Two-dimensional square and hexagonal oxide quasicrystal approximants in SrTiO3 films grown on Pt(111)/Al2O3(0001)

The formation of two-dimensional oxide dodecagonal quasicrystals as well as related complex approximant phases was recently reported in thin films derived from BaTiO₃ or SrTiO₃ perovskites deposited on (111)-oriented Pt single crystals. Here, we use an all-thin-film approach in which the single crystal is replaced by a 10 nm thick Pt(111) buffer layer grown by molecular beam epitaxy on an Al₂O₃(0001) substrate. An ultra-thin film of SrTiO₃ was subsequently deposited by pulsed laser deposition. The film stacking and structure are fully characterized by diffraction and microscopy techniques. We report the discovery of two new complex phases obtained by reduction of this system through high temperature annealing under ultrahigh vacuum conditions. The formation of a new large square approximant with a lattice parameter equal to 44.4 Å is evidenced by low-energy electron diffraction and scanning tunneling microscopy (STM). Additionally, a new 2D hexagonal approximant phase with a lattice parameter of 28 Å has been observed depending on the preparation conditions. Both phases can be described by two different tilings constructed with the same basic square, triangle and rhombus tiles possessing a common edge length of about 6.7 Å. Using the tiling built from high resolution STM images, we propose an atomic model for each approximant which accounts for the experimental observations. Indeed, the STM images simulated using these models are found to be in excellent agreement with the experimental ones, the bright protrusions being attributed to the topmost Sr atoms. In addition our theoretical approach shows that the adhesion of the oxide layer is rather strong (-0.30 eV Å^-2). This is attributed to charge transfer, from the most electropositive elements (Sr and Ti) to the most electronegative ones (Pt and O), and to hybridization with Pt-states. Density of states calculations indicate differences in the electronic structure of the two approximants, suggesting different chemical and physical properties. This all-thin-film approach may be useful to explore the formation of complex two-dimensional oxide phases in other metal-oxide combinations.

Defining and validating a Body Skin Discomfort Index (BSDI)

OBJECTIVE

To understand the drivers of body skin discomfort and to validate a new index to assess its severity. This index should be sensitive enough to capture changes in response to treatment.

METHODS

Previous consumer studies suggested seven potential main dimensions behind skin discomfort. Four of them refer to self-declarations (stinging, itching, warming and tightening), whereas three can be assessed by a dermatologist (skin dryness, redness and desquamation). Intensity and frequency or extent of these items were measured using 0-9 ordinal scales. To generate the data for validation of a new index based on the 7 items, a group of 49 subjects complaining of skin discomfort was followed up for 5 weeks: 1-week without product application to check reproducibility, followed by 4 weeks of treatment to evaluate sensitivity to change. Items not significantly reported at baseline or with changes because of treatment not sufficiently correlated with the overall change measured by the index were discarded. A control group of 49 subjects presenting no discomfort at all was also included to check the capacity of our index to discriminate both groups. The final index (Body Skin Discomfort Index, BSDI) was normalized to facilitate the clinical interpretation of the results.

RESULTS

After discarding warming and skin redness, the BSDI is finally a five-dimension score calculated as follows: (TI + TF + SI + SF + ItI + ItF + DI + DE + DqI + DqE) 9 9/90 where T, S, It, D and Dq refer to tightness, stinging, itching, dryness, desquamation respectively, and I, F or E refers to intensity, frequency or extent. The final BSDI score displayed a good capacity to discriminate people with skin discomfort from people with 'normal skin', a good reproducibility (intraclass coefficient correlation ICC = 0.85) and a good sensitivity to detect change because of treatment (Difference vs. Baseline of 2.63 on a 0-9 scale).

CONCLUSION

The developed index, BSDI, is a reliable way to address the measurement issue of the multidimensional skin discomfort syndrome. It thus should simplify the evaluation of cosmetic products effect and helps to compare products dedicated to body cleansing.

On the cation dependence of interlamellar and interparticular water and swelling in smectite clays

The osmotic character of long-range interlamellar swelling in smectite clays is widely accepted and has been evidenced in the interlayer space by X-ray diffraction. Such a behavior in mesopores was not experimentally confirmed until the determination of the mesopore size distribution in Na-montmorillonite prepared from MX80 bentonite using thermoporometry experiments. This is confirmed here for other montmorillonite samples where the interlayer cations are alkaline and Ca(2+) cations. The nature of the interlayer cation is found as strongly influencing the behavior of the size and the swelling of mesopores. These results are supported by the BJH (Barrett, Joyner and Halenda) pore radius values issued from the nitrogen adsorption-desorption isotherms at the dry state. Thermoporometry results as a function of relative humidity ranging from 11% to 97% have shown an evolution of the mesopore sizes for a purified Na-montmorillonite. New thermoporometry data are presented in this article and confirm that the interparticle spaces in K-, Cs-, or Ca-montmorillonites are not strongly modified for all the range of relative humidity: the swelling is not observed or is strongly limited. It appears in contrast that only Li- and Na-montmorillonites undergo a mesopore swelling, distinct from the interlayer swelling. More generally, our results confirm the possibility to use thermoporometry or differential scanning calorimetry to study the structure and the evolution of swelling materials in wetting conditions such as natural clays or biological cells. In this paper, we describe the different key steps of the hydration of swelling clays such as montmorillonites saturated with alkaline cations. Using thermoporometry results combined with X-ray diffraction data, we distinguish the evolution of the porosity at the two different scales and propose a sequence of hydration dependent on the interlayer cation. From this study, it is shown that the interlayer spaces are not completely filled when the mesopores start to fill up. This implies that the swelling observed in the mesopores for Li and Na samples is due to an osmotic swelling. For the other samples, it is difficult to conclude definitively. Furthermore, we determine the different proportion of water (interlayer water and mesopore water) present in our samples by the original combination of (1) X-ray diffraction data, (2) the pore size distribution obtained by thermoporometry, and (3) recent adsorption isotherm results. It is found that the interlayer space is never completely filled by water at the studied relative humidity values for all samples except for the Cs sample.

