Showing papers by "University of Montpellier published in 1989"

Efficient tunable solid-state laser near 630 nm using sulforhodamine 640-doped silica gel

Abstract: Lasing is observed near 630 nm in a sulforhodamine 640-doped silica gel pumped by frequency-doubled radiation from a Q-switched Nd: YAG laser. A conversion efficiency of 20% is obtained. The laser wavelength is tunable over 40 nm.

Climate patterns revealed by pollen and oxygen isotope records of a Tyrrhenian sea core

Abstract: THE analysis of pollen from marine cores has produced continental palaeoclimate records which have been directly correlated with the oxygen isotope record of global ice volume and regional climate1–3. Here we tie the palaeoclimate of southern Europe to this global climate signal by reporting continuous pollen and δ18O records of a well-dated core in the Tyrrhenian Sea for the time span of 55–9 kyr BP. These records show a strong covariation between the marine δ18O reversed curve and a good terrestrial climate indicator, namely the pollen abundance of deciduous oak from the upland sub-humid Mediterranean forest of southern Italy and Sicily, which seems mainly constrained by moisture variation. The Artemisia and grass pollen abundances document the shift between continental semi-desert and oceanic steppe climates. Repetitive successions between 55 and 33 kyr BP of grass, oak, Artemisia and Abies pollen abundance peaks occur in locked phase with δ18O depletion events and indicate that regional vegetation cycles closely accompany deglacial pulses of global extent.

Antigenic probes locate binding sites for the glycolytic enzymes glyceraldehyde-3-phosphate dehydrogenase, aldolase and phosphofructokinase on the actin monomer in microfilaments.

Abstract: The topology of the interfaces between actin monomers in microfilaments and three glycolytic enzymes (glyceraldehyde-3-phosphate dehydrogenase, aldolase and phosphofructokinase) was investigated using several specific antibodies directed against precisely located sequences in actin. A major contact area for glyceraldehyde-3-phosphate dehydrogenase was characterized in a region near residue 103. This interaction altered, by long-range conformational changes, the reactivity of antigenic epitopes in the C-terminal part of actin. The interface between actin and aldolase appeared to involve a sequence around residue 299 in the C-terminal region of actin. The interaction of phosphofructokinase, in contrast, modified the reactivity of all antibodies tested. Finally, the phosphagen kinases arginine kinase and creatine kinase showed no interaction with the microfilament.

Parameters affecting elastic properties of silica aerogels

Abstract: The Young's modulus of silica aerogels is measured, using the three point flexural technique. Various parameters have been investigated, such as the concentration of silicon compounds as well as the catalyting conditions used to develop the initial alcogel and the heat treatment performed to densify the material. The elastic behavior of aerogels depends on the conditions of gel preparation, and the Young's modulus is shown to obey the power dependence E ≃ ρ3.7. This scaling exponent is compared to the percolation model predictions. On the other hand, the elastic behavior of different sets of aerogels is related to the spatial arrangement of the particles pointed out by fractal features.

Functional sequences of the myosin head.

Abstract: Muscle contraction originates from the sliding of myosin filaments on actin filaments, the energy for which is supplied by the hydrolysis of adenosine-5-triphosphate (ATP) by myosin. The nucleotide first binds to the acto-myosin complex in the myosin head (or subfragment-1), producing a conformational change which induces actin dissociation. The release of phosphate (Pi) then allows a return to the strong actin-myosin association, corresponding to the rigor state.

Silica xerogels containing a functional group at silicon

Abstract: Modified silica xerogels can be obtained from several trialkoxysilanes containing a specific group attached to silicon ZSi(OR′)3 (where R′ means an alkyl group). We report here the use of Z = H. In basic catalyzed conditions, the hydrolysis induces a release of H2 gas coming from SiH bonds. However, in neutral or acidic conditions it is possible to prevent the cleavage of SiH bonds. Thus, the dried gel contains SiH bonds as shown both by spectroscopy and chemical analysis. This new family of gels reacts with oxygen gas from the atmosphere. During heating, gels show a 7% weight increase in the temperature range 250°C to 600°C.

Cochlear neuroactive substances.

