bluuebunny/crossref_metadata_2025 huggingface dataset:
What determines the foraging distribution of raptors on heather moorland?
Authors: Thirgood Simon J. , Redpath Stephen M. , Graham Isla M.
Published: December 2004

Foraging theory predicts that mobile predators such as raptors should hunt more frequently in habitat patches yielding the greatest energy gains. Raptor foraging distributions may, however, be constrained by nest location and by competition between different raptor species. We tested these hypotheses in a moorland raptor assemblage including two vole specialists and three generalist predators. We studied spatial and temporal variation in the foraging distributions of these raptors during breeding and non‐breeding seasons on an area of moorland managed for red grouse in Scotland. We compared raptor foraging distributions to indices of prey abundance and availability, the habitat characteristics of foraging sites, and for some species, the distance from nest sites. We also assessed whether the foraging distributions of the smaller raptors were influenced by the larger raptors. Short‐eared owlsAsio flammeus, kestrelsFalco tinnunculusand common buzzardsButeo buteoshowed pronounced temporal variation in foraging in either breeding or non‐breeding seasons in response to fluctuations in the abundance of small mammals. Having removed year effects, however, spatial variation in foraging by these species within and outside the breeding season was not explained by small mammal abundance or availability. In contrast, the foraging distributions of hen harriersCircus cyaenusand peregrinesFalco peregrinusshowed no significant temporal variation. During the breeding season, male and female harriers foraged on areas near harrier nests. Outside the breeding season, female harriers foraged in areas with more grouse and small mammals. Peregrines showed no foraging response to prey during the breeding season but during the non‐breeding season they hunted in areas with more grouse. There was little evidence that the foraging distributions of smaller raptors were influenced by larger raptors; however, golden eaglesAquila chrysaetoswere rarely seen at our study site. These results suggest the simple dichotomy between specialist and generalist predators that masks a more complex response to prey abundance.
Modelling the role of social behavior in the persistence of the alpine marmotMarmota marmota
Authors: Grimm Volker , Dorndorf Norbert , Frey‐Roos Fredy , Wissel Christian , Wyszomirski Tomasz , Arnold Walter
Published: December 2004

A general rule of thumb for biological conservation obtained from simple models of hypothetical species is that for populations with strong environmental noise moderate increases in habitat size or quality do not substantially reduce extinction risk. However, whether this rule also holds for real species with complex behavior, such as social species with breeding units and reproductive suppression, is uncertain. Here we present a population viability analysis of the alpine marmotMarmota marmota, which displays marked social behavior, i.e. it lives in social groups of up to twenty individuals. Our analysis is based on a long‐term field study carried out in the Bavarian Alps since 1982. During the first fifteen years of this study, 687 marmots were individually marked and the movements and fate of 98 dispersing marmots were recorded with radio‐telemetry. Thus, in contrast to most other viability analyses of spatially structured populations, good data about dispersal exist. A model was constructed which is individual‐based, spatially explicit at the scale of clusters of neighbouring territories, and spatially implicit at larger scales. The decisive aspect of marmot life history, winter mortality, is described by logistic regression where mortality is increased by age and the severity of winter, and decreased by the number of subdominant individuals present in a group. Model predictions of group size distribution are in good agreement with the results of the field study. The model shows that the effect of sociality on winter mortality is very effective in buffering environmental harshness and fluctuations. This underpins theoretical results stating that the appropriate measure of the strength of environmental noise is the ratio between the variance of population growth rate and the intrinsic rate of increase. The lessons from our study for biological conservation are that simple, unstructured models may not be sufficient to assess the viability of species with complex behavioral traits, and that even moderate increases in habitat capacity may substantially reduce extinction risk even if environmental fluctuations seem high.
The architecture of shrubs after defoliation and the subsequent feeding behavior of browsers
Authors: Cooper S. M. , Owens M. K. , Spalinger D. E. , Ginnett T. F.
Published: December 2004

We examined regrowth architecture of 4 species of savanna shrubs following 4 levels of defoliation. Defoliation had little effect on the regrowth architecture of honey mesquite (Prosopis glandulosa), which is rarely browsed by mammalian herbivores. The 3 acacia species (Acacia berlandieri, A. greggii, A. schaffneri) responded to defoliation by increasing leaf and spine density on the regrowth branches, but spine length and branching architecture remained unchanged. Only A. greggii, which is a preferred food plant of many browsers, exhibited an increase in the number and length of current annual growth branches in response to defoliation. The changes in plant architecture due to defoliation had little effect on the subsequent feeding behavior of captive white‐tailed deer (Odocoileus virginianus). Food intake rate of the deer was most strongly related to internode distance, a parameter not significantly altered by defoliation. This suggests that the architectural responses of these shrubs to defoliation may not provide increased defense against browsing by co‐evolved mammals.
Extrinsic and intrinsic factors determine the eruptive dynamics of Brandt's voles Microtus brandti in Inner Mongolia, China
Authors: Zhang Zhibin , Pech Roger , Davis Stephen , Shi Dazhao , Wan Xinrong , Zhong Wenqin
Published: December 2004

