bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of sperm storage and timing of mating on offspring sex ratios in the yellow dung fly Scatophaga stercoraria
Authors: Seal Nicola J.
Published: March 2003

1. Offspring sex ratios in the yellow dung fly Scatophaga stercoraria were examined in the laboratory.

2. Previous work indicated that females using previously stored sperm to fertilise their eggs produced male‐biased sex ratios. This result may have been due to female influences or the effects of sperm storage per se.

3. This pattern was not reproduced in the study presented here. Females that were allowed to mate just prior to oviposition produced similarly male‐biased sex ratios to those females that used previously stored sperm to fertilise their clutch.

4. Captive‐reared females may have perceived a lack of males in the population and thus produced a male‐biased offspring sex ratio. Alternatively, gamete ageing or extra‐chromosomal sex ratio distorters may have produced the male bias.
Dynamic effects of parasitism by an endoparasitoid wasp on the development of two host species: implications for host quality and parasitoid fitness
Authors: Harvey Jeffrey A.
Published: March 2003

1. The study reported here examined growth and developmental interactions between the gregarious larval koinobiont endoparasitoid Cotesia glomerata (Hymenoptera: Braconidae) and two of its hosts that vary considerably in growth potential: Pieris rapae and the larger P. brassicae (Lepidoptera: Pieridae). At pupation, healthy larvae of P. brassicae are over twice as large, in terms of fresh body mass, as those of P. rapae.

2. Clutch size of C. glomerata was manipulated artificially, and the relationship between parasitoid burden and the maximum weight of the parasitised host (= host–parasitoid complex) was measured. In both hosts, the maximum complex weight was correlated positively with parasitoid burden. Compared with unparasitised hosts, however, the growth of P. rapae was increased at significantly lower parasitoid burdens than in P. brassicae. Emerging wasp size was correlated negatively with parasitoid burden in both host species, whereas development time was less affected.

3. After larval parasitoid egress, the weight of the host carcass increased slightly, but not significantly, with parasitoid burden, although there was a strong correlation between the proportion of host mass consumed by C. glomerata larvae during development and parasitoid burden.

4. Clutch size was generally correlated positively with instar parasitised in both hosts, and greater in P. brassicae than in P. rapae. Sex ratios were much more female biased in L1 and L2 P. rapae than in all other host classes. Adult parasitoid size was correlated inversely with host instar at parasitism, and wasps emerging from P. brassicae were larger, and completed development faster, than conspecifics emerging from P. rapae.

5. The data reveal that parasitism by C. glomerata has profound species‐specific effects on the growth of both host species. Consequently, optimality models in which host quality is often based on host size at parasitism or unparasitised growth potential may have little utility in describing the development of gregarious koinobiont endoparasitoids. The results of this investigation are discussed in relation to the potential effectiveness of gregarious koinobionts in biological control programmes.
Habitat selection in a large orb‐weaving spider: vegetational complexity determines site selection and distribution
Authors: Mcnett Bonnie Jean , Rypstra Ann Lundie
Published: March 2003

1. The distribution of the large orb‐weaving spider Argiope trifasciata in old field habitats of North America and the habitat selection process this species used was studied for 2 years.

2. Because web spiders have limited dispersal abilities and an energetically costly prey capture device, they do not have the ability to sample potential foraging sites. Structural complexity of the vegetation to which the web must be attached is relatively easy to assess. The hypothesis that the structural complexity is a primary factor in determining initial web site selection was tested both by relating the natural distribution of the spiders across habitats to vegetational complexity and by manipulating the complexity of the habitats in a series of experiments.

3. Argiope trifasciata was not distributed evenly among three old field vegetation types. Habitat complexity was related to spider density in both years although no measure of insect activity, prey capture, or prey consumption was correlated with spider distribution.

4. Three experimental manipulations were conducted to test the impact of habitat structure on spider establishment: (1) the amount of natural vegetation was reduced, (2) structures were added to a simple habitat, and (3) the complexity of the structures added was varied. In each case, spiders were introduced and establishment of webs was monitored. In all manipulations, spider establishment was related to the complexity of the substrate available.

5. These results are important for understanding the cues that influence foraging site selection and therefore provide insight into the distribution of species with limited dispersal abilities and high site investment requirements.
Nutritional benefits of intraguild predation and cannibalism among generalist and specialist phytoseiid mites
Authors: Schausberger Peter , Croft Brian A.
Published: March 2003

1. Intraguild predation and cannibalism are common among predaceous phytoseiid mites (Acari, Phytoseiidae) but the nutritional benefits gained by these processes are poorly understood.

2. The study reported here addressed the questions of whether cannibalism and intraguild predation provide different nutritional benefits and whether the ability to utilise cannibalism and intraguild predation is linked to the diet specialisation of phytoseiid mites. Specialists tested werePhytoseiulus macropilis,Galendromus occidentalis, andNeoseiulus longispinosus;generalists tested wereAmblyseius andersoni,Neoseiulus cucumeris, andNeoseiulus fallacis.

