bluuebunny/crossref_metadata_2025 huggingface dataset:
Continuous imaging of amino‐acid translocation in intact mycelia of Phanerochaete velutina reveals rapid, pulsatile fluxes
Authors: Tlalka M. , Watkinson S. C. , Darrah P. R. , Fricker M. D.
Published: March 2003

Nitrogen translocation by woodland fungi is ecologically important, however, techniques to study long‐distance amino‐acid transport in mycelia currently have limited spatial and temporal resolution. We report a new continuous, noninvasive imaging technique for β‐emitters that operates with submillimetre spatial resolution and a practical sampling interval of 10–60 min.

 Transport of the nonmetabolized, 14C‐labelled amino‐acid analogue, α‐aminoisobutyric acid (AIB) was imaged using a photon‐counting camera as it was transported in foraging mycelium of the cord‐forming woodland fungus, Phanerochaete velutina, grown over an intensifying screen in microcosms.

 The maximum acropetal transport velocity of 14C‐AIB to the colony margin was 50 mm h−1 (average 23 mm h−1), with a mass transfer of 4.6–51.5 pmol 14C‐AIB h−1 per cord. Transport in cords had a pulsatile component with a period of 11–12 h.

 Transport was significantly faster than diffusion, consistent with rapid cycling of nutrients throughout the mycelium between loading and sink regions. The increased spatial and temporal resolution of this method also revealed the rhythmic nature of transport in this fungus for the first time.
Green cotyledons of two Hakea species control seedling mass and morphology by supplying mineral nutrients rather than organic compounds
Authors: Lamont Byron B. , Groom Philip K.
Published: March 2003

Hakea species dominate shrubby vegetation on seasonally dry, nutrient‐impoverished soils in Australia. We hypothesized that the exposed cotyledons control growth of the young seedling by providing it with mineral nutrients rather than C‐based compounds.

Two representative species with differing seed masses were tested. Cotyledon removal caused large reductions in plant mass and dimensions, but little effect on specific leaf area. Cotyledons expanded markedly on germination although their chlorophyll content was much lower than the first leaves. Shading the cotyledons or applying a C‐storage compound (inositol) to the soil had no consistent effect on seedling properties.

Cotyledon removal greatly reduced seedling P (especially), N, K, Ca, Mg and Cu, but not Fe or Mn, whereas shading the cotyledons had no effect. Transfer of mineral nutrients from the embryos to the seedlings in their natural soils varied from 90 to 2% (for P and Ca, respectively), and accounted for 79% of total content (P) to negligible (K, Ca, Fe) at 3 months. Cotyledons indirectly increased soil nutrient uptake. Addition of P, N or P + N after cotyledon removal had no benefit but addition of P + N + K + Mg + S restored morphology and nutrient content.

In nutrient and water‐limited habitats with abundant light, cotyledons in Hakea spp. might serve to maximize supply of mineral nutrients to the shoots, which then maximize C‐supply to the rapidly elongating roots.
Crown architecture of Populus spp. is differentially modified by free‐air CO2 enrichment (POPFACE)
Authors: Gielen B. , Calfapietra C. , Claus A. , Sabatti M. , Ceulemans R.
Published: March 2003

Although canopy architecture is a prime determinant of forest functioning and productivity, it has received little attention when examining forest responses to rising atmospheric CO2 concentrations. In this study different characteristics of crown architecture of two Populus species and one hybrid were investigated within a high‐density poplar plantation. A free‐air CO2 enrichment (FACE) facility was used to mimic future elevated CO2 concentrations.

 Canopy depth and branching patterns were studied, and detailed branch characteristics such as branch dimension, inclination, and internodal length were assessed for the three poplar species in the FACE and control treatments.

 Effects of elevated CO2 were restricted to a significantly increased canopy depth and longer internodal lengths after two years of CO2 enrichment. Additionally, branch dimensions and sylleptic branch numbers were increased by FACE, but responses were variable among growing seasons and species. However, FACE did not affect branch angles of origin and termination.

 Crown architecture was modified mainly through a growth stimulation in response to FACE. Nevertheless, important differences among species were observed which may influence future CO2 responses when competition will become more important.
Effects of relative humidity, light intensity and photoperiod on the colony development of Erysiphe sp. on Rhododendron
Authors: Kenyon D. M. , Dixon G. R. , Helfer S.
Published: March 2003

Growth and reproduction by powdery mildew pathogens is generally inhibited by decreasing relative humidity. With Erysiphe sp. on Rhododendron cv. Elizabeth, the initial stages of colony development were adversely affected by reducing the relative humidity from 100% to 70 and 85%. No significant effects on secondary or tertiary hyphal development were detected. Light intensity and photoperiod both had considerable effect on the induced resistance response of the host. Over the initial 5 days of colonization there were no significant differences between any of the treatments. After 13 days, however, expansion of fungal colonies at 180 photosynthetic active radiation (PAR) was limited solely to the area initially infested by primary hyphae. By comparison, in colonies grown at 80 PAR regardless of day length, secondary and tertiary hyphae had extended beyond the area first colonized. These effects resulted in differing morphologies, small colonies of densely packed hyphae formed at 180 PAR compared with open spreading colonies at 80 PAR.
Microtubule dynamics in compatible and incompatible interactions of soybean hypocotyl cells with Phytophthora sojae
Authors: Cahill D. , Rookes J. , Michalczyk A. , McDonald K. , Drake A.
Published: March 2003

