bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular fingerprinting of TGFß‐treated embryonic maxillary mesenchymal cells
Authors: Pisano M.M. , Mukhopadhyay P. , Greene R.M.
Published: December 2004

The transforming growth factor‐ß (TGFß) family represents a class of signaling molecules that plays a central role in normal embryonic development, specifically in development of the craniofacial region. Members of this family are vital to development of the secondary palate where they regulate maxillary and palate mesenchymal cell proliferation and extracellular matrix synthesis. The function of this growth factor family is particularly critical in that perturbation of either process results in a cleft of the palate. While the cellular and phenotypic effects of TGFß on embryonic craniofacial tissue have been extensively cataloged, the specific genes that function as downstream mediators of TGFß in maxillary/palatal development are poorly defined. Gene expression arrays offer the ability to conduct a rapid, simultaneous assessment of hundreds to thousands of differentially expressed genes in a single study. Inasmuch as the downstream sequelae of TGFß action are only partially defined, a complementary DNA (cDNA) expression array technology (Clontech's AtlasTM Mouse cDNA Expression Arrays), was utilized to delineate a profile of differentially expressed genes from TGFß‐treated primary cultures of murine embryonic maxillary mesenchymal cells. Hybridization of a membrane‐based cDNA array (1178 genes) was performed with 32P‐labeled cDNA probes synthesized from RNA isolated from either TGFß‐treated or vehicle‐treated embryonic maxillary mesenchymal cells. Resultant phosphorimages were subject to AtlasImageTM analysis in order to determine differences in gene expression between control and TGFß‐treated maxillary mesenchymal cells. Of the 1178 arrayed genes, 552 (47%) demonstrated detectable levels of expression. Steady state levels of 22 genes were up‐regulated, while those of 8 other genes were down‐regulated, by a factor of twofold or greater in response to TGFß. Affected genes could be grouped into three general functional categories: transcription factors and general DNA‐binding proteins; growth factors/signaling molecules; and extracellular matrix and related proteins. The extent of hybridization of each gene was evaluated by comparison with the abundant, constitutively expressed mRNAs: ubiquitin, glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH), ornithine decarboxylase (ODC), cytoplasmic beta‐actin and 40S ribosomal protein. No detectable changes were observed in the expression levels of these genes in response to TGFß treatment. Gene expression profiling results were verified by Real‐Time quantitative polymerase chain reaction. Utilization of cDNA microarray technology has enabled us to delineate a preliminary transcriptional map of TGFß responsiveness in embryonic maxillary mesenchymal cells. The profile of differentially expressed genes offers revealing insights into potential molecular regulatory mechanisms employed by TGFß in orchestrating craniofacial ontogeny.
Sustained biochemical remission after interferon treatment may closely be related to the end of treatment biochemical response and associated with a lower incidence of hepatocarcinogenesis
Authors: Suzuki Kenta , Ohkoshi Shogo , Yano Masahiko , Ichida Takafumi , Takimoto Mitsuhiro , Naitoh Akira , Mori Shigeki , Hata Kojiro , Igarashi Kentaro , Hara Hidenori , Ohta Hironobu , Soga Kenji , Watanabe Toshiaki , Kamimura Tomoteru , Aoyagi Yutaka
Published: December 2004

Abstract: Clinical background and incidence of hepatocellular carcinoma (HCC) of patients with chronic hepatitis C who obtained biochemical remission without eradication of virus (biochemical response) after interferon (IFN) treatment was retrospectively analyzed for 755 patients. Annual incidence of HCC was significantly lower in the patients with biochemical response and sustained response than that of the patients that did not show these responses. Logistic regression analysis showed that only the normalization of alanine aminotransferase (ALT) value at the end of IFN treatment was a significant factor for biochemical response. Annual incidence of HCC was significantly lower in the patients who obtained normalization of ALT values at the end of treatment than those who did not. Patients who were younger, who had a lower level of activity and fibrosis indices in histology, higher platelet count, and who were given more higher total dose of IFN were more likely to attain normalization of ALT levels at the end of treatment, and this was related to biochemical response. Low incidence of HCC in patients who obtained normalization of ALT values at the end of treatment was likely because they were in the earlier stage of chronic hepatitis. Active treatment of chronic hepatitis C with interferon in the early phase of the disease may bring about a biochemical response in some patients, even if sustained virological response is not obtained.
Grazer‐induced colony formation in Scenedesmus: are there costs to being colonial?
Authors: Lürling Miquel , Van Donk Ellen
Published: December 2004

Grazer‐induced colony formation in the common green alga Scenedesmus acutus may be interpreted as an anti‐grazer defense. Costs are to be expected because otherwise the protected colonial morph would be the norm. Analysis of growth rates, light harvesting in terms of photosystem II (PSII) efficiency using Xe‐PAM fluorescence measurements and sedimentation rates were compared among unicellular and induced colonial populations. No differences in growth rates and PSII efficiency were detected between unicellular and colonial populations. However, colonial populations had higher settling velocities than unicellular populations. Hence, costs may be attributed to enhanced sinking out of the euphotic zone resulting in reduced growth due to lower light and temperature in deeper water layers.
Effects of plant phenology, nutrients and herbivory on growth and defensive chemistry of plantain, Plantago lanceolata
Authors: Jarzomski C. M. , Stamp N. E. , Bowers M. D.
Published: December 2004

