A role for phosphoinositide 3-kinase in the completion of macropinocytosis and phagocytosis by macrophages

Phosphoinositide 3-kinase (PI 3-kinase) has been implicated in growth factor signal transduction and vesicular membrane traffic. It is thought to mediate the earliest steps leading from ligation of cell surface receptors to increased cell surface ruffling. We show here that inhibitors of PI 3-kinase inhibit endocytosis in macrophages, not by interfering with the initiation of the process but rather by preventing its completion. Consistent with earlier studies, the inhibitors wortmannin and LY294002 inhibited fluid-phase pinocytosis and Fc receptor-mediated phagocytosis, but they had little effect on the receptor-mediated endocytosis of diI-labeled, acetylated, low density lipoprotein. Large solute probes of endocytosis reported greater inhibition by wortmannin than smaller probes did, indicating that macropinocytosis was affected more than micropinocytosis. Since macropinocytosis and phagocytosis are actin-mediated processes, we expected that their inhibition by wortmannin resulted from deficient signaling from macrophage colony-stimulating factor (M-CSF) receptors or Fc receptors to the actin cytoskeleton. However, video microscopy showed cell surface ruffling in wortmannin-treated cells, and increased ruffling after addition of M-CSF or phorbol myristate acetate. Quantitative measurements of video data reported slightly diminished ruffling in wortmannin-treated cells. Remarkably, the ruffles that formed in wortmannin-treated macrophages all receded into the cytoplasm without closing into macropinosomes. Similarly, wortmannin and LY294002 did not inhibit the extension of actin-rich pseudopodia along IgG-opsonized sheep erythrocytes, but instead prevented them from closing into phagosomes. These findings indicate that PI 3-kinase is not necessary for receptor-mediated stimulation of pseudopod extension, but rather functions in the closure of macropinosomes and phagosomes into intracellular organelles.

beta 2-Microglobulin modified with advanced glycation end products is a major component of hemodialysis-associated amyloidosis

beta 2-Microglobulin (beta 2M) is a major constituent of amyloid fibrils in hemodialysis-associated amyloidosis, a complication of long-term hemodialysis patients. Amyloid fibril proteins were isolated from connective tissues forming carpal tunnels in hemodialysis patients with carpal tunnel syndrome. Two-dimensional polyacrylamide gel electrophoresis and Western blotting demonstrated that most of the beta 2M forming amyloid fibrils exhibited a more acidic pI value than normal beta 2M. This acidic beta 2M was also found in a small fraction of beta 2M in sera and urine from these patients, whereas heterogeneity was not observed in healthy individuals. We purified acidic and normal beta 2M from the urine of long-term hemodialysis patients and compared their physicochemical and immunochemical properties. Acidic beta 2M, but not normal beta 2M, was brown in color and fluoresced, both of which are characteristics of advanced glycation end products (AGEs) of the Maillard reaction. Immunochemical studies showed that acidic beta 2M reacted with anti-AGE antibody and also with an antibody against an Amadori product, an early product of the Maillard reaction, but normal beta 2M did not react with either antibody. Incubating normal beta 2M with glucose in vitro resulted in a shift to a more acidic pI, generation of fluorescence, and immunoreactivity to the anti-AGE antibody. The beta 2M forming amyloid fibrils also reacted with anti-AGE antibody. These data provided evidence that AGE-modified beta 2M is a dominant constituent of the amyloid deposits in hemodialysis-associated amyloidosis.

Proteolytic release of CD44 intracellular domain and its role in the CD44 signaling pathway

