Tinnitus as the presenting symptom in a case of Lhermitte-Duclos disease.

Dysplastic gangliocytoma or Lhermitte-Duclos disease (LDD) is a hamartomatous malformation of the cerebellar hemisphere that usually presents with signs of increased intracranial pressure or symptoms of cerebellar dysfunction. In this paper, we report a case of LDD presenting with tinnitus, and postulate a probable mechanism for this unusual presentation.

Differential binding of proteins to peroxisomes in rat hepatoma cells: unique association of enzymes involved in isoprenoid metabolism.

Farnesyl diphosphate synthase (FPPS: EC2.5.1.10), a key enzyme in isoprenoid metabolic pathways, catalyzes the synthesis of farnesyl diphosphate (FPP) an intermediate in the biosynthesis of both sterol and non-sterol isoprenoid end products. The localization of FPPS to peroxisomes has been reported (Krisans, S. K., J. Ericsson, P. A. Edwards, and G. A. Keller. 1994. J. Biol. Chem. 269: 14165;-14169). Using indirect immunofluorescence and immunoelectron microscopic techniques we show here that FPPS is localized predominantly in the peroxisomes of rat hepatoma H35 cells. However, the partial release of 60;-70% of cellular FPPS activity is observed by selective permeabilization of these cells with digitonin. Under these conditions, lactate dehydrogenase, a cytosolic enzyme, is completely released whereas catalase, a known peroxisomal enzyme, is fully retained. Digitonin treatment of H35 cells differentially affects the release of other peroxisomal enzymes involved in isoprenoid metabolism. For instance, mevalonate kinase and phosphomevalonate kinase are almost totally released (95% and 91%, respectively), whereas 3-hydroxy-3-methylglutaryl-CoA reductase is fully retained. Indirect immunoflourescence studies indicate that FPPS is localized in peroxisomes of Chinese hamster ovary (CHO)-K1 cells but is dispersed in the cytosol of ZR-82 cells, a mutant that lacks peroxisomes. Unlike in H35 cells, FPPS is completely released upon digitonin permeabilization of CHO-K1 and ZR-82 cells. In contrast, under the same permeabilization conditions, catalase is fully retained in CHO-K1 cells but completely released from ZR-82 cells. These studies indicate that FPPS and other enzymes in the isoprenoid biosynthetic pathways, involved in the formation of FPP, are differentially associated with peroxisomes and may easily diffuse to the cytosol. Based on these observations, the significance and a possible regulatory model in the formation of isoprenoid end-products are discussed.

Involvement of farnesyl protein transferase (FPTase) in FcarepsilonRI-induced activation of RBL-2H3 mast cells.

Changes in farnesyl protein transferase (FPTase) activity and FPTase beta-subunit protein levels were determined in IgE-sensitized RBL-2H3 mast cells in response to polyvalent antigen administration. Ten minutes after the addition of DNP modified BSA to mast cells, whose high affinity receptor for IgE (FcvarepsilonRI) contained bound anti-DNP IgE, FPTase specific activity increased by 54 +/- 28%. Time course studies showed FPTase specific activity doubled during a 20- to 30-min period after antigen-induced cell aggregation. Also, an increase in FPTase beta-subunit protein during this time ( approximately 30%) was observed; this protein increase was not accompanied by a similar increase in FPTase beta-subunit m-RNA levels. The FcvarepsilonRI aggregation had no significant effect on the activities of other enzymes involved with farnesyl diphosphate (FPP) metabolism: FPP synthase, isopentenyl diphosphate isomerase, geranylgeranyl protein transferase, and squalene synthase. Specific inhibition of FPTase activity by manumycin was studied to determine what role FPTase plays in mast cell activation. Manumycin profoundly inhibited hexosaminidase release in activated cells, indicating FPTase is required for signal transduction involved with protein exocytosis from RBL-2H3 mast cells.

Mach one impact test apparatus utilizing an 18.4-mm-bore gas gun with a novel decelerating device.

The design and operation of a helium-gas-driven gun capable of operation to Mach one is described in this report. The gun utilizes a unique tapered-tube decelerator that captures the sabot and prevents gas discharge from the muzzle. This feature makes it possible to operate the gun in a normal laboratory environment without excessive safety precautions.