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L’objectif de ce travail est de compléter la caractérisation morphologique des civelles entrant dans l’estuaire de la Gironde par un paramètre physiologique, le taux d’hormone de croissance. Le flux d’arrivée a été suivi lors de la saison 1997 – 1998. 303 civelles au stade Vb ont été capturées et analysées individuellement. La longueur et la masse des individus diminuent en février, le facteur de condition seulement en mars. Le taux moyen d’hormone de croissance passe de 6 ng/hypophyse en moyenne en décembre à 16 ng/hypophyse en février et mars pour atteindre 20 ng/hypophyse en avril et mai. L’hypothèse la plus plausible est que cette augmentation du taux d’hormone traduise une détresse physiologique de plus en plus importante des animaux qui arrivent.

L'argenture est une transformation complexe qui fait passer les anguilles de la phase de croissance juvénile, sédentaire (stade jaune) à la phase de migration d'avalaison (stade argenté), étape initiale de la migration de reproduction océanique. Cette étude a été réalisée de façon comparative sur des lots d'anguilles femelles sédentaires ou d'avalaison, de taille supérieure à 45 cm, capturées en milieu naturel. Nous avons cherché à définir des critères de l'argenture en associant, pour la première fois, des paramètres endocriniens à des paramètres anatomiques. Les paramètres anatomiques analysés comprennent des caractères externes (poids et longueur du corps, index oculaire, IO) et internes (rapport gonadosomatique, RGS et rapport tractus digestif-somatique, RTDS) et les paramètres endocriniens incluent des hormones impliquées dans la métamorphose (hormones thyroïdiennes, T4 et T3 ) , la croissance (hormone de croissance, GH) et la reproduction (hormone gonadotrope, GtH). Chez les anguilles sédentaires, on observe un développement progressif des ovaires, corrélé à la croissance corporelle. L'augmentation du RGS s'accentue chez les anguilles d'avalaison (x 2,85), une valeur seuil ≥ 1,4 % caractérisant le stade argenté. L'agrandissement de l'oeil est également un phénomène progressif, initié dès le stade jaune et corrélé au RGS. Comme le RGS, l'accroissement de NO s'accentue chez les anguilles d'avalaison (x 2), une valeur seuil ≥ 8 pouvant être proposée comme critère externe d'argenture. La régression du tractus digestif n'est pas initiée au stade jaune, et survient seulement à l'argenture (x 0,26), avec une valeur seuil ≤ 1,5 % caractérisant le stade argenté. Parmi les paramètres endocriniens étudiés, seule la teneur hypophysaire en GtH permet de caractériser l'argenture. La teneur en GtH s'élève progressivement au cours du stade jaune, de façon corrélée avec le RGS, puis s'accroît fortement à l'argenture (x 25), une valeur seuil ≥ 15 ng/hypophyse permettant de caractériser le stade argenté. La teneur hypophysaire en GH augmente au cours du stade jaune de façon corrélée avec la longueur du corps. La teneur en GH baisse à l'argenture (x 0,5), mais le recoupement des valeurs individuelles ne permet pas d'utiliser ce critère. Le taux circulant d'hormone thyroïdienne T4augmente à l'argenture (x 1,38) mais avec un large recoupement des valeurs individuelles. Le taux de T3ne varie pas à l'argenture. En conclusion, l'argenture inclut des transformations multiples, caractéristiques aussi bien de la métamorphose (augmentation de T4) , de l'initiation de la puberté (augmentations du RGS et de GtH), du jeûne (diminution du RTDS) et de l'arrêt de croissance (diminution de GH). Certains paramètres anatomiques (IO, RGS, RTDS), et endocriniens (GtH), qui présentent très peu de recoupement dans les valeurs individuelles entre les stades jaune et argenté, sont utilisables comme critères de l'argenture.