CD44 is a widely distributed cell surface adhesion molecule and is implicated in diverse biological processes. However, the nature of intracellular signaling triggered by CD44 remains to be elucidated. Here, we show that CD44 undergoes sequential proteolytic cleavage in the ectodomain and intracellular domain, resulting in the release of a CD44 intracellular domain (ICD) fragment. Consequently, CD44ICD acts as a signal transduction molecule, where it translocates to the nucleus and activates transcription mediated through the 12-O-tetradecanoylphorbol 13-acetate-responsive element, which is found in numerous genes involved in diverse cellular processes. Expression of an uncleavable CD44 mutant as well as metalloprotease inhibitor treatment blocks CD44-mediated transcriptional activation. In search of the underlying mechanism, we have found that CD44ICD potentiates transactivation mediated by the transcriptional coactivator CBP/p300. Furthermore, we show that cells expressing CD44ICD produce high levels of CD44 messenger RNA, suggesting that the CD44 gene is one of the potential targets for transcriptional activation by CD44ICD. These observations establish a novel CD44 signaling pathway and shed new light on the functional link between proteolytic processing of an adhesion molecule at the cell surface and transcriptional activation in the nucleus.

Molecular Characterization of N-Acylethanolamine-hydrolyzing Acid Amidase, a Novel Member of the Choloylglycine Hydrolase Family with Structural and Functional Similarity to Acid Ceramidase

Bioactive N-acylethanolamines, including anandamide (an endocannabinoid) and N-palmitoylethanolamine (an anti-inflammatory and neuroprotective substance), are hydrolyzed to fatty acids and ethanolamine by fatty acid amide hydrolase. Moreover, we found another amidohydrolase catalyzing the same reaction only at acidic pH, and we purified it from rat lung (Ueda, N., Yamanaka, K., and Yamamoto, S. (2001) J. Biol. Chem. 276, 35552-35557). Here we report complementary DNA cloning and functional expression of the enzyme termed "N-acylethanolamine-hydrolyzing acid amidase (NAAA)" from human, rat, and mouse. The deduced primary structures revealed that NAAA had no homology to fatty acid amide hydrolase but belonged to the choloylglycine hydrolase family. Human NAAA was essentially identical to a gene product that had been noted to resemble acid ceramidase but lacked ceramide hydrolyzing activity. The recombinant human NAAA overexpressed in HEK293 cells hydrolyzed various N-acylethanolamines with N-palmitoylethanolamine as the most reactive substrate. Most interestingly, a very low ceramide hydrolyzing activity was also detected with NAAA, and N-lauroylethanolamine hydrolyzing activity was observed with acid ceramidase. By the use of tunicamycin and endoglycosidase, NAAA was found to be a glycoprotein. Furthermore, the enzyme was proteolytically processed to a shorter form at pH 4.5 but not at pH 7.4. Expression analysis of a green fluorescent protein-NAAA fusion protein showed a lysosome-like distribution in HEK293 cells. The organ distribution of the messenger RNA in rats revealed its wide distribution with the highest expression in lung. These results demonstrated that NAAA is a novel N-acylethanolamine-hydrolyzing enzyme that shows structural and functional similarity to acid ceramidase.

A contractile activity that closes phagosomes in macrophages

Studies of Fc-mediated phagocytosis by mouse macrophages identified a contractile activity at the distal margins of forming phagosomes. Time-lapse video microscopic analysis of macrophages containing rhodamine-labeled actin and fluorescein dextran showed that actin was concentrated at the distal margins of closing phagosomes. Phagocytosis-related contractile activities were observed when one IgG-opsonized erythrocyte was engaged by two macrophages. Both cells extended pseudopodia until they met midway around the erythrocyte. It was then constricted and pulled into two phagosomes, which remained interconnected by a string of erythrocyte membrane. Butanedione monoxime, an uncompetitive inhibitor of class II and perhaps other myosins, and wortmannin and LY294002, inhibitors of phosphoinositide 3-kinase, prevented the constrictions without inhibiting the initial pseudopod extension. Immunofluorescence microscopy showed the presence of myosins IC, II, V and IXb in phagosomes. Of these, only myosin IC was concentrated around the strings connecting shared erythrocytes, suggesting that myosin IC mediates the purse-string-like contraction that closes phagosomes. The sequential processes of pseudopod extension and contraction can explain how macropinosomes and spacious phagosomes form without guidance from a particle surface.

