bluuebunny/crossref_metadata_2025 huggingface dataset:
Detergent‐resistant membrane fractions contribute to the total 1H NMR‐visible lipid signal in cells
Authors: Wright Lesley C. , Djordjevic Julianne T. , Schibeci Stephen D. , Himmelreich Uwe , Muljadi Nick , Williamson Peter , Lynch Garry W.
Published: December 2004

Leukocytes and other cells show an enhanced intensity of mobile lipid in their 1H NMR spectra under a variety of conditions. Such conditions include stimulation, which has recently been shown to involve detergent‐resistant, plasma membrane domains (DRMs) often called lipid rafts. As there is much speculation surrounding the origin of cellular NMR‐visible lipid, we analysed subcellular fractions, including DRMs, by NMR spectroscopy. We demonstrated that DRMs isolated by density gradient centrifugation from lymphoid (CEM‐T4, stimulated Jurkat cells), and monocytoid (THP‐1) cells produced NMR‐visible, lipid signals. Large scale subfractionation of THP‐1 cells determined that while cytoplasmic lipid droplets constituted much of the total NMR‐visible lipid, the contribution of DRMs was significant. Qualitative and quantitative lipid analyses revealed that DRMs and lipid droplets differed in their lipid composition. DRMs were enriched in cholesterol and ganglioside GM1, and contained relatively unsaturated fatty acids compared with the lipid droplets. Both lipid droplets and DRMs contained neutral lipids (triacylgycerols, cholesterol ester, fatty acids in THP‐1 cells) that could, in addition to phospholipids, contribute to the NMR‐visible lipid. The lipid droplets also exhibited different protein profiles and contained 500‐fold less protein than DRMs, confirming that DRMs and droplets were fractionated as separate entities. The NMR‐visible lipid in DRMs is therefore unlikely to be a contaminant from lipid droplets. We propose a micropartitioning of the NMR‐visible mobile lipid of whole cells between intracellular lipid droplets, where most of this lipid resides, and detergent‐resistant plasma membrane domains.
Variation in Male Calling Behaviour and Relation to Male Mating Success in the Strawberry Poison Frog (Dendrobates pumilio)
Authors: Pröhl Heike
Published: December 2004

Calling behaviour and the characteristics of the males’ call are important for mate attraction, female mate choice and male mating success in anurans. In this study I investigated the variation in calling activity and the variation in one spectral (dominant frequency) and four temporal properties (call rate, call duration, duty cycle and pulse rate) of the advertisement call of strawberry poison frogs, Dendrobates pumilio, in two Costa Rican populations during two study periods. Regarding all call properties, no differences were found between populations or years, but between‐male variation was significantly higher than within‐recording and within‐male variation. Dominant frequency was less variable within and among males than temporal call properties and I classified the former as static and the latter as intermediate properties of the call. No call property seemed to be strongly affected by body length or weight. Moreover, I used behavioural observations to relate male calling behaviour to mating success. Calling activity was more variable between males and accounted for more variability in mating success in multiple regression models than any call property. Some call properties (call rate, dominant frequency and pulse rate) were also related to male mating success in one or two study periods. These call properties are probably important for females during courtship to assess their prospective mate and/or for competitive male–male interactions. Furthermore, I compared call properties and mating success of some males for which data were available for both study periods. Pulse rate was lower in the second than in the first year, suggesting age‐related changes in this call property. Moreover, male D. pumilio increased their relative mating success from the first to the second study year. Together with other studies, the data of this study suggest that, in anurans, endurance rivalry contributes more to variation in male mating success than does female choice based on male characteristics.
Mutual Mate Assessment in Wolf Spiders: Differences in the Cues Used by Males and Females
Authors: Rypstra Ann L. , Wieg Christina , Walker Sean E. , Persons Matthew H.
Published: December 2004

When males engage in conspicuous courtship displays, it seems obvious that females would use characteristics of that display in mating decisions. However, males must also have a way to identify and evaluate females prior to engaging in what might be a costly mating ritual. Although it was known that female wolf spiders of the speciesPardosa milvina(Araneae; Lycosidae) attract males using volatile chemical cues, the nature of the cues used by males and females in mate selection had not been investigated. Specifically we determined whether males could detect the mating status of the female and if chemotactile cues from the female played a role in that process. In addition, we quantified conspicuous aspects of the male courtship (leg raises and body shakes) to determine if courtship intensity was related to female choice. Although repeated mating occurred in our studies, males were more likely to court and mate with virgin females. Males used substrate‐borne cues deposited by females to discriminate between mated and virgin females. Females used the conspicuous behaviors of males during courtship, body shakes and leg raises, in mate selection. Thus males and females use different kinds of information and different sensory modalities to assess the suitability of a potential mate.
Amarillo Fish (Girardinichthys multiradiatus) Use Visual Landmarks to Orient in Space
Authors: de Perera Burt T. , Macías Garcia C.
Published: December 2004

