bluuebunny/crossref_metadata_2025 huggingface dataset:
Loop gain of reflexes controlling human standing measured with the use of postural and vestibular disturbances
Authors: Fitzpatrick R. , Burke D. , Gandevia S. C.
Published: December 2017

1. In this study we measured the loop gain of postural reflexes in standing human subjects. Reflex activity is conventionally described in terms of the muscle activation arising from a perturbation, but in this study the ability of the evoked muscle activity to correct the perturbation was also measured, and the behavior of the entire feedback loop is described. 2. A weak continuous random perturbation was applied at waist level to standing subjects. The effects of the perturbation on body sway and soleus electromyogram (EMG) were identified by cross-correlation, and spectral analysis was used to estimate the open-loop reflex transmission characteristics (i.e., sway to EMG). Under the same conditions, activity in the leg muscles was evoked by galvanic vestibular stimulation with the use of a continuous randomly varying current. The effects on soleus EMG and the subsequent body sway were identified by cross-correlation. This allowed calculation of the open-loop muscle and load behavior (i.e., EMG to sway). From these open-loop reflex and muscle and load transfer functions, the loop gain and phase were calculated. 3. In addition to the gain of the feedback loop, the study describes the transmission characteristics of reflex responses in the leg muscles associated with body sway and the effects of excluding visual and proprioceptive contributions to the response; the transfer function of human soleus with a stimulus that preserves the normal recruitment of motoneurons, including the effects of different load conditions on the muscle; and the transmission characteristics of vestibular pathways that evoke responses in the leg muscles during standing in situations that might modify the reflexes. 4. When standing, the loop gain of reflex feedback is approximately unity and is unchanged by eye closure and stability of support. Reflex transmission introduced a marked phase advance, and this served to offset most of the phase lag introduced by muscle and load. The residual phase lag could explain the frequency of tremor observed during standing (6–8 Hz). 5. The gain of the feedback loop (approximately 1) is higher than suggested by both previous estimates and theoretical considerations, but is still insufficient to explain the stability of normal human standing. This implies that, although sensory information is used to control posture, it does not do so exclusively through a negative feedback control process. The experimental findings are consistent with a reflex response based on a feed-forward process, and this would result in prediction of the response necessary to counteract a postural disturbance.
Differential Response Properties to Amplitude Modulated Signals in the Dorsal Nucleus of the Lateral Lemniscus of the Mustache Bat and the Roles of GABAergic Inhibition
Authors: Yang Lichuan , Pollak George D.
Published: December 2017

Yang, Lichuan and George D. Pollak. Differential response properties to amplitude modulated signals in the dorsal nucleus of the lateral lemniscus of the mustache bat and the roles of GABAergic inhibition. J. Neurophysiol. 77: 324–340, 1997. We studied the phase-locking of 89 neurons in the dorsal nucleus of the lateral lemniscus (DNLL) of the mustache bat to sinusoidally amplitude modulated (SAM) signals and the influence that GABAergic inhibition had on their response properties. Response properties were determined with tone bursts at each neuron's best frequency and then with a series of SAM signals that had modulation frequencies ranging from 50–100 to 800 Hz in 100-Hz steps. DNLL neurons were divided into two principal types: sustained neurons (55%), which responded throughout the duration of the tone burst, and onset neurons (45%), which responded only at the beginning of the tone burst. Sustained and onset neurons responded differently to SAM signals. Sustained neurons responded with phase-locked discharges to modulation frequencies ≤400–800 Hz. In contrast, 70% of the onset neurons phase-locked only to low modulation frequencies of 100–300 Hz, whereas 30% of the onset neurons did not phase-lock to any modulation frequency. Signal intensity differentially affected the phase-locking of sustained and onset neurons. Sustained neurons exhibited tight phase-locking only at low intensities, 10–30 dB above threshold. Onset neurons, in contrast, maintained strong phase-locking even at relatively high intensities. Blocking GABAergic inhibition with bicuculline had different effects on the phase-locking of sustained and onset neurons. In sustained neurons, there was an overall decline in phase-locking at all modulation frequencies. In contrast, 70% of the onset neurons phase-locked to much higher modulation frequencies than they did when inhibition was intact. The other 30% of onset neurons phase-locked to SAM signals, although they fired only with an onset response to the same signals before inhibition was blocked. In both cases, blocking GABAergic inhibition transformed their responses to SAM signals into patterns that were more like those of sustained neurons. We also propose mechanisms that could explain the differential effects of GABAergic inhibition on onset neurons that locked to low modulation frequencies and on onset neurons that did not lock to any SAM signals before inhibition was blocked. The key features of the proposed mechanisms are the absolute latencies and temporal synchrony of the excitatory and inhibitory inputs.
Simulated Optic Flow and Extrastriate Cortex. I. Optic Flow Versus Texture
Authors: Kim Jong-Nam , Mulligan Kathleen , Sherk Helen
Published: December 2017