To assess the combined effect of herbivory, nutrient availability and plant phenology on plant mass and defensive chemistry, we conducted a field experiment with plantain (Plantago lanceolata: Plantaginaceae) using three levels of herbivory, three levels of fertilizer and two harvest dates. Shoot mass of the no‐herbivory plants showed a nonlinear response to increased fertilizer such that mass with high fertilizer was no greater than that with low fertilizer. In contrast, shoot mass of the low‐herbivory plants (12% damage) was not influenced by fertilizer, but for high‐herbivory plants (23% damage), there was a positive linear response to increased fertilizer. Increasing nutrient levels caused a decrease in iridoid glycoside concentration. Herbivory did not induce higher iridoid glycoside concentration in leaves of any age. But increasing herbivory resulted in a decrease in the concentration of catalpol in new leaves. Another experiment assessed how leaf age and plant age affected plant defensive chemistry. Total iridoid glycosides increased over 5 weeks, but catalpol only increased in new leaves. Overall, the order of importance in determining variation in iridoid glycoside concentration was plant phenology, nutrient availability and, to a much lesser extent, herbivory.
Roles of odor, taste, and toxicity in the food preferences of lambs: implications for mimicry in plants
Authors: Provenza Frederick D. , Kimball Bruce A. , Villalba Juan J.
Published: December 2004

In the traditional sense, food ingestion consists of prehending, masticating, swallowing, and digesting plant matter. It is also possible to ingest plants without eating them. Volatile compounds are inhaled directly into the lungs and transported from the lungs into the bloodstream. Volatiles in high concentrations could presumably produce toxicosis, without an herbivore ever ingesting a plant in the customary sense. Volatile compounds may be aposematic, serving to warn potential predators of toxins in plants. We conducted three experiments to explore the roles of odor, taste, and toxicity in the food preferences of lambs. The first experiment determined if brief exposure to a novel odor followed by lithium chloride (LiCl)‐induced toxicosis caused lambs to avoid a familiar food that contained the odor. Lambs that sniffed coconut‐flavored barley and then received LiCl subsequently ate less coconut‐flavored barley than lambs that did not receive LiCl. The second experiment determined if lambs were deterred from eating a familiar food by the odor of Astragalus bisulcatus. A. bisulcatus is a malodorous (to humans) sulfur‐containing herb considered unpalatable and toxic. Neither odor nor intraruminal infusions of A. bisulcatus deterred lambs from feeding. The third experiment also determined how the degree of familiarity with the odor of A. bisulcatus, along with toxicosis, influenced preference of lambs for food with or without the odor of A. bisulcatus. Lambs with 8 d exposure to the odor but not given LiCl ate similar amounts of food, with and without the odor of A. bisulcatus, whereas lambs given LiCl showed a mild aversion to food with the odor during testing. Lambs with 1 d exposure to the odor but no LiCl ate similar amounts of food, with and without the odor, whereas lambs given LiCl showed a strong but transient aversion to food with the odor. Collectively, these findings show that lambs responded strongly to novel odors, but their response was transient and depended on the postingestive consequences of toxins and nutrients associated with odor inhalation. Thus, we submit that odor alone, in the absence of toxicosis or nociception, is not a deterrent to herbivores that continually sample foods and adjust intake based on the postingestive effects of toxins and nutrients. It also is unlikely that non‐toxic plants can mimic the odors of toxic plants to avoid herbivory (Batesian mimicry), unless the odors are indistinguishable by herbivores, again because herbivores constantly sample foods.
Ant predation and the cost of egg carrying in the golden egg bug: experiments in the field
Authors: Kaitala Arja , Espadaler Xavier , Lehtonen Risto
Published: December 2004

Golden egg bug (Phyllomorpha laciniata) females lay eggs on the
backs of both female and male conspecifics. Bugs receive eggs voluntarily
and involuntarily, and even when males carry eggs, many eggs are not
fertilised by the carrier. Carrying the eggs of another individual is
unexpected, particularly if egg carrying bears a cost in survival. 
We examined the predation risk associated with egg carrying
experimentally in the field. P. laciniata individuals were
enclosed with workers of one of two ant species, Pheidole pallidula
or Cataglyphis piliscapus, which co‐occur with the bug in the
wild. Pheidole pallidula workers preyed on golden egg bugs and their
eggs, but Cataglyphis piliscapus workers did not. In P.
pallidula enclosures, golden egg bugs carrying larger egg loads were eaten first.  These results suggest that golden egg bugs experience high predation pressure and that egg carrying increases the risk of predation. Due to the direct survival costs associated with egg carrying and the lack of relatedness between the eggs and the carrier, we suggest the golden egg bug as the first known intraspecific parasite in which parasitism is not related to active parental care.
The social organization of free‐ranging fish shoals
Authors: Hoare Daniel J. , Ruxton Graeme D. , Godin Jean‐Guy J. , Krause Jens
Published: December 2004