3. All generalists and the specialistP. macropiliswere able to complete juvenile development with both con‐ and hetero‐specific prey. Juvenile development of generalists was shorter with heterospecific prey than with conspecific prey, whereas development of the specialistP. macropilisdid not differ between prey types. Only a fewN. longispinosusandG. occidentalis, both specialists, reached adulthood by cannibalism but none reached adulthood by intraguild predation.

4. All generalists were able to sustain oviposition by intraguild predation.Neoseiulus cucumerisandA. andersonilaid more eggs with heterospecific prey than with conspecific prey, whereasN. fallacishad similar oviposition rates with both prey types. No specialist sustained oviposition by intraguild predation or cannibalism.

5. Overall, generalists gained equal or more nutritional benefits by intraguild predation than by cannibalism and were able to utilise phytoseiid intraguild prey as an alternative food source. Specialists gained equal or more nutritional benefits from cannibalism than from intraguild predation. For specialists, con‐ and hetero‐specific phytoseiids may be considered only a supplemental food.
Females of the European beewolf preserve their honeybee prey against competing fungi
Authors: Strohm Erhard , Linsenmair K. Eduard
Published: March 2003

1. Females of the European beewolf Philanthus triangulum (Hymenoptera, Sphecidae) provision brood cells with paralysed honeybees as larval food. Because brood cells are located in warm, humid locations there is a high risk of microbial decomposition of the provisions. Low incidence of fungus infestation (Aspergillus sp.) in nests in the field suggested the presence of an anti‐fungal adaptation.

2. To test whether the paralysis caused the protection from fungus infestation, the timing of fungus growth on bees that were freeze‐killed, paralysed but not provisioned, and provisioned regularly by beewolf females was determined. Fungus growth was first detected on freeze‐killed bees, followed by paralysed but not provisioned bees. By contrast, fungus growth on provisioned bees was delayed greatly or even absent. Thus, paralysis alone is much less efficient in delaying fungus growth than is regular provisioning.

3.

Observations  of beewolves in their nests revealed that females lick the body surface of their prey very thoroughly during the period of excavation of the brood cell.

4. To separate the effect of a possible anti‐fungal property of the brood cell and the licking of the bees, a second experiment was conducted. Timing of fungus growth on paralysed bees did not differ between artificial and original brood cells. By contrast, fungus growth on bees that had been provisioned by a female but were transferred to artificial brood cells was delayed significantly. Thus, the treatment of the bees by the female wasp but not the brood cell caused the delay in fungus growth.

5. Beewolf females most probably apply anti‐fungal chemicals to the cuticle of their prey. This is the first demonstration of the mechanism involved in the preservation of provisions in a hunting wasp. Some kind of preservation of prey as a component of parental care is probably widespread among hunting wasps and might have been a prerequisite for the evolution of mass provisioning.
What causes male‐biased sex ratios in mature damselfly populations?
Authors: Stoks Robby
Published: March 2003

1. Several hypotheses to account for biased sex ratios in mature insect populations were tested by monitoring two field populations of the damselfly Lestes sponsa and by performing experiments in field cages. The population sex ratios are heavily male biased in this species.

2. The observed sex ratio at emergence was even and both sexes emerged synchronously. Females had longer maturation times but these were insufficient to explain the observed sex ratio shift.

3. Mass increases during maturation were consistently larger in females. In agreement with this, immature females made more flights per unit of time, which should make them more vulnerable to predation, however maturation probabilities were lower in females only in one field cage experiment. This inconsistency may be due to long bad weather conditions. Interestingly, predators reduced mass increase and this reduction was larger in females than in males.

4. Calculations based on the sex specific maturation times show that only slightly lower daily survival probabilities during maturation in females are enough to generate the observed sex ratio shift.

5. Mature survival was higher in males than in females in one field population but not in another, indicating that this cannot be a general mechanism causing the sex ratio. A higher maturation probability in males is therefore the most plausible mechanism causing the sex ratio shift in damselfly populations.
The role of resources and natural enemies in determining the distribution of an insect herbivore population
Authors: Williams Iain S. , Jones T. Hefin , Hartley Susan E.
Published: March 2003

1. Both resources and natural enemies can influence the distribution of a herbivore. The ideal free distribution predicts that herbivores distribute themselves to optimise utilisation of resources. There is also evidence of herbivores seeking out refuges that reduce natural enemy attack (enemy‐free space). Which of these theories predominates in a thistle–tephritid Terellia ruficauda (Diptera: Tephritidae)–parasitoid interaction is examined.

2. The plant, Cirsium palustre, had a contagious distribution approximated by the negative binomial distribution. Terellia ruficauda foraged preferentially and oviposited on isolated plants although its larvae gained neither nutritional benefit nor reduced natural enemy pressure from such behaviour.

3. Parasitoids of T. ruficauda foraged and oviposited more frequently on isolated than on crowded T. ruficauda, resulting in inverse density‐dependent parasitoid attack at all spatial scales examined. Neither the herbivore nor natural enemies distributed themselves according to the predictions of the ideal free distribution and the herbivore did not oviposit to reduce natural enemy attack.