Kim, Jong-Nam, Kathleen Mulligan, and Helen Sherk. Simulated optic flow and extrastriate cortex. I. Optic flow versus texture. J. Neurophysiol. 77: 554–561, 1997. A locomoting observer sees a very different visual scene than an observer at rest: images throughout the visual field accelerate and expand, and they follow approximately radial outward paths from a single origin. This so-called optic flow field is presumably used for visual guidance, and it has been suggested that particular areas of visual cortex are specialized for the analysis of optic flow. In the cat, the lateral suprasylvian visual area (LS) is a likely candidate. To test the hypothesis that LS is specialized for analysis of optic flow fields, we recorded cell responses to optic flow displays. Stimulus movies simulated the experience of a cat trotting slowly across an endless plain covered with small balls. In different simulations we varied the size of balls, their organization (randomly or regularly dispersed), and their color (all one gray level, or multiple shades of gray). For each optic flow movie, a “texture” movie composed of the same elements but lacking optic flow cues was tested. In anesthetized cats, >500 neurons in LS were studied with a variety of movies. Most (70%) of 454 visually responsive cells responded to optic flow movies. Visually responsive cells generally preferred optic flow to texture movies (69% of those responsive to any movie). The direction in which a movie was shown (forward or reverse) was also an important factor. Most cells (68%) strongly preferred forward motion, which corresponded to visual experience during locomotion.
Three-Dimensional Model of the Human Eye-Head Saccadic System
Authors: Tweed Douglas
Published: December 2017

Tweed, Douglas. Three-dimensional model of the human eye-head saccadic system. J. Neurophysiol. 77: 654–666, 1997. Current theories of eye-head gaze shifts deal only with one-dimensional motion, and do not touch on three-dimensional (3-D) issues such as curvature and Donders' laws. I show that recent 3-D data can be explained by a model based on ideas that are well established from one-dimensional studies, with just one new assumption: that the eye is driven toward a 3-D orientation in space that has been chosen so that Listing's law of the eye in head will hold when the eye-head movement is complete. As in previous, one-dimensional models, the eye and head are feedback-guided and the commands specifying desired eye position eye pass through a neural “saturation” so as to stay within the effective oculomotor range. The model correctly predicts the complex, 3-D trajectories of the head, eye in space, and eye in head in a variety of saccade tasks. And when it moves repeatedly to the same target, varying the contributions of eye and head, the model lands in different eye-in-space positions, but these positions differ only in their cyclotorsion about the line of sight, so they all point that line at the target—a behavior also seen in real eye-head saccades. Between movements the model obeys Listing's law of the eye in head and Donders' law of the head on torso, but during certain gaze shifts involving large torsional head movements, it shows marked, 8° deviations from Listing's law. These deviations are the most important untested predictions of the theory. Their experimental refutation would sink the model, whereas confirmation would strongly support its central claim that the eye moves toward a 3-D position in space chosen to obey Listing's law and, therefore, that a Listing operator exists upstream from the eye pulse generator.
Complex Spike Activity of Purkinje Cells in the Ventral Uvula and Nodulus of Pigeons in Response to Translational Optic Flow
Authors: Wylie Douglas R. W. , Frost Barrie J.
Published: December 2017

Wylie, Douglas R. W. and Barrie J. Frost. Complex spike activity of Purkinje cells in the ventral uvula and nodulus of pigeons in response to translational optic flow. J. Neurophysiol. 81: 256–266, 1999. The complex spike (CS) activity of Purkinje cells in the ventral uvula and nodulus of the vestibulocerebellum was recorded from anesthetized pigeons in response to translational optic flow. Translational optic flow was produced using a “translator” projector: a mechanical device that projected a translational optic flowfield onto the walls, ceiling, and floor of the room and encompassed the entire binocular visual field. CS activity was broadly tuned but maximally modulated in response to translational optic flow along a “best” axis. Each neuron was assigned a vector representing the direction in which the animal would need to translate to produce the optic flowfield that resulted in maximal excitation. The vector is described with reference to a standard right-handed coordinate system, where the vectors, + x, + y, and + z represent, rightward, upward, and forward translation of the animal, respectively. Neurons could be grouped into four response types based on the vector of maximal excitation. + y neurons were modulated maximally in response to a translational optic flowfield that results from self-motion upward along the vertical ( y) axis. − y neurons also responded best to translational optic flow along the vertical axis but showed the opposite direction preference. The two remaining groups responded best to translational optic flow along horizontal axes: − x + z neurons and − x− z neurons. In summary, our results suggest that the olivocerebellar system dedicated to the analysis of translational optic flow is organized according to a reference frame consisting of three approximately orthogonal axes: the vertical axis, and two horizontal axes oriented 45° to either side the midline. Previous research has shown that the rotational optic flow system, the eye muscles, the vestibular semicircular canals and the postural control system all share a similar spatial frame of reference.
Muscarine Modulates Ca2+ Channel Currents in Rat Sensorimotor Pyramidal Cells Via Two Distinct Pathways
Authors: Stewart Ansalan E. , Yan Zhen , Surmeier D. James , Foehring Robert C.
Published: December 2017