Purpose – The purpose of this paper is to investigate the lateral forces during the fall of a magnet in a conducting pipe, when the direction of magnetization of the magnet is fixed. If the direction of magnetization is not parallel to the axis of the pipe, lateral forces occur and a decentration of the magnet happens. Design/methodology/approach – The problem is studied numerically, with a T - h 3D FE formulation well-suited for the problem. Computational results are compared with experimental results. Findings – The physical model is given and the main force coefficients analyzed. The lateral forces and the decentration phenomenon are studied as a function of the main parameters (thickness and radius of the pipe). Originality/value – The direction of magnetization is a key parameter to analyze the dynamics of a magnet motion inside a conducting pipe, when the radii of the pipe and the magnet are not so close. This analysis with a fixed direction of magnetization allows one to quantify the lateral forces and the decentration, and is a first step to understand the complete motion which includes the rotation which can be linked to the decentration. [ABSTRACT FROM AUTHOR]

Atomic force microscopy (AFM) combined with surface pressure-area isotherms were used to probe the interfacial behavior of phospholipid monolayers following penetration of surfactin, a cyclic lipopeptide produced by Bacillus subtilisstrains. Prior to penetration experiments, interfacial behavior of different surfactin molecules (cyclic surfactins with three different aliphatic chain lengthsS13, S14, and S15and a linear surfactin obtained by chemical cleavage of the cycle of the surfactin S15) has been investigated. A more hydrophobic aliphatic chain induces greater surface-active properties of the lipopeptide. The opening of the peptide ring reduces the surface activity. The effect of phospholipid acyl chain length (dimyristoylphosphatidylcholine, dipalmitoylphosphatidylcholine- (DPPC), and distearoylphosphatidylcholine) and phospholipid polar head (DPPC, dipalmitoylphosphatidylethanolamine and dipalmitoylphosphatidylserine) on monolayer penetration properties of the surfactin S15 has been explored. Results showed that while the lipid monolayer thickness and the presence of electrostatic repulsions from the interfacial film do not significantly influence surfactin insertion, these parameters strongly modulate the ability of the surfactin to alter the nanoscale organization of the lipid films. We also probed the effect of surfactin structure (influence of the aliphatic chain length and of the cyclic structure of the peptide ring) on the behavior of DPPC monolayers. AFM images and isotherms showed that surfactin penetration is promoted by longer lipopeptide chain length and a cyclic polar head. This indicates that hydrophobic interactions are of main importance for the penetration power of surfactin molecules.

Hydrogeomorphic processes within alluvial river systems create, maintain and degrade riparian habitat. The dynamic interactions between water, sediment, aquatic–terrestrial landforms and biotic elements control the functional processes and biodiversity patterns within the riparian zone and, thus, contribute directly to their ecological integrity and societal value. Numerous researchers from different disciplines publish work on the physical, biological, economic and societal functions of the riparian zone within various physiographic areas. The present paper aims to review the hydrogeomorphic processes of unconfined alluvial channel–floodplain rivers within the temperate zone. These processes and their interactions with the biotic environment provide the basis for understanding the physical as well as the ecological functioning of fluvial hydrosystems. The review focuses mainly on the European context, but major advances in riparian research from other continents are also considered. Rehabilitation and management strategies for the riparian zone are summarized and recommendations for further research conclude this review. Copyright © 2005 John Wiley & Sons, Ltd.

The present purpose was to study the influence of the type of training sport practised (long distance running, sprinting, handball) on ratings of perceived exertion (RPE), estimation of time limit (ETL), and heart rate (HR) on running tests. It was hypothesised that these parameters would be related to the type of training sport practised. 31 trained women (10 endurance-trained runners, 10 sprinters, and 11 handball players) performed two exercises to exhaustion on an outdoor track. The first test was a graded run to estimate maximal aerobic speed (SMA), i.e., the minimal speed which elicited maximal oxygen uptake. The second test was a constant all-out run at speed delta 50 (SΔ50), which corresponded to the speed halfway between SMAand the speed at lactate threshold (SLT), to specify time to exhaustion at this intensity (TLIM). Sensations regarding RPE, ETL, and HR were recorded during these tests. SMA, SΔ50, and SLT, expressed in absolute values (km · hr.−1) were statistically significantly different between groups (p<.05) whereas TLIMwas not. The covariance analysis showed that endurance-trained runners perceived the exercise as lighter and presented lower HR than handball players and sprinters for a same running %SMA(p<.05). Moreover, endurance-trained runners felt that they could endure more than the other groups at a given %SMAor relative exhaustion time (%TLIM). These results mean that the type of training sport which has been performed may mediate perceptual responses and influence physiological parameters during exhausting exercises. These results are likely in part related to sport-specificity of the exercise mode used in tests. This point must be taken into consideration by physical trainers who have to prescribe exercise intensities during athletic seasons for different groups of athletes.

