Iron absorption by excised grapevine roots

Excised roots from cuttings of Vitis vinifera cv. Verduzzo and of two rootstocks V. berlandieri x V. riparia 420 A and V. berlandieri x V. rupestris 1103 P. were tested for iron absorbed from FeEDTA solutions.Absorption rates decreased with time. At 0-2 °C iron absorption was only 50-60 % inhibited. BPDS, a specific chelator for Fe2+, inhibited almost completely absorption showing that reduction from Fe3+ to Fe2+ was needed both at 30 °C and at 0-2 °C. As pH increased from 5 to 8 absorption rate doubled for the cv. Verduzzo, increased about 5 times for 1103 P. and about 10 times for 420 A. Also the apparent kinetic constants of absorption were very different in the three grapevines: both Vmax and Km were in the order: 1103 P.> Verduzzo > 420 A. The presence of a conspicuous part of not exchangeable absorption apparently not dependent on metabolism and the possibility of characterizing cultivars and rootstocks as to nutritional requirements through ion absorption measurements are discussed.Absorption du fer par les racines coupées de la vigneDes racines coupées de x cv. Verduzzo et des porte-greffes V. berlandieri x V. riparia 420 A et V. berlandieri x V. rupestris 1103 P. ont été étudiées quant au fer absorbé de solutions de FeEDTA. La vitesse d'absorption diminue en fonction du temps. A 0-2 °C l'absorption est inhibée seulement de 50--60 %. Le BPDS, chélant spécifique du Fe2+, inhibe presque complètement l'absorption, ce qui démontre que la réduction Fe3+ -> Fe2+ est nécessaire à 0-2 °C ainsi qu'à 30 °C. Lorsque le pH passe de 5 à 8 la vitesse d'absorption se redouble pour le cv. Verduzzo, elle augmente d'à peu près cinq fois pour le 1103 P. et d'environ dix fois pour le 420 A. Les constantes ciné tiques apparentes de l'absorption sont aussi très différentes pour les trois vignes: Vmax  et Km sont toutes les deux de l'ordre de 1103 P. > Verduzzo > 420 A.On discute la présence d'une part remarquable· de l'absorption qui n'est pas échangeable et qui apparemment ne dépend pas du mé tabolisme, ainsi que la possibilité de caractériser les cultivars et les por te-greffes suivant leurs besoins en substances nutritives minérales au moyen de mesurages de l'absorption des ions

Mapping the Evolution of "Clusters": A Meta-analysis

This paper presents a meta-analysis of the “cluster literature” contained in scientific journals from 1969 to 2007. Thanks to an original database we study the evolution of a stream of literature which focuses on a research object which is both a theoretical puzzle and an empirical widespread evidence. We identify different growth stages, from take-off to development and maturity. We test the existence of a life-cycle within the authorships and we discover the existence of a substitutability relation between different collaborative behaviours. We study the relationships between a “spatial” and an “industrial” approach within the textual corpus of cluster literature and we show the existence of a “predatory” interaction. We detect the relevance of clustering behaviours in the location of authors working on clusters and in measuring the influence of geographical distance in co-authorship. We measure the extent of a convergence process of the vocabulary of scientists working on clusters.Cluster, Life-Cycle, Cluster Literature, Textual Analysis, Agglomeration, Co-Authorship

Extraction and preliminary characterization of microsomal (Mg2+ + K+)-ATPase activity of grapevine roots

The microsomal fraction extracted from grapevine roots obtained from woody cuttings possesses Mg2+-dependent, monovalent cation-stimulated ATPase activity. Addition of BSA, PVPP, choline-CI, ethanolamine, glycerol-1-P besides EDTA and DTT to the homogenizing medium as preservative compounds was required in order to achieve a successful isolation.When microsomes were extracted according to HODGES and LEONARD (1974) by homogenizing root tissue in the presence of EDTA and DTT, the enzyme activity exhibited inhibition by Mg2+ only partially relieved by K+, and properties of acid phosphatase rather than ATPase.Cation-stimulated ATPase of microsomes protected during homogenization was further characterized and it showed optimum activity at pH 7.0 in the presence of Mg2+ plus K+ . It was specific as a triphosphatase and Mg2+, rather than other divalent cations, was preferred as a cofactor. As monovalent stimulating cation, only NH4+ could substitute for K+ with equivalent efficiency. The kinetics of K+ stimulation showed a biphasic pattern.Biochemical bases of ion uptake by grapevine seem to be similar to those clarified for annual plants