The phenotypic composition of social groups can affect the foraging efficiency and predation risk of their individual members. In shoaling fishes, active choice of shoal companions on the basis of phenotypic characters such as body length has been reported. In this study, we investigated the phenotypic composition of free‐ranging, multi‐species fish shoals in a temperate freshwater lake. We collected 21 entire shoals, each consisting of up to four species and comprising 3622 fish in total. Shoals were strongly assorted by species, body length, parasite prevalence and parasite load. Using a mark‐recapture procedure involving 785 banded killifish (Fundulusdiaphanus), we found no evidence for shoal fidelity or site fidelity, as individuals from different shoals mixed extensively after just 24 h and ranged all over the study site irrespective of initial capture locations. Killifish showed strong changes in shoal‐size choice over 24 h, and no evidence was found that shoals might break up into sub‐units of individuals that are more phenotypically assorted than their original shoals. The mechanisms by which assortative groups may arise and the consequences of low group fidelity for the evolution of cooperative behaviour are discussed.
Food web structure and the strength of transient indirect effects
Authors: Fox Jeremy W. , Olsen Erik
Published: December 2004

The relative importance of direct and indirect effects in ecological communities remains unresolved. Indirect effects may diminish as they propagate through highly reticulate food webs. We tested this hypothesis by assembling replicate food webs of different complexity in laboratory microcosms, and comparing the transmission of indirect effects through these webs. By providing the top predator (Didinium) with either
one (Paramecium) or two (Paramecium and Colpidium)
species of protists as prey, we created linear or reticulate food webs
where we could examine the transient response of predators to an indirect
effect. Addition of Chlamydomonas, a small alga consumed by
Paramecium, but not by Colpidium, perturbed the system and
generated an indirect effect on Didinium. We expected the
proportional response of Didinium to Chlamydomonas addition
would be smaller in the reticulate web containing alternative,
unperturbed prey (Colpidium). We measured predator response as
predator yield, the maximum number of predators produced prior to
overexploitation of prey and subsequent predator decline. The ratio of
yield in perturbed bottles to yield in unperturbed bottles measures the
proportional response of Didinium to Chlamydomonas
addition. We expected this ratio to be smaller with Colpidium present. Contrary to expectations, alternative prey enhanced rather than diminished predator response to the perturbation. This resulted from competition between the prey species, a factor ignored in some simple verbal arguments. Food web complexity may have unanticipated consequences for the strength of indirect effects.
Investigating the relationship between neighbor root biomass and belowground competition: field evidence for symmetric competition belowground
Authors: Cahill, Jr. James F. , Casper Brenda B.
Published: December 2004

Little is known about how small‐scale variation in neighbor biomass can influence the strength of root competition experienced by an individual plant. In this study, modified root exclusion tubes were used to vary the accessibility of the soil space surrounding Amaranthus
retroflexus target plants to the neighboring plants. A gradient of root accessibility was created by drilling varying numbers of holes into standard root exclusion tubes, made of 15 cm diameter PVC pipe. Belowground competitive intensity, defined as biomass reduction due to root interactions alone, relative to growth in the absence of neighbors, was then measured along the resulting gradient of neighbor root densities. At low neighbor root abundances the strength of belowground competition was proportional to neighbor root biomass, consistent with prior evidence that belowground competition is symmetric. If belowground competition were asymmetric, neighbor roots should have had little effect on target plants when they are rare relative to those of the target plant. At higher neighbor root abundances, belowground competitive intensity should increase rapidly. The strong relationship found between neighbor root biomass and belowground competitive intensity suggests relatively small variations in root biomass could lead to large variations in belowground competition. Reduced belowground competition in areas with low root biomass could have important implications for the establishment and growth of poor belowground competitors, suggesting a mechanism by which species coexistence may occur despite extremely intense root competition.
The prevalence of non‐breeders in raptor populations: evidence from rings, radio‐tags and transect surveys
Authors: Kenward R. E. , Walls S. S. , Hodder K. H. , Pahkala M. , Freeman S. N. , Simpson V. R.
Published: December 2004

Age‐specific survival and breeding (ASSAB) models were developed with data from 146 common buzzards (Buteo buteo) radio‐tagged in southern Britain during 1990–1998, in a 120‐km2 study area that had on average 25 egg‐laying pairs. Survival checks were aided by philopatric behaviour and a maximum annual tag failure rate of 7%: minimum survival rates, that were estimated by assuming death of buzzards with lost tags, were close to maximum rates that were estimated using only the recorded deaths. First‐year survival rate estimates for 35 buzzards fitted in 1990–1991 with 25–30‐g backpack radios were 69–74% (minimum‐maximum), close to the 61–71% for 16 buzzards with 12‐g tail‐mount radios; the backpacks transmitted for 2–4 yr. Overall survival rates were 66–73% in the first year, 91–97% in the second and 88–91% thereafter. Survival estimates from 288 recent British ring recoveries were lower in the first and second years, at 55% and 75%, but similar (88%) thereafter. Most deaths were from natural causes (40%) or interaction with artefacts (36%). ASSAB models, from radio‐tracking and the observed 1.71 young clutch−1, predicted breeding by 16–21% of all the buzzards present in spring, or up to 25% with the minimum likely productivity of 1.4 young clutch−1 or 12% net emigration. Ringing data predicted breeding rates of 33–38%. The models were tested with density data from nest surveys and new radio‐corrected‐transect and truncation‐mark‐resighting estimates of buzzard numbers. Surveys in autumn and late winter estimated breeding rates of 21–25%. The high non‐breeder density in spring, of three other buzzards for each paired bird with eggs, has important implications for understanding evolutionary fitness, predation and population ecology.
Defoliation‐induced enhancement of total aboveground nitrogen yield of grasses
Authors: Green Ronald A. , Detling James K.
Published: December 2004

