Mechanism of an epibiont burden: Crepidula fornicata increases byssus thread production by Mytilus edulis

Epibionts of mussels can have detrimental effects on their basibionts,such as reduced growth rates, lower fecundity, increased mortalityand an enhanced risk of dislodgement of the overgrown bivalvesdue to stronger hydrodynamic forces. In blue mussels Mytilusedulis, the epibiotic American slipper limpet Crepidula fornicatareduces growth and survival. In a field experiment we testedthe hypothesis that an enhanced byssus thread production withhigh energetic costs for the mussels due slipper limpet epibiontsis the underlying mechanism for the epibiont burden. Byssusthread production in overgrown mussels was twice as high asin unfouled M. edulis (11 ± 0.9 and 5.4 ± 0.6byssus threads/mussel/day, respectively). A control experimentrevealed intermediate byssus thread production (8.4 ±0.8 byssus threads/mussel/day) in mussels cleaned of C. fornicataat the beginning of the experiments, indicating that C. fornicatais responsible for the effects observed. We conclude that increasedbyssus production in fouled M. edulis is a functional responseto higher drag caused by epibionts and that it is associatedwith increased energy expenditure that reduces allocation ofresources for other processes such as growth, reproduction andsurvival. Such indirect effects of epibionts, mediated by anenhanced byssus production, may be widespread in byssus-producingbivalves, with important implications for their population dynamics. (Received 12 January 2006; accepted 21 November 2006)     

Defoliation and Leaf Age Influence on Ergot Alkaloids in Tall Fescue

A controlled environment experiment was conducted to determinethe influence of defoliation on the regrowth and developmentof two tall fescue (Festuca arundinacea Schreb.) host-endophyte(Neotyphodium coenophialum Morgan-Jones and Gams (Glenn, Bacon,Price and Hanlincomb. nov. ) associations (DN2 and DN11), knownto differ in morphology and alkaloid production capacity. Defoliationtreatments included an uncut control, and clipping to a 5- or10-cm residue height. In a separate experiment, leaf age effectswere determined on an uncut plant canopy. Ergot alkaloid concentrationwas greatest in pseudostem and least in harvested leaf. Non-infectedplants were devoid of alkaloid. Alkaloid production (expressedas a function of dry matter) and yield were greater in uncutthan clipped plants, and were greater in DN11 than DN2 plants.Alkaloid production increased with increasing N concentrationin both associations; however, the rate of production was influencedby concentration of non-structural carbohydrate. Leaf age influencedleaf mass and alkaloid concentration and yield. Oldest leaves(>6 weeks after appearance) of DN2 and DN11 had the lowestconcentrations of ergot alkaloid, while leaves that were 2 to4 weeks old had the greatest alkaloid concentration and yield(alkaloid concentrationxleaf mass). Repeated defoliation reducedthe production of alkaloids, but did so as a function of non-structuralcarbohydrate. Our data suggest that alkaloid production canbe modified by defoliation as well as by host-endophyte association. Neotyphodium coenophialum ; Festuca arundinacea ; N; non-structural carbohydrate     

Factors Influencing Seed Set in Triploid Musa spp. L. and Production of Euploid Hybrids

Seed set in triploid Musa spp. L. is very low due to high levelsof sterility. This makes cross breeding of plantain and bananadifficult. Nonetheless, several triploid plantain and bananacultivars produce seeds after hand pollination with diploidparents. This paper reports results about the pattern of seedvariation, success of in vitro germination and hybrid productionafter triploid-diploid crosses. Between-and within-clones differencesin seed set were observed. ABB cooking bananas had the highestrates of seed production followed by AAB French plantains. Plantainsproduced more diploid than tetraploid offsprings after triploid-diploidcrosses, which suggests that meiosis resulted in the productionof balanced haploid gametes (n = x) due to normal chromosomebehaviour between homologous genomes. Seed set variation withinclones was influenced by both the production of 2n (= 3x) gametesin the triploid parent and climatic factors. Indeed, seed production,embryo and seed germination success, and euploid and tetraploidhybrid production followed a pattern of seasonal variation reachinga peak in September. High frequency of seed with tetraploidembryos was obtained in the period from January to mid-March.The results demonstrate that production of desirable tetraploidswould be more efficient when hand pollinations are done underhigh temperature, high solar radiation and low relative humidity.These seem to be the most convenient conditions for relativelyhigh production of 2n eggs as compared to haploid gametes.Copyright1995, 1999 Academic Press Banana, fertility, embryo culture, Musa spp. AAA group, Musa spp. AAB group, Musa spp. ABB group, plantain, ploidy, seed set, 2n gametes     

