bluuebunny/crossref_metadata_2025 huggingface dataset:
TRACKING LONG‐TERM CHANGES IN CLIMATE USING ALGAL INDICATORS IN LAKE SEDIMENTS
Authors: Smol John P. , Cumming Brian F.
Published: March 2003

Interest in climate change research has taken on new relevance with the realization that human activities, such as the accelerated release of the so‐called greenhouse gases, may be altering the thermal properties of our atmosphere. Important social, economic, and scientific questions include the following. Is climate changing? If so, can these changes be related to human activities? Are episodes of extreme weather, such as droughts or hurricanes, increasing in frequency? Long‐term meteorological data, on broad spatial and temporal scales, are needed to answer these questions. Unfortunately, such data were never gathered; therefore, indirect proxy methods must be used to infer past climatic trends. A relatively untapped source of paleoclimate data is based on hindcasting past climatic trends using the environmental optima and tolerances of algae (especially diatoms) preserved in lake sediment profiles. Paleophycologists have used two approaches. Although still controversial, attempts have been made to directly infer climatic variables, such as temperature, from past algal assemblages. The main assumption with these types of analyses is that species composition is either directly related to temperature or that algal assemblages are related to some variable linearly related to temperature. The second more commonly used approach is to infer a limnological variable (e.g. water chemistry, lake ice cover, etc.) that is related to climate. Although paleolimnological approaches are broadly similar across climatic regions, the environmental gradients that paleophycologists track can be very different. For example, climatic inferences in polar regions have focused on past lake ice conditions, whereas in lakes near arctic treeline ecotones, paleophycologists have developed methods to infer past lakewater‐dissolved organic carbon, because this variable has been linked to the density of coniferous trees in a drainage basin. In closed‐basin lakes in arid and semiarid regions, past lakewater salinity, which can be robustly reconstructed from fossil algal assemblages, is closely tied to the balance of evaporation and precipitation (i.e. drought frequency). Some recent examples of paleophycolgical work include the documentation of striking environmental changes in high arctic environments in the 19th century believed to be related to climate warming. Meanwhile, diatom‐based reconstructions of salinity (e.g. the Great Plains of North America and Africa) have revealed prolonged periods of droughts over the last few millennia that have greatly exceeded those recorded during recent times. Marked climatic variability that is outside the range captured by the instrumental record has a strong bearing on sustainability of human societies. Only with a long‐term perspective can we understand natural climatic variability and the potential influences of human activities on climate and thereby increase our ability to understand future climate.
Immunolocalization and distribution of form ii rubisco in the pyrenoid and chloroplast stroma of amphidinium carterae and form i rubisco in the symbiont‐derived plastids of peridinium foliaceum (dinophyceae)
Authors: Jenks Andrée , Gibbs Sarah P.
Published: March 2003

Chloroplasts of peridinin‐containing dinoflagellates have recently been shown to contain Form II Rubisco, which consists of large subunits only and is coded by nuclear genes. We have used immunoelectron microscopy to determine the distribution of Form II and Form I Rubisco in dinoflagellates. In sections of Amphidinium carterae Hulburt, the pyrenoid was intensely labeled and the rest of the chloroplast moderately labeled by antisera to Form II Rubisco from the purple non‐sulfur bacterium Rhodospirillum rubrum and the symbiotic dinoflagellate Symbiodinium sp. No labeling was observed when sections were exposed to antiserum against Form I Rubisco of the haptophyte alga Isochrysis galbana. In contrast, cell sections of the dinoflagellate Peridinium foliaceum (Stein) Biecheler, whose chloroplasts belong to a diatom endosymbiont, showed no labeling with the two antisera against Form II Rubisco, but heavy pyrenoid labeling was present after treatment with antiserum against Form I Rubisco of I. galbana. The same immunolabeling results were obtained with the free‐living diatom Phaeodactylum tricornutum Bohlin. Volumetric analysis of the distribution of Form II Rubisco in the chloroplast of A. carterae showed that, in cells grown under moderate photon irradiance, 72.9% of the plastid's Rubisco was localized in the pyrenoid, whereas in cells grown under low irradiance only 37.0% of the Rubisco was found in the pyrenoid. This light‐induced concentration of Rubisco in the pyrenoid suggests that a CO2–concentrating mechanism may elevate CO2 within the pyrenoid, favoring the efficient fixation of CO2 by pyrenoid Rubisco.
PSEUDONEOCHLORIS MARINA(CHLOROPHYTA), A NEW COCCOID ULVOPHYCEAN ALGA, AND ITS PHYLOGENETIC POSITION INFERRED FROM MORPHOLOGICAL AND MOLECULAR DATA
Authors: Watanabe Shin , Himizu Atsumi , Lewis Louise A. , Floyd Gary L. , Fuerst Paul A.
Published: March 2003

Ultrastructural and molecular sequence data were used to assess the phylogenetic position of the coccoid green alga deposited in the culture collection of the University of Texas at Austin under the name ofNeochlorissp. (1445). This alga has uninucleate vegetative cells and a parietal chloroplast with pyrenoids; it reproduces by forming naked biflagellate zoospores. Electron microscopy revealed that zoospores have basal bodies displaced in the counterclockwise absolute orientation and overlapped at their proximal ends. Four microtubular rootlets numbering 2 and 2/1 are alternatively arranged in a cruciate pattern. A system I fiber extends beneath each d rootlet and a system II fiber (rhizoplast) originates from each basal body and extends peripherally along each d rootlet. These features differ substantially from those of the three genera,Ettlia(Komárek) Deason et al.,Neochloris(Starr) Deason et al., andParietochlorisWatanabe et Floyd, all of which were previously accommodated in the single genusNeochlorisStarr. Sequence data from the nuclear small subunit ribosomal RNA gene were obtained and compared with published green algal sequences. Results from the ultrastructural and sequence data support the placement ofNeochlorissp. (The Culture Collection of Algae at the University of Texas at Austin [UTEX] no. 1445) in the Ulvophyceae. This isolate is described asPseudoneochloris marina, gen. et sp. nov. in the Ulotrichales, Ulvophyceae.
PRESENCE OF PHYCOERYTHRIN IN TWO STRAINS OF PROCHLOROCOCCUS (CYANOBACTERIA) ISOLATED FROM THE SUBTROPICAL NORTH PACIFIC OCEAN
Authors: Penno Sigrid , Campbell Lisa , Hess Wolfgang R.
Published: March 2003