We conducted an experiment in a northern mixed‐grass prairie at Wind Cave National Park, South Dakota, USA to evaluate the effect of defoliation frequency on aboveground net primary production (ANPP), shoot nitrogen concentration, and aboveground N yield of graminoids. ANPP was significantly reduced at weekly and biweekly defoliation frequencies, but unaffected relative to unclipped controls at monthly and bimonthly frequencies. By contrast, clipping at all frequencies increased shoot N concentration above that of controls, and this increase was greatest at monthly or more frequent defoliations. Total aboveground N yield and potential N yield to grazers were greatest at intermediate (bimonthly to biweekly) frequencies. We suggest that grazers may maximize their nutritional status in this system by periodically regrazing areas at frequencies near the approximately monthly optimum that we observed.
Inferences about nested subsets structure when not all species are detected
Authors: Cam Emmanuelle , Nichols James D. , Hines James E. , Sauer John R.
Published: December 2004

Comparisons of species composition among isolated ecological communities of different size have often provided evidence that the species in communities with lower species richness form nested subsets of the species in larger communities. In the vast majority of studies, the question of nested subsets has been addressed using information on presence‐absence, where a “0” is interpreted as the absence of a given species from a given location. Most of the methodological discussion in earlier studies investigating nestedness concerns the approach to generation of model‐based matrices corresponding to the null hypothesis of a nonnested pattern. However, it is most likely that in many situations investigators cannot detect all the species present in the location sampled. The possibility that zeros in incidence matrices reflect nondetection rather than absence of species has not been considered in studies addressing nested subsets, even though the position of zeros in these matrices forms the basis of earlier inference methods. These sampling artifacts are likely to lead to erroneous conclusions about both variation over space in species richness, and the degree of similarity of the various locations. Here we propose an approach to investigation of nestedness, based on statistical inference methods explicitly incorporating species detection probability, that take into account the probabilistic nature of the sampling process. We use presence‐absence data collected under Pollock's robust capture‐recapture design, and resort to an estimator of species richness originally developed for closed populations to assess the proportion of species shared by different locations. We develop testable predictions corresponding to the null hypothesis of a nonnested pattern, and an alternative hypothesis of perfect nestedness. We also present an index for assessing the degree of nestedness of a system of ecological communities. We illustrate our approach using avian data from the North American Breeding Bird Survey collected in Florida Keys.
Factors influencing movement probabilities of a nomadic food specialist: proximate foraging benefits or ultimate gains from exploration?
Authors: Bennetts Robert E. , Kitchens Wiley M.
Published: December 2004

We examined the factors that influenced movement probabilities of snail kites (Rostrhamus sociabilis) in Florida, USA, based on birds with radio transmitters (n=282) during a three‐year period from April 1992 through April 1995. We focused on the hypotheses that increased movement probabilities were in response to low food availability or low water levels; the latter also implying low food availability for this species. An alternative hypothesis was that snail kites exhibit exploratory behavior, and corresponding increased movement probabilities, during periods of high food availability.  Movement probabilities were not consistent with the hypotheses that low water levels or low food availability were the proximate cues to initiate movement from one wetland to another. Movement probabilities were higher during periods of relatively high food availability and were not associated with water levels; thus were consistent with the hypothesis that snail kites exhibited exploratory behavior during times of food abundance. However, we do not believe that our results are in conflict with previous reports of increased movement during extreme food scarcity; rather, that these hypotheses are not mutually exclusive and reflect different resource levels. During extreme drying events, food becomes virtually unavailable and birds must either move or die, but during times of food abundance there may be an advantage of exploratory behavior. Given that local drying events occur at frequencies of approximately every 5–10 yr in this environment, having explored wetlands throughout their range reduces the need for “blind” searching for suitable alternative habitats when such events do occur.
Ignorant seed predators and factors affecting the seed survival of a tropical palm
Authors: Brewer Steven W. , Webb Molly A. H.
Published: December 2004