Application of microanalytical techniques to the study of aqueous ion sorption phenomena on mineral surfaces

Nuclear microprobe analysis has been used to study the aqueous sorption of cadmium and selenium at different solution pH values onto hydroxyapatite. By coupling Particle Induced X-ray Emission (PIXE) and Rutherford Backscattering (RBS) microanalyses, we have quantified the concentration and modeled the depth distribution of Cd and Se in particles of calcium hydroxyapatites (HAP). No cadmium precipitation was observed for those experiments in which the initial concentration was greater than the solubility of Cd(OH)2 and CdCO3 at solution pH=9 and 12. The observation of the solid by transmission and scanning electron microscopies, SEM and TEM, showed the polycrystalline nature of the particles; these particles were constituted by aggregated nanocrystals. This additional information allowed us to interpret the incorporation of Cd and Se into the apatitic substrate as a penetration in the intra-particle porosity generated by this aggregation of crystals and probably not as diffusion in the solid structure.

Epidemiological changes in hepatitis C virus genotypes in France: evidence in intravenous drug users

Hepatitis C virus (HCV) genotypes are distributed differently depending on geography and route of infection. We characterized the distribution of genotypes in a large cohort of patients with chronic hepatitis C in the South-east of France and evaluated the relative prevalence according to time of acquisition. One thousand, one hundred-and-eighty-three patients who were anti-HCV-positive were studied. HCV genotype distribution has changed significantly from the 1960s to 2000. The prevalence of genotype 1b decreased from 47% before 1978 to 18.8% in the 1990s while the prevalence of genotype 1a and 3a increased during the same period from 18% and 15.3% to 28.8% and 26.3%, respectively. The logistic regression model showed that genotype 1a was significantly more common in patients infected through intravenous drug injection odds ratio ((OR): 2.08, P < 0.01) and after 1990 (OR: 1.98, P < 0.05). Genotype 1b was significantly less frequent in patients infected through intravenous drug injection (OR: 0.17, P < 0.001) and has decreased since 1978 (OR: 0.27, P < 0.001). Genotype 3a was independently associated with intravenous drug injection (OR: 6.1, P < 0.001) and tattooing (OR: 8.01, P < 0.001) and was more frequent in the 1979-90 period (OR: 2.05 and 1.74, P < 0.001 and P < 0.05). Our results show a modification of HCV genotypes distribution over the last four decades due to an increase of intravenous drug use (IVDU) contamination and an evolution of HCV genotypes distribution only in IVDU population characterized by a decrease of genotype 1b, an increase of genotype 3a from 1970 to 1990 and a higher increase of genotype 1a which is currently the predominant genotype in our population.

Study of hydrophobic interactions between acylated proteins and phospholipid bilayers using BIACORE

Intracellular proteins of eukaryotic cells are frequently covalently modified by the addition of long chain fatty acids. These modifications are thought to allow otherwise soluble proteins to associate with membranes by lipid-lipid based hydrophobic interactions. The purpose of this work was to quantify the effect of acyl chain length on hydrophobic interactions between acylated proteins and phospholipid monolayers. The binding of an artificially acylated model protein to electrically neutral phospholipids was studied by surface plasmon resonance, using BIACORE. Kinetic rates for the binding of bovine pancreatic ribonuclease A (RNase A), monoacylated on its N-terminal lysine with fatty acids of 10, 12, 14, 16 or 18 carbon atoms, to phospholipids on hydrophobic sensor chips, were measured. Unlike unmodified ribonuclease, acylated RNase A bound to the phospholipids, and the association level increased with the acyl chain length to reach a maximum for C16. Reproducible kinetics were obtained which did not fit a 1:1 Langmuir model but rather a two-step binding profile.

Analysis of habituated embryogenic lines in Asparagus officinalis L.: growth characteristics, hormone content and ploidy level of calli and regenerated plants

Habituated asparagus embryogenic lines derived from eleven genotypes were maintained on hormone-free medium and grew actively through secondary embryogenesis. Secondary embryos were of single cell origin and emerged from the transversal division of some epidermal or subepidermal cotyledonary cells of primary embryos. The intensity of secondary embryogenesis was found to be variable between embryogenic lines. Plants regenerated from three of these lines have been previously demonstrated to carry a mutation whose phenotype was the direct appearance of somatic embryos on apices or nodes cultured on hormone-free medium. Habituated lines of embryogenic calli and various tissues of embryogenic mutant and wild type plants were analysed for their hormonal content in ABA, IAA, iP, Z and their metabolites ABA-GE, iPA, iMP, ZR. No significant difference was found between different embryogenic lines, except the level of iPA, or between cladophyll or apex cultures of mutant and wild type plants. Flow cytometry analyses indicated only 34% of the embryogenic lines were diploid, most of the others being tetraploid, but 62% of regenerated plants from these lines were diploid. This indicated the process of maturation and conversion selected diploid embryos in the embryogenic lines.

