Ceramide in Rice Grain

A rice lamina inclination test that is simple and specific for brassinosteroids was used as a micro-quantitative bioassay for brassinolide 1 and its 6-keto congener, castasterone 2, in the concentration range of 5 x 10^–5 /ig/ml to 5 x 10^–3μg/ml, when uniform seedlings of the rice cultivars Arborio J-l and Nihonbare were selected. A phytohormone, indole-3-acetic acid (IAA), showed similar activity in this bioassay. Its lowest effective concentration, however, was 50 /ig/μl, about five orders of magnitude greater than that of brassinolide. Other phytohormones, abscisic acid (ABA) and the cytokinins kinetin and A⁶-benzyladenine, inhibited the lamina inclination of rice seedlings. The addition of a cytokinin reduced the promoting effect of brassinolide. Thus, the rice lamina inclination test can be used both as a micro-quantitative bioassay for brassinosteroids and as a method for detecting antibrassinolide compouds.     

The Polarographic Determination of Phosphate

A method is described for estimating polarographically the amountof phosphate in small volumes of liquid, where the phosphoruscontent lies between 0.5 and 10.5 µg. P/ml. with an errorof ± 0.2 µg. P/ml. even when chloride, nitrate,and sulphate are present in excess. The method is based on precipitationof uranyl phosphate from uranyl acetate and estimation of theuranyl ion left in solution. A comparison is made with the colorimetric method of Berenblumand Chain.     

Effects of Concentration and Time of Exposure on the Phytotoxicity of Linuron

When seedlings of lettuce and turnip were grown in nutrientsolutions containing different concentrations of linuron, theconcentration in the shoot at the time when toxicity symptomsappeared was related to the solution concentration. With lettuce,for example, symptoms were recorded after 7 d at 0.15 µg/mland the shoot concentration was 2.7 µg/g fresh wt. At0.06 µg/ml, symptoms appeared after 10 d and the shootconcentration was then 1.1 µg/g fresh wt. If grown fordifferent periods in solutions containing linuron and then transferredto fresh nutrient solutions containing no herbicide, turnipor lettuce seedlings which had accumulated 0.7–0.8 µglinuron/g fresh wt developed toxicity symptoms 4 to 6 d later.Seedlings were also treated with linuron after they had grownfor different periods in control nutrient solutions. The shootconcentrations attained before toxicity symptoms appeared werehigher in those seedlings which were larger when herbicide treatmentbegan. These results show that the herbicide concentration insolution, time of exposure, and age of seedling are interrelatedin determining linuron phytotoxicity.     

EFFECTS OF VARIOUS FACTORS ON THE INCREASE OF {alpha}-AMYLASE ACTIVITY IN RICE ENDOSPERM INDUCED BY GIBBERELLIN A3

The increase of -amylase activity in embryoless rice endosperminduced by the addition of gibberellin A₃ was examined undervarious conditions with an aim to establish a bioassay methodfor gibberellins. Sterilized embryoless rice endosperms were incubated in a testtube containing 0.2–1.0 ml of test solution for 4 daysat 30. -Amylase activity in the endosperm was determined bymeasuring digestion of added starch. The increase of amylaseactivity during the incubation was not affected by the additionof various vitamins, amino acids, organic acids, protease, sucrose,indoleacetic acid or kinetin. Helminthosporol, helminthosporicacid and sclerin (1–10 µg/ml) had weak promotingeffects. Under appropriate conditions, 10^–5 µg/mlof gibberellin A₃ could be detected. In double logarithmic plot,the increase in the enzyme activity was proportional to thegibberellin A₃ concentration in the range from 10^–5 to10^–2 µg/ml. (Received April 13, 1966; )     

Variation in nicotine consumption in inbred mice is not linked to orosensory ability

Genetic studies of nicotine addiction in mice have utilizedthe oral self-administration model. However, it is unclear ifstrain differences in nicotine consumption are influenced byvariation in bitter taste sensitivity. We measured both nicotineconsumption and nicotine brief-access licking behavior in severalcommonly used inbred strains of mice that were previously shownto differ in nicotine consumption. A/J (A), C57BL/6J (B6), andDBA/2J (D2) mice were given a 2-bottle choice test with a singleconcentration of nicotine (75 µg/ml; nicotine vs. water).Mice of these strains were also tested with a range of nicotineconcentrations (5–400 µg/ml) using a brief-accesstest, which measures orosensory response and minimizes postingestiveeffects. Although B6 mice consumed more 75-µg/ml nicotinethan A or D2 mice in the 2-bottle test, these strains did notdiffer in level of aversion to nicotine when tested with thebrief-access procedure. Strain differences in orosensory responseto nicotine were not found; yet, differences emerged duringthe 2-bottle tests. This study provides evidence that variationin intake level of nicotine is likely not due to differencesin taste or trigeminal sensitivity but likely due to postingestivefactors.     