Clustering dynamics and the location of high-tech firms

The location of productive activities and the emergence of clustering dynamics has been an important research topic since the early works of Weber (1929) and Marshall (1920 and 1921). This thesis aims at relating the processes of firms' location decision and the development of high-tech clusters within an encompassing theoretical and empirical framework. The thesis shows the empirical relevance of the clustering of high-tech sectors and highlights the importance of the issue through the construction and use of an original database on the location of high-tech establishments and employment (at two different geographical levels) in four major industrialised countries. It also contains a critical review of a number of different streams of theoretical and empirical literature which are directly connected, or which have been explicitly put in connection by the author, with the topic of study. In the thesis we develop a composite modelling framework for analysing firms' location decisions and the growth of high-tech clusters, and we empirically test a number of crucial hypotheses in order to draw some guidelines for economic policy. The models presented in the theoretical chapter derive from two different streams of literature. The first derives from the analysis of population ecology, the second from the theory of innovation diffusion. These modelling frameworks have stressed the existence of a critical mass and a maximum dimension of the cluster and their effects on the early and late phases of development within the "life cycle" of a cluster. They also highlighted the role of rank, stock, order and epidemics effects in the location decision of an individual firm which has to decide whether to locate into a developing cluster. The empirical evidence presented in the thesis has focused on the crucial elements of the location process by verifying the empirical relevance of different locational factors, has stressed the relative importance of agglomeration versus scale economies in determining the industrial specialisation of an area, and has measured the competitive effects which arise between the development of different clusters and the synergistic effects which are generated within the cluster. Finally the thesis presents empirical evidence which shows that local competition and industrial specialisation are the key elements for the success of an industrial cluster. A final chapter extracts some crucial policy conclusions on the role of entry versus growth policies, on the different development path that an industrial cluster may follow depending on the excludability condition, presents an original taxonomy of specific policies, applies some of these findings to a brief survey of the phenomenon of science parks and finally produces a series of guidelines for policy makers. The conclusion summarises the results obtained in the thesis and present a brief agenda for future research

Special issue on the 13th international conference on computational management science

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SERPINB3 delays glomerulonephritis and attenuates the lupus-like disease in lupus murine models by inducing a more tolerogenic immune phenotype

Objective: To explore the effects of SERPINB3 administration in murine lupus models with a focus on lupus-like nephritis. Methods: 40 NZB/W F1 mice were subdivided into 4 groups and intraperitoneally injected with recombinant SERPINB3 (7.5 \u3bcg/0.1 mL or 15 \u3bcg/0.1 mL) or PBS (0.1 mL) before (group 1 and 2) or after (group 3 and 4) the development of proteinuria ( 65100 mg/dl). Two additional mice groups were provided by including 20 MRL/lpr mice which were prophylactically injected with SERPINB3 (10 mice, group 5) or PBS (10 mice, group 6). Time of occurrence and levels of anti-dsDNA and anti-C1q antibodies, proteinuria and serum creatinine, overall- and proteinuria-free survival were assessed in mice followed up to natural death. Histological analysis was performed in kidneys of both lupus models. The Th17:Treg cell ratio was assessed by flow-cytometry in splenocytes of treated and untreated MRL/lpr mice. Statistical analysis was performed using non parametric tests and Kaplan-Meier curves, when indicated. Results: Autoantibody levels and proteinuria were significantly decreased and time of occurrence significantly delayed in SERPINB3-treated mice vs. controls. In agreement with these findings, proteinuria-free and overall survival were significantly improved in SERPINB3-treated groups vs. controls. Histological analysis demonstrated a lower prevalence of severe tubular lesions in kidneys of group 5 vs. group 6. SERPINB3-treated mice showed an overall trend toward a reduced prevalence of severe lesions in both strains. Th17:Treg ratio was significantly decreased in splenocytes of MRL/lpr mice treated with SERPINB3, compared to untreated control mice. Conclusions: SERPINB3 significantly improves disease course and delays the onset of severe glomerulonephritis in lupus-prone mice, possibly inducing a more tolerogenic immune phenotype

Characterization of a potassium-stimulated ATPase in membrane fraction isolated from roots of grapevine seedlings

A microsomal fraction possessing Mg2+-dependent and K+-stimulated ATPase activity was extracted by differential centrifugation from roots of grape seedlings (Vitis vinifera L. cv. Verduzzo).Roots yield from grape seeds was stimulated by means of GA3 and further improved by treatments able to control microbial contamination.The biochemical characteristics of ATPase activity were studied and compared with those previously reported for roots produced by grape woody cuttings.The presence of choline-Cl, ethanolamine and glycerol-1-P in addition to BSA, EDTA, PVPP and DTT in the homogenizing medium was obligatory in order to record the K+-stimulated component of activity.The enzyme was activated by Mg2+, further stimulated by monovalent ions and showed strong preference for ATP as the substrate and optimum pH at 6.5 in the presence of both Mg2+ and K+. The effect of different monovalent ions followed a sequence similar to that found in cereal roots preparations, but very different with respect to that recorded for preparations from roots of grape woody cuttings.K+-ATPase activity was inhibited by vanadate and DES whereas molybdate and azide had no or scarce effect . ATPase activity showed a simple Michaelis-Menten saturation with increasing ATP: Mg concentration, and a complex pattern of possible negative cooperativity for K+ stimulation.Microsomes fractionated using sucrose density gradient showed enrichment in plasmalemma vesicles at 1.10-1,15 g ml-1 density.This parameter differentiates this fraction from similar preparations containing plasmalemma ATPase obtained from roots of various annual plants