Brandt's voles (Microtus brandti) are small native mammals that inhabit the grasslands of Inner Mongolia, China. The species is considered a pest, particularly during population outbreaks, which have increased in frequency since 1970 from 1 every 7 years to 1 every 3 to 5 years. Using historical records taken between 1948 and 1998, we found that there was significant correlation between years for which the monthly averages of the Southern Oscillation Index (SOI) were consistently high, and years in which outbreaks occurred. Also there was a tendency for outbreaks not to occur in years with precipitation above or below average. For some years at some sites, annual or biannual estimates are available for the density of Brandt's vole populations. We found that the seasonal rate of increase over the non‐breeding season from autumn to spring was negatively correlated with the density in autumn. The rate of increase over the breeding season from spring to autumn was independent of the density in spring but instead, reflects the species' preference for habitat with short, sparse grass; populations do not persist in highly degraded grasslands or in tall, dense grassland. The link between outbreaks and climatic indices, and the numerical response of Brandt's voles to particular habitat characteristics, suggest that current grazing intensity tends to maintain grass at low height in years with average precipitation. The substantial increase in livestock numbers over the last 50 years appears to have increased the number of years when the balance of grazing and plant growth favours high rates of increase in Brandt's vole populations, and hence, there has been an increase in the frequency of outbreaks.
Relatedness and competitive asymmetry – the growth and development of common frog tadpoles
Authors: Pakkasmaa Susanna , Aikio Sami
Published: December 2004

Individuals can compete either through direct interference or uptake of limiting resources. If competing individuals are able to recognize their relatives, relatedness of competitors may evoke kin selection, which favours relatively even resource share among relatives. Resource competition is often size‐symmetric, i.e. proportional to an individual's biomass, while interference competition is asymmetric giving large individuals a disproportionate advantage over small individuals. Kin‐selection is predicted to reduce the intensity of direct interference and competitive asymmetry, leading to increased mean and decreased variation in individual size. We tested these predictions by investigating the effects of relatedness on age and size at metamorphosis in the common frogRana temporariatadpoles in a laboratory experiment. We reared related (full‐ and half‐sibs) and unrelated tadpoles of different sizes (small, large, small and large together) at two densities until metamorphosis. Relatedness had little effect on mean growth, but it reduced size variation, as measured with coefficient of variation. Furthermore, there was a significant interaction between relatedness and density in size at metamorphosis, so that relatives always grew better in lower density, but growth was less affected by density among unrelated individuals. This indicates that the effects of relatedness on tadpole performance may be context dependent. Initial size differences in the mixed size treatment evened out during the course of the experiment, and initially small tadpoles were able to compensate the early growth losses, although it took longer for them to reach metamorphosis. We conclude that although relatedness may have rather small effects on the growth and development ofR. temporariatadpoles, it increases the symmetry of resource share decreasing between‐individual variation in size at metamorphosis.
Significance of butterfly eyespots as an anti‐predator device in ground‐based and aerial attacks
Authors: Lyytinen Anne , Brakefield Paul M. , Mappes Johanna
Published: December 2004

Many butterfly genera are characterised by the presence of marginal eyespots on their wings. One hypothesis to account for an occurrence of eyespots is that these wing pattern elements are partly the outcome of visual selection by predators. Bicyclus anynana (Satyrinae) has underside spotting on its wings but there is also a seasonal form in which the eyespots are reduced in size or totally absent. This natural variation gives us a useful tool to test the hypothesis that marginal eyespot patterns can decoy the attacking predator by, at least sometimes, diverting attack from vital body parts to the edges of the wings. We used lizards, Anolis carolinensis, and pied flycatchers, Ficedula hypoleuca, as predators for living spotted and spotless B. anynana. The presence of eyespots did not increase the escape probability of resting butterflies once captured (even a form with enlarged eyespots did not add to effective deflection of attacks). There was also no evidence that eyespots influenced the location of strikes by the predators. This study thus provides no support that marginal eyespot patterns can act as an effective deflection mechanism to avoid lizard or avian predation.
Experimental determination of predation intensity in an intertidal predator guild: dominant versus subordinate prey
Authors: Navarrete Sergio A. , Castilla Juan C.
Published: December 2004

Theoretical and empirical ecologists have long acknowledged that information about the intensity or strength of the interaction between species is crucial for an understanding of community dynamics. In communities in which predation is an important structuring process, and some predator species are commercially exploited, quantitative estimates of predation by different predator species within a guild are necessary to make even the simplest recommendations about conservation and resource management. Here, we evaluated per capita and population level components of predation intensity of three intertidal predators that feed on monospecific stands of barnacles and mussels at wave exposed sites in the rocky intertidal zone of central Chile. These prey species represent the two most distinctive stages of the mid‐intertidal seascape, with mussels being competitively dominant. Our results showed that the commercially exploited gastropod Concholepasconcholepas and the sea star Heliasterhelianthus have similarly large per capita and population effects on the competitively dominant mussel Perumytiluspurpuratus. Their per capita (by average size individual) and population effects on mussels were more than two orders of magnitude larger than those of Acanthocyclusgayi crabs and likely even larger than the effect of other predator species in this system (other crabs, whelks, birds, fish). The overall pattern of predation on barnacles was similar to that on mussels, but some differences occurred in the way different components of predation intensity were distributed across predator species. Despite the roughly similar pattern of population predation intensity between prey species, the expected consequences for the prey population, and hence the rest of the community, were acutely different for mussels and barnacles.
Phenotypic modifications to conspecific density arising from predation risk assessment
Authors: Peacor S.D.
Published: December 2004

