Experimental study and clinical use of poly(vinyl acetate) emulsion as liquid embolisation material

A new material, an emulsion of poly(vinyl acetate) was experimentally developed and clinically used to overcome several disadvantages in currently used liquid embolisation materials. The emulsion microparticles, 0.3-0.7 microns in size, possessed cationic charge on the surface and hence aggregated immediately on contact with fluids containing anions. This inert polymer has the advantage that it does not induce a deleterious reaction in living tissue. Moreover, its medium is water and it is not adhesive, like the cyanoacrylates. Several concentrations of emulsion were injected into the renal arteries of dogs. For the investigation of tissue reactions and the possibility of recanalisation, the emulsion was injected into rats both subcutaneously and into the renal arteries. The renal artery injections in dogs showed adequate radiopacity and consistent complete occlusion. The lower the concentration of the emulsion, the smaller the arteries which could be occluded. Even at very low concentrations, however, venous occlusion did not occur. Histological study of the embolised rat kidney revealed no detectable damage in the vessel wall and no recanalisation for up to 6 months. The subcutaneously injected PVAc emulsion elicited mononuclear cell infiltration and gradual centripetal fibrosis, without any deleterious effect on the surrounding tissue. A cerebral arteriovenous malformation (AVM) was embolised using the material. Histology of the resected nidus showed findings similar to those in the animal experiments.

Central nervous system metastases from Ewing's sarcoma--case report

A 12-year-old boy presented with a rare case of intracranial metastasis 33 months after surgical treatment for Ewing's sarcoma of the rib. His chief complaints were headache, right hemiparesis, and disturbance of speech. Computed tomography revealed a large metastatic lesion in the left occipitoparietal region. The tumor was totally removed through an emergency operation. Seven months later the intracranial tumor recurred. Another operation was performed, but he showed spinal cord involvement at the T-10 level and died. The possibility of central nervous system metastasis should be considered in long-term follow-up survivors with Ewing's sarcoma.

Trochlear nerve neurinoma associated with a giant thrombosed dissecting aneurysm of the contralateral vertebral artery

The authors encountered the unusual case of a 57-year-old man with a right trochlear nerve neurinoma associated with a giant thrombosed dissecting aneurysm of the left vertebral artery. The right trochlear nerve neurinoma was subtotally removed via the right subtemporal transtentorial route. The trochlear nerve entered the tumor directly posterolaterally. The left vertebral artery was clipped just proximal to the thrombosed dissecting aneurysm via the left lateral suboccipital approach. The patient was discharged without neurologic deficits except for the right trochlear nerve palsy. To our knowledge, this seems to be the first reported case of such an occurrence.

Extent and location of cerebral infarcts on multiplanar MR images: correlation with distribution of perforating arteries on cerebral angiograms and on cadaveric microangiograms

The basal gray matter in the cerebrum is supplied by different anatomical groups of perforating arteries, including striate, thalamic, and choroidal arteries. In this pictorial essay we illustrate multiplanar MR imaging of infarctions in those regions and correlate their appearances with cerebral angiographic findings of the same patients when available. We also correlate the extent and location of infarctions on multiplanar MR images with the anatomical distributions of perforating arteries seen on microangiograms of unrelated cadavers. Information conveyed from this correlation will increase understanding of patterns of basal cerebral infarction shown on cross-sectional imaging.

Apigenin induces morphological differentiation and G2-M arrest in rat neuronal cells

Flavonoids are pigments of edible plants. We have recently reported that most flavonoids induce G1 arrest in human cancer cells, and that genistein (an isoflavone) specifically inhibits their cell cycle at G2-M phase. In the present study, apigenin (a flavone) was found to inhibit the proliferation of B104 rat neuronal cells, and flow-cytometric analysis showed that apigenin arrested their cell cycle at G2-M phase. This effect was dose-dependent and reversible when apigenin was removed from the culture medium. Microscopic observation showed that apigenin did not significantly increase the mitotic index compared with the control. Further, apigenin induced morphological differentiation, that is, elongation and arborization of neurites in B104 cells. This is the first report to show that apigenin inhibited the proliferation of malignant tumor cells by G2-M arrest and induced morphological differentiation.

