Energy allocation and life history strategy of the desert isopod H. reaumuri

Summary Population characteristics of the desert isopod H. reaumuri and its energy allocation during each penophase were investigated in the Negev desert, Israel.It was found that on the individual level, 52% of the energy is allocated to the prereproductive, and 48% to the reproductive phenophases. On the population level, only 10–23% is devoted to isopods which are involved in reproduction. Assuming that the energy allocation pattern in H. reaumuri is the consequence of its life history strategy, two unique evolutionary lines were suggested. One suggestion is the evolution of the family mode of life which increases the probability of the individual's survival. This is due to parental investment and co-operation between siblings. The other suggestion is the evolution of high energy utilization for burrowing, in order to solve the low and unpredictable nature of water resources in the desert.     

Significance of bacterial biomass in the nutrition of a freshwater isopod (Lirceus sp.)

The quantitative significance of bacterial biomass in the nutrition of detritivores remains equivocal. We have used tritiated thymidine to specifically label stable macromolecules in natural assemblages of sediment-associated and detritus-associated bacteria. This material was presented to the isopod (Lirceus sp.) and incorporation of bacterial biomass measured. The isopod incorporated roughly 1 ng bacterial carbon (mg wet wt.)^-1 h^-1 from leaf discs and about 6 ng mg^-1 h^-1 from sediment. Calculation of grazing rate from changes in cell counts yields grazing rates from 2.3–17.9 ng C mg^-1 h^-1. Even the maximum grazing rate, which is an overestimate of C assimilated, represents only 14.7% of C respired by the isopod.     

Pathogenic effect of entomopathogenic nematode-bacterium complexes on terrestrial isopods

In this study, we evaluated the effect of entomopathogenic nematodes (EPNs) Steinernema carpocapsae, Steinernema feltiae and Heterorhabditis bacteriophora, symbiotically associated with bacteria of the genera Xenorhabdus or Photorhabdus, on the survival of eight terrestrial isopod species. The EPN species S. carpocapsae and H. bacteriophora reduced the survival of six isopod species while S. feltiae reduced survival for two species. Two terrestrial isopod species tested (Armadillidium vulgare and Armadillo officinalis) were found not to be affected by treatment with EPNs while the six other isopod species showed survival reduction with at least one EPN species. By using aposymbiotic S. carpocapsae (i.e. without Xenorhabdus symbionts), we showed that nematodes can be isopod pathogens on their own. Nevertheless, symbiotic nematodes were more pathogenic for isopods than aposymbiotic ones showing that bacteria acted synergistically with their nematodes to kill isopods. By direct injection of entomopathogenic bacteria into isopod hemolymph, we showed that bacteria had a pathogenic effect on terrestrial isopods even if they appeared unable to multiply within isopod hemolymphs. A developmental study of EPNs in isopods showed that two of them (S. carpocapsae and H. bacteriophora) were able to develop while S. feltiae could not. No EPN species were able to produce offspring emerging from isopods. We conclude that EPN and their bacteria can be pathogens for terrestrial isopods but that such hosts represent a reproductive dead-end for them. Thus, terrestrial isopods appear not to be alternative hosts for EPN populations maintained in the absence of insects.     

Phenology and floral visitors of two sympatric Heliconia species in the Brazilian Atlantic forest

The main goal of the present study was to test if two sympatric species of Heliconia, Heliconia spathocircinata and Heliconia laneana var. flava, differ in their reproductive seasons and guilds of flower visitors. Twenty-four sampling sessions were conducted monthly between February 2001 and January 2003. Individuals of H. spathocircinata and of H. laneana var. flava were tagged within a transect of 4000×4 m. Reproductive phenophases (flowering, unripe, and ripe fruits) were recorded, and circular statistics were used to test for the regularity and frequency of phenophases. Flower visitors were observed during two flowering periods for each species. Both species had well-defined and synchronous reproductive periods, with a small overlap, suggesting a sequential flowering model. Biotic and abiotic factors seem to affect phenophases of both species. However, herbarium data suggest that the flowering period in H. spathocircinata varies less than in H. laneana, despite its wider geographic distribution. The hummingbird Phaethornis idaliae was the main floral visitor of both Heliconia species studied. H. laneana was also legitimately visited by another hummingbird species, Glaucis hirsuta, and by Lepidoptera. Some Lepidoptera, particularly the bee Trigona spinipes, were illegitimate visitors (‘nectar robbers’). We suggest that the flower of H. spathocircinata allowed a wider array of visitors, because it is bigger.     