Prochlorococcus is a ubiquitous marine oxyphotobacterium characterized by the presence of DV‐chl a and b. In addition, the type strain Prochlorococcus marinus Chisholm et al. CCMP 1375 (or SS120), an isolate from the Sargasso Sea, contains low levels of an unusual phycoerythrin. Until now, it has been unclear if phycoerythrin occurs randomly within this systematic group and if the molecular characteristics of this phycoerythrin are restricted to this single strain. Here, we show that two additional Prochlorococcus strains from the Pacific Ocean also contain similar low levels of phycoerythrin. DNA sequence and phylogenetic analyses demonstrated that this phycoerythrin is very similar to the phycoerythrin of P. marinus SS120 and differs from the classic cyanobacterial phycoerythrins. In contrast, a third isolate from the Arabian Sea lacks phycoerythrin. Based on the DV‐chl b:a ratio and 16S rRNA sequence data, we classify the two Pacific phycoerythrin‐containing isolates as low‐light‐adapted strains and the Arabian Sea isolate as a high‐light‐adapted strain. Thus, we provide further evidence to link the physiology of an individual genotype and the presence or absence of functional phycoerythrin genes within the genus Prochlorococcus.
DOMOIC ACID PRODUCTION IN NITZSCHIA SP. (BACILLARIOPHYCEAE) ISOLATED FROM A SHRIMP‐CULTURE POND IN DO SON, VIETNAM
Authors: Kotaki Yuichi , Koike Kazuhiko , Yoshida Makoto , Van Thuoc Chu , Huyen Nguyen Thi Minh , Hoi Nguyen Chu , Fukuyo Yasuwo , Kodama Masaaki
Published: March 2003

Domoic acid (DA), a neuroexcitatory amino acid, was detected in batch culture of the newly recognized species Nitzschia navis‐varingica Lundholm et Moestrup. The production of DA by this diatom was confirmed by electrospray ionization mass spectrometry. The diatom was collected from a shrimp‐culture pond in Do Son, Vietnam. The production of DA (1.7 pg·cell−1) is within the levels reported for Pseudo‐nitzschia multiseries (Hasle) Hasle. The DA production started during the late exponential growth phase and reached a maximum during the early stationary growth phase. Maximum DA levels in the axenic culture decreased to about half that of the nonaxenic culture (0.9 pg·cell−1 vs. 1.7 pg·cell−1), suggesting that DA production by the new species is influenced by bacteria.
AN ECOLOGICAL BASIS FOR EXTRACELLULAR CARBONIC ANHYDRASE IN MARINE UNICELLULAR ALGAE
Authors: Hobson Louis A. , Hanson Christine E. , Holeton Claire
Published: March 2003

Extracellular carbonic anhydrase (CAe) is expressed by many, but not all, autotrophic species of aquatic unicellular protists. We measured CAe activities in unicellular marine algae characteristic of either high nutrient spring, fall, and winter blooms or low nutrient summer populations to provide ecological/evolutionary information about the enzyme. Highest activities occurred in spring bloom and opportunistic diatoms exposed to long photoperiods (16 h) when pH was highest and CO2 was lowest. Lower activities were recorded for a fall‐bloom diatom exposed to the long photoperiod, and lowest values were found under all culture conditions for one diatom and a number of flagellated species typical of summer low nutrient environments. Other potential sources of variance in measurements of CAe activity were examined. Maximum activities of CAe were recorded for the diatom, Skeletonema costatum (Greville) Cleve, during late exponential phase of growth and within 8 h of the beginning of the photoperiod. We concluded that ecological factors are important in determining CAe activities in marine unicellular protists. Potential functions of CAe in the metabolism of marine unicellular algae are discussed.
EFFECTS OF UV‐B‐INDUCED DNA DAMAGE AND PHOTOINHIBITION ON GROWTH OF TEMPERATE MARINE RED MACROPHYTES: HABITAT‐RELATED DIFFERENCES IN UV‐B TOLERANCE
Authors: Van De Poll Willem H. , Eggert Anja , Buma Anita G. J. , Breeman Anneke M.
Published: March 2003

