Effects of carotid sinus nerve stimulation on respiratory sinus arrhythmia and respiratory blood pressure waves of the dog

The effect on the amplitudes of RSA and RBPW of the time of the stimulus in the cardiac cycle, and also of continuous stimulation were studied. When the stimulus train was applied near peak systole the amplitudes of RSA and RBPW decreased. Stimulation in late systole increased both RSA and RBPW. Continuous stimulation did not exert any effects on RSA and RBPW.     

Angiotensin-converting enzyme 2 in acute respiratory distress syndrome

Angiotensin-converting enzyme (ACE) and ACE2 are highly homologous metalloproteases that provide essential catalytic functions in the renin-angiotensin system (RAS). Angiotensin II is one key effector peptide of the RAS, inducing vasoconstriction and exerting multiple biological functions. ACE cleaves angiotensin I to generate angiotensin II, whereas ACE2 reduces angiotensin II levels. Accumulating evidence has demonstrated a physiological and pathological role of ACE2 in the cardiovascular systems. Intriguingly, the SARS coronavirus, the cause of severe acute respiratory syndrome (SARS), utilizes ACE2 as an essential receptor for cell fusion and in vivo infections. Moreover, recent studies have demonstrated that ACE2 protects murine lungs from acute lung injury as well as SARS-Spike protein-mediated lung injury, suggesting a dual role of ACE2 in SARS infections and protection from ARDS. Received 18 May 2006; received after revision 12 March 2007; accepted 24 April 2007     

Facilitation of avoidance conditioning by reticular stimulation in the cat]

Learning is facilitated in Cats by posttrial reticular stimulation. It has been pointed out that this stimulation has no immediate anterograde effect and does not evoke any change in the cortical, motor or autonomic functions during its delivery. Moreover this stimulation has no effect on the time course of cortical and autonomic responses to the conditioned stimulus. Therefore, these results suggest that reticular stimulation has a specific action on memory consolidation or information processing.     

Über einen Bahnung seffekt bei sukzessiver Einwirkung von vestibulären und optokinetischen Reizen

Summary In the rabbit rotatory vestibular stimulation followed by optokinetic stimulation has a persisting facilitatory effect on the latter. The facilitation is independent of the direction of the second stimulus relative to the first one. It can therefore not be explained on the basis of the well-known addition effect in simultaneous stimulation. The neurophysiological and biological aspects of the phenomenon are discussed.     

Birefringence signals and tension development in single frog muscle fibres at short stimulus intervals

Summary The early large birefringence signal and mechanical activity were studied together in isolated single fibres of frog skeletal muscle with double stimulation at short stimulus intervals (2–60 msec) at room temperature and at 4–6°C. In all fibres tested, extra tension and additional birefringence signal in response to the second stimulus appeared simultaneously and suddenly upon increasing the stimulus interval. The shape of the stimulus-interval versus tension-development curve makes it highly improbable that subthreshold calcium release occurs at shorter stimulus intervals; therefore, tension development reliably reflects Ca-release in these experiments. In contrast to the report by Suarez-Kurtz and Parker, birefringence signal and calcium release are shown not to be dissociated by double stimulation. This result supports the hypothesis that the early large birefringence signal is an intrinsic indicator of calcium release from the sr during EC-coupling in skeletal muscle.     

Birefringence signals and tension development in single frog muscle fibres at short stimulus intervals.

The early large birefringence signal and mechanical activity were studied together in isolated single fibres of frog skeletal muscle with double stimulation at short stimulus intervals (2-60 msec) at room temperature and at 4--6 degrees C. In all fibres tested, extra tension and additional birefringence signal in response to the second stimulus appeared simultaneously and suddenly upon increasing the stimulus interval. The shape of the stimulus-interval versus tension-development curve makes it highly improbable that subthreshold calcium release occurs at shorter stimulus intervals; therefore, tension development reliably reflects Ca-release in these experiments. In contrast to the report by Suarez-Kurtz and Partker, birefringence signal and calcium release are shown not to be dissociated by double stimulation. This result supports the hypothesis that the early large birefringence signal is an intrinsic indicator of calcium release from the sr during EC-coupling in skeletal muscle.     