Phenological response to climate change in China: a meta‐analysis

The change in the phenology of plants or animals reflects the response of living systems to climate change. Numerous studies have reported a consistent earlier spring phenophases in many parts of middle and high latitudes reflecting increasing temperatures with the exception of China. A systematic analysis of Chinese phenological response could complement the assessment of climate change impact for the whole Northern Hemisphere. Here, we analyze 1263 phenological time series (1960–2011, with 20+ years data) of 112 species extracted from 48 studies across 145 sites in China. Taxonomic groups include trees, shrubs, herbs, birds, amphibians and insects. Results demonstrate that 90.8% of the spring/summer phenophases time series show earlier trends and 69.0% of the autumn phenophases records show later trends. For spring/summer phenophases, the mean advance across all the taxonomic groups was 2.75 days decade^?1 ranging between 2.11 and 6.11 days decade^?1 for insects and amphibians, respectively. Herbs and amphibians show significantly stronger advancement than trees, shrubs and insect. The response of phenophases of different taxonomic groups in autumn is more complex: trees, shrubs, herbs and insects show a delay between 1.93 and 4.84 days decade^?1, while other groups reveal an advancement ranging from 1.10 to 2.11 days decade^?1. For woody plants (including trees and shrubs), the stronger shifts toward earlier spring/summer were detected from the data series starting from more recent decades (1980s–2000s). The geographic factors (latitude, longitude and altitude) could only explain 9% and 3% of the overall variance in spring/summer and autumn phenological trends, respectively. The rate of change in spring/summer phenophase of woody plants (1960s–2000s) generally matches measured local warming across 49 sites in China (R = ?0.33, P < 0.05).     

First record of Synidotea laevidorsalis (Miers, 1881) (Crustacea: Isopoda) in Europe (Gironde estuary,France)

This note reports on the presence of a well established population of the isopod Synidotea laevidorsalis (Miers) in the Gironde estuary (southwestern France). This species is new for the European fauna. S. laevidorsalis is a nonendemic cool-temperate to subtropical, shallow-water species which was probably introduced into the study area from Asia. In the salinity range of 1 to 10 g 1^-1 of the Gironde the species constitutes an important component of the brackish-water hyperbenthic community. The population was already present in 1975 when it was misidentified as the native species Idotea emarginata (Fabricius).     

Microplastic ingestion affects hydrogen production and microbiomes in the gut of the terrestrial isopod Porcellio scaber

Microplastic (MP) is an environmental burden and enters food webs via ingestion by macrofauna, including isopods (Porcellio scaber) in terrestrial ecosystems. Isopods represent ubiquitously abundant, ecologically important detritivores. However, MP-polymer specific effects on the host and its gut microbiota are unknown. We tested the hypothesis that biodegradable (polylactic acid [PLA]) and non-biodegradable (polyethylene terephthalate [PET]; polystyrene [PS]) MPs have contrasting effects on P. scaber mediated by changes of the gut microbiota. The isopod fitness after an 8-week MP-exposure was generally unaffected, although the isopods showed avoidance behaviour to PS-food. MP-polymer specific effects on gut microbes were detected, including a stimulation of microbial activity by PLA compared with MP-free controls. PLA stimulated hydrogen emission from isopod guts, while PET and PS were inhibitory. We roughly estimated 10⁷ kg year⁻¹ hydrogen emitted from the isopods globally and identified their guts as anoxic, significant mobile sources of reductant for soil microbes despite the absence of classical obligate anaerobes, likely due to Enterobacteriaceae-related fermentation activities that were stimulated by lactate generated during PLA-degradation. The findings suggest negative effects of PET and PS on gut fermentation, modulation of important isopod hydrogen emissions by MP pollution and the potential of MP to affect terrestrial food webs.     