The arrangement of microtubules in soybean (Glycine max) cells was examined during compatible and incompatible interactions of hypocotyls of soybean cv. Harosoy (susceptible) and cv. Haro 1272 (resistant) with race 1 of the soybean‐specific pathogen Phytophthora sojae. Both reaction types were similar during the first 3 h after zoospore inoculation in terms of the number of cells penetrated, and depth penetrated into the cortex. By 3 h postinoculation, clear differences had developed between the two interaction types: incompatible interactions were characterized by a hypersensitive response that was confined to single penetrated cells; while compatibly responding cells appeared unchanged. Both types of response were characterized by autofluorescence of cell walls or cytoplasm and, at 6 h after inoculation, complete disorganization of cell cytoplasm. Reorientation and loss of microtubules was seen in the early stages of the incompatible interaction in association with cellular hypersensitivity, but not in compatible responses. In cells adjacent to those that reacted hypersensitively, there was little evidence of change in microtubule orientation. Treatment of hypocotyls with the microtubule depolymerizer oryzalin prior to inoculation did not alter the compatible response, but led to breakdown of the incompatible response. Changes in microtubule orientation and state are thus among the first structural changes that are visible within cells during incompatibility in this system.
Kinetics of CFU‐Mk after automated plateletpheresis
Authors: Wagner T. , Schwartz D. W. M. , Winter M. , Kabrna E. , Kollars M. , Schwarzinger I. , Lanzer G. , Mayr W. R. , Geissler K.
Published: March 2003

Background and Objectives

Platelet count, thrombopoetin (TPO) level and the compartment of megakaryocyte progenitor cells (CFU‐Mk) are major determinants in the regulation of thrombopoiesis. The aim of this study was to investigate the potential changes in the compartment of CFU‐Mk and their correlation with serum TPO levels and platelet count after plateletpheresis.

Materials and methods

Twelve healthy individuals were randomly assigned to undergo single‐donor plateletpheresis. A collagen‐based in vitro culture system was used to determine the number of peripheral blood (PB) CFU‐Mk before and after donation and on days 1, 4 and 7 thereafter. TPO levels were measured by a specific enzyme‐linked immunosorbent assay and whole blood counts were performed using an automated cell counter.

Results

The pre‐apheresis platelet count (mean ± SEM: 276 ± 13 × 109/l) decreased after plateletpheresis to a nadir of 194 ± 8 × 109/l (P < 0·001), showed a gradual increase on days 1 and 4, and reached pre‐apheresis values by day 7 (280 ± 11). The serum TPO levels were found to be significantly increased on days 1 and 7 as compared to baseline levels (baseline value 103·3 ± 18·5 pg/ml versus day‐1 value 135·8 ± 25·8 pg/ml and day‐7 value 132 ± 30·19 pg/ml; P < 0·03 and P < 0·03, respectively). The numbers of CFU‐Mk in PB were significantly elevated on day 4 only (125 ± 21 colonies/ml of PB versus pre‐apheresis values of 68 ± 18 colonies/ml of PB, P < 0·005).

Conclusions

These findings suggest that platelet loss during plateletpheresis affects thrombopoiesis at the progenitor cell level, probably through alterations in TPO plasma concentrations.
Multivariate analysis of determinants of bacterial contamination of whole‐blood donations
Authors: Perez P. , Bruneau C. , Chassaigne M. , Salmi L. R. , Noel L. , Allouch P. , Audurier A. , Gulian C. , Janus G. , Boulard G. , De Micco P.
Published: March 2003

Background and Objectives Introduction of bacteria into blood components at the collection stage seems to be a frequent occurrence. We therefore assessed determinants of bacterial contamination of whole‐blood donations to gain insight into contamination mechanisms and direct prevention.

Materials and Methods A cross‐sectional study was carried out on donors accepted for whole‐blood donation in four French blood banks. Each blood bank used its own two‐stage procedure for phlebotomy site preparation. Contamination was identified by culturing two 15‐ml samples (collected aseptically at the outset of donation) in a BacT/Alert 240® system. Determinants were assessed by logistic regression analysis.

Results Bacterial contamination, mainly by skin flora, occurred in 76 (2·2%) out of 3385 donations. Significant determinants were as follows: the blood bank (odds ratio [OR] range = 3·0–5·6, P < 0·001); lack of repetition of scrub (OR = 2·7, P = 0·032); and donor age > 35 years (OR = 1·8, P = 0·036).

Conclusion Systematic scrub repetition should be implemented to reduce bacterial contamination by skin flora at the collection stage. Further research is required to clarify the role of different antiseptic agents and of donor age.
Inclusion trail patterns in porphyroblasts from the Foothills Terrane, California: a record of orogenesis or local strain heterogeneity?
Authors: Paterson S. R. , Vernon R. H.
Published: March 2003

