High-Throughput Phenotyping in Plant Stress Response: Methods and Potential Applications to Polyamine Field.

High-throughput phenotyping has opened whole new perspectives for crop improvement and better understanding of quantitative traits in plants. Generation of loss-of-function and gain-of-function plant mutants requires processing and imaging a large number of plants in order to determine unknown gene functions and phenotypic changes generated by genetic modifications or selection of new traits. The use of phenomics for the evaluation of transgenic lines contributed significantly to the identification of plants more tolerant to biotic/abiotic stresses and furthermore, helped in the identification of unknown gene functions. In this chapter we describe the High-throughput phenotyping (HTP) platform working in our facility, drawing the general protocol and showing some examples of data obtainable from the platform. Tomato transgenic plants over-expressing the arginine decarboxylase 2 gene, which is involved in the polyamine biosynthetic pathway, were analyzed through our HTP facility for their tolerance to abiotic stress and significant differences in water content and ability to recover after drought stress where highlighted. This demonstrates the applicability of this methodology to the plant polyamine field.

Compared effects of sotalol, flecainide and propafenone on ventricular repolarization in patients free of underlying structural heart disease.

Antiarrhythmic drugs are known to affect the depolarization and repolarization time in a different fashion. The aim of the present study was to compare the effects of Sotalol, Flecainide and Propafenone on some common (QT, QTc, JT, JTc) or uncommon (QTc dispersion, T-peak to T-end interval) electrocardiographic parameters in order to evaluate the effects of these antiarrhythmic drugs on ventricular repolarization time both in terms of absolute values and of dispersion across the myocardium. The analysis of these antiarrhythmic drug effects was performed on the standard 12-lead electrocardiograms of 31 patients (17F and 14M, age 38.1+/-17 years, range 11-67 years) in the free-drug state and at the steady state after oral treatment with Sotalol (160 mg daily), Flecainide (200 mg daily) and Propafenone (450 mg daily). These drugs were prescribed, separately, to all the 31 patients, free of underlying structural heart disease, for the treatment of their atrio-ventricular nodal re-entry tachycardia. Data of the present study show that Sotalol, over the range prescribed, significantly prolongs ventricular repolarization index QT (P=0.001), JT (P=0.0001) and JTc (P=0.0001) values in an homogeneous fashion, as shown by the significant decrease in QTcD (P=0.019) and Tp-Te (P=0.01). On the contrary, Flecainide treatment was associated with an increase in QTcD (P=0.029), Tp-Te (0.0001), QT (P=0.001), QTc (P=0.0001) and QRS (P=0.0001), with no significant changes in JT and JTc. Propafenone, over the range prescribed, did not affect repolarization time, resulting only in a prolongation of depolarization time as expressed by the increase of QRS (P=0.0001).

Increased QT dispersion and other repolarization abnormalities as a possible cause of electrical instability in isolated aortic stenosis.

The aim of our study was to analyze the ventricular repolarization phase in patients with isolated aortic stenosis (AS) in order to search for possible abnormalities that might contribute to an explanation of the electrical instability peculiar to this valve disease. We selected a population of 39 patients with isolated AS (25 M and 14 F, mean age 60+/-16 yrs). As controls we considered a group of 31 age-matched healthy subjects 20 M and 11 F, mean age 55+/-14 yrs, P=NS. Disease severity was assessed by echocardiography, calculating the maximum and mean pressure gradients max and mean PG) and the functional valve orifice area. Various electrocardiographic intervals (QT, QT'c, JT, JTc) and indices (QT and QTc dispersion were adopted for a detailed non-invasive evaluation of the ventricular repolarization. In patients with AS, M-QT (391+/-45 ms vs 362+/-25 ms, P=0.002), M=QTc (431+/-29 ms vs 412+/-19 ms, P=0.003), M-JT (290+/-41 ms vs 265+/-26 ms, P=0.003, M-JTc 331+/-29 ms vs 302+/-19 ms, P<0.001, QTD (67+/-34 ms vs 40+/-15 ms, P<0.001), QTcD (77+/-36 ms vs 52+/-23 ms, P<0.001) all resulted significantly greater than in controls. QTD and QTcD both resulted linearly related either to max PCi (r=0.388, P=0.018 and r=0.357, P=0.03) or to mean PG (r=0.513, P=0.004 and r=0.438, P=0.015), while M-JT and M-JTc turned out to be directly related only to mean PG (r=0.436, P=0.016 and r=0.483, P=0.007). Our findings suggest a prolonged duration of ventricular recovery and a greater dispersion of ventricular repolarization in patients with AS and might account for the electrical instability proper to this valve dysfunction. Besides, the existence of a linear direct relation between the severity of AS and the degree of inhomogeneity of left ventricular recovery, together with the correlation found among mean PCr and the total duration of the repolarization phase, expressed by the intervals JT and JTc, strongly suggest the hypothesis that in AS arrhythmogenic substrates development parallels the worsening of the valve defect.