Fish responsiveness to visual stimuli has been studied extensively in contexts such as female mate choice, predator inspection and schooling, yet surprisingly little work has been conducted on visual orientation in space in fish. Here we report on an experiment designed to test whether Amarillo fish can learn to find a goal within a maze more effectively in the presence of local visual landmarks than otherwise. We found that: (a) Amarillo fish can use landmarks to locate a goal, (b) there was no observed difference in the ability to use visual landmarks between two populations and (c) overall navigational performance differed between two populations of Amarillo fish: individuals from a permanently turbid eutrophic pond performed better than those from a pond with clear waters. We hypothesize that fish that inhabit clear waters possess poorer navigational capabilities than fish from turbid waters because they normally rely on goal‐oriented behaviour, which requires neither egocentric nor environmental clues to navigate. This paper adds to the literature on the links between habitat characteristics and population differences in performance.
A Contrast in Extra‐Pair Paternity Levels on Mainland and Island Populations of Mediterranean Blue Tits
Authors: Charmantier Anne , Blondel Jacques
Published: December 2004

Extra‐pair copulation (EPC) is a widespread behaviour amongst birds, yet the rate of occurrence of extra‐pair offspring is highly variable both within and across species. Two populations of Mediterranean blue tits, Parus caeruleus, one on the mainland and the other on the island of Corsica, are characterized by high levels of extra‐pair paternity (EPP), with 14 and 25% of extra‐pair offspring (in 46 and 68% of the nests), respectively. The rate of EPP is significantly higher in the island population. Such high rates on Corsica contradict the predictions of higher mate fidelity and lower levels of EPP on islands. Despite expressing several traits that characterize an insular syndrome, blue tits of Corsica do not exhibit lower genetic variation which could be associated with low levels of EPP on islands. Furthermore, our results do not support any of the hypotheses that have been proposed so far to explain variation in EPP rates at the local level. We tentatively suggest that proximate Mediterranean constraints, especially consistent food shortage, prompt females to seek better breeding opportunities through a two‐step process including high rates of EPC and divorce.
Vocal Coordination of Group Movement by Green Woodhoopoes (Phoeniculus purpureus)
Authors: Radford A. N.
Published: December 2004

Communication signals are used by many species to maintain group cohesion when moving over larger areas. Groups of green woodhoopoes (Phoeniculus purpureus) generally move around their territory as a close‐knit unit. Dominant individuals were more likely than subordinates to initiate movement to a new foraging site, but there was no intersexual difference. Dominants were also more likely than subordinates to be followed immediately. Vocalizations were shown to play an important role in mobilization: in the thick forests inhabited by woodhoopoes, visual cues to coordinate movement are likely to be less successful. When responding to the rallying call of a neighboring group, dominants and subordinates were equally likely to lead, as were males and females. As other group members followed immediately on most of these occasions, vocalizations were less important in this context than when moving to a new foraging site.
Succession in a stream invertebrate community: A transition in species dominance through colonization
Authors: Miyake Yo , Hiura Tsutomu , Kuhara Naotoshi , Nakano Shigeru
Published: December 2004

A field experiment was conducted using ceramic plates as experimental substrates to describe the colonizing pattern of a stream invertebrate community after disturbance, and to ascertain the importance of colonizing ability for succession in a Japanese stream. We employed the simultaneous removal design in which plates were periodically set in place (1, 2, 4, 8, 16 and 32 days before sampling) and all plates were sampled on the last day of the experiment, to diminish the influence of seasonal change in stream invertebrates. Total abundance and taxon richness reached a plateau after 4–16 days of colonization. In contrast, the relative abundance of six common taxa and community structure changed throughout the 32 days of colonization. Differences in the colonizing ability of the stream invertebrates were evident. Taxa with high mobility, such as the mayflies Baetis thermicus, Paraleptophlebia japonica, Cinygmula sp. and Drunella sachalinensis, colonized faster than those with low mobility (e.g. the caddisfly species Brachycentrus americanus and the chironomid midge Diamesinae spp.). The abundance of the most common taxon, Baetis, decreased at late stages of colonization, possibly because of low periphyton biomass. Consequently, we concluded that a difference in colonization ability among taxa is an important factor causing succession in stream invertebrate communities in local habitats.
Influence of micro‐landforms on forest structure, tree death and recruitment in a Japanese temperate mixed forest
Authors: Nagamatsu Dai , Hirabuki Yoshihiko , Mochida Yukira
Published: December 2004

The micro‐landform unit system offers an effective way of analyzing vegetation–geomorphology relationships at a 10‐m scale in areas such as the hilly regions of Japan. We analyzed relationships between micro‐landforms and tree population parameters over a 9‐year interval to elucidate the influence of geomorphic processes on vegetation dynamics. A 2.16‐ha permanent plot was established in a temperate mixed forest. Each 5 m × 5 m quadrat within this plot was classified according to six types of micro‐landform units: (i) crest slope (CS); (ii) upper sideslope (US); (iii) head hollow (HH); (iv) lower sideslope (LS); (v) foot slope (FS); and (vi) river bed (RB). All living trees larger than 10 cm in diameter at breast height (d.b.h.) were identified, mapped and marked in 1989 and resurveyed in 1998. Almost all of the 23 common tree species persisted in their own core habitats (i.e. the micro‐landforms) between the two surveys. The species distribution in both surveys showed that the six micro‐landforms could be combined into two larger groups: upper and lower hillslope areas. The upper hillslope area had higher tree densities and larger basal areas than the lower hillslope area. It is possible that these differences result from the longer lifespans of trees on the upper hillslope area rather than from differences in mortality and recruitment rates. In addition, the different ways in which trees die in the different micro‐landform units may affect the regeneration process in hilly regions through different gap formation. The effects of different geomorphic processes are reflected in the lifespans of the trees and may result in different forest structure and dynamics among micro‐landform units.
Systemic NKT cell deficiency in NOD mice is not detected in peripheral blood: implications for human studies
Authors: Berzins Stuart P , Kyparissoudis Kon , Pellicci Daniel G , Hammond Kristen J , Sidobre Stephane , Baxter Alan , Smyth Mark J , Kronenberg Mitchell , Godfrey Dale I
Published: December 2004

