bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical anisotropy of a pig tendon under compression*
Authors: Feitosa Vera Lúcia C. , Vidal Benedicto C. , Pimentel Edson R.
Published: March 2003

The proximal region of the superficial digital flexor tendon of pigs passes under the tibiotarsal joint, where it is subjected to compressional and tensional forces. This region was divided into a surface portion (sp), which is in direct contact with the bone and into a deep portion (dp), which is the layer opposite the articulating surface. The purpose of this work was to analyse the distribution and organisation of the collagen bundles and proteoglycans in the extracellular matrix in sp and dp. Toluidine‐blue‐stained sections were analysed under a polarising microscope. Strong basophilia and metachromasia were observed in sp, demonstrating accumulation of proteoglycan in a region bearing compression, but the intensity was reduced the further layers were from the bone. Linear dichroism confirmed that the glycosaminoglycan molecules were disposed predominantly parallel to the longest axis of the collagen fibrils. Birefringence analysis showed a higher molecular order and aggregation of the collagen bundles in areas where the tension was more prominent. The crimp pattern was more regular in dp than in sp, probably as a requirement for tendon stretching. The optical anisotropy exhibited by the collagen bundles also confirmed the helical organisation of the collagen bundles in the tendon. Hyaluronidase digestion caused a decrease in the basophilia, but this was not eliminated, supporting the idea that in the matrix, proteoglycans are not completely available to the enzyme action.
Development of the lung of the brushtail possum, Trichosurus vulpecula
Authors: Cooke Michèle M. , Alley Maurice R.
Published: March 2003

The developing lung of the brushtail possum, Trichosurus vulpecula, was studied by light microscopy, and transmission electron microscopy was used to study the morphology of the conducting airways in the adult. Bronchi did not extend beyond the hilus of each of the six lobes of the lung, and lobules were supplied by major bronchioles. By 105 days post partum, bronchi and bronchioles were fully formed, coinciding with the emergence of mucosal associated lymphoid tissue (MALT), which preceded alveolar maturation by approximately 20 days. In the adult lung, goblet cells were rarely observed in the mucosal epithelium of bronchi, whereas Clara cells were present in the mucosa of all airways, increasing proportionately as the conducting and respiratory portions narrowed distally. Although the airways of the possum lung have a poorly developed mucociliary blanket, this may be compensated for by the large numbers of Clara cells and adequate supply of MALT.
The conus arteriosus of the adult gilthead seabream (Sparus auratus)
Authors: Schib J. L. , Icardo J. M. , Durán A. C. , Guerrero A. , López D. , Colvee E. , De Andrés A. V. , Sans‐Coma V.
Published: March 2003

This paper reports on the presence of the conus arteriosus in the heart of the adult gilthead seabream, Sparus auratus (Perciformes, Teleostei). The junctional region between the single ventricle and the bulbus arteriosus has been studied by conventional light microscopy, and by scanning and transmission electron microscopy. In addition, fluorescent phalloidin and antibodies against the muscle myosin heavy chains, laminin and collagen type IV have been used. The conus arteriosus is a distinct muscular segment interposed between the ventricle and the bulbus arteriosus. It is clearly different from the bulbus arteriosus due to its myocardial nature. It can also be distinguished from the ventricular myocardium because: (1) it has a conus shape; (2) it is formed by compact, well‐vascularized myocardium; (3) it is surrounded on its inner and outer faces by fibrous layers rich in collagen and elastin; (4) it constitutes the anatomical support of the so‐termed conus valves; (5) it shows intense staining for laminin and type‐IV collagen; and (6) the myocardial cells located close to the inner fibrous layer are helicoidally arranged. By contrast, the ventricular myocardium is highly trabecular, lacks a compacta, shows no vessels, and presents barely detectable amounts of laminin and collagen type IV. The presence of a distinct conus arteriosus in the heart of an evolutionary advanced teleost species indicates that the conus is not a vestigial segment from the evolutionary or embryological points of view. The characteristic spatial arrangement of the conus myocytes strongly suggests that the conus is implicated in the mechanical performance of the conus valves.
Butterfly responses to habitat edges in the highly fragmented prairies of Central Iowa
Authors: Ries Leslie , Debinski Diane M.
Published: March 2003

The behaviour of two butterfly species, a habitat specialist (Speyeria idalia) and a habitat generalist (Danaus plexippus), was tracked at four prairie edges to determine the extent to which edges act as a barrier to emigration. The four edge types studied were crop, road, field and treeline. The edges differed in structure ranging from high‐contrast (treeline) to low‐contrast (field).

S. idalia, the habitat specialist, responded strongly to all edges, even those with low structural contrast. However, S. idalia’s response was strongly affected by conspecific density at crop and field edges; individuals were less likely to exit from high density plots. S. idalia responded to edges both by turning to avoid crossing them, and returning to the plot if they had crossed.

D. plexippus responded strongly only to treeline edges. Wind direction and time of year were important factors influencing behaviour at edges for this species. Conspecific density was not a significant factor affecting their behaviour. D. plexippus responded to edges by not crossing them, but rarely returned once they had crossed.