Stewart, Ansalan E., Zhen Yan, D. James Surmeier, and Robert C. Foehring. Muscarine modulates Ca2+ channel currents in rat sensorimotor pyramidal cells via two distinct pathways. J. Neurophysiol. 81: 72–84, 1999. We used the whole cell patch-clamp technique and single-cell reverse transcription-polymerase chain reaction (RT-PCR) to study the muscarinic receptor-mediated modulation of calcium channel currents in both acutely isolated and cultured pyramidal neurons from rat sensorimotor cortex. Single-cell RT-PCR profiling for muscarinic receptor mRNAs revealed the expression of m1, m2, m3, and m4 subtypes in these cells. Muscarine reversibly reduced Ca2+ currents in a dose-dependent manner. The modulation was blocked by the muscarinic antagonist atropine. When the internal recording solution included 10 mM ethylene glycol-bis(β-aminoethyl ether)- N,N,N′,N′-tetraacetic acid (EGTA) or 10 mM bis-( o-aminophenoxy)- N,N,N′,N′-tetraacetic acid (BAPTA), the modulation was rapid (τonset ∼ 1.2 s). Under conditions where intracellular calcium levels were less controlled (0.0–0.1 mM BAPTA), a slowly developing component of the modulation also was observed (τonset ∼17 s). Both fast and slow components also were observed in recordings with 10 mM EGTA or 20 mM BAPTA when Ca2+ was added to elevate internal [Ca2+] (∼150 nM). The fast component was due to a reduction in both N- and P-type calcium currents, whereas the slow component involved L-type current. N-ethylmaleimide blocked the fast component but not the slow component of the modulation. Preincubation of cultured neurons with pertussis toxin (PTX) also greatly reduced the fast portion of the modulation. These results suggest a role for both PTX-sensitive G proteins as well as PTX-insensitive G proteins in the muscarinic modulation. The fast component of the modulation was reversed by strong depolarization, whereas the slow component was not. Reblock of the calcium channels by G proteins (at −90 mV) occurred with a median τ of 68 ms. We conclude that activation of muscarinic receptors results in modulation of N- and P-type channels by a rapid, voltage-dependent pathway and of L-type current by a slow, voltage-independent pathway.
Impairment of Neocortical Long-Term Potentiation in Mice Deficient of Endothelial Nitric Oxide Synthase
Authors: Haul Sven , Gödecke Axel , Schrader Jürgen , Haas Helmut L. , Luhmann Heiko J.
Published: December 2017

Impairment of neocortical long-term potentiation in mice deficient of endothelial nitric oxide synthase. The role of the possible retrograde messenger nitric oxide (NO) in the induction of long-term potentiation (LTP) was studied in supragranular layers of somatosensory cortical slices obtained from adult mice. High-frequency stimulation produced a slowly rising, long-lasting (50 min) and significant ( P < 0.001) increase in the extracellular synaptic response by 23%. The induction of LTP was independent from activation of N-methyl-d-aspartate (NMDA) receptors, but prevented by bath application of N G-nitro-l-arginine methyl ester (l-NAME), indicating that one or several of the different NO synthases (NOS) produced NO within the postsynaptic neuron. No LTP could be induced in knockout mice lacking the endothelial NOS (eNOS) isoform. These data suggest that eNOS is involved in an NMDA receptor–independent form of LTP in the rodent cerebral cortex.
The evolutionarily conserved Dim1 protein defines a novel branch of the thioredoxin fold superfamily
Authors: ZHANG YU-ZHU , GOULD KATHLEEN L. , DUNBRACK ROLAND L. , CHENG HONG , RODER HEINRICH , GOLEMIS ERICA A.
Published: December 2017

Zhang, Yu-Zhu, Kathleen L. Gould, Roland L. Dunbrack, Jr., Hong Cheng, Heinrich Roder, and Erica A. Golemis. The evolutionarily conserved Dim1 protein defines a novel branch of the thioredoxin fold superfamily. Physiol. Genomics 1: 109–118, 1999.—Dim1 is a small evolutionarily conserved protein essential for G2/M transition that has recently been implicated as a component of the mRNA splicing machinery. To date, the mechanism of Dim1 function remains poorly defined, in part because of the absence of informative sequence homologies between Dim1 and other functionally defined proteins or protein domains. We have used a combination of molecular modeling and NMR structural analysis to demonstrate that ∼125 of the 142 amino acids of human Dim1 (hDim1) define a novel branch of the thioredoxin fold superfamily. Mutational analysis of Dim1 based on the predicted fold indicates that alterations in the region corresponding to the thioredoxin active site do not affect Dim1 activity. However, removal of a very short carboxy-terminal extension generates a dominant negative form of the protein [hDim1-(1–128)] that when overproduced induces cell cycle arrest in G2, via a mechanism likely to involve alteration of Dim1 association with partner molecules. In sum, this study identifies the Dim1 proteins as a novel sixth branch of the thioredoxin superfamily involved in cell cycle.
Excitotoxic Amino Acids
Authors: Olney JW
Published: December 2017

The excitatory transmitters glutamate and aspartate and certain structural analogues, known collectively as excitotoxins, interact with synaptic membrane receptors to excite central nervous system (CNS) neurons, either physiologically or unto death, depending on the duration of receptor interaction. The ability of these agents, when administered orally or subcutaneously, to penetrate the enocrine hypothalamus and excite or destroy hypothalamic neurons makes them useful neuroendocrine research probes;these same properties raise important questions regarding the currently widespread use of excitotoxins as food additives. Accumulating evidence suggests that excitotoxins endogeneously present in the CNS may play pathogenic roles in human neurological disorders and provides hope that rational therapeutic approaches to such conditions may be developed.
From Dogfish to Dogs: Trimethylamines Protect Proteins from Urea
Authors: Somero GN
Published: December 2017