Direct transactivation of c-Ha-Ras gene by p53: evidence for its involvement in p53 transactivation activity and p53-mediated apoptosis

p53 protein is a sequence-specific transcriptional activator which induces the expression of a number of cellular genes involved in different metabolic pathways. We report that the computer-selected sequence in human and mouse C-Ha-Ras gene confers to a reporter gene the ability to be directly transactivated by wild-type p53 either overexpressed or activated in response to a cellular stress. By analysing human transformed cell lines, we showed, at both mRNA and protein level, that the endogenous c-Ha-Ras gene expression is positively regulated by wt p53 protein. The stimulation of c-Ha-Ras gene expression in Saos-2Ts cells by a temperature shift down to the permissive temperature for the p53-wt conformation is associated with a significant increase in the activated form of p21c-Ha-Ras protein. Furthermore, in human transformed cell lines, the transient expression of a dominant interfering mutant of c-Ha-Ras greatly reduced the ability of p53 to induce apoptosis and inhibited the p53-dependent transactivation. This is due, at least in part, to a decrease in the protein (but not mRNA) level of the transiently expressed p53, indicating that inactivation of p21c-Ha-Ras signalling pathways led to a specific degradation of p53 protein. We therefore suggest that, by inducing c-Ha-Ras, p53 activates a positive feedback loop that counteracts the negative feedback loop mediated by Mdm2.

Covert transmission of hepatitis C virus during bloody fisticuffs

Hepatitis C virus (HCV) is transmitted primarily through direct percutaneous exposure to infected blood. Sporadic HCV cases exist and may represent more than 10% of HCV transmission. We report the first case of documented transmission of HCV during a fight from a person who unknowingly had chronic HCV infection to a person who subsequently contracted acute hepatitis C. Patient-to-patient transmission was ascertained by sequence analysis of part of the NS5B genome and phylogenetic analysis. This case report suggests that sporadic HCV infection may be a result of blood exposure. This example of transmission could have a major impact in sports such as boxing or rugby. We suggest that in any fight, single use or nondisposable material should be used to dry blood to avoid such contamination.

Characterization and molecular basis of the oligomeric structure of HIV-1 nef protein

The Nef protein of human immunodeficiency virus type I (HIV-1) is an important determinant for the onset of AIDS disease. The self-association properties of HIV-1 Nef are analyzed by chemical cross-linking, dynamic light scattering, equilibrium analytical ultracentrifugation, and NMR spectroscopy. The experimental data show that the HIV-1 Nef core domain forms stable homo-dimers and trimers in solution, but not higher oligomers. These Nef homomers are not covalently linked by disulfide bridges, and the equilibrium between these forms is dependent on the Nef concentration. We further provide the molecular basis for the Nef core dimers and trimers obtained by analysis of crystallographic models. Oligomerization of biological polypeptides is a common tool used to trigger events in cellular signaling and endocytosis, both of which are targeted by Nef. The quaternary structure of Nef may be of physiological importance and may help to connect its cellular targets or to increase affinity of the viral molecule for its ligands. The herein described models for Nef dimers and trimers will allow further mutational studies to elucidate their role in vivo. These results provide novel insight into the structural and functional relationships of this important viral protein. Moreover, the oligomer interface may represent a novel target for the design of antiviral agents.

MOMP (major outer membrane protein) of Campylobacter jejuni; a versatile pore-forming protein

The great majority of trimeric porins of Gram-negative bacteria cannot be dissociated into monomers without disrupting their folded conformation. The porin of Campylobacter jejuni, however, displays two folded structures, a classical oligomer and a monomer resistant to detergent denaturation. We probed the transition of trimer to monomer using light scattering experiments and examined the secondary structures of these two molecular states by infra-red spectroscopy. The channel-forming properties of both trimer and monomer were studied after incorporation into artificial lipid bilayers. In these conditions, the trimer induced ion channels with a conductance value of 1200 pS in 1 M NaCl. The pores showed marked cationic selectivity and sensitivity to low voltage. Analysis of the isolated monomer showed nearly the same single-channel conductance and the same selectivity and sensitivity to voltage. These results indicate that the folded monomer form of C. jejuni MOMP displays essentially the same pore-forming properties as the native trimer.

Control of seed dormancy in Nicotiana plumbaginifolia: post-imbibition abscisic acid synthesis imposes dormancy maintenance

The physiological characteristics of seed dormancy in Nicotiana plumbaginifolia Viv. are described. The level of seed dormancy is defined by the delay in seed germination (i.e the time required prior to germination) under favourable environmental conditions. A wild-type line shows a clear primary dormancy, which is suppressed by afterripening, whereas an abscisic acid (ABA)-deficient mutant shows a non-dormant phenotype. We have investigated the role of ABA and gibberellic acid (GA(3)) in the control of dormancy maintenance or breakage during imbibition in suitable conditions. It was found that fluridone, a carotenoid biosynthesis inhibitor, is almost as efficient as GA(3) in breaking dormancy. Dry dormant seeds contained more ABA than dry afterripened seeds and, during early imbibition, there was an accumulation of ABA in dormant seeds, but not in afterripened seeds. In addition, fluridone and exogenous GA(3) inhibited the accumulation of ABA in imbibed dormant seeds. This reveals an important role for ABA synthesis in dormancy maintenance in imbibed seeds.

[Lyell syndrome and Stevens-Johnson syndrome caused by lamotrigine]

BACKGROUND

Lamotrigine is a new anticonvulsant belonging to the triazine family. Several cases of Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) have been described in patients taking this drug. We report 2 cases in children attending the same hospital.

CASE REPORTS

Two children, aged 9 and 13 years, developed SJS and TEN respectively, 3 and 28 days after lamotrigine was added to their usual anticonvulsant regimen. In both cases, outcome was favorable despite major decline in psychomotor capacity in one. In the first case, chronological attributability was plausible for lamotrigine and doubtful for sodium valproate, clonazepam and hydrocortisone. In the second case, chronological attributability was probable for amoxicillin, plausible for lamotrigine and doubtful for sodium valproate, but the numerous previous absorptions of amoxicillin made lamotrigine more suspect.