Synthesis, characterization, and antibacterial activity of N,O-quaternary ammonium chitosan

N,N,N-Trimethyl O-(2-hydroxy-3-trimethylammonium propyl) chitosans (TMHTMAPC) with different degrees of O-substitution were synthesized by reacting O-methyl-free N,N,N-trimethyl chitosan (TMC) with 3-chloro-2-hydroxy-propyl trimethyl ammonium chloride (CHPTMAC). The products were characterized by ¹H NMR, FTIR and TGA, and investigated for antibacterial activity against Staphylococcus aureus and Escherichia coli under weakly acidic (pH 5.5) and weakly basic (pH 7.2) conditions. TMHTMAPC exhibited enhanced antibacterial activity compared with TMC, and the activity of TMHTMAPC increased with an increase in the degree of substitution. Divalent cations (Ba²⁺ and Ca²⁺) strongly reduced the antibacterial activity of chitosan, O-carboxymethyl chitosan and N,N,N-trimethyl-O-carboxymethyl chitosan, but the repression on the antibacterial activity of TMC and TMHTMAPC was weaker. This indicates that the free amino group on chitosan backbone is the main functional group interacting with divalent cations. The existence of 100 mM Na⁺ slightly reduced the antibacterial activity of both chitosan and its derivatives.     

Energetics of isopod populations in a forest of central Japan

Energetics of the populations of three isopods, Armadillidium vulgare, Porcellio scaber and Ligidium japonicum were studied in a warm-temperate evergreen broadleaved forest of Mt. Kiyosumi in central Japan. The study deals with age composition, survivorship curves, relations of body size to number of eggs or young, and mean growth curves of the populations. Respiratory rates, calorific values and food consumptions of the individual animals were determined in the laboratory. Population density of A. vulgare was highest of the three species, being about 350/m² in June 1966. The survivorship curve of the L. japonicum population was more close to L-type than the others. Average total biomass for populations of A. vulgare, P. scaber and L. japonicum were 3.3 kcal/m², 0.67 kcal and 0.43 kcal on the monthly basis, respectively. The energy of 35.2 kcal/m² was estimated to be assimilated by the A. vulgare population, 7.84 kcal by P. scaber and 6.91 kcal by L. japonicum during the period from October 1965 to September 1966. The relations between assimilation A and production P for fish, grasshopper and isopod populations were found to be expressed as A=aP^b. The values of the constant a for the fish, grasshopper and isopod populations seem to be in the range from 10 to 25, from 2 to 7 and from 4 to 8, respectively. Production efficiencies presented as P/A of A. vulgare, P. scaber and L. japonicum populations were estimated as 19.1%, 15.3% and 13.1%, respectively. The ecological efficiency represented as M/C of these isopod populations was estimated to be in the range from 7.6% to 11. 2%. Reproduction efficiency (Rp/P) of L. japonicum population was 20%, being the highest value of the three isopod species. This may be related to the L-type survivorship curve of L. japonicum population. Reproduction efficiency, relating closely to the age structure of the population, is important in the investigation of populations of animals, particularly those that have long life span.     

Design,synthesis, and biological properties of triazole derived compounds and their transition metal complexes

Triazole derived Schiff bases and their metal complexes (cobalt(II), copper(II), nickel(II), and zinc(II)) have been prepared and characterized using IR, ¹H and ¹³C NMR, mass spectrometry, magnetic susceptibility and conductivity measurements, and CHN analysis data. The structure of L², N-[(5-methylthiophen-2-yl)methylidene]-1H-1,2,4-triazol-3-amine, has also been determined by the X-ray diffraction method. All the metal(II) complexes showed octahedral geometry except the copper(II) complexes, which showed distorted octahedral geometry. The triazole ligands and their metal complexes have been screened for their in vitro antibacterial, antifungal, and cytotoxic activity. All the synthesized compounds showed moderate to significant antibacterial activity against one or more bacterial strains. It is revealed that all the synthesized complexes showed better activity than the ligands, due to coordination.     