A major problem with the current use of porphyroblast–matrix microstructural relationships to infer orogenic histories, such as multiple orthogonal orogenic events, is that other evidence for these events is typically lacking. For example, a comparison of regional relationships and local structures formed in and adjacent to porphyroblasts present in contact aureoles in the Foothills Terrane, Sierra Nevada, California, shows that: (1) except in shear zones, contact aureoles and local zones along lithological contacts, the Foothills Terrane has a single regional cleavage, although locally formed by multiple processes; (2) the regional cleavage and locally developed porphyroblast inclusion trails have variable orientations, and neither dataset supports the formation of dominantly subhorizontal and subvertical cleavages in this orogen; (3) structural and metamorphic heterogeneities occur at all scales and can markedly affect inclusion trail patterns in porphyroblasts; (4) complex porphyroblast growth features and internal inclusion trail patterns can form in porphyroblasts that grow during short time intervals in contact aureoles, indicating that local complexity in porphyroblasts does not imply regional complexity. Because of these conclusions, multiple datasets, rather than data acquired only from porphyroblasts, should be considered when attempting to understand the evolution of orogens. Furthermore, using microstructural information preserved only in porphyroblasts to infer orogenic processes and plate motions is generally unjustified.
Submicron polyphase inclusions in garnet from the Tananao Metamorphic Complex, Taiwan: a key to unravelling otherwise unrecognized metamorphic events
Authors: Hwang S. L. , Yui T. F. , Chu H. T. , Shen P.
Published: March 2003

Kyanite and staurolite occur in the Tananao Metamorphic Complex as submicron inclusions in almandine‐rich garnet from a metamorphosed palaeosol weathering horizon, near Hoping, eastern Taiwan. Quartz, rutile/brookite and zircon are also found as associated submicron inclusions in garnet. Employing the reaction ilmenite+kyanite+quartz=almandine+rutile, and the breakdown of staurolite and quartz as thermobarometers, these submicron‐scale minerals formed at >8.3–8.8 kbar and < 660–690 °C. This P–T estimate is different from that (i.e. 5–7 kbar and 530–550 °C) derived from matrix minerals, which include almandine‐rich garnet, muscovite, chlorite, chloritoid, plagioclase, quartz and ilmenite. These results suggest that submicron inclusions in garnet‐like materials may record portions of the otherwise undocumented prograde path or provide information about previous metamorphic events and thus yield new insights into orogenic belts.
Awareness of toddlers' initial cognitive experiences with virtual reality
Authors: Passig D. , Klein P. , Noyman T.
Published: March 2003

Abstract In this study Virtual Reality technology was used to simulate a toddler's first few days' experiences in daycare and improve the caregiver's understanding of their state of mind. The virtual worlds were developed in accordance with toddlers' way of thinking and from their cognitive and visual viewpoint. The aim of the research was to investigate whether the caregiver's awareness to the cognitive experiences that toddlers undergo in their first days in kindergarten improves through a VR simulation of toddlers' worlds. Six cognitive elements of toddlers were simulated: object constancy; trial and error; perspective of height; perspective of things; egocentricity and imagination. The participants in this study were 40 (female) caregivers who work with infants aged 6 months to 4 years in private daycare. The findings indicate that experiencing a virtual world that reflects the real world of children improves the caregiver's awareness to the cognitive experiences that toddlers undergo in their first days in a kindergarten or daycare.
Student perceptions of a virtual field trip to replace a real field trip
Authors: Spicer J.I. , Stratford J.
Published: March 2003

Abstract  This study examines student perceptions on the use of virtual field trips (VFT) as part of their university experience and in particular the extent to which they could replace real field trips. While students were extremely positive about the potential of VFT to provide valuable learning experiences (and in particular a VFT constructed by the authors of this paper) nearly all of the students were insistent that it could not, and should not, replace real field trips. Furthermore when the same students were re‐approached after having been on a real field trip, these perceptions were strengthened and they thought VFT could be most effective in preparing for, or revising after, a real field trip.
The use of hypertext in the writing of group papers
Authors: Van Den Bosch H. , Bolluyt J.
Published: March 2003

Abstract The Virtual Constructing Tool (VCT) was developed at the Nijmegen School of Management in 1998. The VCT is intended to facilitate the process of writing group papers through the use of construction and communication tools and is based completely on the Internet. The VCT allows a paper to be structured by means of hyperlinking and cooperation between students. Students are allowed to divide tasks, but they are held responsible for the quality of the arguments in the paper as a whole. They are invited to spend time in dealing with validity claims and in building a valid train of thought. Producing a group paper includes four interrelated working processes: exploring the subject, exchanging information, arguing and discussing and editing. Hyperlinking offers a contribution in each of these processes which varies from associative linking of pieces of information to strengthening linear structuring. Therefore, a different perspective has been taken to that of those authors who consider hyperlinking as a tool par excellence for the nonlinear production of information.
Using narratives in conferences to improve the CMC learning environment
Authors: Ritchie G. , Peters S.
Published: March 2003

Abstract This paper reports on the use of short stories in Internet discussions to promote student learning. It describes off‐campus teacher education students CMC discussions of short stories concerning issues in human development. The content of students' discussions is analysed, as is their perceptions of the value of the discussion stories. The results indicate that the use of narratives can improve the social environment of online conferences and contribute to collaborative student learning.
The effects of mediation in computer assisted dynamic assessment
Authors: Tzuriel D. , Shamir A.
Published: March 2003

Abstract This study examined the effects of the computer‐assisted dynamic assessment (DA) on cognitive performance as compared to DA with an examiner. The DA approach is based on Feuerstein's mediated learning experience theory and Tzuriel's DA approach with young children. A sample of kindergarden children (n = 60) were assigned to either a Computer Assisted (CA, n = 30) or Examiner Only (EO, n = 30) groups. The sample was randomly chosen from three kindergardens in a middle‐SES area. Initial intelligence level of both groups was controlled by matching their frequency distribution on the Raven's Colored Progressive Matrices score. The CA group was administered the Think‐in‐Order program, which is a multimedia program designed specifically for this study and is based on the Children's Seriational Thinking Modifiability (CSTM) test. The EO group was administered the CSTM test by an examiner. The findings revealed that intervention involving mediation processes in a CA dynamic assessment procedure was more effective in bringing about significant cognitive changes than mediation with only an examiner.
Using a toolkit to support the evaluation of learning
Authors: Oliver M. , MacBean J. , Conole G. , Harvey J.
Published: March 2003

