Localization and Characterization of a Novel 20 kDa Polypeptide in the Chloroplast of the Green Alga Dunaliella salina

Recent work with the green alga Dunaliella salina showed thepresence of a {small tilde}20 kDa chloroplast protein that wasrecognized by polyclonal antibodies raised against the isolatedLHC-II [Webb M.R. and Melis A. (1995) Plant Physiol. 107: 885].In this report, a characterization of the {small tilde}20 kDapolypeptide is presented. It is shown that it is localized inthe chloroplast envelope membrane of D. salina. The abundanceof this protein is constant on a per cell basis and independentof the light regime during cell growth. The {small tilde}20kDa polypeptide is easily degraded to a {small tilde}19 kDaproduct during sample preparation. A limited amino acid sequenceof 21 residues from the free N-terminus of the {small tilde}19kDa product was obtained. On the basis of this partial sequence,it was concluded that the {small tilde}20 kDa polypeptide isnot a degradation product of a known LHC-II but rather a novelprotein. The {small tilde}20kDa polypeptide did not cross-reactwith antibodies raised against the Cbr (carotene biosynthesis-related)gene product and showed a different electrophoretic mobilityfrom the latter. Light-shift experiments suggest that the {smalltilde}20 kDa polypeptide is not an ELIP (early light-inducibleprotein). Possible functions of the {small tilde}20 kDa proteinare discussed. ¹Permanent address: Department of Biochemistry, University oflund, PO Box 124, S-221 00 Lund, Sweden     

Some taste molecules and their solution properties.

The solution properties of a variety of different sapid substances from all four basic taste modalities, namely, sweet (n = 24), salty (n = 7), sour (n = 11) and bitter (n = 2), have been investigated. Some multisapophoric molecules, i.e. molecules exhibiting more than one taste, have also been included in the study in an attempt to define their properties in relation to the tastes they exhibit; eight sweet-bitter and three salty-bitter molecules were used. The density and sound velocity of their solutions in water have been measured and their apparent volumes, apparent compressibilities and compressibility hydration numbers calculated and compared. Apparent molar volumes (phi(v)) and apparent specific volumes (ASV) reflect the state of hydration of the molecules, and thus their extent of interaction with water structure. The range of ASVs reported are 0.13-0.49 cm3/g for salty molecules, 0.55-0.68 cm3/g for sweet molecules, 0.53-0.88 cm3/g for sweet-bitter molecules and a much wider range (0.16-0.85 cm3/g) for sour molecules. Isentropic apparent specific compressibilities range from -2.33 x 10(-5) to -8.06 x 10(-5) cm3/g x bar for salty molecules, -3.38 x 10(-7) to -2.34 x 10(-5) cm3/g x bar for sweet molecules, +6.35 x 10(-6) to -2.22 x 10(-5) cm3/g x bar for sweet-bitter molecules and +6.131 x 10(-6) to -2.99 x 10(-5) cm3/g x bar for sour molecules. Compressibility hydration numbers are also determinable from the measurements of isentropic compressibilities and these reflect the number of water molecules that are disturbed by the presence of the solutes in solution. This study also shows that it is possible to group isentropic apparent molar compressibility values by the taste quality exhibited by the molecules in the same order as for ASV.     

Summer nutrient dynamics in the Middle Atlantic Bight: primary production and utilization of phytoplankton carbon

In late summer, production and utilization of carbon in thestratified water of the Middle Atlantic Bight appears to approachsteady-state conditions. In the euphotic zone there is a paniculateorganic carbon (POC) pool of {small tilde}6000 mg Cm^–2.Primary production adds {small tilde}350 mg C m^–2 d^–1,while zooplankton ingestion removes {small tilde}450 mg C m^–2d^–1, of which {small tilde}135 mg C m^–2 d^–1are returned to the POC pool as feces. Sinking of POC averages{small tilde}240 mg C m ^–2 d^–1. Thus, there is anet loss from the euphotic zone of {small tilde}200 mg C m^–2d^–1, which represents a removal rate from the POC poolof {small tilde}3%d^–1. However, sinking losses of phytoplanktoncarbon from the POC pool were small ({small tilde}12 mg C m^–2d^–1), which suggests that most of the primary productionenters the pelagic food chain. This is in sharp contrast tothe conditions in early spring, when the POC pool increasessubstantially, and the main loss is sinking rather than heterotrophicconsumption. ^*This research was supported by the U.S. Department of Energyunder Contract No. DE-AC02-76CH000I6.     

