Cytokine-induced nitric oxide generation by cultured astrocytoma cells involves Ca(++)-calmodulin-independent NO-synthase

The effect of several cytokines (IL1 beta and TNF alpha) on the inducible biosynthesis and release of NO by cultured astrocytoma cells was investigated and compared to that observed following pretreatment of cells with LPS. Preincubation for 4, 12, 24 and 48 h of astrocytoma cells with IL1 beta (10 ng ml-1), TNF alpha (500 U ml-1) and LPS (0.5 micrograms ml-1) enhanced their ability to inhibit thrombin-induced platelet aggregation through the release of an NO-like factor and increased nitrite levels in supernatants of stirred cells. The enhancement of NO production induced by cytokines as well as LPS was mediated by a time-dependent increase of NO-synthase activity in cell homogenates being mainly Ca(++)-calmodulin-independent. However, LPS activated earlier than cytokines the inducible NO-synthase and its effect was, at least in part, related to the release of IL1 beta by astrocytoma cells. In conclusion, the present data show, for the first time, that astrocytoma cells possess a cytokine-inducible Ca(++)-calmodulin-independent NO-synthase, whose activation seems to occur with a mechanism different from that described for LPS.

Calcium ion independent membrane leakage induced by phospholipase-like myotoxins

The two snake venom myotoxins ammodytin L and myotoxin II, purified respectively from Vipera ammodytes ammodytes and Bothrops asper, have phospholipase-like structures but lack an Asp-49 in the active site and are without normal phospholipase activity. The interaction of these proteins with different types of liposomes indicated that the myotoxins were able to provoke rapid and extensive release of the aqueous content of liposomes. Leakage was measured by two different methods: fluorescence dequenching of liposome-entrapped carboxyfluorescein and ESR measurement of intravesicular TEM-POcholine reduction by external ascorbate. The process was independent of Ca2+ and took place without any detectable phospholipid hydrolysis. Nonmyotoxic phospholipases tested under the same conditions were unable to induce liposome leakage, which could be detected only when Ca2+ was added to the medium and with the concomitant hydrolysis of phospholipids. The kinetics of Ca(2+)-dependent and Ca(2+)-independent leakage were completely different, indicating two different mechanisms of interaction with the lipid bilayer. Studies using diphenylhexatriene as a probe of lipid membrane organization indicated that the myotoxins gave rise to a profound perturbation of the arrangement of the lipid chains in the membrane interior, whereas interaction of Naja naja phospholipase A2 with the membrane surface did not affect lipid organization. On the basis of these results we suggest that a new type of cytolytic reaction mechanism is responsible for the effects of phospholipase-like myotoxins in vivo.

Analysis for transaminases in serum with an amperometric glutamate electrode

We determined transaminases in human blood serum with an amperometric glutamate biosensor. The probe was a hydrogen peroxide sensor assembled with appropriate selective membranes to enhance the probe specificity and lifetime. Calibration curves of glutamate were linear in the range 1-1000 mumol/L, with a response time of < 1 min. This probe was subsequently applied to the measurement of activities of aspartate and alanine aminotransferases in human sera. Analytical recovery studies demonstrated the suitability of the glutamate sensor by measuring 91-99% of added glutamate, 92-106% of added aspartate aminotransferase, and 101-105% of added alanine aminotransferase. Transaminase activity measured in 80 sera correlated well with results obtained with a spectrophotometric procedure.

Analysis for Transaminases in Serum with an Amperometric Glutamate Electrode

We determined transaminases in human blood serum with an amperometric glutamate biosensor. The probe was a hydrogen peroxide sensor assembled with appropriate selective membranes to enhance the probe specificity and lifetime. Calibration curves of glutamate were linear in the range 1-1000 mumol/L, with a response time of &lt; 1 min. This probe was subsequently applied to the measurement of activities of aspartate and alanine aminotransferases in human sera. Analytical recovery studies demonstrated the suitability of the glutamate sensor by measuring 91-99% of added glutamate, 92-106% of added aspartate aminotransferase, and 101-105% of added alanine aminotransferase. Transaminase activity measured in 80 sera correlated well with results obtained with a spectrophotometric procedure.

Monoclonal antibodies against human placental glutathione transferase (class pi)

Five monoclonal antibodies (MAbs) were produced in a mouse hybridoma system against human placental glutathione transferase (GST pi). Four of these monoclonal antibodies, named 461 to 464, were of immunoglobulin G class, whereas the monoclonal antibody 465 was of IgA class. All these MAbs specifically recognized the glutathione transferase from human placenta (class pi) showing no cross reactivity against the basic and the neutral forms of GST from human liver. When each MAb was incubated with the GST pi, no inhibition of enzymatic activity towards 1-chloro-2,4-dinitrobenzene was observed except for MAb 465 which showed a slight inhibition to a serial dilution of 1:128.

Two sisters with generalized dystonia associated with homocystinuria

Two sisters with progressive dystonic syndromes and homocystinuria are presented. The biochemical defect was not accompanied by the typical clinical features of homocystinuria. Magnetic resonance imaging (MRI) revealed bilateral lesions of the basal ganglia. Homocystinuria should be considered among the causes of symptomatic or secondary dystonias associated with basal ganglia lesions.

Glutathione transferase of human breast is closely related to transferase of human placenta and erythrocytes

An acidic form (pI 4.6) of glutathione transferase has been purified to homogeneity from normal and tumor specimens of human breast. The two proteins did not differ significantly in their molecular and catalytic properties. The enzyme has a molecular weight of 46,000 and is composed of two identical subunits. The data presented, including amino acid composition, substrate specificity and immunological studies, give strong evidence that the glutathione transferase of human breast, placenta and erythrocytes are similar if not identical proteins.