DISCUSSION

The risk of Steven-Johnson syndrome and toxic epidermal necrolysis is high with lamotrigine with an estimated frequency of 1/1000. This risk is probably higher than with other anticonvulsants. Associating lamotrigine with sodium valproate increases the frequency of adverse skin reactions.

Assessment of spontaneous fluctuations of viral load in untreated patients with chronic hepatitis C by two standardized quantitation methods: branched DNA and Amplicor Monitor

Quantitation of hepatitis C virus (HCV) RNA in serum has been used to predict and monitor the efficacy of interferon therapy in chronic HCV infection. We prospectively studied the fluctuation of viremia by a longitudinal follow-up of HCV RNA levels for 2 months in six untreated patients. Spontaneous fluctuations of HCV RNA ranged from 2.8- to 5.7-fold with branched DNA assay and from 2.9- to 5.6-fold with Monitor. These large spontaneous fluctuations (up to 0.75 log), observed daily, weekly, and monthly, raise doubt about the clinical value of a single assessment of pretherapeutic viremia.

HIV-1 Nef protein: purification, crystallizations, and preliminary X-ray diffraction studies

Human immunodeficiency virus Nef protein accelerates virulent progression of AIDS by its interaction with specific cellular proteins involved in cellular activation and signal transduction. Here we report the purification and crystallization of the conserved core of HIV-1LAI Nef protein in the unliganded form and in complex with the wild-type SH3 domain of the P59fyn protein-tyrosine kinase. One-dimensional NMR experiments show that full-length protein and truncated fragment corresponding to the product of HIV-1 protease cleavage have a well-folded compact tertiary structure. The ligand-free HIV-1 Nefcore protein forms cubic crystals belonging to space group P23 with unit cell dimensions of a = b = c = 86.4 A. The Nef-Fyn SH3 cocrystals belong to the space group P6(1)22 or its enantiomorph, P6(5)22, with unit cell dimensions of a = b = 108.2 A and c = 223.7 A. Both crystal forms diffract to a resolution limit of 3.0 A resolution using synchrotron radiation, and are thus suitable for X-ray structure determination.

ZEA3: A Negative Modulator of Cytokinin Responses in Plant Seedlings

In Nicotiana plumbaginifolia cytokinins affect seedling development by inhibiting root growth and hypocotyl elongation and by stimulating cotyledon expansion. The zea3.1 mutant was selected for its inability to grow in conditions of low nitrogen and for its ability to grow independently on inhibitory concentrations of zeatin (J.D. Faure, M. Jullien, M. Caboche [1994] Plant J 5: 481-491). The zea3.1 growth response to cytokinins is reflected by an increase in cotyledon expansion due to cell division and by a swelling of the hypocotyl due to cell enlargement. An analysis of the seedling's root length and fresh weight over a wide range of benzyladenine concentrations showed that zea3.1 plants exhibit a higher sensitivity and an amplified response to cytokinins. A similar response of zea3.1 to benzyladenine was also seen in the expression of msr1, a cytokinin-regulated gene. Regulation of msr1 expression by protein phosphorylation was unaffected by the zea3.1 mutation. No significant differences in cytokinin and auxin levels were found between zea3.1 and wild-type seedlings, suggesting that the mutant phenotype is not caused by an alteration of these hormone levels. The data presented suggest that ZEA3 negatively modulates cytokinin responses and may function as a broad regulator of seedling development.

Crystallization of monoacylated proteins: influence of acyl chain length

The crystallization of monoacylated proteins has been investigated using a model system. Acylated derivatives of bovine pancreatic ribonuclease A, differing in their acyl chain lengths (10 to 16 carbon atoms), have been prepared using reverse micelles as microreactors. With one fatty acid moiety per polypeptide chain, covalently attached to the NH2 terminus of the protein, all the modified proteins have similar enzymatic activity and hydrodynamic radius as the native protein. Only the caprylated derivative can give crystals which diffract to high resolution. The resolved structure indicates that: (i) the protein folding is not modified by the chemical modification, (ii) the capryl moiety is not buried within the molecule but available for external interactions. Dynamic light scattering experiments on concentrated solutions show that the protein-protein interactions are dependent on acyl chain length. Proteins with the longest attached chains (14 and 16 carbon atoms) tend to self-associate through acyl group interactions.

[Sarcoidosis with hematologic involvement and hypogammaglobulinemia]

BACKGROUND

Hematological changes are uncommon in childhood sarcoidosis.

CASE REPORT

Case 1. This patient developed severe hemolytic anemia associated with splenomegaly at the age of 11 months. A second episode of hemolysis was seen at the age of 6 years; it was associated with thrombocytopenia and hypogammaglobulinemia. A partial splenectomy permitted histological diagnosis of sarcoidosis that was confirmed by elevated angiotensin-converting enzyme level, and subsequently developement of pulmonary involvement. Case 2. This boy suffered from autoimmune hemolytic anemia and thrombocytopenia associated with splenomegaly at the age of 3 years. At the age of 7 years, he had splenomegaly, enlarged cervical and lomboaortic lymph nodes and hypogammaglobulinemia. Diagnosis of sarcoidosis was made from lymph nodes and spleen biopsies after splenectomy; the patient had increased angiotensin-converting enzyme concentration, and subsequently developed specific renal involvement.

CONCLUSION

Association of hemolytic anemia, thrombocytopenia, hypogammaglobulinemia and splenomegaly should suggest the diagnosis of sarcoidosis and could be considered as part of the disease spectrum.