Heavy water slows biological timing processes

Summary Deuterium oxide lengthens the period of the endogenous tidal activity rhythm of the sand-beach isopod, Excirolana chiltoni. Heavy water has also been shown to retard the circadian rhythm of deer mice, when added to the animals' drinking water. The average dosage dependence of the effect can be estimated with high precision for both isopod and mouse, and the two values are indistinguishable. A similar slowing of circadian rhythms, due to D₂O, has also been reported for an alga, a higher plant, two species of birds and three other rodents. Although data permitting reliable estimates of dosage dependence have not been published for these latter cases, the effect is apparently also of about the same magnitude. This evidence suggests fundamental similarities in the rhythmic mechanisms. Heavy water also produces a reversible slowing of several biological rhythms with periods in the millisecond range: the electric-organ discharge of a gymnotid fish (Stenarchus albifrons); the respiratory cycle of goldfish, as well as of an amphipod (Paraphoxus) and an isopod (Excirolana); and the cardiac cycle of a clam (Donax) and a crab (Emerita). Since these high-frequency rhythms originate in pacemakers dependent on diffusion processes, the experimental results suggest the possibility that long-period biological clocks are also based on diffusion-dependent pacemakers.Research initiated under grant GB 5471 from the National Science Foundation; publication supported, in part, by the Sea Grant Program under Grant GH 112 to the University of California, and in part by grant GB 23949 from the National Science Foundation. Dr. T. H. Bullock provided the Stenarchus used for the experiments of Fig. 4, and offered helpful experimental advice. Dr. H. Scheich and Mr. R. Hamstra gave valuable assistance with the experimental setup; my thanks to all three.     

Phenological responses to small-scale spatial variation in snowmelt timing reveal compensatory and conservative strategies in subarctic-alpine plants

Background: In tundra ecosystems, the adjustment of phenological events, such as bud burst, to snowmelt timing is crucial to the climatic adaptation of plants. Natural small-scale variations in microclimate potentially enable plant populations to persist in a changing climate.

Aims: To assess how plant phenology responds to natural differences in snowmelt timing.

Methods: We observed the timing of eight vegetative and reproductive phenophases in seven dwarf-shrub species in relation to differences in snowmelt timing on a small spatial scale in an alpine environment in subarctic Finland.

Results: Some species and phenophases showed accelerated development with later snowmelt, thus providing full or partial compensation for the shorter snow-free period. Full compensation resulted in synchronous occurrence of phenophases across the snowmelt gradient. In other species, there was no acceleration of development. The timing of phenophases varied between two consecutive years and two opposing mountain slope aspects.

Conclusions: The results have shown three distinct patterns in the timing of phenophases in relation to snowmelt and suggest alternative strategies for adaptation to snowmelt timing. These strategies potentially apply to other species and tundra ecosystems and provide a framework, enabling one to compare and generalise phenological responses to snowmelt timing under different future climate scenarios.     

Rapid Stimulation of EAAC1-Mediated Na+-Dependent l-Glutamate Transport Activity in C6 Glioma Cells by Phorbol Ester

Abstract: C6 glioma cells were used as a model system to study the regulation of EAAC1-mediated Na⁺-dependent l -[³H]glutamate transport. Although a 30-min preincubation with forskolin had no effect on transport activity, preincubation with phorbol 12-myristate 13-acetate (PMA) increased transport activity two- to threefold. PMA caused a time-dependent and concentration-dependent increase in EAAC1-mediated l -[³H]glutamate transport activity. A 2-min preincubation with PMA was sufficient to cause more than a twofold increase in transport activity and the protein synthesis inhibitor cycloheximide had no effect on the increase. These data suggest that this increase is independent of protein synthesis. The EC₅₀ value of PMA for stimulation of transport activity was 80 nM. Kinetic analyses demonstrated that the increase in transport activity was due to a 2.5-fold increase in V_max with no change in K_m. PMA also increased the transport of the nonmetabolizable analogue, d -[³H]aspartate to the same extent. In parallel assays, PMA did not, however, increase Na⁺-dependent glycine transport activity in C6 glioma. The inactive phorbol ester 4α-phorbol 12,13-didecanoate, did not stimulate l -[³H]glutamate transport activity, and the protein kinase C inhibitor chelerythrine blocked the stimulation caused by PMA. Okadaic acid and cyclosporin A, which are phosphatase inhibitors, had no effect on the stimulation of transport activity caused by PMA. The Ca²⁺ ionophore A23187 did not act synergistically to increase PMA stimulation. In previous studies, PMA caused a rapid increase in amiloride-sensitive Na⁺/H⁺ transport activity in C6 glioma. In the present study, pre- and coincubation with amiloride had no effect on the stimulation of transport activity caused by PMA. These studies suggest that activation of protein kinase C causes a rapid increase in EAAC1-mediated transport activity. This rapid increase in Na⁺-dependent l -[³H]-glutamate transport activity may provide a novel mechanism for protection against acute insults to the CNS.     