Organisms often perceive predation risk through visual, auditory, or chemical cues that accompany or persist after an attack on other prey individuals. In this paper an argument is developed that suggests that it is adaptive for species that use such indirect cues to include conspecific density in the assessment of predation risk, and to respond to conspecific density by modifying phenotype (e.g. behavior, morphology of life history). A model based on this argument predicts that at equivalent (including negligible) indirect cue levels an organism should adopt less vulnerable phenotypes at lower conspecific density. Further, the phenotypic modifications to differences in conspecific density are predicted to be on the same order of magnitude as phenotypic responses to differences in predator density, to be more pronounced at higher indirect cue levels, and can be extended to responses to differences in the density of heterospecific species that share predators. This “risk assessment” mechanism is qualitatively different from other mechanisms, such as the dilution and “many eyes” effects that predict behavioral responses to conspecific density. If species use conspecific or heterospecific density to assess predation risk as predicted, there may be implications for the role and evolution of traits used to perceive conspecific and heterospecific densities, species aggregation, and population dynamics, and should be considered in the design of experiments of nonlethal effects of predators.
Adjacency arrangement effects on plant diversity and composition in woodland patches
Authors: Hersperger Anna M. , Forman Richard T. T.
Published: December 2004

To understand “adjacency arrangement” (configuration of a patch and its adjoining elements) as a basic unit of landscape pattern, we studied 30 woodland patches (Populus tremuloides)in Alberta, Canada, with adjacent vegetation varying from 0% shrubland (100% grassland) to 100% shrubland (0% grassland). We evaluated (1) how important adjacency effects are relative to resource availability and disturbance in affecting plant species richness and composition in the woodland understory, and (2) which species and species groups change in abundance and presence with increasing percent shrubland in the adjacency arrangement. We found that, in addition to topography and previous grazing, adjacency arrangement is a major significant variable affecting the vegetation composition of woodland patches. Along a gradient from 0% to 100% adjacent shrubland, the species composition in woodland patches changed from an abundance of weedy and introduced plants to an abundance of moist‐environment plants, the proportion of native species and perennials increased linearly, the number of “shrubland species” increased linearly, “grassland species” decreased linearly, and total species richness remained constant. Woodland vegetation did not differ significantly where adjacent shrubland was to the east or to the west of the wooded patch, nor between patches which did or did not experience a change in the adjacent shrubland in the recent past. We conclude that adjacency arrangement is an easily measured, highly promising concept for ecological understanding, as well as for land planning, design, conservation and management.
Herbivore damage to sagebrush induces resistance in wild tobacco: evidence for eavesdropping between plants
Authors: Karban Richard , Maron John , Felton Gary W. , Ervin Gary , Eichenseer Herbert
Published: December 2004

Whether plants respond to cues produced by neighbors has been a topic of much debate. Recent evidence suggests that wild tobacco plants transplanted near experimentally clipped sagebrush neighbors suffer less leaf herbivory than tobacco controls with unclipped neighbors. Here we expand these results by showing evidence for induced resistance in naturally rooted tobacco when sagebrush neighbors are clipped either with scissors or damaged with actual herbivores. Tobacco plants with sagebrush neighbors clipped in both ways had enhanced activity levels of polyphenol oxidase (PPO), a chemical marker of induced resistance in many solanaceous plants. Eavesdropping was found for plants that were naturally rooted, although only when sagebrush and tobacco grew within 10 cm of each other. Although tobacco with clipped neighbors experienced reduced herbivory, tobacco that grew close to sagebrush had lower production of capsules than plants that grew far from sagebrush. When neighboring tobacco rather than sagebrush was clipped, neither levels of PPO nor levels of leaf damage to tobacco were affected. Eavesdropping on neighboring sagebrush, but not neighboring tobacco, may result from plants using a jasmonate signaling system. These results indicate that plants eavesdrop in nature and that this behavior can increase resistance to herbivory although it does not necessarily increase plant fitness.
Body size and the timing of egg production in parasitoid wasps
Authors: Ellers Jacintha , Jervis Mark
Published: December 2004

In insects several key fitness‐related variables are positively correlated with intraspecific variation in body size, but little is known about size‐related variation in the timing of egg production within species. Female insects are known to vary in the degree to which they concentrate egg production into the early part of life. This variation has been quantified as the ovigeny index, defined as the proportion of the maximum potential lifetime complement of eggs that is mature following emergence from the pupa. We tested the hypothesis that the timing of egg production depends both on body size and on host availability, by means of a dynamic programming model that predicted optimal resource allocation to reproduction and survival together with the resulting ovigeny index, in non‐feeding synovigenic parasitoids of different sizes. As body size increases, the proportionate increase in resource allocation to initial egg load is less than the proportionate increase in allocation to lifetime fecundity and potential life span, leading to a deferred investment in reproduction as shown by a decrease in ovigeny index. High habitat quality and high habitat stochasticity in reproductive opportunities have a significant effect on the optimal allocation of resources to reproduction and survival, and thus select for early reproduction, i.e. an increased ovigeny index. The ovigeny concept – ovigeny index together with its life‐history correlates – enables understanding of the general occurrence of size‐related deferment of reproductive investment in parasitoid wasps and also helps explain a significant part of the considerable life‐history variation found among such insects.
Life in the land of the midnight sun: are northern lizards adapted to longer days?
Authors: Uller Tobias , Olsson Mats
Published: December 2004