Factors Inducing Successful Anhydrobiosis in the African Chironomid Polypedilum vanderplanki: Significance of the Larval Tubular Nest

The African chironomid Polypedilum vanderplanki exhibits anhydrobiosis,i.e., the larvae can survive complete desiccation. Recoveryrate and trehalose content were investigated in larvae desiccatedslowly or at a rate more than 3 times faster. Upon slow desiccation(evaporation rate 0.22 ml day^–1) larvae synthesized 38µg trehalose/individual before complete desiccation, andall of them recovered after rehydration, whereas larvae thatwere dehydrated quickly (evaporation rate 0.75 ml day^–1)accumulated only 6.8 µg trehalose/individual and noneof them revived after rehydration. In the pools that are theirnatural habitat P. vanderplanki larvae make tubes by incorporatingdetritus or soil with their sticky saliva. This tubular structureis a physical barrier not only to protect the larva from naturalenemies but also induces successful anhydrobiosis by reducingthe dehydration rate. When larvae were dehydrated with 100 µldistilled water (DW) in soil tubes, they accumulated 37 µgtrehalose/individual and more than half of them could reviveafter rehydration, whereas larvae without tubes accumulatedlower level of trehalose and none recovered after rehydration.     

Induction of apoptotic effects of anti-proliferative zeolite X from coal fly ash on cervical cancer (HeLa) cell lines

The synthesised zeolite X from coal fly ash showed significant cytotoxic activity in contradiction of HeLa cells (cervical cancer) in a concentration-dependent way at concentrations ranges from 200 µg to 0.781 µg/ml as shown by MTT assay and failed to cause cytotoxic effect in normal cells (Gh239). Cell cycle analysis exposed that zeolite X (10 and 15 µg/ml) endorses cell growth inhibition by inducing G2/M phase arrest in HeLa cells as observed using flow cytometry. The confocal microscopic results depicted increased early apoptotic related changes in HeLa cell lines induced by zeolite X at a dosage of 10, 15 and 20 µg/ml. Zeolite X at a dosage of 10, 15 and 20 µg/ml in HeLa cells showed fragmentation of DNA by ladder pattern thereby indicates that cell death is related with apoptosis. By the increase of Bax/Bcl-2 ratio, zeolite X leads to the caspase-3 and caspase-9 activation and allow the cells to enter apoptosis. These collective results evidently showed that the influence of mitochondria-mediated signalling pathway in zeolite X induced apoptosis and intensely delivered investigational suggestion for the use of zeolite X as a significant curative agent in the preclusion and therapy of human cervical carcinoma.

     

Effect of aerosolized acetylcholine on bronchial blood flow

We studiedthe effects of aerosolized as well as intravenous infusion ofacetylcholine on bronchial blood flow in six anesthetized sheep.Intravenous infusion of acetylcholine, at a dose of 2 µg/kg, increased bronchial blood flow from 45 ± 15 (SE) to 74 ± 30 ml/min, and vascular conductance increased by 76 ± 22%. In contrast, aerosolized acetylcholine at doses of 2 and 20 µg/kg decreased bronchial vascular conductance by ~10%. At anaerosolized dose of 200 µg/kg, the bronchial vascular conductanceincreased by ~15%, and there was no further increase in conductancewhen the aerosolized dose was increased to 2,000 µg/kg. Pretreatmentof animals with a nitric oxide synthase inhibitor,N-nitro-L-argininemethyl ester hydrochloride, partially blocked the vasodilatory effectsof intravenous acetylcholine and completely blocked the vasodilatoryeffects of high-dose aerosolized acetylcholine. These data suggest thataerosolized acetylcholine does not readily penetrate the vascular wallof bronchial circulatory system and, therefore, has minimalvasodilatory effects on the bronchial vasculature.

