Fischer-Tropsch synthesis. Evaluation of an aluminum small channel reactor.

Fischer-Tropsch synthesis was conducted in a small channel compact heat exchange reactor that was constructed of aluminum. While limited to lower temperature-pressure regions of the Fischer-Tropsch synthesis, the reactor could be operated in an isothermal mode with nearly a constant temperature along the length of the channel. The results obtained with the compact heat exchange reactor were similar to those obtained in the isothermal continuous stirred tank reactor, with respect to both activity and selectivity. Following a planned or unplanned shutdown, the reactor could be restarted to produce essentially the same catalytic activity and selectivity as before the shutdown.

Involvement of nuclear factor kappaB in c-Myc induction by tubulin polymerization inhibitors.

We showed previously that microtubule disassembly by vinblastine induces the proto-oncogene c-myc in epithelial mammary HBL100 cells. In this study, we demonstrate that vinblastine treatment in these cells, in contrast to what was observed with the colon adenocarcinoma cell line HT29-D4, activated the transcription factor NFkappaB, which has been involved in c-myc regulation. The microtubule disassembly also induced IkappaB degradation. Using transient transfection analysis, we show that the trans-activation of c-myc by vinblastine was decreased when NFkappaB binding sites on c-myc promoter were mutated. Additionally, we demonstrate that microtubule dissolution trans-activated a thymidine kinase-CAT construct containing an NFkappaB binding site at -1180 to -1080 bp relative to the P1 promoter. Thus, vinblastine up-regulates the enhancer activity of the NFkappaB binding site. These results suggest that microtubule disassembly induced by vinblastine can trans-activate the c-myc oncogene through NFkappaB. Taking into consideration the paradoxical roles of both c-myc and NFkappaB in proliferation or apoptosis, this data reveals the complex action mechanism of this microtubule interfering agent.

A major posttranslational modification of ezrin takes place during epithelial differentiation in the early mouse embryo.

The preimplantation development of the mouse embryo leads to the formation of two populations of cells: the trophectoderm, which is a perfect epithelium, and the inner cell mass. The divergence between these two lineages is the result of asymmetric divisions, which can occur after blastomere polarization at compaction. The apical pole of microvilli is the only asymmetric feature maintained during mitosis and polarity is reestablished only in daughter cells that inherit all or a sufficient part of this pole. To analyze the role of ezrin in the formation and stabilization of the pole of microvilli, we isolated and cultured inner cell masses (ICM). These undifferentiated cells can differentiate very quickly into epithelial cells. After isolation of the ICMs, ezrin relocalizes at the cell cortex before the formation of microvilli. This redistribution occurs in the absence of protein synthesis. The formation of microvilli at the apical surface of the outer cells of ICM correlates with a major posttranslational modification of ezrin. We show here that this posttranslational modification is not controlled by a serine/threonine kinase but an O-glycosylation may partially contribute to it. These data suggest that ezrin has at least two roles during development. First, ezrin may be involved in the formation of microvilli because it localizes at the cell cortex before microvilli appear in ICMs. Second, ezrin may stabilize the pole of microvilli because it is modified posttranslationally when microvilli form.

Control of vulval cell division number in the nematode Oscheius/Dolichorhabditis sp. CEW1.

Spatial patterning of vulval precursor cell fates is achieved through a different two-stage induction mechanism in the nematode Oscheius/Dolichorhabditis sp. CEW1 compared with Caenorhabditis elegans. We therefore performed a genetic screen for vulva mutants in Oscheius sp. CEW1. Most mutants display phenotypes unknown in C. elegans. Here we present the largest mutant category, which affects division number of the vulva precursors P(4-8).p without changing their fate. Among these mutations, some reduce the number of divisions of P4.p and P8.p specifically. Two mutants omit the second cell cycle of all vulval lineages. A large subset of mutants undergo additional rounds of vulval divisions. We also found precocious and retarded heterochronic mutants. Whereas the C. elegans vulval lineage mutants can be interpreted as overall (homeotic) changes in precursor cell fates with concomitant cell cycle changes, the mutants described in Oscheius sp. CEW1 do not affect overall precursor fate and thereby dissociate the genetic mechanisms controlling vulval cell cycle and fate. Laser ablation experiments in these mutants reveal that the two first vulval divisions in Oscheius sp. CEW1 appear to be redundantly controlled by a gonad-independent mechanism and by a gonadal signal that operates partially independently of vulval fate induction.