The sensitivity to UV‐B radiation (UVBR: 280–315 nm) was tested for littoral (Palmaria palmata[L.] O. Kuntze, Chondrus crispus Stackhouse) and sublittoral (Phyllophora pseudoceranoides S. G. Gmelin, Rhodymenia pseudopalmata[Lamouroux] Silva, Phycodrys rubens[L.] Batt, Polyneura hilliae[Greville] Kylin) red macrophytes from Brittany, France. Algal fragments were subjected to daily repeated exposures of artificial UVBR that were realistic for springtime solar UVBR at the water surface in Brittany. Growth, DNA damage, photoinhibition, and UV‐absorbing compounds were monitored during 2 weeks of PAR + UV‐A radiation (UVAR) + UVBR, whereas PAR + UVAR and PAR treatments were used as controls. The littoral species showed a higher UV tolerance than the sublittoral species. After 2 weeks, growth of P. palmata and C. crispus was not significantly affected by UVBR, and DNA damage, measured as the number of cyclobutane‐pyrimidine dimers per 106 nucleotides, was negligible. Photoinhibition, determined as the decline in optimal quantum yield, was low and decreased during the course of the experiment, coinciding with the production of UV‐absorbing compounds in these species. In contrast, no UV‐absorbing compounds were induced in the sublittoral species. Growth rates of P. pseudoceranoides and R. pseudopalmata were reduced by 40% compared with the PAR treatment. Additionally, constant levels of DNA damage and pronounced photoinhibition were observed after the UVBR treatments. Growth was completely halted for Phycodrys rubens and Polyneura hilliae, whereas DNA damage accumulated in the course of the experiment. Because Phycodrys rubens and Polyneura hilliae showed the same degree of photoinhibition as the other sublittoral species, it appears that the accumulation of DNA damage may have been responsible for the complete inhibition of growth. The results suggest an important role of DNA repair pathways in determining the UV sensitivity in red macrophytes.
EVOLUTION OF MACROCYSTIS SPP. (PHAEOPHYCEAE) AS DETERMINED BY ITS1 AND ITS2 SEQUENCES1,
Authors: Coyer James A. , Smith G. Jason , Andersen Robert A.
Published: March 2003

Macrocystis (Lessoniaceae) displays an antitropical distribution, occurring in temperate subtidal regions along western North America in the northern hemisphere and throughout the southern hemisphere. We used the noncoding rDNA internal transcribed spacer regions (ITS1 and ITS2) to examine relatedness among (1) Macrocystis and several genera of Laminariales, (2) four species of Macrocystis (M. integrifolia Bory from the northern hemisphere, M. angustifolia Bory and M. laevis Hay from the southern hemisphere, and M. pyrifera[L.] C. Ag. from both hemispheres), and (3) multiple clones of several individuals. Of the taxa included in our phylogenetic analysis, the elk kelp, Pelagophycus porra (Lem.) Setch., was the sister taxon to Macrocystis spp. Macrocystis individuals from the southern hemisphere (representing three species) formed a strongly to moderately supported clade, respectively, when the ITS1 and ITS2 sequences were analyzed separately. No distinction was detected between the two species in the northern hemisphere. Thus, Macrocystis may be a monospecific genus (M. pyrifera). A northern‐hemisphere‐to‐southern‐hemisphere pattern of dispersal was inferred, because northern‐hemisphere individuals were more diverse and displayed paraphyletic clades, whereas southern‐hemisphere individuals were less diverse and formed a monophyletic clade. High intraindividual variation in ITS1 sequences was observed in one individual from Santa Catalina Island (CA), suggesting very recent and rapid mixing of genotypes from areas to the north and Baja California (Mexico) or introgressive hybridization with Pelagophycus.
FOURIER TRANSFORM INFRARED SPECTROSCOPY AS A NOVEL TOOL TO INVESTIGATE CHANGES IN INTRACELLULAR MACROMOLECULAR POOLS IN THE MARINE MICROALGA CHAETOCEROS MUELLERII (BACILLARIOPHYCEAE)
Authors: Giordano Mario , Kansiz Mustafa , Heraud Philip , Beardall John , Wood Bayden , McNaughton Don
Published: March 2003

Fourier Transform Infrared (FT‐IR) spectroscopy was used to study carbon allocation patterns in response to changes in nitrogen availability in the diatom Chaetoceros muellerii Lemmerman. The results of the FT‐IR measurements were compared with those obtained with traditional chemical methods. The data obtained with both FT‐IR and chemical methods showed that nitrogen starvation led to the disappearance of the differences in cell constituents and growth rates existing between cells cultured at either high [NO3−] or high [NH4+]. Irrespective of the nitrogen source supplied before nitrogen starvation, a diversion of carbon away from protein, chlorophyll, and carbohydrates into lipids was observed. Under these conditions, cells that had previously received nitrogen as nitrate appeared to allocate a larger amount of mobilized carbon into lipids than cells that had been cultured in the presence of ammonia. All these changes were reversed by resupplying the cultures with nitrogen. The rate of protein accumulation in the N‐replete cells was slower than the rate of decrease under nitrogen starvation. This study demonstrates that the relative proportions of the major macromolecules contained in microalgal cells and their changes in response to external stimuli can be determined rapidly, simultaneously, and inexpensively using FT‐IR. The technique proved to be equally reliable to and less labor intensive than more traditional chemical methods.
MECHANISMS OF FLUID SHEAR‐INDUCED INHIBITION OF POPULATION GROWTH IN A RED‐TIDE DINOFLAGELLATE1
Authors: Juhl Andrew R. , Latz Michael I.
Published: March 2003