The regulation of growth hormone (GH) by thyroid hormones (THs) has been shown to present species variation. We investigated the regulation of GH in the eel, a representative of an ancient group of teleosts. In vivo administration of triiodothyronine (T(3)) or thyroxine (T(4)) significantly reduced pituitary and serum GH levels, as measured by homologous RIA. In order to investigate the ability of THs to regulate GH production directly at the pituitary level, we used a long-term, serum-free primary culture of eel pituitary cells. Both T(3) and T(4) inhibited GH release in a concentration-dependent manner, producing up to 50% inhibition at 10 nM, with an ED(50) of <0.2 nM, within the range of their physiological circulating levels. Other hormones also acting via the nuclear receptor superfamily, such as sex steroids (testosterone, estradiol and progesterone) and corticosteroid (cortisol), had no effect on GH release in vitro, underlining the specificity of the regulatory effect of THs on GH. Measurement of both GH release and cellular content for calculation of GH production in vitro indicated that THs not only inhibited GH release but also GH synthesis. Dot-blot assay of GH messenger RNA (mRNA) using an homologous eel cDNA probe showed a decrease in GH mRNA levels in cells cultured in the presence of T(3), as compared with control cells. This demonstrated that the inhibition of T(3) on GH synthesis was mediated by a decrease in GH mRNA steady state levels. In conclusion, we demonstrate inhibitory regulation of eel GH synthesis and release by THs, exerted directly at the pituitary level. These data contrast with the rat, where THs are known to have a stimulatory effect and suggest that the pattern observed here in an early vertebrate and also found in birds, reptiles and some mammals including humans, may represent an ancestral and more generalized vertebrate pattern of TH regulation of pituitary GH.

We propose the use of DNA microarray for the discrimination of homologous products after a single PCR amplification with consensus primers. The method was applied to Staphylococcus identification. The femAnucleotide sequences, which are phylogenetically conserved among the staphylococci, were first amplified using a consensus primer pair together with the mecAsequence, a molecular marker for methicillin resistance. Products were then identified on a glass array.The microarray contained five selective DNA capture probes for the simultaneous and differential identification of the five most clinically relevant staphylococcal species (S. aureus, S. epidermidis, S. haemolyticus, S. hominis, and S. saprophyticus), while a consensus capture probe could detect all femAsequences, allowing the identification of the genus Staphylococcus. The mecAsequencehybridized to a specific capture probe. The identification was univocal because only a single capture probe had to be present for each sequence to be identified. The hybridization and identification processes were completed in less than 2 h. Current results demonstrate that low-density microarrays are powerful multigenotypic post-PCR analyzers and could compete with conventional bacteria identification.

Development of microarrays has revolutionized gene expression analysis and molecular diagnosis through miniaturization and the multiparametric features. Critical factors affecting detection efficiency of targets hybridization on microarray are the design of capture probes, the way they are attached to the support, and the sensitivity of the detection method. Microarrays are currently detected in fluorescence using a sophisticated confocal laser-based scanner. In this work, we present a new colorimetric detection method which is intented to make the use of microarray a powerful procedure and a low-cost tool in research and clinical settings. The signal generated with this method results from the precipitation of silver onto nanogold particles bound to streptavidin, the latter being used for detecting biotinylated DNA. This colorimetric method has been compared to the Cy-3 fluorescence method. The detection limit of both methods was equivalent and corresponds to 1 amol of biotinylated DNA attached on an array. Scanning and data analysis of the array were obtained with a colorimetric-based workstation. Copyright 2001 Academic Press.

An adaptive meshing technique is proposed. For a given number of nodes, the method allows a better precision, with a better repartition of the position of the nodes. It is based on the analysis of the influence of the node position and edge connection on the functional of the problem.