Macrophage scavenger receptor mediates the endocytic uptake and degradation of advanced glycation end products of the Maillard reaction

Modification of proteins by long-term incubation with glucose leads to the formation of advanced glycation end products (AGE). Recent immunological demonstration of the presence of AGE proteins in several human tissues suggests that they may be involved in aging, diabetic complications and atherosclerosis. AGE proteins are taken up by macrophages via the AGE receptor, which is similar to the macrophage scavenger receptor (MSR). In the present study, we examined whether MSR could mediate the endocytic uptake of AGE proteins by using Chinese hamster ovary (CHO) cells overexpressing bovine type II MSR (CHO-SRII). 125I-labelled AGE bovine serum albumin (125I-AGE-BSA) as well as 125I-acetylated low-density lipoprotein (125I-acetyl-LDL) underwent endocytic degradation by CHO-SRII cells, but not by control CHO cells. Endocytic degradation of 125I-acetyl-LDL and 125I-AGE-BSA by CHO-SRII cells was significantly inhibited by unlabeled AGE-BSA, as well as by acetyl-LDL. Immunoelectron microscopic studies using both AGE-BSA conjugated with gold particles and anti-(bovine MSR) antibody (D2) revealed co-localization of gold particles and the reactive sites for the antibody at coated pits of plasma membranes as well as in endosomes. These results clearly show that MSR mediates the endocytic uptake and degradation of AGE proteins, suggesting a new role of MSR in biological recognition of AGE in vivo.

Calcium hydroxyapatite ceramic used as a delivery system for antibiotics

Porous blocks of calcium hydroxyapatite ceramic were evaluated as delivery systems for the sustained release of antibiotics. We tested gentamicin sulphate, cefoperazone sodium, and flomoxef sodium in powder form placed in a cylindrical cavity in calcium hydroxyapatite blocks, using in vitro studies of elution and in vivo studies in rats. Gentamicin sulphate gave a maximum concentration within the first week, which gradually decreased but was still effective at 12 weeks, when 70% of the antibiotic had been released. Even at this stage the antibiotic concentration from a 75 mg dose was five times the minimum inhibitory concentration for staphylococci. In the in vivo studies the release of gentamicin sulphate into the normal bone of rats was at similar rates and levels. The bacteriocidal activity of the drugs was not affected by packing into calcium hydroxyapatite ceramic and the blocks were completely biocompatible on histology. This new system overcomes the disadvantages of other drug delivery systems, avoiding thermal damage to the antibiotics and a second operation for the removal of the carrier. Some mechanical strength is provided by the ceramic and healing may be accelerated by bone ingrowth into its micropores.

Phosphoinositide-3-kinase-independent contractile activities associated with Fcgamma-receptor-mediated phagocytosis and macropinocytosis in macrophages

Previous studies have shown that Fcgamma receptor (FcR)-mediated phagocytosis and macropinocytosis in macrophages consist of two dissociable activities: a phosphoinositide 3-kinase (PI3K)-independent extension of phagocytic cups and a PI3K-dependent contractile mechanism that closes phagosomes and ruffles into intracellular organelles. Here, we identify an additional contractile activity that persists in the presence of the PI3K inhibitor wortmannin. ML-7, an inhibitor of myosin-light-chain kinase (MLCK), inhibited FcR-mediated phagocytosis, macropinocytosis and cell movements associated with ruffling. Scanning electron microscopy demonstrated a striking difference in morphology between phagocytic cups in the different inhibitors: whereas phagocytic cups of control cells and wortmannin-treated cells conformed closely to particles and appeared to have constricted them, the phagocytic cups in cells treated with ML-7 were more open. Video microscopy of macrophages expressing green-fluorescent-protein (GFP)-actin fusions revealed that bound IgG-opsonized erythrocytes were squeezed during phagosome formation and closure. In ML-7, GFP-actin-rich protrusions extended outward but failed to squeeze particles. Moreover, in contrast to the effects of PI3K inhibitors, ML-7 markedly reduced ruffle movement, and perturbed circular ruffle formation. These PI3K-independent myosin-II-based contractile activities that squeeze phagocytic cups and curve ruffles therefore represent a third component activity of the actin cytoskeleton during phagocytosis and macropinocytosis.