Net population growth of some dinoflagellates is inhibited by fluid shear at shear stresses comparable with those generated during oceanic turbulence. Decreased net growth may occur through lowered cell division, increased mortality, or both. The dominant mechanism under various flow conditions was determined for the red‐tide dinoflagellate Lingulodinium polyedrum (Stein) Dodge. Cell division and mortality were determined by direct observation of isolated cells in 0.5‐mL cultures that were shaken to generate unquantified fluid shear. Larger volume cultures were exposed to quantified laminar shear in Couette‐flow chambers (0.004–0.019 N·m−2 shear stress) and to unquantified flow in shaken flasks. In these larger cultures, cell division frequency was calculated from flow cytometric measurements of DNA·cell−1. The mechanism by which shear inhibits net growth of L. polyedrum depends on shear stress level and growth conditions. Observations on the isolated cells showed that shaking inhibited growth by lowering cell division without increased mortality. Similar results were found for early exponential‐phase cultures exposed to the lowest experimental shear stress in Couette‐flow chambers. However, mortality occurred when a late exponential‐phase culture was exposed to the same low shear stress and was inferred to occur in cultures exposed to higher shear stresses. Elevated mortality in those treatments was confirmed using behavioral, morphological, and physiological assays. The results predict that cell division in L. polyedrum populations will be inhibited by levels of oceanic turbulence common for near‐surface waters. Shear‐induced mortality is not expected unless shear‐stress levels are unusually high or when cellular condition resembles late exponential/stationary phase cultures.
EFFECTS OF LIGHT ON PHOTOSYNTHESIS, GRAZING, AND POPULATION DYNAMICS OF THE HETEROTROPHIC DINOFLAGELLATE PFIESTERIA PISCICIDA (DINOPHYCEAE)1
Authors: Feinstein Timothy N. , Traslavina Ryan , Sun Ming‐Yi , Lin Senjie
Published: March 2003

In studying how environmental factors control the population dynamics of Pfiesteria piscicida Steidinger et Burkholder, we examined the influence of light regime on kleptoplastidic photosynthesis, growth, and grazing. Prey (Rhodomonas sp.)‐saturated growth rate of P. piscicida increased (0.67 ± 0.03 d−1 to 0.91 ± 0.11 d−1) with light intensity varying from 0 to 200 μmol photons·m−2·s−1. No significant effect was observed on grazing, excluding the possibility that light enhanced P. piscicida growth through stimulating grazing. Light‐grown P. piscicida exhibited a higher gross growth efficiency (0.78 ± 0.10) than P. piscicida incubated in the dark (0.32 ± 0.16), and photosynthetic inhibitors significantly decreased growth of recently fed populations. These results demonstrate a role of kleptoplastidic photosynthesis in enhancing growth in P. piscicida. However, when the prey alga R. sp. was depleted, light's stimulating effect on P. piscicida growth diminished quickly, coinciding with rapid disappearance of Rhodomonas‐derived pigments and RUBISCO from P. piscicida cells. Furthermore, the effect of light on growth was reversed after extended starvation, and starved light‐grown P. piscicida declined at a rate significantly greater than dark‐incubated cultures. The observed difference in rates of decline appeared to be attributable to light‐dependent cannibalism. Using a 5‐chloromethylfluorescein diacetate staining technique, cannibalistic grazing was observed after 7 days of starvation, at a rate four times greater under illumination than in the dark. The results from this study suggest that kleptoplastidy enhances growth of P. piscicida only in the presence of algal prey. When prey is absent, P. piscicida populations may become vulnerable to light‐stimulated cannibalism.
A SURVEY OF THE STEROL COMPOSITION OF THE MARINE DINOFLAGELLATES KARENIA BREVIS, KARENIA MIKIMOTOI, AND KARLODINIUM MICRUM: DISTRIBUTION OF STEROLS WITHIN OTHER MEMBERS OF THE CLASS DINOPHYCEAE1
Authors: Leblond Jeffrey D. , Chapman Peter J.
Published: March 2003

The sterol composition of different marine microalgae has been examined to determine the utility of sterols as biomarkers to distinguish members of various algal classes. For example, members of the class Dinophyceae possess certain 4‐methyl sterols, such as dinosterol, which are rarely found in other classes of algae. The ability to use sterol biomarkers to distinguish certain dinoflagellates such as the toxic species Karenia brevis Hansen and Moestrup, responsible for red tide events in the Gulf of Mexico, from other species within the same class would be of considerable scientific and economic value. Karenia brevis has been shown by others to possess two major sterols, (24S)‐4α‐methyl‐5α‐ergosta‐8(14),22‐dien‐3β‐ol (ED) and its 27‐nor derivative (NED), having novel structures not previously known to be present in other dinoflagellates. This prompted the present study of the sterol signatures of more than 40 dinoflagellates. In this survey, sterols with the properties of ED and NED were found in cultures of K. brevis and shown also to be the principal sterols of Karenia mikimotoi Hansen and Moestrup and Karlodinium micrum Larsen, two dinoflagellates closely related to K. brevis. They are also found as minor components of the more complex sterol profiles of other members of the Gymnodinium/Peridinium/Prorocentrum (GPP) taxonomic group. The distribution of these sterols is consistent with the known close relationship between K. brevis, K. mikimotoi, and K. micrum and serves to limit the use of these sterols as lipid biomarkers to a few related species of dinoflagellates.
TROPHIC INTERACTIONS IN THE SEA: AN ECOLOGICAL ROLE FOR CLIMATE RELEVANT VOLATILES?1
Authors: Steinke Michael , Malin Gill , Liss Peter S.
Published: March 2003

When attacked by herbivores, land plants can produce a variety of volatile compounds that attract carnivorous mutualists. Plants and carnivores can benefit from this symbiotic relationship, because the induced defensive interaction increases foraging success of the carnivores, while reducing the grazing pressure exerted by the herbivores on the plants. Here, we examine whether aquatic phytoplankton use volatile chemical cues in analogous tritrophic interactions. Marine algae produce several classes of biogenic gases such as non‐methane hydrocarbons, organohalogens, ammonia and methylamines, and dimethylsulfide. The grazing‐induced release of marine biogenic volatiles is poorly understood, however, and its effect on the chemical ecology of plankton and the foraging behavior of predators is essentially unknown. We outline grazing‐induced defenses in algae and highlight the biogenic production of volatiles when phytoplankton are attacked by herbivores. The role of chemical signaling in marine ecology presents several possible avenues for future research, and we believe that progress in this area will result in better understanding of species competition, bloom development, and the structuring of food webs in the sea. This has further implications for biogeochemical cycles, because several key compounds are emitted that influence the chemistry of the atmosphere and global climate.
HOW CRITICAL IS THE CRITICAL N:P RATIO?1
Authors: Flynn Kevin J.
Published: March 2003