Abstract: We have reviewed the experiments done in our laboratory concerning various cochlear neuroactive substances. Data using chemical neuroanatomy and neurochemical techniques are described. They allow the identification and localization of neuroactive substances which could act as neurotransmitters and/ or neuromodulators at the different types of synapses in the organ of Corti. Three hypotheses are presented: (1) the inner hair cells use glutamate as a neurotransmitter, but in addition to its excitatory properties, glutamate may also be involved in pathophysiological events affecting afferent auditory dendrites; (2) subpopulations of both the lateral and medial olivocochlear efferent systems can be differentiated by the neuroactive substances they may use; (3) the base and the apex of the cochlea can be distinguished on the basis of neurochemical data.

Genetical variation and polyphyletic origin in Japanese Mus musculus.

Abstract: Previous reports of mitochondrial DNA variation in Japanese mice have revealed the occurrence of two components, a M. m. musculus mtDNA type in central Japan and a M. m. castaneus one at both northern and southern ends. In the present study, we explore the genetic composition of nuclear genes from Japanese wild mice. Protein electrophoresis at 16 polymorphic loci was used to characterise mice from 20 localities and to compare them with samples from the surrounding countries. The results revealed a predominant M. m. musculus nuclear gene component on the main Japanese Islands. A M. m. castaneus contribution was detectable in south Kyushu, but, interestingly, not evident in Northern Honshu were the castaneus mtDNA predominates. On the other hand, the mouse populations from Ogasawara (Chichi Islands) showed a threefold origin with a strong M. m. domesticus component, probably resulting from a very recent admixture. This clearcut example of reticulate evolution, which does not give rise to an homogeneous gene distribution, is however very different from the situation observed in the European hybrid zone. This raises questions concerning the mechanisms that either impede or favour gene admixture when differentiated gene pools are brought together.

Isolation and characterization of the G-actin-myosin head complex

Abstract: THE two main proteins involved in muscular contraction and cell motility, myosin and actin, possess the intrinsic property of being able to form filamentous structures1. This property poses a serious impediment to the study of their structures and interactions, and a considerable effort has thus been made to isolate their functional domains. The globular part of myosin, subfragment-1 (SI), which possesses ATPase and actin-binding sites as well as supporting the movement of actin filaments during in vitro assays, has been isolated2–4. But because SI is efficient in inducing actin polymerization5,6, as is myosin, it has not been possible to prepare and characterize a complex of SI with monomeric actin (G-actin). We have now used chromatographically purified proteins to show that only the SI isoenzyme carrying the Al light-chain subunit promotes actin polymerization. The other isoenzyme, SI (A2), carrying the A2 light-chain subunit, binds to actin, forming a tight complex of G-actin and SI in a 1:1 ratio. This new functional difference between myosin isoforms directly implicates the Al light-chain in myosin-induced actin polymerization. Additionally, this finding should lead to the purification of the stable G-actin–Sl complex needed to resolve the structure and to understand the molecular dynamics of the actin-myosin system.

Phenotypic Heterogeneity Studied by Immunohistochemistry and Aneuploidy in Non-Small Cell Lung Cancers

Abstract: Non-small cell lung cancers (non-SCLC) differ from small cell lung cancers (SCLC) by many clinical features and prognosis. However, recent studies suggest that lung cancer heterogeneity frequently leads to the association of SCLC and non-SCLC in the same tumor. This phenotypic heterogeneity can be analyzed by immunohistochemistry using monoclonal antibodies (Mab) raised against differentiation related antigens. It may have clinical relevance inasmuch as the diversification of malignant cells is a well-known factor of tumor progression and may be due to chromosomal instability because inappropriate gene expression leads to the formation of antigens unrelated to cell lineage. Chromosomal instability in cancer leads to aneuploidy detectable by cell DNA content analysis. In a prospective study, we analyzed, in parallel, the expression of neuroendocrine related antigens by immunohistochemistry and the cell DNA content in frozen specimens from 40 patients who underwent complete surgical resection of primary non-SCLC in an attempt ( a ) to characterize the phenotypic heterogeneity and ( b ) to determine whether this heterogeneity is correlated with aneuploidy and clinical staging. Three Mabs were used in association as a marker of neuroendocrine antigen expression (S-L 11.14, MOC-1, and NE-25); reactivity of these Mabs in 9 SCLC and 3 lung carcinoid tissue sections was used as positive control. All SCLC and 2 of 3 lung carcinoids tested were homogeneously positive with Mabs S-L 11.14, MOC-1, and NE-25; 13 of 40 non-SCLC were homogeneously positive and 11 additional specimens focally positive with Mabs S-L 11.14, MOC-1, and NE-25. The frequency of this abnormal phenotype was significantly higher in poorly differentiated squamous cell carcinomas (x2 10.08; P < 0.005), in clinical stage III non-SCLC (x2 5.93; P < 0.02), and in tumors involving mediastinal lymph nodes (x2 5; P < 0.03). The percentage of cells in the modal DNA of G-G1 phase was significantly lower in non-SCLC homogeneously positive with Mabs S-L 11.14, MOC-1, and NE-25 [27.4 ± 10.3% (SD)] in comparison with non-SCLC negative with these same Mabs [56.8 ± 21.3%; P < 0.01, Mann-Whitney U test]. We conclude that ( a ) mixed SCLC-non-SCLC differentiation is frequent and can be assessed by immunohistochemistry, ( b ) neuroendocrine differentiation in non-SCLC is mainly observed in poorly differentiated tumors and in advanced clinical stages, and that ( c ) this heterotopic phenotype is correlated with aneuploidy and has clinical implications.