Phenology in central Europe – differences and trends of spring phenophases in urban and rural areas

In order to examine the impacts of both large-scale and small-scale climate changes (urban climate effect) on the development of plants, long-term observations of four spring phenophases from ten central European regions (Hamburg, Berlin, Cologne, Frankfurt, Munich, Prague, Vienna, Zurich, Basle and Chur) were analysed. The objective of this study was to identify and compare the differences in the starting dates of the pre-spring phenophases, the beginning of flowering of the snowdrop (Galanthus nivalis) and forsythia (Forsythia sp.), and of the full-spring phenophases, the beginning of flowering of the sweet cherry (Prunus avium) and apple (Malus domestica), in urban and rural areas. The results indicate that, despite regional differences, in nearly all cases the species studied flower earlier in urbanised areas than in the corresponding rural areas. The forcing in urban areas was about 4 days for the pre-spring phenophases and about 2 days for the full-spring phenophases. The analysis of trends for the period from 1951 to 1995 showed tendencies towards an earlier flowering in all regions, but only 22% were significant at the 5% level. The trends for the period from 1980 to 1995 were much stronger for all regions and phases: the pre-spring phenophases on average became earlier by 13.9 days/decade in the urban areas and 15.3 days/decade in the rural areas, while the full-spring phenophases were 6.7 days earlier/decade in the urban areas and 9.1 days/decade earlier in the rural areas. Thus rural areas showed a higher trend towards an earlier flowering than did urban areas for the period from 1980 to 1995. However, these trends, especially for the pre-spring phenophases, turned out to be extremely variable. Received: 21 October 1999 / Revised: 5 April 2000 / Accepted: 25 April 2000     

Neurochemical,pharmacological, and developmental studies on cerebellar receptors for dicarboxylic amino acids

Specific binding ofl-[³H]glutamate ([³H]Glu) andl-[³H]asparate ([³H]Asp) to cerebellar membranes represented a time-, temperature- pH- and protein-dependent interaction which was both saturable and reversible. Binding sites for both radioligands appeared maximally enriched in synaptosomal fractions isolated by gradient centrifugation. Kinetically derived dissociation constant (K _off/K _on=K _d) for [³H]Glu binding to this fraction indicated high-affinity (443 nM). Competition experiments employing analogs of excitatory amino acids, including new antagonists, helped identify binding sites for [³H]Glu and [³H]Asp as receptors with differential pharmacological, specificities. Membrane freezing reduced numbers of both receptor types, but binding activity could be recovered partially by incubation at 37°C. Glu receptors exhibited a pronounced deleterious sensitivity to thiol modifying reagents andl-Glu (50–1000 M) provided protection, against these compounds during co-incubation with cerebellar membranes. It is suggested that cold storage may induce partially reversible receptor inactivation by promoting sulfhydryl group/bond modification. Rat cerebellar glutamatergic function (endogenous Glu content, Glu uptake and receptor sites) exhibited an apparent ontogenetic peak between days 8–12 postpartum with a plateauing profile from day 30 to adulthood. The accelerated development (days 8–12) coincides with the first demonstrable Glu release and kainic acid neurotoxicity, as described previously.     

Isolation,characterisation of major secondary metabolites of the Himalayan Trichoderma koningii and their antifungal activity

Ethyl acetate extracts of two strains of Trichoderma koningii were evaluated for antifungal activity against soilborne pathogenic fungi, Rhizoctonia solani, Sclerotium rolfsii, Macrophomina phaseolina and Fusarium oxysporum by poisoned food technique. Secondary metabolites, namely δ-decanolactone, 6-pentyl-α-pyranone and 6-(4-oxopentyl)-2H-pyran-2-one were isolated from T. koningii (T-8) extract while palmitic acid, 6-pentyl-α-pyranone and stigmasterol were isolated from T. koningii (T-11) extract. Secondary metabolites were identified by ¹H NMR, ¹³C NMR and mass spectroscopic methods. These metabolites were evaluated for antifungal activity against the test pathogens 6-Pentyl-α-pyranone and 6-(4-oxopentyl)-2H-pyran-2-one exhibited excellent antifungal activity against S. rolfsii. The antifungal activity though slightly less was comparable to that of hexaconazole, a commercial fungicide.     