Temporal variability in copepod fecundity during two different spring bloom periods in coastal waters off Plymouth (SW England)

The temporal variation in egg production of the planktonic copepodsCalanus helgolandicus, Temora longicornis and Pseudocalanuselongatus was studied during two different spring bloom periodsin 1989 and 1990 by weekly sampling at two permanent stationsin coastal waters off Plymouth (SW England). Copepod egg productionwas estimated in situ by incubating individual adult femalesin filtered seawater for 24 h (72 h until hatching for P.elongatus)at the field surface temperature. The relationship between copepodegg production rates and: (i) chlorophyll a concentration (totaland >10 µm size fraction), (ii) temperature and (iii)initial copepod gut pigment content was investigated. The springbloom periods were very different in both years, with the occurrenceof a Phaeocystis sp. bloom in 1990, which negatively affectedthe feeding and fecundity of copepods. Egg production ratesin spring 1989 were significantly correlated with chlorophylla concentration (particularly with the >10 µm fraction),field temperature and copepod gut pigment contents. In spring1990, egg production rates were also correlated with copepodgut pigment contents, but no significant correlations were obtainedwith temperature or with chlorophyll a concentration, as a consequenceof the lower egg production rates obtained during the Phaeocystissp. dominance period. These results show that food availabilityis the factor which mainly affects the fecundity of neriticcopepods in short time periods.     

Environmental and Chemical Control of Vegetative Dormant Bud Production in Hydrilla verticillata

Bud production was investigated using algal-free cultures ofthe aquatic weed, Hydrilla verticillata. Vegetative dormantbud production in hydrilla is stimulated by a shortened photoperiodand is not temperature-dependent between 15 and 30 C. The phytochromesystem appears to be involved in this process and ABA stimulatesbud production. Artificial illumination throughout the nightprevented dormant bud production. Ethylene, applied as ethephon,reduced bud production in greenhouse cultures by 80 per centwhen applied at a level of 0.1 mgl^–1 ethephon at 2-d intervals. Hydrilla verticillata, aquatic plants, dormant buds, ethephon, ethylene, abscisic acid     

Ethylene Production by the Kudzu Strains of Pseudomonas syringae pv. phaseolicola Causing Halo Blight in Pueraria lobata (Willd) Ohwi

Significant amounts of ethylene was produced by Pseudomonassolanacearum (all strains), P. syringae pv. phaseolicola (Kudzustrains isolated from Pueraria lobata) and Erwinia rhapontici(2 strains out of 22) out of 24 species, 3 subspecies and 38pathovars of plant pathogenic bacteria tested in yeast extract-peptonebroth. The bean strains of P. syringae pv. phaseolicola causinghalo blight in kindney bean plants did not produce ethylene.The Kudzu strains produced ethylene at a rate of 7 to 100?10^–9nl cell^–1 h^–1, which was 500 to 1,000 times higherthan that of P. solanacearum and several times higher than thatof Penicillium digitatum, the most potent ethylene producerknown among microorganisms. The presence of living cells was essential for ethylene productionby the Kudzu strains. The bacterium effectively produced ethylenefrom amino acids such as glutamate, aspartate and their amides.Although glucose and succinate were also good substrates forethylene biosynthesis, the rate of ethylene production was significantlysmaller than that with glutamate. Methionine, which is knownas the precursor of ethylene in plants, had no effect on ethyleneproduction by the bacterium. 1-Aminocyclopropane-1-carboxylicacid (ACC) also had no effect on ethylene production, and therewas not enough ACC in the bacterial cells to account for thehigh rate of ethylene production. Ethylene production from glutamatewas inhibited by n-propylgallate and EDTA, but not by aminoethoxyvinylglycine.These results indicate that ACC is not involved as an intermediatein the process of ethylene biosynthesis by the bacterium, suggestingthe presence of a pathway different from that of plant tissues. (Received September 4, 1984; Accepted October 27, 1984)     

