bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sub‐optimal morning temperature induces photoinhibition in dense outdoor cultures of the alga Monodus subterraneus (Eustigmatophyta)
Authors: Vonshak A. , Torzillo G. , Masojidek J. , Boussiba S. 
Published: March 2003

AbstractDiel changes in photosynthetic oxygen evolution and several photochemical parameters measured by chlorophyll fluorescence quenching and induction were measured in outdoor dense cultures of the alga Monodus subterraneus (Eustigmatophyta). Cultures were maintained under two temperature regimes. In one, a rise in temperature was initiated in the morning by the increase in solar radiation up to the optimal temperature of 28 °C; in the other, a heating device was used to increase the rate of warming up in early morning.Although the two cultures were maintained at the same temperature and light intensity for most of the day, cultures exposed for only a short time to suboptimal morning temperature showed a larger decrease in almost all the photosynthetic parameters. By comparing the diel changes in maximal photochemistry efficiency of photosystem II, the electron transport rate and the photochemical and non‐photochemical chlorophyll fluorescence quenching of the cultures, we concluded that even a relatively short exposure to suboptimal morning temperatures induced photoinhibitory damage. The higher photochemical activity of the heated culture was also reflected in a significant increase in productivity, which was 60% higher in the morning heated cultures than in the non‐heated cultures.
An experimental test of the link between foraging, habitat selection and thermoregulation in black rat snakes Elaphe obsoleta obsoleta
Authors: Blouin‐Demers Gabriel , Weatherhead Patrick J. 
Published: March 2003

Summary

Most physiological processes are temperature‐dependent. Thus, for ectotherms, behavioural control of body temperatures directly affects their physiology. Ectotherms thermoregulate by adjusting habitat use and therefore thermoregulation is probably the single most important proximate factor influencing habitat use of terrestrial reptiles, at least in temperate climates.
Snakes have been shown to raise their body temperature following feeding in a laboratory thermal gradient, presumably to enhance digestion. This experiment was exported to the field to explore the link between feeding, habitat selection and thermoregulation in free‐ranging snakes.
Experimental feeding was conducted in the laboratory and in the field on black rat snakes (Elaphe obsoleta obsoleta) that had temperature‐sensitive radio‐transmitters surgically implanted.
Snakes had higher mean body temperatures following feeding than prior to feeding in a laboratory thermal gradient.
Some, but not all evidence, indicated that black rat snakes increased their mean body temperature following feeding in the field. Indices of thermoregulation indicated that the snakes thermoregulated more carefully and more effectively after they had eaten.
Forest edges provided the best opportunities for thermoregulation in the study area. Black rat snakes were less likely to move following feeding when fed in edges than when fed in the forest and were more likely to be found in edges following feeding, whether they had been fed in the forest or in an edge.
Results of this study and one previous study suggest that thermoregulatory behaviour of snakes following feeding in the laboratory is a reliable predictor of their behaviour in the field. A review of 13 studies of the thermoregulatory behaviour of snakes following feeding in the laboratory revealed that not all species behave similarly. However, the quality and number of studies currently available is not adequate for testing hypotheses about which species should change thermoregulatory behaviour in response to eating and which should not.
A long‐term study of reproductive performance in tree swallows: the influence of age and senescence on output
Authors: Robertson Raleigh J. , Rendell Wallace B. 
Published: March 2003