Effects of therapeutic doses of amiloride and hydrochlorothiazide on taste, saliva and salt intake in normotensive adults

Tentative evidence suggests that hydrochlorothiazide (HCTZ)and amiloride may alter salivary function, taste sensitivityand dietary intake. The effects of these diuretics on salivaryflow and composition, taste attributes (i.e. recognition thresholds,perceived intensity ratings and preference) as well as sodiumintake were further examined in 73 normotensive adults in adouble-blind, placebo-controlled, cross-over study. Followingrandom assignments to one of three groups [5 mg twice per dayof amiloride (n = 24), 50 mg/day of HCTZ (n = 24) or placebo(n = 25)], subjects took appropriate placebos for 2 weeks, activedrug for 8 weeks and placebo for 3 weeks. Relative to baselinevalues, amiloride treatment resulted in a significant 39% decreasein stimulated salivary sodium levels and a 28% decline in NaClrecognition thresholds. HCTZ significantly stimulated sodiumintake as the sodium/creatinine ratio was {small tilde}50% higherfollowing 4 weeks of drug use relative to baseline values. Subjectswere subjectively unaware of these changes. Potential mechanismsand clinical implications of these findings are considered.     

The chorda tympani and glossopharyngeal nerves in the adult hamster

The numbers and diameters of axons in the intact chorda tympani(CT) and lingual branch of the glossopharyngeal nerve (GN) arequantified with the use of electron microscopic photomontages.The cross-sectional diameters of the CT and GN average 68 and86 microns, respectively. The intact CT contains {small tilde}1050 fibers, 63% are unmyelinated and 37% are myelinated. TheGN contains {small tilde} 1600 fibers, 79% are unmyelinatedand 21% are myelinated. Both nerves are made up of relativelysmall unmyelinated and myelinated fibers, although the GN showsa broader distribution of diameters for its myelinated fibersdue to the presence of general somatosensory fibers. Followingde-efferentation, there is a 48% reduction in the number ofunmyelinated fibers in the CT. Fifty-two per cent of the unmyelinatedfibers are sensory. The number of myelinated fibers is not significantlyreduced and nearly all of the myelinated fibers are sensory.Sixty-seven per cent of the fibers within the CT are sensory.The de-efferented CT contains an equal number of unmyelinatedand myelinated axons and a total of {small tilde} 700 fibers.Comparable data in the rat indicate that its intact and de-efferentedCT are organized differently in regards to the numbers of sensoryand motor, and myelinated versus unmyelinated fibers. The findingsof the present study, together with the available data fromother species, suggest that anatomical differences in the make-upof the major gustatory nerves do not contribute in any obviousway to the known differences in the response properties betweenthe rat and hamster CT, and that the number of myelinated fibersin the visceral motor component of the CT varies considerablyacross species.     

In Vitro Phosphorylation of Proteins in IAA-Treated Mesocotyls in Zea mays

Five-mm sections of elongation zones of Zea mesocotyls wereincubated for designated periods with various concentrationsof IAA. In vitro protein phosphorylation in the soluble fraction(85,000 x g supernatant) prepared from the sections was analyzedby sodium dodecyl sulfate-polyacrylamide gel electrophoresis.The phosphorylation of proteins in the soluble fraction thathad been prepared from sections incubated for 20 min in thepresence of 10{small tilde}^s M IAA was greater than that inthe sections incubated for 20 min without IAA. The amount ofphosphorylation of proteins per protein became higher when higherconcentrations increased (10{small tilde}⁸—10{small tilde}⁵M).The growth of sections incubated in the presence of 10{smalltilde}⁸ M IAA or higher concentrations was greater than thatof sections incubated in the absence of IAA. The promotion ofgrowth by IAA was greater at higher concentrations of IAA. Proteinsin the soluble fraction, prepared from sections incubated for20 min in the presence of 10{small tilde}⁵ M IAA, were phosphorylatedin the presence of either 10 fM cAMP, 10 µM cGMP, 100µM W-7, 100 µM W-5, 20 µM H-7 or 20 µMHA1004. The calmodulin antagonist, W-7, and the inhibitor ofprotein kinase C, H-7, inhibited the phosphorylation of proteinsstimulated by incubation with IAA. These results suggest thatIAA promotes cell elongation via protein phosphorylation thatdepends on calmodulin-dependent protein kinase and protein kinaseC. (Received November 29, 1995; Accepted May 20, 1996)     