Growth hormone-releasing hormone (GHRH) and pituitary adenylate cyclase-activating polypeptide (PACAP) belong to the same superfamily of regulatory neuropeptides and have both been characterized on the basis of their hypophysiotropic activities. This review describes the molecular evolution of the GHRH/PACAP gene family from urochordates to mammals and presents the hypothesis that the respective roles of GHRH and PACAP in the control of GH secretion are totally inverted in phylogenetically distant groups of vertebrates. In mammals, GHRH and PACAP originate from distinct precursors whereas, in all submammalian taxa investigated so far, including birds, amphibians and fish, a single precursor encompasses a GHRH-like peptide and PACAP. In mammals, GHRH-containing neurons are confined to the infundibular and dorsomedial nuclei of the hypothalamus while PACAP-producing neurons are widely distributed in hypothalamic and extrahypothalamic areas. In fish, both GHRH- and PACAP-immunoreactive neurons are restricted to the diencephalon and directly innervate the adenohypophysis. In mammals and birds, GHRH plays a predominant role in the control of GH secretion. In amphibians, both GHRH and PACAP are potent stimulators of GH release. In fish, PACAP strongly activates GH release whereas GHRH has little or no effect on GH secretion. The GHRH/PACAP family of peptides thus provides a unique model in which to investigate the structural and functional facets of evolution.

Sec7 domains catalyze the replacement of GDP by GTP on the G protein ADP-ribosylation factor 1 (myrARF1) by interacting with its switch I and II regions and by destabilizing, through a glutamic finger, the beta-phosphate of the bound GDP. The myristoylated N-terminal helix that allows myrARF1 to interact with membrane lipids in a GTP-dependent manner is located some distance from the Sec7 domain-binding region. However, these two regions are connected. Measuring the binding to liposomes of functional or abortive complexes between myrARF1 and the Sec7 domain of ARNO demonstrates that myrARF1, in complex with the Sec7 domain, adopts a high affinity state for membrane lipids, similar to that of the free GTP-bound form. This tight membrane attachment does not depend on the release of GDP induced by the Sec7 domain but is partially inhibited by the uncompetitive inhibitor brefeldin A. These results suggest that the conformational switch of the N-terminal helix of myrARF1 to the membrane-bound form is an early event in the nucleotide exchange pathway and is a prerequisite for a structural rearrangement at the myrARF1-GDP/Sec7 domain interface that allows the glutamic finger to expel GDP from myrARF1.

Cellular adhesion to fibronectin (FN) can be mediated by several sequences located in different portions of the molecule. In human FN, these are: (i) the bipartite RGDS domain containing the RGDS cell‐binding sequence functioning in synergy for full cellular adhesion with a second site (termed here the synergistic adhesion site) and (ii) the recently characterized CS1 and REDV adhesion sites within the alternatively‐spliced type III homology‐connecting segment. Using specific adhesive ligands and inhibitory probes, we have examined the role of each of these domains in the adhesion, spreading, and motility of avian neural crest cells in vitro. Both the RGDS domain and the CS1 adhesion site were found to promote attachment of neural crest cells, but only the RGDS domain supported their spreading. However, the RGDS sequence could mediate both attachment and spreading efficiently only when it was associated with the synergistic adhesion site. In migratory assays, it was found that both the RGDS domain and the CS1 site are required in association, each with functional specificity, to permit effective locomotion of neural crest cells. The REDV adhesion site was apparently not recognized by avian neural crest cells, presumably because this sequence is absent from chicken FN. Finally, it was found that recognition of both the RGDS domain and CS1 binding site by neural crest cells involved receptors belonging to the integrin family. From these results, we conclude that neural crest cells can interact with several binding sites of FN molecules, and use them for distinct functions. Our results also suggest the possibility of an instructive role for FN in the control of adhesive and migratory events during embryonic development.

Thyroid stimulating hormone (TSH) is a vertebrate pituitary heterodimeric hormone that stimulates the thyroid gland to produce the thyroid hormones, T3 and T4. We report here the cloning, by PCR on reverse-transcribed pituitary RNAs, of a 180 bp fragment of the cDNA encoding TSH β subunit in the turbot (Psetta maxima). The deduced amino acid sequence displayed 66 and 75% identity with the corresponding sequence from the European eel (Anguilla anguilla) and the rainbow trout (Oncorchyncus mykiss), respectively. This cDNA was then used as a probe for densitometric analysis of individual pituitary Northern blots. TSH β mRNA levels were quantified in turbot where circulating thyroid hormones were modified by dietary treatments or hormone supplementation. Recombinant rainbow trout growth hormone had no effect on circulating thyroid hormone levels or on pituitary TSH β mRNA level. In turbot fed heat-treated rapeseed meal, plasma T4 levels were lowered and TSH β mRNA increased more than two fold. In contrast, when turbot were fed a standard fish-meal supplemented with T3, circulating T3 levels were elevated and there was a dramatic decrease in TSH β mRNA level. It is concluded that both thyroid hormones are able to down-regulate TSH β mRNA level in vivo in the turbot. These results are discussed in the context of the evolution of the TH feed-back on TSH production.

