Showing papers in "Physiology in 2002"
TL;DR: Intracellular acidosis due mainly to lactic acid accumulation has been regarded as the most important cause of skeletal muscle fatigue, but recent studies show little direct effect of acidosis on muscle function at physiological temperatures.
Abstract: Intracellular acidosis due mainly to lactic acid accumulation has been regarded as the most important cause of skeletal muscle fatigue. Recent studies on mammalian muscle, however, show little direct effect of acidosis on muscle function at physiological temperatures. Instead, inorganic phosphate, which increases during fatigue due to breakdown of creatine phosphate, appears to be a major cause of muscle fatigue.
597 citations
TL;DR: Ca2+-activated K+ channels of large conductance control a large variety of physiological processes, including smooth muscle tone, neurosecretion, and hearing, which are fundamental to the adequate function of many tissues.
Abstract: Ca2+-activated K+ channels of large conductance (MaxiK or BK channels) control a large variety of physiological processes, including smooth muscle tone, neurosecretion, and hearing. Despite being coded by a single gene (Slowpoke), the diversity of MaxiK channels is great. Regulatory b-subunits, splicing, and metabolic regulation create this diversity fundamental to the adequate function of many tissues.
286 citations
TL;DR: Vascular biology is providing increased knowledge of the mechanisms involved and thus contributing to the understanding of the pathophysiology of the disease.
Abstract: The structure of the resistance vessels is altered (remodeled) in individuals with high blood pressure (essential hypertension). The structure is dependent not only on blood pressure but also on blood flow and hormonal environment. Vascular biology is providing increased knowledge of the mechanisms involved and thus contributing to our understanding of the pathophysiology of the disease.
229 citations
TL;DR: The progressive acidification of secretory organelles does not reflect an increased proton pumping activity but rather the decreased conduction of a "proton leak" pathway resembling the recently cloned voltage-gated proton channels.
Abstract: An optimal pH is maintained in each secretory and endocytic organelle by the balance between active H(+) pumping and passive H(+) efflux. The progressive acidification of secretory organelles does not reflect an increased proton pumping activity but rather the decreased conduction of a "proton leak" pathway resembling the recently cloned voltage-gated proton channels.
220 citations
TL;DR: The plasminogen activator inhibitor 1 (PAI-1) as mentioned in this paper is a low-density lipoprotein receptor superfamily member-dependent mechanism, which can be used to suppress the activity of the PA and t-PA.
Abstract: Plasminogen activator inhibitor 1 (PAI-1) inhibits plasminogen activators (u-PA and t-PA) by forming stable complexes endocytosed via a low-density lipoprotein receptor superfamily member-dependent mechanism. PAI-1 circulates actively in plasma and latently in platelets but is also secreted and deposited into the matrix by several cells, where it participates in tissue repair processes.
192 citations
TL;DR: The pacemaker current has unusual characteristics, including activation on hyperpolarization, permeability to K+ and Na+, modulation by internal cAMP, and a tiny, single-channel conductance.
Abstract: The “funny” (pacemaker) current has unusual characteristics, including activation on hyperpolarization, permeability to K+ and Na+, modulation by internal cAMP, and a tiny, single-channel conductance. In cardiac cells and neurons, pacemaker channels control repetitive activity and excitability. The recent cloning of HCN subunits provides new insight into the molecular basis for the funny channel properties.
192 citations
TL;DR: Hypoxic pulmonary vasoconstriction matches perfusion to ventilation and optimizes systemic oxygenation and membrane potential, Ca(2+) entry, and tone.
Abstract: Hypoxic pulmonary vasoconstriction matches perfusion to ventilation and optimizes systemic oxygenation. Alterations in Po2 are sensed by a vascular redox O2 sensor in the pulmonary artery smooth muscle cell, probably within the mitochondria. This creates a signal that modulates redox-sensitive K+ channels, thereby controlling membrane potential, Ca2+ entry, and tone.