SummaryWe describe age‐related reproductive performance and recapture rates of tree swallows (Tachycineta bicolorVieillot) based on a 25‐year study of a nestbox population in south‐eastern Ontario, Canada (1975–99).Performance improved from first‐time breeders to intermediate‐aged birds. Nest initiation advanced, and clutch size increased in both sexes. In females the number of hatchlings and fledglings increased, and the proportion of nests failing completely declined. Performance declined in females after ‘middle‐age’, in the number of young fledged, and the proportion of young fledged relative to initial clutch and brood size. Also, the proportion of nests that failed completely increased in the oldest birds. Males showed similar patterns.An index of performance incorporating clutch size, hatching and fledging efficiency, and two measures of total nest failure increased to, then declined after, 4 years of age in females and 3 years in males. The relationship between this index and age was best predicted by quadratic regression.We found no support for three of four hypotheses to explain improvement in performance with age. Recapture rates declined after age 4Y in males, but remained unchanged in females until age 7Y +, while output decreased in both sexes (Residual Reproductive Value). Birds breeding repeatedly did not perform better during their first attempt compared to birds that bred only once (Selection). Birds with varied breeding experience did not differ in their performance within age‐groups (Breeding Experience). We did find support for the Breeding Age hypothesis; in females with no breeding experience, there was a successive advance in laying and increase in clutch size from 2 to 4 years of age.Improved performance may be due to skills acquired with age, such as those devoted to feeding and balancing energy demands, which are necessary to prepare and maintain individual condition prior to, and during, breeding. Senescence in performance after ‘middle‐age’ may result from accumulated costs of previous breeding effort which have been identified in this species based on research elsewhere.
Benefits of early arrival at breeding grounds vary between males
Authors: Forstmeier Wolfgang 
Published: March 2003

Summary It is often assumed that, in migratory birds, males of highest phenotypic quality are the first to arrive at breeding grounds, as only males in good body condition can afford the costs of early arrival. Here it is argued that variation in how much an individual can gain from being early may sometimes override these patterns of condition dependence. Benefits from early arrival will depend on how good the chances of an individual are of successfully occupying and defending a high‐quality territory. Other studies have shown that these chances depend on male resource‐holding power (RHP) and on value asymmetries (VA), as resulting from prior ownership. Patterns of spring arrival were studied in a polygynous population of the dusky warblerPhylloscopus fuscatusBlyth, a species with high breeding‐site tenacity. During the period of postnuptial moult, just before departure to winter quarters, about half of the males preoccupied and vigorously defended high‐quality territories. Apparently these males enhanced their success in competition over these territories in the following breeding season by taking advantage of having prior ownership. Males with good chances of obtaining a high‐quality territory (i.e. males that had occupied such territories before) were the first to arrive in spring, suggesting that high motivation drives early arrival. In contrast, there was no indication for male quality or body condition to affect arrival patterns. Interestingly, males of small body size, possibly reflecting low RHP, invested more in gaining prior ownership than did large males. The present study suggests that, in some species, individual variation in benefits rather than in costs resulting from early arrival determine which males are the first to arrive.
Effect of jasmonate‐induced plant responses on the natural enemies of herbivores
Authors: Thaler Jennifer S. 
Published: March 2003

Summary

Plant traits can act as defences against herbivores both by reducing herbivore performance directly and by increasing the effectiveness of the natural enemies of herbivores. Natural enemy performance and rate of parasitism can be affected by plant traits and/or changes in herbivore quality.
Jasmonic acid is responsible for the induction of many changes in plant resistance that occur following herbivore attack. This study examines the effects of jasmonate‐induced defences on the abundance and performance of natural enemies, as well as the interaction between induced plant responses and parasitism in their ability to kill herbivores.
In a tomato field containing plants induced with jasmonic acid and control plants, the abundance of natural enemies was counted using several census techniques. Induced resistance affected the abundance of natural enemies of herbivores differently. One predator of aphids, syrphid flies, was negatively affected by the decrease in herbivore abundance on induced plants. One parasitoid of caterpillars, Hyposoter exiguae Viereck, was not affected by induced resistance in this study although it was positively affected in a previous study. Two other natural enemies, a parasitoid of aphids and ladybeetle predators, were not affected by induced resistance.
Induced resistance and parasitism both reduced the survivorship of herbivores. In a 2 × 2 factorial design with induced resistance crossed by parasitism, the interaction between the effects of induced resistance and parasitism on herbivore survival was tested. Two trials of this experiment were conducted; one where induced resistance affected both herbivore quantity and quality and one where induced resistance only affected herbivore quality (herbivore density was equalized).
Parasitoids were more effective at killing herbivores feeding on control plants than herbivores on induced plants. This difference was due to a difference in herbivore quality, not herbivore quantity. Herbivores feeding on induced plants have lower mass than herbivores on control plants and this appears to be a major factor reducing the performance of developing parasitic wasps.
Thus, jasmonate‐induced responses influence natural enemies species in differing ways, sometimes reducing the density of herbivores and sometimes reducing the quality of herbivores for natural enemies.
Dispersal potential and early growth in 14 tropical mangroves: do early life history traits correlate with patterns of adult distribution?
Authors: Clarke Peter J. , Kerrigan Raelee A. , Westphal Christine J. 
Published: March 2003