Autonomic nervous system imbalance and left ventricular systolic dysfunction as potential candidates for arrhythmogenesis in Becker muscular dystrophy.

We evaluated the arrhythmic profile in a population of 20 Becker muscular dystrophy (BMD) patients searching for possible correlations between the severity of the arrhythmic events, the cardiac autonomic balance (assessed by heart rate variability analysis in the time domain) and the degree of left ventricular systolic impairment. A population of 14 male healthy individuals served as the control group. BMD subjects exhibited lower values of SDNN (P=0.013), SDANN index (P=0.008) and 24-h mean heart rate (P=0.002). The total number of premature ventricular beats (totPVB) and the number of PVB out of 1000 heartbeats (PVB/1000) appeared also higher in BMD subjects (P=0.05 and P=0.046, respectively). No difference was found in terms of 24-h mean QTc and 24-h longest QT among the two groups. TotPVB and PVB/1000 were inversely related to both the ejection fraction (r= -0.620, P=0.004 and r= -0.517, P=0.019) and to the shortening fraction (r= -0.568, P=0.009 and r= -0.469, P=0.037). Twenty-four-h mean QTc was also inversely related to both the ejection fraction (r= -0.520, P=0.019) and the fractional shortening (r= -0.491, P=0.028). These data suggest that in BMD there is cardiac autonomic imbalance characterized by sympathetic predominance and an increased susceptibility to ventricular arrhythmias, even in the absence of overt cardiomyopathy. Furthermore, the severity of the arrhythmic profile in BMD appears closely related to the degree of left ventricular systolic dysfunction.

[Electrophysiological analysis of atrioventricular and intraventricular conduction in bi- and tri-fascicular blocks]. / Analisi elettrofisiologica della conduzione atrioventricolare ed intraventricolare nei blocchi bi- e tri fascicolari.