In addition to acting as seed predators, some terrestrial mammals bury seeds via scatter hoarding. This study system used two permanent plots in examining the interaction between small rodents and the seeds of the palm Astrocaryum mexicanum. We tested how experimental burial, and fruiting status of the parent, distance to the parent, seed size, and microsite characteristics affect the survival of these seeds. Up to 34% of the buried seeds that were exposed only to ignorant rodent foragers (individuals not responsible for burial) survived. In comparison, less than 1% of seeds buried by scatter hoarding rodents survived in previous studies, a percentage that is comparable to the low survival of unburied seeds in this study (<2%). Although unburied seeds had very low survival, increasing distance and/or seed density positively affected survival of unburied seeds. Distance to parent had no effect on buried seed survival.  Buried seed survival was most strongly and significantly determined by the fruiting status of the trees under which they occurred. Seeds experienced significantly greater predation if buried under “parent” trees that fruited during the experiment. Buried seed survival was also negatively affected by germination, as germination may signal the presence of a seed to foraging rodents. There was some indication of a positive effect of tree density on seed survival between the two plots, whereas differences in rodent abundance appear to have no effect on seed survival. Seed size and microsite characteristics had no significant effect on buried seed survival, likely due to the greater proportional effects of other factors and the longevity of A. mexicanum seeds. The results of this study were used to generate a hypothetical causal network showing how comparatively low recovery of buried seeds by ignorant foragers – combined with processes determining the removal of scatter hoarding foragers from their scattered seed caches – may affect seedling recruitment in A. mexicanum.
Compensation behaviour by insect herbivores and natural enemies: its influence on community structure
Authors: Kondoh Michio , Williams Iain S.
Published: December 2004

Insect herbivores feeding on low‐quality plants often compensate by increasing their consumption of plant tissue. This usually results in a longer developmental time leading to a higher vulnerability to natural enemies. This has been termed the slow‐growth, high‐mortality hypothesis. To explore how compensation may shape the species composition of herbivore and natural enemy populations, we present a mathematical model of a tri‐trophic system incorporating both the nutritional quality of plants and herbivores, and the compensatory ability of herbivores and their natural enemies. Using this model we predict the abundance of herbivores and natural enemies, and some characteristics of the composition of species of insect communities along a gradient of plant nutritional quality. Specifically, we make the following predictions: 1) In the absence of natural enemies, the abundance of the juvenile herbivores increases with plant quality, and only highly compensating herbivores persist at low plant nutritional quality. 2) If natural enemies are present, the abundance of the juvenile herbivores decreases with increasing plant quality due to more effective suppression by the natural enemies. Poorly compensating herbivores increase while their highly compensating counterparts decrease with lowered plant quality. 3) When the plants have low nutritional quality, natural enemies will only persist when either very highly compensating herbivores are present or if the natural enemy itself is highly compensating. 4) The abundance of adult herbivores in a community with natural enemies can either increase or decrease with increasing plant quality depending on the compensatory abilities of herbivores and natural enemies.
Do southern African songbirds live longer than their European counterparts?
Authors: Peach Will J. , Hanmer Dale B. , Oatley Terence B.
Published: December 2004

Understanding life history evolution in tropical and southern hemisphere birds has been hindered by a paucity of knowledge of key life history traits and this is particularly true of African songbirds. Here we use a unique long‐term mark‐recapture data set collected over 16 years in Malawi (latitude 16°S) to estimate adult survival rates for 28 African passerine species. Survival of these and 11 other African songbirds (taken from the literature) showed a bi‐modal distribution with annual survival of insectivores and nectarivores (bulbuls, thrushes, warblers and sunbirds) averaging 72% (quartiles 63–80%) compared to 54% (50–62%) in granivores (weavers, finches and canaries). The mean adult life expectancy of African insectivores and nectarivores (3.1 yr) was more than twice that of related European insectivores (1.4 yr) and nearly twice that of African granivores (1.6 yr). These marked differences in survival were highly significant after controlling for body mass and phylogeny. Among African songbirds there was a strong negative correlation between adult survival and clutch size with granivores laying relatively large clutches and living relatively short lives. We hypothesize that these differing life history trade‐offs reflect variation in the seasonality of food resources whereby survival rates of northern temperate songbirds may be limited by food availability and cold weather during winter, while survival of southern African granivores may be limited by the influence of a variable and unpredictable rainfall regime on seed availability.
Revising the convergence hypothesis of avian use of honeydew: evidence from Dominican subtropical dry forest
Authors: Latta Steven C. , Gamper Heather A. , Tietz James R.
Published: December 2004