The relative importance of genetic and environmental factors for explaining differences in trait distributions between populations is one of the major issues in evolutionary biology. In ectotherms, temperature can have a major impact on morphology, physiology, and life history strategies, and has often been inferred to explain differences between populations. In species with active thermoregulation, however, the ambient temperature may not be as important as the opportunity for thermoregulation. We studied growth in juvenile common lizards (Lacerta vivipara) originating from two environments differing in such thermal opportunity (i.e. day length). The populations differed significantly in their norms of reaction, with lizards experiencing long days in the wild showing a steeper increase in growth rate with increasing thermal opportunity. The environment with longer days also has a lower mean temperature in the wild, and in accordance with evolutionary predictions, lizards from this population had higher endurance at low temperatures. Both populations showed genetic variation in degree of phenotypic plasticity in growth rate as evident from the extensive crossing in norms of reaction.
The anatomy of a range expansion: changes in cranial morphology and rates of energy extraction for North American red squirrels from different latitudes
Authors: Goheen Jacob R. , Swihart Robert K. , Robins James H.
Published: December 2004

Species with expanding ranges provide unique opportunities to examine environmentally induced adaptations in ecological traits and anatomical characteristics. Since the late 1800s, the North American red squirrel (Tamiasciurus hudsonicus) has expanded its range into the central hardwoods of the United States in conjunction with increasing agricultural fragmentation. We examined whether red squirrels from the central hardwoods (west‐central Indiana, USA) displayed differences in foraging behaviors and morphology relative to red squirrels from conifer‐dominated environments (upper peninsula of Michigan, USA), a biome in which red squirrels evolved. Specifically, we measured rates of energy extraction, variation in cranial morphology, and diet preference between red squirrels from both regions. In addition, we compared foraging behaviors of red squirrels from the central hardwoods to those of a competitor that coevolved with nut‐producing trees, the gray squirrel (Sciurus carolinensis). Red squirrels from Indiana and Michigan differed significantly in the efficiency with which they used food items, with individuals from each region extracting calories at a more rapid rate for items that were common in their region. The enhanced efficiency of southern red squirrels feeding on black walnuts (Juglans nigra) was correlated with geographic differences in cranial morphology; skulls of southern squirrels were larger, with longer jaws and higher metrics associated with greater mandibular force than northern squirrels. Contrary to our expectations, red squirrels from Indiana and Michigan did not differ qualitatively in preferences for food items, suggesting that diet choice may be governed by perishability of food items rather than by rates of energy extraction. Gray squirrels were more efficient than Indiana red squirrels in using all food items, and differed only slightly from red squirrels with regard to preference for food items. Measures of efficiency of resource use, after accounting for species‐specific metabolic requirements, suggest that red squirrels are unlikely to compensate ecologically for declining gray squirrel populations in fragmented portions of the central hardwoods, with potentially adverse effects for forest regeneration and succession. Our results demonstrate that invading species can display significant flexibility in adapting to new environments, but they may not be flexible enough to exploit resources in a manner comparable to native species.
Sentenced without trial: reviling and revamping the Resource Dispersion Hypothesis
Authors: Johnson Dominic D. P. , Macdonald David W.
Published: December 2004

The resource dispersion hypothesis (RDH) offers a predictive model for how, in heterogeneous environments, some animals may form groups even without any direct benefits from doing so. Revilla (2003) levels a number of criticisms at the RDH, all of which we feel can be easily clarified or resolved (we address them in the order they appear in his critique). We argue that the RDH, despite its long history and despite our own efforts, still lacks convincing evidence to reject it. On the contrary, we see it as having weathered its critics very well. While there is steadily accumulating evidence in support of the RDH, there are very few empirical tests that provide decent evidence against it.
Abnormal Vesicular Trafficking in Mouse Models of Hermansky–Pudlak Syndrome
Authors: SWANK RICHARD T. , NOVAK EDWARD K. , MCGARRY MICHAEL P. , ZHANG YUKE , LI WEI , ZHANG QING , FENG LIJUN
Published: December 2004

