Leonardo NICOLA SIRI - Academia.edu (original) (raw)
Papers by Leonardo NICOLA SIRI
BMC Cardiovascular Disorders, Jan 9, 2006
Background: The occurrence of variations in the spectrum of cardiovascular disease between differ... more Background: The occurrence of variations in the spectrum of cardiovascular disease between different regions of the world and ethnic groups have been the subject of great interest. This study report the 24-h variation of myocardial infarction (MI) occurrence in patients recruited from CCU located in Argentina and Uruguay. Methods: A cohort of 1063 patients admitted to the CCU within 24 h of the onset of symptoms of an acute MI was examined. MI incidence along the day was computed in 1 h-intervals. Results: A minimal MI incidence between 03:00 and 07:00 h and the occurrence of a first maximum between 08:00 and 12:00 h and a second maximum between 15:00 and 22:00 h were verified. The best fit curve was a 24 h cosinor (acrophase ~ 19:00 h, accounting for 63 % of variance) together with a symmetrical gaussian bell (maximum at ~ 10:00 h, accounting for 37 % of variance). A similar picture was observed for MI frequencies among different excluding subgroups (older or younger than 70 years; with or without previous symptoms; diabetics or non diabetics; Q wave-or non-Q wave-type MI; anterior or inferior MI location). Proportion between cosinor and gaussian probabilities was maintained among most subgroups except for older patients who had more MI at the afternoon and patients with previous symptoms who were equally distributed among the morning and afternoon maxima. Conclusion: The results support the existence of two maxima (at morning and afternoon hours) in MI incidence in the Argentine and Uruguayan population.
Biological Rhythm Research, Feb 1, 2008
In a recent study we examined the circadian rhythmicity of acute myocardial infarction (MI) onset... more In a recent study we examined the circadian rhythmicity of acute myocardial infarction (MI) onset in a cohort of 1063 patients admitted to the CCU within 24 h of the onset of symptoms (D’Negri et al. 2006). A minimal MI incidence between 03:00 and 07:00 h and the occurrence of a first maximum between 08:00 and 12:00 h and a second maximum between 15:00 and 22:00 h were reported. The best fit curve was a 24 h cosinor (acrophase *19:00 h, accounting for 63% of variance) together with a symmetrical Gaussian bell (maximum at *10:00 h, accounting for 37% of variance (D’Negri et al. 2006). A similar picture was observed for MI frequencies among different subgroups (older or younger than 70 years; with or without previous symptoms; diabetics or non-diabetics; Q waveor non-Q wave-type MI; anterior or inferior MI location). The proportion between cosinor and Gaussian probabilities was maintained among most subgroups. We wish to report here the differences we observed when we applied a quartile partition to analyze the same data. To quantify the time dependence of MI incidence, we followed a current practice in the field (Zoble & Deedwania 1997) by dividing the day into quartiles of equal duration, i.e., 00:01 – 06:00 h, 06:01 – 12:00 h, 12:01 – 18:00 h and 18:01 – 24:00 h bands (‘‘0 – 24 h partition’’). In order to assess whether the distribution of MI incidence was affected by the way the quartile partition was made, we compared the results with those obtained by delaying for 2 h the quartile partition, i.e. 02:01 – 08:00 h, 08:01 – 14:00 h, 14:01 – 20:00 h and 20:01 – 02:00 h (‘‘2 – 26 h partition’’) (Figure 1). Observed cases of MI occurrence within each time band were counted and expressed as percentage incidence in each quartile. The total population, and also the excluding subgroups, were analyzed. We only show here as an example the comparison of MI incidence between the anterior and inferior location. Differing from what we reported in the same population when partition of the day in 1-h intervals was used (D’Negri et al. 2006), only one maximum was found for all groups by using
Journal of Physics: Conference Series, 2007
A visual aid to pace self-controlled respiratory cycles in humans is presented. Respiratory manoe... more A visual aid to pace self-controlled respiratory cycles in humans is presented. Respiratory manoeuvres need to be accomplished in several clinic and research procedures, among others, the studies on Heart Rate Variability. Free running respiration turns to be difficult to correlate with other physiologic variables. Because of this fact, voluntary self-control is asked from the individuals under study. Currently, an
Psychiatry and Neuroscience Update, 2018
It is accepted that several biological (genetic, physiological), psychological (personality, mood... more It is accepted that several biological (genetic, physiological), psychological (personality, mood), social (family, work), and ecological (living environment) factors interact to allow the preservation of quality of life and health. The autonomic nervous system (ANS) is structural and rhythmically interfaced between forebrain, internal, and external environments, to regulate energy, matter, and information exchanges, thus expressing the biopsychosocial nature of the individual. During last year strong evidence has been produced that demonstrates the influence of the ANS into beat-to-beat fluctuations of cardiac heart period. Stephen Hales was the first in describing the association between respiratory cycle and heart rate. However, it was not until the second half of the twentieth century that subtle relations between ANS activity and heart rate variability (HRV) were systematically explored in several physiological conditions, including physical activity, sleep, and stress. In addition, autonomic imbalance may configure a final common pathway to increased morbidity and mortality from a host of physical, such as metabolic disorders and cardiovascular disease, and psychological conditions, like anxiety or depression. This chapter will focus on the physiological mechanisms underlying HRV, the methods for assessing it and the information that has provided about ANS activity in certain physiological and pathological situations.