In highly fragmented landscapes, such as the one in which this study occurred, butterflies which show little or no response to edges may exhibit high emigration rates because of the high probability of encountering an edge in small habitat patches. Butterflies may respond strongly to even subtle habitat boundaries, but those responses may be modified by the edge structure, local environment or other conditions. Therefore, modifying edge structure may be a way to influence emigration rates, making it a useful tool for conservation.
Environmental forcing and high amplitude fluctuations in the population dynamics of the tropical butterfly Acraea acerata (Lepidoptera: Nymphalidae)
Authors: Azerefegne Ferdu , Solbreck Christer , Ives Anthony R.
Published: March 2003

The population dynamics of the sweet potato butterfly, Acraea acerata, were studied for 3 years in sweet potato fields in southern Ethiopia in an area where farmers practice successive plantings throughout the year and do not use pesticides. Densities of eggs, young and old larvae, pupae and adults were estimated for 18 or more generations.

The insect breeds during all seasons with about six generation cycles per year. Superimposed on the generation cycles are longer‐term intergeneration fluctuations with amplitudes of three to four orders of magnitude. Population decline and build‐up are gradual processes taking place over several generations.

We used time‐series techniques to analyse the patterns of density‐dependent stage‐specific survival and reproduction, and the influence of enemies and weather fluctuations on A. acerata intergeneration dynamics. These techniques allow statistically valid inference about insect demography.

The analyses revealed strong density‐dependent effects on recruitment, due possibly to the combined effects of reductions in adult female size and density‐dependent emigration.

Weather conditions affected dynamics in two opposing ways. Rainy conditions increased recruitment. In contrast, heavy rains decreased the survival of young larvae and pupae, while very dry conditions also decreased their survival, leading to a non‐linear effect of rainfall on survival of immature stages.

Enemies appeared to have little effect on the population dynamics of A. acerata.

The net consequences of the sensitivity of A. acerata to seasonal fluctuations in rainfall are high‐amplitude multigeneration fluctuations in abundance. This case study demonstrates that high‐amplitude fluctuations in abundance may be driven by weather, rather than by predator–prey interactions.
Movements and foraging areas of naïve, recently weaned southern elephant seal pups
Authors: McConnell Bernie , Fedak Mike. , Burton Harry R. , Engelhard G. H. , Reijnders Peter J. H.
Published: March 2003

Female southern elephant seals (Mirounga leoninaL.) expend variable, often large, amounts of their stored body resources on their pups during lactation. There is some evidence that pups with higher weaning masses have a better chance of surviving their first year. But in order to understand what level of maternal investment is required to produce successful pups, we need to understand the behaviour and problems faced by naïve pups before nutritional independence.

 We used satellite telemetry to track 30 newly weaned pups on their first trip to sea from their natal site at Macquarie Island in 1995 and 1996. Track duration varied from 2 to 179 (mean, 77) days. Seven seals were tracked for the entire duration of their first trip.

 The movements were grouped into three phases. Phase 1 (mean duration 30 days) was characterized by rapid and directed dispersal from Macquarie Island at daily travel rates of up to 140 km day−1. Phase 2 (mean duration 67 days) consisted of slower travel rates (generally < 20 km day−1) where activity was often centred on localized patches up to 1900 km from Macquarie Island. This phase was sometimes interrupted by bouts of increased travel rate as the seal moved to another patch. Phase 3 (mean duration 42 days) consisted of prolonged increased travel rates as the seals returned to Macquarie or, in one case, Chatham Island.

 The routes of the tracks to the south‐east were very similar. Simulated tracks based on a constant heading of magnetic east, at variable swimming speed, and modified by ocean current vectors produced a pattern similar to, but not identical to, the south‐east tracks. The tracks to the west and south were more diverse and meandering.

 Based on a nearest neighbour analysis, neither sex, year nor weaning mass influenced Phase 1–2 or Phase 2–3 transition locations.

 Phase 2 tracks were associated in the south‐eastern group with the Pacific Antarctic Ridge and in the south‐west group, to a lesser extent, with the Indian Antarctic Ridge. The southern limits of Phase 2 tracks in the south‐eastern group aligned with the southern Antarctic Circumpolar Circulation front.

 Using calculated estimates of body composition at weaning and estimates of the rate of utilization of body reserves for the period before animals reach phase 2 of their trip, we estimate that large pups will have reserves remaining to supply their needs whereas pups in the small group are approaching critical limits. However, these estimates are based on several assumptions and extrapolations. More information on body composition of pups at weaning and departure is needed along with behavioural information to clarify the value of maternal expenditure in terms of offspring survival.
Effects of habitat fragmentation on pollination: pollinators, pollinia viability and reproductive success
Authors: Murren Courtney J.
Published: March 2003

For 3 years, I examined the effects of fragmentation on pollination of an endemic, euglossine bee‐pollinated, epiphytic orchid,Catasetum viridiflavum, on 10 islands created during the construction of the Panamá Canal and at five sites in nearby large tracts of mainland forest.

I investigated the viability of pollinia over time, availability of pollinators and male and female reproductive success (measured as removal of pollinaria and fruit set, respectively) at different sites.

Viability of pollinia declined dramatically over time, although some remained at least partially viable for up to 60 days. Bees moved between trapping stations at different sites within a day, and viable pollen therefore could have been transferred between populations.

Although euglossine bees were equally frequent in fragments and continuous forest, those recorded on islands were visitors from mainland sites, and not island residents.

Neither male nor female reproductive success were significantly different between island and mainland forest types in 1997. The higher reproductive success in certain sites within both forest types throughout the flowering season could not be explained by variation in overall population floral display. Larger inflorescences had higher male and female reproductive success.