We have evaluated, at baseline and during incremental atrial pacing (AP), intracardiac conduction features of 53 patients with electrocardiographic diagnosis of bifascicular or trifascicular block, free from any pharmacological treatment potentially able to affect atrioventricular (AV) conduction system properties. The patients have been subdivided in the following groups: group A (13 patients), with LBBB and a PQ interval > or = 200 msec; group B (14 patients), with RBBB, LAH with a PQ interval > or = 200 msec; group C (8 patients), with LBBB and a PQ < 200 msec; group D (15 patients), with RBBB, LAH and a PQ < 200 msec; group E (3 patients), with RBBB, LPH and a PQ < 200 msec. In group A, 31% presented a long AH interval (> 140 msec), while 85% showed an increased infra-his conduction time (HV > 55 msec). During AP, only 38.5% maintained a 1:1 AV conduction ratio up to 140 bpm, while 30.8% developed an infra-his Mobitz 2 2nd degree AV block. 15.4% an infrahis 2:1 2nd degree AV block, 15.4% an AV nodal Mobitz 2 2nd degree AV block. In group B, 64% and 29% exhibited respectively an AV nodal and an infrahis conduction delay. During AP, 57.1% maintained a 1:1 AV conduction ratio up to 140 bpm, 14.3% developed an AV nodal Mobitz 1 2nd degree AV block, 14.3% an infrahis Mobitz 1 2nd degree AV block, 7.1% an AV nodal 2:1 2nd degree AV block, 7.1% an infrahis Mobitz 2 2nd degree AV block. In group C, no patient manifested a prolonged AH interval, while 50% exhibited a HV > 55 msec. 62.5% maintained a 1:1 AV conduction ratio up to 140 bpm, 25% developed an AV nodal Mobitz 1 2nd degree AV block and 12.5% an infrahis 2:1 2nd degree AV block. In group D, no patient showed an increased AH interval and only 13% presented a HV interval exceeding 55 msec. During AP, 86.7% maintained a 1:1 AV conduction ratio up to 140 bpm, 6.6% developed an AV nodal Mobitz 1 2nd degree AV block, 6.6% an infrahis 2:1 2nd degree AV block. In group E, no patient showed a prolonged AH interval, while 2/3 (66.6%) exhibited an infrahis conduction delay. During AP, 100% developed an infrahis 2:1 2nd degree AV block. Considering all patients with LBBB (groups A+C) and with RBBB+LAH (groups B+D), no differences were found in terms of PQ, PA and AH intervals, even though, concerning patients with a long PQ (group A vs group B), AH interval resulted significantly longer in patients with RBBB+LAH (121.85 +/- 36.4 msec vs 163.29 +/- 55.96 msec, p = 0.031). Infrahis conduction, independently from the measurement adopted (HVI interval: from the beginning of the His to the onset of the ventricular electrogram recorded at the His region; HV2 interval: from the beginning of the His to the onset of the surface QRS), resulted more compromised in patients with LBBB than in patients with RBBB+LAH (HVI: 75.24 +/- 40.23 msec vs 50.79 +/- 25.16 msec, p = 0.011; HV2: 77.24 +/- 38.12 msec vs 53.92 +/- 29.3 msec, p = 0.015). Such a difference became even more significant when comparing the percentage of patients with a prolonged HV interval (average value > 55 msec) in the above mentioned groups: 71.4% in case of LBBB, 20.7% in case of RBBB+LAH (p < 0.001). Regarding intraventricular conduction (IV), no statistically significant differences were found. In patients with RBBB+LAH, IV was not related to infrahis conduction time and PQ interval appeared more related to AH (r = 0.838, p < 0.001) than to HV (PQ-HV1: r = 0.381, p = 0.041, PQ-HV2: r = 0.474, p = 0.009). Conversely, in patients with LBBB infrahis and IV conduction appeared linearly related (HVI-V: r = 0.416, p = 0.06; HV2-V: r = 0.445, p = 0.043). As for PQ interval, it resulted more closely related to infrahis conduction (PQ-HVI: r = 0.626, p = 0.002; PQ-HV2: r = 0.674, p < 0.001), than to AH (r = 0.533, p = 0.013). In conclusion, infrahis conduction resulted more impaired in patients with LBBB. In this group, differently from patients with RBBB+LAH, infrahis conduction seems to affect the degree of IV conduction delay. (ABST

QTc and not QTc dispersion behavior affects the occurrence of ventricular extrasystole during exercise in infarcted patients.