In the diabetes‐prone NOD mouse, there is a proven association between a systemic deficiency of NKT cells and the onset of type 1 diabetes. Numerous reports of similar defects within the NKT cell compartment of human type 1 diabetes patients suggested NKT cell levels might be a valuable predictor of susceptibility and could provide a target for therapeutic intervention. Two recent studies, however, found no association between type 1 diabetes and blood NKT cell levels in humans and consequently rejected a link between the onset of diabetes and NKT cell deficiency. This cast considerable doubts on the potential for NKT cell‐based clinical applications and challenged the validity of the NOD mouse as a model of human type 1 diabetes. We now report that NKT cell levels in blood are a poor representation of those in other organs. Strikingly, systemic NKT cell deficiencies were identified in NOD mice with normal, or even raised, blood levels. This re‐establishes the correlation between NKT cell deficiency and type 1 diabetes and raises important questions regarding the assaying of NKT cell levels in humans.
Hepatitis C virus and lichen planus
Authors: NAGAO YUMIKO , SATA MICHIO
Published: December 2004

Hepatitis C virus (HCV) is an important factor in the development of chronic liver disease and hepatocellular carcinoma. In recent years it has become known that HCV induces various extrahepatic manifestations including mixed cryoglobulinemia, membranoproliferative glomerulonephritis, Sjögren's syndrome, autoimmune thyroiditis, malignant lymphoma, porphyria cutanea tarda and lichen planus. Although the mechanisms of extrahepatic manifestations remain unclear, it is known that interferon (IFN) therapy and coadministration of IFN with ribavirin are effective in promoting the disappearance or alleviation of such extrahepatic lesions, which have tended to be overlooked. The present review focuses on lichen planus, one of the major extrahepatic manifestations.

© 2004 Blackwell Publishing Asia Pty Ltd
Cannabis and driving: A new perspective
Authors: O'Kane Carl J , Tutt Douglas C , Bauer Lyndon A
Published: December 2004

Cannabis and driving is an emerging injury‐prevention concern. The incidence of driving while affected by cannabis is rising in parallel with increased cannabis use in the community. Younger drivers are at particular risk. Improvements in research methodology, technology and laboratory testing methods have occurred in the last 10 years. These cast doubt on earlier results and conclusions. Studies now show that cannabis has a significant impairing effect on driving when used alone and that this effect is exaggerated when combined with alcohol. Of particular concern is the presence of cannabis as the sole psychoactive drug in an increasing number of road fatalities and the lack of any structural response to this problem. A review of testing methods, laboratory and real driving studies, and recent epidemiological studies is presented. Suggestions for methods of further data collection and future public policy are made.
Enhancing cognitive performance with repetitive transcranial magnetic stimulation at human individual alpha frequency
Authors: Klimesch Wolfgang , Sauseng Paul , Gerloff Christian
Published: December 2004

We applied rapid‐rate repetitive transcranial magnetic stimulation (rTMS) at individual alpha frequency (IAF) to improve cognitive performance by influencing the dynamics of alpha desynchronization. Previous research indicates that a large upper alpha power in a reference interval preceding a task is related to both large suppression of upper alpha power during the task and good performance. Here, we tested the hypothesis that rTMS at individual upper alpha frequency (IAF + 1 Hz) can enhance alpha power in the reference interval, and can thus improve task performance. Repetitive TMS was delivered to the mesial frontal (Fz) and right parietal (P6) cortex, and as sham condition with 90°‐tilted coil (P6 position). The behavioural effect was assessed in a mental rotation task. Further control conditions were rTMS at a lower IAF (IAF − 3 Hz) and at 20 Hz. The results indicate that rTMS at IAF + 1 Hz can enhance task performance and, concomitantly, the extent of task‐related alpha desynchronization. This provides further evidence for the functional relevance of oscillatory neuronal activity in the alpha band for the implementation of cognitive performance.
Rhinal–hippocampal theta coherence during declarative memory formation: interaction with gamma synchronization?
Authors: Fell Juergen , Klaver Peter , Elfadil Hakim , Schaller Carlo , Elger Christian E. , Fernández Guillén
Published: December 2004