Abstract Many resources have been developed to support particular evaluation methodologies. However, the more complex problems of helping academics decide which methodology best suits their needs and then create a plan that will allow them to implement this remain largely unaddressed. In this paper, a toolkit is described that attempts to tackle these problems. A two‐part evaluation of the toolkit's impact is then presented, which demonstrates that this approach does enhance design, supports reflection and prompts users to consider the most appropriate, not just the most familiar, approach to evaluation.
Learning preferences towards computerised competitive modes
Authors: Yu F.Y. , Chang L.J. , Liu Y.H. , Chan T.W.
Published: March 2003

Abstract  An online domain‐independent competitive gaming system, called JOYCE, was devised to engage students in drill‐and‐practice exercises. In this paper, theories underpinning the system design are explained. As in the system students are allowed to compete with others in a face‐to‐face situation, and in network situations where an opponent's identify is revealed or concealed, a preliminary study was conducted to examine students' preferences towards different competition modes and satisfaction towards the learning experience. Results supported JOYCE's incorporation into the learning process and the design and development of the system. Based on the obtained data it was suggested that to increase its intrinsic value and to lessen the negative emotional states which is more easily exhibited in a face‐to‐face competition situation anonymity is a promising feature to be included in a competitive learning system. Furthermore, various competition modes should be built into e‐learning environments to satisfy peoples' different learning mode preferences.
The role of local authorities in the integration of ICT in learning
Authors: Bryderup I.M. , Kowalski K.
Published: March 2003

Abstract  How does ICT integration in learning processes depend on the support or lack of support from local authorities? Data from the SITES M2 case studies sheds light on how Danish schools attempted to meet the ‘Act on the Folkeskole’ regarding the integration of ICT in all subjects. This paper draws on the school's perspective based on interviews with the Principals, teachers and ICT coordinators, and the schools' ICT plans and strategies. The schools' perspective is then seen in relationship to the respective municipalities, ICT strategies and national ICT policy in a discussion of the implications of ICT integration on the decentralised Danish folkeskole system.
Ixodes rubicundus nymphs are short‐day diapause‐induced ticks with thermolabile sensitivity and desiccation resistance
Authors: Fourie L. J. , Belozerov V. N. , Needham G. R.
Published: March 2003

Abstract. The Karoo Paralysis tick, Ixodes rubicundus Neumann (Acari: Ixodidae), is a semi‐voltine ixodid that survives stressful environmental conditions using morphogenetic diapause (eggs and engorged nymphs) and desiccation resistance. Both photoperiod and temperature influence diapause induction in the engorged nymph. Ixodes rubicundus nymphs are typical long‐day photoperiodic organisms. The critical photoperiod is ∼ 13.5 h light, 10.5 h dark, and they display a thermolabile response. The period between detachment and apolysis in engorged nymphs is modified by photoperiod; however, apolysis to ecdysis is not affected by photoperiod. Thus, initiation of development, but not the actual process is controlled by photoperiod. Most engorged nymphs delayed metamorphosis when exposed to short‐day regimen (LD 12 : 12 h) after feeding. Nymphs exposed to pre‐ and post‐feeding long‐day regimen (LD 14 : 10 h) developed. Times for 50% of nymphs to apolyse when exposed to photoperiods of LD 14 : 10 h, 13.5 : 10.5 h, 13 : 11 h and 12 : 12 h were 28, 36, 40 and 58 days, respectively. Times for 50% of engorged nymphs to ecdyse ranged from 38 to 40 days after apolysis. Nymphs were sensitive to photoperiodic exposures before, during and after feeding. Nymphs exposed to long day (LD 14 :10 h) before and during feeding, moulted at 20°C; however, most exposed to 10°C followed by 20°C (post‐feeding) went into diapause. Both short‐ (10 : 14 h) and long‐ (14 : 10 h) day exposed engorged nymphs survived 45 days at 0% r.h. (n = 73), but diapause‐destined ticks kept at 13°C lost the least mass (29.5 ± 9.5%, SD), while nondiapause ticks at 23°C lost the most (48.7 ± 8.2%, SD). Termination of diapause and transition to development probably coincides with a definite increase of water vapour uptake by engorged nymphs. Comparatively, I. rubicundus engorged nymphs are more desiccation tolerant than a North‐American counterpart, Amblyomma cajennense (Fabricius) (Acari: Ixodidae), which is also semi‐arid‐ to xeric‐adapted. Diapause conveys important survival attributes that enable engorged I. rubicundus nymphs to inhabit a semi‐arid environment with great temperature extremes, and to synchronize their activity periods with seasons and host utilization patterns.
Pre‐adult mortality in the blowfly Lucilia sericata
Authors: Wall R. , Pitts K. M. , Smith K. E.
Published: March 2003