The value of cellular N:P that corresponds to co‐limitation by N and P, the critical (Rcrit) or optimum ratio, has been used to infer the competitive advantage of phytoplankton growing in P‐impoverished systems. Using a revised quota model, with a normalized quota function and capable of simulating surge transport, the interactions between the minimum P‐quota (PCo), the shape of the P‐quota–cell growth relationship (affected by constantKQP), and transport kinetics in affecting the utility ofRcritare considered. For a lowPCoto endow an organism with a highRcritover a wide range of growth rates, the P‐quota curve must be more hyperbolic (KQPlow) rather than linear (KQPhigh).PCoandKQPalso affect the half saturation constant for growth,KgP ; this and the capacity to transport nutrients at rates above those required to sustain steady‐state growth endows a competitive advantage. However, the kinetics of transport into the organism have a greater potential for affectingKgPthan changing the kinetics of internal P usage. Thus, the value ofRcritis not a critical factor affecting competition except in extreme oligotrophic conditions. For competition between species, nutrient transport, accumulation, and resource utilization are all important. However, the efficiency of internal resource utilization is of lesser importance, and certainly not of greater importance, than resource acquisition. Multinutrient models intended to describe competition need to recognize these interactions; the traditional quota model is poorly equipped to do so.
ISOLATION OF DI(HYDROXYMETHYL)DIHYDROXYPYRROLIDINE FROM THE CYANOBACTERIAL GENUS CYLINDROSPERMUM THAT EFFECTIVELY INHIBITS DIGESTIVE GLUCOSIDASES OF AQUATIC INSECTS AND CRUSTACEAN GRAZERS1
Authors: Jüttner Friedrich , Wessel Hans Peter
Published: March 2003

An effective glucosidase inhibitor was isolated from the cyanobacterial genus Cylindrospermum. Its chemical structure was determined by MS and NMR spectrometry to be di(hydroxymethyl)dihydroxypyrrolidine (DMDP; 2(R),5(R)‐bis‐(hydroxymethyl)‐3(R), 4(R)‐dihydroxypyrrolidine). Its identity was established by comparison with an authentic compound. All five species of Cylindrospermum investigated synthesized this compound but accumulated it to a different extent intracellularly. Particularly active producers were the axenic C. licheniforme (22 pmol·nmol chl a−1) and a monoxenic unknown species of Cylindrospermum that contained the maximum amount (159 pmol·nmol chl a−1). The major part of DMDP was found to be extracellular for all species investigated. The isolated compound inhibited digestive α‐ and β‐glucosidases isolated from crustacean zooplankton (IC50 19 and 49 nM, respectively). The bacterial 1‐deoxynojirimycin, which was used as a well‐studied reference glucosidase inhibitor, was less inhibitory (IC50 520 and 2190, respectively). Digestive enzymes of macrozoobenthos (chironomids, trichoptera, and ephemeroptera) were less sensitive to DMDP. The insect digestive β‐glucosidase was more effectively inhibited than the α‐glucosidase. Beside others, the ecological function of the glucosidase inhibitor may be the reduction of the digestibility of the cyanobacterium for grazers.
ENDOBACTERIA IN THE DIATOM PINNULARIA (BACILLARIOPHYCEAE). I. “SCATTERED ct‐NUCLEOIDS” EXPLAINED: DAPI–DNA COMPLEXES STEM FROM EXOPLASTIDIAL BACTERIA BORING INTO THE CHLOROPLASTS1,2
Authors: Schmid Anna‐Maria M.
Published: March 2003

A local strain of the pennate diatom Pinnularia cf. “nobilis” was investigated using cytochemistry and fluorescence and EM techniques. The regular perforation of the chloroplasts of P. “nobilis” and the lack of a typical diatom pyrenoid were confirmed at the ultrastructural level. Cavities and channels in the complex secondary plastid were found to harbor symbiotic bacteria, and their DNA elicited DAPI fluorescence. Wheat germ agglutinin, labeling bacteria walls, elicited a similar fluorescence pattern. Previous speculation that the apochlorotic DNA‐positive dots in the plastids of several Pinnularia species are “scattered ct‐nucleoids” is thus refuted. Bacteria were rod shaped and gram negative. They resided in the lumen of the endoplasmic reticulum (ER) during host interphase confined to the specialized ER compartment housing the secondary plastid, that is, to the space between the third and the fourth membrane profile, encircling the chloroplast. TEM images of chemically and cryofixed cells revealed that cavities resulted from the interaction of bacteria with the plastid according to the following sequence, alignment, attachment, deformation, and disintegration. This occurred without visible injury to the primary chloroplast envelope or the relict cell membrane of the reduced ancestral red alga that surrounds the chloroplast. The patterned arrangement of bacteria suggests recognition sites on the vestigial cell membrane, thought to interact with surface groups on the bacteria. The intimate association between bacteria and secondary plastid inside the common specialized ER cisterna suggests they form a functional unit. Comparison of thylakoid profiles, disrupted by bacteria in Pinnularia, with those disrupted by the pyrenoid in other pennate diatoms (e.g. Trachyneis) revealed a significant ultrastructural resemblance. No aposymbiotic Pinnularia cells were found at the sampling site.
Lipid Biomarker Analysis of the Toxic Dinoflagellate Pfiesteria Piscicida: Distribution of Sterols and Fatty Acids Within the Class Dinophyceae
Authors: Leblond J. D. , Chapman P. J.
Published: March 2003