     

Ascorbate enhancement of H1 histamine receptor sensitivity coincides with ascorbate oxidation inhibition by histamine receptors

Ascorbate has previously been shown to enhance both ₁- and ₂-adrenergic activity. This activity is mediated by ascorbate binding to the extracellular domain of the adrenergic receptor, which also decreases the oxidation rate of ascorbate. H1 histamine receptors have extracellular agonist or ascorbate binding sites with strong similarities to _1- and ₂-adrenergic receptors. Physiological concentrations of ascorbate (50 µM) significantly enhanced histamine contractions of rabbit aorta on the lower half of the histamine dose-response curve, increasing contractions of 0.1, 0.2, and 0.3 µM histamine by two- to threefold. Increases in ascorbate concentration significantly enhanced 0.2 µM histamine (5–500 µM ascorbate) and 0.3 µM histamine (15–500 µM ascorbate) in a dose-dependent manner. Histamine does not measurably oxidize over 20 h in oxygenated PSS at 37°C. Thus the ascorbate enhancement is independent of ascorbate's antioxidant effects. Ascorbate in solution oxidizes rapidly. Transfected histamine receptor membrane suspension with protein concentration at >3.1 µg/ml (56 nM maximum histamine receptor) decreases the oxidation rate of 392 µM ascorbate, and virtually no ascorbate oxidation occurs at >0.0004 mol histamine receptor/mol ascorbate. Histamine receptor membrane had an initial ascorbate oxidation inhibition rate of 0.094 min·µg protein^–1·ml^–1, compared with rates for transfected ANG II membrane (0.055 min·µg protein^–1·ml^–1), untransfected membrane (0.052 min·µg protein^–1·ml^–1), creatine kinase (0.0082 min·µg protein^–1·ml^–1), keyhole limpet hemocyanin (0.00092 min·µg protein^–1·ml^–1), and osmotically lysed aortic rings (0.00057 min·µg wet weight^–1·ml^–1). Ascorbate enhancement of seven-transmembrane-spanning membrane receptor activity occurs in both adrenergic and histaminergic receptors. These receptors may play a significant role in maintaining extracellular ascorbate in a reduced state. molecular complementarity; vitamin C; seven-transmembrane-spanning membrane receptors     

Stimulation of RNA Synthesis in Isolated Nuclei by Auxin-Binding Proteins-I and -II

The auxin-binding proteins (ABP-I and ABP-II) purified frometiolated mung bean seedlings stimulated RNA synthesis in isolatednuclei both in the presence and absence of (NH₄)₂SO₄. In theabsence of (NH₄)₂SO₄, maximum stimulation of RNA synthesis occurredat 100 µg ABP-I (25%) and 300 µg ABP-II (60%), whereasin the presence of 50 mM (NH₄)₂SO₄ maximum stimulation occurredat 60 µg ABP-I (10%) and 100 µg ABP-II (40%). Thesestimulatory effects on RNA synthesis by ABP-I and ABP-II werecompletely abolished by the addition of -amanitin (4 µg/0.5ml reaction mixture). IAA had no effect on the stimulation ofRNA synthesis by ABP-I and ABP-II. (Received September 30, 1985; Accepted March 5, 1986)     

A Simple and Inexpensive Design of Chemostat Enabling Steady-state Growth of Acer pseudoplatanus L. Cells under Phosphate-limiting Conditions

Operational and constructional details are given of a relativelysimple and inexpensive chemostat designed for the continuousculture of plant cells in suspension. This apparatus permitscontrol of the growth rate of sycamore, Acer pseudoplatanusL. cells in steady-state conditions. By alteration of the rateof input of medium different steady-state growth rates wereobtained over a wide range (mean doubling times from 182 h to36 h). In order to establish a growth-limiting nutrient thetime course of nutrient uptake in batch culture was measured.In batch culture the maximum growth obtained was proportionalto the initial concentration of phosphate when this was belowa concentration of 17 µg P per ml (as phosphate). It isalso shown in chemostat culture that the steady-state cell densityis proportional to the phosphate concentration in the mediumwhen this is below 17 µg P per ml (as phosphate). Phosphatewas therefore established to be the growth rate-limiting nutrientin chemostat culture at a concentration of 8•5 µgP per ml (as phosphate).     