Abstract. Populations of the blowfly, Lucilia sericata (Meigen) (Diptera: Calliphoridae), have a considerable potential for rapid increase; the lifetime reproductive output of each adult female has been estimated to be between 130 and 172 eggs. Nevertheless, in the field, absolute population densities of this species are relatively low. To account for this difference, the levels of mortality affecting the eggs, feeding and wandering larvae and pupae of L. sericata were assessed in the field and laboratory. Percentage egg hatch was dependent on relative humidity with no egg eclosion at humidities below 50%; there was no significant effect of temperature on egg hatch. On infested sheep, the mean mortality of feeding larvae was 53%, but this ranged widely from 0% to 96%. There was no effect of atmospheric temperature or humidity on the mortality of feeding larvae in vivo. In the laboratory, only 10% of wandering larvae pupariated at 10°C. At above 20°C pupariation was consistently almost 100%. Percentage emergence increased from 0% at 10°C to about 80% between 20 and 30°C. The upper lethal temperature for pupae was approached at 35°C. Analysis of the predation of pupae in the field revealed a weak, but significant curvilinear relationship between temperature and proportionate mortality and a median mortality of 0.49% per 24 h exposure (interquartile range = 5.2%). There was no evidence of density dependence in pupal predation. Overall, it is estimated that pre‐adult mortality accounts for losses of approximately 97% of each generation, but this figure is subject to considerable variation depending on factors such as climate, time of year and host susceptibility.
Malaria transmission risk variations derived from different agricultural practices in an irrigated area of northern Tanzania
Authors: Ijumba J. N. , Mosha F. W. , Lindsay S. W.
Published: March 2003

Abstract Malaria vector Anopheles and other mosquitoes (Diptera: Culicidae) were monitored for 12 months during 1994–95 in villages of Lower Moshi irrigation area (37°20′ E, 3°21′ S; ∼700 m a.s.l.) south of Mount Kilimanjaro in northern Tanzania. Adult mosquito populations were sampled fortnightly by five methods: human bait collection indoors (18.00–06.00 hours) and outdoors (18.00–24.00 hours); from daytime resting‐sites indoors and outdoors; by CDC light‐traps over sleepers. Anopheles densities and rates of survival, anthropophily and malaria infection were compared between three villages representing different agro‐ecosystems: irrigated sugarcane plantation; smallholder rice irrigation scheme, and savannah with subsistence crops. Respective study villages were Mvuleni (population 2200), Chekereni (population 3200) and Kisangasangeni (population ?1000), at least 7 km apart.

Anopheles arabiensis Patton was found to be the principal malaria vector throughout the study area, with An. funestus Giles sensu lato of secondary importance in the sugarcane and savannah villages. Irrigated sugarcane cultivation resulted in water pooling, but this did not produce more vectors. Anopheles arabiensis densities averaged four‐fold higher in the ricefield village, although their human blood‐index was significantly less (48%) than in the sugarcane (68%) or savannah (66%) villages, despite similar proportions of humans and cows (ratio 1 : 1.1–1.4) as the main hosts at all sites. Parous rates, duration of the gonotrophic cycle and survival rates of An. arabiensis were similar in villages of all three agro‐ecosystems.

The potential risk of malaria, based on measurements of vectorial capacity of An. arabiensis and An. funestus combined, was four‐fold higher in the ricefield village than in the sugarcane or savannah villages nearby. However, the more realistic estimate of malaria risk, based on entomological inoculation rates, indicated that exposure to infective vectors was 61–68% less for people in the ricefield village, due to the much lower sporozoite rate in An. arabiensis (ricefield 0.01%, sugarcane 0.1%, savannah 0.12%). This contrast was attributed to better socio‐economic conditions of rice farmers, facilitating relatively more use of antimalarials and bednets for their families. Our findings show that, for a combination of reasons, the malaria challenge is lower for villagers associated with an irrigated rice‐growing scheme (despite greater malaria vector potential), than for adjacent communities with other agro‐ecosystems bringing less socio‐economic benefits to health. This encourages the development of agro‐irrigation schemes in African savannahs, provided that residents have ready access to antimalaria materials (i.e. effective antimalaria drugs and insecticidal bednets) that they may better afford for protection against the greater vectorial capacity of An. arabiensis from the ricefield agro‐ecosystem.
Progressive supranuclear palsy: neuronal and glial cytoskeletal pathology in the higher order processing autonomic nuclei of the lower brainstem
Authors: Rüb U. , Del Tredici K. , Schultz C. , De Vos R. A. I. , Jansen Steur E. N. H. , Arai K. , Braak H.
Published: March 2003

The medial and lateral parabrachial nuclei (MPB, LPB), the gigantocellular reticular nucleus (GI), the raphes magnus (RMG) and raphes obscurus nuclei (ROB), as well as the intermediate reticular zone (IRZ) represent pivotal subordinate brainstem centres, all of which control autonomic functions. In this study, we investigated the occurrence and severity of the neuronal and glial cytoskeletal pathology in these six brainstem nuclei from 17 individuals with clinically diagnosed and neuropathologically confirmed progressive supranuclear palsy (PSP). The association between the severity of the pathology and the duration of the disease was investigated by means of correlation analysis. The brainstem nuclei in all of the PSP cases were affected by the neuronal cytoskeletal pathology, with the IRZ and GI regularly showing severe involvement, the MPB, RMG, and ROB marked involvement, and the LPB mild involvement. In the six nuclear greys studied, glial cells undergo alterations of their cytoskeleton on an irregular basis, whereby diseased oligodendrocytes predominantly presented as coiled bodies and affected astrocytes as thorn‐shaped astrocytes. In all six nuclei, the severity of the neuronal or glial cytoskeletal pathology showed no correlation with the duration of PSP. In view of their functional role, the neuronal pathology in the nuclei studied offers a possible explanation for the autonomic dysfunctions that eventually develop in the course of PSP.
Amino acid budgets in three aphid species using the same host plant
Authors: Sandström J. P. , Moran N. A.
Published: March 2003

