Marcello Alessandro Caria

Neurogenic myocardial arrhythmias in experimental focal epilepsy

Summary: The potential for cardiac arrhythmia was studied in an experimental focal epilepsy induced in hemispherectomized rats by topical application of buffered penicillin G onto the thalamus. The epileptic burst triggered cardiac and hemodynamic responses, as simultaneously monitored by arterial pressure, and hypothalamic and heart activity. During interictal epileptic activity, the single burst triggered a short‐latency cardiac arrhythmia, characterized by sinus bradyarrhythmia and junctional rhythm, and lengthening of intervals between sphygmic waves with significant reduction of diastolic pressure. When the epileptic burst stopped, the cardiac activity resumed normal rhythm, and diastolic pressure returned to basal value. During ictal epileptic activity, the sinus and junctional bradyarrhythmic episodes lasted longer, and supraventricular extrasystoles, sinus arrest, and bigeminal ventricular extrasystoles were observed. Both systolic and diastolic pressures decreased from 120/85 to 100/65 mm Hg. The end of the ictal episode always marked resumption of normal cardiac rhythm and systemic pressure. Considering the absence of metabolic complications (blood‐gas analytic parameters and acid‐base balance being controlled) and the short latency of the cardiac and hemodynamic responses, it is suggested that during paroxysmal hypothalamic activity the observed cardiac arrhythmias and the hemodynamic modifications were neurogenic in origin. A role for cardiovascular alterations in sudden unexplained epileptic death is postulated.

Estimating stroke volume from oxygen pulse during exercise.

This investigation aimed at verifying whether it was possible to reliably assess stroke volume (SV) during exercise from oxygen pulse (OP) and from a model of arterio-venous oxygen difference (a-vO(2)D) estimation. The model was tested in 15 amateur male cyclists performing an exercise test on a cycle-ergometer consisting of a linear increase of workload up to exhaustion. Starting from the analysis of previous published data, we constructed a model of a-vO(2)D estimation (a-vO(2)D(est)) which predicted that the a-vO(2)D at rest was 30% of the total arterial O(2) content (CaO(2)) and that it increased linearly during exercise reaching a value of 80% of CaO(2) at the peak workload (W(max)) of cycle exercise. Then, the SV was calculated by applying the following equation, SV = OP/a-vO(2)D(est), where the OP was assessed as the oxygen uptake/heart rate. Data calculated by our model were compared with those obtained by impedance cardiography. The main result was that the limits of agreement between the SV assessed by impedance cardiography and the SV estimated were between 22.4 and -27.9 ml (+18.8 and -24% in terms of per cent difference between the two SV measures). It was concluded that our model for estimating SV during effort may be reasonably applicable, at least in a healthy population.

Quantification of spinning® bike performance during a standard 50-minute class

Abstract Spinning is a type of indoor fitness activity performed on stationary bikes by participants who pedal together to the rhythm of music and the motivating words of an instructor. Despite worldwide popularity of this type of recreational activity, to date there have been few, mainly non-scientific, studies of the impact of spinning on metabolic, respiratory, and cardiovascular functions. The main aim of this study was to evaluate a number of metabolic and cardiovascular variables during a standard 50-min class performed by Spinning® instructors of both sexes: six males (age 30 ± 4.8 years, body mass index 24 ± 2.5 kg · m−2; mean ± s) and six females (age 34 ± 6.3 years, body mass index 21 ± 1.9 kg · m−2). The mean power output, heart rate, and oxygen uptake during the performance were 120 ± 4 W, 136 ± 13 beats · min−1, and 32.8 ± 5.4 ml · kg−1 · min−1 respectively for males, and 73 ± 43 W, 143 ± 25 beats · min−1, and 30 ± 9.9 ml · kg−1 · min−1 respectively for females. Analysis of individual performances showed that they were compatible with physical exercise that ranged from moderate-to-heavy to very heavy, the latter conditions prevailing. The results show that this type of fitness activity has a high impact on cardiovascular function and suggest that it is not suitable for unfit or sedentary individuals, especially the middle aged or elderly, who are willing to begin a recreational physical activity programme.