The Movement of Chloramphenicol and Streptomycin in Broad Bean and Tomato Plants

The concentration of chloramphenicol in treated plants varieddirectly with that in solution over a range of 10–500µg./ml.Cut shoots contained more antibiotic than rooted plants. Chloramphenicolwas distributed throughout plants treated with 200µg./ml.solutions for 19 hours, but the concentration at the base ofplants was greater than that at the top. When treatment wascontinued for 5 days the concentration of chloramphenicol wasuniform throughout the plant. If, following treatment, the plantswere grown in water for 5 days, top leaves contained more antibioticthan lower leaves. The accumulation of chloramphenicol in rootedbroad bean plants was a linear function of water uptake. Rooted broad bean plants grown for 18 hours in streptomycinsolutions containing 500µg./ml. had a trace of antibioticin bottom leaves only. No streptomycin was present in plantstreated with less concentrated antibiotic solutions. Streptomycinmoved more readily in cut shoots of broad bean and cut shootsand rooted tomato plants, but the antibiotic content of bottomleaves was much greater than that of top leaves. The accumulationof streptomycin in rooted broad bean plants was exceedinglyslow.     

Synergistic antibacterial activity of carvacrol loaded chitosan nanoparticles with Topoisomerase inhibitors and genotoxicity evaluation

The increasing prevalence of antibiotic resistant bacteria is a significant healthcare crisis with substantial socioeconomic impact on global community. The development of new antibiotics is both costly and time-consuming prompting the exploration of alternative solutions such as nanotechnology which represents opportunities for targeted drug delivery and reduced MIC. However, concerns have arisen regarding genotoxic effects of nanoparticles on human health necessitating an evaluation of nanoparticle induced DNA damage.This study aimed to investigate the antibacterial potential of already prepared, characterized chitosan nanoparticles loaded with carvacrol and their potential synergism with Topoisomerase II inhibitors against S. aureus, E. coli and S. typhi using agar well diffusion, microdilution and checkerboard method. Genotoxicity was assessed through comet assay.Results showed that both alone and drug combinations of varying concentrations exhibited greater zones of inhibition at higher concentrations. Carvacrol nanoparticles combined with ciprofloxacin and doxorubicin significantly reduced MIC compared to the drugs used alone. The MIC₅₀ values for ciprofloxacin were 35.8 µg/ml, 48.74 µg/ml, 35.57 µg/ml while doxorubicin showed MIC₅₀ values of 20.79 µg/ml, 34.35 µg/ml, 25.32 µg/ml against S. aureus, E. coli and S. typhi respectively. The FICI of ciprofloxacin and doxorubicin with carvacrol nanoparticles found ≤ 0.5 Such as 0.44, 0.44,0.48 for ciprofloxacin and 0.45, 0.45, 0.46 for doxorubicin against S. aureus, E. coli and S. typhi respectively revealed the synergistic effect. The analysis of comet assay output images showed alteration of DNA at high concentrations.Our results suggested that carvacrol nanoparticles in combination with Topoisomerase inhibitors may prevent and control the emergence of resistant bacteria with reduced dose.     

Action Spectrum for Light-induced Chloroplast Accumulation in a Marine Coenocytic Green Alga, Bryopsis plumosa

A marine coenocytic green alga, Bryopsis plumosa exhibited multistriatetype protoplasmic streaming of a velocity less than 100 µm.min^–1.When the alga was illuminated locally, chloroplasts and othercell organelles accumulated in the illuminated zone. The actionspectrum for this reaction showed that blue light between 380and 500 nm was most effective. The velocity of chloroplast movement decreased when the cellwas totally illuminated with blue light, but no comparable changewas observed under red light illumination. Therefore, chloroplastaccumulation probably was caused by the reduced streaming ratein the illuminated zone. Electron microscopy showed cytoplasmic microtubules arrangedparallel to the cell axis in the vicinity of the chloroplasts.Chloroplast movement was inhibited heavily by treatment withantimicrotubule agents, but was little affected by cytochalasinB at a concentration of 10 µg/ml. (Received May 30, 1981; Accepted August 24, 1981)     

Effect of caffeinated drinks on substrate metabolism, caffeine excretion, and performance