The accumulation of methylamine solutes to counteract perturbation of proteins by urea seems to be an important and phylogenetically widespread phenomenon. In the renal papilla of the mammalian kidney, the accumulation of methylamines appears to solve two distinct problems. The "osmotic gap" may be largely filled by methylamines and urea, and, because methylamines appear to be accumulated to about one-half the concentration of urea, they are likely to offset fully the influences of urea on intracellular proteins. How the kidney cells accumulate and retain methylamines and how they adjust mehtylamine concentrations int he face of fluctuations in urea levels remain fascinating and important questions for physiologists to resolve.
Brown Adipose Tissue: An Extrathyroidal Source of Triiodothyronine
Authors: Silva JE
Published: December 2017

The role of brown adipose tissue in heat production is well known, but it is a novel concept that this tissue can activate the main secretory product of the thyroid gland, thyroxine, by converting it into the ten times more active triiodothyronine. The enzyme that catalyzes the reaction is present also in other tissues, but it is activated by the sympathetic nervous system only in brown adipose tissue. Thus sympathetic stimulation of brown adipose tissue results in increased production of triiodothyronine and activation of metabolism in other tissues.
The Sauna - Stimulating and Relaxing
Authors: Hanninen O
Published: December 2017

The sauna - a hot air bath - is a centuries old cultural tradition in Finland and is now spreading to fitness centers and private homes around the world. The exposure to hot air at 70-100� C and low humidity for 10-20 minutes causes skin temperature to rise, resulting in heavy sweating and other physiological changes. A major reason for the sauna's continuing popularity is that it leaves the bather with a pleasant feeling of deep relaxation.
Man in Space
Authors: West JB
Published: December 2017

The Challenger disaster focused attention on the hazards as well as the possibilities of man in space. The physiological effects of prolonged weightlessness include important changes in vestibular, bone, muscle, cardiovascular, blood, renal, and pulmonary function. Much has been learned from US and Soviet experiments, but large areas of ignorance remain. Exceptional opportunities for physiological research are provided by Spacelab, a pressurized laboratory planned as a payload of the Space Shuttle.
Capillary Hematokrit - What Does It Mean?
Authors: Duling BR , Desjardins C
Published: December 2017

The hematocrit of capillary blood bears little relation to the hematocrit of arterial blood. Capillary hematocrits are lower than arterial values, and, most importantly, the capillary hematocrit fluctuates in parallel with tissue metabolic activity and the contractile state of the arterioles. This suggests that the capillary hematocrit could be a controlled variable with a central role in the regulation of tissue oxygenation.
Interdigestive Activity in the Gastrointestinal Tract
Authors: Magee DF
Published: December 2017

The empty stomach and intestinal tract show a great deal of apparently spontaneous activity, with regard to both motility and secretion. This intrinsic activity is cyclic and has caused problems for investigators of gastrointestinal physiology because it is difficult to establish a true base line for many experiments.
Paradigms and Concepts in Thermal Regulation of Homeotherms
Authors: Simon E
Published: December 2017

This article challenges the belief in a central role for the hypothalamus in temperature regulation. This concept arose from classical experiments that pointed to the hypothalamus as a central regulator where deep body temperature is monitored, integrating incoming signals and controlling effectors such as shivering, sweating, and panting. More recent experimental evidence requires a much broader view of the integrated neural control system for temperature regulation in homeotherms.
The Physiology of Aldosterone Secretion
Authors: McDougall JG
Published: December 2017

Aldosterone is the major mineralocorticoid hormone of all mammalian species and is only secreted by the zona glomerulosa of the adrenal cortex. The control of aldosterone secretion remains one of the more intriguing problems in the field of endocrinology. The complexities of the system are manyfold, involving multiple stimuli and inhibitors and possibly multiple biosynthetic pathways.
Pulmonary Surfactant: Biochemistry, Physiology, and Pathology
Authors: Bourbon JR , Rieutort M
Published: December 2017

The material that lines the alveoli of the lung, known as pulmonary surfactant, plays a crucial role in lung function. Its composition and biosynthesis are rather well known, but its mechanism of action and its primary role in the etiology of neonatal respiratory distress remain controversial. Surfactant replacement for the treatment of respiratory distress nevertheless appears useful.
Hypertension: Role of the Hypothalamic-Pituitary-Adrenal Axis
Authors: Scoggins BA
Published: December 2017

Blood pressure regulation may be mediated by corticotropin-releasing factor and/or by adrenocorticotropic hormone, by adrenocortical steroids, or by adrenomedullary catecholamines. The interaction between these factors is complex. Catecholamines and central actions of the neuropeptides may be involved in rapid hemodynamic responses to "stress". In contrast, adrenocortical steroids are probably more important in longer-term adaptations of the circulation to prolonged stress.
Diuresis in Mosquitoes: Role of a Natriuretic Factor
Authors: Beyenbach KW , Petzel DH
Published: December 2017

When a mosquito takes in a blood meal that is twice its body weight, flying and easy maneuvering become a problem. To get rid of the extra water, the mosquito produces a copious flow of urine that begins even before the meal has been completed. How is this diuresis controlled?
Sympathetic Control of Intestinal Fluid and Electrolyte Transport
Authors: Sjovall H , Jodal M , Lundgren O
Published: December 2017

The sympathetic efferent innervation of the small intestine contains fibres that increase intestinal net fluid absorption. This pathway seems to be part of the regulatory system for maintaining fluid balance. Knowledge of the mechanism and type of receptors involved may be of interest in the development of new drugs against diarrheal disease.
Skeletal Muscle: A Potential Power Source for Cardiac Assist Devices
Authors: Acker M, A. , Stephenson LW
Published: December 2017