Evidence for a dimeric intermediate on the crystallization pathway of ribonuclease A

Early steps in the crystallization process of pancreatic ribonuclease have been investigated by time-dependent fluorescence anisotropy, using a labeled protein as a fluorescent probe. Previous experiments have shown that steady-state fluorescence anisotropy is sensitive to protein-protein interactions and can be used to find new crystallization conditions. The present work describes an attempt, by means of time-resolved experiments, to detect and characterize species appearing in the early stages of the crystallization pathway. Fluorescence anisotropy decay was measured with synchrotron radiation as a light source under a variety of conditions where it is known that the solutions tend towards crystallization; the decay was analyzed by a maximum-entropy method that calculates a rotational correlation-time distribution. Fluorescence anisotropy originates in the Brownian rotatory motion of macromolecules and the values of the correlation times are related to the size and shape of different species present in the solution. In the presence of high salt concentrations, a bimodal distribution is always observed. Whereas a peak of protein monomer is still present, a second peak appears as a stable intermediate in the crystallization pathway. The correlation time of this new species varies between two and three times the correlation time of the monomer. The second peak is possibly the symmetrical dimer of the ribonuclease molecules commonly observed in all the high-salt crystal forms.

Zea3: a pleiotropic mutation affecting cotyledon development, cytokinin resistance and carbon-nitrogen metabolism

When photomorphogenesis takes place during early plant development, the cotyledons undergo a metabolic transition from heterotrophic sink metabolism to autotrophic source metabolism. A mutant screen was devised for seedlings affected in the regulation of nitrate assimilation during this early sink-source transition in Nicotiana plumbaginifolia. A mutant (EMS 203.6) was isolated for its inability to grow on low nitrate concentration. In contrast to wild-type (WT) plants, the mutant cotyledons remained tightly attached to each other throughout seedling development. It was found that a low carbon/nitrogen ratio (C/N ratio) in the medium was required for mutant growth. The higher the ratio was, the more the growth was inhibited. Mutant EMS 203.6 accumulated all amino acids in permissive conditions (low C/N ratio), and all amino acids and sugars also in selective (high C/N ratio) conditions. In addition, sucrose in the medium repressed light-regulated genes involved in nitrate assimilation and in photosynthesis in the mutant but not in the WT plants. The mutation was mapped to the Zea3 complementation group which confers resistance to zeatin. This zeatin resistance was associated with a hypertrophy of mutant cotyledons in response to cytokinin. Both cytokinin resistance and sensitivity to a high C/N ratio were not observed in etiolated mutant seedlings and were restricted to the jointed-cotyledon developmental stage. Previous physiological studies showed evidence for a role of cytokinins in the expression of nitrate reductase. Here, the first genetic evidence for a link between carbohydrate/nitrogen metabolism and cytokinin action during early development is provided.

Evidence for in vitro induced mutation which improves somatic embryogenesis in Asparagus officinalis L

Somatic embryogenesis from different genotypes of Asparagus officinalis L. could be obtained by in vitro culture of shoot apices. Apices were first cultured on an auxin-rich inducing medium and then transferred onto a hormone-free development medium. All genotypes tested in this way produced a few somatic embryos. In some experiments, during the development phase, a new kind of friable highly embryogenic tissue appeared in a random manner. These tissues could be continuously subcultured on a hormone-free medium and were named embryogenic lines. Five of these embryogenic lines regenerated plants from somatic embryos. These regenerated plants exhibited an increased embryogenic response compared to the parent plants; e.g. apex culture produced somatic embryos without any auxin treatments. For one of the embryogenic lines, a genetic analysis showed that the improved embryogenic response of regenerated plants was controlled by a mendelian dominant monogenic mutation.

Identification of two loci involved in phytochrome expression in Nicotiana plumbaginifolia and lethality of the corresponding double mutant

Four Nicotiana plumbaginifolia mutants exhibiting long hypocotyls and chlorotic cotyledons under white light, have been isolated from M2 seeds following mutagenesis with ethyl methane sulphonate. In each of these mutants, this partly etiolated in white light (pew) phenotype is due to a recessive nuclear mutation at a single locus. Complementation analysis indicates that three mutants, dap5, ems28 and ems3-6-34, belong to a single complementation group called pew1, while dap1 defines the pew2 locus. The mutants at pew1 contain normal levels of immunochemically detectable apoprotein of the phytochrome that is relatively abundant in etiolated seedlings, but are deficient in spectrophotometrically detectable phytochrome, whether seedlings are grown in darkness or light. Moreover, biliverdin, a precursor of the phytochrome chromophore, restores light-regulated responses in pew1 mutants and increases their level of photoreversible phytochrome when grown in darkness. These results indicate that the pew1 locus may be involved in chromophore biosynthesis. The mutant at the pew2 locus displays no photoreversible phytochrome in etiolated seedlings, but does contain normal levels of photoreversible phytochrome when grown in the light. Biliverdin had little effect on light-regulated responses in this mutant. In addition, biliverdin did not alter the level of phytochrome in etiolated seedlings. These observations lead us to propose that this mutant could be affected in the phyA gene itself. We have also obtained the homozygous double mutant at the pew1 and pew2 loci. This double mutant is lethal at an early stage of development, consistent with a critical role for phytochrome in early development of higher plants.