Periodic variations in motor endplate potentials]

The amplitudes of motor end-plate potentials in the Frog have been measured during repetitive stimulations of the motor nerve at frequencies between 0,5 and 30 Hz. A serial analysis showed that cyclic variations of these amplitudes were superimposed on the random fluctuation of epp due to the quantal nature of transmitter release. The period of these cyclic variations varied between 3 and 10 stimulations. This period was not significantly related to the frequency of the stimulation. The frequency spectrum analysis of the epp amplitudes showed similar values for the period of the cyclic variation of epp. The same kind of analysis applied to a binomial series of random numbers did not significantly present periodic fluctuations. The same analysis was applied to mean amplitudes of groups of 5 to 120 successive epps at the same end-plate. Periodic fluctuations were identified with periods of about 10 to 180 sec. It is suggested that periodic failures of nerve spike propagation in nerve terminals at sites of low safety factor, as at branchings, are responsible for the observed cyclic variation of epp.     

Interaction between visual activation and proprioceptive activation in neurons of the superior colliculus]

Units located in the superficial and intermediate layers of the superior colliculus are activated by proprioceptive stimulation of the extraocular muscle nerves as well as by specific visual stimuli. Units of the deep layer of the colliculus, not sensitive to visual activation, are inhibited by proprioceptive stimulation. A few of the units showed interaction between the two types of stimulation, the proprioceptive response appearing only when spontaneous activity was decreased by a visual stimulus.     

Influence of cervical sympathetic nerve stimulation on carotid sinus baroreceptor afferents

Summary In rabbits and dogs, the response of low-threshold carotid sinus baroreceptor afferent fibres to cervical sympathetic nerve stimulation at various non-pulsatile steady pressures was examined. Fibres which possessed a rhythmic bursting discharge at low pressures increased this activity during sympathetic stimulation; all other low-threshold afferents were unaffected.This work was supported by the Medical Research Council of Canada and the British Columbia Heart Foundation.     

Variations au cours de la journée de l'incorporation in vivo de la leucine tritiée dans les protéines du cervelet et du cerveau du jeune rat normal et hypothyro?dien. Daily variations of the in vivo [3H] leucine incorporation into the cerebellar and cerebral proteins of the normal and hypothyroid young rat [(author's transl)

In the normal and hypothyroid 6-day-old rat, the specific radioactivity (RSA) and the relative RSA (ratio of the RSA to the [3H] lecine concentration of the acido soluble phase) of the cerebral and cerebellar proteins, changes during the day synchronally. They show a maximum at 15.00 h and a minimum at 0.300 h. At all stages studied, these values are significantly lower in the hyothyroid animals than in normal ones.     

Bilaterale Projektion der Netzhaut auf die Sehrinde des Kaninchens

Summary The bilateral representation of the retina on the visual cortex was investigated by analysing the amplitude, latency and topic distribution of the potentials evoked in the visual cortex by monocular photic stimulation of the retina in the conscious rabbit. The amplitudes of the potentials evoked on both ipsi- and contralateral hemispheres, show a relation 1:4. A small field for bilateral retinal projection of the retina was mapped in the anterolateral part of the visual cortex. These differences in amplitude, latency and topic distribution may be significant for stereoscopic vision.     

Nouveau principe de stimulation électrique: L'excitation ambipolaire par courant alternatif,sinusoïdal pur,de fréquence moyenne

Summary Impulses of amplitude-modulated middle-frequency current (20 000 c.p.s.) stimulate nerve simultaneously at both poles. No polarity effect is observed, because no rectification occurs in the stimulation circuit if pure sine-wave middle-frequency current is employed. This principle is demonstrated by using bipolar longitudinal stimulation that, above threshold, elicits action currents, with latency difference corresponding to the distance between the stimulating electrodes. With supramaximum strength, maximum action currents are obtained at either pole, as is the case with ordinary cathodal stimuli of supramaximum strength applied to one pole or the other. Middle-frequency stimulation, therefore, has to be regarded asambipolar, i.e. does not depend on polarity. With second harmonic distortion, however, rectification occurs in the stimulation circuit and contamination by direct-current component ensues. Middle-frequency stimulation can be applied across nerve, since the excitatory effect does not apparently depend on longitudinal current flow. This method allows the action current to be recorded at the site of stimulation with minimum stimulus artefact.     

Variations au cours de la journée de l'incorporation in vivo de la leucine tritiée dans les protéines du cervelet et du cerveau du jeune rat normal et hypothyroïdien

Summary In the normal and hypothyroid 6-day-old rat, the specific radioactivity (RSA) and the relative RSA (ratio of the RSA to the [³H] leucine concentration of the acido soluble phase) of the cerebral and cerebellar proteins, change during the day synchronally. They show a maximum at 15.00 h and a minimum at 03.00 h. At all stages studied, these values are significantly lower in the hypothyroid animals than in normal ones.     