Pfl�gers Archiv European Journal of Physiology, 1989
Two types of fibres were characterized in the cruralis muscle of the toad using electrophysiologi... more Two types of fibres were characterized in the cruralis muscle of the toad using electrophysiological techniques: the slow and the fast fibres. Five to ten slow fibres were easily identified on the inner face of this muscle. The cruralis slow fibres developed the ability to produce action potentials 40 days after the sciatic nerve was transected at the hip level, while the slow fibres of the pyriformis muscle showed a latent period of 17 days after the same surgical treatment. However, when in addition to this procedure the nerve was transected at the point where it enters the muscle but without damaging the slow fibres, the latency was about 20 days. The slow fibres of the cruralis muscle maintained in organ culture developed the ability to produce action potentials in 24 days. During the winter the slow fibres of in vivo denervated cruralis and pyriformis muscles did not develop the ability to produce regenerative responses. More-over organ-cultured cruralis muscles taken from winter toads showed this same inability. These results further support the idea that the excitability of slow fibres is under the control of a neural factor rather than of activity. The seasonal dependence points to the fact that the metabolic state of the muscle is of crucial importance in determining the development of excitability of slow fibres.
Journal of Physics: Conference Series, 2007
In this work, a simulator of surface electrocardiogram recorded signals (ECG) is presented. The d... more In this work, a simulator of surface electrocardiogram recorded signals (ECG) is presented. The device, based on a microcontroller and commanded by a personal computer, produces an analog signal resembling actual ECGs, not only in time course and voltage levels, but also in source impedance. The simulator is a useful tool for electrocardiograph calibration and monitoring, to incorporate as well in educational tasks and in clinical environments for early detection of faulty behaviour.
The Journal of Physiology, 1983
1. Voltage-clamp experiments using the three micro-electrode method were performed to study the t... more 1. Voltage-clamp experiments using the three micro-electrode method were performed to study the temperature dependence of the calcium current ICa in intact twitch skeletal muscle fibres of the frog. Contraction was blocked by recording in hypertonic sucrose solutions. 2. For depolarizations smaller than 0 mV the decay of the transient, slow, inward current, recorded in the presence of external tetraethylammonium (TEA+) and by replacing Cl-for CH3SO3-, followed a complex time course. For larger depolarizations, after the initial inward current, there was a prominent, slow, outward current which showed two phases: after reaching a peak (time to peak 1-0 sec, peak amplitude 20-50 #sA/cm2 at 20 mV) it slowly declined to a steady level in about 2-3 see at 23 'C. 3. The inward current was greatly reduced or abolished by the adding of2 mM-Cd2+ or by replacing external Ca2+ with Mg2+. The amplitude and time course of slow, outward currents were not obviously modified by replacing Ca2+ with Mg2+, having the two described phases. However, in the presence of Cd2+ the first transient phase of the outward current was not detected and only outward currents slowly increasing to a steady level were observed. 4. Reliable ICa records were obtained by further blocking K+ outward currents by incubating the muscles in a K+-free TEA+and Cs+-containing solution prior to experiments. Tubular space clamp was improved by recording ICa from small fibres with 20-30 jsm radius. 5. The decay phase of ICa under a maintained depolarization in incubated muscles was fitted by a single exponential. The corresponding rate constant determined between 12 and 24 OC strongly depended on temperature, as expected for a gating process. The values for the activation energy and the corresponding Q10 (calculated for a 10-20 0C transition) were respectively: 17-5 + 1'0 kcal/mole and 2-9 + 0-2 at 0 mV, and 18-0 + 1-5 kcal/mole and 3 0 + 0-3 at-20 mV. 6. The activation phase of Ica, analysed following the ma2h Hodgkin-Huxley kinetic model, showed a similar temperature dependence with a Q10 of 3-0 + 0 3. The * Recipient of a fellowship from CONACyT, Mexico.
