Seasonality, substrate perference and attachment sites of epizoic diatoms on cladoceran zooplankton

Cladocerans from three lakes in northwest Iowa were examinedfor attached diatoms over a period of 1 year to assess the seasonality,substrate preference and attachment site specificities of epizoicdiatoms. Over 90% of the cladocerans had attached diatoms immediatelyfollowing ice thaw, when the lakes were not yet thermally stratified,surface water temperatures were low(10–15°C)and watertransparency was at its annual high. Mean maximum density ofdiatoms on cladocerans averaged among lakes at this time was3000 cells animal^–1. The dominant epizoic diatom was Synedracyclopum Brutschy, which was found most often on large, pelagicDaphnia pulicaria and Daphnia galeata mendotae. Heavily infestedanimals had diatoms concentrated on the second antennae andanterior ventral margin of the carapace. Animals with <5epizoic diatoms were more likely to have cells attached to thepostabdomen or tail spine. In addition to living epizoically,S.cyclopum was found free living in the plankton, exhibitingtemporal fluctuations in densities similar to epizoic counterpartsHowever, the densities of the free-living cells seldom exceededepizoic densities, suggesting that S.cyclopum is adapted forgrowth on motile cladoceran substrates. ¹Present address: Savannah River Ecology Lab, Drawer E, Aiken,SC 29802, USA ²Present address: Department of Fisheries and Aquatic Sciences,7922 NW 71st St, Gainesville, FL 32606, USA     

Localization and Binding Characteristics of a High-Affinity Binding Site for N--Acetylchitooligosaccharide Elicitor in the Plasma Membrane from Suspension-Cultured Rice Cells Suggest a Role as a Receptor for the Elicitor Signal at the Cell Surface

A high-affinity binding site for N-acetylchitooligosac-chlarideelicitor was found to localize in the plasma membrane from suspension-culturedrice cells. Binding kinetics as well as the specificity of thisbinding site corresponded well with the behavior of the ricecells to the editor. These characteristics suggest that thebinding site represents a functional receptor for N-acetylchitooligosaccharideelicitor in rice. ²Present address: Okinawa Prefectural Livestock ExperimentalStation, 2009-5 Shoshi, Nakijin-son, Okinawa, 905-04 Japan. ³Present address: School of Hygiene and Public Health, The JohnsHopkins University, 615 North Wolfe Street, Baltimore, Maryland,21205 U.S.A. ⁴Present address: University of Tenessee, Microbiology, knoxville,Tennessee, 37996 U.S.A.     

COMPARISON OF EUTHECOSOMATOUS PTEROPODS IN THE PLANKTON AND SEDIMENTS OFF BARBADOS, WEST INDIES

The euthecosomatous pteropod fauna of Barbados plankton wascompared with euthecosome shells occurring in recent sediments.Twenty species of euthecosomes were collected in the same relativeabundance in both provinces. Differences in the average sizesof Spiratella inflata and Creseis virgula conica, the most commonspecies were not statistically significant although differencesin the size-frequency histograms were noted. It is concludedthat euthecosomes deposited in the upper sediment layers offBarbados accurately reflect the species composition and relativeabundance of euthecosome species in the plankton. ¹Supported by a Postgraduate Scholarship from the National ResearchCouncil of Canada and NRC Grant No. A5248 to Dr. C.M. Lalli. ²Present address: Department of Oceanography, Dalhousie University,Halifax, Nova Scotia, Canada.     

The Deduced Amino Acid Sequence of Phytochrome from Adiantum Includes Consensus Motifs Present in Phytochrome B from Seed Plants

A cDNA for the phytochrome of the fern Adiantum capillus-venerisL. was cloned and sequenced. The deduced phytochrome is 50{smalltilde}55% identical to phytochromes of seed plants, and 68%identical to Selaginella phytochrome. Regions resemble thosein previously characterized phytochromes from ferns, lower plantsand seed plants. ³Present address: Yamanouchi Pharmaceutical Co., Ltd., 21 Miyukigaoka,Tsukuba-shi, Ibaraki, 305 Japan ⁴Present address: Plant Growth Regulation Laboratory, The Instituteof Physical and Chemical Research (RIKEN), Hirosawa 2-1, Wako-shi,Saitama, 351-01 Japan ⁵Present address: Advanced Research Laboratory, Hitachi, Ltd.,Hatoyama, Saitama, 350-03 Japan     

The influence of water circulation on chlorophyll-turbidity relationships in Lake Okeechobee as determined by remote sensing