The hippocampus and the rhinal cortex, two substructures of the medial temporal lobe, together play a crucial role in human declarative memory formation. To investigate in detail the mechanism connecting these two structures transiently during memory formation we recorded depth EEG in epilepsy patients from within the hippocampus and the rhinal cortex. During this recording, patients performed a single‐trial word list‐learning paradigm with a free recall memory test following a distraction task. Rhinal–hippocampal EEG coherence and spectral power at both locations in the time interval up to 2 s after onset of word presentation were analysed in the frequency range 1–19 Hz. Successful as opposed to unsuccessful memory formation was associated with a general rhinal–hippocampal coherence enhancement, but without alterations in spectral power. Coherence increases in the theta range were correlated with the previously reported memory‐related changes in rhinal–hippocampal gamma phase synchronization. This correlation may suggest an interaction of the two mechanisms during declarative memory formation. While theta coherence might be associated with slowly modulated coupling related to an encoding state, rhinal–hippocampal gamma synchronization may be more closely related to actual memory processes by enabling fast coupling and decoupling of the two structures.
Working memory controls involuntary attention switching: evidence from an auditory distraction paradigm
Authors: Berti Stefan , Schröger Erich
Published: December 2004

One function of working memory is to protect current mental processes against interference. In contrast, to be able to react flexibly on unpredictable environmental changes working memory should not totally be encapsulated from processing task unrelated information; that is, it should remain distractible. By manipulating the task load of the primary task in an auditory distraction paradigm we investigated how these opposing functions are coordinated by working memory. The behavioural results show that distraction effects were still present but reduced markedly with higher task demands. This suggests that working memory exerts some control over involuntary attention. In addition, event‐related brain potentials related to the different processing stages reveal that the preattentive change detection system underlying distraction was not modulated by task demand whereas distraction per se was. The present data suggest that working memory is able to coordinate the maintenance of distractibility and the focus on the task at hand.
The expression of genes encoding visual components is regulated by a circadian clock, light environment and age in the honeybee (Apis mellifera)
Authors: Sasagawa Hiromi , Narita Ryo , Kitagawa Yasuo , Kadowaki Tatsuhiko
Published: December 2004

The honeybee, Apis mellifera, has been used as a model to study the development of the visual system and adult bee behaviour. However, the regulation of the levels of visual component genes has never been addressed in this organism. We isolated honeybee cDNAs encoding green‐sensitive opsin and visual arrestin and then measured their mRNA levels in honeybee workers. Both mRNAs fluctuate on a daily cycle that depends on a pacemaker that functions separately from the pacemaker which controls rhythmic locomotor activity. The cycling‐patterns of opsin and arrestin mRNAs are different from each other and are modified by light. Furthermore, light exposure can increase the absolute levels of both mRNAs and the arrestin mRNA level is also dependent on age. Consistent with these results, both mRNA levels are higher in foragers than in in‐hive bees under natural conditions. This study thus shows that the expression of genes encoding visual components is regulated by multiple factors and is adjusted to the honeybees' need for vision during the day, and throughout their lives. Comparison of data obtained with honeybees and other organisms indicates that there is a link between the regulation of phototransduction components and vision‐related animal behaviour.
The essential role of Broca's area in imitation
Authors: Heiser Marc , Iacoboni Marco , Maeda Fumiko , Marcus Jake , Mazziotta John C.
Published: December 2004

The posterior sector of Broca's area (Brodmann area 44), a brain region critical for language, may have evolved from neurons active during observation and execution of manual movements. Imaging studies showing increased Broca's activity during execution, imagination, imitation and observation of hand movements support this hypothesis. Increased Broca's activity in motor task, however, may simply be due to inner speech. To test whether Broca's area is essential to imitation, we used repetitive transcranial magnetic stimulation (rTMS), which is known to transiently disrupt functions in stimulated areas. Subjects imitated finger key presses (imitation) or executed finger key presses in response to spatial cues (control task). While performing the tasks, subjects received rTMS over the left and right pars opercularis of the inferior frontal gyrus (where Brodmann area 44 is probabilistically located) and over the occipital cortex. There was significant impairment in imitation, but not in the control task, during rTMS over left and right pars opercularis compared to rTMS over the occipital cortex. This suggests that Broca's area is a premotor region essential to finger movement imitation.
Auditory sensory memory disorder in dyslexic adults as indexed by the mismatch negativity
Authors: Kujala T. , Belitz S. , Tervaniemi M. , Näätänen R.
Published: December 2004

Deficient temporal discrimination and vulnerability to masking effects caused by rapidly succeeding or simultaneous sounds might be one factor underlying the phonological difficulties in dyslexia. We evaluated cortical auditory discrimination in dyslexia by recording the mismatch negativity (MMN) for a simple pitch change, for an order reversal of tone pairs, and for tone‐pair order reversals, with a third tone either preceding or following the tone pairs. It was found that when an additional tone followed the pairs the MMN amplitude was attenuated, suggesting elevated backward‐masking effects in the auditory cortex of dyslexic individuals. In addition, the MMN elicited by pitch change was diminished over the left hemisphere of the dyslexic individuals suggesting left hemisphere auditory dysfunction. These results suggest impaired cortical discrimination of sounds and lowered tolerance for the masking effects of rapidly following sounds in dyslexia.
The ERK/MAP kinase pathway couples light to immediate‐early gene expression in the suprachiasmatic nucleus
Authors: Dziema Heather , Oatis Ben , Butcher Greg Q. , Yates Robert , Hoyt Kari R. , Obrietan Karl
Published: December 2004