Hermansky–Pudlak Syndrome (HPS) is a group of related multigenic recessively inherited disorders which causes abnormalities in the biosynthesis and/or function of three related organelles; melanosomes, platelet‐dense granules and lysosomes. These lead, in turn, to hypopigmentation, prolonged bleeding and ceroid deposition. Positional cloning strategies have identified five mouse HPS genes. Two orthologous human diseases (HPS1 and HPS2) have likewise been identified. At least four of the five mouse genes encode proteins involved in the regulation of intracellular vesicle trafficking. The pearl (HPS2) and mocha genes encode the beta3A and delta subunits, respectively, of the AP‐3 adaptor complex, which captures organelle membrane proteins at the trans‐Golgi apparatus. The protein products of the pallid and gunmetal genes are also important components of the vesicular trafficking machinery. The former interacts with a t‐SNARE, syntaxin13, and the latter is the alpha subunit of Rab geranylgeranyltransferase, which renders Rab proteins sufficiently lipophilic to function at their target membranes. The pale ear (HPS1) gene encodes a ubiquitously expressed protein of unknown function. Recent physiological studies have shown that mouse HPS mutants, like their human HPS counterparts, have variably reduced lifespans and may have lung abnormalities.
Intracellular Vesicular Trafficking of Tyrosinase Gene Family Protein in Eu‐ and Pheomelanosome Biogenesis
Authors: JIMBOW KOWICHI , HUA CHEN , GOMEZ PAUL F. , HIROSAKI KUNINORI , SHINODA KYOKA , SALOPEK THOMAS G. , MATSUSAKA HIDENOBU , JIN HAI‐YING , YAMASHITA TOSHIHARU
Published: December 2004

The intracellular vesicular trafficking in the melanosome biogenesis (melanogenesis) is reviewed with the incorporation of our own experimental findings. The melanosome biogenesis involves four stages of melanosome maturation, which reflect the transport of structural and enzymatic proteins from Golgi (trans‐Golgi network: TGN) to the melanosomal compartment and their organization therein. The major melanosomal proteins include tyrosinase gene family protein (tyrosinase and tyrosinase‐related protein; TRP), lysosome‐associated membrane protein (Lamp) and gp100 (pmel 17). They are glycosylated in the endoplasmic reticulum, and transported by vesicles from the TGN to the melanosomal compartment. During the formation of transport vesicles, they assemble on the cytoplasmic face of the TGN to select cargo by interacting directly or indirectly with coat proteins. Tyrosinase and TRP‐1 possess the dileucine motifs at the cytoplasmic domain, to which adapter protein‐3 binds to transport them from the TGN to stage I melanosomes (related to late endosomes) and then to stage II melanosomes. A number of small guanosine triphosphate‐binding proteins, including rab 7, appear to be involved in this vesicular transport. Phosphatidyl inositol 3 kinase also regulates this membrane trafficking of melanosomal glycoprotein. Eumelanogenesis is controlled by melanocyte‐stimulating hormone, and all three tyrosinase gene family proteins are transported from the TGN to stage II melanosomes that are elliposoidal and contain the structural matrix of filaments/lamellae. In contrast, pheomelanogenesis is primarily regulated by agouti signal protein, and only tyrosinase is transported from stage I melanosomes to stage II melanosomes that are spherical and related to lysosomes. Because of the absence of TRP‐1 and TRP‐2 in pheomelanogenesis, it may be suggested that tyrosinase is involved in lysosomal degradation after forming dopaquinone, to which the cysteine present in the lysosomal granule binds to form cysteinyldopas that will then be auto‐oxidized to become pheomelanin.
The Melanosome: The Perfect Model for Cellular Responses to the Environment
Authors: HEARING VINCENT J.
Published: December 2004

Melanocytes play critical roles in mammals, including the regulation of constitutive pigmentation in the skin, hair, and eyes, in embryological development, and in photoprotection from ionizing radiation. The pigments themselves, possibly due to the inherent cytotoxic properties of their precursors, are synthesized and deposited within membrane‐bound organelles known as melanosomes. However, the structure of melanosomes, and thus their characteristic properties, varies widely, from relatively disorganized, poorly pigmented pheomelanosomes to highly structured, melanized eumelanosomes. Melanocytes respond to various physiological stimuli, such as melanocyte‐stimulating hormone (MSH), agouti signal protein (ASP), endothelins and/or ultraviolet light (UVL) by highly complex intracellular signaling mechanisms that can elicit dramatic changes in melanosome and melanocyte morphology. MSH and UVL stimulate transcription of melanogenic genes that elicit dramatic increases in the amount of eumelanins produced, whereas ASP serves as an antagonist of MSH and inhibits the transcription of those same genes. Recent studies have shown that melanocyte‐specific transcription factors, such as MITF, play important roles in these responses, but ubiquitous transcription factors, such as ITF2 and E2A, are also involved. Virtually all known intracellular signaling pathways affect one or more parameters of pigmentation, and it is clear that both melanocyte‐specific and basic housekeeping processes are affected by such modulation. The properties of melanins, including their photoprotective function, may be optimized by such stimulatory responses. Studies targeted at elucidating the regulatory mechanisms involved and the functional changes that result demonstrate that the melanosome is the perfect model to study such biological response mechanisms.
1‐Methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine Pretreatment Attenuates Methamphetamine‐Induced Dopamine Toxicity
Authors: Kita Taizo , Saraya Tutomu , Konishi Noboru , Matsunari Yasunori , Shimada Keiji , Nakamura Mitsutoshi , O'Hara Kiichi , Wagner George C. , Nakashima Toshikatsu
Published: December 2004