4. Extrapolating from the theoretical predictions of the ideal free distribution and enemy‐free space to the field requires considerable caution. Terellia ruficauda and its parasitoids appear to select their oviposition sites to spread the risk of losses through factors (e.g. mammal herbivory) that may damage dense clusters of C. palustre.
An adaptive benefit of facultative coprophagy in the German cockroach Blattella germanica
Authors: Kopanic Robert J. , Holbrook Glenn L. , Sevala Veeresh , Schal And Coby
Published: March 2003

1. A possible adaptive benefit of coprophagy was investigated in nymphs of the German cockroach Blattella germanica (L.).

2. Newly ecdysed first instars, given no source of food other than conspecific faeces, survived significantly longer than first instars deprived of faeces. The faeces of adult males and females may be of different quality, however, because nymphs given female faeces were more likely to moult into the second stadium than nymphs given male faeces.

3. In contrast to first instars, second instars provided adult faeces survived only slightly longer than starved counterparts. Faecal feeding is therefore stage‐specific, as is the benefit derived from it.

4. The relationship between the nutrient composition of faeces and the survival of nymphs was also examined. First instars fed the faeces of adults that had been maintained on a high (50%) protein diet, died more slowly than first instars fed the faeces of adults that had been maintained on medium (22.5%) and low (5%) protein diets. Chemical analysis of faeces showed that the concentration of protein in adult faeces increased with the level of protein in the diet. Moreover, food choice assays showed that first instars, unlike adults, ingested more of the high‐protein diets.

5. These data support the idea that coprophagy is a stage‐specific adaptive behaviour that permits first instars to moult into the second stadium with minimal foraging.
Habitat and weather affect reproduction and size of the dung beetleAphodius fossor
Authors: Vessby Karolina
Published: March 2003

1. The influence of sun exposure and moisture on reproduction and size of a north temperate dung beetleAphodius fossorwas investigated. Adult beetles were added to cow pats that were either shaded or exposed and treated with different watering regimes.

2. After 26 days, more eggs and larvae were recovered from shaded and wetter pats than from exposed and drier pats.

3. At the end of the experiment, more beetles had developed in shaded and wetter pats, and these beetles were larger than those from exposed and drier pats.

4. There was no between‐treatment difference in the ratio between adults in final sampling and larvae in first sampling.

5. It was concluded that exposure and moisture can influence both reproduction and size ofA. fossor. It is suggested that weather may be a factor regulating reproduction inAphodiusnot only through heat‐ or drought‐induced mortality, as suggested earlier, but also by limiting the time available for egg laying. Further studies are needed to clarify this suggestion.
Discrimination against previously searched, host‐free patches by a parasitoid foraging for concealed hosts
Authors: Hoffmeister T. S. , Gienapp P.
Published: March 2003

1. The foraging behaviour of the parasitoid wasp Halticoptera laevigata Thomson (Hymenoptera: Pteromalidae) was studied. This wasp attacks the first‐instar larvae of the fruit fly Myoleja lucida Fallén (Diptera: Tephritidae) within honeysuckle Lonicera xylosteum L. (Caprifoliaceae) fruits. It was hypothesised that, to forage efficiently, wasps should be able to maintain a systematic or at least non‐random search pattern on the level of the microhabitat, i.e. branches with fruits, and/or be able to recognise previously searched fruits.

2. Comparisons of observed patch visitation patterns on branches bearing uninfested fruits with expected values for systematic and random visitation patterns indicated that H. laevigata wasps visit patches randomly and do not avoid visiting host‐free patches that they have visited previously.

3. While wasps did not alter their search effort on uninfested fruits searched previously by conspecifics, they searched for much shorter times and probed less frequently for hosts on uninfested fruits that they had searched previously.

4. The results indicate that H. laevigata wasps engage in partially systematic search and increase their search efficiency through the recognition of self‐searched fruits. The reasons why partial rather than fully systematic search should be adaptive in this parasitoid are discussed.
Senescence of immune defence in Bombus workers
Authors: Doums Claudie , Moret Yannick , Benelli Elmar , Schmid‐Hempel Paul
Published: March 2003

Abstract 1. Senescence in workers of social insects is a particularly intriguing life‐history trait as the future fitness of workers relies primarily on age‐dependent survival rate. The pattern of senescence of immune defence traits was investigated under laboratory conditions in workers of two bumble bees: Bombus terrestris and B. lucorum.

2. In both species, there was a significant decrease with age in the ability to encapsulate a foreign object (a global measure of the efficiency of immune systems). This pattern of senescence was observed in all colonies in B. terrestris (seven) and B. lucorum (eight) assayed, even though, for the latter, there was some heterogeneity among colonies.

3. In B. terrestris, two other measures of immune defence were taken: the relative percentage of fat body in the abdomen and the concentration of haemocytes (the immune defence cells). The quantity of fat body increased only slightly with age and there was no effect for the concentration of haemocytes. Interestingly, the concentration of haemocytes decreased strongly after an encapsulation response, regardless of the age of workers.