The distribution of GABA-immunoreactivity was studied in the brain of the silver eel (Anguilla anguilla) by means of antibodies directed against GABA. Immunoreactive neuronal somata were distributed throughout the brain. Positive perikarya were detected in the internal cellular layer of the olfactory bulb, and in all divisions of the telencephalon, the highest density being observed along the midline. Numerous GABA-reactive cell bodies were found in the diencephalon, particularly in the preoptic and tuberal regions of the hypothalamus, and the dorsolateral, dorsomedial and ventromedial thalamic nuclei. In the optic tectum, the majority of GABApositive cell bodies were located in the periventricular layer. A number of immunolabelled cell bodies were observed in different tegmental structures, notably the torus semicircularis. In the cerebellum, the Purkinje cells were either very intensely or very weakly immunoreactive. In the rhombencephalon, reactive cell bodies were observed in the eminentia granularis, the valvula cerebellaris, the octavolateral nucleus, the lobus vagus and in the vagal and glossopharyngeal motor nuclei. Intensely immunoreactive axons and terminals were observed in the external granular layer and internal cellular layer of the olfactory bulb. In the telencephalon, the highest density of reactive fibres and boutons was found in the fields of the medial wall. Many immunolabelled fibres were seen in the medial and lateral forebrain bundles. In the diencephalon, intense labelling of fibres and terminals were observed in the nuclei situated close to the midline. In the optic tectum the highest density of reactive fibres was seen in the sfgs, the layer to which the retina projects massively. Finally, in the rhombencephalon the strongest labelling of neurites was observed in the nuclei of the raphé, the nucleus octavocellularis magnocellularis and the nuclei of the IXth and Xth cranial nerves. The GABAergic system of the eel, which is well developed, appears to be generally comparable to that described in tetrapod vertebrates.

Insulin-like growth factor (IGF)-I has been suggested as a potential signal linking growth and puberty in mammals. Using the juvenile European eel as a model, we employed a long-term, serum-free primary culture of pituitary cells to study the direct effect of IGF-I on gonadotrophin (GtH-II=LH) production. IGF-I increased both cell content and release of GtH-II in a time- and dose-dependent manner. IGF-I and IGF-II had similar potencies but insulin was 100-fold less effective, suggesting the implication of an IGF type 1 receptor. Other growth and metabolic factors, such as basic fibroblast growth factor and thyroid hormones, had no effect on GtH-II production. IGF-I did not significantly increase the number of GtH-II immunoreactive cells, indicating that its stimulatory effect on GtH-II production does not result from gonadotroph proliferation. Comparison of IGF-I and somatostatin (SRIH-14) effects showed that both factors inhibited growth hormone (GH) release but only IGF-I stimulated GtH-II production by eel pituitary cells. This indicates that the effect of IGF-I on gonadotrophs is not mediated by the reduction of GH released by somatotrophs into the culture medium. This study demonstrates a specific stimulatory effect of IGF-I on eel GtH-II production, played out directly at the pituitary level. These data obtained in a primitive teleost suggest that the role of IGF-I as a link between body growth and puberty may have been established early in the evolution of vertebrates.