Abstract: The effects of pretreatment with MPTP (1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine) on the acute and long‐term effects of methamphetamine on striatal dopamine were evaluated in BALB/c mice. Four subcutaneous injections of a non‐toxic dose of MPTP (8 mg/kg, at 2 hr intervals) were followed three days later by a toxic regimen of methamphetamine (four injections of 4 mg/kg, at 2 hr intervals) and mice were sacrificed immediately or three days later. Control mice received saline in place of the MPTP or methamphetamine and mice were observed for acute changes in body temperature, self‐injurious behaviour, and striatal dopamine metabolites, or long‐term changes in striatal dopamine levels, tyrosine hydroxylase immunoreactivity and glial fibrillary acidic protein. It was observed that pretreatment with MPTP protected mice against the acute increase in body temperature caused by the methamphetamine but, at the same time, delayed the occurrence of self‐injurious behaviour following the repeated injections of methamphetamine. Likewise, pretreatment with MPTP attenuated the long‐term depletion of striatal dopamine induced by the methamphetamine as well as the large increase in glial fibrillary acidic protein and the reduction in tyrosine hydroxylase immunoreactivity. The MPTP‐treatment itself did not alter any of these neurotoxic markers. Finally, the acute decrease in 3,4‐dihydroxyphenyacetic acid levels and increased ratio of 3‐methoxytyramine/dopamine observed 60 min. after a single injection of methamphetamine (4 mg/kg) were also attenuated in MPTP‐treated mice. These results are discussed in the context of the hypothesis that the low‐dose treatment with MPTP may modify exchange diffusion across the striatal cell membrane thereby altering the acute and long‐lasting effects of methamphetamine.
Induction of Apoptosis by Tanshinone I via Cytochrome c Release in Activated Hepatic Stellate Cells
Authors: Kim Ji Young , Kim Kyoung Mi , Nan Ji‐Xing , Zhao Yu Zhe , Park Pil‐Hoon , Lee Sang Jun , Sohn Dong Hwan
Published: December 2004

Abstract: Hepatic stellate cells play central roles in hepatic fibrosis. The therapeutic goal in hepatic fibrosis is to halt or reverse fibrosis. Apoptosis is suggested to eliminate activated hepatic stellate cells in fibrosis. Salvia miltiorrhiza is a traditional medicine used to improve blood circulation and treat chronic hepatitis and hepatic fibrosis. We investigated the effect of tanshinone I, an ingredient of Salvia miltiorrhiza, on the apoptotic death of rat hepatic stellate cells transformed by simian virus 40 (T‐HSC/Cl‐6), which retains the features of activated stellate cells. Treatment of T‐HSC/Cl‐6 cells with tanshinone I resulted in the induction of typical DNA fragmentation and DNA ladder formation in a concentration‐ and time‐dependent manner. The induction of apoptosis was confirmed by flow cytometric analysis. Treatment of T‐HSC/Cl‐6 cells with tanshinone I caused activation of caspase‐3 and subsequent proteolytic cleavage of poly(ADP‐ribose) polymerase. Tanshinone I induced mitochondrial membrane dipolarization and the release of cytochrome c from mitochondria into the cytosol. In conclusion, our results demonstrate that tanshinone I induces apoptosis of T‐HSC/Cl‐6 cells and that tanshinone I‐induced apoptosis involves caspase activation through cytochrome c release and loss of mitochondrial membrane potential.
Calcium Channels Involved in Noradrenaline Release from Sympathetic Neurones in Rabbit Carotid Artery*
Authors: Uhrenholt Torben R. , Nedergaard Ove A.
Published: December 2004

Abstract: Transmitter release from nerve terminals is dependent on the entry of Ca2+ through neuronal voltage‐gated calcium channels. In sympathetic neurones both N‐ and L‐type calcium channels are present. Potassium channel blockade increases Ca2+ entry into sympathetic neurones. We examined the participation of N‐ and L‐type calcium channels in the stimulation‐evoked release of noradrenaline from vascular sympathetic neurones. Rings of rabbit carotid artery were preincubated with [3H]‐noradrenaline. Electrical field stimulation was used to evoke 3H overflow. The selective N‐type calcium channel blocking agent ω‐conotoxin GVIA (single concentrations: 3×10−10–10−8 M) caused a slowly developing reduction of the stimulation‐evoked 3H overflow. At 3×10−8 M, ω‐conotoxin GVIA caused an equilibrium block with a rapid (15 min.) onset. After 2 hr exposure to ω‐conotoxin the inhibition was steady (pIC50 (‐log M): 9.43; Emax: 91%). The selective L‐type calcium blocking agents nifedipine (10−7–10−5 M) and nimodipine (10−8–10−5 M) had no effect on the stimulation‐evoked 3H overflow. The calcium channel opener Bay K 8644 (10−6 M) likewise had no effect. The potassium channel blocking agent 4‐aminopyridine (10−5–10−3 M) enhanced the stimulation‐evoked 3H overflow up to 5 times. 4‐Aminopyridine (10−4 M) did not alter the inhibitory effect of ω‐conotoxin GVIA (3×10−8 M). In the presence of 4‐aminopyridine (10−4 M), nifedipine (10−5 M) and nimodipine (10−6 M) enhanced the 3H overflow. We conclude that the stimulation‐evoked release of noradrenaline from sympathetic neurones in rabbit carotid artery is mediated by N‐type calcium channels and that L‐type channels are not involved even when potassium channels are blocked by 4‐aminopyridine.
Pimozide Injections into the Nucleus accumbens Disrupt Maternal Behaviour in Lactating Rats
Authors: Silva Maria Rita P. , Bernardi Maria M. , Cruz‐Casallas Pablo E. , Felicio Luciano F.
Published: December 2004