Signalling via the p42/44 mitogen‐activated protein kinase (MAPK) pathway has been identified as an intermediate event coupling light to entrainment of the mammalian circadian clock located in the suprachiasmatic nucleus (SCN). Given this observation, it was of interest to determine where within the entrainment process the MAPK pathway was functioning. In this study, we examined the role of the MAPK pathway as a regulator of light‐induced gene expression in the SCN. Towards this end, we characterized the effect pharmacological disruption of the MAPK cascade has on the expression of the immediate‐early genes c‐Fos, JunB and EGR‐1. We report that uncoupling light from MAPK pathway activation attenuated the expression of all three gene products. In the absence of photic stimulation, inhibition of the MAPK pathway did not alter basal gene product expression levels. Light‐induced activation of cAMP response element (CRE)‐dependent transcription, as assessed using a CRE‐LacZ transgenic mouse strain, was also disrupted by blocking MAPK pathway activation. These results reveal that the MAPK cascade functions as one of the first transduction steps leading from light to rapid transcriptional activation, an essential event in the entrainment process. MAPK pathway‐dependent gene expression in the SCN may result, in part, from stimulation of CRE‐dependent transcription.
A damage to locus coeruleus neurons converts sporadic seizures into self‐sustaining limbic status epilepticus
Authors: Giorgi Filippo S. , Ferrucci Michela , Lazzeri Gloria , Pizzanelli Chiara , Lenzi Paola , AlessandrÏ Maria G. , Murri Luigi , Fornai Francesco
Published: December 2004

Various studies demonstrated that the neurotransmitter norepinephrine (NE) plays a relevant role in modulating seizures; in particular, a powerful effect consists in delaying the kindling of limbic areas such as the amygdala and hippocampus. Given the rich NE innervation of limbic regions, we selected a sensitive trigger area, the anterior piriform cortex, to test whether previous loss of noradrenergic terminals modifies sporadic seizures in rats. The damage to locus coeruleus terminals was produced by using the selective neurotoxin N‐(‐2‐chloroethyl)‐N‐ethyl‐2‐bromobenzylamine (DSP‐4, 60 mg/kg i.p.). In intact rats, bicuculline (a GABA‐A antagonist, 118 pmol) microinfused into this area produced sporadic seizures, while in rats previously injected with DSP‐4, bicuculline determined long‐lasting self‐sustaining status epilepticus. In intact rats, sporadic seizures were accompanied by a marked increase in norepinephrine release in the contralateral piriform cortex, while in locus coeruleus‐lesioned rats this phenomenon was attenuated. While bicuculline‐induced sporadic seizures were prevented by the focal infusion of amino‐7‐phosphonoheptanoic acid (AP‐7, a selective NMDA antagonist), or 1,2,3,4‐tetrahydro‐6‐nitro‐2,3‐dioxo‐benzo[f]quinoxaline‐7‐sulphonamide (NBQX, a selective non‐NMDA antagonist), status epilepticus obtained in norepinephrine‐lesioned rats was insensitive to AP‐7 but was still inhibited by NBQX. By using fluorescent staining for damaged (Fluoro‐Jade B) and intact (DAPI) neurons, as well as cresyl violet, we found that rats undergoing status epilepticus developed neuronal loss in various limbic regions. This study demonstrates a powerful effect of noradrenergic terminals in regulating the onset of limbic status epilepticus and its sensitivity to specific glutamate antagonists.
Production and perception of grip force without proprioception: is there a sense of effort in deafferented subjects?
Authors: Lafargue Gilles , Paillard Jacques , Lamarre Yves , Sirigu Angela
Published: December 2004

We assessed the ability of healthy subjects (n = 7) and a patient deprived of proprioception (GL) to produce and assess different levels of isometric forces. They first produced a target force with one hand (the reference control hand) and then, after a delay of 3 s, they attempted to match it with the other hand (the experimental matching hand). Despite abnormal variations in motor outputs, we found that GL could, as could the control subjects, maintain a constant relationship between the force exerted by the control hand and the force exerted by the experimental hand. As GL was deprived of proprioceptive cues, these results suggest that she indirectly perceived muscular force through central effort. Interestingly, when carrying out the task the patient reported neither feelings of fatigue nor awareness of how hard she tried to perform the matches. Hence, under certain circumstances (such as in our motor task), it seems possible to assess and scale muscular force on the basis of endogenous signals only. However, internally generated signals related to the size of the motor command may need to interact with afferent input to gain full access to consciousness.
Anandamide regulates neuropeptide release from capsaicin‐sensitive primary sensory neurons by activating both the cannabinoid 1 receptor and the vanilloid receptor 1 in vitro
Authors: Ahluwalia Jatinder , Urban Laszlo , Bevan Stuart , Nagy Istvan
Published: December 2004