Arno is a 47-kDa human protein recently identified as a guanine nucleotide exchange factor for ADP ribosylation factor 1 (ARF1) with a central Sec7 domain responsible for the exchange activity and a carboxyl-terminal pleckstrin homology (PH) domain (Chardin, P., Paris, S., Antonny, B., Robineau, S., Béraud-Dufour, S., Jackson, C. L., and Chabre, M. (1996) Nature 384, 481-484). Binding of the PH domain to phosphatidylinositol 4,5-bisphosphate (PIP2) greatly enhances Arno-mediated activation of myristoylated ARF1. We show here that in the absence of phospholipids, Arno promotes nucleotide exchange on [Delta17]ARF1, a soluble mutant of ARF1 lacking the first 17 amino acids. This reaction is unaffected by PIP2, which suggests that the PIP2-PH domain interaction does not directly regulate the catalytic activity of Arno but rather serves to recruit Arno to membranes. Arno catalyzes the release of GDP more efficiently than that of GTP from [Delta17]ARF1, and a stable complex between Arno Sec7 domain and nucleotide-free [Delta17]ARF1 can be isolated. In contrast to [Delta17]ARF1, full-length unmyristoylated ARF1 is not readily activated by Arno in solution. Its activation requires the presence of phospholipids and a reduction of ionic strength and Mg2+ concentration. PIP2 is strongly stimulatory, indicating that binding of Arno to phospholipids is involved, but in addition, electrostatic interactions between phospholipids and the amino-terminal portion of unmyristoylated ARF1GDP seem to be important. We conclude that efficient activation of full-length ARF1 by Arno requires a membrane surface and two distinct protein-phospholipid interactions: one between the PH domain of Arno and PIP2, and the other between amino-terminal cationic residues of ARF1 and anionic phospholipids. The latter interaction is normally induced by insertion of the amino-terminal myristate into the bilayer but can also be artificially facilitated by decreasing Mg2+ and salt concentrations.

The distribution of immunoreactive GnRH was studied in the brain and pituitary gland of normal and human chorionic gonadotrophin (hCG) injected silver eels. It was found that the general organization of GnRH systems in this species is similar to that reported in other teleosts. Cell bodies were present in the olfactory bulbs, ventral telencephalon, periventricular hypothalamus and dorsal tegmentum. No positive perikarya could be detected in the preoptic region. Only scarce fibers were observed in the proximal neurohypophysis. Treatment with hCG does not modify the distribution of GnRH but it increases the density of positive structures, in particular at the level of the pituitary. The results are discussed in relation with the present status of knowledge of the mechanisms underlying the blockage of sexual maturation in the European eel at the silver stage.

A 4-month-old infant was admitted with a monoblastic infiltration of the skin associated with osteosclerosis. Both lesions spontaneously disappeared within a few months, but 2 years later, a monoblastic leukemia occurred that was associated with marked skin erythema and myelofibrosis. Skin and bone marrow specimens showed a monoblastic infiltration with numerous intermingled mast cells of normal appearance. Whether myelofibrosis was a feature of a systemic mastocytosis or of the leukemic process is discussed in this case.

A rapid, automated instrumental procedure for distinguishing urine cultures containing greater than 10(5) organism per ml is described. The method is based upon the measurement of changes in impedance that take place as microorganisms alter the chemical composition of the medium. The time required to detect impedance change is inversely related to the initial concentration of microorganisms in the sample. By defining an impedance-positive culture as one that gives detectable impedance change within 2.6 h, 95.8% of 1,133 urine cultures tested were correctly classified as containing more than or fewer than 10(5) organisms per ml. Selection of a longer detection time decreases false negative results at the cost of increased false positive results. Impedance screening is compared with screening data reported in the literature using adenosine-5'-triphosphate detection, microcalorimetry, electrochemical measurements, and optical microscopy.

A conceptually simple and east-to-use technique is described that uses continuous impedance measurements for automated monitoring of microbial growth and metabolism. The method has been applied to a wide range of microorganisms. Optical clarity is not required. The sensitivity and reproducibility of the method are demonstrated. The mechanism whereby microbial growth alters the impedance of the medium is discussed, as well as potential applications of the method to clinical microbiology.