Clarification of substrate specificity of papain by crystal analyses of complexes with covalent-type inhibitors

In order to investigate the stereo specificity of papain Sn subsites (n = 1-4) at the atomic level, two kinds of covalent-type inhibitors were designed based on the previous results on papain-E-64 and papain-E-64-c interactions, and their complex crystals with papain were analyzed by X-ray diffraction. The results show that the hydrophobic regions consisting of Val-133, Val-157 and Asp-158 and of Tyr-61, Gly-66 and Tyr-67 residues interact with the hydrophobic P2 and P3 side chains of inhibitors, thus indicating the function of the former and latter binding pockets as S2 and S3 subsites, respectively. Furthermore, the X-ray analysis suggests that the papain has no definite Sn subsite of n > or = 4, and the S3-P3 hydrophobic interaction is significantly affected by the Pn side chain (n > or = 4) of both the substrate and the inhibitor.

Expression of major histocompatibility complex class II but not of CD8 molecules by lectin-stimulated peripheral CD4+ T cells in LEC mutant rats

LEC rats show a congenital maturational arrest from CD4+8+ to CD4+8- but not to CD4-8+ cells in the thymus. However, some CD4+ cells exist in peripheral lymph nodes. In normal F344 rats, a part of CD4+ T cells expressed CD8 molecules upon concanavaline A (Con A) stimulation. The percentage of CD4+8+ cells and the level of CD8 expression in F344 rat CD4+ cells were enhanced by the glucocorticoid hormone dexamethasone. In contrast, although LEC rat CD4+ cells induced DNA synthesis normally upon Con A stimulation, expression of CD8 was significantly reduced. Furthermore, addition of dexamethasone did not restore the inhibition of CD8 expression. However, LEC rat CD4+ cells could induce CD8 expression, when stimulated by T cell receptor (TCR) cross-linking with anti-TCR monoclonal antibody, suggesting that the TCR-mediated signal is normally transduced in LEC rat CD4+ cells. On the other hand, LEC rat CD4+ cells showed normal expression of major histocompatibility complex (MHC) class II antigens, when stimulated by either Con A or TCR cross-linking, indicating that signals for the induction of MHC class II expression are normal in LEC rat CD4+ cells. Activation of peripheral CD4+ cells has been reported to induce simultaneous expression of CD8 and MHC class II molecules in rats. However, our results using LEC rat CD4+ cells suggest that Con A-induced signaling pathways for CD8 and MHC class II expression can be separable.

Stimulation of interleukin-6 production by endothelin in rat bone marrow-derived stromal cells

Endothelin (ET) produced by endothelial cells has recently been found to be a potent vasoconstricting hormone. In this report, ET is shown to be a potent stimulator of interleukin-6 (IL-6) production by rat bone marrow (BM)-derived stromal cells. It was also shown that ET increased the level of mRNA for IL-6 in these cells. The two types of ET receptor (R), ETAR and ETBR, were shown to be expressed on both BM-derived stromal cells in culture and ex vivo in BM tissue, suggesting that ET works as a physiologic stimulator of IL-6 production in the BM. It was shown that ETAR is coupled to phospholipase C activation, leading to the production of inositol 1,4,5-trisphosphate (IP3) and 1,2-diacylglycerol (DAG) as second messengers in BM-derived stromal cells. This was corroborated by data showing that IL-6 production in these cells was induced by combined stimulation with ionomycin and phorbol myristate acetate, thereby bypassing the effects of IP3 and DAG, respectively. This is the first report on the hormonal regulation of IL-6 production by BM stromal cells, indicating that hematopoiesis is subject to endocrinologic regulation under physiologic conditions. ET has recently been reported to be produced by macrophages in response to bacterial lipopolysaccharide and human immunodeficiency virus-1 glycoprotein 120. These facts, taken together with our findings, raise the possibility that ET shares the same role of IL-1 as a local cytokine, mediating an intercellular signal between macrophages and BM stromal cells in response to bacterial or viral stimulation.

Inheritance of immunoglobulin subclass regulator-1 (Igsr-1) in LEC mutant rats

Long-Evans Cinnamon (LEC) mutant rats were reported to exhibit a deficiency in the serum immunoglobulin (Ig) G1. The phenotype determining the basal level of IgG1 was tentatively designated as immunoglobulin subclass regulator-1 (Igsr-1), and normal rats and LEC rats were categorized into Igsr-1A (normal expression of IgG1) and Igsr-1B (low expression of IgG1), respectively. In this report we examined genetic trait of this phenotype in LEC rats. The serum IgG1 levels in F1 hybrids produced by mating LEC rats (Igsr-1B) with normal rats (Igsr-1A) were intermediate level, indicating that Igsr-1 behaves as a co-dominant genetic trait. When backcross rats were examined, serum IgG1 levels varied between those in normal and LEC rats without clear segregation, indicating that Igsr-1 is controlled by multiple genes. Furthermore, the serum IgG1 level in each backcross rat did not correlate to another recessive mutant genotype, thid (T-helper immunodeficiency). These data suggest that the deficiency in serum IgG in LEC rats is independent of the deficiency in helper T cell function, but might be due to the multiple deficiency in as-yet-unidentified mechanisms.