The spatial distribution of phytoplankton can be difficult toassess in shallow, productive aquatic systems due to frequentalgal blooms, high turbidity and sediment-resuspension events.We conducted a study to assess the distribution of suspendedparticles in Lake Okeechobee, Florida, utilizing both Landsat(1974–75) or Advanced Very High Resolution Radiometer(AVHRR) (1987) satellite remote sensing. Surface water sampleswere collected by helicopter to determine in situ chlorophyll-aand turbidity levels at 20 stations on four dates in 1974–75and six dates in 1987. Remotely sensed reflectance values agreedwell with in situ particle densities at the 20 in-lake stations(average R²: Landsat = 0.81, AVHRR = 0.53) and independent,synoptic boat mapping of algal blooms (r² = 0.79, P < 0.01).Basin-wide maps of chlorophyll and turbidity, as well as additionalspatial sampling, both indicated that these parameters are notnecessarily coupled in Lake. Our data concur with the hypothesisthat the spatial distributions of chlorophyll and turbidityare shaped by different forces. The highest concentrations ofchlorophyll occurred in the vicinity of tributary nutrient inputsat the lake's perimeter, while turbidity increased towards thecenter of the lake, reflecting predominant water circulationpatterns. ²Present address: Department of Biology & Romberg TiburonEnvironmental Center, San Francisco State University, San Francisco,CA 94132, USA ³Present address: Idaho Division of Environmental Quality, 1420North Hilton, Boise, ID 83706-1260, USA ⁴Present address: 5642 Santiago Circle, Boca Raton, FL 33433,USA     

High Affinity of the 5'-Upstream Region of a Winged Bean Chymotrypsin Inhibitor Gene for Nuclear Matrix

The 5'-upstream region of a winged bean chymotrypsin inhibitorgene (WCI-3b) was found to have a high affinity for nuclearmatrix. The region, named WCI-3b MAR (matrix attachment region),is highly A+T-rich and contains multiple sites interacting withnuclear matrix. A MAR was also found in the corresponding regionof the WCI-x gene, another active gene of the WCI family. SeveralMAR-binding proteins were detected in the wheat nuclear matrix. ⁴Present address: Friedrich Miescher Institute, P.O. Box 2543,CH-4002 Basel, Switzerland. ⁵Present address: Research Institute for Biological Sciences(RIBS), Kayo-cho, Jyobo-gun, Okayama, 716–1241 Japan.     

Photoconversion of protochlorophyll to chlorophyll a in a mutant of Chlorella regularis

Dark-grown cells of a mutant strain of Chlorella regularis containedchlorophyll a and protochlorophyll, phytyl ester of protochlorophyllide.Under illumination, protochlorophyll was quantitatively anddirectly converted into chlorophyll a. The photoconversion wasdependent on light intensity and temperature and proceeded ina cell-free preparation. The pathway of chlorophyll formation found in the mutant cellsis entirely different from that from protochlorophyllide byway of chlorophyllide a, which is generally observed in greenplants. ¹Present address: Division of Biology, Medical College of Miyazaki,Miyazaki 889-16, Japan. ²Present address: Division of Environmental Biology, The NationalInstitute for Environmental Studies, Ibaragi 300-21, Japan. (Received October 24, 1975; )     

Distribution of Fallover in the Carboxylase Reaction and Fallover-Inducible Sites among Ribulose 1,5-Bisphosphate Carboxylase/Oxygenases of Photosynthetic Organisms

The biphasic reaction course, fallover, of carboxyla-tion catalysedby ribulose 1,5-bisphosphate carboxylase/ox-ygenase (RuBisCO)has been known as a characteristic of the enzyme from higherland plants. Fallover consists of hysteresis in the reactionseen during the initial several minutes and a very slow suicideinhibition by inhibitors formed from the substrate ribulose-l,5-bisphosphate(RuBP). This study examined the relationship between occurrenceof fallover and non-catalytic RuBP-binding sites, and the putativehysteresis-inducible sites (Lys-21 and Lys-30S of the largesubunit in spinach RuBisCO) amongst RuBisCOs of a wide varietyof photosynthetic organisms. Fallover could be detected by followingthe course of the carboxylase reaction at 1 mM RuBP and thenon-catalytic binding sites by alleviation of fallover at 5mM RuBP. RuBisCO from Euglena gracilis showed the same linearreaction course at both RuBP concentrations, indicating an associationbetween an absence of fallover and an absence of the non-catalyticbinding sites. This was supported by the results of an equilibriumbinding assay for this enzyme with a transition state analogue.Green macroalgae and non-green algae contained the plant-type,fallover enzyme. RuBisCOs from Conjugatae, Closterium ehrenbergii,Gona-tozygon monotaenium and Netrium digitus, showed a muchsmaller decrease in activity at 1 mM RuBP than the spinach enzymeand the reaction courses of these enzymes at 5 mM RuBP werealmost linear. RuBisCO of a primitive type Conjugatae, Mesotaeniumcaldariorum, showed the same linear course at both RuBP concentrations.Sequencing of rbcL of these organisms indicated that Lys-305was changed into arginine with Lys-21 conserved. ⁷ On leave from Research and Development Center, Unitika Ltd.,23 Kozakura, Uji, Kyoto, 611 Japan. ⁸ Present address: Department of Applied Biological Chemistry,Faculty of Agriculture, Tohoku University, Tsutsumidori-Ama-miyamachi, Sendai, 981 Japan. ⁹ Present address: National Institute for Basic Biology, Myodaiji,Okazaki, 444 Japan. ¹⁰ Present address: Department of Environmental Biology, TokyoPharmaceutical University, Hachioji, Tokyo, 192-03 Japan.     