ERM proteins: from cellular architecture to cell signaling.

ERM (ezrin/radixin/moesin) proteins, concentrated in actin rich cell-surface structures, cross-link actin filaments with the plasma membrane. They are involved in the formation of microvilli, cell-cell adhesion, maintenance of cell shape, cell motility and membrane trafficking. Recent analyses reveal that they are not only involved in cytoskeleton organization but also in signaling pathway. They play an important role in the activation of members of the Rho family by recruiting their regulators. The functions of ERM proteins are regulated by their conformational charges: the intramolecular interaction between the N- and C-terminal domains of ERM proteins charges masks several binding sites, leading to a dormant protein. Different activation signals regulate ERM proteins functions by modulating these intramolecular interactions. The involvement of ERM proteins in many signaling pathways has led to study their role during development of different species.

Ribavirin-induced resistance to heat shock, inhibition of the Ras-Raf-1 pathway and arrest in G(1).

Ribavirin [1-(beta-D-ribofuranosyl)1,2,4-triazole-3-carboxamide (virazole)], a specific inhibitor of inositide 5'-monophosphate dehydrogenase (IMPDH), induces a strong depletion of GTP pools in IGR39 cells. After a 3-day treatment, the cell cycle was reversibly arrested in G(0)/G(1), suggesting the involvement of GTP in the cell cycle process. The reduction of the GTP cell content modified the appearance of the microtubule network, as examined using immunofluorescence. However, the dynamics of repolymerisation were not altered. When arrested in G(0)/G(1), cells displayed a surprising resistance to a 3-h period of heat shock at 45 degrees C. Considering the lack of coimmunoprecipitation of p21ras with Raf-1, the reduction of the level of GTP-associated p21ras and the decrease of the activation of the extracellular signal-regulated protein kinases (ERK), also known as mitogen-activated protein (MAP) kinase, in ribavirin-treated cells, we suggest a possible relationship between the expression of heat-shock proteins and the change, in GTP-depleted cells, of the regulation of Raf kinase by ras protein.

Further studies in deoxycorticosterone acetate treated rats: brain content of mineralocorticoid and glucocorticoid receptors and effect of steroid antagonists on salt intake.

We have studied the role of mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) on salt appetite developed by deoxycorticosterone acetate (DOCA) treated rats. To this end, we measured the effects of DOCA given on alternate days on (1) salt intake; (2) MR and GR in hippocampus (HIPPO), amygdala (AMYG), and hypothalamus (HT); (3) the activity of ornithine decarboxylase (ODC), a GR-mediated response, and (4) the salt intake after treatment with the antiglucocorticoid RU 486 or the antimineralocorticoid ZK 91587. First, we demonstrated that 10 but not 1 mg DOCA induced natriogenesis. Forty-eight hours after adrenalectomy and 24 h after the last DOCA injection, 10 but not 1 mg hormone reduced binding to GR in HIPPO, AMYG, and HT. Both doses of DOCA also reduced the binding to MR in HIPPO, without changes in AMYG; in HT the 1-mg dose was without effect, but the natriogenic dose (10 mg) highly increased binding of [3H]-corticosterone to MR. Scatchard analysis demonstrated increased Bmax and Kd values in the HT of DOCA-treated rats. Occupation of GR by DOCA did not stimulate the ODC activity, in contrast to the four-fold increment effected by the glucocorticoid dexamethasone. Also, administration of RU 486 did not inhibit the sale intake promoted by DOCA, in contrast to ZK 91587 which partly delayed the natriogenic effect of DOCA. It is suggested that brain MR are involved in the natriogenic effect of DOCA, whereas the role of GR is inconclusive.(ABSTRACT TRUNCATED AT 400 WORDS)

Transformation and nuclear translocation of brain type L corticosteroid receptors complexed with the mineralocorticoid antagonist ZK 91587, aldosterone or dexamethasone.