Summary

We characterized the dispersal potential and early growth traits of 14 tropical mangrove species in experiments where diaspores were immersed in various solutions of seawater and subsequently stranded onto surfaces with the same salinity.
Viviparous and non‐viviparous species had similar buoyancy, seed weight and rates of root and shoot initiation, as well as early growth and salinity tolerance. This trait convergence may be related to selection against small, dormant diaspores in the unstable regeneration niche.
Differences in dispersal potential and early growth of 12 species were compared with known patterns of distribution (across the shore, along estuaries, regional occurrence and continental range size) to test if tidal sorting of diaspores could account for adult spatial patterns.
Diaspore buoyancy, orientation, lateral root initiation, shoot initiation and early shoot extension differed among species but none correlated with adult zonation across the shore or along estuaries. However, some back‐shore species had diaspores that were buoyant and were slow to initiate lateral roots and shoots. Patterns of early growth were partially related to the distribution along estuaries but salinity responses contributed to this zonation in only three species.
Regional distributions were unrelated to dispersal potential. However, the tendency of infrequent species to show slow growth in full seawater may account for the under‐saturation of species in estuaries with appropriate habitats. The range size of the tropical mangroves appears unrelated to their dispersal potential and early growth traits.
Early life history traits of 12 mangroves showed poor correlation with patterns of adult distribution across all spatial scales. Traits related to establishment were, however, stronger predictors of distribution than those associated with dispersal.
Leaf dynamics and maintenance of tree crowns in a Malaysian rain forest stand
Authors: Osada Noriyuki , Takeda Hiroshi , Furukawa Akio , Awang Muhamad 
Published: March 2003

Summary Leaf demography was examined for trees of various heights over a 3.7‐year period in a Malaysian rain forest. We compared demography between upper and lower parts of the crown and its relation to height. The results were analysed at the stand level by pooling several trees of various shade‐tolerant species, as well as three species for which multiple individuals were sampled. Photon flux density was generally higher in the upper than in the lower crowns. Leaf production rate and leaf loss rate were faster, and number of leaf cohorts and median leaf life span were therefore lower, in the upper crowns of most trees. Faster rates of leaf loss and shorter life spans were associated with increasing height, although leaf production rate was unaffected. Leaf life span and specific leaf area were plastic traits which decreased with height within several shade‐tolerant tree species, indicating functional convergence. Vertical distribution of leaf biomass was almost even in the stand. Because leaf life span was shorter in the upper canopy, these leaves contributed most to litter production. The vertical structure of the forest stand was therefore maintained through dynamic processes in trees of various heights over short time‐scales.
Degradation of mangrove tissues and implications for peat formation in Belizean island forests
Authors: Middleton B. A. , McKee K. L. 
Published: March 2003

Summary Macrofaunal leaf consumption and degradation of leaves, woody twigs and roots were studied in mangrove island forests on a Belizean island. Factors influencing accumulation of organic matter deposited both above and below ground in this oligotrophic, autochothonous system were assessed. Leaf degradation rates ofRhizophora mangle(red mangrove),Avicennia germinans(black mangrove) andLaguncularia racemosa(white mangrove) measured in mesh bags, were much faster in the lower than the upper intertidal zone. Mass loss was most rapid inA. germinansbut zonal effects were much larger than species differences. Exposure to invertebrates such as crabs and amphipods tripled overall rates of leaf litter breakdown. In the lower intertidal, crabs completely consumed some unbagged leaves within 23 days. Crabs also had an effect on some upper intertidal sites, where degradation of leaves placed in artificial burrows was 2.4 times faster than when placed on the soil surface. In contrast to leaves (27 ± 5% remaining after 230 days), roots and woody twigs were highly refractory (40 ± 2% and 51 ± 6% remaining after 584 and 540 days, respectively). Root degradation did not vary by soil depth, zone or species. Twigs ofR. mangleandA. germinansdegraded faster on the ground than in the canopy, whereas those ofL. racemosawere highly resistant to decay regardless of position. Peat formation at Twin Cays has occurred primarily through deposition and slow turnover of mangrove roots, rather than above‐ground tissues that are either less abundant (woody twigs) or more readily removed (leaves).
Parasitic fungus mediates change in nitrogen‐exposed boreal forest vegetation
Authors: Strengbom Joachim , Nordin Annika , Näsholm Torgny , Ericson Lars 
Published: March 2003