A honeydew‐producing scale insect (family Margarodidae, tribe Xylococcini, genus Stigmacoccus) was found associated with the tree Bursera simaruba in subtropical dry forests at elevations of 100–400 m on the south side of the Sierra de Bahoruco, Pedernales Province, Dominican Republic. At two study sites, 91% of Bursera trees supported locally dense populations of Margarodidae. Fifteen species of birds were observed foraging on the honeydew, but most observations were of the winter resident Cape May warbler (Dendroica tigrina) and black‐throated blue warbler (D. caerulescens), and the permanent resident bananaquit (Coereba flaveola) and black‐crowned palm tanager (Phaenicophilus palmarum). The Cape May warbler actively defended the honeydew resource but frequency of use of honeydew was influenced by the close presence of flowering agave and scale insect density. Data suggest that honeydew may be a critical component of the diet of this species especially during the late winter dry‐season. Hymenopteran insects also were observed feeding on honeydew, but rates of consumption did not approach that of avian species. The occurrence of this phenomenon in Dominican dry forest is discussed in light of the convergence hypothesis of bird use and defense of homopteran honeydew in which it is proposed that birds are able to maintain relationships with scale insects in moist, warm temperate forests because it is in these climates where ant abundance is low. We suggest that our observation of a well‐developed bird–homopteran system in classic subtropical dry forest supports the proposed mechanism of reduced competition with ants allowing bird use of honeydew, but we suggest that a broader array of especially insular habitats which may be relatively depauperate in terms of ants also can be expected to support bird–homopteran systems.
The effects of habitat destruction in finite landscapes: a chain‐binomial metapopulation model
Authors: Hill Mark F. , Caswell Hal
Published: December 2004

We present a stochastic model for metapopulations in landscapes with a finite but arbitrary number of patches. The model, similar in form to the chain‐binomial epidemic models, is an absorbing Markov chain that describes changes in the number of occupied patches as a sequence of binomial probabilities. It predicts the quasi‐equilibrium distribution of occupied patches, the expected extinction time (
image

), and the probability of persistence (

image

) to time x as a function of the number N of patches in the landscape and the number S of those patches that are suitable for the population. For a given value of N, the model shows that: (1)

image

and

image

are highly sensitive to changes in S and (2) there is a threshold value of S at which

image

declines abruptly from extremely large to very small values. We also describe a statistical method for estimating model parameters from time series data in order to evaluate metapopulation viability in real landscapes. An example is presented using published data on the Glanville fritillary butterfly, Meltiaea cinxia, and its specialist parasitoid Cotesia melitaearum. We calculate the expected extinction time of M. cinxia as a function of the frequency of parasite outbreaks, and are able to predict the minimum number of years between outbreaks required to ensure long‐term persistence of M. cinxia. The chain‐binomial model provides a simple but powerful method for assessing the effects of human and natural disturbances on extinction times and persistence probabilities in finite landscapes.
Describing and quantifying interspecific interactions: a commentary on recent approaches
Authors: Abrams Peter A.
Published: December 2004

There has been a recent resurgence of attempts to measure the strengths of interspecific interactions in biological communities. Two recent reviews have compared the performances of different measures of interaction strength using simulations. The goal of obtaining measures of interaction strength is based on the premise that such measures will achieve a closer connection between theory and experiment in community ecology. The present article disputes this premise. Because interactions are typically nonlinear, single numerical measures are generally poor characterizations. Typically, the functional dependencies of growth rates on population densities are unknown. Lacking more information about the form of these functions, the results of most population manipulations make very limited contributions to the construction of dynamic models of communities. Even if all effects of population densities on per capita growth rates were linear, performing all possible removal experiments will frequently fail to identify the constants of proportionality. Many misconceptions about the meaning and measurement of interaction coefficient persist. More extensive natural history observations and use of more flexible short‐term experiments are advocated as approaches that will aid in constructing mathematical models of interspecific interactions.
Female‐biased density‐dependent dispersal of a tephritid fly in a fragmented habitat and its implications for population regulation
Authors: Albrectsen Benedicte , Nachman Gösta
Published: December 2004

The aim of this study was to quantify the rate of dispersal as a response to density in the specialist tephritid fly Paroxyna plantaginis (the main seed predator on its patchily distributed host plant, Tripolium vulgare, Asteraceae). Marked flies were released at three different fly densities in artificial host patches. The individual histories of recaptures were recorded as well as migration between patches and invasion by unmarked flies. The loss of marked flies relative to initial density was analysed using maximum likelihood estimation. Females generally had the highest loss rate. When comparing a density‐independent model with a density‐dependent model of the loss rate, the density‐dependent model won four times out of six for the females but not a single time for the males. A stronger immigration rate of females relative to males supported the suggested female‐biased dispersal. This indicates a sit‐and‐wait strategy for the territorial males and a pre‐emptive competition strategy for egg‐laying substrates for the females. These results may be of general importance for non‐frugivorous tephritid systems with unpredictable and almost ephemeral accessibility to host plants and with a dynamics characterised by a high turnover rate and high attack levels. The study presents a method for measuring the propensity of individuals to leave an area as a response to local density. It is further an example of the consequences individual behavioural responses may have on the population dynamics of a patchy population.
Hormaphis hamamelidis and gall size: a test of the plant vigor hypothesis
Authors: Rehill Brian J. , Schultz Jack C.
Published: December 2004