In 2 of 3 years, plants on islands had significantly lower fruit set than plants on mainland sites. Female reproductive success differed dramatically across years and sites.

The low fruit set in 1996 and 1998 on islands in comparison with mainlands, and the observation that bees are not island residents, conform with expectations of physical isolation of forest patches. In spite of the evidence of fragmentation in this system, patterns of pollinator behaviour and of reproductive success suggest significant connectedness among sites. This 3‐year study shows that a single year study may not have highlighted the complexity of the system.
The rust pathogen Triphragmium ulmariae as a selective force affecting its host, Filipendula ulmaria
Authors: Ericson L. , Burdon J. J. , Müller W. J.
Published: March 2003

The rust fungus Triphragmium ulmariae had a substantial effect on the survival of seedlings of Filipendula ulmaria with 89% dying over a 5‐year period. Throughout the experiment, plants that survived the entire study period consistently showed very low disease severity when compared to that suffered by plants that died during its course.

The resistance of F. ulmaria to T. ulmariae was assessed through inoculation of progeny of six geographically separated populations of F. ulmariae with four bulk populations of T. ulmariae. Significant differences in resistance as expressed by differences in pathogen prevalence and severity were detected among the F. ulmaria populations. Within individual host populations, significant differences were also detected among open‐pollinated family lines.

Although in some instances the susceptibility of host populations was greatest towards the pathogen collected from the same site, there was no consistent evidence for local adaptation.

An unplanned infection by Septoria ulmariae allowed assessment of resistance within F. ulmaria towards a single population of this pathogen. Again variation for resistance was detected among host populations and among family lines within some of the populations.
Consequences of positive ions upon imaging in low vacuum scanning electron microscopy
Authors: Craven J. P. , Baker F. S. , Thiel B. L. , Donald A. M.
Published: March 2003

The effects caused by an excess quantity of ionized gas molecules within the low vacuum, variable pressure and environmental scanning electron microscope (ESEM) are described with reference to mechanisms by which they can influence imaging conditions. These effects can include specimen charging, recombination and development of space charge. They are demonstrated for three different classes of sample: (1) an electrically grounded conductor, (2) an electrically floating conductor, and (3) an electrical insulator. A new device is presented that will aid excess charge removal within the ESEM and help correct for some of these effects, thereby dramatically improving imaging over a wide range of operating conditions and samples. The mechanism of image enhancement is demonstrated with reference to the three classes of sample described above.
A novel sample holder allowing atomic force microscopy on transmission electron microscopy specimen grids: repetitive, direct correlation between AFM and TEM images
Authors: Lin A. C. , Goh M. C.
Published: March 2003

A novel sample holder that allows atomic force microscopy (AFM) to be performed on transmission electron microscope (TEM) grids is described. Consequently, AFM and TEM images were repeatedly obtained on exactly the same sample area. For both techniques, a thin carbon film was used as the imaging substrate. Although these techniques have been previously used in conjunction, AFM and TEM images on exactly the same area have not been repeatedly obtained for any system. Correlation of AFM and TEM images is useful for work where the three‐dimensional topographical information provided by the AFM could be used to better interpret the two‐dimensional images provided by the TEM and vice versa. To demonstrate the applicability of such correlation, new results pertaining to a fibrillar collagen system are summarized.
Intraplantar injection of glutamate evokes peripheral adenosine release in the rat hind paw: involvement of peripheral ionotropic glutamate receptors and capsaicin‐sensitive sensory afferents
Authors: Liu Xue Jun , White Thomas D. , Sawynok Jana
Published: March 2003

Glutamate receptors have been identified on the peripheral terminals of both primary sensory afferents and sympathetic post‐ganglionic neurons, and activation of these receptors produces peripheral sensitization and enhances nociception. Adenosine is an endogenous agent that has a regulatory effect on pain. In brain and spinal cord, adenosine release can be promoted by excitatory amino acids. In the present study, we used in vivo microdialysis to determine whether glutamate also can release adenosine in peripheral tissues. Rats were anesthetized with pentobarbital and microdialysis probes were implanted into the subcutaneous tissue of the plantar aspect of the rat hind paw. Subcutaneous injection of glutamate (50 μL, 0.3–100 μmol) evoked a short‐lasting adenosine release immediately following drug injection. Co‐administration of either the N‐methyl‐d‐aspartate (NMDA) receptor antagonist, dizocipine maleate (MK‐801, 1 nmol) or the non‐NMDA receptor antagonist, 6‐cyano‐7‐nitroquinoxaline (CNQX, 10 nmol) with glutamate blocked such release, suggesting an involvement of peripheral ionotropic glutamate receptors in this response. Systemic pre‐treatment with capsaicin, a neurotoxin selective for unmyelinated sensory afferents, significantly reduced glutamate‐evoked peripheral adenosine release, but release was not affected by systemic pre‐treatment with 6‐hydroxydopamine, a neurotoxin selective for sympathetic nerve efferents. Neither MK‐801 nor CNQX blocked 5% formalin‐evoked adenosine release, suggesting adenosine release by formalin is not secondary to ionotropic glutamate receptor activation. We conclude that administration of glutamate evokes peripheral adenosine release, and that peripheral ionotropic glutamate receptors on unmyelinated sensory afferents are involved in such release. The released adenosine may provide a negative feedback control on nociception.
Nicotine activates the extracellular signal‐regulated kinase 1/2 via the α7 nicotinic acetylcholine receptor and protein kinase A, in SH‐SY5Y cells and hippocampal neurones
Authors: Dajas‐Bailador F. A. , Soliakov L. , Wonnacott S.
Published: March 2003