The Journal of Physiology, 1984
1. The decay of the Ca2+ current (ICa) during a maintained depolarization was studied in intact t... more 1. The decay of the Ca2+ current (ICa) during a maintained depolarization was studied in intact twitch skeletal muscle fibres of Rana pipiens and Rana moctezuma with the three-micro-electrode voltage-clamp technique. 2. ICa was recorded at 23 TC, after blocking K+ currents, in TEA methanesulphonate saline with 10 mM-Ca2+ made hypertonic by adding 350 mM-sucrose. 3. In two-pulse experiments, ICa during the test pulse was reduced to about 80 % (R. pipiens) or 50 % (R. moctezuma) of the control value, without any detectable inward ICa during 7 s conditioning pre-pulses. 4. The experimental points of the steady-state inactivation curve (h.) were fitted to hoo = (1 +exp ((Em-Vh)/kh))-, where Em is the membrane potential and with Vh =-33 + 3 mV and kh = 6 +1 mV for R. pipiens, and Vh =-44 + 3 mV and kh = 9-5 + ±10 mV for R. moctezuma. 5. The rate constant of decay for inactivated currents (range-8 to-47 mA cm3) and for control currents (range-23 to-62 mA cm-3), was independent of Ica amplitude. The average rate constant of decay at 0 mV was 118 + 002 s-1 (66). 6. These results indicate that in intact fibres under hypertonic solution Ica decay can be explained by a voltage-dependent inactivation process and not by depletion of tubular Ca2+. The absence of depletion could be due to a large fractional tubular volume or to the presence of a Ca2+ pump in the tubular system. INTRODUCTION Voltage-clamp experiments in frog skeletal muscle fibres have shown that Ca2+ current (Ica) spontaneously decays during a maintained depolarization (Beaty &
The Journal of Physiology, 1980
1. Current and voltage clamp experiments were carried out on frog skeletal muscle fibres. For vol... more 1. Current and voltage clamp experiments were carried out on frog skeletal muscle fibres. For voltage clamp, the three micro-electrode technique near the fibre end was used. 2. Calcium spikes and currents were recorded in TEA sulphate saline. The addition of 400 mM-glycerol did not appreciably modify them. 3. Muscle fibres were detubulated with the glycerol method. They showed sodium propagating action potentials, with sodium and potassium currents of expected amplitudes. 4. Calcium spikes and currents were reduced or abolished in detubulated muscle fibres. 5. An analysis of fibre capacitance showed a linear correlation between the remaining ICa and the degree of electric discontinuity between the transverse tubular system and the surface membrane. 6. These results indicate that ICa is mainly located in the transverse tubular system. This localization is compatible with some role during mechanical activation.
The Mechanism of Gated Calcium Transport Across Biological Membranes, 1981
Neuropsychobiology, 1996
Electrodermal responses in the facial region of freely moving rats were recorded bilaterally. Aft... more Electrodermal responses in the facial region of freely moving rats were recorded bilaterally. After a nociceptive stimulus (ammonia vapor exposure), the response (a transient negative potential followed by a longer-lasting positive potential) attained a similar amplitude on both sides. Surgical sympathetic denervation of facial skin by ipsilateral superior cervical ganglionectomy (SCGx) significantly decreased the electrodermal response. When an inferior cervical ganglionectomy was performed in addition to SCGx, a further decrease in electrodermal response was observed. Pretreatment of unilaterally SCGx rats with atropine blunted the electrical response in the control side to levels similar to those found in the SCGx side. Treatment with phenoxybenzamine or propranolol was ineffective. Skin potential responses were measured in adult rats administered with clomipramine from the 8th to the 21st day of life and exhibiting a long-lasting syndrome resembling human depression. Clomipramine-injected rats developed larger skin potential responses to sound stimulation than controls while responses to ammonia vapor were similar in both groups, as well as the habituation rate after repetitive exposure to ammonia vapor. The results indicate that some of the altered electrodermal responses found in depressed patients are detectable in the clomipramine animal model of endogenous depression.
Neuropediatrics, 2010
Autosomal recessive hereditary spastic paraplegia with thinning of the anterior corpus callosum (... more Autosomal recessive hereditary spastic paraplegia with thinning of the anterior corpus callosum (ARHSP-TCC) due to mutations in SPG11 on chromosome 15q (MIM610844) is the single most common cause of ARHSP. It is characterized by slowly progressive paraparesis and peripheral neuropathy. Although cognitive impairment, sometimes diagnosed as mental retardation, is an almost invariable feature, the extent and specific neuropsychological features are not fully understood. We report a comprehensive neuropsychological assessment in two ARHSP-TCC patients harbouring mutations in SPG11. A specific impairment in executive functions occurring even before cognitive decline, may be considered the core of the neuropsychological profile of patients harbouring mutations in SPG11.
Muscle & Nerve, 1993
The properties of singles K+ channels in normal and denervated muscles were compared using the "p... more The properties of singles K+ channels in normal and denervated muscles were compared using the "patch-clamp" technique. Single channels were recorded from vesicles obtained by stretching bundles of normal and denervated extensor digitorium longus (EDL) muscles. The most frequently observed channel in normal muscles was a high conductance (266 pS) Ca+ +activated K+ channel. Although channel density, as estimated by patch recording, showed a significant decrease in denervated muscles, no differences were found in conductance and gating properties. Another voltage-dependent K+ channel (81 pS) was only recorded from normal muscles, but never from denervated ones. In addition, a 35 pS conductance was recorded from both normal and denervated fibers. This channel displayed neither voltage dependence nor sensitivity to tetraethylammonium (TEA). In contrast, another TEAinsensitive (16 pS) channel was recorded only from denervated muscles. We conclude that denervation induces significant changes in the distribution and expression of K+ channels in mammalian skeletal muscles.