Skeletal muscle has a tremendous capacity for adaptation in increased use, a property that makes in potentially suitable to assist the heart in pumping blood. Heart "ventricles" capable of pumping blood chronically in circulation have been developed based on this concept. Such pumps may some day represent an alternate therapeutic approach to patients with end-stage heart disease or infants with certain congential heart defects.
Taste Transduction and Modulation
Authors: Schiffman SS
Published: December 2017

The application to the tongue of agents that interact with taste cells can tell us a great deal about transduction mechanisms that mediate taste. Separate pathways for Na+ and K+ appear to be part of the transduction mechanisms for the tastes of sodium and potassium salts. Caffeine and other methyl xanthines can potentiate certain tastes;this enhancement may involve the interaction of caffeine with an adenosine receptor. There is also evidence for glutamate and inosine receptors in addition to multiple receptors for sweet and bitter tastes.
Muscle Cells of Hollow Organs
Authors: Murphy RA
Published: December 2017

Muscle cells in hollow organs must shorten and perform work much like skeletal muscle. However, they must also contract tonically to maintain organ dimensions against imposed loads. Vertebrate smooth muscle has a regulatory system involving Ca2+-stimulated cross-bridge phosphorylation that controls not only the number of cross bridges interacting with the thin filament but also controls their cycling rates. Regulation by phosphorylation and dephosphorylation lowers the efficiency of smooth muscle but contributes to a remarkable economy of force maintenance.
Coordination Between Posture and Movement: Why and How?
Authors: Massion J , Dufosse M
Published: December 2017

Posture and movement are two different and often conflicting aspects of motor control. Postural control involves stabilizing a "reference" (joint angle, center, of gravity position) against disturbances exerted by external forces, whereas movement control involves reaching a new position through a trajectory. Voluntary movements tend to disturb posture and equilibrium and are therefore associated with "anticipatory" postural adjustments. This article reviews the coordination between posture and movement.
Novel Specific Inhibitors of Epithelial Phosphate Transport
Authors: Kempson SA
Published: December 2017

The characteristics of phosphate transport across epithelial cell membranes and the influence of hormones and other factors have been studied in detail. Almost no information has emerged about the identity, structure, and biogenesis of the membrane-bound phosphate transporting proteins or how their transport function is regulated by intracellular events. One major difficulty has been the unavailability of a highly specific label for the phosphate transporter.
Normal Aging and the Brain
Authors: Katzman R
Published: December 2017

During normal aging, cognition as measured by intelligence tests is remarkably preserved, although most of the very old show significant slowing of brain processing and mild loss of episodic memory. The neural basis for these changes is poorly understood.
Two Interacting Signal Transduction Pathways Regulate Collecting Duct Water Transport
Authors: Ando Y , Jacobson HR , Breyer MD
Published: December 2017

Receptor-mediated signal transduction occurs through phosphatidylinositol bisphosphate (PIP2) breakdown and activation of adenylate cyclase interacting to regulate cell function. Current studies suggest that hormone-stimulated PIP2 breakdown modulates the classic cyclic AMP-mediated hydrosmotic action of vasopressin through separate mechanisms attributable to activation of protein kinase C, elevation of intracellular Ca2+ concentration, and generation of arachidonate metabolites.
Neuropeptide Y: Sympathetic Cotransmitter and Modulator?
Authors: Lundberg JM , Pernow J , Lacroix JS
Published: December 2017

Neuropeptide Y (NPY) exerts potent vasoconstrictor activity and is coreleased with noradrenaline from sympathetic nerves, mainly on a high degree of activation. It may contribute to the vasoconstriction on high-frequency sympathetic stimulation during control conditions and mediate the long-lasting responses evoked by nerve stimulation in the absence of noradrenaline. NPY enhances the vasomotor effects to noradrenaline and inhibits its release from perivascular nerves. NPY probably is a cotransmitter in sympathetic vascular control.
Gut Immunophysiology: Regulatory Pathways Within a Common Mucosal Immune System
Authors: Castro GA
Published: December 2017

Results of recent investigations on the immunological regulation of gastrointestinal function infer that future considerations of factors that coordinate the physiological behavior of epithelium and smooth muscle must include the role of the mucosal immune system. Implications of such regulation extend to mucosal tissues beyond the alimentary canal.
Regulation of G Protein-Gated K+ Channels
Authors: Kurachi Y
Published: December 2017

GTP-binding proteins (G or N) transduce signals from various membrane receptors to effector systems in the cell membrane. Recently it was shown that G proteins couple a variety of receptors to a K+ channel.
Noninvasive Assessment of Arterial Flow Patterns and Wall Properties in Humans
Authors: Reneman RS , van Merode T , Hoeks APG
Published: December 2017

Multigate pulsed Doppler systems are developed that allow noninvasive, on-line recording of instantaneous velocities simultaneously at various sites along the ultrasound beam and, hence, of velocity profiles and of arterial wall displacement. These systems provide valuable information about flow patterns in arteries and arterial wall properties under normal and pathological circumstances.
Synovial Fluid Exchange - A Case of Flow Through Fibrous Mats
Authors: Levick JR
Published: December 2017

Synovial joints contain a film of lubricating fluid that is maintained by exchange between plasma and joint cavity. Fluid exchange is governed partly by capillary endothelium, but, due to the low hydraulic resistance of the fenestrations, interstitial resistance is important too. Each component contains a mesh work of fibrous elements, which makes "porosity" a more realistic model than traditional pores.
The Paradox of Renal Bicarbonate Reabsorption
Authors: Kiil F
Published: December 2017

