systems. Their effects on the area postrema of the medulla oblongata are largely responsible for the alpha-adrenergic-mediated peripheral vasoconstriction, as well as the nausea and vomiting that frequently accompany digitalis intoxication. Actions of glycosides on the cerebral cortex are responsible for the wide range of neurotoxic effects that range from visual disturbances and headaches to seizures and coma. Finally, peripheral neurologic effects of digitalis glycosides on baroreceptor and cardiac afferent fibers may: improve the depressed function of these receptors in the situation of heart failure, and reflexly lower peripheral vascular resistance, thereby partially preventing the vascular constrictor action of these glycosides.
Topics: Animals; Blood Circulation; Coronary Circulation; Digestive System; Digitalis Glycosides; Dogs; Heart; Heart Failure; Humans; Kidney; Muscle, Smooth; Neurons, Afferent; Pressoreceptors; Rabbits; Splanchnic Circulation
PubMed: 3886756
DOI: 10.1016/s0735-1097(85)80468-x -
British Heart Journal Apr 1956
Topics: Blood; Blood Circulation; Cardiovascular Abnormalities; Cardiovascular System; Heart; Heart Septal Defects, Atrial; Humans
PubMed: 13315850
DOI: 10.1136/hrt.18.2.209 -
British Journal of Anaesthesia Mar 1954
Topics: Anesthesia; Anesthetics; Blood Circulation; Blood Physiological Phenomena; Humans; Veins
PubMed: 13149714
DOI: 10.1093/bja/26.2.118