Abstract. Nutrient provisioning in aphids depends both on the composition of ingested phloem sap and on the biosynthetic capabilities of the aphid and its intracellular symbionts. Amino acid budgets for three aphid species, Rhopalosiphum padi (L.), Schizaphis graminum (Rondani) and Diuraphis noxia (Mordvilko), were compared on a single host plant species, wheat Triticum aestivum L. Ingestion of amino acids from phloem, elimination of amino acids in honeydew, and the content of amino acids in aphids tissue were measured. From these values, ingestion rates were estimated and compared to honeydew and to estimated composition of aphid proteins. Ingestion rate was lowest in D. noxia due to low growth rate and low honeydew production; intermediate in S. graminum due to higher growth rate and intermediate honeydew production; and highest in R. padi, which had the highest rates for both variables. Both D. noxia and S. graminum induced increases in the amino acid content of ingested phloem. These changes in phloem content, combined with differences in ingestion rates, resulted in large differences among aphids in estimated rates of ingestion of individual amino acids. In honeydew, most essential amino acids were found in low amounts compared with the amounts ingested, especially for methionine and lysine. A few amino acids (arginine, cystine, histidine and tryptophan) were more abundant in honeydew of some aphids, suggesting oversupply. Aphid species differed in the composition of free amino acids in tissue but showed very similar composition in protein, implying similar requirements among the aphids. In R. padi and D. noxia, most essential amino acids were ingested in amounts insufficient for growth, implying dependence on symbiont provisioning. In S. graminum, most amino acids were ingested in amounts apparently sufficient for growth.
Effects of photoperiod and temperature on pupal diapause induction of grape berry moth Lobesia botrana
Authors: Roditakis Nikos E. , Karandinos Michael G.
Published: March 2003

Abstract. The grape berry moth, Lobesia botrana Denn. & Sciff. (Lepidoptera: Tortricidae), one of the most injurious pest of grape berries in Greece, is a multivoltine species that overwinters as diapausing pupae. The effects of several diel and non‐diel photoperiods and of temperature, experienced by eggs and larvae, on pupal diapause induction were investigated. The diapause response curve was of Type I (long day type) and the determining factor was the duration of scotophase (> 11 h), regardless of the duration of photophase. However, at very short (< 4 h) photoperiods, the incidence of diapause was also high. Diapause was positively and significantly correlated with the egg‐larval developmental time, pupal mortality and the duration of the pupal stage. Eggs and larvae reared under LD 12 : 12 h photoperiod and various temperatures (from 12 to 30 °C) produced diapausing pupae (almost 100%), but the duration of the pupal stage (intensity of diapause) increased with increasing temperature. Under continuous darkness, however, the percentage diapause decreased with increasing temperature. Single and double 1‐h light pulses were applied systematically at various times during the scotophase of six diapause‐inducing diel photoperiods. Two photosensitive points in time (called A and B) were revealed, during which illumination resulted in a significant decrease of diapause induction. The decrease was much greater during the first sensitive period (early in scotophase) rather than in the second (late in the scotophase).
Expression studies of key adipogenic transcriptional factors reveal that the anti‐adipogenic properties of retinol in primary cultured human preadipocytes are due to retinol per se
Authors: Machinal‐Quélin F. , Dieudonné M. N. , Leneveu M. C. , Pecquery R. , Castelli D. , Oddos T. , Giudicelli Y.
Published: March 2003

Synopsis

The aim of this study was to investigate the mechanism(s) underlying the antiadipogenic effect of retinol that we recently reported in primary cultured human preadipocytes.

Exposure of human preadipocytes to the potent alcohol dehydrogenase inhibitor, 4‐methyl‐pyrazole, failed to alter the antiadipogenic effect of retinol (3.5 µm), suggesting that the latter effect is due to retinol per se rather than to its oxidation product, retinoic acid (RA).

Moreover, retinol, in contrast to what is generally observed with RA, did not alter the expression of the major adipogenic transcriptional factors PPARγ and C/EBPα but, like RA, reduced transcription of an adipospecific gene controlled in part by C/EBP, the ob gene.

These results indicate that retinol per se inhibits the adipo‐conversion of human preadipocytes and suggest that the mechanisms of this antiadipogenic action implies at least in part inhibition of C/EBP transcriptional activity.
Immune responses in hepatitis C virus infection: The role of dendritic cells
Authors: Fowler Nina L , Torresi Joseph , Jackson David C , Brown Lorena E , Gowans Eric J
Published: March 2003

Cellular immune responses are critical for the clearance of hepatitis C virus. Persistent infection results from a narrow and weak cellular immune response, in direct contrast to the broad, strong response associated with viral clearance in acute infection. The presence of dendritic cells in the liver facilitates presentation of viral antigens to both CD4+ and CD8+ T cell populations. Exploiting the potent antigen presentation capability of dendritic cells for immunotherapy of chronic hepatitis C is attractive; however, infection or transfection of segments or the entire hepatitis C virus genome appears to impair the allostimulation capacity of dendritic cells. If dendritic cell immunotherapy for hepatitis C virus infection is to become a reality, the mechanism behind the defective allostimulatory capacity needs to be deciphered.
Spinal cord involvement of primary central nervous system lymphomas: Histopathological examination of 14 autopsy cases
Authors: Kawasaki Koichi , Wakabayashi Koichi , Koizumi Takayuki , Tanaka Ryuichi , Takahashi Hitoshi
Published: March 2003

