A method of simultaneous dual-radionuclide cardiac imaging with technetium 99m and thallium 201. I: Analysis of interradionuclide crossover and validation in phantoms

Background  

Simultaneous dual-radionuclide technetium 99m/thallium 201 scintigraphy can potentially produce perfectly aligned stress and rest images in less time than conventional protocols. However, interradionuclide crossover limits diagnostic accuracy. Accordingly, we evaluated^99mTc and²⁰¹Tl crossover in line and heart phantoms.     

Molecular properties and structure-function relationships of lethal peptides from venom of Wagler's pit viper, Trimeresurus wagleri.

Two new lethal peptides (waglerins) were purified from the venom of Trimeresurus wagleri, and sequenced. We found them to be analogs of lethal peptides (waglerins) I and II reported previously (Weinstein et al., Toxicon 29, 227-236, 1991), with an additional Ser-Leu on the amino terminus. Three of the four waglerins were synthesized and the products were chemically and biologically equivalent to the naturally occurring counterparts in venom. Murine i.p. LD50 for synthetic waglerins I, SL-I and II were 0.33, 0.22, and 0.51 mg/kg, respectively. The single, intramolecular disulfide bond in each synthetic peptide formed rapidly in high yield. The reduced (cysteine-containing) forms of the peptides appeared to have significant toxicities, even without prior disulfide bond formation, but synthetic analogs with serine substituted for cysteine were not toxic. The synthetic dimer of waglerin I, formed by two intermolecular disulfide bonds, was not toxic, but rapidly rearranged to lethal, monomeric waglerin I at alkaline pH upon the addition of 5 mM beta-mercaptoethanol. Waglerin I was inactivated by cleavage at Tyr-15 with chymotrypsin.     

Rupture of the posterior tibial tendon: CT and surgical findings

Computed tomography (CT) was performed in 42 patients with 49 clinically suspected tears of the posterior tibial tendon. Twenty-eight of the 49 suspected tears were subsequently surgically explored and repaired. Three patterns of tendon abnormalities were recognized on CT scans: type I-intact, hypertrophied, heterogeneous tendon; type II-attenuated tendon; and type III-absence of a portion of a tendon. Types I and II correlated with partial rupture seen during surgery, and type III correlated with complete rupture of the tendon. CT findings were accurate in 96% of the patients who underwent surgery. In four cases (14%), tendon rupture was seen on CT scans, but the extent of the injury was underestimated and the rupture was misclassified. Reactive periostitis of the distal tibia was seen in 71% of diseased tendons and may represent an important factor in the diagnosis of tendon rupture.     

Computerized cortical surface electroencephalography after temporary middle cerebral artery occlusion in rabbits

The sensitivity and regional specificity of intraoperative electroencephalographic (EEG) monitoring in cerebral ischemia was evaluated in a new experimental model of temporary focal cerebral ischemia in rabbits. EEG potentials were recorded directly from the cortical surface using a bipolar disc electrode grid and were analyzed by computer. Groups of 5 animals each underwent temporary occlusion of the left middle cerebral arterial trunk for 5, 10, 20, 30, 45, or 60 minutes. EEG data were recorded from the cortex proximal (temporal site) and distal (parasagittal site) to the middle cerebral arterial trunk during occlusion and 2 hours of reperfusion. EEG suppression was detected immediately after occlusion at the temporal site by analysis of power spectra in 29 of 30 rabbits (mean power, 32% of base line), by compressed spectral array (CSA) edge analysis in 23, and by analysis of the conventional EEG wave form in 24. Within 5 minutes after the start of occlusion, all 30 rabbits showed EEG power suppression and 26 showed decrease in the CSA edge frequency or in the routine EEG wave form. By the end of the occlusion period, EEG power at the temporal site had decreased to 20.5% of base line. At the parasagittal site, a lesser degree of EEG suppression was detected; 20 rabbits had an initial loss of EEG power (mean, 85.7% of base line), 13 had decrease in the CSA edge, and 7 had suppression of the EEG wave form. By the end of the occlusion period, spectral power at the parasagittal site had decreased in 25 of 30 rabbits to a mean of 86.9% of base line.(ABSTRACT TRUNCATED AT 250 WORDS)