Antinociceptive and antipyretic effects of alkaloids extracted from the stem bark of Hunteria zeylanica

Effects of crude alkaloids extracted from the stem bark of Hunteria zeylanica Gard. (H. zeylanica) on nociceptive responses, capillary permeability, yeast-induced hyperthermia, pentobarbital-induced sleep, and spontaneous motor activity were investigated. Oral administration of 50 mg/kg H. zeylanica alkaloid extract significantly decreased the number of writhings induced by intraperitoneal acetic acid. The extract at 100-200 mg/kg significantly increased nociceptive threshold of the inflamed but not the non-inflamed paw in the Randall-Selitto test. Moreover, in the formalin test, the extract (100 mg/kg) significantly decreased licking activity in the late phase without affecting the activity in the early phase. However, the extract did not produce antinociceptive effect in the hot plate test, while it inhibited increase of vascular permeability induced by acetic acid in the capillary permeability test. Moreover, the extract dose-dependently reduced yeast-induced hyperthermia in rats without affecting normothermia. It did not affect pentobarbital-induced sleep, but significantly increased locomotor activity at 100 mg/kg. These results suggest that H. zeylanica alkaloid extract possesses antinociceptive and antipyretic effects, and that the former effect may be mediated by its anti-inflammatory action.

[Antitumor effect of UFT against differentiated thyroid cancer]

We have determined the levels of 5-FU, tegafur and uracil in the thyroid cancer and normal thyroid tissue in the patients with differentiated carcinoma who were administered UFT 600 mg/day p.o. preoperatively for six days. 5-FU and uracil levels in the thyroid cancer tissue were significantly higher than in normal thyroid tissue. However, tegafur level did not show significant differences in any tissues. Two cases with differentiated carcinoma, which resulted in PR after prolonged administration of UFT were presented. These findings suggest that oral administration of UFT for a long term is a useful treatment for advanced differentiated thyroid cancer.

Enhanced expression of catalytic subunit isoform PP1 gamma 1 of protein phosphatase type 1 in malignant fibrous histiocytoma

The expression of the three catalytic subunits of protein phosphatase (PP) type 1 and 2A, PP1 alpha, PP1 gamma 1, and PP2AC, was examined in malignant fibrous histiocytoma using immunohistochemical analysis. The percentage of cells stained positively with antiserum against PP1 catalytic subunit isoform PP1 gamma 1 was significantly higher in tumorous region than in non-tumorous region of malignant fibrous histiocytoma. Furthermore, tumorous region showed markedly high S-phase fraction in the cell cycle, as compared to non-tumorous region. These results suggest that PP1 gamma 1 is involved in the accelerated growth of tumor cells in malignant fibrous histiocytoma.

Wilson's disease gene is homologous to hts causing abnormal copper transport in Long-Evans cinnamon rats

BACKGROUND/AIMS

The Long-Evans Cinnamon (LEC) mutant rat shows an excess copper accumulation in the liver and low serum ceruloplasmin activity. The disorder is controlled by a single autosomal recessive gene designated as hts. Wilson's disease is an autosomal recessive disorder of copper metabolism characterized by abnormal copper accumulation in the liver and low serum ceruloplasmin activity. The gene responsible for Wilson's disease has recently been isolated. The present study was designed to examine whether the LEC rat is an ideal animal model for Wilson's disease from a genetic point of view.

METHODS

For chromosomal mapping of hts, genetic linkage analysis using rat microsatellite marker loci was performed. Furthermore, cosegregation between hts and a rat counterpart of the Wilson's disease gene was analyzed.

RESULTS

hts was finely mapped to rat chromosome 16. Complete cosegregation between hts and a rat counterpart of the Wilson's disease gene was detected.

CONCLUSIONS

hts is likely to correspond to a rat homologue of the Wilson's disease gene. The present results allow us to propose that the LEC rat is an ideal animal model for Wilson's disease.