We tested the Plant Vigor Hypothesis by determining the distribution of galls formed on leaves of witch hazel, Hamamelis virginiana, by the aphid Hormaphis hamamelidis, and by determining various factors that affect the fecundity of the gall‐forming fundatrices. We also studied the role of the fundatrix in host plant manipulation. While the mean number of galls per leaf was low, galls had an aggregated distribution among leaves. Among trees, the average number of galls per leaf was not related to the mean leaf size, contrary to the preference prediction of the Plant Vigor Hypothesis. While fundatrices preferred the distal leaves of buds, which grew more than the proximal leaves, being on distal leaves conferred no increase in fecundity for fundatrices, contrary to predictions of the Plant Vigor Hypothesis. Gall size was the factor that explained the largest proportion of variation in fundatrix fecundity; fundatrix size explained somewhat less of the variation. Also, gall position on the leaf, number of aphid galls on the leaf, and on which leaf of the bud the gall was located all played small, statistically significant roles in explaining fundatrix fecundity, but their effects were variable between experiments. Removal of fundatrices shortly after galls had enclosed them limited the growth of galls, indicating the role of the fundatrices in gall growth. We compare and contrast this system versus other gall‐forming insects, as well as discuss the adaptive significance of the aphid manipulation of the host plant. Much of the data contradict predictions of the Plant Vigor Hypothesis, and we discuss how gall size, as a measure of plant growth caused by insect manipulation, explains the observed patterns.
Intraoral myxoid nerve sheath tumour
Authors: Schortinghuis J , Hille JJ , Singh S
Published: December 2004

A case of an intraoral myxoid nerve sheath tumour of the dorsum of the tongue in a 73‐year‐old Caucasian male is reported. This case describes the oldest patient with this pathology to date. Immunoperoxidase staining for neuron‐specific enolase (NSE) and epithelial membrane antigen (EMA) expression demonstrated the perineural origin of the lesion.
Interaction between leucocytes and human spermatozoa influencing reactive oxygen intermediates release
Authors: Frączek Monika , Sanocka Dorota , Kurpisz Maciej
Published: December 2004

The relationship between the presence of white blood cells (WBCs) and the fertilizing potential of human semen is still an open question. It is well known that the presence of leucocytes in human semen can be related to the production of reactive oxygen intermediates (ROI). Semen samples were obtained from 15 normozoospermic men and leucocytes were isolated from heparinized blood drawn from 15 volunteers. Lucigenin and luminol‐mediated chemiluminescence assays were used to determine reactive oxygen species (ROS) generation by non‐activated or activated leucocytes through 12‐myristate‐13‐acetate or N‐formyl‐methionyl‐leucyl‐phenyalanine (FMLP) before the addition of spermatozoa isolated by swim‐up or Percoll procedures. All spermatozoal fractions used in this study were characterized by defining their motility, morphology and viability. The levels of ROS formation by non‐activated as well as stimulated leucocytes were significantly decreased after addition of swim‐up separated spermatozoa (p < 0.01). The ability to inhibit the basal chemiluminescence was of lower degree for spermatozoa isolated from 90% Percoll fractions than for swim‐up sperm. However, addition of sperm cells from 47% Percoll fraction was found to increase both lucigenin and luminol signals. Moreover, the determined ROI levels changed depending on the type of inducing factor used for oxidative burst. Then, spermatozoa selected by swim‐up procedure although with only slightly higher viability and morphology than sperm obtained from 90% Percoll fraction clearly exhibited much higher capacity to inhibit ROI secretion by receptor‐stimulated leucocytes (FMLP‐activation) than Percoll fractionated sperm. Such results may indicate that within normal semen may exist sperm subpopulations with different biochemical mechanisms controlling the interaction between spermatozoa and contaminating leucocytes. When ROI levels contained in normozoospermic semen are dependent on the WBCs activation, it seems that spermatozoa with preserved normal functional competence are able to defend themselves against leucocytes‐derived ROI. Also for normozoospermic ejaculates, swim‐up sperm may improve semen antioxidant characteristics when comparing with Percoll (90%) separated sperm. It may help for optimal sperm preparation when assisting to infertility treatment.
In situ expression of Granzyme B and Fas‐ligand in the liver of viral hepatitis
Authors: Ibuki Naohisa , Yamamoto Kazuhide , Yabushita Kazuhisa , Okano Nobuaki , Okamoto Ryoichi , Shimada Noriaki , Hakoda Tomomi , Mizuno Motowo , Higashi Toshihiro , Tsuji Takao
Published: December 2004

Abstract:  Background/Aims: The molecular mechanism involved in hepatocellular injury in viral hepatitis remains to be clarified.

Methods: We investigated the in situ expression of effector molecules of cytotoxic T lymphocytes such as Fas‐ligand (Fas‐L), perforin and Granzyme B (Gr‐B) immunohistochemically in liver tissues from 20 patients with chronic hepatitis B (CHB) and C (CHC). The degree of cell infiltration was analysed semi‐quantitatively and compared with the histological activity index (HAI). Fas‐L was expressed in both CD4 and CD8 T‐cells in the portal tract as well as in the parenchyma.

Results: Immunostaining of serial sections demonstrated that mononuclear cells at interface hepatitis and focal necrosis were mainly Fas‐L positive CD8 T‐cells. On the other hand, the expression of perforin or Gr‐B was limited to a few mononuclear cells in the portal tract and parenchyma. Semi‐quantitative analysis showed a positive correlation between HAI and the grade of infiltration of CD8 T‐cells or Fas‐L‐positive cells, while the correlation was not apparent between HAI and the number of Gr‐B positive cells. The expression of these molecules was not different between types of viruses.

