High-attenuating crescent in abdominal aortic aneurysm wall at CT: a sign of acute or impending rupture.

PURPOSE: To determine whether a peripheral high-attenuating crescent in an abdominal aortic aneurysm (AAA) on unenhanced computed tomographic (CT) scans is a sign of impending or active aneurysm rupture. MATERIALS AND METHODS: CT scans were reviewed of 149 consecutive patients operated on because of AAA who had undergone preoperative unenhanced CT scanning. The presence of a peripheral high-attenuating crescent on CT scans was correlated with surgical findings of aneurysm complication. Aneurysm diameter was correlated with presence or absence of pain at the time of CT, high-attenuating crescent, and aneurysm complication. RESULTS: Sensitivity of the high-attenuating crescent sign as an indication of complicated aneurysm was 77%; specificity, 93%; and positive predictive value, 53%. The sign showed a statistically significant correlation with large aneurysm size (P < .001) and presence of pain at the time of CT (P < .003). CONCLUSION: In patients without CT evidence of frank aneurysm leak, the high-attenuating crescent sign should be regarded as a sign of impending AAA rupture, particularly in patients with pain.

Does CTAP prior to hepatic resection improve patient survival rates?

The purpose of our study was to compare survival rates of colon carcinoma patients who had undergone attempted curative hepatic resection based on liver staging by computed tomographic angiography (CTA) or portography (CTAP) with previously reported survival rates of patients who underwent similar surgery without preoperative CTAP evaluations. A total of 404 CTAP studies performed at three institutions were reviewed. Of this group, 197 had colon carcinoma. Sixty-nine of the colon patients went to surgery. Actuarial adjusted yearly survival rates were calculated for the prior CTAP colon group and compared to historical controls. The control survival data were taken from reports published prior to the CTAP era. Our study demonstrated no difference in the 1-year survival data between the groups. However, the CTAP patients had greater survival in years 2-4. This greater survival may be multifactorial but in part due to better surgical selection caused by CTAP.

Preoperative determination of the resectability of hepatic tumors: efficacy of CT during arterial portography.

OBJECTIVE: A multiinstitutional study was performed to evaluate the efficacy of CT during arterial portography for determining the resectability of hepatic tumors. The impact of findings from CT during arterial portography on patients' treatment (i.e., surgical vs nonsurgical) was assessed. In patients considered to have resectable tumors, the accuracy of CT during arterial portography for predicting surgical findings was also evaluated. MATERIALS AND METHODS: A retrospective study was done of 404 patients from three institutions who had CT during arterial portography during the period 1985-1991 as part of preoperative staging to determine the resectability of hepatic tumors. The tumors included metastases from colorectal carcinoma in 197 patients (49%); other hepatic metastases, mostly from adenocarcinoma of the stomach, pancreas, and biliary tree in 123 (30%); and primary hepatocellular carcinoma in 84 (21%). Imaging results were correlated with results of percutaneous biopsy of at least one hepatic lesion in patients whose tumors were considered unresectable. In patients whose tumors were considered resectable, results were correlated with preoperative percutaneous biopsy (obtained in almost all cases) and pathologic examination of a surgical specimen (all cases). Although each case was considered individually, four criteria were used for resectability: (1) accessibility of all lesions to lobar or wedge resection that would yield clear margins, (2) anticipation that residual liver tissue after resection would provide sufficient function, (3) the absence of invasion of central hepatic vascular or biliary structures, and (4) the absence of extrahepatic disease. No specific restriction was made with respect to the number of hepatic lesions present. The accuracy of findings by CT during arterial portography for predicting resectability was assessed in the 146 patients who had tumors that were considered resectable on the basis of imaging findings and had surgery. RESULTS: Of 404 patients, only 146 (36%) were thought to be candidates for resection on the basis of findings from CT during arterial portography. Of these, 122 (84%) actually had resection. The 24 patients who did not have resection included 22 patients with disease understaged or overstaged by CT during arterial portography, one with true-negative findings by CT during arterial portography, and one who died during surgery. The accuracy of findings by CT during arterial portography for predicting results at surgery was 85% for all patients and 91% for the subset of patients who had primary colorectal tumors with hepatic metastases. CONCLUSION: Our experience shows that CT during arterial portography is a useful procedure for assessing the resectability of hepatic tumors. In our study, 64% of patients were spared unnecessary surgery.(ABSTRACT TRUNCATED AT 400 WORDS)

A translational inhibitor from muscles of diabetic rats: identification as histone H1.

A heat- and acid-stable protein fraction that inhibited peptide chain initiation in rabbit reticulocyte lysates was extracted from frozen, powdered rat skeletal muscles by stepwise trichloroacetic acid precipitation. Streptozotocin-induced diabetes increased the inhibitory activity; this was prevented by insulin therapy. Size-exclusion high-performance liquid chromatography resolved four inhibitory fractions; only one was consistently increased (approximately 2-fold) in muscle extracts from diabetic rats. Polysome profiles of lysates incubated with this fraction indicated peptide chain initiation inhibition. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis the purified inhibitory fraction migrated with apparent Mr 30 and 32 kDa, which on Western blot immunostained with antisera against histone H1/H1(0). Perchloric acid extraction of muscle homogenates yielded approximately twofold more H1 from diabetic than from control rats; yield from diabetics decreased to control values 5 h after subcutaneous insulin injection. Inclusion of detergent during homogenization increased H1 yield more from muscles of control than from diabetic rats and abolished the difference between them. Because H1 affects several biochemical reactions, its facilitated extraction from insulin-deprived tissues can bias interpretation of studies of insulin action.