Journal of Psychosomatic Research, 2004
To determine whether depression is associated with cardiac autonomic alterations in elderly patie... more To determine whether depression is associated with cardiac autonomic alterations in elderly patients with recent acute coronary syndromes (ACSs). Cross-sectional study on the association between a major depressive episode or isolated depressive symptoms (21-item Hamilton depression score) and heart rate variability abnormalities in 56 adults (31 women, 55%) 60 years of age and older with a recent (24-72 h) myocardial infarction (MI) or unstable angina (UA). Spectral and nonspectral parameters of respiratory sinus arrhythmia, indicative of parasympathetic activity on the heart, were decreased in patients with depression (high-frequency heart rate variability [log ms(2)] 2.12+/-0.4 vs. 2.52+/-0.5, P=.024; pNN50 [%] 1+/-2 vs. 9+/-15, P=.006; and rMSNN [ms] 16+/-6 vs. 28+/-22, P=.009). Also, high-frequency heart rate variability decreased with increasing depressive symptom severity. In a sample of older adults suffering from ACSs, depression was associated with impaired parasympathetic control of the heart.
Journal of Neurochemistry, 2008
The diurnal variations and photic regulation of cyclic AMP and melatonin content in golden hamste... more The diurnal variations and photic regulation of cyclic AMP and melatonin content in golden hamster retina were studied. Both parameters showed significant diurnal variations with maximal values at night. Light exposure during the night inhibited retinal cyclic AMP and melatonin levels, whereas exposure to darkness during the day significantly increased cyclic AMP and melatonin content. Incubation with melatonin of retinas excised at different intervals indicated that the methoxyindole inhibited cyclic AMP accumulation in a time-dependent manner. The inhibitory effect of melatonin at 2400 h and at noon showed a threshold concentration of 1 and 10 pM, respectively. At 0400 h melatonin did not affect cyclic AMP accumulation. The results indicate a diurnal variability of retinal cyclic AMP and melatonin content in hamsters, mainly influenced by a photic stimulus. Cyclic AMP could be a putative second messenger for melatonin action in golden hamster retina.
Journal of Cellular Physiology, 1988
Slow Ca-action potentials (CaAP) were studied in normal human skeletal muscle fibers obtained dur... more Slow Ca-action potentials (CaAP) were studied in normal human skeletal muscle fibers obtained during surgery (fibers with both ends cut). Control studies also were carried out with intact as well as cut rat skeletal muscle fibers. Experiments were performed in hypertonic CI-free saline with 10 or 84 m M Ca and K-channel blockers; muscles were preincubated in a saline containing Cs and tetraethylammonium. A current-clamp technique with two intracellular microelectrodes was used. In human muscle, 14.5% of the fibers showed fully developed CaAPs, 21 % displayed nonregenerative Ca responses, and 64.5% showed only passive responses; CaAPs were never observed in 10 m M Ca. In rat muscle, nearly 90% of the fibers showed CaAPs, which were not affected by the cut-end condition. Human and rat muscle fibers had similar membrane potential and conductance in the resting state. In human muscle (22-32" C, 84 m M Ca), the threshold and peak potential during a CaAP were + 26 k 6 mV and + 70 ? 3 mV, respectively, and the duration measured at threshold level was 1.7 2 0.5 sec. In rat muscle, the duration was four times longer. During a CaAP, membrane conductance was assumed to be a leak conductance in parallel with a Ca and a K conductance. In human muscle (22-32" C, 84 m M Ca, 40 p m fiber diameter), values were 0.4 2 0.1 pS, 1.1 f 0.7 p,S, and 0.9 * 0.4 p,S, respectively. Rat muscle (22-24" C, 84 m M Ca) showed leak and K conductances similar to those found in human fibers. Ca-conductance in rat muscle was double the values obtained in human muscle fibers. Ca-dependent action potentials have been observed in mammalian muscle, when C1 was replaced by a
Journal of Cellular Physiology, 1990
slow Ca-dependent action potentials were studied in skeletal muscle fibers from different Neuromu... more slow Ca-dependent action potentials were studied in skeletal muscle fibers from different Neuromuscular Diseases (NMD). Byopsies were obtained from: 3 myopathies [Fascioscapulohumeral Dystrophy (FSH) and Polymyositis (PM)], 6 patients with other diseases (CD) [Amyotrophic Lateral Sclerosis (ALS), Central Core Disease, Mitochondria1 Myopathy, Polyneuritis (PN), von Eulenberg's Paramyotonia], and 8 normal control muscles. Experiments were carried out in muscle fibers under current-clamp conditions. Membrane currents other than Ca ones were abolished or greatly diminished. Muscle fibers produced any of 3 types of responses, when stimulated by depolarizing pulses: fully developed Ca-action potentials (CaAP), abortive non-regenerative Ca responses (NrR), or only capacitive passive responses (WK). The 3 types of responses were not dependent on the basal conditions of the fibers. The frequency of observation of CaAPs was significantly higher in myopathic disease. In rnyopathies, 46% of the muscle fibers had CaAPs, while only 22% of fibers from CD and 15% of the fibers from normal muscles showed CaAPs. N o differences were observed in the resting constants as well as in the CaAPs parameters between normal and diseased muscle fibers.