Neuronal nicotinic acetylcholine receptors (nAChR) can modulate many cellular mechanisms, such as cell survival and memory processing, which are also influenced by the serine/threonine protein kinases ERK1/2. In SH‐SY5Y cells and hippocampal neurones, nicotine (100 µm) increased the activity of ERK1/2. This effect was Ca2+ dependent, and prevented by the α7 nAChR antagonist α‐bungarotoxin (α‐Bgt) and an inhibitor (PD98059) of the upstream kinase MEK. To determine the intervening steps linking Ca2+ entry to MEK‐ERK1/2 activation, inhibitors of Ca2+‐dependent kinases were deployed. In SH‐SY5Y cells, selective blockers for PKC (Ro 31–8220), CaM kinase II (KN‐62) or PI3 kinase (LY 294002) failed to inhibit the nicotine‐evoked increase in ERK1/2 activity. In contrast, two structurally different inhibitors of PKA (KT 5720 and H‐89) completely prevented the nicotine‐dependent increase in ERK1/2 activity. Inhibition of the nicotine‐evoked increase in ERK1/2 activity by H‐89 was also observed in hippocampal cultures. Down stream of PKA, the activity of B‐Raf was significantly decreased by nicotine in SH‐SY5Y cells, as determined by direct measurement of MEK1 phosphorylation or in vitro kinase assays, whereas the modulation of MEK1 phosphorylation by Raf‐1 tended to increase. Thus, this study provides evidence for a novel signalling route coupling the stimulation of α7 nAChR to the activation of ERK1/2, in a Ca2+ and PKA dependent manner.
Formation of carnosine‐Cu(II) complexes prevents and reverts the inhibitory action of copper in P2X4 and P2X7 receptors
Authors: Coddou Claudio , Villalobos Claudio , González Jorge , Acuña‐Castillo Claudio , Loeb Bárbara , Huidobro‐Toro J. Pablo
Published: March 2003

To further analyze the action of copper on brain synaptic mechanisms, the brain dipeptide carnosine (β‐alanyl‐l‐histidine) was tested in Xenopus laevis oocytes expressing the rat P2X4 or P2X7 receptors. Ten micromolar copper halved the currents evoked by ATP in both receptors; co‐application of carnosine plus copper prevented the metal induced‐inhibition with a median effective concentration of 12.1 ± 3.9 and 12.0 ± 5.5 µm for P2X4 and P2X7, respectively. Zinc potentiated only the P2X4 ATP‐evoked currents; carnosine had no effect over this metal. The relative potency and selectivity of classical metal chelators to prevent the copper inhibition was compared between carnosine and penicillamine (PA), bathophenanthroline (BPh) or l‐histidine (His). Their rank order of potency in P2X4 and P2X7 receptors was carnosine = PA = His > BPh > Glycine (Gly) and carnosine = BPh = His > PA > Gly, respectively. The potency to prevent the zinc‐induced potentiation in the P2X4 receptor was BPh > PA > His; carnosine, Gly and β‐alanine were inactive. Whereas 1–100 µm carnosine or His alone did not modify the ATP‐evoked currents, 10–100 µm PA augmented and 100 µm BPh decreased the ATP‐evoked currents. Carnosine was able to revert the copper‐induced inhibition restoring the maximal ATP gated current in a concentration‐dependent manner. Electronic spectroscopy confirm the formation of carnosine‐Cu(II) complexes, mechanism that can account for the prevention and reversal of the copper inhibition, revealing its potential in copper intoxication treatment.
Prostacyclin‐induced rundown of N‐methyl‐d‐aspartate receptor currents in HEK293 cells is protein kinase A‐dependent and NR2 subunit‐selective
Authors: Woodward John J.
Published: March 2003

Previous studies in neurons have demonstrated a rapid decrease in NMDA receptor currents following tyrosine kinase inhibition or exposure to platelet‐derived growth factor (PDGF). Inhibitors of protein kinase A␣(PKA) block the PDGF‐induced rundown suggesting a multistep pathway that leads to decreased amplitudes of NMDA‐activated currents. In this study, HEK293 cells expressing different NMDA receptor subunits were used to study the effects of prostacyclin receptor‐mediated PKA activation on the magnitude of glutamate‐activated currents. The prostacyclin agonist iloprost induced a rapid and time‐dependent depression of otherwise stable glutamate‐activated currents in cells expressing NR1–2a/2A or NR1–2a/2D receptors but not NR1–2a/2B or NR1–2a/2C receptors. This rundown was prevented by treatment of cells with the PKA inhibitor H89. The iloprost effect persisted in cells coexpressing NR1–2a/2A receptors and either wild‐type or mutant Src kinase (SrcS17A). Co‐expression of PSD‐95 with NR1–2a/2A receptors reduced but did not eliminate the extent of rundown. Iloprost also produced current rundown in cells expressing NR1–2a and a C‐terminal truncated NR2A subunit (NR2A1050stop) but not in those transfected with an NR2A tyrosine mutant (Y842F). The iloprost‐induced rundown of wild‐type NR1–2a/2A receptors was prevented by prior exposure of cells to hypertonic sucrose. These results suggest that PKA influences the functional activity of NMDA receptors in an NR2 subunit‐selective fashion.
Involvement of GABA and cholinergic receptors in the nucleus accumbens on feedback control of somatodendritic dopamine release in the ventral tegmental area
Authors: Rahman Shafiqur , McBride William J.
Published: March 2003