The effect of anandamide, which activates both the cannabinoid 1 (CB1) receptor and the vanilloid receptor 1 (VR1), was studied on calcitonin gene‐related peptide (CGRP) release from cultured primary sensory neurons, the majority of which coexpress the CB1 receptor and VR1. Concentrations of anandamide < 1 µm produced a small but significant CB1 receptor‐mediated inhibition of basal CGRP release while higher concentrations induced VR1‐mediated CGRP release. The excitatory effect of anandamide was potentiated by the CB1 receptor antagonist SR141716A. In the presence of SR141716A at concentrations < 100 nm, anandamide was equipotent with capsaicin in stimulating CGRP release. However, at higher concentrations anandamide produced more CGRP release than equimolar concentrations of capsaicin. Three and ten nanomolar anandamide inhibited the capsaicin‐evoked CGRP release. In the presence of SR141716A, treatments which activated protein kinase A, protein kinase C and phospholipase C significantly potentiated the anandamide‐evoked CGRP release at all anandamide concentrations. Although this potentiation was reduced when the CB1 receptor antagonist was omitted from the buffer, the CGRP release evoked by 300 nm and 1 µm anandamide was still significantly larger than that seen with nonpotentiated cells. These data indicate that anandamide may regulate CGRP release from capsaicin‐sensitive primary sensory neurons in vivo, and that the net effect of anandamide on transmitter release from capsaicin‐sensitive primary sensory neurons depends on the concentration of anandamide and the state of the CB1 receptor and VR1. These findings also suggest that anandamide could be one of the molecules responsible for the development of inflammatory heat hyperalgesia.
Bursts of high‐frequency stimulation trigger rapid delivery of pre‐existing α‐CaMKII mRNA to synapses: a mechanism in dendritic protein synthesis during long‐term potentiation in adult awake rats
Authors: Håvik Bjarte , Røkke Håvard , Bårdsen Kjetil , Davanger Svend , Bramham Clive R.
Published: December 2004

Messenger ribonucleic acid encoding the alpha‐subunit of calcium/calmodulin‐dependent protein kinase II (camkII) is abundantly and constitutively expressed in dendrites of pyramidal and granule cell neurons of the adult hippocampus. Recent evidence suggests that camkII messenger ribonucleic acid is stored in a translationally dormant state within ribonucleic acid storage granules. Delivery of camkII messenger ribonucleic acid from sites of storage to sites of translation may therefore be a key step in activity‐driven dendritic protein synthesis and synaptic plasticity. Here we explored possible camkII trafficking in the context of long‐term potentiation in the dentate gyrus of awake, adult rats. Long‐term potentiation was induced by patterned high‐frequency stimulation, synaptodendrosomes containing pinched‐off dendritic spines were obtained from microdissected dentate gyrus, and messenger ribonucleic acid levels were determined by real‐time polymerase chain reaction. High‐frequency stimulation triggered a rapid 2.5‐fold increase in camkII messenger ribonucleic acid levels in the synaptodendrosome fraction. This increase occurred in the absence of camkII upregulation in the homogenate fraction, indicating trafficking of pre‐existing messenger ribonucleic acid to synaptodendrosomes. The elevation in camkII messenger ribonucleic acid was paralleled by an increase in protein expression specific to the synaptodendrosome fraction, and followed by depletion of camkII message. Activity‐dependent regulation of camkII messenger ribonucleic acid and protein did not require N‐methyl‐d‐aspartate receptor activation. In contrast, N‐methyl‐d‐aspartate receptor activation was required for induction of the immediate early genes zif268 and activity‐regulated cytoskeleton‐associated protein in dentate gyrus homogenates. The results support a model in which locally stored camkII messenger ribonucleic acid is rapidly transported to dendritic spines and translated during long‐term potentiation in behaving rats.
Suppressed proliferation and apoptotic changes in the rat dentate gyrus after acute and chronic stress are reversible
Authors: Heine Vivi M. , Maslam Suharti , Zareno Jessica , Joëls Marian , Lucassen Paul J.
Published: December 2004

Acute stress suppresses new cell birth in the hippocampus in several species. Relatively little is known, however, on how chronic stress affects the turnover, i.e. proliferation and apoptosis, of the rat dentate gyrus (DG) cells, and whether the stress effects are lasting. We investigated how 3 weeks of chronic unpredictable stress would influence the structural dynamic plasticity of the rat DG, and studied newborn cell proliferation, survival, apoptosis, volume and cell number in 10‐week‐old animals. To study lasting effects, another group of animals was allowed to recover for 3 weeks. Based on two independent parameters, bromodeoxyuridine (BrdU) and Ki‐67 immunocytochemistry, our results show that both chronic and acute stress decrease new cell proliferation rate. The reduced proliferation after acute stress normalized within 24 h. Interestingly, chronically stressed animals showed recovery after 3 weeks, albeit with still fewer proliferating cells than controls. Apoptosis, by contrast, increased after acute but decreased after chronic stress. These results demonstrate that, although chronic stress suppresses proliferation and apoptosis, 3 weeks of recovery again normalized most of these alterations. This may have important implications for our understanding of the reversibility of stress‐related hippocampal volume changes, such as occur, for example, in depression.
Synthesis, localization and externalization of galectin‐1 in mature dorsal root ganglion neurons and Schwann cells
Authors: Sango Kazunori , Tokashiki Akiko , Ajiki Kyoko , Horie Masao , Kawano Hitoshi , Watabe Kazuhiko , Horie Hidenori , Kadoya Toshihiko
Published: December 2004