159 citations
TL;DR: New methods in experimental fluid mechanics provide insights into the physiological mechanisms of aquatic force generation and limits to locomotor performance.
Abstract: Understanding how fishes generate external fluid force to swim steadily and maneuver has proven to be difficult because water does not provide a stable platform for force measurement. But new methods in experimental fluid mechanics provide insights into the physiological mechanisms of aquatic force generation and limits to locomotor performance.
120 citations
TL;DR: The basal ganglia are part of a neuronal network organized in parallel circuits that give rise to poverty and slowness of movement in Parkinson's disease or dyskinesias.
Abstract: The basal ganglia are part of a neuronal network organized in parallel circuits. The "motor circuit" is most relevant to the pathophysiology of movement. Abnormal increment or reduction in the inhibitory output activity of basal ganglia give rise, respectively, to poverty and slowness of movement (i.e., Parkinson's disease) or dyskinesias.
116 citations
TL;DR: The development and maintenance of the vascular system requires not only the formation of new vessels but also the continuous adjustment of vessel and network structures in response to functional needs.
Abstract: The development and maintenance of the vascular system requires not only the formation of new vessels (vasculogenesis, angiogenesis) but also the continuous adjustment of vessel and network structures in response to functional needs. This "angioadaptation" depends on the interplay of vascular responses to growth factors, to the metabolic status of the tissue, and to hemodynamic forces exerted by the flowing blood.
116 citations
TL;DR: The brain possesses an intrinsic regulatory mechanism to maintain an adequate supply of O(2) and nutrition despite local increases in neuronal activity, and brain astrocytes function as an intermediary cell type by responding to glutamate released from activated neurons.
Abstract: The brain possesses an intrinsic regulatory mechanism to maintain an adequate supply of O2 and nutrition despite local increases in neuronal activity. Brain astrocytes function as an intermediary cell type by responding to glutamate released from activated neurons, and they couple cerebral blood flow by producing cytochrome P-450-derived epoxyeicosatrienoic acids that induce vasodilation and increase capillary density.
TL;DR: Event related brain potentials provide information about cortical processing in severe neurological patients whose cognitive abilities cannot be expressed in their behavior in coma and in a vegetative state.
Abstract: Event related brain potentials (ERPs) provide information about cortical processing in severe neurological patients whose cognitive abilities cannot be expressed in their behavior. In coma, ERPs contribute to the prediction of the outcome. In a vegetative state, ERPs uncover the functional state of cortical processes. The significance of ERPs in the neurophysiological study of consciousness is discussed.
TL;DR: There is more quantitative evidence suggesting a function for extracranial lymphatic vessels than exists to support a role for arachnoid villi and granulations in CSF transport.
Abstract: The textbook view that projections of the arachnoid membrane into the cranial venous sinuses represent the primary cerebrospinal fluid (CSF) absorption sites seems incompatible with many clinical and experimental observations. On balance, there is more quantitative evidence suggesting a function for extracranial lymphatic vessels than exists to support a role for arachnoid villi and granulations in CSF transport.
TL;DR: A novel role for aquaporin-1 as a gated ion channel reshapes our current views of this ancient family of transmembrane channel proteins as mentioned in this paper, which is part of the diverse major intrinsic protein family of water and solute channels.
Abstract: Mammalian aquaporins are part of the diverse major intrinsic protein family of water and solute channels. Intriguing links exist in structural and functional properties between aquaporins and ion channels. A novel role for aquaporin-1 as a gated ion channel reshapes our current views of this ancient family of transmembrane channel proteins.
TL;DR: Rat, monkey, and human infants have evolved to expect certain patterns of care and hyperactivity of immature stress systems such as the limbic-hypothalamic-pituitary-adrenal axis and the limbics-sympatho- adrenomedullary axis can alter their subsequent reactivity across the life span.
Abstract: Rat, monkey, and human infants have evolved to expect certain patterns of care. Spontaneous or experimental deviations of care from the norm result in infant stress responses. Hyperactivity of immature stress systems such as the limbic-hypothalamic-pituitary-adrenal axis and the limbic-sympatho-adrenomedullary axis can alter their subsequent reactivity across the life span.
