[Ultrasound-guided biopsy of the pancreas: a multicenter study]. / Punción pancreática ecodirigida: estudio multicéntrico.

OBJECTIVE: Members of "Asociación de Ecografía Digestiva" decided to carry out a multicenter retrospective study on fine-needle aspiration biopsy for pancreatic space-occupying lesions under ultrasonographic guidance and via the percutaneous route in order to assess this technique s performance versus endoscopic ultrasound-guided biopsy. SUBJECTS: 10 hospitals for a total of 222 patients with suspiciously malignant, 8-120-mm pancreatic lesions were included in the study. RESULTS: The analysis of results shows a sensitivity of 89%, a specificity of 98%, a positive predictive value of 99%, and a negative predictive value of 74%, for an overall diagnostic accuracy of 91%. No major complications occurred. CONCLUSION: Percutaneous fine-needle aspiration for pancreatic lesions is highly cost-effective and has few and mild complications.

Evidence for the presence of collagenous domains in Candida albicans cell surface proteins.

Rabbit polyclonal antibodies (PAbs) directed towards the amino-terminal cysteine-rich 7S domain (PAb anti-7S), the major internal collagenous domain (PAb anti-type IV), and the C-terminal noncollagenous region (PAb anti-NC1) of the type IV collagen molecule were probed by indirect immunofluorescence against Candida albicans blastoconidia and germinated blastoconidia. Most nongerminating cells and mother blastoconidia from which germ tubes originated showed strong fluorescence when PAb anti-7S was used, whereas with PAb anti-type IV, fluorescence was found almost exclusively on the surface of filamentous forms. A patched fluorescent pattern rather than a homogenous confluent fluorescence was observed in all cases. No fluorescent cells were observed with PAb anti-NC1. By Western immunoblotting, PAb anti-type IV cross-reacted primarily with a polypeptide of 37 kDa present in wall extracts obtained from intact cells of both growth forms by treatment with beta-mercaptoethanol, whereas PAb anti-7S recognized a major 58-kDa antigen also present in both extracts, along with some other high-molecular-mass (> 106-kDa) polydisperse species present only in the material released from blastoconidia with beta-mercaptoethanol. No reactive bands were observed when PAb anti-NC1 was used as a probe in Western immunoblotting experiments. The sensitivities or resistances to collagenase digestion of the different polypeptides that cross-reacted with PAbs anti-type IV and anti-7S suggest the existence of cell wall components in C. albicans that contain epitopes that mimic the collagenous domains of the type IV collagen molecule.

The oxidation of ubiquinol by the isolated Rieske iron-sulfur protein in solution.

The pre-steady-state redox reactions of the Rieske iron-sulfur protein isolated from beef heart mitochondria have been characterized. The rates of oxidation by c-type cytochromes is much faster than the rate of reduction by ubiquinols. This enables the monitoring of the oxidation of ubiquinols by the Rieske protein through the steady-state electron transfer to cytochrome c in solution. The pH and ionic strength dependence of this reaction indicate that the ubiquinol anion is the direct reductant of the oxidized cluster of the iron-sulfur protein. The second electron from ubiquinol is diverted to oxygen by the isolated Rieske protein, and forms oxygen radicals that contribute to the steady-state reduction of cytochrome c. Under anaerobic conditions, however, the reduction of cytochrome c catalyzed by the protein becomes mechanicistically identical to the chemical reduction by ubiquinols. The present kinetic work outlines that: (i) the electron transfer between the ubiquinol anion and the Rieske cluster has a comparable rate when the protein is isolated or inserted into the parent cytochrome c reductase enzyme; (ii) the Rieske protein may be a relevant generator of oxygen radicals during mitochondrial respiration.

ATP-dependent degradation of 125I-bovine serum albumin by rabbit reticulocytes does not need repression of an endogenous inhibitor.

The ubiquitin-dependent proteolysis of 125I-bovine serum albumin in rabbit reticulocytes has been investigated. Using various reticulocyte fractions (reticulocyte protease, inhibitor-free protease, "ubiquitin" and "inhibitor") in the presence or absence of ATP, we found that the repression of an endogenous inhibitor, as suggested by others for alpha-casein proteolysis, is unlikely for bovine serum albumin. Therefore, differences exist in the ATP-dependent proteolytic pathway of rabbit reticulocytes depending on the substrate. Fractionation of the reticulocyte ATP-dependent proteolytic system revealed at least two proteolytic and two inhibitory fractions involved in the proteolysis of bovine serum albumin.

Modification of the catalytic function of the mitochondrial cytochrome b-c1 complex by dicyclohexylcarbodiimide.

N,N'-Dicyclohexylcarbodiimide (DCCD) induces a complex set of effects on the succinate-cytochrome c span of the mitochondrial respiratory chain. At concentrations below 1000 mol per mol of cytochrome c1, DCCD is able to block the proton-translocating activity associated to succinate or ubiquinol oxidation without inhibiting the steady-state redox activity of the b-c1 complex either in intact mitochondrial particles or in the isolated ubiquinol-cytochrome c reductase reconstituted in phospholipid vesicles. In parallel to this, DCCD modifies the redox responses of the endogenous cytochrome b, which becomes more rapidly reduced by succinate, and more slowly oxidized when previously reduced by substrates. At similar concentrations the inhibitor apparently stimulates the redox activity of the succinate-ubiquinone reductase. Moreover, DCCD, at concentrations about one order of magnitude higher than those blocking proton translocation, produces inactivation of the redox function of the b-c1 complex. The binding of [14C]DCCD to the isolated b-c1 complex has shown that under conditions leading to the inhibition of the proton-translocating activity of the enzyme, a subunit of about 9500 Da, namely Band VIII, is the most heavily labelled polypeptide of the complex. The possible correlations between the various effects of DCCD and its modification of the b-c1 complex are discussed.

Intracellular degradation of mitochondrial enzymes.

Quantitation of the pool of short-lived mitochondrial proteins in cultured cells by a new method shows it to be very low, i.e. approximately 1.35%. Degradation of three long-lived mitochondrial enzymes of rat liver which make up approximately 25-30% of the mitochondrial protein necessitates the cooperation of mitochondrial and lysosomal components. The degradation of carbamyl phosphate synthetase (t1/2, 7.7 d) and of ATPase (t1/2, 2-3 d) requires both a protein component from the inner mitochondrial membrane and lysosomes while degradation of glutamate dehydrogenase (GDH) (t1/2, approximately 1 d) necessitates a mitoplast factor, identified as NADP, which facilitates the inactivation by lysosomes. Chemotropic modification (carbamylation) of GDH also changes stability to rat liver proteases. All three enzymes are synthesized as pro-enzymes. Their processing and possibly control of degradation by maturases as well as the relation of both processes to molecular plasticity is presented.