Separation and Partial Characterization of Membranes from Prochloron sp.

Two differently colored membrane preparations were separatedfrom the prochlorophyte, Prochloron sp., by mechanical disintegrationof the cells followed by sucrose density gradient centrifugation.An orange-colored preparation, containing zeaxanthin as themajor constituent pigment, seemed to comprise the cytoplasmicmembrane. The other green-colored membrane preparation, containingß-carotene and chlorophyll a and b as major pigmentconstituents, was identified as the thylakoid membrane. Thetwo types of membranes were compared as to their absorptionspectra and buoyant densities. ¹ This work is one of the results of the 8th International Expeditionon Prochloron organized by Dr. R. A. Lewin, University of Californiaat San Diego. ⁵ Present address: Solar Energy Research Group, The Algatron,The Institute of Physical and Chemical Research (RIKEN), Wako-shi,Saitama 351, Japan. ⁶ Present address: National Institute for Basic Biology, Okazaki444, Japan. (Received October 19, 1984; Accepted January 7, 1985)     

Intersetule distances are a poor predictor of particle-retention efficiency in Diaptomus sicilis

In contrast to published results for the copepod Acartia, thecumulative frequency distribution of intersetule distances onthe second maxillae of Diaptomus sicilis is a poor predictorof the experimentally determined particle-retention efficienciesof feeding. Moreover, a simple model that includes intersetalretention also does not work. This may be because D. sicilisraptorially seizes particles, as well as filtering them. Also,certain assumptions about the hydrodynamics of the filteringprocess that are implicit in the intersetule-distance modelsmay be false for Diaptomus and other calanoid copepods whosesecond maxillae form a stationary filter chamber. ¹GLERL Contribution No. 246 ²Present address: Department of Biological Sciences, CaliforniaState University, Chico, CA 95929, USA     

Molecular Cloning and Characterization of S-Adenosyl-L-Methionine:Scoulerine-9-O-Methyltransferase from Cultured Cells of Coptis japonica

S-Adenosyl-L-methionine : scoulerine-9-O-methyltransferase (SMT)catalyzes the transfer of the S-methyl group of S-adenosyl-L-methionineto the 9-hydroxyl group of scoulerine during the biosynthesisof berberine. We have isolated functionally active cDNA clones(pCJSMTs) from a cDNA library prepared from cultured cells ofCoptis japonica. The longest cDNA insert (pCJSMT1) had an openreading frame that encoded 351 amino acids, but the calculatedmolecular mass (38,364 Da) of the deduced product was slightlylower than the experimentally determined molecular mass of purifiedSMT. Rapid amplification of the 5' end of the cDNA indicatedthat the full-length cDNA of SMT consisted of 1,458 nucleotidesthat encoded 381 amino acids. When the full-length cDNA wasexpressed in E. coli, the molecular mass of the expressed SMTwas greater than that of native SMT in Coptis cells. This resultsuggests that SMT might be produced in a pre-mature form andprocessed post-translationally. SMT was also found to exhibitsequence homology to other O-methyltransferases from plantsand N-terminal region of the SMT polypeptide appeared to benecessary for enzymatic activity. ¹Present address: High Quality Life Research Laboratories, SumitomoMetal Industries, Ltd., 3-5 Hikaridai, Seika, Sourakugun, Kyoto,619-02 Japan ²Present address: Suntory Research Center, 1-1-1 Wakayamadai,Shimamoto, Mishima-gun, Osaka, 618 Japan ³Present address: Department of Cell Biology, The Scripps ResearchInstitute, La Jolla, CA 92037 U.S.A.     