Crystal structure of a fluorescent derivative of RNase A

The crystal structure of RNase A chemically modified with the fluorescent probe, N-[[(iodoacetyl)-amino]ethyl]-5-naphthylamine-1-sulfonic acid (1,5-IAENS), has been solved and refined to high resolution. It yields information on the mode of binding, the mobility of a probe commonly used in spectroscopic studies, and anion binding sites in RNase A. Trigonal crystals of the fluorescent derivative grown in sodium or cesium chloride and ammonium sulfate, pH 5.1, were nearly isomorphous with those of a semisynthetic RNase [DeMel, et al. (1992) J. Biol. Chem. 267, 247-256]. Refinement starting from semisynthetic RNase led to a model with R = 20% against 1.7-A diffraction data from crystals in ammonium sulfate and another model with R = 17% against 1.9-A data taken in the presence of 3 M NaCl. The second model contains three chloride ions: one is at the active site, and the other two are at molecular interfaces. Otherwise, the two models are very similar. The fluorophore has very little effect on the protein conformation. It is found to be covalently attached to the active site His-12 with the naphthyl group stacked on the imidazole ring of His-119. It remains largely accessible to solvent and in a polar environment on the protein surface, even though the fluorescence emission spectrum is blue shifted as it is in nonpolar solvents.

[Neural sarcoidosis in children. A case report]

A case of cerebral sarcoidosis of fortuitous discovery is reported in an adolescent. Neurosarcoidosis is exceedingly rare in the pediatric age groups. Clinical manifestations are widely variable and nonspecific, making diagnosis difficult in patients without extraneurologic involvement. The mainstay of management is early, prolonged corticosteroid therapy. Outcome varies with location of the lesions.

[Needle puncture biopsy: the contribution of extemporaneous examination of samples in the diagnosis of malignant liver tumors]

In this retrospective study, the authors compared the sensitivity and specificity, in terms of the diagnosis of malignancy, of two techniques of ultrasound-guided biopsy of liver tumours. The first technique involving fine needle biopsy with cytological and histological analysis of the specimen was carried out in 39 patients. A technique using a wide calibre needle with frozen section examination of the fragment obtained was performed in 27 patients. All patients had one or more malignant liver tumours. Sensitivity and specificity of the technique with frozen section histology were both 100 per cent, while figures for the technique with delayed histological study were 84.6 and 87.4 per cent. This study suggests that frozen section histology might be associated with greater sensitivity than delayed histology.

Agrobacterium-mediated transformation of Asparagus officinalis L. long-term embryogenic callus and regeneration of transgenic plants

Twenty-three independent kanamycin resistant lines were obtained after cocultivation of longterm embryogenic cultures of three Asparagus officinalis L. genotypes with an Agrobacterium tumefaciens strain harboring ß-glucuronidase and neomycin phosphotransferase II genes. All the lines showed ß-glucuronidase activity by histological staining. DNA analysis by Southern blots of the kanamycin resistant embryogenic lines and of a plant regenerated from one of them confirmed the integration of the T-DNA.

Crystal packing in six crystal forms of pancreatic ribonuclease

We compare the molecular packing of bovine pancreatic ribonuclease A (RNase A) in six crystal forms, two grown with alcohol, three with high salt and one with polyethylene glycol as a precipitant. The six packings differ in the number of molecules in contact and in the extent of the contacts, which bury 1570 A2 to 2790 A2 of the RNase surface. Regions of the protein surface involved in the six packings cover almost the whole RNase molecule. The abundance of polar interactions, about one per 200 A2, is the same in all types of precipitants. All molecule-to-molecule contacts are different in the six crystal forms, except for the one that forms a RNase dimer. The dimer has a large interface covering 1800 A2 and eight to ten polar interactions. Its presence in the three salt-grown crystal forms suggests that it is an intermediate in salt induced crystallization. In contrast, the two alcohol-grown forms contain only small interfaces, implying a different mechanism of nucleation.

[Liddle syndrome (or pseudo-hyperaldosteronism). Long-term development and erythrocyte potassium flow study in 4 cases]

BACKGROUND

Liddle's syndrome (or pseudoprimary aldosteronism) is a rare hereditary disease; only 18 cases have been reported since 1963. Its cause remains unclear, but one of its features is increased cell membrane permeability to ions.

PATIENTS AND METHODS

A diagnosis of Liddle's syndrome was made in 4 new cases, all female, two of them sisters (cases n0 3 and 4), at the ages of 2, 12, 5 and 4 years. The first manifestations were dehydratation with hypokalemia at 6 months (case n0 1), hypertension at 2 years (case n0 2), polydipsia with poor weight and height gain at 5 and 4 years of age (cases n0 3 and 4). At diagnosis, all the patients had severe hypertension, metabolic alkalosis, hypokalemia and hyperkaliuria, low plasma renin activity and serum aldosterone levels. Administration of antihypertensive agents was without effect, but the hypertension was reduced when triamterene and low-sodium diet were used. Hypercalciuria was observed in 2 cases and nephrocalcinosis in 2 (case n0 1 had both hypercalciuria and nephrocalcinosis). The 2 oldest patients (n0 3 and 4) developed progressive kidney failure, possibly due to reno-vascular disease secondary to hypertension. Patient n0 3 underwent kidney transplantation 18 years after the first symptoms of the disease. This resulted in the complete disappearance of her hypokalemia and hypertension. The red blood cell membrane permeability to K+ and Cl- was studied in all 4 cases before triamterene treatment. The passive permeability to K+ and (K+/Cl-) cotransport were both elevated. A second study, 3 years (cases n0 2 and 3) and 8 years (cases n0 1 and 4) later, of patients treated with triamterene showed low values for passive K+ permeability and (K+/Cl-)-cotransport.

CONCLUSIONS

The 4 new cases of Liddle's syndrome had the classic features of the disease, except for hypercalciuria and nephrocalcinosis in 2 of them. The cell membrane permeability data are difficult to interpret. Hypokalemia and hypertension were immediately corrected after kidney transplantation in one case and remained so for 4 years, suggesting that this disease is tubular in origin.