Acute effects of interstitial hyperthermia on normal monkey brain--magnetic resonance imaging appearance and effects on blood-brain barrier

The magnitude and time course of histological and neuroradiological changes due to interstitial hyperthermia in normal cerebral white matter were investigated in eight adult Japanese monkeys. A cooling system enveloping a 2450-MHz microwave antenna was inserted stereotactically into the brain under general anesthesia. A point located 5 mm away from the surface of the cooling system was used as the reference point (RP). Hyperthermia was given to maintain the RP at 43 degrees C for 60 minutes. Two animals were sacrificed under general anesthesia following the intravenous administration of Evans blue, immediately and 1, 3, and 7 days after treatment. After removing the brain, histological changes were investigated. Magnetic resonance (MR) imaging was performed at 1, 3, and 7 days after treatment. Evans blue extravasation was most prominent in the region heated to 43 degrees C or above immediately after treatment. MR imaging showed obvious enhancement in the region heated to 43 degrees C or above 1 day after treatment, related to the disruption of the blood-brain barrier (BBB) by hyperthermia. Three days after treatment, ring-like enhancement with a central low-intensity area was seen in the region heated to about 43 degrees C, caused by BBB disruption and slight neovascularization. One week after treatment, an enhanced ring was observed in the region heated to less then 43 degrees C which surrounded a low-intensity area. The enhancement seen 1 week after treatment was caused by prominent neovascularization. T2-weighted imaging showed a high-intensity area, caused by edema, most prominent 3 days after treatment. Thus chemotherapeutic agents should be given just before the end of hyperthermia.

DNA replication from initiation zones of mammalian cells in a model system

We reported that DNA replication initiates from the region containing an autonomously replicating sequence from Saccharomyces cerevisiae when negatively supercoiled plasmid DNA is incubated with the proteins required for simian virus 40 DNA replication (Y. Ishimi and K. Matsumoto, Proc. Natl. Acad. Sci. USA 90:5399-5403, 1993). In this study, the DNAs containing initiation zones from mammalian cells were replicated in this model system. When negatively supercoiled DNA containing an initiation zone (2 kb) upstream of the human c-myc gene was incubated with simian virus 40 T antigen as a DNA helicase, HSSB (also called replication protein A), and DNA polymerase alpha-primase complex isolated from HeLa cells, DNA replication was specifically initiated from the center of the initiation zone, which was elongated bidirectionally in the presence of a DNA swivelase. Without HSSB, the level of DNA synthesis was significantly reduced and the localized initiation could not be detected, indicating that HSSB plays an essential role in the initiation of DNA replication. The digestion of negatively supercoiled template DNA with a single-strand-specific nuclease revealed that HSSB stimulated DNA unwinding in the center of the initiation zone where the DNA duplex is relatively unstable. In contrast, DNA replication started from a broad region of an initiation zone downstream of the dihydrofolate reductase gene from chinese hamster ovary cells, but the center of the region was mapped near the origin of bidirectional DNA replication. These results suggested that this system mimics a fundamental process of initiation of eukaryotic DNA replication. The mechanism of initiation is discussed.

Onset of paternal gene activation in early mouse embryos fertilized with transgenic mouse sperm

We investigated the onset of paternal gene expression in the early mouse embryo. We obtained transgenic mouse embryos by fertilizing BD (C57BL/6N x DBA) F1 hybrid female oocytes in vitro, with sperm from homozygous transgenic males carrying integrated chicken beta-actin promoter-driven firefly luciferase cDNA. We then examined the RNA and protein synthesis of the luciferase gene in embryos from the 1- to 2-cell stage. RNA transcripts of the luciferase gene were first detected in the 1-cell stage embryos as early as 13 hr postinsemination, just prior to elongation. By photon-count imaging, functional luciferase was identified at the 2-cell stage 23 hr postinsemination. These findings indicate that the paternal endogenous gene is already transcribed in the late 1-cell embryos, although paternally derived protein is not synthesized until the 2-cell stage. Therefore, these results suggest that the embryonic gene is activated as early as the late 1-cell stage.

Malignant pleural mesothelioma presenting as achalasia

A 65-year-old man with an occupational history of asbestos exposure developed dysphagia and vomiting. Clinical examinations at onset revealed a dilated esophagus with smooth narrowing at the gastroesophageal junction and no apparent tumor in and around the esophagus. Achalasia was suspected. Dysphagia progressed gradually and examinations performed three months after the onset disclosed a tumor in the pleural and the peritoneal cavities. At laparotomy, the tumor extended from the pleural cavity into the peritoneal cavity. Histological examination of the biopsied specimen demonstrated malignant mesothelioma. We report the first case of malignant pleural mesothelioma presenting as achalasia.