The effect ofaddition of different dosages of caffeine (Caf) to acarbohydrate-electrolyte solution (CES) on metabolism, Caf excretion,and performance was examined. Subjects(n = 15) ingested 8 ml/kg of waterplacebo (Pla-W), 7% CES (Pla-CES), or 7% CES with 150, 225, and 320 mg/l Caf (CES-150, CES-225, and CES-320, respectively) during a warm-upprotocol (20 min) and 3 ml/kg at one-third and two-thirds of a 1-h timetrial. Performance was improved with Caf supplementation: 62.5 ± 1.3, 61.5 ± 1.1, 60.4 ± 1.0, 58.9 ± 1.0, and 58.9 ± 1.2 min for Pla-W, Pla-CES, CES-150, CES-225, and CES-320, respectively.The postexercise urinary Caf concentration (range 1.3-2.5 µg/ml)was dose dependent and always far below the doping level of theInternational Olympic Committee (12 µg/ml) in all subjects. Sweat Cafexcretion during exercise exceeded postexercise early-void urinary Cafexcretion. Caffeinated CES did not enhance free fatty acidavailability, ruling out the fact that performance improvement resultedfrom enhanced fat oxidation. It is concluded that addition ofrelatively low amounts of Caf to CES improves performance and thatpostexercise urinary Caf concentration remained low.

     

Almitrine and doxapram decrease fatigue and increase subsequent recovery in isolated rat diaphragm

McGuire, Michelle, Michael F. Carey, and John J. O'Connor.Almitrine and doxapram decrease fatigue and increase subsequent recovery in isolated rat diaphragm. J. Appl.Physiol. 83(1): 52-58, 1997.The effects ofalmitrine bimesylate and doxapram HCl on isometric force produced by invitro rat diaphragm were studied during direct muscle activation at37°C. Doxapram and almitrine ameliorate respiratory failureclinically by indirectly increasing phrenic nerve activity. This studywas carried out to investigate possible direct actions of these agentson the diaphragm before and after fatigue of the fibers. Two age groupsof animals were chosen [6-14 wk (group1) and 50-55 wk (group2)] because it is known that increasing agedecreases a muscle fiber's resistance to fatigue. Muscle strips wereisolated from both group 1 and group 2 and directly stimulated (2-mspulse duration, 5-15 V) to produce twitch tensions of 1.3 and 2.1 N/cm², respectively. At lowconcentrations, doxapram (20 µg/ml) and almitrine (12 µg/ml)had no effect on twitch contraction or 100-Hz tetanic tension. However,40 µg/ml doxapram and 30 µg/ml almitrine increased twitch tensionby 9.0 ± 1.4 and 11.6 ± 1.9%, respectively, in animals ofgroup 2 (n = 5). A fatigue protocol consistingof low-frequency stimulation (30-Hz trains, 250-ms duration every 2 sfor 5 min) caused a reduction of twitch tension in animals ofgroup 1 (48 ± 4% ofcontrol) and group 2 (28 ± 4% ofcontrol). At 90 min postfatigue, the twitch tension recovered to 72 ± 3 and 42 ± 2% of control values ingroup 1 and group2, respectively. In the presence of doxapram (20 µg/ml), there was a significant increase in the recovery of twitchtension at 90 min in group 1 andgroup 2 (84.5 ± 3.2 and 80.1 ± 2.8%, respectively) compared with controls at 90 min postfatigue. Inthe presence of almitrine (12 µg/ml), there was a full recovery fromfatigue in group 1 animals (100% ofcontrol) and a recovery to 95.6 ± 2.1% of control ingroup 2 animals at 90 min. Theseresults demonstrate a significant improvement in the rapidity andmagnitude of recovery from fatigue in the rat diaphragm muscle in thepresence of both doxapram and, especially, almitrine. These effects maybe due to changes in intracellular calcium, ADP/ATP ratios, or oxygenfree radical scavenging.

     

In vitro Demonstration of Lactogenic Activity in the Mammalian Placenta

As part of a comparative study of the occurrence of placentalprolactins among mammals, studies were done to see if the placentaeof a variety of mammals produce a prolactin, and if it is produced,during what period of gestation it is demonstrable. The lactogenicactivity of baboon, sheep, chinchilla, hamster, mouse, rat,and rabbit placentae at different stages of pregnancy were examinedby organ co-culture of placental explants with prelactatingmammary tissue, as well as by the addition of placental extractsto mammary organ cultures. The lactogenic activity of humanplacental lactogen (hPL) was also examined. Mammary tissue fromnulliparous (day 11 or 12) pregnant BALB/c Crgl mice were culturedin Waymouth's synthetic medium supplimented with insulin (5µg/ml) and aldosterone (1 µg/ml). The lactogenicactivity of the baboon, sheep, chinchilla, hamster, rat, andmouse placentae was clearly demonstrable. In the rabbit, thelactogenic activity was not detectable.     