Seasonal Production of Secondary Phloem in the Twigs of Certain Tropical Timber Trees

Secondary phloem production in four deciduous (Albizzia lebbeck,Dalbergia sissoo, Tectona grandis and Terminalia crenulata)and three evergreen plants (Calophyllum inophyllum, Mangiferaindica and Morinda tinctoria) is briefly described. The totalduration of phloem production for each year was worked out forall these plants. In three of the four deciduous trees therewere two instalments of phloem production in correspondencewith the presence of two flushes of cambial activity while inTectona grandis and in all the three evergreen trees there wasonly one instalment. The time of initiation and cessation ofphloem tissue production was found to be variable in the differentplants studied. Periodicity in the production of different componentsof phloem tissue as well as the difference in the dimensionsof the different phloic elements produced during each flushof cambial activity resulted in detectable growth increments(or ‘rings’) within the phloem. There was a distinctshortening of the different phloem elements during the approachof dormancy/least activity. Conspicuous changes were found inthe ergastic contents of phloem parenchyma and ray cells adjacentto the cambial zone during the initiation of cambial activityand during the approach of dormancy/least activity. Seasonal growth, secondary phloem, deciduous and evergreen trees, cambial activity     

Mechanical Stress Elicits Nitric Oxide Formation and DNA Fragmentation in Arabidopsis thaliana

The effect of mechanical stress (centrifugation) on the inductionof nitric oxide (NO) formation and DNA fragmentation was investigatedin leaf cells of Arabidopsis thaliana. Centrifuged and non-centrifugedleaves from wild-type and nitrate reductase (NR)nia1, nia2 doublemutant, defective in the assimilation of nitrate, were labelledwith 4,5-diaminofluorescein diacetate (DAF-2 DA) to visualizein vivo NO production. After these treatments, DNA fragmentationwas detected by the terminal deoxynucleotidyl transferase-mediateddUTP nick end in situ labelling (TUNEL) method. Exposure toan NO-releasing compound, sodium nitroprusside (SNP) mimickedthe cell response to centrifugation (20 g). The involvementof endogenous NO as a signal in mechanical stress and in DNAfragmentation was confirmed by inhibition of NO production usinga nitric oxide synthase (NOS) inhibitor viz. N^G-monomethyl-L -arginine (L -NMMA). These results indicate that NOS-likeactivity was present in A. thaliana leaves and was increasedby mechanical stress. The effect of leaf-wounding on nitricoxide production was identical to that of centrifugation. Experimentswith A. thaliana NR mutant also showed that NO bursts were inducedby mechanical and wounding stresses and that NO was not a by-productof NR activity. A positive and significant correlation betweenNO production and DNA fragmentation was recorded for both centrifugedand non-centrifuged cells. Our results suggest that factorsother than NO contribute to DNA damage and cell death, and furthermore,that an inducible form of NOS is present in A. thaliana. Copyright2001 Annals of Botany Company Arabidopsis thaliana, cell death, DNA fragmentation, NO, plant stress, wounding     

Spatial Distribution of Ethylene Production by Individual Needles Along a Shoot ofPinus sylvestrisL.: Relationship with Peroxidase Activity