Early developmental stages of greasyback shrimp,Metapenaeus ensis (de Haan, 1844) (Crustacea, Decapoda, Penaeidae)

Metapenaeus ensis was spawned and laboratory cultured untilthe post-larval stage to illustrate and describe its embryonicand larval development. Fecundities ranged between 454 000 and689 000 eggs, and {small tilde}99.2% of spawned eggs hatchedafter 12 h and 40 min at 33.5 p.p.t. and 29.0-29.1°C. Sixnaupliar, three protozoeal, three mysis and one post-larvalstages were noted. A minimum of {small tilde}10 days (249 h20 min) from the time of hatching were required to completethe larval stages by subsisting only on Chaeioceros gracilisand Tetraselmis tetrathele at varying temperature and salinityof 28.1-29.8°C and 33.5—34.5 p.p.t., respectively.The embryonic and larval developmental stages of M.ensis aregenerally similar to those of other known penaeid species, exceptfor the size and structure of diagnostic characters, setationof appendages and duration of metamorphoses.     

Diurnal vertical migration of Gymnodinium mikimotoi during a red tide in Hoketsu Bay, Japan

The depth, velocity and timing of the vertical migration ofGymnodinium mikimotoi were examined using fluorometric fieldobservations. Gymnodinium mikimotoi can migrate vertically {smalltilde}20 m daily at velocities of {small tilde}2.2 m h^–1     

Maize Root Plasma Membranes Isolated by Aqueous Polymer Two-phase Partitioning: Assessment of Residual Tonoplast ATPase and Pyrophosphatase Activities

Plasma membrane-enriched fractions were obtained from maizeroots by differential centrifugation and aqueous polymer two-phasepartitioning. Plasma membrane enrichment and tonoplast depletionwere assessed from comparisons of marker ATPase specific activitiesamong starting microsomal, intermediate, and final phase-partitionedfractions. ATPase assays were conducted in the presence of themembrane permeabilizing detergent Brij 58. The plasma membranefraction was enriched in ATPase specific activity at pH 6·5.This activity was strongly inhibited by vanadate (50% inhibitionat {small tilde}3 mmol m     

The annual cycle of Mesodinium rubrum in the waters surrounding the Isles of Shoals, Gulf of Maine

Mesodinium rubrum was collected in Kemmerer bottles, fixed inBouin's solution and protargol stained. Cell volume showed aseasonal change of over an order of magnitude, being largest(3.25x10⁴ µm³) in the early spring and smallest in thesummer. Cell abundance was highest in the spring and lowestin the summer. Biomass followed a similar trend ranging from{small tilde}1 to 147 J m^–3 Production, estimated by amultiple regression that incorporated ambient temperature andcell volume, was 2.5 kJ m^–3 day^–1 This is {smalltilde}0.3% of the primary production.     

Abundance and diversity of surface zooplankton in the Gulf of Aqaba, Red Sea, Egypt

Surface zooplankton were studied in Egyptian coastal watersof the Gulf of Aqaba, from bimonthly samples from July 1994to May 1995. Species diversity, numerical abundance and dynamicswere analysed for each taxon, at six sites, inside three Protectorates.A total of 62 taxa and species were identified. At all sites,copepods were predominant in the standing crop with an averageof 1945 ind. M^–3 and formed {small tilde}75.5%, numerically,of the total zooplankton community. The meroplanktonic larvaeoccupied the second rank and they constituted {small tilde}19.7%of the total zooplankton. Seasonally, the main peak of zooplanktonabundance was recorded in winter (January) with an average of3510 ind. M^–3 while September was characterized by thelowest density (1906 ind. m^–3 The relatively higher diversityvalues were recorded at Ras Mohammed Protectorate and a progressivedecline in diversity was observed northward.     

Temporal dissociation of taste mixture components

Reaction times to salty and bitter tastes as single stimuliand in mixture were measured using response time deadlines rangingfrom 300 to 2500 ms. Salty reaction times were the same whethersalty was in mixture with bitter or a single stimulus, and theywere always shorter than bitter reaction times. Reaction timeto bitter was slower in mixture with salty than as a singletaste. Salty, alone and in mixture, was correctly identifiedon {small tilde}80% of the trials within 500 ms while correctbitter identifications did not reach similar levels until 1000ms. Bitter in mixture with salty never reached that level ofcorrect responding and correct responses actually decreasedslightly at response time deadlines of 2500 ms. The resultsshow that differences in taste onset latency are great enoughto allow identification of single tastes in mixtures.     