4. The importance of the senescence pattern observed for the immune defence traits is discussed in the context of the social biology of workers.
Dung feeding in adult scarabaeines (tunnellers and endocoprids): even large dung beetles eat small particles
Authors: Holter P. , Scholtz C. H. , Wardhaugh K. G.
Published: March 2003

Abstract 1. The maximum size of ingested particles was determined in 15 species of adult dung beetle (Scarabaeidae: Scarabaeinae) by mixing small latex or glass balls of known diameter into the dung used as food. Twelve species (tribes Coprini, Onitini, Oniticellini, and Onthophagini) were tunnellers (making dung stores for feeding and breeding in the soil below the pat) and three species (tribe Oniticellini) were endocoprids (feeding and breeding in the dung pat itself).

2. The test species, covering a wide range of body size (fresh weights 0.05–7.4 g), ingested minute particles only (maximum diameter 8–50 µm), and there was a statistically significant but numerically small increase in particle size with body weight.

3. When the effect of body size was taken into account, taxon (tribe), ecological group (tunneller/endocoprid), and dung preference (coarse/fine) had no significant effect on the size of ingested particles.

4. Tests using two tunnelling species did not indicate that beetles use their mandibles to grind dung particles prior to ingestion.

5. The results suggest essentially the same feeding mechanism in all adult tunnelling or endocoprid scarabaeines that eat fresh dung. Larger, indigestible plant fragments are avoided by filtration, and ingestion is confined to very small particles of higher nutritional value.
Patterns of pollen feeding and habitat preference among Heliconius species
Authors: Estrada Catalina , Jiggins Chris D.
Published: March 2003

Abstract 1. The ecological circumstances that precipitate speciation remain poorly understood. Here, a community of Heliconius butterflies in lowland Panama was studied to investigate patterns of pollen use, and more specifically the ecological changes associated with the recent divergence of Heliconius melpomene (Linnaeus) and H. cydno (Doubleday).

2. Considering the seven commonest Heliconius species in the community, 32 types of pollen or spore were encountered in pollen loads but only five pollen species were common. Systematic exploitation of pollen was therefore confined to a small proportion of the flowers visited.

3. Most of the variation in pollen load composition between individuals was explained by differences in collecting locality. The exception was Psiguria, which was used in all habitats by the melpomene/hecale clade far more than by the erato/sapho clade. This may suggest an ancestral switch within Heliconius towards increased reliance on Psiguria pollen.

4. Heliconius cydno and H. melpomene differed significantly in pollen load composition for three of the five most commonly collected pollen species. This is most probably explained by differences in habitat preference; H. melpomene and its co‐mimic H. erato are found in open habitat while H. cydno and its co‐mimic H. sapho are found in closed‐canopy forest.

5. As melpomene and cydno are known to hybridise occasionally, such differences in adult microhabitat contribute to pre‐mating isolation. Habitat divergence between H. cydno and H. melpomene, which is associated with changes in mimicry, must have played a role in their recent speciation.
Dynamics of springtail and mite populations: the role of density dependence, predation, and weather
Authors: Ferguson Steven H. , Joly Damien O.
Published: March 2003

Abstract1. Ecological theory suggests that density‐dependent regulation of organism abundance will vary from exogenous to endogenous factors depending on trophic structure. Changes in abundance of soil arthropods were investigated at three trophic levels, springtails (Collembola), predaceous mites (Acari), and macro‐arthropods (spider, adult and larval beetles, centipedes). Predictions were that springtails are predator regulated and mites are food limited according to the Hairstonet al. (1960) model, which predicts alternating regulation by competition and predation from fungi to springtails to mites to macro‐arthropods. The alternate hypothesis was based on the bottom‐up model of trophic dynamics, which predicts that each trophic level is regulated by competition for resources.

2. The relative contributions to springtail and mite population dynamics of endogenous (i.e. density‐dependent population growth related to food availability) and exogenous (i.e. predation and weather) factors were tested using time‐series analysis and experimental manipulation of water conditions. Box patterns were distributed within an aspen forest habitat located in the Canadian prairies and surveyed weekly from May to September 1997–1999. Each box depressed the leaf litter, creating a microhabitat island for soil arthropods that provided counts of invertebrates located immediately beneath the boxes.

3. Strong evidence was found for endogenous control of springtail and mite numbers, indicated by a reduction in population growth related to density in the previous week. Contrary to predictions, no evidence was found for regulation of springtail numbers by mites, or for regulation of mite numbers by macro‐arthropods. Springtail population growth rate was related positively to current springtail density (8 and 23% variation explained) and related negatively to 1‐week lagged density (85 and 58%), and related negatively to temperature (5 and 5%) for time‐series data and for experimental addition of water respectively. Mite population growth rate was related positively to current mite density (54%) and temperature (4%), and negatively to 1‐week lagged mite density (20%) and precipitation (6%) for time‐series analysis. For experimental addition of water, mite growth rate was related positively to current mite density (44%) and temperature (5%), and negatively to 1‐week lagged density (11%). Results differed from the Hairstonet al. (1960) model predictions but were consistent with a bottom‐up view that springtail and mite populations were regulated intrinsically by competition for food and secondarily by temperature as a function of reproduction.
Allee effect in larval resource exploitation in Drosophila: an interaction among density of adults, larvae, and micro‐organisms
Authors: Wertheim Bregje , Marchais Julien , Vet Louise E. M , Dicke Marcel
Published: March 2003

Abstract 1. Aggregation pheromones can evolve when individuals benefit from clustering. Such a situation can arise with an Allee effect, i.e. a positive relationship between individual fitness and density of conspecifics. Aggregation pheromone in Drosophila induces aggregated oviposition. The aim of the work reported here was to identify an Allee effect in the larval resource exploitation by Drosophila melanogaster, which could explain the evolution of aggregation pheromone in this species.