BMC Cardiovascular Disorders, Jan 9, 2006
Background: The occurrence of variations in the spectrum of cardiovascular disease between differ... more Background: The occurrence of variations in the spectrum of cardiovascular disease between different regions of the world and ethnic groups have been the subject of great interest. This study report the 24-h variation of myocardial infarction (MI) occurrence in patients recruited from CCU located in Argentina and Uruguay. Methods: A cohort of 1063 patients admitted to the CCU within 24 h of the onset of symptoms of an acute MI was examined. MI incidence along the day was computed in 1 h-intervals. Results: A minimal MI incidence between 03:00 and 07:00 h and the occurrence of a first maximum between 08:00 and 12:00 h and a second maximum between 15:00 and 22:00 h were verified. The best fit curve was a 24 h cosinor (acrophase ~ 19:00 h, accounting for 63 % of variance) together with a symmetrical gaussian bell (maximum at ~ 10:00 h, accounting for 37 % of variance). A similar picture was observed for MI frequencies among different excluding subgroups (older or younger than 70 years; with or without previous symptoms; diabetics or non diabetics; Q wave-or non-Q wave-type MI; anterior or inferior MI location). Proportion between cosinor and gaussian probabilities was maintained among most subgroups except for older patients who had more MI at the afternoon and patients with previous symptoms who were equally distributed among the morning and afternoon maxima. Conclusion: The results support the existence of two maxima (at morning and afternoon hours) in MI incidence in the Argentine and Uruguayan population.
Biological Rhythm Research, Feb 1, 2008
In a recent study we examined the circadian rhythmicity of acute myocardial infarction (MI) onset... more In a recent study we examined the circadian rhythmicity of acute myocardial infarction (MI) onset in a cohort of 1063 patients admitted to the CCU within 24 h of the onset of symptoms (D’Negri et al. 2006). A minimal MI incidence between 03:00 and 07:00 h and the occurrence of a first maximum between 08:00 and 12:00 h and a second maximum between 15:00 and 22:00 h were reported. The best fit curve was a 24 h cosinor (acrophase *19:00 h, accounting for 63% of variance) together with a symmetrical Gaussian bell (maximum at *10:00 h, accounting for 37% of variance (D’Negri et al. 2006). A similar picture was observed for MI frequencies among different subgroups (older or younger than 70 years; with or without previous symptoms; diabetics or non-diabetics; Q waveor non-Q wave-type MI; anterior or inferior MI location). The proportion between cosinor and Gaussian probabilities was maintained among most subgroups. We wish to report here the differences we observed when we applied a quartile partition to analyze the same data. To quantify the time dependence of MI incidence, we followed a current practice in the field (Zoble & Deedwania 1997) by dividing the day into quartiles of equal duration, i.e., 00:01 – 06:00 h, 06:01 – 12:00 h, 12:01 – 18:00 h and 18:01 – 24:00 h bands (‘‘0 – 24 h partition’’). In order to assess whether the distribution of MI incidence was affected by the way the quartile partition was made, we compared the results with those obtained by delaying for 2 h the quartile partition, i.e. 02:01 – 08:00 h, 08:01 – 14:00 h, 14:01 – 20:00 h and 20:01 – 02:00 h (‘‘2 – 26 h partition’’) (Figure 1). Observed cases of MI occurrence within each time band were counted and expressed as percentage incidence in each quartile. The total population, and also the excluding subgroups, were analyzed. We only show here as an example the comparison of MI incidence between the anterior and inferior location. Differing from what we reported in the same population when partition of the day in 1-h intervals was used (D’Negri et al. 2006), only one maximum was found for all groups by using
Journal of Physics: Conference Series, 2007
A visual aid to pace self-controlled respiratory cycles in humans is presented. Respiratory manoe... more A visual aid to pace self-controlled respiratory cycles in humans is presented. Respiratory manoeuvres need to be accomplished in several clinic and research procedures, among others, the studies on Heart Rate Variability. Free running respiration turns to be difficult to correlate with other physiologic variables. Because of this fact, voluntary self-control is asked from the individuals under study. Currently, an
Psychiatry and Neuroscience Update, 2018
It is accepted that several biological (genetic, physiological), psychological (personality, mood... more It is accepted that several biological (genetic, physiological), psychological (personality, mood), social (family, work), and ecological (living environment) factors interact to allow the preservation of quality of life and health. The autonomic nervous system (ANS) is structural and rhythmically interfaced between forebrain, internal, and external environments, to regulate energy, matter, and information exchanges, thus expressing the biopsychosocial nature of the individual. During last year strong evidence has been produced that demonstrates the influence of the ANS into beat-to-beat fluctuations of cardiac heart period. Stephen Hales was the first in describing the association between respiratory cycle and heart rate. However, it was not until the second half of the twentieth century that subtle relations between ANS activity and heart rate variability (HRV) were systematically explored in several physiological conditions, including physical activity, sleep, and stress. In addition, autonomic imbalance may configure a final common pathway to increased morbidity and mortality from a host of physical, such as metabolic disorders and cardiovascular disease, and psychological conditions, like anxiety or depression. This chapter will focus on the physiological mechanisms underlying HRV, the methods for assessing it and the information that has provided about ANS activity in certain physiological and pathological situations.
