Nitric oxide does not promote iron release from ferritin

It has been previously reported that iron release from ferritin could be promoted by nitric oxide (NO) generated from sodium nitroprusside. It was thus proposed that some of the toxic effects of NO could be related to its ability to increase intracellular free iron concentrations and generate an oxidative stress. On the contrary, the iron exchange experiments reported here show that NO from S-nitrosothiols is unable to promote iron release from ferritin. The discrepancy may be explained by the disregarded ability of ferrozine, the ferrous trap used in the previous report, to mobilize iron both from ferritin and from sodium nitroprusside spontaneously.     

Isolation and preliminary characterization of gas1-1, a mutation causing partial suppression of the phenotype conferred by the gibberellin-insensitive (gai) mutation in Arabidopsis thaliana (L.) Heyhn

The semi-dominant gai mutation of arabidopsis confers a dark-green dwarf phenotype resembling that of gibberellin (GA)-deficient mutants. In contrast to GA-deficient mutants, gai mutants do not respond to GA treatments and accumulate higher levels of bioactive GAs than are found in wild-type controls. The gai mutation thus alters the responses of plant cells to GA, indicating that the GAI (wild-type) gene product is involved in GA reception and/or signal transduction. Here we describe the isolation and preliminary characterization of a mutation, gas1-1, which is not linked to gai and which partially suppresses the effect of the gai mutation. Double mutant, gai gas1-1, homozygotes are less severely dwarfed and lighter green than gai GAS1 controls. However, comparisons of the effects of treatments with exogenous GA demonstrate that gas1-1 does not increase the GA responsiveness of the gai mutant. Thus the gas1-1 mutation appears to reduce the GA-dependency of plant growth, and identifies a gene (GAS1) whose product is a candidate GA signal-transduction component.Abbreviations GA gibberellin - GA₃ gibberellic acid We thank Maarten Koornneef (Wageningen Agricultural University, The Netherlands) for providing mutant seed stocks; Mark Aarts and Bernard Mulligan (University of Nottingham, UK) for performing the -irradiation. This work was made possible by AFRC/BBSRC PMB Grants PG208/520 and PG208/0600, and by a grant from the Gatsby Charitable Foundation. P.C. was supported by a Human Capital and Mobility Fellowship from the EC.     

Astroglial Cells Express Large Amounts of GABAA Receptor Proteins in Mature Brain

Abstract: GABA_A receptors were characterized in cellular fractions isolated from adult bovine brain. The fraction enriched in cortical astrocytes is very rich in high-affinity binding sites for [³H]flunitrazepam and other "central-type" benzodiazepine ligands. The amount of specific [³H]flunitrazepam binding was more than five times higher in the glial fraction than in synaptosomal and perikaryal fractions. [³H]Flunitrazepam was displaced by low concentrations of clonazepam and other specific ligands for central GABA_A receptors. Specific binding sites for GABA, flunitrazepam, barbiturates, and picrotoxin-like convulsants were characterized. Allosteric interactions between the different sites were typical of central-type GABA_A receptors. The presence of α-subunit(s), as revealed by [³H]flunitrazepam photoaffinity labeling, was demonstrated in all brain fractions at molecular mass 51–53 kDa. Photoaffinity labeling was highest in the glial fraction. However, in primary cultured astrocytes from neonate rat cortex, no photoaffinity labeling was detected. Information obtained from astrocytes in culture should thus be taken with caution when extrapolated to differentiated astroglial cells. Our results actually show that, in mature brain, most of the fully pharmacologically active GABA_A receptors are extrasynaptic and expressed in astroglia.     

Mutations in the mitochondrial split gene COXI are preferentially located in exons: a mapping study of 170 mutants

We have analysed the precise location of a large number (170) of mutations affecting the structural gene for subunit 1 of the cytochrome c oxidase complex. This gene, COXI, is 12.9 kb long and the major part of the sequence (i.e. 11.3 kb) is composed of introns. Several conclusions can be drawn from this study: (1) A significant proportion (84/170) of the mutations cannot be assigned to a single position within the gene by deletion mapping, in spite of clearly being located in it. These mutations are probably large deletions or multiple mutations. (2) Four mutants carry distant double mutations, which have been individually localized. (3) Eighty-two mutants have lesions that are restricted to very short regions of the gene and we therefore conclude that they are most probably due to single hits; amongst these single mutations, 41 are unambiguously located in exons and 28 in introns. This result implies that, at least in this particular split gene, the probability of selection of a mutant phenotype in an exon is, on the average, 13.3 times greater than in an intron, in spite of the existence, within most of these introns, of open reading frames specifying intronic proteins. The evolutionary significance and biological implications of these results are discussed.     