2. It is hypothesised that an Allee effect in D. melanogaster larvae arises from an increased efficiency of a group of larvae to temper fungal growth on their feeding substrate. To test this hypothesis, standard apple substrates were infested with specified numbers of larvae, and their survival and development were monitored. A potential beneficial effect of the presence of adult flies was also investigated by incubating a varying number of adults on the substrate before introducing the larvae. Adults inoculate substrates with yeast, on which the larvae feed.

3. Fungal growth was related negatively to larval survival and the size of the emerging flies. Although the fungal growth on the substrate was largely reduced at increased larval densities, the measurements of fitness components indicated no Allee effect between larval densities and larval fitness, but rather indicated larval competition.

4. In contrast, increased adult densities on the substrates prior to larval development yielded higher survival of the larvae, larger emerging flies, and also reduced fungal growth on the substrates. Hence, adults enhanced the quality of the larval substrate and significant benefits of aggregated oviposition in fruit flies were shown. Experiments with synthetic pheromone indicated that the aggregation pheromone itself did not contribute directly to the quality of the larval resource.

5. The interaction among adults, micro‐organisms, and larval growth is discussed in relation to the consequences for total fitness.
Do leaf shelters always protect caterpillars from invertebrate predators?
Authors: Jones Meg T. , Castellanos Ignacio , Weiss Martha R.
Published: March 2003

Abstract 1. All larval instars of Epargyreus clarus, the silver‐spotted skipper, construct and inhabit leaf shelters that are presumed to protect them from predator attack.

2. Shelters effectively protected the larvae against foraging Crematogaster opuntiae ants and naive Polistes spp. wasps in laboratory tests, but did not protect them from predators, largely vespid wasps, present in the field.

3. A range of factors, including type of predator, learning ability, and experience level, may determine the effectiveness of leaf shelters as protection from predators.
Ontogenetic shifts in competitive interactions and intra‐guild predation between two wolf spider species
Authors: Balfour Robert A. , Buddle Christopher M. , Rypstra Ann L. , Walker Sean E. , Marshall Samuel D.
Published: March 2003

Abstract.1. The wolf spiders (Araneae: Lycosidae)Hogna helluo(Walckenaer) andPardosa milvinaHentz co‐occur in soybean fields of south‐west Ohio, U.S.A. As adults,Hognais the larger species and has the competitive advantage in most interactions; due to differing phenologies, however, their size‐classes frequently overlap and as such there is potential for shifts in competitive ability and intra‐guild predation. The hypothesis that competitive interactions and intra‐guild predation will favourPardosawhenPardosais similar‐sized, or has a size advantage overHogna, was tested in laboratory and field experiments.

2. Studies in laboratory arenas, pairing similar‐sized individuals of these species andHognaspiderlings with larger spiders of both species, revealed that intra‐guild predation seldom occurs with similar‐sizedHognaandPardosa, howeverPardosawill consume smallHognaindividuals in laboratory arenas.

3. Field experiments involved stocking high densities (50 m–2) ofPardosaandHognain enclosures placed in soybean fields. In experiments with spiders of similar size, no interspecific effects were uncovered, but an intraspecific effect was found forPardosaas its survival and weight gain were lower in the presence of more conspecifics. LargeHognaorPardosahad no effect on the survival or weight gain ofHognaspiderlings.

4. AlthoughHognais a better competitor as an adult, it has no advantage overPardosawhen their size‐classes overlap, andPardosaeffects onHognamay be inconsequential under field conditions. Therefore, the co‐existence of these species is fostered by the fact that there are few negative interspecific interactions during their ontogeny.
Competition as a factor underlying the abundance of an uncommon phytophagous insect, the salt‐marsh planthopper Delphacodes penedetecta
Authors: Ferrenberg Scott M. , Denno Robert F.
Published: March 2003

Abstract. 1. Recent reviews of experimental studies provide compelling evidence that competition should be retained as a potential factor influencing the success of phytophagous insects. In this context, the objective of the study was to determine the role of interspecific and intraspecific competition, both contemporaneous and plant mediated (feeding‐induced resistance), in limiting the population density of a consistently rare insect in a guild of abundant potential competitors.

2. Competitive interactions were assessed experimentally between two phloem‐feeding planthoppers, the abundant Prokelisia dolus and the rare Delphacodes penedetecta (Hemiptera: Delphacidae). Both species are monophagous on the cordgrass Spartina alterniflora and overlap broadly in their use of habitats in the intertidal salt marshes along the Atlantic coast of North America.

3. The two planthoppers partition their cordgrass host plant, with D. penedetecta feeding more on the basal stems (particularly females) and P. dolus occurring most often on the canopy leaves. Notably, there was no evidence for niche shifting in D. penedetecta because its distribution on the plant did not change in the presence or absence of P. dolus.