The objectives of the present study were to examine the involvement of GABA and cholinergic receptors within the nucleus accumbens (ACB) on feedback regulation of somatodendritic dopamine (DA) release in the ventral tegmental area (VTA). Adult male Wistar rats were implanted with ipsilateral dual guide cannulae for in vivo microdialysis studies. Activation of the feedback system was accomplished by perfusion of the ACB with the DA uptake inhibitor GBR 12909 (GBR; 100 µm). To assess the involvement of GABA and cholinergic receptors in regulating this feedback system, antagonists (100 µm) for GABAA (bicuculline, BIC), GABAB (phaclofen, PHAC), muscarinic (scopolamine, SCOP), and nicotinic (mecamylamine, MEC) receptors were perfused through the probe in the ACB while measuring extracellular DA levels in the ACB and VTA. Local perfusion of the ACB with GBR significantly increased (500% of baseline) the extracellular levels of DA in the ACB and produced a concomitant decrease (50% of baseline) in the extracellular DA levels in the VTA. Perfusion of the ACB with BIC or PHAC alone produced a 200–400% increase in the extracellular levels of DA in the ACB but neither antagonist altered the levels of DA in the VTA. Co‐perfusion of either GABA receptor antagonist with GBR further increased the extracellular levels of DA in the ACB to 700–800% of baseline. However, coperfusion with BIC completely prevented the reduction in the extracellular levels of DA in the VTA produced by GBR alone, whereas PHAC partially prevented the reduction. Local perfusion of the ACB with either MEC or SCOP alone had little effect on the extracellular levels of DA in the ACB or VTA. Co‐perfusion of either cholinergic receptor antagonist with GBR markedly reduced the extracellular levels of DA in the ACB and prevented the effects of GBR on reducing DA levels in the VTA. Overall, the results of this study suggest that terminal DA release in the ACB is under tonic GABA inhibition mediated by GABAA (and possibly GABAB) receptors, and tonic cholinergic excitation mediated by both muscarinic and nicotinic receptors. Activation of GABAA (and possibly GABAB) receptors within the ACB may be involved in the feedback inhibition of VTA DA neurons. Cholinergic interneurons may influence the negative feedback system by regulating terminal DA release within the ACB.
Evidence for a γ‐hydroxybutyrate (GHB) uptake by rat brain synaptic vesicles
Authors: Muller Claude , Viry Sandrine , Miehe Monique , Andriamampandry Christian , Aunis Dominique , Maitre Michel
Published: March 2003

γ‐Hydroxybutyrate (GHB) is an endogenous metabolite of mammalian brain which is derived from GABA. Much evidence favours its role as an endogenous neuromodulator, synthesized, stored and released at particular synapses expressing specific receptors. One key step for GHB involvement in neurotransmission is its uptake by a specific population of synaptic vesicles. We demonstrate that this specific uptake exists in a crude synaptic vesicle pool obtained from rat brain. The kinetic parameters and the pharmacology of this transport are in favour of an active vesicular uptake system for GHB via the vesicular inhibitory amino acid transporter. This result supports the idea that GABA and GHB accumulate together and are coliberated in some GABAergic synapses of the rat brain, where GHB acts as a modulatory factor for the activity of these synapses following stimulation of specific receptors.
Development of anatomical structure of roots of Phragmites australis
Authors: Soukup Aleš , Votrubová Olga , Čížková Hana
Published: March 2003

Focusing on characters related to its survival in flooded soils, the anatomy and differentiation of roots of Phragmites australis is reported here.

Roots were examined by anatomical methods and permeability tests using periodate‐, Fe2+‐ and berberine‐based apoplastic tracers.

Root development was characterized by the differentiation of a multiseriate exodermis with suberin lamellae and Casparian bands that formed close to the root tip. Impregnation of the exodermis with lignin and/or suberin appeared closer to the apex than in the endodermis, which is not commonly observed in other plant species. The early developed exodermis proved to be an effective barrier restricting the passive apoplastic penetration of solutes from the rooting medium into the root tissues. Relationships between exodermis, endodermis, aerenchyma and lateral root primordia development were also recorded.

It is concluded that early differentiation of the exodermis was advantageous in flooded substrates. Only a limited proportion of tissue without this apoplastic barrier might be crucial to reduce radial oxygen loss to the sediment and restrain the action of unfavourable factors, such as phytotoxins, in a flooded sediment.
Invasion of vascular cells in vitro by Porphyromonas endodontalis
Authors: Dorn B. R. , Harris L. J. , Wujick C. T. , Vertucci F. J. , Progulske‐Fox A.
Published: March 2003

Aim The objective of this study was to determine whether laboratory strains and clinical isolates of microorganisms associated with root canal infections can invade primary cultures of cardiovascular cells.

Methodology Quantitative levels of bacterial invasion of human coronary artery endothelial cells (HCAEC) and coronary artery smooth muscle cells (CASMC) were measured using a standard antibiotic protection assay. Transmission electron microscopy was used to confirm and visualize internalization within the vascular cells.

Results Of the laboratory and clinical strains tested, only P. endodontalis ATCC 35406 was invasive in an antibiotic protection assay using HCAEC and CASMC. Invasion of P. endodontalis ATCC 35406 was confirmed by transmission electron microscopy.