Pfl�gers Archiv European Journal of Physiology, 1989
Two types of fibres were characterized in the cruralis muscle of the toad using electrophysiologi... more Two types of fibres were characterized in the cruralis muscle of the toad using electrophysiological techniques: the slow and the fast fibres. Five to ten slow fibres were easily identified on the inner face of this muscle. The cruralis slow fibres developed the ability to produce action potentials 40 days after the sciatic nerve was transected at the hip level, while the slow fibres of the pyriformis muscle showed a latent period of 17 days after the same surgical treatment. However, when in addition to this procedure the nerve was transected at the point where it enters the muscle but without damaging the slow fibres, the latency was about 20 days. The slow fibres of the cruralis muscle maintained in organ culture developed the ability to produce action potentials in 24 days. During the winter the slow fibres of in vivo denervated cruralis and pyriformis muscles did not develop the ability to produce regenerative responses. More-over organ-cultured cruralis muscles taken from winter toads showed this same inability. These results further support the idea that the excitability of slow fibres is under the control of a neural factor rather than of activity. The seasonal dependence points to the fact that the metabolic state of the muscle is of crucial importance in determining the development of excitability of slow fibres.
Journal of Physics: Conference Series, 2007
In this work, a simulator of surface electrocardiogram recorded signals (ECG) is presented. The d... more In this work, a simulator of surface electrocardiogram recorded signals (ECG) is presented. The device, based on a microcontroller and commanded by a personal computer, produces an analog signal resembling actual ECGs, not only in time course and voltage levels, but also in source impedance. The simulator is a useful tool for electrocardiograph calibration and monitoring, to incorporate as well in educational tasks and in clinical environments for early detection of faulty behaviour.
The Journal of Physiology, 1983
1. Voltage-clamp experiments using the three micro-electrode method were performed to study the t... more 1. Voltage-clamp experiments using the three micro-electrode method were performed to study the temperature dependence of the calcium current ICa in intact twitch skeletal muscle fibres of the frog. Contraction was blocked by recording in hypertonic sucrose solutions. 2. For depolarizations smaller than 0 mV the decay of the transient, slow, inward current, recorded in the presence of external tetraethylammonium (TEA+) and by replacing Cl-for CH3SO3-, followed a complex time course. For larger depolarizations, after the initial inward current, there was a prominent, slow, outward current which showed two phases: after reaching a peak (time to peak 1-0 sec, peak amplitude 20-50 #sA/cm2 at 20 mV) it slowly declined to a steady level in about 2-3 see at 23 'C. 3. The inward current was greatly reduced or abolished by the adding of2 mM-Cd2+ or by replacing external Ca2+ with Mg2+. The amplitude and time course of slow, outward currents were not obviously modified by replacing Ca2+ with Mg2+, having the two described phases. However, in the presence of Cd2+ the first transient phase of the outward current was not detected and only outward currents slowly increasing to a steady level were observed. 4. Reliable ICa records were obtained by further blocking K+ outward currents by incubating the muscles in a K+-free TEA+and Cs+-containing solution prior to experiments. Tubular space clamp was improved by recording ICa from small fibres with 20-30 jsm radius. 5. The decay phase of ICa under a maintained depolarization in incubated muscles was fitted by a single exponential. The corresponding rate constant determined between 12 and 24 OC strongly depended on temperature, as expected for a gating process. The values for the activation energy and the corresponding Q10 (calculated for a 10-20 0C transition) were respectively: 17-5 + 1'0 kcal/mole and 2-9 + 0-2 at 0 mV, and 18-0 + 1-5 kcal/mole and 3 0 + 0-3 at-20 mV. 6. The activation phase of Ica, analysed following the ma2h Hodgkin-Huxley kinetic model, showed a similar temperature dependence with a Q10 of 3-0 + 0 3. The * Recipient of a fellowship from CONACyT, Mexico.