4. Interspecific interactions with P. dolus had very little effect on the performance (development time and body size) and survival of D. penedetecta, a result demonstrated in both the laboratory and field. This result occurred both in contemporaneous interactions and on plants fed on previously by P. dolus. Only the males of D. penedetecta experienced weak competitive effects from P. dolus, as evidenced by reduced body size and slightly protracted development.

5. By contrast, there were strong adverse effects of intraspecific crowding (both from contemporaneous interactions and on plants fed on previously by conspecifics), whereby the survival, development time, and body size of D. penedetecta were affected very adversely.

6. These results suggest that interspecific competition is a weak force influencing the abundance of D. penedetecta in the field. Rather, strong intraspecific competition, a high requirement for plant nitrogen, and intrinsically low lifetime fecundity combine to explain the rarity of D. penedetecta.
Cytokine autoantibodies in multiple sclerosis, aseptic meningitis and stroke
Authors: Elkarim  , Mustafa  , Kivisäkk  , Link  , Bakhiet
Published: March 2003

Background

We have recently described the induction of anti‐cytokine autoantibodies during bacterial infections and autoimmune diseases as a mechanism for cytokine regulation.

Methods

Herein, we study the occurrence of autoantibodies to pro‐ and anti‐inflammatory cytokines in cerebrospinal fluid and plasma from patients with multiple sclerosis, aseptic meningitis and stroke.

Results

Increased levels of autoantibodies to interferon γ, tumour necrosis factor α, interleukin 4 and interleukin 10 were detected in both compartments of multiple sclerosis and aseptic meningitis patients. Interestingly, in cerebrospinal fluid from stroke patients, only autoantibodies to interleukin 4 and interleukin 10, but not interferon α or tumour necrosis factor α were detected. No significant autoantibody levels were registered in plasma from stroke patients against all four cytokines compared with healthy control subjects. The latter revealed very low autoantibody levels in plasma and no detectable autoantibodies in cerebrospinal fluid.

Conclusions

Our data show for the first time the occurrence of cytokine autoantibodies in these diseases, but their biological significance is unclear.
Angiotensin‐converting enzyme gene polymorphism is not associated with coronary atherosclerosis and myocardial infarction in a sample of Italian patients
Authors: Arca  , Pannitteri  , Campagna  , Candeloro  , Montali  , Cantini  , Seccareccia  , Campa  , Marino  , Ricci
Published: March 2003

Background

The deletion (D) allele of the angiotensin‐converting enzyme (ACE) gene has been proposed as a genetic marker of the risk of ischaemic heart disease. However, the relationships between ACE genotypes, the development of coronary atherosclerosis and the occurrence of major coronary events are still controversial.

Methods

To investigate whether the ACE I/D (insertion/deletion) polymorphism predicts the risk of coronary stenosis and myocardial infarction (MI), ACE genotypes were determined in 394 consecutive patients who underwent coronary angiography. The presence of coronary artery disease (CAD) (defined by > 50% stenosis) was detected in 236 patients (CAD+); 85 of these individuals had a history of MI. Patients with coronary stenosis < 10% (n = 158) served as controls (CAD−). ACE genotypes were determined by agarose gel sizing after polymerase chain reaction (PCR) amplification.

Results

The distribution of ACE genotypes in CAD+ patients was not significantly different from that in CAD− patients (χ2 = 2.63, P < 0.27). After controlling for other coronary risk factors, no significant increase in risk of CAD or MI was found to be associated with the D allele, regardless of whether the D allele was assumed to have a dominant, a co‐dominant or a recessive effect. Similar results were observed in CAD+ patients at lower risk because of low body mass index and apolipoprotein B concentrations. Smoking, apolipoprotein B and history of hypertension were found to be independent predictors of CAD and MI.

Conclusion

Our study did not provide evidence of a significant association between ACE genotypes and the development of coronary atherosclerosis. It also failed to support a role of ACE I/D polymorphism in favouring the conversion of coronary stenosis to MI.
The effect of smoking on post‐heparin lipoprotein and hepatic lipase, cholesteryl ester transfer protein and lecithin:cholesterol acyl transferase activities in human plasma
Authors: Freeman  , Caslake  , Griffin  , Hinnie  , Tan  , Watson  , Packard  , Shepherd
Published: March 2003

Introduction

Smoking is associated with dyslipidaemia, particularly raised plasma triglycerides and reduced high‐density lipoprotein (HDL)‐cholesterol and a delayed clearance of triglyceride in fat tolerance tests. The aim of this study was to investigate whether these phenomena could be explained by a reduced lipoprotein lipase activity in smokers.

Methods

A group of 40 healthy individuals [plasma cholesterol 5.07 (SD 0.90) mmol L−1, plasma triglyceride 1.02 (SD 0.39) mmol L−1)] was studied to examine the effects of smoking on plasma enzyme activities, particularly post‐heparin lipase activities. The group comprised 20 smokers and 20 non‐smokers, who were matched for age, gender and body mass index (BMI).