Summary

Experimental additions of N to an old‐growth boreal forest resulted in elevated levels of free amino acids in leaves of the dominant dwarf‐shrub Vaccinium myrtillus and increased attack from a parasitic fungus, Valdensia heterodoxa.
Glutamine additions to the leaf surface of V. myrtillus increased disease incidence by an average of almost three times compared to controls and suggested a causal connection between amino acid availability and fungal infection.
Increased abundance of the grass Deschampsia flexuosa followed N addition but infection by the parasitic fungus, which causes premature leaf loss of its primary host V. myrtillus, explained four times as much of the variation in grass abundance as N did.
Nitrogen deposition can have marked effects on vegetation by affecting the interaction between dominant hosts and their natural enemies. A shift in abundance of dominating species occurred within 3 years of treatment, with nitrogen loads similar to those deposited over large areas in Europe and North America, suggesting that such effects may by important for the vegetation of large areas subjected to low levels of nitrogen input.
Elevated atmospheric CO2affects structure of a model regenerating longleaf pine community
Authors: Davis Micheal A. , Pritchard Seth G. , Mitchell Robert J. , Prior Stephen A. , Rogers Hugo H. , Runion G. Brett 
Published: March 2003

AbstractDifferences in plant morphology, physiology, life form, and symbiotic relationships can generate differences in species responses to CO2‐enrichment, which can alter competitive interactions, thus affecting community structure and function. Here, we present data from a two‐year study, examining the species and community responses to elevated [CO2] of a model regenerating longleaf pine community. The model community was constructed from an assemblage of early successional forest species representing major functional guilds within a typical longleaf pine–wiregrass community: (1) a C3evergreen conifer (Pinus palustris); (2) a C4bunch grass (Aristida stricta); (3) a C3broadleaf tree (Quercus margaretta); (4) a C3perennial herbaceous legume (Crotalaria rotundifolia); and (5) a C3herbaceous perennial (Asclepias tuberosa). After 2 years, CO2‐enriched plots had 109% greater above‐ground biomass than ambient plots, mainly due to a 117% increase in pine biomass. Community structure was altered by CO2enrichment;CrotalariaandAsclepiashad higher mortality and less biomass in high‐CO2plots, suggesting that not all species will perform well as global [CO2] rises. Our data suggest that longleaf pine communities as a whole will perform well in a future higher CO2world, but some species may fall prey to altered competitive interactions for light and soil moisture.
Molecular determinants for the action of general anesthetics  at recombinant α2β3γ2γ‐aminobutyric acidA receptors
Authors: Siegwart Roberta , Jurd Rachel , Rudolph Uwe 
Published: March 2003

AbstractGeneral anesthetics modulate the activity of ligand‐gated ion channels including the GABAA receptor. Mutational studies mainly on the benzodiazepine‐insensitive α2β1(M286W) and α6β3(N289M)γ2 GABAA receptors revealed that a serine in transmembrane domain 2 and a methionine in transmembrane domain 3 are essential for the action of most general anesthetics. We investigated whether these residues would similarly be relevant for their action at the benzodiazepine‐sensitive GABA receptor subtype, α2β3γ2. We found that not only the N265M but also the M286W mutation nearly abolished the modulatory effect of etomidate. However, the anti‐convulsant loreclezole, a structural homologue of etomidate, was inactive on the N265M mutant, but displayed normal modulatory activity on the M286W mutant. Both mutations did not affect the modulatory action of the neurosteroid alphaxalone. The direct action of alphaxalone, however, was dramatically increased in the M286W mutant to about twice the maximal GABA current but not significantly affected in the N265M mutant. These data demonstrate that the structural requirements for modulatory and direct actions of various general anesthetics are distinct. The molecular switches induced by these mutations can be exploited to identify the molecular determinants for the action of general anesthetics.
Role of Ca2+ and calmodulin‐dependent enzymes in the regulation of glycine transport in Müller glia
Authors: Gadea Ana , López Edith , Hernández‐Cruz Arturo , López‐Colomé Ana María 
Published: March 2003