New development in the tritium labelling of peptides and proteins using solid catalytic isotopic exchange with spillover-tritium

Summary.  The mechanism of the reaction of high temperature solid state catalytic isotope exchange (HSCIE) of hydrogen in peptides with spillover-tritium at 140–180°C was analyzed. This reaction was used for preparing [³H]enkephalins such as [³H]DALG with specific activity of 138 Ci/mmol and [³H]LENK with specific activity of 120 Ci/mmol at 180°C. The analogues of [³H]ACTG_4–10 with specific activity of 80 Ci/mmol, [³H]zervamicin IIB with specific activity of 70 Ci/mmol and [³H]conotoxin G1 with specific activity 35 Ci/mmol were produced. The obtained preparations completely retained their biological activity. [³H]Peptide analysis using ³H NMR spectroscopy on a Varian UNITY-600 spectrometer at 640 MHz was carried out. The reaction ability of amino fragments in HSCIE was shown to depend both of their structures and on the availability and the mobility of the peptide chain. The reaction of HSCIE with the β-galactosidase from Termoanaerobacter ethanolicus was studied. The selected HSCIE conditions allow to prepare [³H] β-galactosidase with specific activity of 1440 Ci/mmol and completely retained its the enzymatic activity. Received November 30, 2001 Accepted January 31, 2002 Published online December 18, 2002 Acknowledgments The work was supported by the Russian Foundation for Basic Research, grant 01-04-48519a. Authors' address: Dr. Yurii A. Zolotarev, Institute of Molecular Genetics, Russian Academy of Sciences, pl. Kurchatova 2, 123182, Moscow, Russia, Fax: +7 (095) 196-0221, E-mail: zolya@img.ras.ru Abbreviations: HSCIE, the reaction of high temperature solid state catalytic isotope exchange; HS, hydrogen spillover; ³H NMR, tritium nuclear magnetic spectroscopy; CtxG1, conotoxin G1; AchR, acetylcholine receptor; HF, Hartree-Fock ab initio quantum-chemical calculation method     

Release of radiolabeled dopamine,p-tyramine,andm-tyramine from rat striatal slices by some aminotetralins

The effect of several 2-aminotetralins (2ATs) on the uptake and release of [¹⁴C] dopamine and [³H]m- or [³H]p-tyramine by rat striatal slices was examined. 6,7-Dihydroxy-2AT (6,7OHAT) and 5,6-dihydroxy-2-methyl-AT (5,6OHMeAT) were the most potent uptake inhibitors as well as the most potent releasers of the three labeled amines. The 5-, 6-, and 7-hydroxy-2-N,N-dipropyl-ATs (5-, 6-, and 7OHdiPrAT) and 5,6-dihydroxy-2-N,N-dipropyl-AT (5,6OHdiPrAT) significantly inhibited the uptakes of the three labeled amines, but they released only the tyramines. The dipropyl substitution of a 2AT appeared to confer a tyraminergic specificity to its release properties. To verify this supposition, 2AT was compared to 2-N,N-dipropyl-AT (diPrAT). Although 2AT released both [³H]p-tyramine and [¹⁴C]dopamine, diPrAT released only [³H]p-tyramine. None of the compounds, however, differentiated betweenm- andp-tyramine. It was concluded that the release of tyramines could be implicated in the actions of some of the 2ATs and that the tyramines can be transported independently from dopamine.     