Packing forces in ribonuclease crystals

Packing in Ribonuclease A and Ribonuclease S crystals have been compared in order to determine the possible role of the precipitant on lattice contacts. Both proteins have similar tertiary structures, but they crystallize in different space groups depending on the precipitating agent. It is found that packing differs either by the number of nearest neighbours or by the size of surface areas buried in individual contacts. Ammonium sulfate seems to promote hydrophobic interactions with interfaces similar to those found in oligomeric proteins. Organic precipitants favour electrostatic interactions.

Allosteric transition of aspartokinase I-homoserine dehydrogenase I studied by time-resolved fluorescence

The allosteric transition of threonine-sensitive aspartokinase I-homoserine dehydrogenase I from Escherichia coli has been studied by time-resolved fluorescence spectroscopy. Fluorescence decay can be resolved into 2 distinct classes of tryptophan emitters: a fast component, with a lifetime of about 1.5 ns; and a slow component, with a lifetime of about 4.5 ns. The fluorescence properties of the slow component are modified by the allosteric transition. In the T-form of the enzyme stabilized by threonine, the lifetime of the slow component is longer, with a red-shifted spectrum; its accessibility to quenching by acrylamide becomes slightly higher without any decrease of fluorescence anisotropy. These results indicate a change in polarity of the slow component environment. The quaternary structure change associated with the allosteric transition probably involves global movements of structural domains without leading to any local mobility on the nanosecond time-scale. We suggest that the slow component corresponds to the unique tryptophan of the buried kinase domain.

Early stimulation by EGF plus insulin of rRNA, c-fos, and actin mRNA expression: inhibition by cytochalasin D

Stimulation of membrane ruffling is one of the first events induced by addition of growth factors to quiescent cultures. In order to assess the importance of intact cytoskeleton in induction, by EGF + insulin, of early events such as stimulation of rRNA, c-fos, and actin mRNA expression, we studied the effect of cytochalasin D (CD) on these metabolisms. We observed that CD slightly increased rRNA synthesis in nonstimulated cells; conversely, it decreased rRNA synthesis in cells stimulated by EGF + insulin. The maximal inhibition observed was 60%. The c-fos mRNA was not expressed in control cells and was accumulated in cells stimulated by the mixture of EGF + insulin; this accumulation was inhibited by CD. Actin mRNA was expressed in control cells and its expression was stimulated by EGF + insulin. Addition of CD decreased actin mRNA accumulation in stimulated cells but increased this accumulation in unstimulated cells. Our results, taken together, show that CD specifically affected the stimulation of rRNA and mRNA expression induced by growth factors and suggest that intact cytoskeleton and possibly membrane ruffling favored this stimulation.

Quenching by acrylamide and temperature of a fluorescent probe attached to the active site of ribonuclease

The fluorescence properties of ribonuclease labelled at its active site with N-(iodoacetylamino)-ethyl-5-naphthylamine-1-sulfonic acid have been studied at different temperatures and in the presence of acrylamide. The rate constant for the quenching of the fluorescence of labelled ribonuclease by acrylamide is apparently not limited by the "accessibility" of the probe: similar values are obtained for the native and denatured states of the protein. Instead, acrylamide seems to be a rather inefficient quencher of this fluorescent group [acetamidoamino)ethyl-5-naphthylamine-1-sulfonic acid), as shown by non-linear Stern-Volmer representations, biphasic decay kinetics, and a low value of the rate constant. The fluorescence intensity of the native state of the labelled protein is highly sensitive to temperature and exhibits a 20% decrease for an increase of temperature of from 10 degrees C to 30 degrees C, independent of solvent viscosity. This thermal quenching is specific for the native conformation and disappears when the protein is unfolded. When the fluorescence lifetime of the label is shortened by addition of acrylamide, the effect of temperature becomes identical for native and unfolded structures. This suggests that the cause of the thermal quenching is the presence of conformational fluctuations within the native protein which apparently take place in the time range from 35 to 200 ns.

Inhibition by quercetin of the release of density dependent-inhibition of cell growth in RSV-transformed chicken cells

The expression of src gene in dense cultures of chick embryo fibroblasts (CEF) infected by a thermosensitive mutant (NY68) of RSV released density-dependent inhibition of growth and induced in these cells a large increase in DNA, RNA and protein synthesis. This stimulation of cellular metabolism was abolished in the presence of quercetin. Furthermore, quercetin added to the culture medium also inhibited the stimulation of pp60src kinase due to the expression of transformation.

Early release of the density-dependent inhibition of phosphate uptake and ATP synthesis after src gene expression in chick embryo fibroblasts

Our results showed that the expression of the src gene in chick embryo fibroblasts (CEF) released the density-dependent inhibition (DDI) of phosphate metabolism (phosphate uptake and phosphorylation of small organic compounds). With increasing cell density, phosphate metabolism decreased by 58% in normal CEF and, in contrast, increased by 20% in Rous sarcoma virus (RSV)-transformed CEF. The same change in the DDI was observed in CEF infected by NY68 (a ts mutant for transformation of RSV) and maintained at the permissive temperature (37 degrees C) instead of the restrictive temperature (41.5 degrees C) for the expression of transformation. An interesting feature was that the release of the DDI of phosphate metabolism was an early event in the process of transformation, since it was almost concomitant with the stimulation of the pp60 src kinase activity following the shift from 41.5 to 37 degrees C of NY68 CEF. The phosphorylation of small organic compounds (Po) was more strongly increased by the change in temperature than was 32Pi accumulation. Furthermore, the percentage increases of Po and adenosine triphosphate (ATP) labelling with 32P were similar, suggesting that the expression of src gene enhanced ATP synthesis. In glucose-free medium, the stimulation of Po-labelling was still observed but was decreased. Therefore the activation of glycolytic activity is not an absolute requirement, but is necessary for the maximum effect of transformation on the release of DDI of phosphate metabolism. Oligomycin added in complete medium did not prevent the increase in Po-labelling. From these results, we assumed that ATP turnover was stimulated as a consequence of enhanced ATP degradation. We verified that the stimulation of Po phosphorylation was not a consequence of increased ATP utilization for RNA or protein synthesis. The stimulation of Po labelling was specifically abolished by quercetin. This drug inhibited the transformed cells more strongly than the non-transformed cells.