The brain and spinal cord from 14 patients with primary central nervous system lymphomas (PCNSL) were systematically examined to determine the distribution and frequency of spinal cord lesions. Spinal cord involvement was observed in four cases (cases 1–4). In cases 1 and 2, tumor cells were spread widely in the brain and extended downward to C4 and Th8 in the spinal parenchyma and to C2 and Th2 in the subarachnoid space (SAS), respectively. In case 3, tumors were found in the cerebrum but not in the cerebellum or brainstem. In the spinal cord there was massive subarachnoid involvement from C2 to L4 and localized parenchymal invasion from Th8 to L4. In case 4, tumors were found in the parenchyma from brainstem to Th2 and in the SAS all around the cord. Diffuse subarachnoid proliferation with parenchymal invasion via the Virchow–Robin space was found in the spinal cord. The route of tumor spread in cases 1 and 2 was considered to be intraparenchymal invasion from the medulla oblongata to the spinal cord because the cord lesions had continuity with the brain lesions. In contrast, the cord lesions in cases 3 and 4 were considered to be spread via the CSF because the lesions had no continuity with the brain lesions in case 3, and spinal SAS involvement was more extensive than the parenchymal lesions in both cases. These findings suggest that spinal cord involvement is not a rare event in PCNSL and that there are two routes of spread: direct invasion from the medulla oblongata and dissemination via the CSF.
Structure of the type III secretion and substrate‐binding domain of Yersinia YopH phosphatase
Authors: Smith Craig L. , Khandelwal Purnima , Keliikuli Kai , Zuiderweg Erik R. P. , Saper Mark A.
Published: March 2003

Pathogenic strains of Yersinia deploy a type III secretion system to inject the potent tyrosine phosphatase YopH into host cells, where it dephosphorylates focal adhesion‐associated substrates. The amino‐terminal, non‐catalytic domain of YopH is bifunctional; it is essential for the secretion and binding of the specific chaperone SycH, but also targets the catalytic domain to substrates in the infected cell. We describe the 2.2  Å resolution crystal structure of residues 1–129 of YopH from Yersinia pseudotuberculosis. The amino‐terminal α‐helix (2–17), comprising the secretion signal, and β‐strand (24–28) of one molecule exchange with another molecule to form a domain‐swapped dimer. Nuclear magnetic resonance (NMR) and gel filtration experiments demonstrated that YopH(1–129) could exist as a monomer and/or a dimer in solution. The topology of the dimer and the dynamics of a monomeric form in solution observed by NMR imply that YopH has the propensity to unfold partially. The dimer is probably not important physiologically, but may mimic how SycH binds to the exposed non‐polar surfaces of a partially unfolded YopH. Phosphopeptide‐induced perturbations in NMR chemical shifts define a substrate‐binding surface on YopH(1–129) that includes residues previously shown by mutagenesis to be essential for YopH function.
Commercial dry dog food in the north central United States is not contaminated by Dermatophagoides house dust mites
Authors: Deboer Douglas J. , Schreiner Terri A.
Published: March 2003

Contamination of home‐stored cereal grain food products with Dermatophagoides spp. house dust mites (HDM) was reported recently, along with anaphylaxis after consumption of these foods by dust mite‐allergic people. We hypothesized that commercial dry dog food could become similarly contaminated, particularly if stored improperly, and could eventually contribute to allergic signs in dogs. Newly purchased bags of dry dog food (n = 30), from a variety of sources and manufacturers, and client samples of dry dog food (n = 50), stored under a variety of conditions, were obtained. Food samples were extracted in aqueous buffer, and extracts were assayed using ELISA for Dermatophagoides group II (Der II) allergen, as a marker for the presence of HDM. Der II allergen was not detected in any of the 30 newly purchased or 50 stored samples tested. Positive control samples consisting of house dust or dog food mixed with house dust, similarly extracted, and Dermatophagoides commercial allergen extract were positive for Der II in the same assay. We could find no evidence of HDM contamination in newly purchased or stored commercial dry dog food in the north central United States.
Congenital hypotrichosis in a Percheron draught horse
Authors: Valentine Beth A. , Hedstrom Olaf R. , Miller William H. , Scott Danny W. , Mathies Suzette
Published: March 2003

A blue roan Percheron foal was born with poorly circumscribed patchy alopecia of the trunk and legs. Teeth and hoof development were normal. Alopecia was progressive, becoming almost complete by 1 year of age. Histopathological findings in a skin biopsy obtained at 7 months of age were consistent with severe follicular hypoplasia. Sebaceous glands, epitrichial sweat glands and arrector pilae muscles were normal. The horse is alive and otherwise well at 6 years of age, although adult stature is considered small for this breed. The clinical history and histopathological findings are most consistent with a form of congenital hypotrichosis.
The mast cell in wound healing
Authors: Noli Chiara , Miolo Alda
Published: March 2003

This review describes the role of the mast cell in the pathobiology of skin healing. After illustrating its main morphofunctional characteristics, with special reference to the dog and cat, we consider the involvement of the mast cell in the various phases of skin repair. With the aid of a wide array of newly formed or preformed mediators released by degranulation, the activated mast cell controls the key events of the healing phases: triggering and modulation of the inflammatory stage, proliferation of connective cellular elements and final remodelling of the newly formed connective tissue matrix. The importance of the mast cell in regulating healing processes is also demonstrated by the fact that a surplus or deficit of degranulated biological mediators causes impaired repair, with the formation of exuberant granulation tissue (e.g. keloids and hypertrophic scars), delayed closure (dehiscence) and chronicity of the inflammatory stage.
An ankyrin repeat‐containing protein plays a role in both disease resistance and antioxidation metabolism
Authors: Yan Juqiang , Wang Jing , Zhang Hong
Published: March 2003