Results

Post‐heparin lipoprotein lipase (LPL) activity [3.89 (SD 1.58) vs. 5.85 (SD 2.30) μmol free fatty acids (FFA) mL−1 h−1, P < 0.005], but not post‐heparin hepatic lipase (HL) activity, was reduced in smokers. Plasma cholesteryl ester transfer protein (CETP) activity and lecithin:cholesterol acyl transferase (LCAT) activity were measured in a subgroup of 18 individuals, comprising nine smokers with nine matched non‐smokers. There was no difference in CETP activities between the two groups, but smokers had a significantly reduced plasma LCAT activity [112 (SD 23) vs. 152 (SD 24) nmol cholesterol mL−1 h−1, P < 0.005]. In both smokers (r = –0.53, P < 0.05) and non‐smokers (r = –0.54, P < 0.05), HDL2 concentration was negatively associated with HL activity. In non‐smokers, HDL3 concentration was negatively associated with CETP activity (r = –0.77, P < 0.05), whereas in smokers HDL3 concentration was negatively associated with LCAT activity (r = –0.78, P < 0.050).

Conclusion

It was shown by direct measurement that the activity of plasma post‐heparin LPL is reduced in smokers, independently of age, gender and BMI. It is concluded that this enzyme perturbation associated with smoking may contribute to the development of the atherogenic lipoprotein phenotype seen in smokers.
Parathyroid hormone and ionized calcium levels are related to the severity of illness and survival in critically ill patients
Authors: Carlstedt  , Lind  , Rastad  , Stjernström  , Wide  , Ljunghall
Published: March 2003

Background

The present study explores serum parathyroid hormone (PTH) and blood ionized calcium (Ca2+) levels in relation to the severity of disease and mortality in the intensive care unit (ICU).

Methods

In a pilot study, 37 consecutive critically ill patients admitted to the ICU were studied with determinations of serum PTH and total serum calcium within the first 24 h. In a following prospective study, patients suffering from sepsis (n = 13) or subjected to major surgery (n = 13) were investigated daily for 1 week with determinations of serum PTH and ionized calcium (Ca2+). Severity of disease was assessed by the APACHE II score and hospital mortality was recorded.

Results

In the pilot study, serum PTH levels were elevated (> 55 ng L−1) in 38% of the patients and were not related to serum calcium but showed a significant relationship to the APACHE II score (r = 0.39, P < 0.05). In the prospective study, serum PTH was elevated in 69% of the patients in both groups at inclusion, and 6 days later 87% of the septic and 37% of the surgery patients still showed elevated levels. Hypocalcaemia was more commonly seen in the septic patients [mean Ca2+ 1.03 ± 0.08 (SD) mmol L−1] than in the surgical patients (1.14 ± 0.06 mmol L−1) at inclusion. Both PTH and Ca2+ levels were significantly related to the APACHE II score (r = 0.46, P < 0.03, and r = –0.54, P < 0.009, respectively). Furthermore, PTH levels were significantly increased in non‐survivors (n = 5) compared with survivors (mean 161 ± 51 vs. 79 ± 51 ng L−1, P < 0.005).

Conclusion

Hypocalcaemia and increased levels of PTH were common findings in critically ill patients. These alterations in calcium homeostasis were related to the severity of disease and increased PTH levels were associated with a poor outcome.
Purine metabolism in female heterozygotes for hypoxanthine–guanine phosphoribosyltransferase deficiency
Authors: Puig  , Mateos  , Torres  , Buño
Published: March 2003

Background

Female carriers of the X‐linked recessive disorder hypoxanthine–guanine phosphoribosyltransferase (HPRT) deficiency show somatic cell mosaicism, and this may cause an increased synthesis of purines. We have examined whether urinary oxypurines could be useful for carrier diagnosis.

Methods

Carrier testing was performed in 35 women belonging to 16 unrelated Spanish families with at least one subject affected by the Lesch–Nyhan syndrome (11 families, 14 patients) or the Kelley–Seegmiller syndrome (five families, six patients) by means of HPRT and adenine phosphoribosyltransferase activities in hair follicles and/or molecular studies. Plasma and 24‐h urinary concentrations of hypoxanthine, xanthine and uric acid were measured while subjects were on a purine‐restricted diet.

Results

Mean plasma urate concentrations and 24‐h urinary hypoxanthine, xanthine and uric acid excretion rates were significantly higher in 22 heterozygotes than in 13 non‐carriers (P < 0.02). Daily urinary oxypurine excretion rates were also significantly higher in heterozygotes than in 12 normal women (P = 0.0011). Cumulative 5‐day radioactivity excretion after [8‐14C]‐adenine infusion was markedly increased in 10 carrier women compared with five normal women (P = 0.0369). The sensitivity of 24‐h urinary hypoxanthine and xanthine excretion rates was 86% and 77%, respectively, and the specificity 100% for both tests.

Conclusion

Female heterozygotes for HPRT deficiency show an enhanced purine nucleotide degradation and purine overproduction. An elevated hypoxanthine and/or xanthine excretion rate differentiated most heterozygotes for HPRT deficiency from non‐carrier women and thus could be useful for carrier diagnosis.
Direct in vivo gene transfer to healing rat patellar ligament by intra‐arterial delivery of haemagglutinating virus of Japan liposomes
Authors: Özkan  , Shino  , Nakamura  , Natsu‐ume  , Matsumoto  , Horibe  , Tomita  , Kaneda  , Ochi
Published: March 2003

Background

Manipulation of ligament healing has been a major focus of orthopaedic research. In recent years, gene transfer to healing ligament appears to be a feasible method for manipulating the healing process. In this study, we investigated the feasibility of gene transfer to healing rat patellar ligament by intra‐arterial delivery.