Discussion Certain microorganisms associated with endodontic infections are invasive. If bacterial invasion of the vasculature contributes to the pathogenesis of cardiovascular disease, then microorganisms in the pulp chamber represent potential pathogens.
Discovery simulations and the assessment of intuitive knowledge
Authors: Swaak J. , De Jong T.
Published: March 2003

Abstract The objective of the present work is to have a closer look at the relations between the features of discovery simulations, the learning processes elicited, the knowledge that results, and the methods used to measure this acquired knowledge. It is argued that discovery simulations are ‘rich’, have a relatively low transparency, and require active involvement of learners. Discovery simulations are suited to support data‐driven, partly implicit learning. Discovery learning leads to intuitive knowledge. To complement this conceptual investigation, a series of five experimental studies is described. In all five studies, learners were pre‐tested and post‐tested with several knowledge measures. Central to the set of tests was one with the objective of measuring intuitive knowledge. One conclusion of these experimental studies is that assignments contribute most clearly to the instructional effectiveness of simulations. Another conclusion is that the intuitive knowledge tests seem able to measure the results of learning with discovery simulations.
Using technology in Higher Education: an Activity Theory perspective
Authors: Isssroff K. , Scanlon E.
Published: March 2003

Abstract This paper describes the application of Activity Theory to considerations of enhancing learning through the use of technology in Higher Education. The theory is reviewed and its extended version which uses the idea of an activity system to help analyse the use of technology in context described. Two case studies of teaching and learning in Higher Education are described: one exploring the use of ICT in a postgraduate study of science communication and the other a history course using the web to provide a range of resources and communication facilities for students. These two case studies represent different uses of technology in different disciplines and lead to a consideration of how the use of Activity Theory informs understanding of these learning experiences.
The contribution of computer‐based activities to understanding statistics
Authors: Morris E.J. , Joiner R. , Scanlon E.
Published: March 2003

Psychology students often find statistical concepts difficult, and research has suggested that students can hold confusions about seemingly straightforward concepts, such as the mean. Although previous research has evaluated computer‐based learning systems for statistics, there is little research that has looked specifically at whether particular computer‐based learner activities contribute to students' understanding of introductory concepts in statistics. The study described in this paper was designed to investigate whether computer‐based activities that provide multiple representations of concepts contribute to students' understanding of correlations and measures of central tendency. A pre‐/post‐test control group design was used involving 50 students who were studying psychology. It was found that activities involving the direct manipulation of data contributed to students' understanding of measures of central tendency as indicated by a significant improvement from pre‐ to post‐test. However, findings indicated that computer‐based activities of this kind did not necessarily contribute to students' understanding of correlations.
Using computer algebra systems in mathematical classrooms
Authors: Kramarski B. , Hirsch C.
Published: March 2003

Abstract This paper describes a research whose main focus is the use of Computer Algebra Systems (CAS) in mathematical classrooms and the didactical possibilities linked with its use. The possibilities of integrating Self‐Regulated Learning (SRL) within the CAS environment are brought into focus. Forty‐three Israeli students (mean age 13.3) were assigned to two learning algebraic groups. The first group received explicit meta‐cognitive SRL with CAS (CAS + SRL); the second group was exposed to CAS without SRL (CAS). Empirical results from the experimental and case study designs revealed that (CAS + SRL) students outperformed (CAS) students on algebraic thinking and that (CAS + SRL) students regulated their learning more effectively.
Repellent effects on Anopheles arabiensis biting humans in Kruger Park, South Africa
Authors: Govere J. , Braack L. E. O. , Durrheim D. N. , Hunt R. H. , Coetzee M.
Published: March 2003

Abstract. Distribution of biting sites on the human body by the malaria vector Anopheles arabiensis Patton (Diptera: Culicidae) was investigated near a source of mosquitoes in the Kruger National Park, South Africa. Eight adult male volunteers (2 teams × 2 pairs of subjects) conducted human bait collections while seated on camp chairs in the open‐air, wearing only short trousers (no shirt, socks or shoes). Mosquito collections during 18.30–22.30 hours on five consecutive nights in April 1998 yielded a total of 679 An. arabiensis females biting subjects with or without their ankles and feet treated with deet insect repellent (15% diethyl‐3‐methylbenzamide, Tabard™ lotion). On subjects whose feet and ankles were smeared with repellent, 160 An. arabiensis females were captured biting in 60 man‐hours: 88.1% on the legs, 1.4% on the arms and 1.2% on other parts of the body, but none on the repellent‐treated feet or ankles. On subjects without repellent treatment, 519 An. arabiensis were caught biting in 60 man‐hours: 81.1% on feet and ankles, 16.4% on legs, 1.4% on arms and 1.2% on the rest of the body. For individual subjects, the reduction of An. arabiensis bites ranged from 36.4 to 78.2% (mean protection 69.2%). Results of this study confirm previous findings that, in this part of South Africa − inhabited only by wildlife − when people sit outside during the evening An. arabiensis prefers to bite their lower limbs: 97.5% below the knees. Overall, the number of bites by the malaria vector An. arabiensis was reduced more than three‐fold (from 26 to 8/person/evening), simply by treating ankles and feet with a consumer brand of deet repellent. Whether or not this provides a satisfactory degree of protection against malaria risk would depend on the malaria sporozoite rate in the malaria vector population.
Morphology and structural organization of Gene's organ in Argas walkerae
Authors: Schöl H. , Edelmann B. , Göbel E. , Gothe R.
Published: March 2003