Effects of Exogenous Auxin on the Regulation of Elongation Growth of Excised Segments of Vigna Hypocotyls under Osmotic Stress

IAA applied simultaneously with osmotica greatly enhanced theadaptive recovery of the elongation growth of segments of Vignahypocotyls during osmotic stress irrespective of whether ornot absorbable solutes were present. IAA stimulated both thesurface pump and the xylem pump, which have been shown to bestimulated by osmotic stress and to control the yielding ofthe cell wall and the absorption of solutes. Thus, wall extensibilityand the effective turgor were further enhanced under osmoticstress in the presence of IAA. These results indicate that thesimultaneous presence of IAA can reduce the inhibition of growthby osmotic stress, and they support numerical predictions basedon the apoplast canal model. The mechanism involved in the rapidrecovery of growth is discussed. ¹ Present address: Research Centre, Guangxi Agricultural University,Xiu Ling Rd., Nanning, Guangxi 530005 China. ² Present address: Biology Institute, Department of GeneralEducation, Nagoya University, 1 Furo-cho, Chikusa-ku, Nagoya,464 Japan. ³ Present address: Graduate School of Integrated Science, YokohamaCity University, 22-2, Seto, Kanazawa-ku, Yokohama, 236 Japan.     

Effect of Nasal Dilators on Perceived Odor Intensity

Subjects wearing nasal dilators rated olfactory stimuli as beingmore intense compared with ratings done without nasal expansion.The results support a perceptual constancy model in olfaction.Chem. Senses 22: 177–180, 1997. ¹Present address: Biology Department, St Lawrence UniversityCanton, NY 13617, USA ²Present address: PO Box 802, Drew University, Madison, NJ 07940,USA     

Zooplankton growth rates: the larvaceans Appendicularia, Fritillaria and Oikopleura in tropical waters

The growth rates of Appendicularia sicula, Fritillaria borealissargassi, Fritillaria haplostoma, Oikopleura dioica and Oikopleuralongicauda were determined from microcosms incubated in situat 23C in Jamaican waters. Experiments were conducted fromoligotrophic offshore waters, through mesotrophic Lime Cay andeutrophic Kingston Harbour in both natural and nutrient-enhancedphytoplankton communities. Length-weight relationships werecalculated for two of these species: O.longicauda log W=2.47log TL –6.10 and F.haplostoma log W=2.44 log TL –7.37,where weight (W) is in micrograms and trunk length (TL) is inmicrometres. Instantaneous growth rates averaged 1.7–2.5day^–1 for the five species and were observed as high as3.3 day^–1 These instantaneous rates are equivalent todaily specific growth rates averaging 4.6–11.4 and rangingup to 28. In larger genera, growth rates were related positivelyto picoplankton and nanoplankton concentration, and negativelyto the biomass of larvaceans, but in the smallest species growthwas unrelated to these factors. However, because the variabilityin these two factors within microcosms exceeded their naturalrange of variability, growth rates of larvaceans may normallybe unlimited by resources or population density effects. ¹Present address :Monterey Bay Aquarium Research Institute 7700Sandholdt Road, Moss Landing, CA 95039-0628, USA ²Present address :Bedford Institute of Oceanography PO Box 1006,Dartmouth, Nova Scotia B2Y 4A2, Canada     

The effect of Gymnema sylvestre extracts on the sweetness of eight sweeteners

Although numerous experiments have demonstrated the sweetness-inhibitingeffects of Gymnema sylvestre extracts, no human psychophysicalstudies have been done to quantitatively assess G.sylvestre'seffects across a set of natural and intensive sweeteners. Thepresent study evaluated the sweetness-inhibiting effects ofG.sylvestre extracts on three concentrations each of acesulfameK, aspartame, sodium cyclamate, fructose, glucose, sucrose,stevioside and xylitol. Subjects made sweetness judgements ofthe stimuli following pretreatment with either distilled water,commercial tea or G.sylvestre extracts. Gymnema sylvestre pretreatmentreduced the sweetness of the stimuli by an average of 77% withno evidence for a differential effect across sweeteners. Thepercentage reduction in sweetness was constant across the low,medium and high concentrations of the sweeteners. Kinetic plotsof the data fit the Michelis-Menten model for non-competitiveinhibition, but statistical results did not permit competitiveor uncompetitive mechanisms to be ruled out. A receptor occupancy/blockingmechanism is unlikely. The results support disruption of a moregeneral aspect of sweetness transduction and fit a type of ‘mixed’inhibition involving an effect on the breakdown of the stimulus/receptorcomplex. Inhibition of a later step in a sequential-step transductionsystem and/or a change in the physicochemistry of the environmentof the stimulus/receptor complex are possible. ²Present address: Department of Chemistry, Clark University,Worcester, MA 01610, USA. ³Present address: Department of Psychology, University of Rochester,Rochester, NY 14627, USA     