The effectiveness of an immobilization device in conformal radiotherapy for lung tumor: reduction of respiratory tumor movement and evaluation of the daily setup accuracy

PURPOSE

To evaluate the daily setup accuracy and the reduction of respiratory tumor movement using a body frame in conformal therapy for solitary lung tumor.

METHODS AND MATERIALS

Eighteen patients with a solitary lung tumor underwent conformal therapy using a body frame. The body shell of the frame was shaped to the patient's body contour. The respiratory tumor movement was estimated using fluoroscopy, and if it was greater than 5 mm, pressure was applied to the patient's abdomen with the goal of minimizing tumor movement. CT images were then obtained, and a treatment planning was made. A total dose of 40 or 48 Gy was delivered in 4 fractions. Portal films were obtained at each treatment, and the field displacements between them and the simulation films were measured for daily setup errors. The patients were repositioned if the setup error was greater than 3 mm. Correlations were analyzed between patient characteristics and the tumor movement, or the tumor movement reduction and the daily setup errors.

RESULTS

Respiratory tumor movement ranged from 0 to 20 mm (mean 7.7 mm). The abdominal press reduced the tumor movement significantly from a range of 8 to 20 mm to a range of 2 to 11 mm (p = 0.0002). Daily setup errors were within 5 mm in 90%, 100%, and 93% of all verifications in left-right, anterior-posterior, and cranio-caudal directions, respectively. Patient repositioning was performed in 25% of all treatments. No significant correlation was detected between patient characteristics and tumor movement, tumor movement reduction, and the daily setup errors.

CONCLUSIONS

The abdominal press was successful in reducing the respiratory tumor movement. Daily setup accuracy using the body frame was acceptable. Verification should be performed at each treatment in hypofractionated conformal therapy.

Advanced glycation end products are eliminated by scavenger-receptor-mediated endocytosis in hepatic sinusoidal Kupffer and endothelial cells

Long-term incubation of proteins with glucose leads to the formation of advanced glycation end products (AGE). Physiological aspects of the catabolism of non-enzymically glycated proteins were studied in vivo and in vitro. AGE-modified BSA (AGE-BSA) was a mixture of high-Mr (cross-linked), monomeric and low-Mr (fragmented) AGE-BSA. After intravenous administration in rat, all three fractions of AGE-BSA accumulated extremely rapidly and almost exclusively in liver. Uptake in liver endothelial, Kupffer and parenchymal cells accounted for approx. 60%, 25% and 10-15% respectively of hepatic elimination. Both cross-linked and monomeric AGE-BSA were efficiently taken up and degraded in cultures of purified liver endothelial and Kupffer cells. Endocytosis of AGE-BSA by these cells was inhibited by several ligands for the scavenger receptor. Although 125I-Hb was not endocytosed in vitro, 125I-AGE-Hb was effectively endocytosed by a mechanism that was subject to inhibition by AGE-BSA. Endocytosis of N-terminal propeptide of type I procollagen, a physiological ligand for the scavenger receptor, was effectively inhibited by AGE-Hb and AGE-BSA. We conclude that AGE-modification renders macromolecules susceptible for elimination via the scavenger receptor of both liver endothelial and Kupffer cells.

The use of calcium hydroxyapatite ceramic in bone tumour surgery

We report 60 benign bone tumours treated by resection and curettage followed by the implantation of calcium hydroxyapatite ceramic (CHA). After follow-up of six to 60 months (average 36), no patient had local recurrence of the tumour or any adverse effects from the implants. In almost all cases radiography showed that the CHA was well-incorporated into the host bone, with new bone formation in and around the CHA. Corrective remodelling of deformed bone and normal fracture healing suggested that there was normal bone turnover in the presence of the CHA. Histology of biopsies from seven patients showed bone ingrowth into the pore structure of CHA in the central zone of some defects by one year after implantation. CHA appears to be a useful substitute for bone graft in the treatment of some benign tumours.