Abstract. Electron microscopy revealed that Gene's organ in females of Argas walkerae Kaiser & Hoogstraal (Ixodida: Argasidae) is formed as a double‐sac structure consisting of an outer epithelial and an inner cuticular sac. The latter emerges through the camerostomal aperture to the exterior in ovipositing ticks. The epithelial sac forms the corpus and the two blind‐ending horns, which pass into the epithelium of the excretory duct of a gland at each side of Gene's organ and envelop the cuticular sac. Both excretory ducts open into the lumen between the epithelial and the cuticular sac. The cuticular sac is folded and consists of a fibrous endocuticula outwards towards the lumen between the epithelial and the cuticular sac and of a smooth epicuticula inwards. Parallel running grooves occur over the lateral epicuticular surface turning medially into cobble‐stone pavement‐like rises. Tubuli pass through the cuticular sac ending in pores on the epicuticular surface and open into the lumen between the epithelial and the cuticular sac. Muscle fibres pass through the epithelial sac at the horn tips and are inserted to the cuticular sac. In ovipositing females, the glands are fully developed and the lumen between the epithelial and the cuticular sac is filled with an amorphous mass.
Phylogeny of the Neuropterida (Insecta: Holometabola)
Authors: Aspöck Ulrike
Published: March 2003

The Neuropterida, with about 6500 known species — living fossils in a way — at the base of the Holometabola (as a sister group of the Coleoptera), comprise Raphidioptera (about 210 species, two families), Megaloptera (about 300 species, two families) and Neuroptera (6000 species, 17 families). Megaloptera + Neuroptera is argued vs. the traditional Raphidioptera + Megaloptera. Raphidioptera are undisputedly monophyletic. Monophyly of Megaloptera is the operational hypothesis, although occasionally questioned. Sucking tubes of the larvae are the most spectacular autapomorphy of Neuroptera. The construction of larval head capsules indicates three evolutionary lines: Nevrorthiformia, and Myrmeleontiformia + Hemerobiiformia. Traditional Myrmeleontiformia is Psychopsidae + (Nemopteridae + (Nymphidae + (Myrmeleontidae + Ascalaphidae))), the present approach is (Psychopsidae + Nemopteridae) + all other Myrmeleontiformia. Hemerobiiformia are based on the ‘maxillary head’ concept. The ithonid clade Ithonidae/Rapismatidae + Polystoechothidae and the dilarid clade Dilaridae + (Mantispidae + (Rhachiberothidae + Berothidae)) are based on robust criteria. Other relationships remain unclear: Hemerobiidae + Chrysopidae (on similarity) and the ‘early offshoot’ concept of coniopterygidae (on autapomorphies) should not be perpetuated. Chysopidae + Osmylidae and (Hemerobiidae + (Coniopterygidae + Sisyridae)) + dilarid clade are discussed. Aquatic larvae, regarded as independent apomorphies of megaloptera and neuropteran Nevrorthidae and Sisyridae for a long time, are re‐interpreted as a synapomorphy of Megaloptera + Neuroptera and thus plesiomorphic within these groups. Terrestrial larvae (with cryptonephry to solve osmotic problems) are consequently apomorphic. Aquatic Sisyridae with cryptonephry of a single malpighian tubule, is conflicting, but larvae may have become secondarily aquatic, after a terrestrial intermezzo.
Gene expression of adrenomedullin, leptin, their receptors and neuropeptide Y in hormone‐secreting and non‐functioning pituitary adenomas, meningiomas and malignant intracranial tumours in humans
Authors: Knerr I. , Schuster S. , Nomikos P. , Buchfelder M. , Dötsch J. , Schoof E. , Fahlbusch R. , Rascher W.
Published: March 2003

The aim of this study was to assess human intracranial tumours for their gene expression pattern of the vasoactive peptide adrenomedullin (AM), its receptor (AM‐R) and leptin, which exerts multiple biological effects including proliferation and angiogenesis via the leptin receptor (OB‐Rb). Gene activity of neuropeptide Y (NPY) was monitored additionally. We investigated whether there was a characteristic gene expression pattern of AM and leptin in different intracranial tumours, depending on their proliferation activity and biological behaviour. We investigated 35 non‐functioning pituitary adenomas (including eight null cell, four silent plurihormonal, 23 silent gonadotroph adenomas), seven somatotropinomas, seven prolactinomas, eight meningiomas, five astrocytomas, two glioblastoma multiformes and unaffected temporal lobe (n = 8). Quantitative reverse transcriptase‐polymerase chain reaction (TaqMan® RT‐PCR) was performed. AM mRNA was detectable in all tumour specimens. AM/GAPDH (glyceraldehyde‐3‐phosphate dehydrogenase) ratio was significantly higher in somatotropinomas, as was AM/CD31 ratio in prolactinomas, compared with inactive adenomas (P < 0.05). AM‐R mRNA was found in all tumour subgroups in small quantities but, in general, higher in tumours than in temporal lobe tissue, respectively. AM‐R/CD31 ratio was significantly higher in prolactinomas than in inactive adenomas (P < 0.05). Leptin was detectable in very low quantities in each subgroup. OB‐Rb gene expression was found in all tumour subgroups, OB‐Rb/GAPDH ratio was highest for meningiomas (P < 0.0001, compared with temporal lobe). NPY mRNA was detectable in temporal lobe in higher quantities than in tumours (P < 0.0001), and almost undetectable in prolactinomas and astrocytomas. Our data demonstrate that AM and AM‐R, NPY, as well as leptin and OB‐Rb, are expressed in various intracranial tumours in humans but their particular function has to be elucidated further. At present, there is no evidence for a cross‐talk on transcriptional level between the peptidergic vasodilative system AM and the putative angiogenic and proliferation affecting factor leptin.
Chemical properties allow stingless bees to place their eggs upright on liquid larval food
Authors: Jungnickel Harald , Velthuis Hayo H. W. , Imperatriz Fonseca Vera L. , Morgan E. David
Published: March 2003