Spatial‐time variability and conservation relevance of plant communities in Mediterranean temporary wet habitats: A case study in Sardinia (Italy)

This research was undertaken with the aim of improving our knowledge of the floristic composition and spatial‐temporal dynamics of plant communities in Mediterranean temporary wet habitats, and to evaluate the diversity and conservation relevance of their plant assemblages. Three different types of temporary wet habitats were monitored throughout the growing season: large temporary ponds (lTPs), small temporary ponds (sTPs), and rock pools (RPs). lTPs presented a small‐scale zonation arranged in an inner, an intermediate, and a peripheral belt. A total of 98 species were recorded, of which 40 were classified as temporary wet habitat (TWH) specialists and 24 as rare. Eight different groups of plant assemblages were identified presenting space–time dynamics related to water‐depth variations and flooding period. In terms of diversity, the most relevant assemblages were located in the outer belt of the lTPs and in the sTPs. The mosaic of different assemblages and their time‐variability determined the presence of several types of habitats of community interest according to the Habitat Directive. This wide heterogeneity should be taken into account to ensure that all types of TWHs are considered in conservation programmes.

Labyrinthine projection to the hypoglossal nucleus

Evoked potentials and responses of single hypoglossal neurons were recorded in response to electrical stimulation of the labyrinth. In addition, the spontaneous electrical activity of hypoglossal neurons was significantly modified in response to ipsi- and contralateral static tilt of the whole animal and thermic stimulation of the labyrinth. The experiment showed that the labyrinth modulates the electrical activity of hypoglossal neurons with phasic inputs in response to ampullar stimulation and with tonic inputs in response to macular stimulation. The vestibular phasic influence of hypoglossal neurons represents the most adequate functional pattern to obtain a quick, short lasting response of the tongue muscles instantly modifiable with every abrupt head displacement. On the contrary, the vestibular tonic influence of hypoglossal neurons represents the most adequate functional pattern to obtain not only adjustment but also maintenance of the muscular lingual response to static displacement of the head.

Improvement of Vestibular Plasticity in the Guinea Pig with a Calcium Entry Blocker

The influence of flunarizine on vestibular compensation was investigated in hemilabyrinthectomized guinea pigs. The results showed that the vestibular deficits from hemilabyrinthectomy disappeared more rapidly in the treated animals than in the controls. To elucidate the mechanism by which the drug could affect the compensatory process, further studies on the spontaneous and evoked activity of vestibular nuclei were performed in normal, labyrinthectomized and labyrinthectomized-cerebellectomized animals. These electrophysiological data implied that flunarizine improved the vestibular compensation by inhibiting the receptor and nuclear activities of the intact labyrinth. The drug excited the cerebellar cortex, which modulated the activity of the vestibular nuclei of both sides, restoring the balance disrupted by hemilabyrinthectomy.

Gap analysis revealed a low efficiency of Natura 2000 network for the conservation of endemic species in Mediterranean temporary freshwater habitats

Listed and rare species are abundant in temporary freshwater habitats. Among them, the endemic contingent represents a crucial conservation target particularly in the areas characterized by abundant endemic flora for which the local administrations have a high level of responsibility. The aim of this research was to test how the endemic plants found in Mediterranean temporary ponds were represented in Natura 2000 network in a biodiversity hotspot of the Mediterranean region. The results of our research at regional scale pointed out that the existing Nature 2000 sites provide a limited degree of protection and that the gap analysis should be taken into account when conservation priorities are set.

Effect of acute exercise on low molecular weight thiols in plasma.

An important defence against free radicals is represented by plasma low molecular weight (LMW) thiols that compose a dynamic system of reduced and oxidized forms able to act as a buffer redox system. This study examined the effect of an acute graded exercise bout on LMW thiols in 16 young subjects (six sedentaries and 10 athletes). Blood analysis was performed before and immediately after the exercise and total and reduced thiols were measured in order to evaluate the thiol redox status. Findings suggested that the exercise test proposed was not enough to imbalance the redox status of all LMW thiols. However, when the redox status was evaluated for each thiol, it was evident that homocysteine (Hcy) redox status was significantly different after physical activity. In particular, we found a lower level of reduced Hcy after the exercise test both in sedentaries and in athletes. We concluded that duration and intensity of the proposed exercise were not enough to promote a reactive oxygen species production able to imbalance the redox thiols status and that the lowering of the reduced Hcy form may be due to the effect produced during the effort on the synthesis and/or removal processes of Hcy.