Type I corticosteroid receptors were determined in cytosol from hippocampus (HIPPO) and amygdala (AMYG), using [3H]aldosterone (ALDO), [3H]dexamethasone (DEX) or the mineralocorticoid antagonist [3H]ZK 91587 as ligands. Incubations with the first two compounds also contained the pure glucocorticoid RU 28362 to block type II receptors. Binding of the three ligands was comparable in cytosol from HIPPO and it was slightly higher for [3H]DEX in AMYG. However, after heat-induced receptor transformation, binding to DNA-cellulose was observed for [3H]ALDO-receptor complex obtained from HIPPO or AMYG, whereas it was negligible for [3H]ZK 91587. Receptors charged with [3H]DEX or [3H]ALDO showed similar retention on DNA-cellulose columns in the case of the AMYG, while binding to the polynucleotide was higher for [3H]ALDO in the HIPPO. Finally, only [3H]ALDO was taken up to a significant extent in purified cell nuclei prepared from slices of HIPPO and AMYG previously incubated with the three ligands. It is concluded that binding of a natural agonist steroid may be a prerequisite for type I receptor transformation and translocation from the cytoplasm into the nuclear fraction. DEX binding to type I receptors resembles a partial agonist with antagonist properties, whereas antagonists such as ZK 91587 are bound and retained in cytoplasm, without further translocation.

Effects of deoxycorticosterone treatment on beta-subunit mRNA for (Na + K)ATPase in brain regions determined by in situ hybridization.

1. We have used in situ hybridization techniques to determine the mRNA for (Na + K)ATPase in 20 brain regions from control rats and rats treated with high doses of deoxycorticosterone (DOC). 2. DOC-treated rats developed a salt appetite following the second hormone administration on alternate days and were used after the fourth DOC administration. 3. DOC treatment did not change the number of silver grains/cell deposited in cells from Ca1, CA2, CA3, and CA4 hippocampal subfields, dentate gyrus, cerebral cortex, medial preoptic area (POA), substantia nigra, and periventricular gray matter. 4. Nonsignificant reductions were detected in lateral POA, medial and lateral septum, caudate-putamen, and three amygdaloid nuclei (cortical, basolateral, and central) from DOC-treated rats. 5. Significant reductions were obtained, after DOC administration, in arcuate and ventromedial hypothalamic nuclei and medial and lateral amygdala. 6. The results suggested that regulation of the beta-subunit mRNA of (Na + K)-ATPase may be related to the central actions of mineralocorticoids in the control of salt intake.

Properties and distribution of binding sites for the mineralocorticoid receptor antagonist [3H]ZK 91587 in brain.

We have studied the binding of the synthetic antimineralocorticoid [3H]ZK 91587 to soluble receptors in brain of adrenalectomized rats. It was observed that [3H]ZK 91587 labeled a single receptor class with high affinity (Kd 1.3 nM) and low capacity (51.1 fmol/mg prot.) in cytosol of hippocampus (HIPPO). The ligand was efficiently displaced in vitro from the receptor by aldosterone (IC50 2.0 nM) and corticosterone (2.3), while dexamethasone showed less potency (IC50 5.1 nM) and the pure antiglucocorticoid RU 28362 competed weakly (161 nM). Furthermore, there was a widespread distribution of binding sites all over the brain for this compound, but with CA1 and CA3 regions of HIPPO, some amygdaloid nuclei and lateral septum containing most of the binding sites, as revealed by binding assays employing 16 different microdissected brain regions. Finally, the receptor labeled with [3H]ZK 91587 was readily displaced by administration of aldosterone in vivo in physiological amounts, from 5 whole brain regions examined, but preferentially from preoptic area, amygdala and HIPPO. It is concluded that [3H]ZK 91587 is a useful ligand for further studies on putative mineralocorticoid responsive cells in brain, due to its high affinity, stability and lack of cross reactivity with glucocorticoid receptors. Its brain distribution is similar to that previously obtained using [3H]aldosterone in the presence of RU 28362 to block ligand binding to the glucocorticoid receptor.