TL;DR: The glycoprotein thrombopoietin (TPO) is the major stimulator of megakaryopoiesis and platelet production and its level is inversely correlated to the mass ofMegakaryocytes and platelets, which degrade the hormone following its binding to specific membrane receptors.
Abstract: The glycoprotein thrombopoietin (TPO) is the major stimulator of megakaryopoiesis and platelet production. Hepatocytes express TPO mRNA at a constant rate. The plasma TPO level is inversely correlated to the mass of megakaryocytes and platelets, which degrade the hormone following its binding to specific membrane receptors.
TL;DR: Alternative views are advanced suggesting that, in reptiles, cardiac shunts represent either an ancestral condition or an embryonic trait.
Abstract: The morphology of the reptilian heart results in the mixing of oxygenated and deoxygenated blood (cardiac shunts). In birds and mammals cardiac shunts are detrimental, but in reptiles this condition is often considered a derived trait, conveying important physiological functions and favored by natural selection. Alternative views are advanced suggesting that, in reptiles, cardiac shunts represent either an ancestral condition or an embryonic trait.
TL;DR: Although differentiated cells will usually maintain their specialized character, conversion of cellular specificities can be observed during adaptation or reparative regeneration, in pathological conditions, even highly specialized cells can alter their properties, leading to a deranged control of cell differentiation and/or proliferation.
Abstract: Although differentiated cells will usually maintain their specialized character, conversion of cellular specificities can be observed during adaptation or reparative regeneration. In pathological conditions, such as inflammation and carcinogenesis, even highly specialized cells can alter their properties, leading to a deranged control of cell differentiation and/or proliferation. Mitogen-activated protein kinases are central regulators of these processes.
TL;DR: The observation that, during maximum aerobic exercise, high-altitude natives generate lower-than-expected amounts of lactate may be caused mainly by upregulated metabolic control contributions from cell ATP demand and ATP supply pathways.
Abstract: For many years, physiologists have puzzled over the observation that, during maximum aerobic exercise, high-altitude natives generate lower-than-expected amounts of lactate; the higher the altitude, the lower the postexercise blood lactate peak. This paradoxical situation may be caused mainly by upregulated metabolic control contributions from cell ATP demand and ATP supply pathways.
TL;DR: Potential biomarkers of NO availability in human blood and critically discuss their respective significance and application fields are summarized and critically discussed.
Abstract: Disturbances of nitric oxide (NO) bioavailability may play a key role in vascular dysfunction and in the development of atherosclerotic lesions. Thus assessment of a reduced NO bioavailability in human circulation is of particular interest. Here we summarize potential biomarkers of NO availability in human blood and critically discuss their respective significance and application fields.
TL;DR: Exercise intolerance and early fatigue seem to be linked in part to intrinsic alterations of skeletal muscle with decreases in both the production of ATP by mitochondria and the transfer of energy through the phosphotransfer kinases.
Abstract: Heart failure is a syndrome that also affects the periphery. Exercise intolerance and early fatigue seem to be linked in part to intrinsic alterations of skeletal muscle with decreases in both the production of ATP by mitochondria and the transfer of energy through the phosphotransfer kinases.
TL;DR: Members of the drug transporter families MDR, MRP, and OATP have been identified in the BBB, and a detailed characterization of the involved proteins is now required to target drugs more efficiently to the brain.
Abstract: Distinct transport proteins regulate the movement of waste products and xenobiotics across the blood-brain barrier (BBB). Members of the drug transporter families MDR, MRP, and OATP have been identified in the BBB, and a detailed characterization of the involved proteins is now required to target drugs more efficiently to the brain.
TL;DR: The heparan sulfate proteoglycan agrin is responsible for the formation, maintenance, and regeneration of the neuromuscular junction and evidence for additional functions of agrin during axonal growth, establishment of the blood-brain barrier, and Alzheimer's disease is accumulating.