Energy-transfer measurements on a double fluorescent labeled ribonuclease A

Two fluorescent groups have been covalently attached to ribonuclease A: first, the alpha-amino group is labeled upon reaction with fluorescein isothiocyanate, and second, one of the active site histidine residues is modified by N-[[(iodoacetyl)amino]ethyl]-5-naphthylamine-1-sulfonic acid. Among the products of these two successive chemical modifications, a derivative bearing one label on Lys-1 and the other label on His-119 can be isolated and characterized. Because of their spectral properties, these two fluorophores, fluorescein and N-[(acetamido)ethyl]-5-naphthylamine-1-sulfonic acid, are suitable for measuring resonance energy transfer within a single protein molecule. The efficiency of the energy transfer is close to 100% in the native state and is reduced to about 50% in the guanidine-unfolded state. This efficiency is further diminished upon reduction of the disulfide bonds in denaturing conditions. The efficiency of energy transfer has been determined independently from both emission and excitation spectra of the double-labeled protein, when unfolded with intact disulfide bonds. The average distance between the two fluorescent groups can be obtained from these measurements: it increases from 20 A at most in the native state to 46 A or more in the unfolded state.

Fluorescent probe of ribonuclease A conformation

The reaction of ribonuclease (RNase) with N-[[(iodoacetyl)amino]ethyl]-5-naphthylamine-1-sulfonic acid (1,5-IAENS) yields a derivative in which one fluorescent group is covalently attached to the protein. Several arguments suggest that the chemical modification has occurred at the enzyme active site: (i) 1,5-IAENS should have the same specificity as iodoacetamide, i.e., carboxymethylate one histidine of the active site; (ii) the derivatized protein is enzymatically inactive; (iii) in the native state of the protein, the fluorescent group is (almost) completely protected from the aqueous solvent; (iv) this group has no motions other than those of the protein. The fluorescence properties of the derivatized RNase change markedly upon unfolding induced by guanidine hydrochloride (Gdn . HCl), as seen from fluorescence intensity, maximum emission wavelength, and polarization measurements. Upon Gdn . HCl-induced unfolding, the fluorescent group is transferred from a nonpolar to a highly polar environment. Dynamic fluorescence measurements show also that unfolding results in a markedly increased mobility of the fluorescent label with respect to its proteic environment. These results are compared to those of Young & Potts (1963) [Young, D. M., & Potts, J. T. (1963) J. Biol. Chem. 238, 1995--2002], who studied the fluorescence properties of a surface-labeled derivative of RNase.

Amino Acid Uptake into Cultivated Mesophyll Cells from Asparagus officinalis L

The uptake of threonine, aspartic acid, and isoleucine into cultivated asparagus cells was examined under culture conditions.Transport was linear with time and with the number of cells present in the assay. The upake of the three amino acids obeyed Michaelis-Menten kinetics with apparent affinities in the range of 0.1 to 0.02 millimolar. Azide and 2,4-dinitrophenol caused inhibition of threonine uptake. Reciprocal competitive inhibitions were found between threonine, aspartic acid, and isoleucine. Methionine and lysine competitively inhibited the uptake of these three amino acids. These results and the comparison of apparent affinities and inhibition constants are in favor of only one uptake system for threonine, aspartic acid, isoleucine, methionine, and lysine with different affinities for the different amino acids. All other amino acids with the exception of histidine, arginine, asparagine, and hydroxyproline inhibited threonine uptake. It is most likely that at least one component of the uptake system is shared by all amino acids.

Diffusible factor(s) controlling density inhibition of 3T3 cell growth: a new approach

In 3T3 Swiss mouse fibroblasts, incorporation of phosphate into cells and phosphorylation of small organic compounds were increased by shaking dense cultures. This response was not obtained with SV40 transformed Swiss 3T3 cells (SV-3T3). It appeared likely that these results could be accounted for by an inhibitor released from 3T3 cells but not from SV-3T3 cells. Our new method of co-incubation of sparse and dense cultures allowed us to demonstrate inhibition of growth and phosphate metabolism in sparse 3T3 cultures which were shaken in the presence of dense cultures. The inhibition was much less when the cultures were co-cultivated but not shaken. The inhibition of phosphate incorporation in acid-soluble and acid-insoluble fractions of sparse cultures was observed as early as 20 minutes of co-incubation in the presence of dense cultures, so this inhibition is not the result of depletion of growth factors in the medium. Our experiments suggest that an inhibitor(s) was released from dense cultures of 3T3 cells.

Dependence upon pH of steady-state parameters for the beta-galactosidase-catalysed hydrolyses of beta-D-galactopyranosyl derivatives of different chemical types

The effect of pH upon the beta-galactosidase-catalyzed hydrolyses of aryl galactosides is essentially similar for each of the three steps of their hydrolysis. It differs markedly from that on the hydrolysis of galactosyl pyridinium salts; these proceed through a 'non-bottleneck' pathway. While pH increase abolishes the rate of every step of the reaction for aryl galactosides, it favors the first step of hydrolysis of the galactosyl pyridinium salts, which supports the hypothesis that catalysis of these compounds originates largely in non-covalent interactions.