Role of the trigeminal mesencephalic nucleus in rat whisker pad proprioception

BackgroundTrigeminal proprioception related to rodent macrovibrissae movements is believed to involve skin receptors on the whisker pad because pad muscles operate without muscle spindles. This study was aimed to investigate in rats whether the trigeminal mesencephalic nucleus (TMnu), which provides proprioceptive feedback for chewing muscles, may be also involved in whisker pad proprioception.MethodsTwo retrograde tracers, Dil and True Blue Chloride, were injected into the mystacial pad and the masseter muscle on the same side of deeply anesthetized rats to label the respective projecting sensory neurons. This double-labeling technique was used to assess the co-innervation of both structures by the trigeminal mesencephalic nucleus (TMnu).In a separate group of anesthetized animals, the spontaneous electrical activities of TMnu neurons were analyzed by extracellular recordings during spontaneous movements of the macrovibrissae. Mesencephalic neurons (TMne) were previously identified by their responses to masseter muscle stretching. Changes in TMne spontaneous electrical activities, analyzed under baseline conditions and during whisking movements, were statistically evaluated using Students t-test for paired observations.ResultsNeuroanatomical experiments revealed different subpopulations of trigeminal mesencephalic neurons: i) those innervating the neuromuscular spindles of the masseter muscle, ii) those innervating the mystacial pad, and iii) those innervating both structures. Extracellular recordings made during spontaneous movements of the macrovibrisae showed that whisking neurons similar to those observed in the trigeminal ganglion were located in the TMnu. These neurons had different patterns of activation, which were dependent on the type of spontaneous macrovibrissae movement. In particular, their spiking activity tonically increased during fan-like movements of the vibrissae and showed phasic bursting during rhythmic whisking. Furthermore, the same neurons may also respond to masseter muscle stretch.Conclusionsresults strongly support the hypothesis that the TMnu also contains first-order neurons specialized for relaying spatial information related to whisker movement and location to trigeminal-cortical pathways. In fact, the TMnu projects to second-order trigeminal neurons, thus allowing the rat brain to deduce higher-order information regarding executed movements of the vibrissae by combining touch information carried by trigeminal ganglion neurons with proprioceptive information carried by mesencephalic neurons.

Analysis of central cardioarrhythmogenic triggers in experimental epilepsy

The cardioarrhythmogenic potential of epileptic foci induced at mesencephalic and rhombencephalic levels was analyzed in hemispherectomized rats. Topical application of penicillin-G onto the mesencephalic quadrigeminal lamina or onto the fourth ventricle induced paroxysmal activity at the mesencephalic or bulbar neurone level. At the mesencephalic levels, the paroxysmal activity was characterized by a significant increase in the spontaneous frequency of the neurones, with the appearance of multiunit activity and rhythmical outbursts. The simultaneous recording of myocardial electrical activity and blood pressure showed that the paroxysmal activity triggered short-latency sinus bradyarrhythmias with wandering of the sinus pacemaker, the appearance of biphasic or negative P waves, some premature ventricular contractions and non-significant reduction of systolic and diastolic pressures. When the paroxysmal activity stopped, the cardiac rhythm and blood pressure returned to basal values. At the bulbar level, the paroxysmal activity appeared with longer latency and usually the rhythmical outbursts were not observed. Following bulbar paroxysmal activity only short-lasting episodes of sinus bradyarrhythmias appeared. Midcollicular transection eliminated paroxysmal activity at the bulbar level, and blood pressure and cardiac rhythm resumed basal values. After transection, an additional application of convulsant drug (penicillin-G or pentylenetetrazole) onto the fourth ventricle did not induce the reappearance of paroxysmal activity and the consequent cardiovascular alterations. The results showed the existence of a cardioarrhythmogenic trigger localized at the mesencephalic level which spreads paroxysmal activity upwards. A hypothesis to explain the appearance of fetal haemodynamic modifications and life-threatening arrhythmias has been proposed.