Spatio-temporal distribution of the microphytobenthic biomass in intertidal flats of Tagus Estuary (Portugal)

A study on spatio-temporal distribution of microphytobhethos in intertidal zones of Tagus Estuary was carried out from 1990 to 1992. Near Lisbon, Portugal, Tagus Estuary is a shallow mesotidal estuary, covering an area of 320 km². The intertidal area ranges from 20 to 40% off the total area and it is constituted mainly by mudflats. Intertidal flats are richly populated by microalgae, diatoms being the most important and ubiquitos group.Spatial variation of microphytobethos was studied in spring 1990, 21 different sites were sampled. Microphytobenthos biomass was evaluated as chlorophyll a content of the surface centimeter, ranging from 10 to 240 mg m^–2. A Principal Component Analysis showed that 62% of the total variability found in intertidal flats of Tagus estuary could be attributed to two major factors: sediment type and tidal height. A hierarchical grouping defined 3 major groups of similar stations, each one representing a different strata of the ecosystem.One station from each group was chosen for the study of the temporal variation. A sampling, rogram took place from April 1991 to April 1992, with fortnightly sampling, the Chl a ranged from 20–300 mg m^–2. No clear seasonal variation was found, and our results indicated that tidal height of sampledsite played an essential role in temporal biomass evolution, thus upper littoral sites were influenced by climatic parameters, whereas in lower sites action of tides mainly controlled microphytic biomass.

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Résumé Une étude sur l'hétérogénéité spatio-temporelle du microphytobenthos dans les sédiments intertidaux de l'Estuaire du Tage a été accompli de 1990 á 1992.L'Estuaire du Tage, prés de Lisbonne (Portugal) est un estuaire peu profond, mesotidal, avec une aire total de 320 km². L'aire intertidale est comprise entre 20 et 40% du total, et constituéé surtout par des vasiéres. Ces slikkes sont peuplées par une communauté assez riche de microalgues, ou les diatomées sont les plus abundantes.La variation spatialle du microphytobenthos était évalué au Printemps 1990, ou 21 différentes stations étaient échantillonnées. La biomasse était évalué par la concentration enchlorophylle a du premier centimétre de sédiment, qui a varié de 10 á 240 mg Chl a m^–2. Une Analyse en Composants Principales a montré que 62% de la variabilité de la biomasse était lié á deux facteurs: le sédiment et l'hauteur vis-á-vis la marée. Une classification hiérarchique des stations par similitude a établi 3 groupes principaux, représantantles différents strates de écecosytéme.Une station de chaque groupement a été choisie pour l'étude de la variation temporelle, qui s'est deroulé d'avril 1991 á avril 1992, avec des prélévements deux fois par mois. Les valeurs de Chl a obtenus vont de 20 á 300 mg m^–2. Les variations saisonniéres observées ne sont pas claires: nos résultats indiquent que l'hauteur de la station (m) joue un rôle essentiel dans l'évolution temporel de la biomasse, c'est á dire, la biomasse microalgal des sites du supra-littoral est influencié par les paramétres climatiques, tandis que dans l'infra-littoral c'est l'action des marées le facteur principal.

     

Vanadium derivatives act as growth factor — mimetic compounds upon differentiation and proliferation of osteoblast-like UMR106 cells

The effect of different vanadium compounds on proliferation and differentiation was examined in osteoblast-like UMR106 cells. Vanadate increased the cell growth in a biphasic manner, the higher doses inhibiting cell progression. Vanadyl stimulated cell proliferation in a dose-responsive manner. Similar to vanadate, pervanadate increased osteoblast-like cell proliferation in a biphasic manner but no inhibition of growth was observed. Vanadyl and pervanadate were stronger stimulators of cell growth than vanadate. Only vanadate was able to regulate the cell differentiation as measured by cell alkaline phosphatase activity. These results suggest that vanadium derivatives behave like growth factors on osteoblast-like cells and are potential pharmacological tools in the control of cell growth.     

Solution conformation and dynamics of a tetrasaccharide related to the LewisX antigen deduced by NMR relaxation measurements

¹H-NMR cross-relaxation rates and nonselectivelongitudinal relaxation times have been obtained at two magnetic fields (7.0and 11.8 T) and at a variety of temperatures for the branchedtetrasaccharide methyl3-O--N-acetyl-galactosaminyl--galactopyranosyl-(14)[3-O--fucosyl]-glucopyranoside (1), an inhibitor of astrocyte growth. Inaddition, ¹³C-NMR relaxation data have also been recorded atboth fields. The ¹H-NMR relaxation data have been interpretedusing different motional models to obtain proton–proton correlationtimes. The results indicate that the GalNAc and Fuc rings display moreextensive local motion than the two inner Glc and Gal moieties, since thosepresent significantly shorter local correlation times. The¹³C-NMR relaxation parameters have been interpreted in termsof the Lipari–Szabo model-free approach. Thus, order parameters andinternal motion correlation times have been deduced. As obtained for the¹H-NMR relaxation data, the two outer residues possess smallerorder parameters than the two inner rings. Internal correlation times are inthe order of 100 ps. The hydroxymethyl groups have also different behaviour,with the exocyclic carbon on the glucopyranoside unit showing the highestS². Molecular dynamics simulations using a solvated systemhave also been performed and internal motion correlation functions have beendeduced from these calculations. Order parameters and interproton distanceshave been compared to those inferred from the NMR measurements. The obtainedresults are in fair agreement with the experimental data.     