Spatial distribution of ethylene production by individual currentyear needles and the relationship with peroxidase activity wasstudied along a shoot of Scots pine (Pinus sylvestrisL.). Muchvariation in ethylene production between and within individualseedlings was found. There was a significant difference in meanintensity of ethylene production between orthostichies withinindividual seedlings. The capacity of individual needles toconvert 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylenedid not correlate with the basal rate of ethylene production.Mean ethylene production intensity by orthostichies correlatedpositively with mean peroxidase activity. A positive correlationbetween the intensity of ethylene production by individual needlesand detachment-induced peroxidase activity was found. The datasuggests that the rate of ethylene production by individualneedles may be directly related to their peroxidase activityand at least in part to their antioxidative capacity.Copyright1998 Annals of Botany Company Pinus sylvestris,pine, ethylene production, spatial distribution, individual needles, peroxidase, seasonal changes.     

Effect of UV-Irradiation on Total Protein and Nucleic Acids in Alternaria alternata and Fusarium solani

UV-A^* irradiation caused increases in total protein in Fusariumsolani, while its effect on Alternaria alternata was variable,and not as clear-cut as in F. solani. On the other hand, UV-Birradiation stimulated protein production in both fungi. UV-Airradiation showed an inhibitory effect on total DNA in bothfungi, while the effect on RNA was stimulatory in F. solanibut had no effect on A. alternata. Short fluences of UV-B inhibitedDNA production to some extent in both fungi, however longerfluences increased DNA content especially in F. solani. Theeffect of UV-B on RNA production was inhibitory in F. solanibut not in A. alternata. A. alternata is much more resistantto UV-irradiation than is F. solani, and increases in proteinin the former after UV-irradiation suggests that protein mayplay a part in protection against the harmful effect of UV-irradiation. UV-A, UV-B, fluence, protein, nucleic acids, Alternaria alternata, Fusarium solani     

Effect of Some Chelating Agents on Growth and Antheridial Production in Male Clones of Three Mosses Grown In Vitro

The present work deals with the effect of the chelating agentsethylenediamine-di(o-hydroxyphenylacetic acid) [EDDHA] ethylenediamine tetra acetic acid [EDTA] and their iron salts, salicylicacid and ferric citrate on growth and antheridial productionin male clones of three dioecious mosses: Barbula gregaria,Bryum coronatum and Philonotis turneriana., Barbula and Bryumdevelop antheridia in ordinary cultural conditions on basalmedium, whereas Philonotis remains sterile. In Barbula and BryumEDDHA and EDTA enhance the percentage of fertile gametophytes.Fe-EDDHA and Fe-EDTA increase antheridial production as wellas vegetative growth and the former effect is more striking.In this respect Fe-EDDHA is better than Fe-EDTA for Barbula,whereas the reverse is true for Bryum. Salicylic acid inhibitsantheridial production and vegetative growth. Ferric citrateenhances vegetative growth in all three mosses. In Barbula andBryum it also stimulates antheridial production, and this effectis more marked than that on vegetative growth. None of the chelatestested induces antheridia in Philonotis. antheridial production, Barbula gregaria (Mitt.) Jaeg., Bryum coronatum Schwaegr., Philonotis turneriana (Schwaegr.) Mitt., mosses, chelating agents, bryophyta     

Potential contributions of vertically migrating Rhizosolenia to nutrient cycling and new production in the open ocean

We present a numerical model of nutrient uptake and photosynthesisduring migrations of the marine diatom Rhizosolenia that wasdeveloped to estimate fluxes of carbon and nitrogen due to thesemigrations in the open ocean. The predicted specific rate ofincrease of Rhizosolenia was 0.11–0.15 day¹, whereas thetotal time for one migration cycle ranged between 3 and 5 days.Using published estimates of Rhizosolenia abundance, we estimatethat new primary production due to Rhizosolenia migrations rangesbetween 0.018 and 0.033 mmol N m^–2 day^–1. Thesevalues represent up to 17% of new production due to turbulentdiffusive fluxes of nitrate into the euphotic zone and are ofthe same order of magnitude as new production due to nitrogenfixation in tropical oceans. Large-scale contributions of Rhizosoleniato oceanic new production are limited by their relatively lowstanding crop. Variations in the formulation of losses withdepth greatly affected gross and net fluxes of carbon and nitrogen.Better characterization of losses of Rhizosolenia and improvedestimates of its abundance will help determine more accuratelythe contributions of Rhizosolenia to global biogeochemical cycles. ¹Present address: Department of Agricultural and EnvironmentalScience, The Queen's University of Belfast New forge Lane, BelfastBT95PX, UK     