Characterisation of the Binding of [3H]WAY-100635, a Novel 5-Hydroxytryptamine1A Receptor Antagonist, to Rat Brain

Abstract: The specific binding of [³H]WAY-100635 {N-[2-[4-(2-[O-methyl-³H]methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexane carboxamide trihydrochloride} to rat hippocampal membrane preparations was time, temperature, and tissue concentration dependent. The rates of [³H]WAY-100635 association (k₊₁ = 0.069 ± 0.015 nM^?1 min^?1) and dissociation (k_?1 = 0.023 ± 0.001 min^?1) followed monoexponential kinetics. Saturation binding isotherms of [³H]WAY-100635 exhibited a single class of recognition site with an affinity of 0.37 ± 0.051 nM and a maximal binding capacity (B_max) of 312 ± 12 fmol/mg of protein. The maximal number of binding sites labelled by [³H]WAY-100635 was ～36% higher compared with that of 8-hydroxy-2-(di-n-[³H]-propylamino)tetralin ([³H]8-OH-DPAT). The binding affinity of [³H]WAY-100635 was significantly lowered by the divalent cations CaCl₂ (2.5-fold; p < 0.02) and MnCl₂ (3.6-fold; p < 0.05), with no effect on B_max. Guanyl nucleotides failed to influence the K_D and B_max parameters of [³H]WAY-100635 binding to 5-HT_1A receptors. The pharmacological binding profile of [³H]WAY-100635 was closely correlated with that of [³H]8-OH-DPAT, which is consistent with the labelling of 5-hydroxytryptamine_1A (5-HT_1A) sites in rat hippocampus. [³H]WAY-100635 competition curves with 5-HT_1A agonists and partial agonists were best resolved into high- and low-affinity binding components, whereas antagonists were best described by a one-site binding model. In the presence of 50 µM guanosine 5′-O-(3-thiotriphosphate) (GTPγS), competition curves for the antagonists remained unaltered, whereas the agonist and partial agonist curves were shifted to the right, reflecting an influence of G protein coupling on agonist versus antagonist binding to the 5-HT_1A receptor. However, a residual (16 ± 2%) high-affinity agonist binding component was still apparent in the presence of GTPγS, indicating the existence of GTP-insensitive sites.     

Photosynthetic acclimation to different light levels in the brown marine macroalga, <Emphasis Type="Italic">Hizikia fusiformis</Emphasis> (Sargassaceae,Phaeophyta)

Hizikia fusiformis thalli experience dynamic incident light conditions during the period of growth. The present study was designed to examine how changing photon irradiance affects the photosynthesis both in the short and long terms by culturing H. fusiformis under three different light levels: 35 μmol photons m^-2 s^-1 (low light, LL), 85 μmol photons m^-2 s^-1 (intermediate light, IL), and 165 μmol photons m^-2 s^-1 (high light, HL). A similar relative growth rate was observed between IL- and HL-grown algae, but the growth rate was significantly reduced in LL-grown algae. The photosynthetic rates (P _n) measured at their respective growth light levels were found to be lowest in the thalli grown at LL and highest at HL. However, LL-grown algae exhibited much higher P _n in comparison with IL- and the HL-grown thalli at the same measuring photosynthetic photon flux density, indicating the photosynthetic acclimation to low growth light in H. fusiformis. The photosynthesis–light curves showed that LL-grown algae had a highest light-saturating maximum P _n (P _max) in comparison with IL- or HL-grown algae when the photosynthetic rates were expressed on the biomass basis. However, P _max was highest in HL-grown algae compared to IL- or LL-grown algae when the rates were normalized to chlorophyll a. The photosynthesis–inorganic carbon (Ci) response curves were also significantly affected by the growth light conditions. The highest value of apparent photosynthetic conductance occurred in LL-grown algae while the lowest value in HL-grown algae. Additionally, the activity of external carbonic anhydrase (CA) tended to increase while the total CA activity inclined to decrease in H. fusiformis thalli when the growth light level altered from 35 to 165 μmol photons per square meter per second. The external CA inhibitors showed a higher inhibition in HL-grown algae compared with LL-grown algae. It was proposed that photosynthetic acclimation to low light condition in H. fusiformis was achieved through an increase in the number of reaction centers and increased capacities of electron transport and of Ci transport within cells. The ability of photosynthetic acclimation to low light confers H. fusiformis thalli to overcome the environmental low light condition as a result of the attenuation of seawater or self-shading through enhancing its photosynthetic performance and carbon assimilation necessary for growth.