Migration of neural crest cells depends on direct, transient interactions between fibronectin molecules and their corresponding Arg-Gly-Asp integrin receptors. We have previously suggested that the moderate-activity interaction between integrin receptors and fibronectin may be critical for the transient association of the cells with their substratum. In order to test this hypothesis, we have examined the in vitro locomotory behavior of neural crest cells on substrata of differing apparent avidities for integrin receptors. As substrata, we used a variety of monoclonal and polyclonal antibodies to the integrin beta 1 subunit that were characterized for their respective relative apparent avidities for the receptor. Neural crest cells were able to migrate on these antibodies and exhibited an organization of substratum-adhesion sites and of cytoskeletal elements virtually identical to that observed on fibronectin, indicating that they can at least partially mimic the migration-promoting activity of fibronectin. However, the number of migrating cells as well as their morphology and their speed of locomotion varied significantly with both the concentration of the antibody substratum and its relative avidity for the receptor. Thus, on high-avidity monoclonal antibodies and on polyclonal divalent antibodies at high concentrations only a limited number of cells escaped from the neural tube, and the rate of their migration was reduced compared to that on fibronectin (23 +/− 5 microns h-1 versus 65 +/− 10 microns h-1). In addition, cells were unusually flattened and cohesive. Time-lapse videomicroscopy revealed that, on high-avidity substrata, neural crest cells were able to extend cell processes that adhered to the substratum, but showed a dramatically reduced capability of breaking pre-existing substratum contacts. In contrast, the same antibodies at low concentrations produced neural crest cell migration at rates very similar to those on fibronectin at the same concentrations. Low-avidity monoclonal antibodies and polyclonal monovalent antibodies at all concentrations tested permitted extensive migration of neural crest cells, which exhibited the same morphology and locomotory behavior as on fibronectin. These results indicate that both the avidity of receptors for the substratum and the number of receptors bound to the substratum are critical in regulating the locomotory behavior of neural crest cells in vitro, and therefore might help to regulate the directionality of migration and final localization pattern of neural crest cells in vivo.

In avian embryos, somites constitute the morphological unit of the metameric pattern. Somites are epithelia formed from a mesenchyme, the segmental plate, and are subsequently reorganized into dermatome, myotome, and sclerotome. In this study, we used somitogenesis as a basis to examine tissue remodeling during early vertebrate morphogenesis. Particular emphasis was put on the distribution and possible complementary roles of adhesion-promoting molecules, neural cell adhesion molecule (N-CAM), N-cadherin, fibronectin, and laminin. Both segmental plate and somitic cells exhibited in vitro calcium-dependent and calcium-independent systems of cell aggregation that could be inhibited respectively by anti-N-cadherin and anti-N-CAM antibodies. In vivo, the spatio-temporal expression of N-cadherin was closely associated with both the formation and local disruption of the somites. In contrast, changes in the prevalence of N-CAM did not strictly accompany the remodeling of the somitic epithelium into dermamyotome and sclerotome. It was also observed that fibronectin and laminin were reorganized secondarily in the extracellular spaces after CAM-mediated contacts were modulated. In an in vitro culture system of somites, N-cadherin was lost on individual cells released from somite explants and was reexpressed when these cells reached confluence and established intercellular contacts. In an assay of tissue dissociation in vitro, antibodies to N-cadherin or medium devoid of calcium strongly and reversibly dissociated explants of segmental plates and somites. Antibodies to N-CAM exhibited a smaller disrupting effect only on segmental plate explants. In contrast, antibodies to fibronectin and laminin did not perturb the cohesion of cells within the explants. These results emphasize the possible role of cell surface modulation of CAMs during the formation and remodeling of some transient embryonic epithelia. It is suggested that N-cadherin plays a major role in the control of tissue remodeling, a process in which N-CAM is also involved but to a lesser extent. The substratum adhesion molecules, fibronectin and laminin, do not appear to play a primary role in the regulation of these processes but may participate in cell positioning and in the stabilization of the epithelial structures.

Gonadotropin-releasing hormone (GnRH) is released episodically into the pituitary portal vessels and from hypothalamic tissue of male and female rats in vitro. Perifused primary cultures of rat hypothalamic neurons, as well as the GT1-1 GnRH neuronal cell line, spontaneously exhibited episodic GnRH secretion of comparable frequency to that observed with perifused hypothalami. Such pulsatile GnRH release from GT1 cells indicates that GnRH neurons generate rhythmic secretory activity in the absence of input from other cell types. In primary hypothalamic cultures, the frequency of GnRH pulses increased with the duration of culture. The spontaneous pulsatility in GnRH release was abolished in Ca(2+)-deficient medium and was markedly attenuated in the presence of nifedipine, an antagonist of voltage-sensitive Ca2+ channels. The basal intracellular Ca2+ level of perifused GT1-1 cells cultured on coverslips was also dose-dependently reduced by nifedipine. Conversely, depolarization with high K+ increased intracellular Ca2+ and GnRH release in an extracellular Ca(2+)-dependent and nifedipine-sensitive manner. The dihydropyridine Ca2+ channel agonist Bay K 8644 increased basal and K(+)-induced elevations of intracellular Ca2+ concentration and GnRH secretion. These findings demonstrate that pulsatile neuropeptide secretion is an intrinsic property of GnRH neuronal networks and is dependent on voltage-sensitive Ca2+ influx for its maintenance.