A time-honored paradox of renal bicarbonate reabsorption can be understood by realizing that filtered bicarbonate rather than glomerular filtration rate and plasma pH rather than PCO2 are the main determinants of bicarbonate reabsorption.
Acoustic Signals from Skeletal Muscle
Authors: Barry DT
Published: December 2017

Contracting skeletal muscles emit pressure waves that are audible at the skin surface and are easily recorded with standard microphones both in vivo and in vitro. These muscle sounds are an intrinsic component of the contractile mechanism and are produced by mechanical vibrations at the resonant frequency of the muscle. The sounds are useful in measuring force, fatigue, and mechanical properties of muscle.
Significance of Na+-K+ Pump Regulation in Skeletal Muscle
Authors: Clausen T
Published: December 2017

Muscles contain large pools of K+ and Na+-K+pumps and could either flood plasma with K+ or induce a drop in plasma K+ due to rapid intracellular K+ accumulation. Since both events could interfere with cardiac contractile performance, tight regulation of Na+-K+ pump activity and concentration is essential.
Neuronal Processing of Contours
Authors: Von der Heydt R , Peterhans E , Baumgartner G
Published: December 2017

The visual cortex looks at things in a strange way: perception of the white of a sheet of paper is related to activity of the neurons stimulated by its edges, not its surface;contour is a product of a cortical mechanism that integrates various "occlusion cues," not an intensity step that excites local edge detectors.
What Is New in the Chemistry of Endogenous Digitalis-Like Compounds?
Authors: Cloix J-F
Published: December 2017

Methods of measurement of endogenous digitalis-like compounds (EDLC) involved in some pathophysiological conditions are based on biological properties of cardiac glycosides, mainly inhibition of Na-K-ATPase. The origin and putative chemical nature of EDLCs is still questionable and has been reported to be fatty acid, peptide, steroid, or lignan.
Is Carbonic anhydrase Required for Contraction of Skeletal Muscle?
Authors: Geers C , Wetzel P , Gros G
Published: December 2017

An important step in excitation-contraction doupling is release and reuptake of Ca2+ at the sarcoplasmic reticulum membrane, which requires simultaneous transfer of counterions, probably H+. Evidence is provided that a carbonic anhydrase associated with the sarcoplasmic reticulum membrane rapidly generates the H+ necessary for this exchange.
Mammalian Circadian Clock and Its Resetting
Authors: Illnerova H
Published: December 2017

Data on resetting circadian rhythm in melatonin production suggest a complex structure of the underlying pacemaker and explain why the circadian pacemaker functions also as a calendar measuring day length. The pacemaker is entrainable not only by light but by various drugs as well.
ATP Receptor-Operated Ca2+ Influx and Catecholamine Release From Neuronal Cells
Authors: Inoue K , Nakazawa K
Published: December 2017

The physiological function of extracellular ATP was investigated using PC-12 cells as a model neuronal cell. The mechanism of action of ATP proposed is that ATP stimulates P2-purinoceptors, activates Ca2+-permeable cation channels, and causes Ca2+ influx, triggering catecholamine release.
Smooth Muscle: Diversity and Rhythmicity
Authors: Prosser CL
Published: December 2017

Coordinated movements in smooth muscle are brought about by interaction among fibers in varied patterns of rhythmicity. Possible mechanisms of rhythmicity are stretch initiation, ionic fluxes in coupled cycles, endogenously active interstitial cells, glycolytic oscillations, and neural circuits.
Calcium Entry in Nonexcitable Cells: Lessons from Human Platelets
Authors: Sage SO , Mahaut-Smith MP , Rink TJ
Published: December 2017

A rise in cytosolic calcium concentration plays an important role in platelet activation. As well as helping define stimulus-response coupling in these intriguing and clinically important cells, the study of calcium mobilisation in platelets serves as an important model for elucidating calcium signaling mechanisms in general.
The Quest For Water Channels
Authors: Dempster JA , Van Hoek AN , Van Os CH
Published: December 2017

High water permeability of proximal tubules and erythrocytes is due to membrane proteins serving specifically as water channels. Such conclusions stem from volume flow measurements in plasma membrane vesicles and mRNA expression studies in Xenopus oocxytes. Evidence is now emerging that this water channel is a 28-kDa protein which belongs to an ancient channel familiy.
Multiple Site Effects of Extracellular ATP in Cardiac Tissues
Authors: Vassort G , Scamps F , Puceat M , Clement O
Published: December 2017

Before its degradation to adenosine, extracellular ATP released by nerves, or by cardiac cells during ischemia, induces positive inotropy related to stimulation of calcium conductance by P2-purinoceptors. Transiently ATP may also depolarize the cells and trigger arrhythmias by activating a new P3-purinoceptor that requires Mg ions.
Spatiotemporal Aspects of Ca2+ Signaling in Exocrine Acinar Cells
Authors: Dissing S , Gromada JL , Jorgensen NK , Frokjaer-Jensen J , Nauntofte B
Published: December 2017

Digital image processing technique on fura-2-loaded acinar cells from exocrine gland end pieces shows that, on receptor activation, intracellular free Ca2+ concentration rises rapidly at the basolateral and luminal membranes. This is consistent with a model in which K+ channels at basolateral membranes and Cl- channels at luminal membranes are activated simultaneously.
Respiratory Muscle Interaction
Authors: Decramer M
Published: December 2017