We recently confirmed that oxidized galectin‐1 is a novel factor enhancing axonal growth in peripheral nerves after axotomy, but the process of extracellular release and oxidization of endogenous galectin‐1 in the injured nervous tissue remains unknown. In the present study, we examined the distribution of galectin‐1 in adult rat dorsal root ganglia (DRG) in vivo and in vitro. By RT‐PCR analysis and in situ hybridization histochemistry, galectin‐1 mRNA was detected in both DRG neurons and non‐neuronal cells. Immunohistochemical analyses revealed that galectin‐1 was distributed diffusely throughout the cytoplasm in smaller diameter neurons and Schwann cells in DRG sections. In contrast, the immunoreactivity for galectin‐1 was detected in almost all DRG neurons from an early stage in culture (3 h after seeding) and was restricted to the surface and/or extracellular region of neurons and Schwann cells at later stages in culture. In a manner similar to the primary cultured cells, we also observed the surface and extracellular expression of this molecule in immortalized adult mouse Schwann cells (IMS32). Western blot analysis has revealed that both reduced and oxidized forms of galectin‐1 were detected in culture media of DRG neurons and IMS32. These findings suggest that galectin‐1 is externalized from DRG neurons and Schwann cells upon axonal injury. Some of the molecules in the extracellular milieu may be converted to the oxidized form, which lacks lectin activity but could act on neural tissue as a cytokine.
Indirect facilitation of an anuran invasion by non‐native fishes
Authors: Adams Michael J. , Pearl Christopher A. , Bruce Bury R.
Published: December 2004

Positive interactions among non‐native species could greatly exacerbate the problem of invasions, but are poorly studied and our knowledge of their occurrence is mostly limited to plant‐pollinator and dispersal interactions. We found that invasion of bullfrogs is facilitated by the presence of co‐evolved non‐native fish, which increase tadpole survival by reducing predatory macroinvertebrate densities. Native dragonfly nymphs in Oregon, USA caused zero survival of bullfrog tadpoles in a replicated field experiment unless a non‐native sunfish was present to reduce dragonfly density. This pattern was also evident in pond surveys where the best predictors of bullfrog abundance were the presence of non‐native fish and bathymetry. This is the first experimental evidence of facilitation between two non‐native vertebrates and supports the invasional meltdown hypothesis. Such positive interactions among non‐native species have the potential to disrupt ecosystems by amplifying invasions, and our study shows they can occur via indirect mechanisms.
Good housekeeping: why do shelter‐dwelling caterpillars fling their frass?
Authors: Weiss Martha R.
Published: December 2004

Although both feeding and elimination of waste are imperatives for all animals, ecologists and evolutionary biologists have devoted considerable attention to foraging, while largely ignoring defecation. Many organisms, however, exhibit defecation behaviours that appear to have been shaped by natural selection in a range of ecological contexts. Accumulation of waste may pose particular challenges for animals that exhibit high site fidelity or live within enclosed spaces. In a taxonomically widespread but largely unexamined behaviour, many caterpillars that construct and inhabit leaf shelters ballistically eject their individual faecal pellets (frass) great distances at great speeds. Here, I show that elimination of chemical cues for natural enemies is likely to have been a driving force behind the evolution of frass ejection behaviour in skipper caterpillars; hygiene and crowding are less important in this system.
The influence of size‐dependent life‐history traits on the structure and dynamics of populations and communities
Authors: De Roos André M. , Persson Lennart , McCauley Edward
Published: December 2004

Individual organisms often show pronounced changes in body size throughout life with concomitant changes in ecological performance. We synthesize recent insight into the relationship between size dependence in individual life history and population dynamics. Most studies have focused on size‐dependent life‐history traits and population size‐structure in the highest trophic level, which generally leads to population cycles with a period equal to the juvenile delay. These cycles are driven by differences in competitiveness of differently sized individuals. In multi‐trophic systems, size dependence in life‐history traits at lower trophic levels may have consequences for both the dynamics and structure of communities, as size‐selective predation may lead to the occurrence of emergent Allee effects and the stabilization of predator–prey cycles. These consequences are linked to that individual development is density dependent. We conjecture that especially this population feedback on individual development may lead to new theoretical insight compared to theory based on unstructured or age‐dependent models. Density‐dependent individual development may also cause individuals to realize radically different life histories, dependent on the state and dynamics of the population during their life and may therefore have consequences for individual behaviour or the evolution of life‐history traits as well.
Overyielding among plant functional groups in a long‐term experiment
Authors: Hooper David U. , Dukes Jeffrey S.
Published: December 2004

A recent debate among ecologists has focused on mechanisms by which species diversity might affect net primary productivity. Communities with more species could use a greater variety of resource capture characteristics, leading to greater use of limiting resources (complementarity) and therefore greater productivity (overyielding). Recent experiments, however, have shown a variety of relationships between diversity and productivity. In an experiment on serpentine grassland communities spanning 8 years, we found that overyielding increased several years after plot establishment. Overyielding varied greatly depending on the functional characteristics of the species involved and the biotic and abiotic environment (particularly water availability). While functional differences among species led to strong complementarity and facilitation, these effects were not sufficient to cause significant transgressive overyielding or consistent increases in productivity with increased plant diversity. These results suggest that greater absolute production with greater diversity may be restricted to particular species combinations or environmental conditions.
Growth autocorrelation and animal size variation
Authors: Fujiwara Masami , Kendall Bruce E. , Nisbet Roger M.
Published: December 2004