Le spectre clinique et anatomopathologique des hypophysites est large est complexe, dominé par les formes lymphocytaires et granulomateuses. L’apparition de nouvelles entités comme la plasmocytose à IgG4 vient étoffer cette classification des hypophysites. Nous rapportons ici un cas rare d’hypophysite à Ig G4.

La resistenza insulinica sembra essere il miglior indice di predizione dello sviluppo di diabete nei figli di pazienti con diabete di tipo 2, ma il meccanismo responsabile non è noto. Sono stati eseguiti studi con il clamp iperinsulinemico-euglicemico in combinazione con infusioni di (6,6-2H2)glucosio in figli sani, giovani, magri, insulino-resistenti di pazienti con diabete di tipo 2 ed in soggetti di controllo insulino-sensibili, paragonabili per età, altezza, peso ed attività fisica, allo scopo di determinare la sensibilità del fegato e del muscolo all’insulina. Sono stati effettuati studi di spettroscopia a risonanza magnetica protonica (1H) per misurare i lipidi all’interno della cellula muscolare e il contenuto intraepatico di trigliceridi. La velocità della lipolisi del grasso corporeo e sottocutaneo è stata determinata misurando il turnover del (2H5)glicerolo in combinazione con misure microdialitiche del rilascio di glicerolo dal grasso sottocutaneo. Sono stati eseguiti studi di spettroscopia a risonanza magnetica con 31P per valutare l’andamento dell’attività di fosforilazione ossidativa mitocondriale nel muscolo. La velocità di captazione del glucosio insulino-stimolata da parte del muscolo era approssimativamente ridotta del 60% nei soggetti insulino-resistenti rispetto ai soggetti di controllo insulino-sensibili (P<0.001) e si associava ad un aumento di circa l’80% del contenuto lipidico all’interno della miocellula (P=0.005). Tale aumento del contenuto lipidico dentro la cellula muscolare era molto verosimilmente da attribuire ad una disfunzione mitocondriale, come rispecchiato da una riduzione di circa il 30% della fosforilazione mitocondriale (P=0.01 in paragone con i controlli), dal momento che non vi erano differenze significative nell’ andamento sistemico o localizzato della lipolisi, né nelle concentrazioni plasmatiche di TNFa, interleuchina-6, resistina, adiponectina. Questi dati depongono a favore dell’ipotesi che la resistenza insulinica nel muscolo scheletrico della prole insulino-resistente di pazienti con diabete di tipo 2 si associa con una deregolazione del metabolismo degli acidi grassi all’interno della cellula muscolare, possibilmente a causa di un difetto ereditario nella fosforilazione ossidativa mitocondriale.

Floodplain development is associated with lateral accretion along stable channel geometry. Along shifting rivers, the floodplain sedimentation is more complex because of changes in channel position but also cutoff channel presence, which exhibit specific overflow patterns. In this contribution, the spatial and temporal variability of sedimentation rates in cutoff channel infill deposits is related to channel changes of a shifting gravel bed river (Ain River, France). The sedimentation rates estimated from dendrogeomorphic analysis are compared between and within 14 cutoff channel infills. Detailed analyses along a single channel infill are performed to assess changes in the sedimentation rates through time by analyzing activity profiles of the fallout radionuclides 137Cs and unsupported 210Pb. Sedimentation rates are also compared within the channel infills with rates in other plots located in the adjacent floodplain. Sedimentation rates range between 0.65 and 2.4 cm a−1over a period of 10 to 40 years. The data provide additional information on the role of distance from the bank, overbank flow frequency, and channel geometry in controlling the sedimentation rate. Channel infills, lower than adjacent floodplains, exhibit higher sedimentation rates and convey overbank sediment farther away within the floodplain. Additionally, channel degradation, aggradation, and bank erosion, which reduce or increase the distance between the main channel and the cutoff channel aquatic zone, affect local overbank flow magnitude and frequency and therefore sedimentation rates, thereby creating a complex mosaic of sedimentation zones within the floodplain and along the cutoff channel infills. Last, the dendrogeomorphic and 137Cs approaches are cross validated for estimating the sedimentation rate within a channel infill.