Environmentally controlled phyletic evolution, blindness and extinction in Late Devonian tropidocoryphine trilobites

Abstract: The Middle and Upper Devonian carbonate succession of the Montagne Noire, Southern France has been precisely zoned by an unbroken sequence of conodont zones. Stratigraphic control is excellent, and has allowed evolutionary changes in tropidocoryphine trilobites, which occur throughout the succession, to be directly established. The tropidocoryphine had been a stable group for some 40 million years prior to the Middle Givetian. In their last few million years, however, they underwent rapid evolution and exhibit some striking transformations of the cephalon and the regression and virtual disappearance of the eye within a relatively short space of time. They also show a marked diminution in size, and lose their original relief so that the glabella becomes virtually flush with the surface. There are two separate lineages, both of which show eye-reduction and subsequent blindness. In the earlier lineage Tropidocoryphe (Longicoryphe)-Erbenicoryphe, the main features of the ancestral rootstock are conserved and the stable, strongly divergent anterior sutural pattern of the cephalon remains the same. The eye, however, became reduced to a slightly convex surface lacking lenses, only indistinctly defined. Erbenicorphe is confined to well-oxygenated facies, and probably lived as a shallow burrower within the sediment; it became extinct in the early Frasnian. The second lineage T. (Longicoryphe)-Pterocoryphe- Pteroparia shows a remarkable backward migration of the suture, which progressively swings posteriorly in successive species spanning four Frasnian conodont zones (about three million years duration). At the same time the eye progressively degenerates so that the last forms are blind. Sutural migration and eye reduction are not genetically linked, however; the unusual form of the cephalon and suture probably resulted from an adaptation to the euxinic environment in which Pterocoryphe originated. The loss of the eye resulted from the adoption of an endobenthic habit in Pteroparia which descended from the ancestral Pterocoryphe but which had migrated to an oxygenated facies. Eye-reduction is therefore parallel in the two lineages, but superimposed upon a different original cephalic configuration. The last Pteroparia became extinct when the late Frasnian fauna became overwhelmed by the first pulse of the ‘Kellwasser Event’ (probably an anoxic overturn). The evolving characters, through virtually all observed steps, show progressive unidirectional change without sudden breaks or saltations. Such unidirectional evolution is an adaptive response to constant long-lasting environmental influences. □Evolution, Devonian trilobites, France, gradualism, eye reduction.

High-molecular-mass proteins in haemodialysis-associated amyloidosis.

Abstract: 1. Protein constituents were determined in eight amyloid deposits from eight patients (five male and three female), 53 +/- 4 years of age, treated by haemodialysis for 9-20 years using only cuprophane membranes and operated for carpal tunnel syndrome. 2. Soluble proteins were removed by solubilization in phosphate-buffered saline after osmotic lysis. The proteins of the insoluble fibrils were characterized by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and two-dimensional gel electrophoresis, and immunologically identified by Western blotting. 3. In addition to beta 2-microglobulin, alpha 2-macroglobulin was identified in the fibrillar material. The presence of these two proteins in amyloid deposits was confirmed by immunofluorescent microscopic studies. 4. Our data confirm the presence of beta 2-microglobulin in haemodialysis-associated amyloidosis, and also suggest a possible role for alpha 2-microglobulin: it may protect beta 2-microglobulin from proteolytic digestion, leading to its accumulation in intact form and to amyloid fibril formation.