Expression of fimbriae and host response in Branhamella catarrhalis respiratory infections

Sputum during the acute exacerbation of chronic respiratory diseases were observed under the electron microscope, to determine the in vivo expression of surface structures of Branhamella catarrhalis (B. catarrhalis), the polymorphonuclear neutrophil (PMN) response to B. catarrhalis infections, and the composition of sputum. It was found that during infection fimbriae are expressed in B. catarrhalis. However, there were sparsely to densely fimbriated bacteria in each sputum sample. The length of the fimbriae were from 50 to 76 nm. In the sparsely fimbriated B. catarrhalis, external to the cell wall, a thin, granular, electron-dense layer was observed. Due to the presence of fimbriae, this layer was not seen in densely fimbriated B. catarrhalis. Blebs were also found in B. catarrhalis. PMNs were found to phagocytose both B. catarrhalis and debris. Evidence was found that debris were formed mainly by the destruction of PMNs. Bacteria as well as debris were phagocytosed by PMNs.

[A case of sarcoidosis with middle lobe atelectasis]

We report a case of sarcoidosis complicated by middle lobe atelectasis. A chest radiograph and a chest CT film on admission revealed middle lobe atelectasis and mediastinal lymphadenopathy. Bronchofiberscopic findings showed slit-like stenosis and reddish, edematous mucosal change of the middle lobe orifice. On admission, the serum angiotensin-converting enzyme (ACE) level was within the normal range. However, the ACE level had increased beyond the normal range by 2 months later, histological examination of a specimen from a transbronchial lung biopsy (TBLB) of the middle lobe revealed noncaseating epithelioid cell granulomas. We diagnosed sarcoidosis because of the histological findings from the TBLB and serum ACE elevation. Treatment with predonisolone resulted in remarkable alleviation of middle lobe atelectasis and mediastinal lymphadenopathy. Cases of sarcoidosis with middle lobe atelectasis are rare in Japan.

[Percutaneous transluminal angioplasty (PTA) for stenosis at the subclavian artery and at the origin of the vertebral artery: therapeutic indication and some adjunctive safe methods during PTA]

Percutaneous transluminal angioplasty (PTA) for brachiocephalic occlusive lesions has progressed. In this paper our experiences and results of PTA in dealing with those lesions are described with emphasis on adjunctive procedures during PTA. Recently, twenty-four patients with stenosis of the subclavian artery (SA) and/or stenosis at the origin of the vertebral artery (VA) were included in this study. Among the 24, there were 16 cases with SA stenosis, 6 cases with stenosis at the origin of VA and 3 cases with both SA and stenosis at the origin of VA. The stenosis was due to atherosclerosis in 21 cases and aortitis in 3 cases. Most of the patients presented ischemic symptoms of vertebrobasilar circulation and affected upper extremities. In PTA of brachiocephalic lesions, one of the most formidable complications is an embolism distal to the central nervous system. To prevent this complication, a vascular endoscope was used for visualization of the luminal surface of the stenotic lesions in 7 cases, and a protective balloon was used in 4 recent cases. The protective balloon was used for transient occlusion of the artery to alter the flow direction so that the possible emboli might be forced to flow away to a less critical distal artery. In the distal protective balloon technique, the protective balloon was set so as to occlude the stenotic artery distally. Debris caused by PTA was aspirated and/or washed out to an extracranial artery with heparinized saline. In the proximal protective balloon technique, the protective balloon was set so as to occlude the stenotic artery proximally. Debris was washed out with blood flow caused by the induced steal phenomenon to an extracranial artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of calcium hydroxide-containing root canal sealers with an improved rabbit ear chamber

An improved rabbit ear chamber was used to evaluate calcium hydroxide-containing root canal sealers on their potential to induce dystrophic calcification in connective tissue. Four sealers and two control materials were introduced into the chambers and the effects of these materials on the living vascular tissue were observed continuously under a biomicroscope up to 9 weeks. Conventional histopathological investigation and examinations with a scanning electron microscope and an X-ray microanalyzer were done to supplement the results. Sealapex and Calvital (Ca(OH)2 + iodoform) revealed almost the same tissue reaction as calcium hydroxide-saline paste; they rapidly made a precipitate-barrier of calcium phosphate in the connective tissue, inducing calcification. However, Dentalis KEZ (ZnO-Ca(OH)2 + eugenol) caused mild disorders of microcirculation without calcification, as well as Canals (ZnO + eugenol). New A (Ca(OH)2 + fatty acid) had good compatibility with microvessels as well as New B (ZnO + fatty acid), however they induced no calcification and disintegrated rapidly in the tissue. These sealers were reclassified according to what they actually bring about in the tissue, not according to what they include.