Stability of fungiform papillae pattern in rats

A rat has {small tilde} 180 taste-bud-bearing fungiform papillaewhich form a unique individual pattern. This study deals withthe stability of this pattern. The results indicate that thepattern is stable over at least 1 year.     

Natural ingestion rates and grazing impact of the marine cladoceran Penilia avirostris Dana in Tolo Harbour, Hong Kong

The gut fluorescence method was used to study algal grazingby Penilia avirostris in a semiestuarine embayment. Grazingimpact estimated from ingestion rate and animal abundance revealedthat only {small tilde}1% of the algal biomass was grazed perday by the cladocerans.     

The Prothoracicotropes: Source of the Prothoracicotropic Hormone

SYNOPSIS. An in vitro assay for the insect prothoracicolropichormone (PTTH) has been developed which measures the rate ofecdysone synthesized by Manduca sexta prothoracic glands (PG)stimulated in vitro by PTTH. This assay has been used to quantifyPTTH in single neurosecretory cells (NSC) resulting in the identificationof one NSC in each hemisphere of the brain as the prothoracicotrope,source of PTTH. The axonal and dendritic distribution of theprothoracicotrope has been determined by cobalt filling withsilver intensification. From a comparison of the titers of PTTHin brains, corpora cardiaca and corpora allata during larval-pupaldevelopment, the corpus allatum has been identifiedas the neurohemalorgan for PTTH. Electron microscopic analyses suggest that theacellular sheath surrounding the corpus allatum contains theaxon terminals of the prothoracicotropes. There is at least one form of PTTH, {small tilde}22,000 molwt (big PTTH), and possibly a smaller form of about 7,000 molwt (small PTTH). Bioassay and PTTH hemolymph titer data duringthe head critical period (HCP) for larval-larval developmentreveal that big PTTH is released as a single peak lasting {smalltilde}6 hr. By contrast, during the first HCP of the last larvalinstar PTTH is released over a period of {small tilde}18 hrin three bursts, but its molecular weight has not been establishedwith certainty. The kinetics of PG activation by these two formssuggest that big PTTH may function to activate the PG dramaticallyand thereby elicit molting, while small PTTH may activate thePG minimally at the time of cellular reprogramming.     

The Hydrostatic and Hydrodynamic Volumes of Polyols in Aqueous Solutions and Their Sweet Taste

The tastes and solution properties of sugar alcohols were studiedin an attempt to illuminate the mechanism of sweet taste chemoreception.The SMURF method was used to measure taste time-intensity ofaqueous solutions of sugar alcohols and the results were interpretedusing the Stevens power function and kinetic parameters. Theapparent molar volumes, apparent specific volumes, partial molarvolumes, partial specific volumes and intrinsic viscositiesof the solutions were studied. Apparent molar volume reflectsthe size of the molecule in a hydrostatic state whereas intrinsicviscosity gives a measure of the size of the molecules in ahydrodynamic state. Generally the apparent molar volumes ofthe polyols are 6–13% greater than those of the parentsugars, indicating less interaction with the water structure.Apparent specific volume values can predict taste quality, andthe average apparent specific volume for the sugar alcoholsstudied fits within the central part of the sweet range, i.e.0.5–0.68 cm³/g, which accords with their ability to elicita pure sweet taste response. Intensities and persistences ofsweetness in the polyols followed the same trend as intrinsicviscosities. Chem. Senses 22: 149–161, 1997.     

Estimating Initial Epidemic Growth Rates

The initial exponential growth rate of an epidemic is an important measure of disease spread, and is commonly used to infer the basic reproduction number $\mathcal{R}_{0}$ . While modern techniques (e.g., MCMC and particle filtering) for parameter estimation of mechanistic models have gained popularity, maximum likelihood fitting of phenomenological models remains important due to its simplicity, to the difficulty of using modern methods in the context of limited data, and to the fact that there is not always enough information available to choose an appropriate mechanistic model. However, it is often not clear which phenomenological model is appropriate for a given dataset. We compare the performance of four commonly used phenomenological models (exponential, Richards, logistic, and delayed logistic) in estimating initial epidemic growth rates by maximum likelihood, by fitting them to simulated epidemics with known parameters. For incidence data, both the logistic model and the Richards model yield accurate point estimates for fitting windows up to the epidemic peak. When observation errors are small, the Richards model yields confidence intervals with better coverage. For mortality data, the Richards model and the delayed logistic model yield the best growth rate estimates. We also investigate the width and coverage of the confidence intervals corresponding to these fits.     