Sequential signaling in plasma-membrane domains during macropinosome formation in macrophages

Macropinosomes are large endocytic vesicles that form in ruffling regions of plasma membrane. To analyze signal organization relative to ruffle closure into circular ruffles and cup closure into macropinosomes, this study used quantitative microscopy to measure 3' phosphoinositides and small-GTPase activities in a representative subset of forming macropinosomes. Macropinocytosis was stimulated by the addition of macrophage colony-stimulating factor (M-CSF) to macrophages expressing fluorescent reporter proteins. Ratiometric and fluorescence resonance energy transfer (FRET) microscopy determined that Rac1 activity and phosphatidylinositol (3,4,5)-trisphosphate [PtdIns(3,4,5)P(3)] levels increased transiently, peaking 26-30 seconds after ruffle closure. Three-dimensional reconstruction of cells labeled with the fluorescent dye FM4-64 showed that PtdIns(3,4,5)P(3) was restricted to open, circular cups in the plasma membrane. Quantitative fluorescence microscopic methods determined the timing of cup closure, which followed 40-100 seconds after Rac1 and PtdIns(3,4,5)P(3) deactivation and coincided with accumulation of phosphatidylinositol 3-phosphate and Rab5a. Thus, ruffle closure creates a circular domain of plasma membrane that localizes the activation and deactivation of Rac1 and phosphoinositide 3-kinase (PI3K), followed by recruitment of Rab5a and the contractile activities of cup closure.

Rapid formation of advanced glycation end products by intermediate metabolites of glycolytic pathway and polyol pathway

To clarify roles of intermediate metabolites of the glycolytic pathway and the polyol pathway in nonenzymatic glycation under physiological conditions, we incubated bovine serum albumin with intermediates of both pathways in the micromolar range as well as with 20 mmol/l glucose, and observed the formation of advanced glycation end products (AGEs). We found that triose phosphates, glyceraldehyde, and a novel polyol pathway-related metabolite, fructose 3-phosphate along with its breakdown product, 3-deoxyglucosone were extremely potent glycating agents that at nearly physiological concentrations on incubation with albumin produced substantial amounts of AGEs as early as 24 hours, while 20 mmol/l glucose afforded trace amounts of AGEs after two week incubation. The results along with the previous evidence of the increased level of intermediates in diabetic states may suggest that the intermediate metabolites rather than glucose contribute to enhanced glycation in diabetic tissues, inspite of the much lower concentrations compared with glucose.

Slow release of anticancer drugs from porous calcium hydroxyapatite ceramic

We have developed a new delivery system for sustained release of an anticancer drug (cis-platinum) by enclosure into blocks of porous calcium hydroxyapatite ceramic. The slow release of this drug from this system was confirmed in in vitro experiments. When this system was implanted into normal back muscle, or the tibia, sustained release of cis-platinum was observed during a 12-week period after implantation. The diffusion rate of cis-platinum into blood and other organs (liver, kidney, brain) was less than 10% of that at the implanted site. This delivery system placed into experimental tumors of mice also showed a uniform release of anticancer drug for more than 3 months. Inhibition of tumor growth was more marked after local implantation of this system than after intraperitoneal administration of cis-platinum. These results indicate that this new approach to a drug delivery system may well have an important role in cancer chemotherapy. In bone tumors it is attractive because the mechanical strength of calcium hydroxyapatite ceramic permits partial surgical excision and replacement of the bone defect at the same time.

Calcium influx triggers the sequential proteolysis of extracellular and cytoplasmic domains of E-cadherin, leading to loss of beta-catenin from cell-cell contacts

Cadherins are major cell-cell adhesion molecules in both tumor and normal tissues. Although serum levels of soluble E-cadherin have been shown to be higher in the cancer patients than in healthy volunteers, the detail mechanism regulating release of soluble E-cadherin remains to be elucidated. Here we show that the ectodomain of E-cadherin is proteolytically cleaved from some cancer cells by a membrane-bound metalloprotease to yield soluble form, and the residual membrane-tethered cleavage product is subsequently degraded by intracellular proteolytic pathway. Futhermore, we show that extracellular calcium influx, that is induced by mechanical scraping of cells or ionomycin treatment, enhances the metalloprotease-mediated E-cadherin cleavage and the subsequent degradation of the cytoplasmic domain. Immunocytochemical analysis demonstrates that the sequential proteolysis of E-cadherin triggered by the calcium influx results in translocation of beta-catenin from the cell-cell contacts to cytoplasm. Our data suggest that calcium influx-induced proteolysis of E-cadherin not only disrupts the cell-cell adhesion but also activates beta-catenin-mediated intracellular signaling pathway, potentially leading to alterations in motility and proliferation activity of cells.