Abstract. Queen‐laid eggs of Melipona bees stand upright on their larval food, in part because the upper part of the egg is covered with a water‐repellent layer of fatty acids and C21 to C29 hydrocarbons. The lower, wettable portion does not have these materials. Trophic eggs laid by workers are essentially devoid of this coating and tend to sink in the food, when not detected and consumed by the queen. Reproductive workers' eggs, which have about 50% of the water‐repellent coating in comparison with the queen's eggs, are usually laid in the cell after oviposition by the queen, and therefore there are two eggs in the cell. Surface tension forces cause the two eggs to float towards each other so they become attached. When alone inside the cell, the reproductive worker egg often floats at an angle to the surface, reflecting the instability of this kind of egg. Attachment to a queen's egg therefore compensates this instability and enhances the reproductive worker egg's chances to develop. Such reproductive worker eggs have about 50% of the water‐repellent coating in comparison with the queen's eggs. The surface of an ‘undetermined’ egg laid by a worker was much closer in composition to that of a queen's egg, from which it is deduced that this was the rarer type of reproductive worker egg, namely those that are laid before queen oviposition has taken place. The layer of hydrophobic material on a queen's egg is about one molecule thick, and probably orientated with the carboxyl groups toward the chorion of the egg and the hydrocarbon chains perpendicular to the surface.
Anti‐elastase and anti‐hyaluronidase of phenolic substance from Areca catechu as a new anti‐ageing agent
Authors: Lee K.‐K. , Cho J.‐J. , Park E.‐J. , Choi J.‐D.
Published: March 2003

Synopsis We have previously screened 150 medicinal plants for the inhibition of elastase and found significant inhibitory effects of the extracts of Areca catechu L. on the ageing and inflammation of skin tissues. To isolate and identify the compounds having biological activity, they were further purified by each fraction of solvents, silica gel column chromatography, preparative TLC and reversed‐phase HPLC. The peak in HPLC, which coincided with the inhibitory activity against elastase, was identified as a phenolic substance by using various colorimetric methods, UV and IR. IC50 values of this phenolic substance were 26.9 μg mL−1 for porcine pancreatic elastase (PPE) and 60.8 μg mL−1 for human neutrophil elastase (HNE). This phenolic substance showed more potent activity than that of reference compounds, oleanolic acid (76.5 μg mL−1 for PPE, 219.2 μg mL−1 for HNE) and ursolic acid (31.0 μg mL−1 for PPE, 118.6 μg mL−1 for HNE). According to the Lineweaver–Burk plots, the inhibition against both PPE and HNE by this phenolic substance was competitive inhibition with the substrate. The phenolic substance from A. catechu effectively inhibited hyaluronidase activity (IC50 : 210 μg mL−1 ).

These results suggest that the phenolic substance purified from A. catechu has an anti‐ageing effect by protecting connective tissue proteins.
Nitric oxide production by a murine macrophage cell line (RAW264.7) stimulated with lipopolysaccharide from Actinobacillus actinomycetemcomitans
Authors: Sosroseno W. , Barid I. , Herminajeng E. , Susilowati H.
Published: March 2003

The aim of this study was to determine whether Actinobacillus actinomycetemcomitans lipopolysaccharide (LPS‐A. actinomycetemcomitans) could stimulate a murine macrophage cell line (RAW264.7 cells) to produce nitric oxide (NO). The cells were treated with LPS‐A. actinomycetemcomitans or Escherichia coli LPS (LPS‐Ec) for 24 h. The effects of NG‐monomethyl‐L‐arginine (NMMA), polymyxin B and cytokines (IFN‐γ, TNF‐α, IL‐4 and IL‐12) on the production of NO were also determined. The role of protein tyrosine kinase, protein kinase C and microtubulin organization on NO production were assessed by incubating RAW264.7 cells with genistein, bisindolylmaleide and colchicine prior to LPS‐A. actinomycetemcomitans stimulation, respectively. NO levels from the culture supernatants were determined by the Griess reaction. The results showed that LPS‐A. actinomycetemcomitans stimulated NO production by RAW264.7 cells in a dose‐dependent manner, but was slightly less potent than LPS‐Ec. NMMA and polymyxin B blocked the production of NO. IFN‐γ and IL‐12 potentiated but IL‐4 depressed NO production by LPS‐A. actinomycetemcomitans‐stimulated RAW264.7 cells. TNF‐α had no effects on NO production. Genistein and bisindolylmalemaide, but not colchicine, reduced the production of NO in a dose‐dependent mechanism. The results of the present study suggest that A. actinomycetemcomitans LPS, via the activation of protein tyrosine kinase and protein kinase C and the regulatory control of cytokines, stimulates NO production by murine macrophages.