A human immunoglobulin IGHG3 allele (Gmb0,b1,c3,c5,u) with an IGHG4 converted region and three hinge exons.

Abstract: The five humanIGHG genes consist of three constant domain exons plus one of or four hinge exon(s), the quadruplicated hinge region being characteristic of theIGHG3 gene. Besides this structural difference, theIGHG genes are polymorphic, as demonstrated by the restriction fragment length polymorphism and, at the protein level, by the Gm allotypic antigenic determinants. In this paper, we report the sequence of theG3m(b0, b1, c3, c5, u) IGHG3 allele, typical of the Black African populations and of populations with Negroid admixture, found in a homozygous Tunisian designated as LAT. We demonstrate that thisG3 allele contains only three hinge exons instead of four (the probable result of an unequal crossing over) and thatIGHG3 genes with triplicated hinge exons (and therefore encoding shorter γ 3 chains) are present in healthy individuals from different populations. Moreover, we show that the LAT G3m (b0, b1, c3, c5, u) coding sequence results from the conversion, in the CH3 exon, of theG3m (b0, b1, b3, b4, b5, u, v) allele, the most frequentIGHG3 gene in the Negroid populations, by the homologous region of aIGHG4 gene. The structural features of theLAT IGHG3 allele, which are the lack of one hinge exon and its conversion by theIGHG4 gene, demonstrate that both crossing-over and gene conversion events occur in the evolution of the humanIGHG genes.

Recherche d'un materiel enzymatique adapte a l'hydrolyse des precurseurs d'arome de nature glycosidique du raisin

Abstract: 34 preparations enzymatiques commerciales de specifications variees ont ete etudiees : 5 d'entre elles, les plus efficaces pour hydrolyser les glycosides naturels du raisin, ont ete retenues pour des etudes complementaires. Ces preparations donnent des proportions relatives en differents terpenols variables a partir d'un meme extrait glycosidique naturel : ainsi, certaines preparations liberent principalement du linalol, d'autres du geraniol. Elles presentent toutes des activites β-D-glucopyranosidase, α-L-rhamnopyranosidase et α-L-arabinofuranosidase : leur inhibition par le glucose et l'ethanol varient selon la preparation. C'est l'hemicellulase REG2 qui presente les activites glycosidases les plus importantes, avec une grande resistance thermique et une activite interessante au pH des mouts et des vins. De plus, elle presente une activite α-L-arabinopyranosidase douee d'une remarquable resistance en milieu acide

Symmetric Kinematic Formulation and Non-Master/Slave Coordinated Control of Two Arm Robots

Abstract: ロボットが両手でひとつの対象物を操作する作業について, 静力学および運動学的観点より理論解析し, 協調動作を記述するための作業座標, およびその座標系における一般化力, 速度, 位置を首尾一貫した形で導く.そして, この結果に基づき, 左右の手にマスタ, スレーブの区別をつけない位置と力のハイブリッド協調制御系の構成を示す.理論解析では, 両手の運動を対象物中心で考えるために, 仮想ステッキという概念を新たに導入し, さらに一般化逆行列の理論を用いることにより, 両手の運動を対象物の絶対運動と内部運動に分解する.この分解された作業空間において, 協調動作を記述するための一般化力, 速度, 位置を導く.こうして導かれた一般化力, 速度, 位置は, 左右の手の関第力, 速度, 位置の対称な関数となっている.したがって, この座標を作業座標として構成されるハイブリッド制御系は, 左右の手にマスタ, スレーブの区別をつけることなく, 対象物の絶対運動および内部運動に対応した位置と力をそれぞれ独立に制御することが可能である.これより, 両手で対象物を保持して運ぶ作業が, 非マスタスレーブ方式により実現される.

Actions of excitatory amino acids on somatostatin release from cortical neurons in primary cultures.

