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PubMed2004

Structural effects of the lone pair on lead(II), and parallels with the coordination geometry of mercury(II). Does the lone pair on lead(II) form H-bonds? Structures of the lead(II) and mercury(II) complexes of the pendant-donor macrocycle DOTAM (1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane).

The synthesis and structures of [Pb(DOTAM)](ClO4)2.4.5H2O (1) and [Hg(DOTAM)](ClO4)2.0.5CH3OH.1.5H2O (2) are reported, where DOTAM is 1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane. Compound 1 is triclinic, space group P, a = 12.767(3) A, b = 13.528(2) A, c = 18.385(3) A, alpha = 101.45(2) degrees, beta = 93.32(2) degrees, gamma = 90.53(2) degrees, Z = 4, R = 0.0500. Compound 2 is monoclinic, space group Cc, a = 12.767(3) A, b = 13.528(2) A, c = 18.385(3) A, beta = 101.91(2) degrees, Z = 4, R = 0.0381. The Pb(II) ion in 1 has an average Pb-N = 2.63 A to four N-donors from the macrocyclic ring, and four O-donors (average Pb-O = 2.77 A) from the amide pendant donors of the macrocycle, with a water molecule placed with Pb-O = 3.52 A above the proposed site of the lone pair (Lp) on Pb. The Hg(II) in 2 appears to be only six-coordinate, with four Hg-N bond lengths averaging 2.44 A, and two Hg-O from pendant amide donors at 2.41 A. The other two amide donors appear to be noncoordinating, with Hg-O distances of 2.74 and 2.82 A. A water situated 3.52 A above the proposed site of the lone pair on Pb(II) in 1 is oriented in such a way that it might be thought to be forming a Pb-Lp.H-O-H hydrogen bond. It is concluded that that this is not an H-bond, but that the presence of the lone pair allows a closer approach of the hydrogens to Pb than would be true otherwise. The structural analogy in the VSEPR sense between Pb(II), which has the 5d(10)6s(2) outer electron structure, and the Hg(II) ion, which has the 5d10 structure, is examined. The tendency of Hg(II) toward linear coordination, with two short Hg-L bonds (L = ligand) at 180 degrees to each other, and other donor groups at roughly 90 degrees to this and at much longer bond distances, is paralleled by Pb(II). One of the short Hg-L bonds is replaced in the Pb(II) structures by the lone pair (Lp), which is opposite the short Pb-L bond, or in some cases 2-4 shorter Pb-L bonds.

Journal Article↗
PubMed2006

A one-dimensional mixed-anion lead(II) coordination polymer: catena-poly[[(1,10-phenanthroline)lead(II)]-mu-benzoato-mu-nitrato-[(1,10-phenanthroline)lead(II)]-di-mu-benzoato].

In the title polymeric compound, [Pb2(C7H5O2)3(NO3)(C12H8N2)2]n, both independent Pb atoms adopt an eight-coordinate geometry formed by one nitrate, three benzoate and one 1,10-phenanthroline ligand. The one-dimensional polymer consists of dimeric [Pb2(C7H5O2)3(NO3)(C12H8N2)2] units, in which all nitrate and benzoate ligands act in a bridging-chelating coordination mode.

Journal Article↗
PubMed1972

Viruses of Entamoeba histolytica. II. Morphogenesis of the polyhedral particle (ABRM 2 leads to HK-9) leads to HB-301 and the filamentous agent (ABRM) 2 leads to HK-9.

The intracellular development of two morphologically different amoebal viruses has been studied by electron microscopy. One is a polyhedral agent which was observed as early as 24 hr after infection in the perinuclear cytoplasm. Subsequently, cell lysis occurred and particles were found in large number bound to membranes of disrupted amoebae. Other particles were found in phagocytic vacuoles suggesting a possible portal of entry into amoebae. The other virus is a filamentous particle which is first seen in small clusters in the nucleus after 24 hr of infection. The number of particles increases such that by 72 hr massive whorls of particles occupy a substantial part of the nucleus. After rupture of the nuclear membrane, clusters of filaments are widely dispersed throughout the cytoplasm. Still later, the cytoplasmic membrane disintegrates and clusters of filaments are found extracellularly, but free of cell membranes. The morphology of these agents is discussed in comparison with a variety of plant, animal, and bacterial viruses.

Cell Membrane↗
PubMed1979

The single precordial lead for ST segment monitoring: comparison with the multiple lead map.

ST segment elevation, used as an index of the relative extent of myocardial ischemic injury, was measured using a single precordial lead located at the point of maximum ST elevation. ST changes were followed for two hours after acute coronary occlusion in pigs, and were compared to the sum of ST elevation recorded with an 18 lead precordial map. Some animals were subjected to Reperfusion (n = 12), others to infarct extension (n = 10), while a control group (n = 9) was followed without an ST-modifying intervention. Correlation between sigmaST and ST in the single lead was good, with a correlation coefficient of 0.844 at 360 points of comparison. Time to peak ST elevation using the single lead technique was comparable to that using the 18 lead map. Changes in the ST elevation using both techniques were similarly reduced following reperfusion, increased following extension, and followed a similar downslope pattern in the unmodified infarct group. This single lead technique offers the advantage of simplicity of use without sacrifice of accuracy. Its use can facilitate clinical studies of myocardial ischemic injury and its modification.

Animals↗
PubMed2004

New electrocardiographic criteria for identifying the culprit artery in inferior wall acute myocardial infarction-usefulness of T-wave amplitude ratio in leads II/III and T-wave polarity in the right V5 lead.

ST-segment elevations in the right ventricular lead and those greater in lead III than in lead II strongly suggest that right, rather than left circumflex, coronary arterial occlusion occurs in acute myocardial infarction in the inferior wall. Our study demonstrated that, in the very early stages of infarction, a T-wave amplitude that is greater in lead III than in lead II and an upright or positive biphasic T wave in lead V(5)R are just as predictive as ST-segment changes and are often easier to measure.

Arteries↗
PubMed2004

The 13th multiuse ECG lead: shouldn't we use it more often, and on the same hard copy or computer screen, as the other 12 leads?

Although the ECG diagnosis of cardiac pathology is well served by the employment of the standard 12 ECG leads, an occasional need arises that additional leads might provide a diagnostic advantage. To this effect it is proposed that a space is provided in the standard 12-lead ECG printed report for a "13th multiuse ECG lead"; such a lead, which will be referenced to the "central Wilson's terminal," would provide additional information from various chest wall locations (V3R-V6R, posterior [left parascapular]) or other regions. Also such a lead could provide intracardiac electrograms via intracardiac recording wires or metallic or normal saline-filled catheters.

Electrocardiography↗
PubMed2003

Beyond the 12 lead: review of the use of additional leads for the early electrocardiographic diagnosis of acute myocardial infarction.

Despite known limitations, the standard 12 lead ECG is the principal risk stratification device for patients presenting with chest pain to the ED. However, it has a sensitivity of less than 60% for MI. One reason for this is that the standard placement of chest leads fails to interrogate many areas of the myocardium. Various workers have addressed this problem through the use of additional leads or body surface mapping. Additional leads on the posterior and right thoracic surface have been shown to give additional information, which may be important to the emergency physician. This review demonstrates the need for additional leads in the acute setting and makes recommendations about the utility of using additional leads in the ED.

Body Surface Potential Mapping↗