Small GTPases and phosphoinositides in the regulatory mechanisms of macropinosome formation and maturation

Macropinosome formation requires the sequential activation of numerous signaling pathways that coordinate the actin-driven formation of plasma membrane protrusions (ruffles) and circular ruffles (macropinocytic cups), followed by the closure of these macropinocytic cups into macropinosomes. In the process of macropinosome formation, localized productions of phosphoinositides such as PI(4,5)P₂ and PI(3,4,5)P₃ spatiotemporally orchestrate actin polymerization and rearrangement through recruiting and activating a variety of actin-associated proteins. In addition, the sequential activation of small GTPases, which are known to be master regulators of the actin cytoskeleton, plays a pivotal role in parallel with phosphoinositides. To complete macropinosome formation, phosphoinositide breakdown and Rho GTPase deactivation must occur in appropriate timings. After the nascent macropinosomes are formed, phosphoinositides and several Rab GTPases control macropinosome maturation by regulating vesicle trafficking and membrane fusion. In this review, we summarize recent advances in our understanding of the critical functions of phosphoinositide metabolism and small GTPases in association with their downstream effectors in macropinocytosis.

Ultrastructure of nonenzymatically glycated mesangial matrix in diabetic nephropathy

Advanced protein glycation has been proposed as a major factor in the development of diabetic nephropathy. Advanced glycation end products (AGEs) have altered the structure of extracellular matrix component and impaired self association in vitro. To elucidate the role of AGEs in the progression of diabetic nephropathy, the present study was undertaken to localize glomerular AGEs immunohistochemically. Ultrastructural changes of the mesangial matrix were analyzed with high resolution scanning electron microscopy. No glomerular AGEs staining was noted in normal control kidney specimens, or in tissue from glomerulonephritis patients without diabetes mellitus. The mesangium showed a positive AGEs staining in advanced stages of diabetic nephropathy, and the most characteristic finding was the strong AGEs staining in nodular lesions. By high resolution scanning electron microscopy, control and diabetic mesangial matrices revealed a meshwork structure composed of fine fibrils (10 nm in width) and numerous pores (12 to 13 nm in diameter). In the nodular lesions, however, loosening of the meshwork was significant, and the diameter of the pores was enlarged (approximately 24 nm). This study provides the first immunohistochemical evidence that AGEs are localized in diabetic glomeruli, most notably to nodular lesions. Advanced glycation might play a role in the progression of diabetic nephropathy through impairment of the assembly of matrix proteins in vivo.

Phosphoinositide metabolism during membrane ruffling and macropinosome formation in EGF-stimulated A431 cells

Inhibitors of phosphoinositide 3-kinase (PI3K) were found to perturb macropinosome formation without affecting the membrane ruffling and actin polymerization in epidermal growth factor-stimulated A431 cells. Live-cell imaging and quantitative image analysis of the fluorescence intensity ratio of the YFP-tagged phospholipase Cdelta1-pleckstrin homology domain (YFP-PLC-PH) relative to membrane-targeted CFP (CFP-Mem) demonstrated that the concentration of PI(4,5)P(2) in the membrane ruffles forming macropinocytic cups increased to more than double that in planar plasma membranes. The PI(4,5)P(2) level in the membrane reached its maximum just before macropinosome closure and rapidly fell as the macropinocytic cups closed. In contrast, the PI(3,4,5)P(3) concentrations visualized based on the YFP-Akt-PH or YFP-Bruton's tyrosine kinase (Btk)-PH/CFP-Mem ratio increased locally at the site of macropinosome formation and peaked at the time of macropinosome closure. The kinetics of PI(4,5)P(2) and PI(3,4,5)P(3) appeared to be mechanistically linked to actin remodeling during macropinocytosis. From the pharmacological data using inhibitors and synthetic phosphoinositides and other data, it could be concluded that both PI(4,5)P(2) elimination and PI(3,4,5)P(3) production by PI3K might be crucial for macropinosome formation from membrane ruffles. This study emphasizes that locally controlled levels of phosphoinositides are important for regulating the function of actin-binding proteins which effect changes in the membrane architecture.

