Methylation of the Opaque2 box in zein genes is parent-dependent and affects O2 DNA binding activity in vitro.

In the maize endosperm, the expression of the subfamily 4 (SF4) of the zein genes is under the transcriptional control of the Opaque2 (O2) basic leucine zipper transcriptional activator, which binds to the O2-box 5'-TCCACGTAGA-3'. Southern experiments showed that the O2-box core sequence ACGT is heavily methylated in sporophytic tissues but becomes hypomethylated in the endosperm. DNA analyses of two inbred lines and their reciprocal crosses indicate that the hypomethylation state is established on the maternal complements of the endosperm. Electrophoretic mobility shift assay (EMSA) and southwestern experiments with endosperm protein extracts and recombinant O2 using oligonucleotides with methylated and unmethylated cytosines in the O2-box indicate an inhibitory effect of modified sequences on O2-binding activity. These results suggest that DNA methylation modulates O2 activity in vivo and shed light on molecular mechanisms involved in the parent-dependent zein gene expression in maize endosperm.

Specific combinations of zein genes and genetic backgrounds influence the transcription of the heavy-chain zein genes in maize opaque-2 endosperms.

The transcript levels of heavy-chain zein genes (zH1 and zH2) and the occurrence of the zH polypeptides in different opaque-2 (o2) lines were investigated by RNA-blot analyses and by sodium dodecylsulfate-polyacrylamide gel electrophoresis or two-dimensional gel electrophoresis protein fractionations. Four mutant alleles o2R, o2T, o2It, and o2-676 introgressed into different genetic backgrounds (GBs) were considered. The mono-dimensional gel electrophoresis zein pattern can be either conserved or different among the various GBs carrying the same o2 allele. Likewise, in the identical GB carrying different o2 alleles, the zein pattern can be either conserved or differentially affected by the different mutant allele. Zein protein analysis of reciprocal crosses between lines with different o2 alleles or the same o2 showed in some case a more than additive zH pattern in respect to the o2 parent lines. Electrophoretic mobility shift assay approaches, with O2-binding oligonucleotide and endosperm extracts from the above o2 lines, failed to reveal o2-specific retarded band in any of the o2 extracts. The results suggest that the promoter of some zH1 and zH2 contains motif(s) that can respond to factors other than O2.

Impaired left ventricular filling in hypertensive left ventricular hypertrophy as a marker of the presence of an arrhythmogenic substrate.

OBJECTIVE: To assess the prevalence of ventricular late potentials and ventricular tachycardia in hypertensive subjects with left ventricular hypertrophy and to study their relation to clinical characteristics. SETTING: Teaching and general hospital in Padua. METHODS: 107 hypertensive subjects with echocardiographic signs of left ventricular hypertrophy were studied with signal averaged electrocardiography and 24 hour Holter monitoring. Signal averaged electrocardiogram analysis was performed with high pass filters of 25 Hz, 40 Hz, and 80 Hz. Ventricular late potentials were considered to be present if at least two determinants of the signal averaged electrocardiogram were abnormal in one of the three filters. 70 normotensive subjects served as age matched controls. RESULTS: 25% (27) of the hypertensive subjects and 6% (four) of the controls showed late potentials on signal averaged electrocardiography (P < 0.0001). The hypertensive subjects with late potentials had a higher prevalence of ventricular tachycardia (33%, 9/27) than those without late potentials (13%, 10/80; P = 0.035). Twenty nine per cent (31/107) of the hypertensive subjects had an inversion of the early to atrial filling velocity (E/A ratio < 1) on Doppler analysis of transmitral flow. Within this group the percentage of subjects with late potentials (55%, 17/31) and ventricular tachycardia (42%, 13/31) was much greater than that within the group of subjects without an inverted E/A ratio (13%, 10/76 (P < 0.0001) and 12%, 9/76 (P = 0.001) respectively). In a multivariate analysis only the E/A ratio was related to the presence or absence of either late potentials (P = 0.0001) or ventricular tachycardia (P = 0.0008). Both late potentials and ventricular tachycardia were unrelated to left ventricular mass, geometry, and systolic performance. CONCLUSIONS: A relation was found between the occurrence of ventricular tachycardia and the presence of late potentials in hypertensive subjects with left ventricular hypertrophy. Impaired left ventricular filling was the main marker for the arrhythmogenic substrate present in this disease.

[Relations between ventricular late potentials and ventricular arrhythmias in mitral valve prolapse]. / Relazione tra potenziali tardivi ventricolari e aritmie ventricolari nel prolasso valvolare mitralico.