NOX5 NAD(P)H oxidase regulates growth and apoptosis in DU 145 prostate cancer cells

Reactive oxygen species (ROS) appear to play an important role in regulating growth and survival of prostate cancer. However, the sources for ROS production in prostate cancer cells have not been determined. We report that ROS are generated by intact American Type Culture Collection DU 145 cells and by their membranes through a mechanism blocked by NAD(P)H oxidase inhibitors. ROS are critical for growth in these cells, because NAD(P)H oxidase inhibitors and antioxidants blocked proliferation. Components of the human phagocyte NAD(P)H oxidase, p22^phox and gp91^phox, as well as the Ca²⁺ concentration-responsive gp91^phox homolog NOX5 were demonstrated in DU 145 cells by RT-PCR and sequencing. Although the protein product for p22^phox was not detectable, both gp91^phox and NOX5 were identified throughout the cell by immunostaining and confocal microscopy and NOX5 immunostaining was enhanced in a perinuclear location, corresponding to enhanced ROS production adjacent to the nuclear membrane imaged by 2',7'-dichlorofluorescin diacetate oxidation. The calcium ionophore ionomycin dramatically stimulated ferricytochrome c reduction in cell media, further supporting the importance of NOX5 for ROS production. Antisense oligonucleotides for NOX5 inhibited ROS production and cell proliferation in DU 145 cells. In contrast, antisense oligonucleotides to p22^phox or gp91^phox did not impair cell growth. Inhibition of ROS generation with antioxidants or NAD(P)H oxidase inhibitors increased apoptosis in cells. These results indicate that ROS generated by the newly described NOX5 oxidase are essential for prostate cancer growth, possibly by providing trophic intracellular oxidant tone that retards programmed cell death. superoxide anion; diphenylene iodonium; p22^phox; gp91^phox; adenosine 3',5'-cyclic monophosphate response element; caspases     

Production of 2n Gametes in Diploid Subspecies of Dactylis glomerata L. 2. Occurrence and Frequency of 2n Eggs

Whereas polyploidy has been found in more than half the Gramineae,the occurrence of 2n gametes, a potentially major mechanismof polyploid production, has been rarely studied. In the presentwork, the frequency of 2n egg production in nine diploid (n= 2x = 14) subspecies of the polyploid complex Dactylis glomeratahas been estimated by determining the ploidy level of the progenyin 98 2X-4X crosses. The 2n egg origin of the 4X offspring wasverified using enzyme markers. The frequency of 2n egg productionin each subspecies was estimated from the number of 4X offspring,the number of florets in the seed plant and the fertility ofthe subspecies. The ploidy level of the progeny was determinedby chromosome counts or nuclear DNA quantification using flowcytometry. Plants producing 2n eggs were detected in 47% ofthe fertile crosses, involving eight subspecies. Variabilitywas related to individuals and not to subspecies. Average 2negg frequency was 0·49% for all crosses, and 1·53%for crosses where 2n egg production was detected. Individualfrequencies did not exceed 3·5%, with the exception of26% in one plant. Triploid block was higher and fertility, frequencyof high 2n gamete producers and average 2n gamete frequencywere lower in the 2X-4X crosses than in the opposite 4X-2X crossesinvolving the same plants, previously studied. Diplogynous anddiplandrous gamete production were not correlated with eachother. However, the widespread occurrence of plants producingboth kinds of 2n gametes in almost all the studied subspecies,as well as the presence of several individuals able to producehigh rates of 2n eggs or 2n pollen, support the hypothesis thattetraploids can be formed anywhere and anytime by sexual polyploidizationin diploid populations of Dactylis glomerata L. 2n eggs, polyploidy, Dactylis glomerata L., flow cytometry, sexual polyploidization     