A Mutant of Arabidopsis thaliana That Defines a New Locus for Glycine Decarboxylation

A novel photorespiratory mutant of Arabidopsis thaliana, designatedgld2, was isolated based on a growth requirement for abnormallyhigh levels of atmospheric CO₂. Photosynthetic CO₂ fixationwas inhibited in the mutant following illumination in air butnot in atmosphere containing 2% O₂. Photosynthetic assimilationof ¹⁴CO₂ in an atmosphere containing 50% O₂ resulted in accumulationof 48% of the soluble label in glycine in the mutant comparedto 9% in the wild type. The rate of glycine decarboxylationby isolated mitochondria from the mutant was reduced to 6% ofthe wild type rate. In genetic crosses, the mutant complementedtwo previously described photorespiratory mutants of A. thalianathat accumulate glycine during photosynthesis in air due todefects in glycine decarboxylase (glyD, now designated gld1)and serine transhydroxymethylase (stm). Because glycine decarboxylaseis a complex of four enzymes, these results are consistent witha mutation in a glycine decarboxylase subunit other than thataffected in the gld1 mutant. The two gld loci were mapped tochromosomes 2 and 5, respectively. ³Present address: Department of Crop and Soil Sciences, MichiganState University, East Lansing, MI 48824, U.S.A. ⁴Present address: Department of Applied Bioscience, Facultyof Agriculture, Hokkaido University, Kita-Ku, Sapporo, 060 Japan ⁵Present address: Department of Biology, Carnegie Institutionof Washington, 290 Panama Street, Standford, CA 94305, U.S.A.     

Folylpolyglutamate Derivatives of Pisum sativum L. Determination of Polyglutamate Chain Lengths by High Performance Liquid Chromatography Following Conversion to p-aminobenzoylpolyglutamates

The folypolyglutamate derivatives of pea seedlings (Pisum sativumL. cv. Homesteader) were extracted in the presence of 2-mercaptoethanoland cleaved to p-aminobenzoylpolyglutamates by treatment withZn-HCl. Azo dyes were formed by reaction with naphthylethylenediamine and purified by polyacrylamide gel chromatography. p-Aminobenzoylpolyglutamateswere regenerated from these dyes by Zn treatment and then concentratedin vacuo. These derivatives were separated according to glutamylchain length by high performance liquid chromatography on WhatmanPartisil SAX columns. The folylpolyglutamates of 4 day old peacotyledons, pea leaves and isolated chloroplasts were mainlytetra- and pentaglutamates. These and folates of shorter chainlength were labelled when seeds and aerial shoots were incubatedwith p-aminobenzoate-[¹⁴C]. Labelling of the pentaglutamatewas reduced in seeds that were imbibed in the presence of 0.1mM methotrexate. Studies of cotyledon folylpolyglutamate synthetaseshowed that polyglutamate chain length was affected by incubationtime and the concentration of tetra-hydrofolate monoglutamatein the reaction system. ¹Present address: Department of Biology, University of Lethbridge,Alberta, Canada T1K 3M4 ²Present address: Department of Horticulture, Xiong-yue AgriculturalCollege, Xiong-yue, Liaoning Province, China (Received August 4, 1989; Accepted December 5, 1989)     

The impact of short-term exposure to UV-B radiation on zooplankton communities in north temperate lakes

We exposed natural zooplankton communities to in situ levelsof sunlight for 3 days at different depths in two north temperatelakes: one oligotrophic and one eutrophic. Natural fluxes ofUV-B radiation (280–320 nm) were manipulated with cutofffilters (Mylar®). There was substantial mortality in someof the zooplankton exposed to UV-B in the oligotrophic lake,but not in the eutrophic lake. Reproduction of Diaptomus wassuppressed by UV-B down to 6 m in the oligotrophic lake. Thesedata suggest that natural levels of UV-B radiation in the oligotrophiclake may prevent some species of zooplankton from continuouslyexploiting the warm surface waters during summer stratification.In the more eutrophic lake, UV-B is a less important constraintin the vertical distribution of zooplankton. These differencesin the responses of zooplankton to natural UV-B radiation inlakes may alter their ecological interactions with food resources,predators and other environmental variables in the water column. ¹Present address: Universidad Nacional del Comahue, Centro RegionalUniversitario Bariloche, CC 1336, (8400) Bariloche, Argentina ²Present address: National Academy of Engineering, 2101 ConstitutionAvenue, NW, Washington, DC 20418, USA