The Arabidopsis ankyrin repeat‐containing protein AKR2 was identified as a GF14λ‐interacting protein in a yeast two‐hybrid screening (GF14λ is a 14‐3‐3 protein). Reduced expression of AKR2 by using the antisense technique results in small necrotic areas in leaves accompanied by higher production of H2O2, similar to the hypersensitive response to pathogen infection in plant disease resistance. Transcripts of genes encoding pathogen‐induced protein PR‐1 (pathogen‐related protein 1) and stress‐responsive protein GST6 (glutathione S‐transferase 6) are increased in antisense plants. The resistance to a bacterial pathogen infection was also increased by at least 10‐fold in antisense plants. AKR2 also interacts with another GF14λ‐interacting protein, the ascorbate peroxidase 3 that scavenges H2O2 in plant cells. These data suggest that AKR2 may be a negative regulator of PR‐1 expression, and is probably involved in the regulation of antioxidation metabolism that is shared by both disease resistance and stress responses.
Cultivated tomato has defects in both S‐RNase and HT genes required for stylar function of self‐incompatibility
Authors: Kondo Katsuhiko , Yamamoto Mayu , Matton Daniel P. , Sato Takanori , Hirai Masashi , Norioka Shigemi , Hattori Tsukaho , Kowyama Yasuo
Published: March 2003

Cultivated tomato (Lycopersicon esculentum), a self‐compatible species, evolved from self‐incompatible (SI) species in the genus Lycopersicon following a breakdown of the self‐incompatibility system. In order to elucidate the molecular basis of this breakdown in L. esculentum, we first analysed the stylar proteins with an in‐gel assay for ribonuclease activity and 2D‐PAGE. No S‐RNase protein or its activity was detected in the style of L. esculentum. We then introduced the S6‐RNase gene from an SI relative, L. peruvianum, into L. esculentum. However, the styles of transgenic plants expressing S6‐RNase at levels comparable to those found in the L. peruvianum style were unable to reject self‐pollen and L. peruvianum pollen in an allele‐specific manner. This indicated that defect in the S‐RNase expression was not the sole reason for the loss of self‐incompatibility in tomato. The asparagine‐rich HT protein, originally identified from the style of Nicotiana alata, is the other stylar factor involved in self‐incompatibility reaction. We cloned and sequenced two distinct genes encoding HT‐A and HT‐B proteins from L. peruvianum (LpHT‐A and LpHT‐B) and L. esculentum (LeHT‐A and LeHT‐B). A frame shift mutation in the coding sequence of LeHT‐A and a stop codon in the ORF of LeHT‐B were found, and no LeHT‐B transcript was detected in the style of L. esculentum. The results suggest that the breakdown of self‐incompatibility in cultivated tomato is associated with loss‐of‐function mutations in both S‐RNase and HT genes.
Activation of AtMEK1, an Arabidopsis mitogen‐activated protein kinase kinase, in vitro and in vivo: analysis of active mutants expressed in E. coli and generation of the active form in stress response in seedlings
Authors: Matsuoka Daisuke , Nanmori Takashi , Sato Ken‐ichi , Fukami Yasuo , Kikkawa Ushio , Yasuda Takeshi
Published: March 2003

The mitogen‐activated protein kinase (MAPK) cascade, consisting of MAPK, MAPK kinase (MAPKK) and MAPK kinase kinase (MAPKKK), is the signaling system that relays various external signals, including mitogens and stresses in eukaryotes. MAPKK is activated by phosphorylation in the consensus motif, SXXXS/T, in animals, but the regulation mechanism for the plant MAPKK by phosphorylation, having the putative phosphorylation motif of S/TXXXXXS/T, is not yet fully clarified. Here we constructed a series of mutants of AtMEK1, an Arabidopsis MAPKK, having the sequence T218‐X‐S220‐X‐X‐X‐S224 that fits both of the plant‐ and animal‐type motifs. We show that the two double‐mutant proteins replacing Thr‐218/Ser‐224 and Ser‐220/Ser‐224 by Glu expressed in Escherichia coli show a constitutive activity to phosphorylate the Thr and Tyr residues of the kinase‐negative mutant of an Arabidopsis MAPK, named ATMPK4, in vitro. The mutation analysis of AtMEK1 replacing Thr‐218 and Ser‐220 to Ala suggested that Thr‐218 is autophosphorylated by the enzyme. The wild‐type ATMPK4 was also phosphorylated by the active mutants of AtMEK1 and showed a high protein kinase activity toward myelin basic proteins. In contrast, ATMPK3, another Arabidopsis MAPK, was a poor substrate of this plant MAPKK, indicating that AtMEK1 has a substrate specificity preferring ATMPK4 to ATMPK3, at least in vitro. Furthermore, AtMEK1 immunoprecipitated from Arabidopsis seedlings stimulated with wounding, cold, drought, and high salt showed an elevated protein kinase activity toward the kinase‐negative ATMPK4, while the amounts of the AtMEK1 protein did not change significantly. These data indicate that the AtMEK1 becomes an active form through phosphorylation and activates its downstream target ATMPK4 in stress response in Arabidopsis.