Ethanol Promotes Apoptosis in Cerebellar Granule Cells by Inhibiting the Trophic Effect of NMDA

Abstract: When primary cultures of cerebellar granule neurons are grown in a physiological concentration of KCl (5 m M ) they undergo apoptosis, which can be prevented by growing the cells in the presence of N -methyl- d -aspartate (NMDA). We now show that ethanol inhibits this trophic effect of NMDA, i.e., promotes apoptosis, and also inhibits the NMDA-induced increase in intracellular Ca²⁺ concentration in cells grown in 5 m M KCl. Both effects of ethanol show a similar concentration dependence and are reversed by a high concentration of glycine, the co-agonist at the NMDA receptor. The data suggest that the effect of ethanol on apoptosis is mediated, at least in part, by inhibition of NMDA receptor function. This effect of ethanol to increase apoptosis could contribute to the previously described in vivo sensitivity of the developing cerebellum to ethanol-induced damage.     

Cryptic coloration and choice of escape microhabitats by grasshoppers (Orthoptera: Acrididae)

Cryptic coloration is found in many Orthoptera, especially in Acrididae, showing a great variety of forms. In a grasshopper assemblage in southeastern Brazil, preferences for escape places were detected; grasshoppers tended to escape to backgrounds in which they seem to be more cryptic. Coloration was measured using the Simpson diversity index, to quantify 'aspect diversity' (diversity of colours and shapes of patches along the insect's body). A weak positive correlation was found between grasshoppers' aspect diversity and diversification in use of escape places (use of many backgrounds to escape). Grasshoppers with similar colour patterns tended to use the same structures (leaves, sandy soil, stones) to escape.     

Angiogenesis in bronchial circulatory system after unilateral pulmonary artery obstruction

Charan, Nirmal B., and Paula Carvalho. Angiogenesis inbronchial circulatory system after unilateral pulmonary artery obstruction. J. Appl. Physiol. 82(1):284-291, 1997.We studied the effects of left pulmonary artery(LPA) ligation on the bronchial circulatory system (BCS) by using asheep model. LPA was ligated in the newborn lambs soon after birth(n = 8), and when the sheep were ~3yr of age anatomic studies revealed marked angiogenesis in BCS.Bronchial blood flow and cardiac output were studied by placing flowprobes around the bronchial and pulmonary arteries in four adult sheep.After LPA ligation, bronchial blood flow increased from 35 ± 6 to134 ± 42 ml/min in ~3 wk (P < 0.05). We also studied gas-exchange functions of BCS ~3 yr after the ligation of LPA in newborn lambs (n = 4) and used a control group (n = 12)in which LPA was ligated acutely. In the left lung,O₂ uptake after acute ligation was16 ± 3 ml/min and was similar to the chronic model, whereasCO₂ output in the control group was 27 ± 3 ml/min compared with 79 ± 12 ml/min in the chronic preparation (P < 0.05).We conclude that LPA ligation causes marked angiogenesis in BCS that iscapable of performing some gas-exchange functions.

     

Organogenesis in Taxus brevifolia tissue cultures

Summary A method is described for multiple shoot and plantlet formation from zygotic embryos of Taxus brevifolia. Adventitious bud primordia were best induced by culturing zygotic embryos on 1/2B5 medium supplemented with 10 M BA for 14 days. Further vegetative buds were produced following subculture to half-strength McCown's basal salt medium containing 1.0% activated charcoal. Individual adventitious shoots were excised and approximately 5% of these formed roots. Rooting frequency was increased to 58% by a single treatment with ABT rooting powder. Vigorous growing Taxus brevifolia plants were established after transfer to plant growth medium.     

Cpn60 is exclusively localized into mitochondria of rat liver and embryonic Drosophila cells

Several reports have claimed that the mitochondrial chaperonin cpn60, or a close homolog, is also present in some other subcellular compartments of the eukaryotic cell. Immunoelectron microscopy studies, using a polyclonal serum against cpn60, revealed that the protein is exclusively localized within the mitochondria of rat liver and embryonic Drosophila cells (SL2). Furthermore, no cpn60 immunoreactive material could be found within the nucleus of SL2 cells subjected to a 1 h 37°C heat-shock treatment. In contrast to these findings, immunoelectron microscopy studies, using a cpn60 monoclonal antibody, revealed mitochondrial and extramitochondrial (plasma membrane, nucleus) immunoreactive material in rat liver cells. Surprisingly, the monoclonal antibody also reacted with fixed proteins of the mature red blood cell. The monoclonal antibody, as well as cpn60 polyclonal sera, only recognize mitochondrial cpn60 in Western blots of liver proteins. Furthermore, none of the cpn60 antibodies used in this study recognized blotted proteins from rat red blood cells. Therefore, we suggest that the reported extramitochondrial localization of cpn60 in metazoan cells may be due to cross-reactivity of some of cpn60 antibodies with conformational epitopes also present in distantly related cpn60 protein homologs that are preserved during fixation procedures of the cells. © 1995 Wiley-Liss, Inc.     

Susceptibility of heterochromatin to aphidicolin-induced chromosomal breakage

The distribution of aphidicolin-induced chromosomal lesions was analyzed to determine the relative breakage susceptibility of euchromatin and heterochromatin in the cactus mouse, Peromyscus eremicus. The observed breakage was tested against expected distributions corresponding to the karyotypic proportions of autosomal euchromatin, autosomal heterochromatin, X-chromosomal euchromatin, and X-chromosomal heterochromatin. The distribution of induced breakage was independent of sex but dependent on the individual. In all individuals, there was a highly significant (P0.0001) deficiency in the number of breaks observed as compared to expected in autosomal heterochromatin. Sparse observations in the X chromosome and the absence of breaks in the Y chromosome precluded valid statistical tests of the sex-chromosomal distribution of induced breakage. These data indicate that the autosomal heterochromatin of Peromyscus is resistant to aphidicolin-induced chromosomal breakage and argue against a simple relationship between late replication and a general mechanism for chromosomal fragility.