Modulation of rat skeletal muscle branched-chain alpha-keto acid dehydrogenase in vivo. Effects of dietary protein and meal consumption.

The effects of dietary protein on the activity of skeletal muscle branched-chain alpha-keto acid dehydrogenase (BCKAD) were investigated. BCKAD is rate-limiting for branched-chain amino acid (BCAA) catabolism by muscle; its activity is modulated by phosphorylation-dephosphorylation. In rats fed an adequate protein (25% casein) diet, BCKAD was approximately 2% active postabsorptively and increased to 10% or 16% active after a 25% or 50% protein meal, respectively. Prolonged feeding of a 50% protein diet increased postabsorptive BCKAD activity to 7% with further increases to 40% active postprandially. On a low protein (9% casein) diet BCKAD remained approximately 2% active regardless of meal-feeding. Dose-dependent activation of BCKAD by intravenous leucine in postabsorptive rats was blunted by a low protein diet. We conclude that excesses of dietary protein enhance the capacity of skeletal muscle to oxidize BCAA, muscle conserves BCAA when protein intake is inadequate, and skeletal muscle may play an important role in whole-body BCAA homeostasis.

Histone-H1 inhibits translation by reticulocyte lysates with relative mRNA selectivity.

Histone-H1 purified from rat skeletal muscle is a relatively potent inhibitor of peptide chain initiation in a cell free system, the rabbit reticulocyte lysate (50% inhibition at approximately 0.4 microM). H1 does not inhibit formation of the ternary complex nor its attachment to 40S ribosomes; the data are compatible with H1 binding to mRNA. The inhibition shows mRNA selectivity: translation of beta-globin mRNA is more affected than that of alpha-globin mRNA and hepatic albumin mRNA more than total hepatic mRNA. Whether or not histone-H1 plays a role in translational regulation in intact cells is conjectural, it may serve as a useful model for protein-mRNA interactions.

Glucocorticoid-mediated activation of muscle branched-chain alpha-keto acid dehydrogenase in vivo.

Muscle branched-chain alpha-keto acid dehydrogenase, the rate-limiting enzyme for branched-chain amino acid oxidation in skeletal muscle, was measured after treatment of rats with glucocorticoids. Cortisone treatment (10 mg X 100 g body wt-1 X day-1 for 2-5 days) resulted in an approximate doubling of the percentage of active enzyme. To further characterize this effect, the enzyme complex was measured 4 h after the intraperitoneal injection of 6 alpha-methylprednisolone, a water-soluble glucocorticoid with rapid onset effects. The percentage of active enzyme increased linearly as the dose of methylprednisolone was increased from 0.125 to 12.5 mg/100 g body wt, while total enzyme activity was unchanged. Administration of insulin with glucose had no significant effect on the activity of the enzyme. However, treatment of rats with insulin and glucose after methylprednisolone administration partially blocked branched-chain alpha-keto acid dehydrogenase activation. The activity of the enzyme complex was correlated with the concentration of leucine in plasma and muscle. Activation of skeletal muscle branched-chain alpha-keto acid dehydrogenase by increased glucocorticoids may play a role in the acceleration of branched-chain amino acid oxidation observed during severe stress.

Physical properties of a soluble form of the glycoprotein of vesicular stomatitis virus at neutral and acidic pH.

We have analyzed a soluble form of the glycoprotein (G) obtained from vesicular stomatitis virus (VSV) by treatment of intact virions with cathepsin D. This form lacks the carboxy-terminal and membrane-spanning domains and thus is analogous to the previously described secreted form of G, Gs. The molecular weight of the cathepsin D produced G, G(Cath D), measured by sedimentation equilibrium in the analytical ultracentrifuge is 57 600, indicating that it is a monomer. Intact G protein extracted from virions by octyl beta-D-glucoside also is monomeric, based on sedimentation equilibrium analysis. These results suggest that G may be monomeric in virions. The Stokes radii (Rs) of the two forms of G were obtained from their migration in nondenaturing polyacrylamide gradient gels. The Rs of G(Cath D) in the absence of nonionic detergent was 37 A; in the presence of nonionic detergent, it increased to 55 A. The Rs of detergent-extracted intact G was 63 A in nonionic detergent. From the molecular weight and Rs of G(Cath D), we calculated a sedimentation coefficient of 3.8 S; the value determined by centrifugation in a sucrose gradient was 3.7 S. Viruses such as VSV fuse with cell membranes at low pH [White, J., Matlin, K., & Helenius, A. (1981) J. Cell Biol. 89, 674-679]. We have used the fluorescent probe cis,trans,trans,cis-9,11,13,15-parinaric acid (cis-PnA) to detect a reversible conformational change in G(Cath D) when the protein was exposed to an acidic environment close to pH 5. cis-PnA binds to hydrophobic regions of protein, causing a quenching of the intrinsic tryptophan fluorescence and an increase in the fluorescence of the probe.