Role of interleukin-8 (IL-8) and an inhibitory effect of erythromycin on IL-8 release in the airways of patients with chronic airway diseases

To evaluate of the role of interleukin-8 (IL-8), a chemotactic cytokine, in the continuous neutrophil accumulation in the airways of patients with chronic airway disease (CAD) and persistent Pseudomonas aeruginosa infection, we investigated the cell population, IL-8 levels, IL-1 beta levels, tumor necrosis factor (TNF) activities, and neutrophil elastase (NE) activities of bronchoalveolar lavage (BAL) fluids in 17 CAD patients (with P. aeruginosa infections [CAD+PA], n = 9; without any bacterial infections [CAD-PA], n = 8) and 8 normal volunteers. We found significant elevations of neutrophil numbers, IL-8/albumin ratios, and NE/albumin ratios in BAL fluids from CAD patients, in the following rank order: CAD+PA > CAD-PA > normal volunteers. IL-1 beta/albumin ratios were elevated only in CAD+PA, while no TNF bioactivity was detected in BAL fluids. The neutrophil numbers correlated significantly with the IL-8/albumin ratios and NE/albumin ratios in the BAL fluids of CAD patients. When anti-human IL-8 immunoglobulin G was used for neutralizing neutrophil chemotactic factor (NCF) activities in BAL fluids, the mean reduction rate of NCF activities in CAD+PA patients was significantly higher than that in CAD-PA patients. We also evaluated the effects of low-dose, long-term erythromycin therapy in BAL fluids from three CAD+PA and two CAD-PA patients. Treatment with erythromycin caused significant reductions of neutrophil numbers, IL-8/albumin ratios, and NE/albumin ratios in BAL fluids from these patients. To elucidate the mechanism of erythromycin therapy, we also examined whether erythromycin suppressed IL-8 production by human alveolar macrophages and neutrophils in vitro. We demonstrated a moderate inhibitory effect of erythromycin on IL-8 production in Pseudomonas-stimulated neutrophils but not in alveolar macrophages. Our data support the view that persistent P. aeruginosa infection enhances IL-8 production and IL-8-derived NCF activity, causing neutrophil accumulation in the airways and the progressive lung injuries observed in patients with CAD. The clinical efficacy of erythromycin therapy for CAD patients might be partly mediated through a reduced IL-8 production, diminishing neutrophil accumulation and NE release in the airways.

[MR imaging findings of nonketotic hyperglycinemia. 2 cases of neonatal onset]

We presented MR (magnetic resonance) images findings of the brain in nonketotic hyperglycinemia (NKH) from 2 patients of neonatal onset. MR findings in our cases of NKH are compatible with the pathological alterations described in the literature; MR images revealed delayed myelination of the cerebral white matter and hypoplasia of the corps callosum. The latter finding particularly seemed to be relatively characteristic to NKH. MR examination is the imaging modality of choice for this disease because it can demonstrate the degree of myelination, and development of the corpus callosum particularly on sagittal section.

Synergistic activation by Ras and 14-3-3 protein of a mitogen-activated protein kinase kinase kinase named Ras-dependent extracellular signal-regulated kinase kinase stimulator

We have identified, in Xenopus oocyte cytosol, a protein kinase named REKS (Ras-dependent extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase kinase (MEK) stimulator), which phosphorylates and activates recombinant ERK2 through recombinant MEK in a recombinant GTP gamma S (guanosine 5'-(3-O-thio)triphosphate)-Ras-dependent manner. We show here that this REKS activity is synergistically enhanced by a combination of mammalian recombinant GTP gamma S-KiRas and 14-3-3 protein purified from rat brain. 14-3-3 protein is known to activate tyrosine and tryptophan hydroxylases, to modulate the protein kinase C activity, to stimulate secretion, and to show phospholipase A2 activity per se. 14-3-3 protein did not affect the MEK activity. 14-3-3 protein neither interacted with Ki-Ras nor affected the neurofibromin activity to stimulate the GTPase activity of Ki-Ras under the conditions where the recombinant N-terminal fragment of c-Raf-1 inhibited it. These results suggest that 14-3-3 protein has an additional function in the regulation of the Ras-MEK-ERK cascade pathway through the activation of REKS.