Stabilities and isomeric equilibria in solutions of monomeric metal-ion complexes of guanosine 5'-triphosphate (GTP4-) and inosine 5'-triphosphate (ITP4-) in comparison with those of adenosine 5'-triphosphate (ATP4-).

Under experimental conditions in which the self-association of the purine-nucleoside 5'-triphosphates (PuNTPs) GTP and ITP is negligible, potentiometric pH titrations were carried out to determine the stabilities of the M(H;PuNTP) and M(PuNTP)2-complexes where M2+ = Mg2+, Ca2+, Sr2+. Ba2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, or Cd2+ (I = 0.1 M, 25 degrees C). The stabilities of all M(GTP)2- and M(ITP)2- complexes are significantly larger than those of the corresponding complexes formed with pyrimidine-nucleoside 5'-triphosphates (PyNTPs), which had been determined previously under the same conditions. This increased complex stability is attributed, in agreement with previous 1H MNR shift studies, to the formation of macrochelates of the phosphate-coordinated metal ions with N7 of the purine residues. A similar enhanced stability (despite relatively large error limits) was observed for the M(H;PuNTP) complexes, in which H+ is bound to the terminal y-phosphate group, relative to the stability of the M(H;PyNTP)- species. The percentage of the macrochelated isomers in the M(GTP)2- and M(ITP)2- systems was quantified by employing the difference log KMM(PuNTP)-log KMM(PyNTP); the lowest and highest formation degrees of the macrochelates were observed for Mg(ITP)2- and Cu(GTP)2- with 17 +/- 11% and 97 +/- 1%, respectively. From previous studies of M(ATP)2- complexes, it is known that innersphere and outersphere macrochelates may form; that is, in the latter case a water molecule is between N7 and the phosphate-coordinated M2+. Similar conclusions are reached now by comparisons with earlier 1H MNR shift measurements, that is, that Mg(GTP)2- (21 +/- 11%), for example, exists largely in the form of an outersphere macrochelate and Zn(GTP)2- (68 +/- 4%) as an innersphere one. Generally, the overall percentage of macrochelate falls off for a given metal ion in the order M(GTP)2- > M(ITP)2- > M(ATP)2-; this is in accord with the decreasing basicity of N7 and the steric inhibition of the (C6)NH2 group in the adenine residue. Furthermore, although the absolute stability constants of the previously studied M(GMP), M(IMP), and M(AMP) complexes differ by about two to three log units from the present M(PuNTP)2- results, the formation degrees of the macrochelates are astonishingly similar for the two series of nucleotides for a given metal ion and purine-nucleobase residue. The conclusion that N7 of the guanine residue is an especially favored binding site for metal ions is also in accord with observations made for nucleic acids.

[The mitral prolapse syndrome. Observation of 100 cases (author's transl)]. / La sindrome del prolasso della mitrale. Osservazioni su 100 casi

100 patients with mitral prolapse syndrome (MPS) were studied with electrocardiogram, phonocardiogram, thorax radiography and echocardiogram. In 44 of the patients, the effort test and dynamic electrocardiogram were performed; 25 underwent hemodynamic examination, and 10 underwent selective coronarography. The most frequent symptomatologies were palpitations and vertigo; the most-registered electrocardiographic alterations were ventricular extrasystoles and altered electrical repolarization in the inferior seat. The symptomatic patients with rhythm disturbances showed reduced work capacity (RWC) with aggravation of the effort arrhythmias. The phonocardiogram showed variability of the phonoauscultatory reports, not only from patient to patient, but also in the same patient. The apicocardiogram presented a characteristic systolic re-entry which coincided with the non-ejective click. In all cases, the echocardiogram demonstrated a systolic movement backwards from the mitralic strips with different aspects. The endocavitary pressures in the studied cases were normal or only slightly altered. The left ventriculography frequently demonstrated assynergic areas, and constantly, eversion of the posterior mitralic strips in the left atrium. In most of the cases, the selective coronarography showed the absence of the ventricular atrial tract of the circumflex. The sustained role of the mixomatous degeneration in the pathogenetic mechanism of the MPS must be emphasized. The beta-blockers were the most effective drugs against arrhythmias, which in some cases showed themselves impervious to any medicinal treatment. MPS is considered a very diffuse disease which can run its course without detection or which can be accompanied by serious rhythm disturbances that can threaten the patient's life. The importance of echocardiography in the diagnosis of MPS is emphasized. The SPM patient showed undergo a series of wave tests which reveal malignant potentialities, so that the best therapeutic principles, both for the treatment and prevention of the arrhythmias, can be applied.