It has long been recognized that variability in animal size is affected by how individual growth rate is autocorrelated in time. Earlier studies have attributed the mechanism generating the autocorrelation primarily to size‐dependent growth rate and autocorrelation in resource abundance. All of these studies have shown that positive autocorrelation in individual growth rate always translates into increased variability in size. We show that energy reserves in individuals induce growth autocorrelation by acting like a low pass filter between the resource and the internal energy that is available for metabolism, growth and reproduction. However, the reserve also reduces the variance in growth rate. Consequently, reserve‐induced growth autocorrelation has relatively little effect on size variability in the population, contradicting existing ideas about the relationship between the growth autocorrelation and size variability.
Plastic phenotypic resistance to predation by Bdellovibrio and like organisms in bacterial prey
Authors: Shemesh Yair , Jurkevitch Edouard
Published: December 2004

Predation at the lowest trophic level, i.e. between bacteria, is poorly understood, hindering efforts to assess its impact on the structure of bacterial communities. The interaction of Bdellovibrio and Bacteriovorax (Bdellovibrio and like organisms, BLOs), a group of obligate, ubiquitous predatory bacteria, with their Gram‐negative bacterial prey results in the multiplication of the predator and in the lysis, but not in the eradication, of the prey. We show that the residual, surviving populations of prey cells exposed to predation stress differ from the populations before exposure, as they exhibit increased resistance to predation. This resistance was demonstrated in a number of Gram‐negative prey. Moreover, predation resistance is not specific for the BLO strain experienced by the prey. The phenomenon does not stem from a mutation but is a plastic response associated with a phenotypic change, and it disappears upon removal of the predator. As resistance to predation is not total, this mechanism can ensure survival of both predator and prey.
Comparative analysis of a genome fragment of an uncultivated mesopelagic crenarchaeote reveals multiple horizontal gene transfers
Authors: López‐García Purificación , Brochier Céline , Moreira David , Rodríguez‐Valera Francisco
Published: December 2004

Marine planktonic crenarchaeota have escaped all cultivation attempts to date, all crenarchaeota growing in pure culture so far being hyperthermophiles. Here, we present a comparative genomic analysis of a 16S‐ plus 23S‐rDNA‐containing fragment of a crenarchaeote retrieved from an environmental genomic library constructed from picoplankton collected at 500 m depth in the Antarctic Polar Front. The clone DeepAnt‐EC39 contained an insert of 33.3 kbp, which was completely sequenced. DeepAnt‐EC39 appears to represent a lineage specific to deep‐sea waters but widespread geographically, as revealed by the analysis of the 16S‐23S‐rDNA intergenic spacer region. A comparison with previously sequenced marine crenarchaeotal genomic clones also containing an rrn operon (74A4, 4B7 and Cenarchaeum symbiosum strains A and B) revealed a highly variable structure involving gene rearrangements and insertions/deletions. The surroundings of the rrn operon and the contiguous glutamate‐1‐semialdehyde aminotransferase gene appear hot spots for recombination. Phylogenetic analyses of all individual predicted proteins revealed the existence of several likely cases of horizontal gene transfer both, between the two archaeal kingdoms and between the two prokaryotic domains. The most frequent horizontal transfers appear to involve genes from mesophilic methanogenic euryarchaeota related to Methanosarcinales. We hypothesise that the acquisition of genes from mesophilic bacteria and euryarchaeota has played a major role in the adaptation of Group I crenarchaeota to life at lower temperatures.
Enhanced sensitivity of DNA‐ and rRNA‐based stable isotope probing by fractionation and quantitative analysis of isopycnic centrifugation gradients
Authors: Lueders Tillmann , Manefield Mike , Friedrich Michael W.
Published: December 2004

Stable isotope probing (SIP) of nucleic acids allows the detection and identification of active members of natural microbial populations that are involved in the assimilation of an isotopically labelled compound into nucleic acids. SIP is based on the separation of isotopically labelled DNA or rRNA by isopycnic density gradient centrifugation. We have developed a highly sensitive protocol for the detection of ‘light’ and ‘heavy’ nucleic acids in fractions of centrifugation gradients. It involves the fluorometric quantification of total DNA or rRNA, and the quantification of either 16S rRNA genes or 16S rRNA in gradient fractions by real‐time PCR with domain‐specific primers. Using this approach, we found that fully13C‐labelled DNA or rRNA ofMethylobacterium extorquenswas quantitatively resolved from unlabelled DNA or rRNA ofMethanosarcina barkeriby cesium chloride or cesium trifluoroacetate density gradient centrifugation respectively. However, a constant low background of unspecific nucleic acids was detected in all DNA or rRNA gradient fractions, which is important for the interpretation of environmental SIP results. Consequently, quantitative analysis of gradient fractions provides a higher precision and finer resolution for retrieval of isotopically enriched nucleic acids than possible using ethidium bromide or gradient fractionation combined with fingerprinting analyses. This is a prerequisite for the fine‐scale tracing of microbial populations metabolizing13C‐labelled compounds in natural ecosystems.