Abstract: In rodents ongoing maternal behaviour requires activation of dopamine receptors. Therefore, it is possible that some motor components of maternal behaviour might be mediated by concurrent dopaminergic stimulation. It has been previously demonstrated that peripheral injections of some antipsychotic drugs such as pimozide have disruptive effects on maternal behaviour. The present experiments were designed to verify the effects of pharmacological blockade of limbic dopamine receptors on ongoing maternal behaviour in lactating rats. The hypothesis that central injections of the drug pimozide would have an effect on maternal behaviour was tested. We investigated the effects of central bilateral intra‐accumbens microinjections of the dopamine D2 receptor antagonist pimozide (1.5 and 3.0 μg) on maternal behaviour. Animals treated with 3.0 μg of pimozide showed significantly longer latencies for all parameters of maternal behaviour compared to controls. These results suggest that dopamine receptors in the nucleus accumbens play a role in ongoing maternal behaviour.
Photo(chemo) therapy for vitiligo
Authors: Roelandts Rik
Published: December 2004

Vitiligo has always been difficult to treat. Several modes of treatment are available, but the therapeutic effect varies greatly, and rarely does one achieve complete repigmentation. One of the most efficient treatment methods is photo(chemo) therapy. Already in ancient Egypt, vitiligo lesions were treated with extracts of the Ammi maius plant followed by exposure to the sun. This principle is at the basis of the photochemotherapy or PUVA therapy, whereby UVA irradiations are given 2 h after administration of 8‐methoxypsoralen, a photosensitizer. Another efficient treatment form is UVB phototherapy, particularly narrow‐band UVB. This not only gives good therapeutic results but also has the advantage of eliminating the need for a photosensitizer. All these treatments must be applied for many months to be efficient. They can also be combined with various surgical skin‐grafting techniques. A newer approach is targeted UVB phototherapy, whereby xenon‐chloride lasers or monochromatic excimer light is used.
The photopatch test procedure of the German, Austrian, and Swiss photopatch test group
Authors: Neumann N. J. , Lehmann P.
Published: December 2004

In 1984 the German, Austrian, and Swiss photopatch test group was established to investigate photoallergic reactions as well as the epidemiology of photoallergy in central Europe. Therefore, the photopatch test procedure was defined and photopatch test data of 3998 patients were evaluated after two test periods from 1984 to 1990 and from 1991 to 1997. In summary, non‐steroidal anti‐inflammatory drugs, disinfectants, phenothiazines as well as sunscreens were found to be relevant photoallergens in central Europe. Based on the study results and guided by contemporaneously published clinical findings, the German, Austrian, and Swiss photopatch test group released in the year 2000 an optimized photopatch test tray, including a block of 19 photosensitizers, ranging from some historical to newly reported photosensitizers. This standard set is complemented by an optional photopatch test set, indicated only in special cases.
Accuracy of annual erythema exposure estimation using different numbers of ambient exposure fractions in the human exposure model
Authors: Vishvakarman D. , Wong J. C. F.
Published: December 2004

Background: The aim was to determine the optimum number of ambient exposure fractions required in the human exposure model for accurate computation of annual erythema effective solar exposure.

Methods: Ambient exposure fractions were determined on a daily basis over a period of a year in the Rockhampton region using ambient exposure measurements and erythema effective solar exposure measurements at selected body sites of Australia post mail delivery personnel (APMDP). Several values of annual erythema effective exposure for the same body sites were computed using different combinations of ambient exposure fractions on a monthly, seasonally and half‐yearly basis in the human exposure model and compared with the measured values.

Results: This method enabled a check on the accuracy of annual erythema effective solar exposure estimation using the different combinations of ambient exposure fractions in the human exposure model. In the worst case there was approximately 35% difference between the measured value and the computed value.

Conclusion: The best accuracy was obtained with the use of ambient exposure fractions on a monthly basis where most of the estimated values for the different body sites were within 20% of the measured values.
Photoaging in Asians
Authors: Chung Jin Ho
Published: December 2004

The aging process of the skin can be divided into intrinsic and photoaging. Clinically, naturally aged skin is smooth, pale and finely wrinkled. In contrast, photoaged skin is coarsely wrinkled and associated with dyspigmentation and telangiectasia. Although the population of Asia is more than half the population of the Earth, no well‐designed study has been undertaken to investigate the characteristics of cutaneous photodamage in Asian skin. As Asian skin is more pigmented, the acute and chronic cutaneous responses to UV irradiation seen in brown skin differ from those in white skin. The clinical characteristics of photoaging in Asian skin, such as pigmentary changes and wrinkle patterns, differ from those of Caucasian skin. This review provides an outline of the characteristic features of photoaging on the brown skin of Asians.
UV exposure in cars
Authors: Moehrle Matthias , Soballa Martin , Korn Manfred
Published: December 2004

Background: There is increasing knowledge about the hazards of solar and ultraviolet (UV) radiation to humans. Although people spend a significant time in cars, data on UV exposure during traveling are lacking. The aim of this study was to obtain basic information on personal UV exposure in cars.