Combined therapy with MK-801 and nimodipine for protection of ischemic brain damage

Calcium ion can enter ischemic neurons through both receptor-operated and voltage-sensitive Ca2+ channels. To attenuate this Ca2+ entry and Ca2(+)-induced neuronal injury, we tried a combined treatment with the noncompetitive N-methyl-D-aspartate (NMDA) antagonist, MK-801, and the dihydropyridine calcium antagonist, nimodipine, in a cat middle cerebral artery occlusion (1 hour) and reperfusion (3 hours) model. We measured changes in cytosolic free calcium, nicotinamide adenine dinucleotide/reduced nicotinamide adenine dinucleotide redox state, and blood flow in the cat cortex using a newly developed fluorometric technique with indo-1, a fluorescent intracellular Ca2+ indicator. The combined treatment, starting 5 minutes into ischemia, was effective in reducing both Ca2+ entry and histologic damage and in enhancing recovery of the electroencephalogram following reperfusion. MK-801 alone was also effective, but to a lesser extent. These data suggest that the dual blockade of Ca2+ entry using MK-801 and nimodipine may be a useful tool for protection against ischemic brain damage.

Noradrenergic nervous activity in migraine

The autonomic nervous function in patients with migraine was studied during headache-free intervals. The following observations were made: (1) a decrease in overshoot in Valsalva's maneuver; (2) orthostatic hypotension; (3) low levels of plasma norepinephrine in the steady state; (4) failure in elevation of the plasma norepinephrine level after head-up tilting; (5) dilatation of the pupils after instillation in the eye of 1.25% epinephrine; and (6) a long recovery time in tests by bolus injection of 0.1 microgram of norepinephrine bitartrate per kilogram. The above findings suggest that patients with migraine show sympathetic hypofunction together with denervation hypersensitivity of the iris and the arteries, and that a defective noradrenergic nervous system may play a role in the pathogenesis of migraine.

A novel in vivo assay system for consecutive measurement of brain nitric oxide production combined with the microdialysis technique

A novel spectrophotometric nitrite (NO2-)/nitrate (NO3-) assay system for a small quantity (5 microliter) of dialysate sample obtained by in vivo brain microdialysis was developed based on the diazotization reaction. The system has the advantage of in vivo consecutive measurement, high precision, good reproducibility, technical simplicity, relatively short resolution time (2.5-20 min), and wide availability. The NO3- level in the rat striatum was found to be 3 times higher than the NO2- level. A nitric oxide (NO) synthase inhibitor, NG-nitro-L-arginine methyl ester, reduced striatal NO2-/citrulline formation in a dose-related manner and increased arginine, indicating that the tissue NO2- level detected by this assay system adequately reflects the striatal NO synthase activity.

The involvement of calpain-dependent proteolysis of the tumor suppressor NF2 (merlin) in schwannomas and meningiomas

Neurofibromatosis type 2 (NF2) protein, also known as merlin or schwannomin, is a tumor suppressor, and NF2 is mutated in most schwannomas and meningiomas. Although these tumors are dependent on NF2, some lack detectable NF2 mutations, which indicates that alternative mechanisms exist for inactivating merlin. Here, we demonstrate cleavage of merlin by the ubiquitous protease calpain and considerable activation of the calpain system resulting in the loss of merlin expression in these tumors. Increased proteolysis of merlin by calpain in some schwannomas and meningiomas exemplifies tumorigenesis linked to the calpain-mediated proteolytic pathway.