Breathing requires a coordinated contraction of different respiratory muscles. During quiet breathing in upright humans, the diaphragm, parasternal intercostals, and scalenes contract and interact to displace the chest wall along its relaxation line. The most important expiratory muscles, triangularis sterni and transversus abdominis, do not contribute to quiet breathing.
Prevention of Programmed Death in Hematopoietic Progenitor Cells by Hematopoietic Growth Factors
Authors: Koury MJ , Bondurant MC
Published: December 2017

Hematopoietic growth factors have been thought to control blood cell production by stimulating proliferation and differentiation of hematopoietic progenitor cells. However, recent studies show that these growth factors prevent programmed death in progenitor cells. A model of hematopoiesis based on prevention of this death by hematopoietic growth factors is presented.
A Protein With a Single Transmembrane Domain Forms an Ion Channel
Authors: Takumi T
Published: December 2017

Isk is a small membrane protein with a single membrane-spanning domain and shows a slow voltage-dependent K+ channel activity. Mutational analyses showed that Isk forms an integral part of the K+ channel itself. Two other proteins have similar properties, suggesting a new group of voltage-dependent channels.
Pulmonary Blood-Gas Barrier: A Physiological Dilemma
Authors: West JB , Mathieu-Costello O
Published: December 2017

The blood-gas barrier needs to be extremely thin for gas exchange, but also immensely strong because the capillary wall stresses become very high during exercise. Failure of the barrier causes high-permeability pulmonary edema or hemorrhage. Avoiding stress failure poses a challenging problem for some animals.
Body Weight Regulation in Humans: The Importance of Nutrient Balance
Authors: Jequier E
Published: December 2017

Body weight regulation depends on the balances of the three macronutrients. Whereas food intake stimulates the oxidation rate of carbohydrate and protein, it inhibits that of fat. Carbohydrate and protein balances are usually achieved within 24 h, whereas fat balance may vary markedly according to fat intake and energy needs.
Actions of Insulin and the IGFs on Bone
Authors: Verhaeghe J , Bouillon R
Published: December 2017

Insulin and insulin-like growth factors (IGF) I and II have receptors in osteoblastic cells and stimulate both their proliferation and activity in vitro. Insulin probably has no effect on osteoblast precursors. Osteoclast formation is induced by IGF-I in vitro, and IGF-I may affect bone (re)modeling in vivo.
Pituitary-Adrenocortical Function and Experimental Inherited Hypertension: Perspectives of Permanent Correction
Authors: Naumenko EV
Published: December 2017

Changes of pituitary-adrenocortical function in rats with inherited hypertension are associated with alteration of the brain noradrenergic mechanism regulating both arterial blood pressure and the adrenocortical system. A way of permanent restoration of blood pressure and adrenocortical function by interference into norepinephrine metabolism in early ontogenesis is discovered.
ATP-Induced K+ Current Oscillation in Megakaryocytes: A Unique Purinoceptor
Authors: Akaike N , Uneyama H
Published: December 2017

Megakaryocytes respond to externally applied ATP and ADP, showing a periodic K+ current that reflects oscillation in cytoplasmic calcium concentration ([Ca2+] i). The agonist selectivity of the purinoceptor on the megakaryocyte is unique. In addition, the intracellular mechanism of [Ca2+]i oscillation was investigated, and a model is proposed.
Hypoxia in the Uterus
Authors: Wray S
Published: December 2017

Uterine contractions are so powerful during labor that they cause hypoxia. This article examines effects hypoxia has on the ability of the uterus to contract and its relevance to clinical cases of dystocia, i.e., weak contractions, which often lead to cesarean section.
Cytokines in the Healthy and Diseased Brain
Authors: Schobitz B , Holsboer F , Ron de Kloet E
Published: December 2017

Under noninflammatory conditions, interleukin-1 and interleukin-6 are located in neurons and glial cells of discrete brain regions;they appear to be expressed at a constant level during peripheral immune challenges. After severe brain damage, however, synthesis in neurons and glia is increased with stimulation of immune reactions, gliosis, and neuronal growth.
Vomiting - Its Ins and Outs
Authors: Grelot L , Miller AD
Published: December 2017

Vomiting, a highly complex stereotyped behavior, is generated primarily by respiratory muscles. The anatomic organization and pharmacology of input pathways and central mechanisms coordinating the musculature to produce vomiting have become better understood. However, the precise location of the medullary neuronal network responsible for this behavior is still under investigation.
Role of Renal Nerves in Edema Formation
Authors: DiBona GF
Published: December 2017

Once viewed as physiologically insignificant by no less an authority than Homer Smith, the renal nerves have emerged as a physiologically important regulator of renal tubular sodium reabsorption. Increased renal sympathetic nerve activity contributes significantly to the renal sodium retention in edema-forming states.
Renal Proximal Tubule Response to Acid
Authors: Alpern RJ , Yamaji Y , Amemiya M , Cano A , Preisig PA , Miller RT , Moe OW
Published: December 2017

Changes in dietary acid and blood pH lead to adaptations in key enzymes and transport proteins of the renal proximal tubule that tend to return blood pH to normal. The mechanisms responsible, as well as acid-regulated signaling pathways that may effect these responses, are reviewed.
Using Antibodies to unwire the Sympathetic Nervous System
Authors: Brimijoin S
Published: December 2017