Bestimmung der optimalen Reizparameter bei Reizung des aszendierenden retikulären Systems

Summary For the initiation of an arousal reaction, the stimulation of the reticular activating system by square waves of frequencies varying from 50 to 400 c/s was studied. To evaluate the stimulation efficiency, the initial frequency of the rhinencephalic arousal reaction was used. The optimal stimulus frequency depends on the duration of the pulses. The optimal frequency was found to be 200 c/s at a pulse duration of 0.5 ms and 100 c/s at a pulse duration of 1.5 ms.     

Priming effect of vasoactive intestinal peptide on the respiratory burst of neutrophils non-mediated by plasma membrane receptors

Vasoactive intestinal peptide (VIP) primed the respiratory burst of human neutrophils in response to phorbol myristate acetate. Maximal and half-maximal effects were achieved at 10 and 0.5 nM VIP respectively. The absence of plasma membrane receptors to VIP in neutrophils suggests that priming of the respiratory burst should be considered as a side effect of VIP. However, from the above indicated concentration range, the priming of the neutrophil by VIP cannot be considered as a pharmacological effect. The enhancement of the formation of reactive oxygen metabolites by VIP may be important in the pathology of VIP-producing tissues.     

Comparison of the time courses of luteinizing hormone (LH) secretion rates during continuous stimulation by LH-releasing hormone (LH-RH) in vivo and in vitro

Summary The patterns of LH secretion during constant stimulation of the pituitary glands of estradiol-treated ovariectomized rats with a maximally stimulating amount of LH-RH in vivo and in vitro correspond with each other qualitatively and quantitatively. In vitro the changes with time of the LH secretion rate are somewhat retarded, especially the occurrence of desensitization.     

Circulatory and respiratory consequences of massive hemorrhage are reversed by protoveratrines

Summary In a rat model of severe hypotension and respiratory depression induced by step-wise bleeding, protoveratrines cause a prompt and sustained improvement of cardiovascular and respiratory functions, both in anesthetized and in conscious animals, seemingly through a magnification of the reflex response originated by the chemoreceptors of aortic and carotid bodies. The restoration of cardiovascular function is attributable to an increase both in total peripheral resistance and cardiac output. The finding could provide the basis for a new approach to the first-aid management of massive blood losses.     

Modulator role of prostaglandins (Pg) in adrenergic neurotransmission in carotid sinus]

In Rabbit carotid sinus, the presence of sympathetic nerve endings capable of releasing noradrenaline has been demonstrated. The release of NA in response to sympathetic nerve stimulation was decreased by PgE2 and a precursor of Pg (arachidonic acid) but was strongly increased by an inhibitor of Pg biosynthesis (indomethacin). The experiments carried out demonstrated that freshly synthesized Pg acts in the same way as exogenous Pg and suggested that Pg could have a regulating effect on adrenergic neurotransmission in carotid sinus. The role of this regulating mechanism in the physiology of carotid sinus has been discussed.     

Protein kinase C-dependent NF-κB activation is altered in T cells by chronic stress

Chronic stress has been associated with impaired immune function. In this work we studied the effect of chronic mild stress (CMS) exposure on the early intracellular pathways involved in T cells after stimulation with mitogen. We found that mitogen stimulation of T lymphocytes from CMS-exposed mice resulted in a reduction of the intracellular [Ca²⁺] rise, an impairment of growth-promoting protein kinase C (PKC) activation, a lower NF-κB activation and an increase in the inhibitory cAMP-protein kinase A (PKA) pathway activity with respect to those found in control lymphocytes. However, T cell activation with the direct PKC activator phorbol 12-myristate 13-acetate plus calcium ionophore led to a similar proliferative response in both CMS and control lymphocytes, indicating that signals downstream of PKC would not be affected by stress. In summary, our results show that chronic stress induced an alteration in T cell early transduction signals that result in an impairment of the proliferative response.Received 11 February 2005; received after revision 20 May 2005; accepted 6 June 2005     

Correlation between inhibition of stimulatory membrane repolarization and positive inotropic response caused by ouabain in rat heart]

During a stimulus train, the diastolic membrane potential of rat atria exhibits a depolarization phase followed by a slower repolarization phase which has been attributed to the activation of an electrogenic sodium pump (ATPase Na+, K+). This pump seems to be all the more active as stimulation frequency is higher. The parallel evolution of the sodium pump inhibition and a positive inotropic effect in response to ouabain perfusion, suggests that the enzymatic inhibition is directly involved in the development of the cardiotonic effect of digitalis.