Both a long QTc and a large QTc dispersion (QTcd) can predispose infarcted patients to ventricular arrhythmias. The former simply reflects a general prolongation of ventricular recovery time, whereas QTcd is useful for revealing regional inhomogeneities of ventricular repolarization. The aim of our study was to evaluate QTc and QTcd behavior during exercise in 50 patients (all men) with previous myocardial infarction, and its possible correlation with the occurrence of exercise-induced premature ventricular complexes (EIPVC). Our patients underwent ergometric stress test with a load increase of 25 W, every 2 min, until the maximal age-related heart rate or symptoms were obtained, followed by a 10-min recovery phase. QTc and QTcd measurement was performed at rest (BS) and during exercise at two progressively increasing heart rate steps: 100-115 beats/min (T1) and 116-130 beats/ min (T2). The patients were divided into two groups according to the absence (group A; n = 22) or presence (group B; n = 28) of EIPVC. In terms of QTcd, no significant difference was found between the two groups at BS, T1, and T2. As for the mean QTc (QTcm), it was significantly longer in group B at BS (416 +/- 22 ms versus 395 +/- 19 ms; P = 0.001) and at T1 (431 +/- 24 ms versus 410 +/- 8 ms; P = 0.0001). When group B was further differentiated into two subgroups-Bx and Bz-according to the severity of EIPVC, we noted that patients with the most severe arrhythmic response (group Bz; n = 12) showed a persisting, significantly longer QTcm than group A (BS, 426 +/- 28 ms versus 395 +/- 19 ms; P < 0.05; T1, 445 +/- 24 ms versus 410 +/- 8 ms; P < 0.05; T2, 427 +/- 17 ms versus 412 +/- 14 ms; P < 0.05), and group Bx (n = 16) (BS, 426 +/- 28 ms versus 409 +/- 15 ms; P < 0.05; T1, 445 +/- 24 ms versus 420 +/- 19 ms; P < 0.05; T2, 427 +/- 17 ms versus 410 +/- 17 ms; P < 0.05). Group Bx showed a significantly longer QTcm than group A only at BS (409 +/- 15 ms versus 395 +/- 19 ms; P < 0.05). No significant difference in QTcd was found between the three groups at BS, T1, and T2. We also noted that the relationship between QTcm and QTcd was modified by the exercise, changing from a trend of direct relation at BS, towards an inverse one during effort, which reached significance at T2 (r = -0.319; P = 0.037). Based on our data, EIPVC occurrence seems to be more affected by the total duration rather than by regional inhomogeneities of the ventricular recovery time. In those patients with the most severe arrhythmic response, the autonomic modifications generated by the exercise succeed in attenuating only the regional inhomogeneities, but do not eliminate the differences in total duration of the repolarization period.

Increased dispersion of ventricular recovery time as a new repolarization abnormality in the Wolff-Parkinson-White syndrome.

The aim of our study was to assess whether the presence of ventricular preexcitation affects the spatial distribution of ventricular recovery time. Recent reports support the hypothesis that QT and QTc dispersions (QTd and QTcd) can be reliably adopted as a non-invasive parameter to estimate regional discrepancies of ventricular repolarization. The ECGs of 32 healthy subjects with Wolff-Parkinson-White syndrome and of 29 normal individuals have been analysed using a Digitizer (Calcomp 9000), in order to obtain, for each subject, a mean QRS (M-QRS), QT (M-QTe), QTc (M-QTec), JT (M-JT), JTc (M-JTc) from all the measured intervals of the 12 standard ECG leads. QRS, QT and QTc dispersions (QRSd, QTd, QTcd) were defined as the difference between the maximal and minimal QRS, QTe and Qtec values calculated in the various leads. We attained the following results: patients with WPW syndrome exhibited, with respect to controls, longer M-QRS (P < 0.001) and M-QTec (P < 0.001) values, despite similar M-QTe (P = NS), M-JT (P = NS) and M-JTc (P = NS). QRSd did not differ in the two groups(P = NS), while QTd and QTcd both resulted significantly greater in pre-excited subjects (P < 0.001). In the WPW group, QRSd was not related either to QTd (r = 0.325, P = NS) or to QTcd (r = 0.148, P = NS), while in the controls there was a significant relation between QRSd and both QTd (r = 0.522, P = 0.004) and QTcd (r = 0.379, P = 0.042). Our findings suggest that the presence of ventricular pre-excitation does not determine a prolongation of the mean ventricular recovery time, but increases regional discrepancies of the re-polarization process. This assumption is supported by the observation of greater values of QTd and QTcd associated with a similar QRSd.

[An unusual case of ectopic atrial tachycardia: triggered activity as an arrhythmogenic mechanism]. / Un insolito caso di tachicardia atriale ectopica: attività triggerata come meccanismo aritmogeno.