The Journal of Physiology, 1984
1. The decay of the Ca2+ current (ICa) during a maintained depolarization was studied in intact t... more 1. The decay of the Ca2+ current (ICa) during a maintained depolarization was studied in intact twitch skeletal muscle fibres of Rana pipiens and Rana moctezuma with the three-micro-electrode voltage-clamp technique. 2. ICa was recorded at 23 TC, after blocking K+ currents, in TEA methanesulphonate saline with 10 mM-Ca2+ made hypertonic by adding 350 mM-sucrose. 3. In two-pulse experiments, ICa during the test pulse was reduced to about 80 % (R. pipiens) or 50 % (R. moctezuma) of the control value, without any detectable inward ICa during 7 s conditioning pre-pulses. 4. The experimental points of the steady-state inactivation curve (h.) were fitted to hoo = (1 +exp ((Em-Vh)/kh))-, where Em is the membrane potential and with Vh =-33 + 3 mV and kh = 6 +1 mV for R. pipiens, and Vh =-44 + 3 mV and kh = 9-5 + ±10 mV for R. moctezuma. 5. The rate constant of decay for inactivated currents (range-8 to-47 mA cm3) and for control currents (range-23 to-62 mA cm-3), was independent of Ica amplitude. The average rate constant of decay at 0 mV was 118 + 002 s-1 (66). 6. These results indicate that in intact fibres under hypertonic solution Ica decay can be explained by a voltage-dependent inactivation process and not by depletion of tubular Ca2+. The absence of depletion could be due to a large fractional tubular volume or to the presence of a Ca2+ pump in the tubular system. INTRODUCTION Voltage-clamp experiments in frog skeletal muscle fibres have shown that Ca2+ current (Ica) spontaneously decays during a maintained depolarization (Beaty &
The Journal of Physiology, 1980
1. Current and voltage clamp experiments were carried out on frog skeletal muscle fibres. For vol... more 1. Current and voltage clamp experiments were carried out on frog skeletal muscle fibres. For voltage clamp, the three micro-electrode technique near the fibre end was used. 2. Calcium spikes and currents were recorded in TEA sulphate saline. The addition of 400 mM-glycerol did not appreciably modify them. 3. Muscle fibres were detubulated with the glycerol method. They showed sodium propagating action potentials, with sodium and potassium currents of expected amplitudes. 4. Calcium spikes and currents were reduced or abolished in detubulated muscle fibres. 5. An analysis of fibre capacitance showed a linear correlation between the remaining ICa and the degree of electric discontinuity between the transverse tubular system and the surface membrane. 6. These results indicate that ICa is mainly located in the transverse tubular system. This localization is compatible with some role during mechanical activation.
The Mechanism of Gated Calcium Transport Across Biological Membranes, 1981
Neuropsychobiology, 1996
Electrodermal responses in the facial region of freely moving rats were recorded bilaterally. Aft... more Electrodermal responses in the facial region of freely moving rats were recorded bilaterally. After a nociceptive stimulus (ammonia vapor exposure), the response (a transient negative potential followed by a longer-lasting positive potential) attained a similar amplitude on both sides. Surgical sympathetic denervation of facial skin by ipsilateral superior cervical ganglionectomy (SCGx) significantly decreased the electrodermal response. When an inferior cervical ganglionectomy was performed in addition to SCGx, a further decrease in electrodermal response was observed. Pretreatment of unilaterally SCGx rats with atropine blunted the electrical response in the control side to levels similar to those found in the SCGx side. Treatment with phenoxybenzamine or propranolol was ineffective. Skin potential responses were measured in adult rats administered with clomipramine from the 8th to the 21st day of life and exhibiting a long-lasting syndrome resembling human depression. Clomipramine-injected rats developed larger skin potential responses to sound stimulation than controls while responses to ammonia vapor were similar in both groups, as well as the habituation rate after repetitive exposure to ammonia vapor. The results indicate that some of the altered electrodermal responses found in depressed patients are detectable in the clomipramine animal model of endogenous depression.
Neuropediatrics, 2010
Autosomal recessive hereditary spastic paraplegia with thinning of the anterior corpus callosum (... more Autosomal recessive hereditary spastic paraplegia with thinning of the anterior corpus callosum (ARHSP-TCC) due to mutations in SPG11 on chromosome 15q (MIM610844) is the single most common cause of ARHSP. It is characterized by slowly progressive paraparesis and peripheral neuropathy. Although cognitive impairment, sometimes diagnosed as mental retardation, is an almost invariable feature, the extent and specific neuropsychological features are not fully understood. We report a comprehensive neuropsychological assessment in two ARHSP-TCC patients harbouring mutations in SPG11. A specific impairment in executive functions occurring even before cognitive decline, may be considered the core of the neuropsychological profile of patients harbouring mutations in SPG11.
Muscle & Nerve, 1993
The properties of singles K+ channels in normal and denervated muscles were compared using the "p... more The properties of singles K+ channels in normal and denervated muscles were compared using the "patch-clamp" technique. Single channels were recorded from vesicles obtained by stretching bundles of normal and denervated extensor digitorium longus (EDL) muscles. The most frequently observed channel in normal muscles was a high conductance (266 pS) Ca+ +activated K+ channel. Although channel density, as estimated by patch recording, showed a significant decrease in denervated muscles, no differences were found in conductance and gating properties. Another voltage-dependent K+ channel (81 pS) was only recorded from normal muscles, but never from denervated ones. In addition, a 35 pS conductance was recorded from both normal and denervated fibers. This channel displayed neither voltage dependence nor sensitivity to tetraethylammonium (TEA). In contrast, another TEAinsensitive (16 pS) channel was recorded only from denervated muscles. We conclude that denervation induces significant changes in the distribution and expression of K+ channels in mammalian skeletal muscles.