Within US waters, regular blooms of harmful dinoflagellates occur in the Gulf of Mexico and Chesapeake Bay regions. Although the causes of blooms are not fully understood, events in Gulf of Mexico waters have been recorded for over 30 years, and are almost exclusively caused by the photosynthetic dinoflagellate, Karenia brevis. Conversely, blooms in the Chesapeake Bay region, caused by the heterotrophic dinoflagellate Pfiesteria piscicida, appear to be a relatively new phenomenon, and are hypothesized to be linked to an increase in nutrient‐rich runoff from chemical plants and livestock farms along tributaries leading into the Chesapeake. Despite the environmental, economic, and human health relevance of P. piscicida, there appears to be no published work on the characterization of its lipid composition. The objective of this study was, therefore to examine the sterol and fatty acid composition of cultured P. piscicida isolates as a precursor to eventual field studies of blooms of this organism. GC–MS analysis of trimethylsilyl ether derivatives of sterols in free sterol and sterol ester fractions revealed that the overwhelming majority of sterols was found as free sterols. Furthermore, free sterols were found to resemble those of other dinoflagellates, with the dominant compound being the common dinoflagellate sterol, dinosterol; a number of other 4‐methyl sterols common to other dinoflagellates were also identified. The fatty acids of P. piscicida were found to be primarily associated with a fraction containing cellular membrane phospholipids; small amounts of the recently described highly unsaturated fatty acids, octacosaoctaenoic acid [28 : 8(n‐3)] and octacosaheptaenoic acid [28 : 7(n‐6)], were observed in this fraction. The dominant fatty acid (approximately 40–60% of the phospholipid fatty acids) was docosahexaenoic acid [22 : 6(n‐3)]. Unlike K. brevis (see accompanying poster), P. piscicida does not appear to possess significant amounts of unusual sterols or fatty acids which may serve as potential biomarkers for this organism.
Sequence Diversity of the Gene tufA in Coleochaete: An Algal Model for Horizontal Gene Transfer
Authors: Ricker J. M. , Lewandowski J. D. , Delwiche C. F.
Published: March 2003

Studying the organellar gene transfer of tufA in Coleochaete serves as a model system for understanding the effect of functional horizontal gene transfer on sequence conservation and divergence. Previous work indicates that tufA, which codes for protein synthesis elongation factor TU, is encoded only in the chloroplast genome in most green algae, red algae, and glaucocystophytes, but only in the nuclear genome of embryophytes. In the charophytes, the lineage of green algae that gave rise to embryophytes, tufA is present variously within the chloroplast and/or nuclear genome. This implies that tufA was probably transferred to the nucleus from the chloroplast after the charophytes diverged from other green algae but before the diversification of the group. The chloroplast copy has undergone three separate fates within the charophytes: maintained in Charales, divergent in Coleochaetales, and lost in Zygnematales. Previous research indicates the presence of multiple nuclear copies and a highly divergent chloroplast encoded tufA in Coleochaete orbicularis. This research aims to isolate the chloroplast‐encoded tufA from a representative panel of Coleochaete in order to characterize patterns of conservation in the divergent chloroplast tufA. Putative chloroplast copies of tufA have been isolated through PCR and subsequent molecular cloning. By comparing the DNA sequences from copies of the chloroplast‐encoded tufA from a representative panel of Coleochaete, we hope to gain insight into patterns of sequence conservation and from this infer the current function of the divergent chloroplast tufA.
Functional Decline in Aging and Disease: A Role for Apoptosis
Authors: Joaquin Arnel M. , Gollapudi Sastry
Published: March 2003

The process of aging and senescence is associated with a decline in several organ functions and ultimately takes away independence and reduces quality of life. The precariously marginal functional reserves of the immune, pulmonary, and cardiovascular systems are among the most important causes of increased hospitalization in the older population. When complicated by chronic diseases, as is often the case, the problem is magnified. Apoptosis, or programmed cell death, is a process that goes on continuously throughout life. It is involved in embryogenesis for proper organ and tissue development. After birth and through adulthood, it helps eliminate unneeded and damaged cells. There is evidence that advanced age is associated with dysregulation of apoptosis. Several studies have shown age‐related changes in the levels of proteins and factors that regulate apoptosis. This could explain the age‐associated increased prevalence of cancers, certain autoimmune diseases, and neurodegenerative disorders in older people. More studies are needed to further elucidate the process of apoptosis. With this knowledge, the use of gene therapy and apoptosis modulators may someday have therapeutic value in preventing the functional decline we see in the older population.
High Vitamin E Plasma Levels and Low Low‐Density Lipoprotein Oxidation Are Associated with the Absence of Atherosclerosis in Octogenarians
Authors: Cherubini Antonio , Zuliani Giovanni , Costantini Fabrizio , Pierdomenico Sante D. , Volpato Stefano , Mezzetti Andrea , Mecocci Patrizia , Pezzuto Salvatore , Bregnocchi Mario , Fellin Renato , Senin Umberto ,   and the VASA Study Group
Published: March 2003

OBJECTIVES: To identify the biological characteristics of older subjects with vascular successful aging (VASA), defined as the absence of instrumental signs and clinical symptoms of atherosclerosis in the extracoronary and coronary vessels.

DESIGN: A cross‐sectional study.

SETTING: A university‐affiliated outpatient clinic.