We report a rare case of ectopic atrial tachycardia induced by ergometric stress test whose arrhythmogenic mechanism, after transesophageal electrophysiological study, seemed to be triggered activity. The patient was successfully treated with a beta-blocker (metoprolol), confirming the importance of autonomic modulation in the genesis of arrhythmias caused by afterdepolarizations.

[Sotalol, propafenone, and flecainide: compared multiparametric analysis of ventricular repolarization in subjects without organic cardiopathy]. / Sotalolo, propafenone e flecainide: analisi comparata multiparametrica della ripolarizzazione ventricolare in soggetti esenti da cardiopatie organiche.

Antiarrhythmic drugs are known to affect depolarization and repolarization time in a different fashion. The aim of the present study was to compare the effects of sotalol, flecainide and propafenone on some common (mean QT and QTc, mean JT and JTc), or uncommon (QTc dispersion, T-peak to T-end interval-Tp-Te) electrocardiographic parameters in order to evaluate the effects of these antiarrhythmic drugs on repolarization time. QTc dispersion, defined as the difference between maximum and minimum QTc calculated from the standard 12 ECG leads, and the average Tp-Te interval, reflect regional variation in ventricular repolarization. We have analyzed retrospectively the standard 12-lead electrocardiograms of 28 patients (15 females and 13 males, age 36.11 +/- 16 years, range 11-67 years), recorded in the free-drug state and at the steady state after oral treatment with sotalol (160 mg/ die), flecainide (200 mg/die) and propafenone (450 mg/die). These drugs were prescribed, separately, for the treatment of patients with supraventricular tachycardia without underlying structural heart disease. Sotalol treatment prolongs ventricular repolarization times (QT, p = 0.0001; JT, p = 0.0001 and JTc, p = 0.0001) in an homogeneous fashion, as showed by the significant decrease in QTc dispersion (p = 0.026) and Tp-Te interval (p = 0.011). On the contrary, flecainide treatment is associated with an increase in QTc dispersion (p = 0.039) and Tp-Te interval (p = 0.0001), mean QT (p = 0.0001), QTc (p = 0.0001) and QRS (p = 0.0001), with no significant changes in JT and JTc (NS). Propafenone treatment does not affect repolarization time indexes, affecting only depolarization time as expressed by an increase in QRS (p = 0.046).

[The pharmacological treatment of supraventricular atrioventricular nodal reentry or accessory pathway reentry tachycardias: the usefulness of transesophageal electrophysiological study in the selection of therapy]. / Trattamento farmacologico delle tachicardie sopraventricolari da rientro nodale atrioventricolare o da rientro per via accessoria: utilità dello studio elettrofisiologico transesofageo nella selezione della terapia.

Transesophageal atrial pacing is a diagnostic and therapeutic tool in patients with supraventricular reciprocating tachycardia (SVRT). The aim of the present study was to evaluate the effectiveness of transesophageal atrial pacing in the selection of the chronic treatment of SVRT. Between June 1993 and March 1995 we have performed transesophageal atrial pacing in 44 patients affected by atrioventricular nodal reentry tachycardia (AVNRT: n = 28) or atrioventricular reentrant tachycardia (AVRT) using a concealed or manifest bypass tract (n = 16). After a basal (free drug state) transesophageal atrial pacing, we performed serial electropharmacological tests during chronic treatment with sotalol (160 mg/die), flecainide (200 mg/die) and propafenone (450 mg/die). At the end of these tests, the patients were finally discharged with the drug that allowed a more difficult induction or a wider cycle length, and that showed a better clinical tolerance. At the end of the electropharmacological tests 53.6% of the patients affected by AVNRT were discharged with sotalol, 17.8% with propafenone and 28.6% with flecainide. The follow-up of these 28 patients is 11.4 +/- 1.7 months. In the 79.2% of the patients the drug is still effective (absence of whatever episode of SVRT in the follow-up period). In the AVRT group, at the end of the electropharmacological tests, 25% of the patients were discharged with sotalol, 6.25% with propafenone, and 68.75% with flecainide. The follow-up of these 16 patients is 11.7 +/- 1.8 months. In the 78.6% of the patients the drug is still effective (absence of episode of SVRT in the follow-up period).