Journal of Psychosomatic Research, 2004
To determine whether depression is associated with cardiac autonomic alterations in elderly patie... more To determine whether depression is associated with cardiac autonomic alterations in elderly patients with recent acute coronary syndromes (ACSs). Cross-sectional study on the association between a major depressive episode or isolated depressive symptoms (21-item Hamilton depression score) and heart rate variability abnormalities in 56 adults (31 women, 55%) 60 years of age and older with a recent (24-72 h) myocardial infarction (MI) or unstable angina (UA). Spectral and nonspectral parameters of respiratory sinus arrhythmia, indicative of parasympathetic activity on the heart, were decreased in patients with depression (high-frequency heart rate variability [log ms(2)] 2.12+/-0.4 vs. 2.52+/-0.5, P=.024; pNN50 [%] 1+/-2 vs. 9+/-15, P=.006; and rMSNN [ms] 16+/-6 vs. 28+/-22, P=.009). Also, high-frequency heart rate variability decreased with increasing depressive symptom severity. In a sample of older adults suffering from ACSs, depression was associated with impaired parasympathetic control of the heart.
Journal of Neurochemistry, 2008
The diurnal variations and photic regulation of cyclic AMP and melatonin content in golden hamste... more The diurnal variations and photic regulation of cyclic AMP and melatonin content in golden hamster retina were studied. Both parameters showed significant diurnal variations with maximal values at night. Light exposure during the night inhibited retinal cyclic AMP and melatonin levels, whereas exposure to darkness during the day significantly increased cyclic AMP and melatonin content. Incubation with melatonin of retinas excised at different intervals indicated that the methoxyindole inhibited cyclic AMP accumulation in a time-dependent manner. The inhibitory effect of melatonin at 2400 h and at noon showed a threshold concentration of 1 and 10 pM, respectively. At 0400 h melatonin did not affect cyclic AMP accumulation. The results indicate a diurnal variability of retinal cyclic AMP and melatonin content in hamsters, mainly influenced by a photic stimulus. Cyclic AMP could be a putative second messenger for melatonin action in golden hamster retina.
Journal of Cellular Physiology, 1988
Slow Ca-action potentials (CaAP) were studied in normal human skeletal muscle fibers obtained dur... more Slow Ca-action potentials (CaAP) were studied in normal human skeletal muscle fibers obtained during surgery (fibers with both ends cut). Control studies also were carried out with intact as well as cut rat skeletal muscle fibers. Experiments were performed in hypertonic CI-free saline with 10 or 84 m M Ca and K-channel blockers; muscles were preincubated in a saline containing Cs and tetraethylammonium. A current-clamp technique with two intracellular microelectrodes was used. In human muscle, 14.5% of the fibers showed fully developed CaAPs, 21 % displayed nonregenerative Ca responses, and 64.5% showed only passive responses; CaAPs were never observed in 10 m M Ca. In rat muscle, nearly 90% of the fibers showed CaAPs, which were not affected by the cut-end condition. Human and rat muscle fibers had similar membrane potential and conductance in the resting state. In human muscle (22-32" C, 84 m M Ca), the threshold and peak potential during a CaAP were + 26 k 6 mV and + 70 ? 3 mV, respectively, and the duration measured at threshold level was 1.7 2 0.5 sec. In rat muscle, the duration was four times longer. During a CaAP, membrane conductance was assumed to be a leak conductance in parallel with a Ca and a K conductance. In human muscle (22-32" C, 84 m M Ca, 40 p m fiber diameter), values were 0.4 2 0.1 pS, 1.1 f 0.7 p,S, and 0.9 * 0.4 p,S, respectively. Rat muscle (22-24" C, 84 m M Ca) showed leak and K conductances similar to those found in human fibers. Ca-conductance in rat muscle was double the values obtained in human muscle fibers. Ca-dependent action potentials have been observed in mammalian muscle, when C1 was replaced by a
Journal of Cellular Physiology, 1990
slow Ca-dependent action potentials were studied in skeletal muscle fibers from different Neuromu... more slow Ca-dependent action potentials were studied in skeletal muscle fibers from different Neuromuscular Diseases (NMD). Byopsies were obtained from: 3 myopathies [Fascioscapulohumeral Dystrophy (FSH) and Polymyositis (PM)], 6 patients with other diseases (CD) [Amyotrophic Lateral Sclerosis (ALS), Central Core Disease, Mitochondria1 Myopathy, Polyneuritis (PN), von Eulenberg's Paramyotonia], and 8 normal control muscles. Experiments were carried out in muscle fibers under current-clamp conditions. Membrane currents other than Ca ones were abolished or greatly diminished. Muscle fibers produced any of 3 types of responses, when stimulated by depolarizing pulses: fully developed Ca-action potentials (CaAP), abortive non-regenerative Ca responses (NrR), or only capacitive passive responses (WK). The 3 types of responses were not dependent on the basal conditions of the fibers. The frequency of observation of CaAPs was significantly higher in myopathic disease. In rnyopathies, 46% of the muscle fibers had CaAPs, while only 22% of fibers from CD and 15% of the fibers from normal muscles showed CaAPs. N o differences were observed in the resting constants as well as in the CaAPs parameters between normal and diseased muscle fibers.