Matric potential evaluations and measurements for gelled substrates

A new method for evaluating the matric potential of gelled media has been developed. The method allows the derivation of the matric potential as a limit of a series of measurements of water potential values from gelled media prepared without added components, from agar powders progressively cleaned of mineral impurities. Three commercial agar brands were tested, and for these the matric potential was found to contribute only between 1 and 2% of their total water potential. Thermodynamic features relating matric and osmotic potentials are described. New hypotheses for understanding the water flux mechanism from gel to tissue cultured explants are discussed. Movement of water along polymeric chains is postulated to be a facilitated step in comparison with bulk movement.     

Three rare and little known cryptogonimid digeneans from the sciaenid fish Sciaena umbra (L.) in the western Mediterranean

Three species of cryptogonimid digeneans are redescribed from the gut of Sciaena umbra off Corsica. The systematics of the three species, Metadena pauli (Vlassenko, 1931), Paracryptogonimus aloysiae (Stossich, 1885) n. comb. and Anoiktostoma coronatum (Wagener, 1852), are discussed. The latter two species, which have not been reported for more than 100 years, have previously been confused and synonymised with each other. P. aloysiae, which is transferred to Paracryptogonimus from Anoiktostoma, is restricted to the rectum, whereas A. coronatum prefers the pyloric caeca and anterior intestine.     

Study of human erythrocyte membrane protein interactions by selective solubilization of Triton-skeletons

Summary— The membrane skeleton, responsible for shape and mechanical properties of the red cell, was purified by the Triton extraction procedure in presence of 5 mM, 150 mM or 600 mM NaCl. The proportion of spectrin, protein 4.1 and actin present in erythrocyte skeletons does not depend on the molarity of NaCl used. In contrast ankyrin, protein band 3 and protein 4.2 are removed from skeletons as the ionic strength increased. Solubilization assays of membrane skeletons were used to study protein interactions inside the skeleton. Solubilization was performed by Tris, a non-selective disruptive reagent, or by p-mercuribenzene sulfonic acid (PMBS), which principally release spectrin and actin. Tris action was assessed by calculation of the percentage of solubilized proteins, which increased proportionally with Tris molarity. PMBS action was kinetically determined as the decrease in skeleton turbidity. With these two reagents, we observed a lower dissociation of skeletons prepared with high ionic strength buffer. Erythrocyte pretreatment with okadaic acid, an inhibitor of serine-threonine phosphatases, revealed a phosphorylation-induced skeleton gelation and a better resistance to Tris-solubilization.     

Transformation of chicory and expression of the bacterial uidA and nptll genes in the transgenic regenerants

Transgenic chicory plants were obtained from different explantsco-cultured with Agrobacterium tumefaciens. Among tap-root,leaf and cotyledonary tissues, etiolated cotyledons showed thegreatest competence for transformation. The Agrobacterium strainsused contained either pGSGLUC1 or pTDE4 as a vector which carryboth the neomycin phosphotransferase II gene (nptll) for kanamycinresistance and ß-glucuronidase gene (uidA) under thecontrol of different promoters. Transformation was confirmedby NPTII enzymatic assay, histochemical analysis of GUS activityand DNA hybridization. Transgenic plants expressed both markergenes in root and shoot tissues. In leaves, GUS activity wasexpressed in all tissue types, whatever the nature of the promoter.Nevertheless, variable heterogeneous patterns of expressionwere observed in the different root tissues. Differential expression of the GUS fusions controlled by thedual TR or the CaMV 35S promoters are discussed. Key words: Chicory, genetic transformation, GUS activity, kanamycin resistance