Abstract: L-Glutamate, N-methyl-D-aspartic acid (NMDA), quisqualate, and kainate were found to increase endogenous somatostatin release from primary cultures of rat cortical neurons in a dose-dependent manner. The rank order of potency calculated from the dose-response curves was quisqualate greater than glutamate = NMDA greater than kainate, with EC50 values of 0.4, 20, and 40 microM, respectively. Alanine, glutamine, and glycine did not modify the release of somatostatin. The stimulation of somatostatin release elicited by L-glutamate was Ca2+ dependent, was decreased by Mg2+, and was blocked by DL-amino-5-phosphonovaleric acid (APV) and thienylphencyclidine (TCP), two specific antagonists of NMDA receptors. The NMDA stimulatory effect was strongly inhibited by APV in a competitive manner (IC50 = 50 microM) and by TCP in a noncompetitive manner (IC50 = 90 nM). The release of somatostatin induced by the excitatory amino acid agonists was not blocked by tetrodotoxin (1 microM), a result suggesting that tetrodotoxin-sensitive, sodium-dependent action potentials are not involved in the effect. Somatostatin release in response to NMDA was potentiated by glycine, but the inhibitory strychnine-sensitive glycine receptor did not appear to be involved. Our data suggest that glutamate exerts its stimulatory action on somatostatin release essentially through an NMDA receptor subtype.

Apical localization of the alpha subunit of GTP-binding protein Go in choroidal and ciliated ependymocytes.

Abstract: The presence of GTP-binding proteins (G proteins) has been studied in murine adult choroid plexuses and cultured fetal choroidal or hypothalamic ependymal cells by ADP-ribosylation catalyzed by Bordetella pertussis toxin (PTX) and by immunodetection using affinity-purified polyclonal antibodies against the alpha subunit of the Go protein (Go alpha), the major brain G protein. ADP-ribosylation with 32P-NAD and PTX of choroid plexus revealed an intense labeling at the 40 kDa level in addition to the known PTX-substrates at 41 kDa (Gi alpha) and 39 kDa (Go alpha). This 40 kDa substrate was also predominant in cultured ependymal cells. However, a positive immunoreactivity with the anti-Go alpha antibodies was detected at the level of the 39 kDa faster component, indicating the presence of Go alpha in both choroid plexuses and cultured ependymal cells. In thin frozen sections as well as in cultured cells, Go alpha was mainly immunolocalized at the apical pole of choroidal ependymocytes and in the kinocilia of ciliated ependymal cells. At the ultrastructural level, using gold immunoprobes, the immunoreactivity of a Go alpha-like protein was detected on the cytoplasmic face of the apical plasma membrane, coated pits and vesicles, and in the apical cytoplasmic matrix. In ciliated ependymal cells, the positive immunostaining displayed a dotted pattern at the surface of demembranated axonema of apical kinocilia. These findings strongly suggest that G proteins, especially Go, are involved in transducing chemical signals that modulate traffic and exchanges between cerebrospinal fluid and ependyma through the apical membrane of ependymocytes.

Comparative immunocytochemical study of the catecholaminergic and peptidergic afferent innervation to the dorsal vagal complex in rat and guinea pig.

Abstract: Light and electron microscopic immunocytochemistry was used to study the fine structural organization of the catecholaminergic and hypothalamic peptidergic innervation of the dorsal vagal complex of the medulla oblongata in the rat and guinea pig, the latter of which is known to lack central adrenergic neurons. In the rat, adrenergic fibers immunoreactive to phenylethanolamine-N-methyltransferase were concentrated in the dorsal motor nucleus of the vagus, where they established frequent symmetric synapses with dendrites and perikarya. On the other hand, the density of both oxytocin- and corticotropin-immunoreactive fibers appeared far lower in this nucleus than in the dorsal regions of the nucleus of the tractus solitarius, where they formed asymmetric synapses with small dendrites. In tissue treated for the dual labeling of two neuronal antigens, oxytocin- or corticotropin-reactive fibers were in close contact with adrenergic neurons in this dorsal medullary region. In the guinea pig, unlike the rat, the dorsal motor nucleus of the vagus contained large amounts of oxytocin- and corticotropin-reactive fibers, which formed many symmetric synapses with perikarya and dendrites. Taken together, these data suggest that the control of vagal preganglionic neurons by hypothalamic peptidergic neurons involves a bisynaptic neuronal pathway including adrenergic medullary neurons in the rat, whereas it is direct in the guinea pig, which lacks this adrenergic relay.