RNA synthesis required for DNA replication in Vicia seed embryos

The synthesis of DNA and RNA during germination of Vicia seedswas examined. Incorporation of ³H-thymidine into DNA reacheda maximum at about 32 hr after the beginning of imbibition,and RNA synthesis was shown to precede DNA replication. Sedimentationanalyses of ³H-uridine-labeled RNAs indicated that the embryossynthesize all types of rRNA, heterodisperse RNA and 4–5SRNA before and also during the phase of DNA replication. Actinomycin-treatments at lower concentrations (50 or 100 µg/ml)resulted in the specific inhibition of rRNA synthesis. Suchinhibition did not lead to a large reduction in ³H-thymidineincorporation during the replication phase. However, DNA synthesiswas drastically inhibited by a higher level (200 µg/ml)of actinomycin D. The results strongly suggest the involvementof synthesis of heterodisperse RNA in DNA replication. (Received May 28, 1976; )     

Sialyl-Tn-KLH, glycoconjugate analysis and stability by high-pH anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD)

The quantitation of sialyl-Tn (STn) conjugated to keyhole limpethaemocyanin (KLH) can be determined by quantitating the amountof ^N-acetylneuraminic acid (NANA) released by acid or enzymaticdigestion. An optimal 0.1 N H₂SO₄ acid hydrolysis at 80°Cresults in quantitative release of NANA with minimal loss. Arapid isocratic method for the quantitation and separation ofNANA is described using high-pH anion-exchange chromatographyand pulsed amperometric detection (PAD). Multiple injectionof NANA standard and/or samples containing protein led to adecrease in the PAD response which was corrected by additionof internal standard, -2-keto-3-deoxyoctonate (KDO). The ratioof NANA/KDO peak area or peak height gives a linear responsewith increasing amount of NANA in the range 2.5–20 µg/ml(r² = 0.99). The limit of quantitation (LOQ) for NANA usingthis isocratic method is 1.9 µg/ml ({small tilde}160 pmol/25µl injection). Based on the multiple determination theglycoconjugate, STn-KLH, showed a NANA content of 2.9% (w/w).Acid hydrolysis and the sialidase treatment of STn-KLH bothyielded a similar NANA content. The carrier protein, KLH, showedthe absence of NANA. The stability of glycoconjugate STn-KLHwas monitored by a gradient method which separated possibledegradation products STn-crotyl, NANA and GalNAc. Subjectingthe glycoconjugate STn-KLH to various stress conditions of temperature,pH and oxidation does not result in any release of sialic acid,GalNac and STn-crotyl group. high-pH anion-exchange chromatography mono-saccharide analysis pulsed amperometric detection sialyl-Tn stability of glycoconjugate     

Noctiluca scintillans MACARTNEY in the Northern Adriatic Sea: long-term dynamics, relationships with temperature and eutrophication, and role in the food web

The first ‘bloom’ of Noctiluca scintillans in theNorthern Adriatic Sea was recorded in 1977. The organism causedseveral red tides in the whole basin during the late 1970s,a period characterized by increasing nutrient loads. Duringthe 1980s and early 1990s, there was no ‘red tide’,but the species was an almost constant summer presence, associatedwith high temperatures. Noctiluca scintillans was almost completelyabsent from 1994 until May 1997, concurrent with a general planktondecrease. From summer 1997, N. scintillans was recorded againin the whole basin, although there was no other signal of increasingeutrophication. In contrast to all previous observations, duringwinter 2002–2003, N. scintillans was continuously sampledin the Gulf of Trieste. We estimated experimentally growth andgrazing rates of the dinoflagellate at 9–10°C in cultureand consuming the natural assemblage. Noctiluca scintillanswas able to reproduce actively at low temperatures, showingsimilar growth rates in both experiments (k = 0.2 day^–1).The values found were close to those reported in the literaturefor higher temperatures. The natural diet was mainly composedof phytoplankton (ingestion = 0.008 µg C Noctiluca ^–1day^–1), microzooplankton (ingestion = 0.008 µg CNoctiluca ^–1 day^–1) and bacteria (ingestion = 0.005µg C Noctiluca ^–1 day^–1) with an average carboncontent of 0.138 ± 0.020 µg C Noctiluca cell^–1.