Antibodies to surface antigens can target specific neuronal populations for destruction, sometimes with surprising results. In rats, for example, antibodies to the widely distributed synaptic enzyme acetylcholinesterase cause selective ablation of preganglionic sympathetic terminals. This phenomenon is relevant to autonomic disorders of human patients and may also yield insights into normal autonomic physiology.
The Surface of the Heart Leaks Oxygen
Authors: Loiselle DS , van Beek JHGM , Mawson DA , Hunter PJ
Published: December 2017

The rate of oxygen consumption of the heart is classically measured using the Fick principle. Uncritical application of this principle can cause errors of measurement, particularly when estimating cardiac basal metabolic rate. Consideration of these errors leads to a model that supports modern notions of oxygen exchange in perfused tissue.
Annexins: Novel Ca2+-Dependent Regulators of Membrane Function
Authors: Kaetzel MA , Dedman JR
Published: December 2017

The annexins are a family of Ca2+-dependent membrane binding proteins that have been shown to regulate ion conductances, aggregate vesicles and the cytoskeleton, inhibit phospholipase A2, and inhibit blood coagulation. The annexins represent a unique mechanism of cellular regulation by modifying membrane functions in a Ca2+-dependent manner.
How and Why Cells Make Superoxide: The "Phagocytic" NADPH Oxidase
Authors: Maly FE , Schurer-Maly CC
Published: December 2017

The phagocyte enzyme NADPH oxidase generates superoxide essential for antimicrobial defense;its genetic defects cause the immunodeficiency disorder chronic granulomatous disease. B lymphocytes and certain other nonphagocytes also express NADPH oxidase. Molecular approaches allow new ways to study the enzyme and promise to uncover why nonphagocytic cells express NADPH oxidase.
The In Vitro Motility Assay: A Window Into the Myosin Molecular Motor
Authors: Warshaw DM
Published: December 2017

Muscular contraction is powered by myosin, a molecular motor, that derives its energy from hydrolysis of ATP as it interacts with actin. With the development of the in vitro motility assay, molecular events that couple ATP hydrolysis to mechanical work can be probed at the level of a single myosin molecular motor.
Role of Nitric Oxide in the Control of Sodium Excretion
Authors: Salazar FJ , Llinas MT
Published: December 2017

Recent findings suggest that nitric oxide plays a pivotal role in maintaining homeostasis of the extracellular volume. This short review provides evidence supporting the important role of nitric oxide in the regulation of sodium excretion during increments of arterial pressure and in response to acute and prolonged increments of extracellular volume.
Alpha Rhythms in the Brain: Functional Correlates
Authors: Basar E , Schurmann M
Published: December 2017

Experimental evidence suggests a functional significance of electroencephalographic (EEG) alpha rhythms. Event-related, evoked, and induced alpha rhythms may have functional correates in primary sensory processing and preparatory processes. These results are in accord with the view that spontaneous and induced EEG alpha rhythms have quasi-deterministic properties.
Activation and Supply of Channels and Pumps by Aldosterone
Authors: Verrey F , Beron J
Published: December 2017

Mineralocorticoid and glucocorticoid hormones stimulate sodium reabsorption across target epithelia by modulating the transcription rate of a cell-specific set of genes. Unidentified regulated gene products mediate an early activation of preexisting sodium channels and pumps. In a later phase, the supply of proteins belonging to the sodium-transport machinery is increased.
Species Specificity of the Primate Growth Hormone Receptor
Authors: Goodman HM , Frick GP , Souza S
Published: December 2017

Unlike other mammals, primates can respond to growth hormone (GH) only of primate origin. This species specificity results from the incompatibility of the positively charged arginine found uniquely in primate GH receptors with histidine in the GH molecules in all nonprimates in place of the aspartate found in primate GHs.
Gastrin Processing: From Biochemical Obscurity to Unique Physiological Actions
Authors: Dickinson CJ , Seva C , Yamada T
Published: December 2017

Posttranslational processing is essential for the biological activation of many peptide hormones. Only fully processed and amidated gastrin, a peptide secreted by the stomach, stimulates acid secretion. However, both amidated gastrin and its glycine-extended precursor stimulate cellular proliferation through selective receptors, suggesting that posttranslational processing is critical to gastrointestinal physiology.
Quality Control of Protein Folding: Participation in Human Disease
Authors: Choudhury P , Liu Y , Sifers RN
Published: December 2017

Protein folding and quality control machinery prevent deployment of nonfunctional molecules throughout the cell and can participate in the molecular pathogenesis of several human diseases.
Adaptation of Mitochondrial Gene Expression to Changing Cellular Energy Demands
Authors: Wiesner RJ
Published: December 2017

Training of skeletal muscle, as well as thyroid and steroid hormones, stimulates mitochondrial biogenesis, which requires regulation of genes encoded on nuclear and mitochondrial DNA. Imbalances between energy demand and supply increase mitochondrial gene expression via as yet unknown metabolic signals involving transcription factors in the sense of a negative feedback loop.
Nature's KATP-Channel Knockout
Authors: Dunne MJ , Aynsley-Green A , Lindley KJ
Published: December 2017

We describe here how ion-channel dysfunction in b-cells is associated with the pathogenesis of a potentially lethal condition in newborn children and early infancy. We review how nature's KATP-channel knockout has important medical implications and how key lessons in physiology can be learned from studies of rare diseases.