Abstract: The heparan sulfate proteoglycan agrin is responsible for the formation, maintenance, and regeneration of the neuromuscular junction. In the central nervous system, agrin is widely expressed and concentrated at interneuronal synapses, but its function during synaptogenesis remains controversial. Instead, evidence for additional functions of agrin during axonal growth, establishment of the blood-brain barrier, and Alzheimer's disease is accumulating.
TL;DR: In 1866 at Carl Ludwig's Physiological Institute at Leipzig, Elias Cyon described the influence of diastolic filling of the isolated perfused frog heart on ejection volume.
Abstract: In 1866 at Carl Ludwig’s Physiological Institute at Leipzig, Elias Cyon described the influence of diastolic filling of the isolated perfused frog heart on ejection volume. A study performed at the institute of the effect of filling pressure on contraction amplitude was published in 1869 by Joseph Coats, based on a recording made by Henry P. Bowditch.
TL;DR: In a paradigm of cellular differentiation, human myoblast fusion, it is investigated how a Ca(2+) influx, indispensable for fusion, is triggered by newly expressed Kir2.1 K(+) channels, via their hyperpolarizing effect on the membrane potential, which causes intracellular Ca( 2+) to rise.
Abstract: In a paradigm of cellular differentiation, human myoblast fusion, we investigated how a Ca2+ influx, indispensable for fusion, is triggered. We show how newly expressed Kir2.1 K+ channels, via their hyperpolarizing effect on the membrane potential, generate a window Ca2+ current (mediated by a1H T-type Ca2+ channels), which causes intracellular Ca2+ to rise.
TL;DR: Muscle myosin II is an ATP-driven, actin-based molecular motor and recent developments in optical tweezers technology have made it possible to study movement and force production on the single-molecule level and to find out how different myOSin isoforms may have adapted to their specific physiological roles.
Abstract: Muscle myosin II is an ATP-driven, actin-based molecular motor. Recent developments in optical tweezers technology have made it possible to study movement and force production on the single-molecule level and to find out how different myosin isoforms may have adapted to their specific physiological roles.
TL;DR: These studies reveal a complex neural system whose design and operation apparently does not conform to rigid deterministic principles.
Abstract: Trichromatic color vision is rare among mammals, occurring only in some primates Recent work has elucidated the adaptive behavioral significance of trichromacy as well as its underlying genetic and neurophysiological mechanisms These studies reveal a complex neural system whose design and operation apparently does not conform to rigid deterministic principles
TL;DR: The metabolic functionality of adipose tissue is intimately dependent on local communication between various cell types, which influences not only the equilibrium between lipogenesis and lipolysis but also between hypertrophic and hyperplastic growth, thereby determining the role adiposes tissue plays in the insulin resistance syndrome.
Abstract: The metabolic functionality of adipose tissue is intimately dependent on local communication between various cell types. It influences not only the equilibrium between lipogenesis and lipolysis but also between hypertrophic and hyperplastic growth, thereby determining the role adipose tissue plays in the insulin resistance syndrome.
TL;DR: William Harvey was born to a reasonably well-to-do family during a period of unparalled intellectual fervor, which has come to be known as the period of the “scientific revolution.
Abstract: William Harvey was born to a reasonably well-to-do family during a period of unparalled intellectual fervor. The year was 1578, and the period has come to be known as the period of the “scientific revolution.” And indeed, it was a revolution, not because of the frequency of scientific
TL;DR: The ATP-sensitive K(+) channels in the brain respond in ATP-depleted metabolic states such as hypoxia and may be involved in the protection mechanism against energy-consuming generalized seizure.
Abstract: Rapid minimization of energy consumption in excitable tissues is effective protection from lethal effects of extreme metabolic stress. The ATP-sensitive K+ channels in the brain respond in ATP-depleted metabolic states such as hypoxia and may be involved in the protection mechanism against energy-consuming generalized seizure.