N-(2-Mercaptoethyl)picolylamine (MEPAH) was studied as a potentially biologically relevant ligand for the "fac-M(CO)(3)(+)" core (M = Re, (99)Tc, (99m)Tc). To this end, the complex Re(CO)(3)(MEPA) ...was synthesized. The reaction of MEPAH with fac-Re(CO)(3)(MeCN)(3)(+) took place over the course of seconds, showing the high affinity possessed by this ligand for the "fac-Re(CO)(3)(+)" core. A single-crystal X-ray diffraction study was performed confirming the nature of Re(CO)(3)(MEPA), a rare mononuclear rhenium(I) thiolate complex. Additional exploration into derivatization of the ligand backbone has afforded the analogous N-ethyl complex, Re(CO)(3)(MEPA-NEt). The high affinity of the ligand for the metal coupled with the ease of its derivatization implies that utilization of this ligand system for the purposes of (99m)Tc-radiopharmaceutical development is promising.
The Great Recession, institutional dysfunction, a growing divide between urban and rural prospects, and failed efforts to effectively address immigration have paved the way for a populist backlash ...that disrupts the postwar bargain between political elites and citizens. Whether today's populism represents a corrective to unfair and obsolete policies or a threat to liberal democracy itself remains up for debate. Yet this much is clear: these challenges indict the triumphalism that accompanied liberal democratic consolidation after the collapse of the Soviet Union. To respond to today's crisis, good leaders must strive for inclusive economic growth while addressing fraught social and cultural issues, including demographic anxiety, with frank attention. Although reforms may stem the populist tide, liberal democratic life will always leave some citizens unsatisfied. This is a permanent source of vulnerability, but liberal democracy will endure so long as citizens believe it is worth fighting for.
The reduction of ammonium pertechnetate with bis(diphenylphosphino)methane (dppm), and with diphenyl-2-pyridyl phosphine (Ph(2)Ppy), has been investigated. The neutral Tc(II) complex, ...trans-TcCl(2)(dppm)(2) (1), has been isolated from the reaction of (NH(4))TcO(4) with excess dppm in refluxing EtOH/HCl. Chemical oxidation with ferricinium hexafluorophosphate results in formation of the cationic Tc(III) analogue, trans-TcCl(2)(dppm)(2)(PF(6)) (2). The dppm ligands adopt the chelating bonding mode in both complexes, resulting in strained four member metallocycles. With excess PhPpy, the reduction of (NH(4))TcO(4) in refluxing EtOH/HCl yields a complex with one chelating Ph(2)Ppy ligand and one unidentate Ph(2)Ppy ligand, mer-TcCl(3)(Ph(2)Ppy-P,N)(Ph(2)Ppy-P) (3). The cationic Tc(III) complexes, trans-TcCl(2)(Ph(2)P(O)py-N,O)(2)(PF(6)) (4) and trans-TcCl(2)(dppmO-P,O)(2)(PF(6)) (5) (Ph(2)P(O)py = diphenyl-2-pyridyl phosphine monoxide and dppmO = bis(diphenylphosphino)methane monoxide), have been isolated as byproducts from the reactions of (NH(4))TcO(4) with the corresponding phosphine. The products have been characterized in the solid state and in solution via a combination of single-crystal X-ray crystallography and spectroscopic techniques. The solution state spectroscopic results are consistent with the retention of the bonding modes revealed in the crystal structures.
Purpose: This report summarizes our experience with epidural cooling (EC) to achieve regional spinal cord hypothermia and thereby decrease the risk of spinal cord ischemic injury during the course of ...descending thoracic aneurysm (TA) and thoracoabdominal aneurysm (TAA) repair.
Methods: During the interval July 1993 to Dec. 1995, 70 patients underwent TA (n = 9, 13%) or TAA (n = 61) (type I, 24 34%, type II, 11 15%, type III, 26 37%) repair using the EC technique. The latter was accomplished by continuous infusion of normal saline (4° C) into a T11-12 epidural catheter; an intrathecal catheter was placed at the L3-4 level for monitoring of cerebrospinal fluid temperature (CSFT) and pressure (CSFP). All operations (one exception, atriofemoral bypass) were performed with the clamp-and-sew technique, and 50% of patients had preservation of intercostal vessels at proximal or distal anastomoses (30%) or by separate inclusion button (20%). Neurologic outcome was compared with a published predictive model for the incidence of neurologic deficits after TAA repair and with a matched (Type IV excluded) consecutive, control group (n = 55) who underwent TAA repair in the period 1990 to 1993 before use of EC.
Results: EC was successful in all patients, with a 1442 ± 718 ml mean (range, 200 to 3500 ml) volume of infusate; CSFT was reduced to a mean of 24° ± 3° C during aortic cross-clamping with maintenance of core temperature of 34° ± 0.8± C. Mean CSFP increased from baseline values of 13 ± 8 mm Hg to 31 ± 6 mm Hg during cross-clamp. Seven patients (10%) died within 60 days of surgery, but all survived long enough for evaluation of neurologic deficits. The EC group and control group were well-matched with respect to mean age, incidence of acute presentations/aortic dissection/aneurysm rupture, TAA type distribution, and aortic cross-clamp times. Two lower extremity neurologic deficits (2.9%) were observed in the EC patients and 13 (23%) in the control group (p < 0.0001). Observed and predicted deficits in the EC patients were 2.9% and 20.0% (p = 0.001), and for the control group 23% and 17.8% (p = 0.48). In considering EC and control patients (n = 115), variables associated with postoperative neurologic deficit were prolonged (>60 min) visceral aortic cross-clamp time (relative risk, 4.4; 95% CI, 1.2 to 16.5; p = 0.02) and lack of epidural cooling (relative risk, 9.8; 95% CI, 2 to 48; p = 0.005).
Conclusion: EC is a safe and effective technique to increase the ischemic tolerance of the spinal cord during TA or TAA repair. When used in conjunction with a clamp-and-sew technique and a strategy of selective intercostal reanastomosis, EC has significantly reduced the incidence of neurologic deficits after TAA repair. (J Vasc Surg 1997;25:234-43.)
A new route to low-valent technetium complexes containing multiple acetonitrile ligands has been developed. The reduction of TcCl(4)(PPh(3))(2) with zinc metal dust in acetonitrile results in the ...formation of Tc(CH(3)CN)(4)(PPh(3))(2)Zn(2)Cl(6)(1/2). The hexafluorophosphate salt of the analogous Tc(II) cation can be prepared via chemical oxidation of the Tc(I) species, and the Tc(I) cation can be regenerated via chemical reduction. The compounds have been characterized in the solid state via single-crystal X-ray crystallography, and in solution via a combination of spectroscopic techniques and cyclic voltammetry. The structural parameters found in the two complexes are similar to each other; however, the difference in oxidation state is reflected, as expected, in the spectroscopic results. The electrochemical data, obtained from cyclic voltammograms of Tc(CH(3)CN)(4)(PPh(3))(2)(PF(6))(n)() (n = 1,2), mirror the synthetic results in that both compounds possess a reversible redox couple at -0.55 V versus ferrocene, which has been assigned to the Tc(II)/Tc(I) couple.
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