AbstractGlycine (Gly) is considered an obligatory co‐agonist at NMDA receptors. Müller glia from the retina harbor functional NMDA receptors, as well as low and high affinity Gly transporters, the later identified as GLYT1. We here studied the regulation of Gly transport in primary cultures of Müller glia, as this process could contribute to the modulation of NMDA receptor activity at glutamatergic synapses in the retina. We demonstrate that neither glutamate stimulation nor the activation or inhibition of protein kinases A or C modify transport. In order to assess a function for Ca2+ and calmodulin (CaM)‐dependent processes in the regulation of Gly transport, we explored the participation of Ca2+ concentration, CaM and Ca2+/CaM‐dependent enzymes on Gly transporter activity. ATP and carbachol, known to induce Ca2+ waves in Müller cells, as well as caffeine‐induced Ca2+ release from intracellular stores stimulated transport, whereas Ca2+ chelation by BAPTA‐AM markedly reduced transport. CaM inhibitors W‐7, ophiobolin A, R‐24571 and trifluoperazine, induced a specific dose‐dependent inhibition of transport. The inhibition of CaMKII by the autocamtide‐2‐related inhibitory peptide or by KN62 caused a decrease in transport which, in the case of KN62, was due to the abolition of the high affinity component, ascribed to GLYT1. Our results further suggest that Gly transport is under cytoskeletal control, as activation of calpain by major increases in [Ca2+]i induced by ionophores, as well as actin destabilization clearly inhibit uptake. We here demonstrate for the first time the participation of CaM, CaMKII and the actin cytoskeleton in the regulation of Gly transport in glia. Ca2+ waves are induced in Müller cells by distinct neuroactive compounds released by neurons and glia, hence the regulation of [Gly] by this system may be of physiological relevance in the control of retinal excitability.
Interleukin‐1β‐induced substance P release from rat cultured primary afferent neurons driven by two phospholipase A2 enzymes: secretory type IIA and cytosolic type IV
Authors: Morioka Norimitsu , Takeda Kazumi , Kumagai Kei , Hanada Tomohiko , Ikoma Kozo , Hide Izumi , Inoue Atsuko , Nakata Yoshihiro 
Published: March 2003

AbstractWe previously described that recombinant interleukin‐1β (IL‐1β) induced the significant release of substance P (SP) via a cyclooxygenase (COX) pathway in primary cultured rat dorsal root ganglion (DRG) cells. In the present study, we examined the involvement of two types of phospholipase A2 (PLA2) enzymes, which lie upstream of COX in the prostanoid‐generating pathway, in the IL‐1β‐induced release of SP from DRG cells. The expression of type ΙΙΑ secretory PLA2 (sPLA2‐IIA) mRNA was undetectable by ribonuclease protection assay in non‐treated DRG cells, while in DRG cells incubated with 1 ng/mL of IL‐1β, the expression was induced in a time‐dependent manner. On the other hand, type IV cytosolic PLA2(cPLA2) mRNA was constitutively expressed in the non‐treated DRG cells, and treatment with 1 ng/mL of IL‐1β for 3 h significantly increased the levels of cPLA2mRNA. The IL‐1β‐induced SP release was significantly inhibited by the sPLA2inhibitor, thioetheramide phosphorylcholine (TEA‐PC), and the cPLA2inhibitor, arachidonyl trifluoromethyl ketone (AACOCF3). Furthermore AACOCF3suppressed the induction of sPLA2‐IIA mRNA expression induced by IL‐1β. These observations suggested that two types of PLA2, sPLA2‐IIA and cPLA2, were involved in the IL‐1β‐induced release of SP from DRG cells, and that the functional cross‐talk between the two enzymes might help to control their activity in the prostanoid‐generating system in DRG cells. These events might be key steps in the inflammation‐induced hyperactivity in primary afferent neurons of spinal cord.