Dry Weight Production and Partitioning inMedicago minimaandErodium cicutariumUnder Water Stress

Medicago minimaandErodium cicutariumare two naturalized annualspecies in extensive semi-arid, temperate rangelands of centralArgentina. A field study was conducted during 1989 and 1990to evaluate the effects of different levels of soil water availabilityon above- and below-ground dry weight production and partitioningin these species. Dry weight production byM. minimawas moresensitive to water stress than that byE. cicutarium. Althoughthe response was more marked inM. minima, both species allocateda larger proportion of total plant dry weight to fruits underwater stress than under irrigated conditions during early spring.Percentage allocation of total plant dry weight into reproductiveorgans in both species, and stems and peduncles inE. cicutarium,was correlated with total dry weight of these organs; this mightindicate a correlation between sink size and strength. Persistenceof both species in the local flora appears to be associatedwith their capacity to colonize open, degraded areas and growin association with native perennial grasses, as well as totolerate severe drought periods.Copyright 1998 Annals of BotanyCompany Medicago minima(L.) Grufb. var.minima,Erodium cicutarium(L.) L'Herit, water stress, dry matter production and partitioning.     

Pigment ingestion and egg production rates of the calanoid copepod Temora longicornisr. implications for gut pigment loss and omnivorous feeding

We examined the relationship between egg production rate (E)and pigment ingestion rate (I, from gut content corrected for33% loss) for adult female Temora longicornis in Long IslandSound on 47 occasions. Linear regression of E on I [both variablesexpressed in mass of nitrogen (N) female^–1 day^–1]was: E_N = 0.0016 + 0.770 x I_N. The slope, 0.77, is the apparentgross efficiency of egg production, equivalent to the grossgrowth efficiency (GGE) assuming that females partition allnitrogen for growth into egg production. Published work suggeststhat a GGE of 0.37 would be expected for herbivorous copepods.The discrepancy between the expected value of 0.37 and observedvalue of 0.77 could result from unquantified losses of gut pigmentor because T.longicomis ingested a significant amount of nitrogenby feeding as a carnivore. We suggest that if T.longicomis femalesderive all of their nitrogen for growth by feeding on phytoplankton,and if no correction for pigment loss is employed, then thegut pigment method underestimates pigment ingestion by no morethan a factor of two.     

Salicylic Acid Levels in Thermogenic and Non-Thermogenic Plants

The natural trigger for heat production in the thermogenic inflorescencesof Sauromatum guttatum Schott (voodoo lily) was recently identifiedas salicylic acid (SA), which induced heat production at levelsas low as 13 ng g f. wt^–1. Since then the levels of SAwere determined in other thermogenic and non-thermogenic plantspecies. In thermogenic inflorescences of five aroid species,and in male cones of at least four thermogenic cycads SA levelsduring heat production exceeded 1 µg g f. wt^–1.SA was not detected in the thermogenic flowers of a water lily,Victoria regia Lindl. (Nymphaeaceae), and Bactris major Jacq.(Palmae). Levels of salicylic acid varied substantially in thefloral parts of seven non-thermogenic species and in the leavesof 27 non-thermogenic species. Amorphophallus campanulatus Blume ex Decne, Arum italicum Mill., Arum dioscoridis Sibth. & Son., Philodendron selloum Koch, Monstera deliciosa Liebm., Encephalartosferox Bertol. f., Encephalartos hildebrandtii A. Br. & Bouché, Encephalartos gratus Prain, Dioon edule Lindl. cv. edule, Dioon edule Lindl. cv angustifolium, Sauromatum guttatum Schott, voodoo lily, Victoria regia Lindl., Bactris major Jack, salicylic acid, thermogenicity, heat production     

UV-B treated algae exhibiting different responses as a food source for Daphnia magna