Methods

An attempt was made to transfer a reporter gene (Escherichia coli, β‐galactosidase gene) to healing rat patellar ligament using the haemagglutinating virus of Japan (HVJ) liposome‐mediated gene transfer method. Three days after cutting the patellar tendons of 25 14‐week‐old male Wistar rats, HVJ–liposome complexes containing β‐galactosidase (β‐gal) cDNA were injected into the femoral artery of 15 Wistar rats as the experimental group. HVJ liposomes without DNA were injected into the femoral artery of 10 Wistar rats as the control group. Three rats from the experimental group and two control rats were killed 3, 7, 14, 28 and 56 days after the injection.

Results

After X‐gal staining, the rate of transfection in the experimental group (mean ±  SEM) was found to be 12.1% ± 0.590%, 8.7% ± 0.217%, 10.2% ± 0.227%, 3.2% ± 0.247% and 0.7% ± 0.060% at post‐injection days 3, 7, 14, 28 and 56 respectively. In control sections the number of blue‐stained cells were very few at any point.

Conclusion

We succeeded in introducing a reporter gene into healing rat patellar ligament by intra‐arterial delivery of HVJ–liposome complexes. This method appears to have the potential to be applicable for soft‐tissue healing studies and also healing studies of other tissues and organs.
Zymogen granule alterations in caerulein‐induced pancreatitis developed during continuous hydrocortisone administration
Authors: García‐Montero A. C. , Manso M. A. , Orfao A. , Vicente S. , De Dios I.
Published: March 2003

Background

The amount of enzymes stored in individual zymogen granules and the glycosylation of their membrane have been analysed in rats with acute pancreatitis induced by caerulein after hydrocortisone treatment. The consequences of prolonging hydrocortisone administration after pancreatitis and the use of the cholecystokinin (CCK) receptor antagonist, L‐364,718, have also been evaluated.

Materials and methods

Analysis was performed using flow cytometry.

Results

Caerulein‐induced pancreatitis in rats previously treated for 7 days with hydrocortisone (10 mg kg−1 per day) revealed alterations in enzyme storage in the pancreas. Significant increases in amylase and trypsinogen contents in zymogen granules were observed, an effect associated with a reduction in l‐fucose glycoconjugates. Pancreatitis persists 7 days later if hydrocortisone treatment is prolonged. At this stage, a reduced granule fucosylation was still observed, and a significant decrease in the amount of trypsinogen stored in the granules was found. However, hydrocortisone administration led to an increase in intragranular amylase quantities up to normal values, even when L‐364,718 was simultaneously administered, but it reverted to plasma as a consequence of pancreatitis. The amount of N‐acetyl d‐glucosamine in the zymogen granule membrane was not altered by caerulein acute pancreatitis induced under continuous hydrocortisone treatment, but it was decreased by the administration of L‐364,718 over 7 days after pancreatitis induction.

Conclusions

The administration of hydrocortisone after the development of pancreatitis prevented recurrence of the disease. L‐364,718 proved to be detrimental, not only failing to reduce the symptoms of pancreatitis but also altering the glycoproteins of zymogen granule membrane.
α2‐Macroglobulin reduces paracrine‐ and autocrine‐stimulated matrix synthesis of cultured rat hepatic stellate cells
Authors: Schüftan G. G. , Bachem M. G.
Published: March 2003

Background

Transforming growth factor β1 (TGF‐β1) is considered to represent a major fibrogenic mediator in the liver. The aim of the present study was to investigate whether α2‐macroglobulin (α2M) might reduce paracrine‐ and autocrine‐stimulated matrix synthesis of cultured rat hepatic stellate cells (HSCs) by scavenging TGF‐β.

Methods and results

Using native agarose electrophoresis, we demonstrated that α2M binds [125I]‐TGF‐β1 within minutes. Preincubation of transiently acidified supernatants of cultured Kupffer cells, secondary cultured (activated) HSC and platelet lysate with, respectively, 500 and 2000 μg mL−1α2M significantly reduced the concentration of active TGF‐β1 in these media. As a consequence of TGF‐β scavenging by α2M, paracrine‐stimulated proteoglycan synthesis of primary cultured HSCs was reduced significantly. Furthermore, addition of 200 μg mL−1α2M to passaged (activated) HSCs resulted in (a) a reduction in autocrine‐stimulated extracellular matrix synthesis (proteoglycan −52%, fibronectin −55%) and (b) increased cell proliferation. A similar reduction in matrix synthesis was observed after the addition of 5 μmol L−1 TGF‐β1 antisense oligonucleotide to activated HSCs.

Conclusion

We conclude that α2M reduces paracrine‐and autocrine‐stimulated extracellular matrix synthesis of cultured HSCs by scavenging TGF‐β. These mechanisms might restrict liver fibrogenesis.