Changes in number and morphology of fungiform taste buds in rat after transection of the chorda tympani or chordalingual nerve

In normal rats there is one taste bud on the apical surfaceof each fungiform papilla. These taste buds are innervated bythe chorda tympani proper nerve (CT). According to general consensus,after cutting the nerve the taste buds should disappear. Inthis study, performed on 24 rats divided in six groups, theCT nerve on the left side (singly denervated) and the combinedchorda-lingual (CT-L) nerve on the other side (doubly denervatedwere permanently interrupted. The animals were sacrificed after5, 10, 20, 35,60 and 100 days and their tongues serially sectionedfor light microscope examiation. Some papillae were examinedunder an electron microscope. The papillae were categorizedinto three groups: papillae with a normal looking taste bud,with an abnormal looking taste bud and without a taste bud.The results showed a substantial number of papillae with a normallooking taste bud present at all time intervals in all animals.More specifically, on the singly denervated side the proportionof normal looking taste buds stayed below 10% until day 60,when it increased to 15% and to 23% on day 100. The proportionof abnormal looking taste buds decreased from above 92% by day5 to 49% on day 100. The percentage of fungiform papillae withoutsigns of a taste bud was relatively low on the singly denervatedside at times (1, 5, 16, 29, 34 and 28%). On the doubly denervatedside fewer than than 4% normal looking taste buds were foundthroughout the time period. The proportion of abnormal lookingtaste buds decreased from {small tilde} 96% by day 5 to 35%on day 100. A significantly higher proportion of papillae withno taste bud was observed on this side from day 10 onwards.(1, 29, 32, 52, 60 and 63%). The reasons for the differencein tast bud number between the doubly and singly denervatedsides are unknown, but it is possible that collaterals fromother (non-gustatory) nerves have an ability, although limited,to induce and maintain fungiform taste buds. In other words,the capacity to induce taste bud formation is not limited exclusivelyto gustatory nerves.     

Short-term changes of protozoan control on autotrophic picoplankton in an oligo-mesotrophic lake

In May 1994, we investigated the short-term development of theplanktonic community in the epi- and metalimnion of an oligo-mesotrophiclake (Piburger See, Tyrol), focusing on trophic links betweenprotists and picoplankton, but also including phyto- and zooplankton.Uptake experiments with fluorescently labelled bacteria (FLB)and picocyanobacteria (FIC) were performed in order to comparethe importance of both prey types as carbon sources for bacterivorousprotists. Heterotrophic nanoflagellates (HNF) were responsiblefor {small tilde}90% of total protozoan picoplanktivory (FLB+ FLC); ciliates accounted for {small tilde}10%. A selectivityindex related to prey density showed that both HNF and ciliatesclearly preferred FLC over FLB. The mean cell size of autotrophic(prokaryotic) picoplankton (APP) was nearly three times larger(0.323 µm³) and much less variable than mean bacterialcell volume (0.122 µm³). Although APP biomass was on averageonly 8.6% of total picoplankton biomass, pico-cyanobacteriaaccounted for a mean 15.9% of total HNF carbon uptake. We calculatedthat total HNF grazing could match potential APP maximum growthrates at the beginning of the study period. A strong decreasein HNF individual clearance rate (CR) on APP was clearly relatedto a fall in the percentage of choanofiagellates (from 75 to{small tilde}10% of the HNF community). A simultaneous decreasein HNF biomass and CR was followed by a steep increase in APPabundance; APP abundance and HNF biomass were highly negativelycorrelated both in the epi- and the metalimnion (r_{1 EM} = –0.879,r_{1 META} = =0.907; P = 0.001). Total rotifer abundance increasedby a factor of 50 within 2 weeks and was also negatively correlatedwith HNF biomass (r_{1 EM} = –0.852, P < 0.001; r_{1 META}= –0.659, P < 0.05). HNF grazing was found to exerta strong short-term control on picocyanobacteria and this linkwas probably broken by an increase in metazooplankton, especiallydue to rotifer predation on HNF.