Conclusions: These results suggest that Fas‐L‐positive CD8 T‐cells play a major role in the pathogenesis of liver cell injury in chronic hepatitis.
Raised serum ferritin predicts non‐response to interferon and ribavirin treatment in patients with chronic hepatitis C infection
Authors: Distante S , Bjøro K , Hellum KB , Myrvang B , Berg JP , Skaug K , Raknerud N , Bell H
Published: December 2004

Background/Aim:

Previous studies have indicated that response to interferon therapy is inversely proportional to the amount of body iron stores. We have studied the relationship between serum ferritin, transferrin saturation, liver iron, presence of HFE‐C282Y gene mutation and response to treatment in patients with chronic hepatitis C infection.

Methods:

Two hundred and fifty‐six naive, HCV‐RNA positive patients (60% males, median age 38 years, range 21–70) were treated with interferon and ribavirin for 6 months. Iron indices and the presence of the C282Y mutation were measured. In 242 (94%) patients iron deposition were determined by Perls staining method. Patients with negative HCV‐RNA at 6 months after the end of treatment were defined as sustained viral responders.

Results:

Non‐responders (n = 127) had significantly higher median s‐ferritin values compared with sustained viral responders (130 µg/L vs. 75 µg/L P < 0.001). There was no difference in transferrin saturation among the two response groups. Only 23% (4/7) of patients with Perls grade 1 in liver biopsies responded to treatment vs. 54% (122/225) patients without iron deposition (P = 0.02), however, 10/13‐non‐responders had HCV genotype one. Two patients (0.8%) were homozygous for the C282Y mutation, 36 patients were heterozygous (14%). Among mutation carriers 26/38 achieved sustained response compared with 102/216 non‐carriers (68% vs. 48%, P = 0.02). In a multivariate analysis s‐ferritin (P = 0.030) and C282Y carrier status (P = 0.012) remained independent predict of sustained response.

Conclusions:

Raised s‐ferritin values predicate non‐response to interferon‐ribavirin therapy in hepatitis C patients. Response rate in C282Y mutation carriers seems greater than in non‐carriers.
Is it possible to monitor mammal population changes from counts of road traffic casualties? An analysis using Bristol's red foxes Vulpes vulpes as an example
Authors: BAKER PHILIP J. , HARRIS STEPHEN , ROBERTSON CHARLES P. J. , SAUNDERS GLEN , WHITE PIRAN C. L.
Published: December 2004

1. Counts of road traffic casualties (RTCs) have been proposed as one potential method of monitoring changes in the abundance of several mammal species in Britain. However, before such schemes are implemented, it is vital that the relationship between animal density and RTCs is verified and quantified. In this paper, we analyse data collected as part of a long‐term study of red foxes Vulpes vulpes in Bristol, UK to determine whether RTCs reflected changes in fox numbers.

2. Associations between fox density and RTC counts were examined using data collected from throughout Bristol during 1978–84 (spatial model) and from an intensive longitudinal study in the north‐west of the city during 1990–94 (temporal model). For both sets of data, there was a significant relationship between fox density and RTCs; in the case of the temporal model, this was only evident after the data had been manipulated by calculating running means across seasons. These regression models only explained 58% and 43% of the variance observed in the data, respectively.

3. In both analyses, there was a significant difference between the distribution of casualties and the availability of different road types; more foxes were killed on major category roads (e.g. motorways, A‐roads). Incorporating the length of each road category in each region in the spatial model improved the variance explained to 81%. This level of precision would be sufficient for a national monitoring programme. However, we were able to minimize or eliminate a number of factors that could potentially confound the use of RTCs for a national monitoring programme; these factors are discussed in detail. At present, we conclude that further investigation into the validity and precision of this technique is required for a range of mammal species before it could be used in a national monitoring programme.
No evidence of hSNF5/INI1 point mutations in choroid plexus papilloma
Authors: Mueller W. , Eum J.‐H. David , Laß U. , Paulus W. , Sarkar C. , Bruck W. , Von Deimling A.
Published: December 2004

Choroid plexus carcinomas (CPC) have been shown to carry mutations in the hSNF5/INI1 gene on chromosomal arm 22q11.2. A recent study on choroid plexus papillomas (CPP) and CPC revealed frequent losses of chromosomal portions on the long arm of chromosome 22 (−22q). The region harbouring hSNF5/INI1 was affected in 47% of the CPP and 73% of the CPC, respectively. −22q occurred more frequently in adult than in infantile CPP suggesting different pathogenetic pathways for these tumours. These findings may indicate a potential tumour suppressor gene function of hSNF5/INI1 in a subset of choroid plexus tumours. In order to examine its potential role in the pathogenesis of choroid plexus tumours, we analysed exons 1–9 of hSNF5/INI1 by SSCP analysis in a series of 21 formalin‐fixed and paraffin‐embedded CPP. No alterations in migratory patterns were detected. These data indicate that somatic point mutations of hSNF5/INI1 do not play a role in the pathogenesis of CPP and that CPP and CPC may arise by two different molecular pathways.