[Use and validity of the 14-3-3 protein test in the diagnosis of prion diseases: a 4-year prospective study]. / Utilización y validez de la prueba de la proteína 14-3-3 en el diagnóstico de enfermedades por priones: estudio prospectivo de 4 años.

BACKGROUND AND OBJECTIVES: The 14-3-3 test shows a high efficiency for the diagnosis of Creutzfeldt-Jakob disease (CJD), as long as an appropriate clinical setting exists. We analyze the evolution of the use and the validity of this test in Spain. PATIENTS AND METHOD: From January 1997 to June 2001, 1,092 samples were tested in our laboratory; 674 samples were selected for the study. Diagnoses were obtained by the referring physicians and the national CJD surveillance system according to standard criteria (results of the test were not included). RESULTS: The number of samples analyzed (% of follow-up) was: 75 (96%) in 1997, 138 (82.3%) in 1998, 197 (73%) in 1999 and 264 (59%) in 2000. The negative predictive value, sensitivity and specificity for a diagnosis of prion disease revealed stable values (95, 86 and 86%, respectively). The positive predictive value (PPV) decreased from 77% in 1997 to 51% in 2000 because of an increase of false-positive (FP) results. Up to 25% of FP might have been excluded through neuroimaging or CSF characteristics. CONCLUSIONS: The observed increase of the demand suggests that the test is used as a screening technique. In this setting, the PPV of the test decreases due to an increase of false-positive results.

Platelet-activating factor acetylhydrolase activity in cerebrospinal fluid of children with acute systemic or neurological illness.

Platelet-activating factor acetylhydrolase was analyzed in cerebrospinal fluid samples taken from children with a variety of neurological conditions (85 patients; mean age, 3.8 years) to determine it is involved in the defense mechanism against the toxic effect of inflammatory mediators in the central nervous system. A significant increase in cerebrospinal fluid activity was seen in the patients with meningitis and acute febrile illness in comparison with the control subjects. The activity was also significantly higher in the patients with meningitis than in the patients with inflammatory neurological diseases. In addition, the biochemical profile of cerebrospinal fluid platelet-activating factor acetylhydrolase was different from other known acetylhydrolases. These findings suggest that cerebrospinal fluid platelet-activating factor acetylhydrolase activity may be a sensitive marker of the host response to central nervous system infections.

Platelet-activating factor (PAF) concentration and PAF acetylhydrolase activity in cerebrospinal fluid of patients with subarachnoid hemorrhage.

The authors studied the sequential changes in platelet-activating factor (PAF) and PAF acetylhydrolase in the cerebrospinal fluid (CSF) of patients with subarachnoid hemorrhage (SAH). Levels of PAF in CSF showed a gradual increase after the onset of SAH, with a subsequent decrease. The PAF concentration between 5 and 9 days after SAH was greater in patients with cerebral infarction due to vasospasm than in patients without infarction. Conversely, PAF acetylhydrolase activity decreased gradually after SAH, then increased. The enzyme activity for the same period was smaller in patients with cerebral infarction than in patients without infarction. The distribution of the days of maximum PAF concentration and minimum PAF acetylhydrolase activity did not differ significantly between the two groups. The CSF as a source of PAF acetylhydrolase activity gave an apparent Michaelis constant value of 90.8 microM and a maximum velocity of 0.2 nmol/min/mg. The optimum pH level for the PAF acetylhydrolase activity obtained from CSF was 6.5. The enzyme activity of CSF increased, depending on the incubation temperature, ranging from 25 degrees to 45 degrees C. Ethylene-glycol tetra-acetic acid (1 mM) was found to inhibit PAF acetylhydrolase activity in CSF obtained from patients with SAH. Unaltered PAF acetylhydrolase activity was inhibited by adding an aliquot of CSF and minimum PAF acetylhydrolase activity decreased following SAH. Two peaks of inhibitory activity were detected on Sephacryl S-200 HR gel filtration: one was eluted in void volume and the other with an apparent molecular mass of 13 kD. The inhibitory activity was very labile and was lost completely within 3 days of incubation at 4 degrees C. The regulation of the PAF concentration in the CSF of SAH patients is discussed.

Increased serum phospholipase A2 activity in Malawian children with falciparum malaria.

Some clinical manifestations of severe malaria resemble those of sepsis and there may be mediators of the host response that are common to both sepsis and malaria. Phospholipase A2 (PLA2), a proinflammatory enzyme whose expression is induced by tumor necrosis factor (TNF), has been implicated in the pathogenesis of complications of the sepsis syndrome. We examined levels of circulating PLA2 in Plasmodium falciparum malaria and studied the association of PLA2 with disease severity. Plasma PLA2 and TNF were measured in 75 Malawian children with P. falciparum malaria. The mean (SD) plasma PLA2 activity in children with acute malaria was 53,804 (37,256) units/ml as compared with 424 (349) units/ml in 34 healthy controls (P < 0.00001). The mean PLA2 activity in 45 convalescent patients was 2,546 (7,372) units/ml (P < 0.00001). In 48 patients with pretreatment PLA2 activity less than 60,000 units/ml, mortality was 8.3%, while in 27 patients with pretreatment PLA2 levels greater than 60,000 units/ml, mortality was 33.3% (P = 0.008). There were significant correlations between PLA2 and TNF (r = 0.471, P < 0.01), density of parasitemia (r = 0.443, P < 0.0001) and a decrease in hematocrit (r = 0.352, P < 0.005). These data show that P. falciparum malaria is associated with a markedly increased circulating PLA2, especially in patients with severe disease, as manifested by high parasite burden, anemia, coma, and death.

Distribution of vipera ammodytes toxic phospholipase A in the cat and its ability to cross the blood-brain barrier.

Several phospholipases A could be isolated from the venom of the European viper, Vipera ammodytes, having different specific activities toward egg lecithin and different lethalities. The most lethal of these enzymes is fraction "k2" having an intravenous LD50 for white mice of 0.021 mg per kg and a specific activity of 280 microM/min mg at 40 degrees C. The enzyme could be labeled with 131I without loosing its enzymatic activity and lethality. The passage of this enzyme from blood into cerebrospinal fluid (CSF) was followed in anesthetized cats. Approximately 1% of the blood level of the enzyme was found in CSF indicating the ability of this protein to penetrate the blood-brain barrier. Although the lethality of fraction "k2" becomes as low as 0.085 microgram/kg when applied intraventricularly, it is not very likely that the central effects of this fraction are of major importance in envenomation since the distribution pattern of the labeled enzyme shows that most of the protein remains in liver, lungs and kidneys, presumably non-selectively bound to membranes and only 0.2% of the injected fraction can reach the brain. Relatively high amount of enzyme was also found in the diaphragm. The penetration of the blood-brain barrier of the radiolabeled phospholipase is within the limits for the proteins of this size (M.w. 14500).