PARTICIPANTS: Sixty older subjects (30 with VASA and 30 controls with moderate carotid atherosclerosis (AG group)) from a sample of 705 subjects age 75 and older consecutively screened.

MEASUREMENTS: Clinical examination; ultrasonographic examination of carotid, vertebral, abdominal aortic, iliac, and femoral arteries; electrocardiogram; and laboratory evaluation (lipid profile, lipophilic antioxidants, and markers of low‐density lipoprotein (LDL) oxidation).

RESULTS: Compared with controls, there were more females in the VASA group (82% vs 50%, P < .01), and fewer previous smokers (20.5% vs 52.5%, P < .01). Vitamin E/total cholesterol levels both in plasma (4.81 vs 3.51 μmol/mmol, P < .001) and in isolated LDLs (2.71 vs 1.86 μg/mg LDL cholesterol (LDL‐C), P < .01), were higher in the VASA group, as was the resistance of LDLs to in vitro oxidation (as indicated by a longer duration of the lag phase: 80.2 vs 65.6 minutes, P < .001). The level of fluorescent products of lipid peroxidation (FPLPs) in native LDLs was lower in the VASA group (13.5 vs 18.8 URF/mg LDL‐C, P < .001). Multivariate logistic regression analysis showed that only plasma vitamin E level (odds ratio (OR) = 6.04, 95% confidence interval (CI) = 1.48–24.63) and FPLPs in LDLs (OR = 0.53, 95% CI = 0.31–0.91) were independently associated with VASA.

CONCLUSIONS: These results suggest that an appropriate level of vitamin E and a low level of LDL oxidation might be important for reaching advanced age without developing atherosclerosis.
How Proxies Make Decisions about Research for Patients with Alzheimer's Disease
Authors: Sugarman Jeremy , Cain Carole , Wallace Roberta , Welsh‐Bohmer Kathleen A.
Published: March 2003

We examined the proxy decision‐making and informed consent processes for clinical research involving 49 patient‐subjects with dementia in an outpatient setting by performing serial in‐depth, structured, open‐ended telephone interviews. Interviews were tape recorded and transcribed. Transcripts were then coded and analyzed. Although in all cases proxy consent was obtained for research from a legally authorized representative, proxies reported considerable ambiguity regarding who made the decision to participate in research, or to what degree the decision was that of the proxy or of the patient. Reasons proxies gave for participating in research included: hope of direct or indirect benefits to the patient, caregiver, or patient's descendents; desperation; trust in the investigator; belief in the goodness of research; and altruism. These reasons varied according to the type of research. For instance, in drug trials hope of direct benefit prevailed; in studies not evaluating a potential therapy more altruistic concerns predominated. Being a proxy decision maker for research can be burdensome. The degree of burden related to making a decision to participate in research seems influenced by a number of intersecting factors, most importantly, the risk and nature of the study, the extent to which patients were able to participate in the decision, and the duration and severity of dementia. Proxy decision‐making concerning participation in research for patients with dementia can be a difficult task. The process might be improved by emphasizing that proxy consent is being sought because the nature of the patient's underlying medical condition can preclude the ability to make meaningful decisions. In addition, clinical researchers should recognize that giving proxy consent might place additional burdens on caregivers and discuss this explicitly when proxy consent is solicited.
Assistance with Personal Care Activities Among the Old‐Old in Israel: A National Epidemiological Study
Authors: Walter‐Ginzburg Adrian , Guralnik Jack M. , Blumstein Tzvia , Gindin Jacob , Baruch Modan
Published: March 2003

OBJECTIVES:

The objectives of this study were to (1) estimate rates of difficulty, need for assistance, and receipt of assistance with activities of daily living (ADLs) among the old‐old in Israel; (2) describe the living arrangements of the dependent old‐old; and (3) gain insight into the caregiving provided to the disabled members of this population.

DESIGN:

A random stratified sample of 1,820 subjects age 75 to 94 selected from the National Population Register (NPR), a complete listing of the Israeli population maintained by the Ministry of the Interior. The study sample consisted of Jews living in Israel on January 1, 1989, stratified by age (four 5‐year age groups: 75–79, 80–84, 85–89, 90–94), sex, and place of birth (Europe‐America, Middle East/North Africa, Israel).

SETTING:

National sample of old‐old Jewish Israelis.

PARTICIPANTS:

One thousand eight hundred twenty Israelis age 75 to 94 who were living in the community or in institutions at the time of the baseline interview.

MEASUREMENTS:

Participants' disability status was classified in terms of difficulty with, needing help with, and receiving help with any of five ADLs (washing/bathing, dressing, transferring, toileting, and eating). Only those receiving assistance from a person (as opposed to a device) were considered to be receiving help. The independent variables used included sociodemographic, health, and social network characteristics of the participants.

RESULTS:

Twenty‐one percent of those age 75 to 94 were found to be receiving personal assistance with at least one ADL. The most dependent were those age 90 to 94, women, those born in the Middle East or North Africa, and those living in an institution. Among those dependent in one or more ADLs, the overall community:institutionalized ratio was 2.4:1. Those who were dependent in three to five ADLs were about twice as likely to live in an institution as were those who were dependent in one or two ADLs. The Middle Eastern/North African born were more likely to be dependent, and at any given level of disability were more likely to be living in the community with a child and receiving the majority of their caretaking from the informal sector, primarily their family.