Methods: UV transmission of car glass samples, windscreen, side and back windows and sunroof, was determined. UV exposure of passengers was evaluated in seven German middle‐class cars, fitted with three different types of car windows. UV doses were measured with open or closed windows/sunroof of Mercedes‐Benz E 220 T, E 320, and S 500, and in an open convertible car (Mercedes‐Benz CLK). Bacillus subtilis spore film dosimeters (Viospor) were attached to the front, vertex, cheeks, upper arms, forearms and thighs of ‘adult’ and ‘child’ dummies.

Results: UV wavelengths longer than >335 nm were transmitted through car windows, and UV irradiation >380 nm was transmitted through compound glass windscreens. There was some variation in the spectral transmission of side windows according to the type of glass. On the arms, UV exposure was 3–4% of ambient radiation when the car windows were shut, and 25–31% of ambient radiation when the windows were open. In the open convertible car, the relative personal doses reached 62% of ambient radiation.

Conclusions: The car glass types examined offer substantial protection against short‐wave UV radiation. Professional drivers should keep car windows closed on sunny days to reduce occupational UV exposure. In individuals with polymorphic light eruption, produced by long‐wave UVA, additional protection by plastic films, clothes or sunscreens appears necessary.
Immediate effects of UV radiation on the skin: modification by an antioxidant complex containing carotenoids
Authors: Césarini J. P. , Michel L. , Maurette J. M. , Adhoute H. , Béjot M.
Published: December 2004

Background/Aims: The ultraviolet (UV) portion of sunlight is involved in the induction and development of skin cancers against which a limited photoprotection may be provided by reduced time of exposure, clothing, and sunscreen applications. The concept of an effective, safe, systemic photoprotection will circumvent many of the shortcomings. The UV‐induced oxidative stress is a cause of DNA damage and a few publications have shown, in humans, minimal benefits, if any, of the oral intake of antioxidant complex, contrasting with the large literature showing beneficial effects in vitro or in animal models.

Methods: We investigated, in 25 healthy individuals, the capacity of an antioxidant complex (AOC) – vitamins (lycopene, β‐carotene, α‐tocopherol), selenium – to reduce UV‐induced damages. The AOC was administered orally, daily during 7 weeks. Before and after irradiations, before and after the intake of the product, six parameters were studied: skin color by chromametry, minimal erythemal dose and, on skin biopsies, sunburn cells (SBCs), p53 detected by immunohistochemistry, pigmentation index, and levels of lipoperoxides (thiobarbituric acid reaction).

Results: After the oral intake of AOC, we observed an elevation of the actinic erythema threshold (+20%, P=0.01) and a general reduction of the UV‐induced erythemas, a reduction of the UV‐induced p53 expression (P<0.05) and of SBCs (P<0.01), and a parallel reduction of the lipoperoxide levels (P<0.01). The pigmentation was increased (P<0.01).

Conclusion: After the oral intake of an antioxidant complex, many parameters of the epidermal defense against UV‐induced damages are significantly improved. The oral intake of AOC could provide a safe, daylong and efficient complement to photo‐protective measures provided by topical and physical agents and may contribute to reduce the DNA damages leading to skin aging and skin cancers.
Functional acclimation to solar UV‐B radiation in Gunnera magellanica, a native plant species of southernmost Patagonia
Authors: GIORDANO C. V. , MORI T. , SALA O. E. , SCOPEL A. L. , CALDWELL M. M. , BALLARÉ C. L.
Published: December 2004

The ecosystems of Tierra del Fuego (in southern Patagonia, Argentina) are seasonally exposed to elevated levels of ultraviolet‐B radiation (UV‐B: 280–315 nm), due to the passage of the ‘ozone hole’ over this region. In the experiments reported in this article the effects of solar UV‐B and UV‐A (315–400 nm) on two UV‐B defence‐related processes: the accumulation of protective UV‐absorbing compounds and DNA repair, were tested. It was found that the accumulation of UV‐absorbing sunscreens in Gunnera magellanica leaves was not affected by plant exposure to ambient UV radiation. Photorepair was the predominant mechanism of cyclobutane‐pyrimidine dimer (CPD) removal in G. magellanica. Plants exposed to solar UV had higher CPD repair capacity under optimal conditions of temperature (25 °C) than plants grown under attenuated UV. There was no measurable repair at 8 °C. The rates of CPD repair in G. magellanica plants were modest in comparison with other species and, under equivalent conditions, were about 50% lower than the repair rates of Arabidopsis thaliana (Ler ecotype). Collectively our results suggest that the susceptibility of G. magellanica plants to current ambient levels of solar UV‐B in southern Patagonia may be related to a low DNA repair capacity.