The response of green algae Scenedesmus quadricauda and Selenastrumcapricornutum to different levels of UV-B radiation was studied.Daphnia magna, the next step in the food web, was fed with UV-Btreated algae. UV-B radiation induced the synthesis of UV absorbingsubstances and photosynthetic pigments, enhanced the level ofrespiratory potential and suppressed growth of the treated algae.Biomass production in S. quadricauda was higher than in S. capricornutum,but the production of photosynthetic pigments and relative amountsof UV absorbing substances as well as respiratory potentialwere more pronounced in S. capricornutum. A short-term feedingexperiment with D. magna showed that in general, females ingestedhigher numbers of cells of algae treated with a high UV-B dose,but the biomass of ingested algae did not differ significantly.The exception was S. capricornutum treated with a high UV-Bdose; a lower biomass was ingested, probably reflecting thesmaller UV-treated cells.     

Extraction of photosynthesis-irradiance parameters from phytoplankton production data: demonstration in various aquatic systems

A method is presented for extraction of the photosynthesis-responseparameters from profiles of phytoplankton production. The procedure,previously proposed but not tested, is implemented here in varioustypes of aquatic system and a protocol is established for itsuse. Values of daily primary production integrated over thephotic zone were estimated from in situ or simulated in situincubations in four coastal and open-ocean marine systems, andfrom photosynthesis-irradiance (P–E) curves in the afore-mentionedmarine systems, as well as in two freshwater systems. The slopeof the measured daily water-column production (normalised towater-column chlorophyll a biomass) plotted against the dailyincident irradiance was variable from system to system (0.09to 0.60), showing a broader range than previously reported values.Using an iterative procedure, we estimated the photosyntheticparameters from this linear relationship. Generally, estimatedvalues lie within the 95% confidence interval of the photosyntheticparameters obtained from the P–E curves, showing thatthe estimates agree well with measurements. The new method,based on the photophysiological response of the phytoplanktoncommunity, provides a way to enhance our ability to computeprimary production from remote sensing of ocean colour.     

Regulation of ET-1 biosynthesis in cerebral microvascular endothelial cells by vasoactive agents and PKC

Endothelin-1(ET-1) is the most potent vasoconstrictor agent known. ET-1 is elevatedin the cerebrospinal fluid following hemorrhage and brain injury andcan compromise cerebral microvascular homeostasis. The modulation ofET-1 production by cerebral microvascular endothelial cells and themechanism by which such changes take place are very important in ourunderstanding of the pathological roles of ET-1. In the present study,we investigated the effects of vasoconstrictor agents that can bereleased from hemolyzed blood, cAMP-dependent dilators, and the role ofprotein kinase C (PKC) in the regulation of ET-1 production by pigletcerebral microvascular endothelial cells in culture. ET-1 was measured by RIA. 1) Cerebral microvascularendothelial cells synthesize and release ET-1 into the media;2) 5-hydroxytryptamine (5-HT), lysophosphatidic acid (LPA), thromboxane analog U-46619, fetal bovineserum (20%), and phorbol 12-myristate 13-acetate significantly increase ET-1 production; 3) basaland vasoconstrictor agent-induced increases in ET-1 production byendothelial cells may be mediated via PKC;4) cAMP-dependent vasodilatorsattenuate the basal production of ET-1 by cerebral microvessels; and5) pretreatment of endothelial cellswith a higher concentration of LPA, U-46619, or 5-HT counterbalances the cAMP-dependent dilator agent-induced reduction in basal ET-1 production. Therefore, by-products of hemolyzed blood can stimulate theproduction of ET-1 by a PKC-mediated mechanism. cAMP-dependent dilatorscan attenuate the vasoconstrictor agent-induced elevation in ET-1production. These results suggest that cerebral microvascular homeostasis could be compromised by effects of interactions among vasoactive agents released during conditions injurious to the brain andthey may further the understanding of potential contributions ofhemolyzed blood clots to subarachnoid hemorrhage-induced vasospasm.