CONCLUSION:

We conclude that the families of disabled older people, particularly the Middle Eastern/North African born, provide a great deal of care for their older relatives despite the availability of a full range of services, providing no evidence of withdrawal of family care when state home and institutional care are available. This finding may imply underutilization of services, which should be investigated further to determine if it is caused by barriers to utilization or by the free choice of the disabled old‐old and their families.J Am Geriatr Soc 49:1176–1184, 2001.
Age‐Related Changes in the Flash Electroretinogram and Oscillatory Potentials in Individuals Age 75 and Older
Authors: Kergoat Hélène , Kergoat Marie‐Jeanne , Justino Lisette
Published: March 2003

OBJECTIVES:

To evaluate whether the inner plexiform layer of the retina is altered during senescence by examining the oscillatory potentials (OPs) of the flash electroretinogram (fERG) in individuals age 75 and older.

DESIGN:

Cross‐sectional, observational study.

SETTING:

A university‐based center.

PARTICIPANTS:

Fifty‐six healthy volunteers (age 20–88 years).

MEASUREMENTS:

fERGs and OPs were first evaluated in scotopic conditions, following pupillary dilation and dark adaptation, in young (20–32 years; n = 30) and older (75–88 years; n = 26) individuals. Electrical signals were recorded with a Dawson‐Trick‐Litzkow type (DTL) fiber electrode in response to blue and white flashes. Red flashes were subsequently delivered to the test eye for photopic fERG and OP recordings following a period of light adaptation.

RESULTS:

The amplitude of the a‐ and b‐waves in response to blue and white flashes was significantly decreased in older people and their implicit time was increased. The latency of the a‐ and b‐waves under photopic conditions was also prolonged with senescence, but only the amplitude of the b‐wave was reduced. The amplitude of most OPs recorded under both scotopic and photopic conditions decreased with age, whereas their implicit times were prolonged.

CONCLUSIONS:

Our results confirm previous findings regarding the age dependency of the fERG a‐ and b‐waves. Furthermore, we provide novel information concerning the detrimental effects of age on the OPs, indicating that the neuronal elements within the inner plexiform layer of the retina are compromised with senescence. J Am Geriatr Soc 49:1212–1217, 2001.
Five‐Year Survival of Older People with Anemia: Variation with Hemoglobin Concentration
Authors: Kikuchi Motoo , Inagaki Toshiaki , Shinagawa Nagao
Published: March 2003

OBJECTIVES: To investigate the significance of low hemoglobin concentration and longevity in older people.

DESIGN: Randomized prospective study.

SETTING: Nursing home and geriatric hospital ward in a metropolitan welfare center.

PARTICIPANTS: Apparently stable older residents from 1990 to 1996.

MEASUREMENTS: Survival rates were estimated by statistical analysis. Sixty‐three older subjects with low hemoglobin (Hb<11g/dl) and age/sex‐matched normal controls (Hb≥11g/dl) were observed for 60 months. Scores of activities of daily living (ADLs) did not significantly differ between the two groups. Cerebrovascular disease was the main complication in both, and malignant neoplasms were not apparent initially.

RESULTS: After 60 months, the 5‐year survival rate (FSR) of normal controls was significantly higher than that of cases with anemia (P = .0078). FSR was 67% in normal controls and 48% in anemic individuals age 70 to 79. The figures for individuals age 80 to 89 were 62% and 41%, respectively, and for individuals age 90 to 99 were 25% and 13%, respectively, the survival rate significantly decreasing with age in both groups (P < .001). FSR with severe anemia (Hb≤ 8.9g/dl) was 0% in males, and 27% in females. Values for moderate anemia (9.0g/dl to 10.9g/dl) were 25% and 51%, respectively, for normal hemoglobin (11.0g/dl to 12.9g/dl) were 44% and 61%, respectively, and for high hemoglobin (13.0g/dl≤Hb) were 50% and 70%, respectively. Advanced carcinomas were often detected at autopsy in anemic individuals. No death by cancer occurred in normal controls.

CONCLUSION: Low hemoglobin concentration predicts early death in nursing home residents. Anemia‐associated conditions that might be life‐threatening risks in older people require further investigation.
The Effect of Middle‐ and Old‐Age Body Mass Index on Short‐Term Mortality in Older People
Authors: Taylor Donald H. , Østbye Truls
Published: March 2003

OBJECTIVES:

To determine the effect of body mass index (BMI) at old age and at age 50 on short‐term survival among persons age 65 and older.

DESIGN:

Cross‐sectional, using the 4,791 respondents to the community interview of the 1994 National Long Term Care Survey (NLTCS).

SETTING:

United States of America.

PARTICIPANTS:

Persons age 65 and older who lived in community settings as of the 1994 NLTCS interview.

MEASUREMENTS:

Short‐term mortality was measured from the date of the 1994 NLTCS through year‐end 1995. BMI (kg/m2) (at three points: 1994 NLTCS, 1 year before, age 50) and all other variables, including three other modifiable risk factors known to be related to mortality—cigarette smoking, alcohol consumption, and exercise—were based on self‐report.

RESULTS:

Both the unadjusted and adjusted nadirs of mortality in relation to BMI at old age were found in older persons with a BMI between 30 and 34.9; this was true for males and females in all age groups. The highest mortality rates were found for older persons with very low BMI (<18.5). In contrast, BMI at age 50 was positively related to mortality, with those in the lowest BMI category (<18.5) at age 50 having the lowest mortality. Persons who were obese at age 50 and who were no longer obese at the 1994 NLTCS had lower mortality than persons with stable weight.

CONCLUSIONS:

Weight reduction by middle‐aged persons who are obese should be reinforced as a public health priority, because there is evidence that long‐term weight loss results in better short‐term survival. Further study of healthy older survivors to determine why they are not harmed by heavier weight in old age may provide useful insights into successful aging.J Am Geriatr Soc 49:1319–1326, 2001.