BACKGROUND: The aim of the present study was to assess the prevalence and the clinical significance of ventricular late potentials in mitral valve prolapse. METHODS: Two hundred subjects (126 women and 74 men) with mitral valve prolapse, and a mean age of 37 +/- 17 years, were studied. Fifty eight per cent of them exhibited signs of mitral regurgitation at Doppler analysis of mitral flow. A 24-hour Holter recording and a signal-averaged electrocardiogram were performed in all the patients. Late potentials were considered present if the filtered QRS complex was > 110 ms and the root-mean-square amplitude in the last 40 ms of the filtered QRS was < 25 microV after 25 Hz filtering and respectively > 114 ms and < 20 microV after 40 Hz filtering. The duration of low-amplitude signals < 40 mV had to be > 38 ms. RESULTS: Ventricular late potentials were detected in 45 patients (22.5%) and were unrelated to subjects age, sex and electrocardiographic ST-T changes. Fourty one per cent of the subjects exhibited lown class > or = 3 ventricular extrasystoles at Holter ECG monitoring, while the remaining subjects (59%) had Lown classes < 3 ventricular arrhythmias. Complex ventricular arrhythmias were more common in the subjects who exhibited late potentials (55.5%) than in the remaining population (36.7%) (p < 0.03). A higher frequency of late potentials was found in the patients with mitral regurgitation (34.7%) than in those without (5.8%) (p < 0.0001). In the 55 subjects who manifested mitral regurgitation and complex ventricular arrhythmias, the prevalence of late potentials was 43.6%, while in the 61 without complex arrhythmias the prevalence was 26.6% (p = 0.05). CONCLUSIONS: In subjects with mitral valve prolapse the signal-averaged electrocardiogram allows to identify a subgroup of patients with more serious ventricular arrhythmias. Mitral regurgitation seems to be the main determinant of the arrhythmogenic substrate present in these patients.

Annular enlargement during aortic valve replacement: preliminary results with a simplified technique.

A simplified technique has been used to enlarge the aortic annulus in a series of 13 patients undergoing aortic valve replacement. The procedure basically consists of extending the aortotomy incision into the aortic annulus by dividing the commissure between the left and noncoronary sinuses, without involving the anterior mitral leaflet. Wide opening of the commissure is obtained and the resulting defect is closed, preferably using a patch of bovine pericardium sutured to the mitral annulus and aortic wall. This technique is simple, reproducible, avoids opening of the left atrium (reducing the potential bleeding sites), allows insertion of a prosthesis at least two sizes larger than the original annulus, and is also applicable in cases of mitral-aortic valve replacement. Our preliminary results are satisfactory and seem to demonstrate that in many patients, even in the young age group, more complex procedures are often unnecessary when enlargement of the aortic annulus is required.

[Follow-up using echocardiography and ambulatory electrocardiography of patients after excision of intracardiac myxoma]. / Follow-up ecocardiografico e con elettrocardiografia dinamica in soggetti sottoposti ad asportazione di mixoma intracardiaco.

From November 1968 to May 1990, 56 patients, 19 male and 37 female (mean age 49 +/- 14 years) underwent excision of an intracardiac myxoma (M). M was located into the left atrium in 48 (86%), the right atrium in 6 (11%), and the right ventricle in 2 (3.5%). Operation consisted of excision of the tumor together with its base of attachment. There were 2 early (3.5%) and 2 late (3.7%) deaths. Actuarial survival at 20 years is 91 +/- 4%. Non-invasive reevaluation has been carried out in 44 patients (84%), 39 with left atrial M, 4 with right atrial M, and 1 with right ventricular M. 2-D echocardiography ruled out tumor recurrence in all patients and showed, in those with left atrial M, a reduction in the size of the atrial chamber; on the contrary, left ventricular systolic diameter, diastolic diameter and ejection fraction were unmodified. In 7 patients (15.9%) a residual mild mitral insufficiency was disclosed. In 34 patients 24-hour electrocardiographic monitoring reevaluation showed a low incidence of major supraventricular arrhythmias, late postoperatively (short runs of paroxysmal supraventricular tachycardia in 3 patients, and atrial ectopic rhythm in 1). All these patients had undergone tumor excision by biatrial approach. Based on our results, we conclude that excision of intracardiac myxomas is curative and long-term survival is excellent. Non-invasive reevaluation of patients by 2-D echocardiography and 24-hour electrocardiographic monitoring is mandatory in order to promptly disclose possible complications, particularly tumor recurrence and arrhythmias.