bluuebunny/crossref_metadata_2025 huggingface dataset:
The multiple spawning pattern of weakfish in the Chesapeake Bay and Middle Atlantic Bight
Authors: Lowerre‐Barbieri S. K. , Chittenden M. E. , Barbieri L. R.
Published: April 2005

Weakfish Cynoscion regalis were collected from commercial fisheries in the Chesapeake Bay and the Middle Atlantic Bight (n=4380) during 1989–1992 and their reproductive biology assessed using the gonadosomatic index, macroscopic gonad stages, oocyte diameter distributions, microscopic whole oocyte analysis and histology. Sex ratios were approximately 3:1, females to males, in 1990–1992. Most fish (90%) attained sexual maturity by age 1 and at a small size. Estimated mean length at first maturity was: 164mm total length (TL) for males, and 170 mm TL for females. Weakfish spawn within the Chesapeake Bay, as far north as the Virginia/ Maryland border. Although spawning occurred during May–August and gonad development and initiation of spawning was synchronous, cessation of spawning was asynchronous. There was no indication that older fish exhibited a more extended spawning season than younger fish. Weakfish are multiple spawners with indeterminate fecundity. Oocyte development is asynchronous with oocytes of all stages being present in developed ovaries. Because of the complex and dynamic weakfish ovarian cycle, typical methods of assessing reproduction, such as the GSI and macroscopic gonad stages, are inadequate for this species if not used in conjunction with more detailed methods such as histology.
Final oocyte maturation in vivo and in vitro in marine fishes with pelagic eggs; yolk protein hydrolysis and free amino acid content
Authors: Thorsen A. , Fyhn H. J.
Published: April 2005

The role of free amino acids (FAA) in oocyte hydration during final maturation has been studied in plaice Pleuronectes platessa and lemon sole Microstomus kitt by in vivo and in vitro measurements. In vitro final maturation was initiated by the administration of human chorionic gonadotropin on large vitellogenic oocytes. The eggs produced in vitro had the same fraction of their total amino acid pool present in the free form as the in vivo hydrated eggs, regardless of whether FAA had been present in the incubation medium or not. The FAA pool in the mature egg was increased 10–15 times that of the oocyte, and the two FAA pool profiles differed strongly. The FAA profiles of the egg groups (intra‐ as well as interspecific) were almost identical except that the taurine content was lower in eggs in vitro. A major protein band of about 100 kDa was present on SDS electrophoretic gels of oocytes but missing on gels of hydrated eggs. This protein, presumably a lipovitellin, is the most likely origin of the egg FAA pool. We suggest that marine fishes with pelagic eggs share a common mechanism for oocyte hydration whereby partial hydrolysis of specific yolk proteins to FAA creates a major part of the osmotic potential needed for the water influx.
Monthly variation in sperm motility in common carp assessed using computer‐assisted sperm analysis (CASA)
Authors: Christ S. A. , Toth G. P. , McCarthy H. W. , Torsella J. A. , Smith M. K.
Published: April 2005

Sperm motility variables from the milt of the common carp Cyprinus carpio were assessed using a computer‐assisted sperm analysis (CASA) system across several months (March‐August 1992) known to encompass the natural spawning period. Two‐year‐old pond‐raised males obtained each month were primed with an exogeneous hormone injection of carp pituitary extract and stripped of milt 18–24h later. The milt was diluted, activated and videotaped using a high‐speed (200 Hz) videocamera and recorder. Videotaped samples were subsequently analysed using the CellTrak/S CASA system (Motion Analysis Corp.) for percent motility, curvilinear and straight‐line velocity. In addition to assessing changes in motility parameters across several months, a comparison was made between two predilution/ activation media combinations (homologous seminal plasma/NaCl+HEPES v. 2‐h incubation in 200 mM KCl+Tris/Tris). The percentage of motile cells assessed immediately after activation was significantly greater in the summer months (May, June, July) when compared to a spring sampling point (March); when assessed 1 min after activation, cells prediluted in seminal plasma maintained a higher percentage of motility than those prediluted in KC1. Curvilinear and straight‐line velocities exhibited a slight seasonal trend; variations in response to the predilution treatments were observed with these measurements. Sperm count gradually increased through April and May (9–63 × 109 to 2–38 × lO10ml– 1 milt), declined in June and July (to 1–83 × lO10ml– 1 milt), and was followed by a steep increase in August (2–74 × 1010 ml– 1 milt). Mean seminal plasma osmolality remained relatively constant (250–265 mOsmol kg – 1) throughout the sampling period.
The emetic reflex in African walking catfish develops with age
Authors: Sims D. W. , Andrews P. L. R.
Published: April 2005

This opportunistic observational study showed that following feeding, subadult catfish, Clorias gariepinus (>3 months old; n=37) were sensitive to the disturbance caused by removing two fish for weighing. This initiated intense and prolonged vomiting (oral expulsion of upper gut contents). The main emetic response occurred within a few minutes after fish removal, although commercial grade food pellets were still being vomited 50 to 100 min later. The magnitude of the vomiting response was relatively greater after consumption of larger meals, however, nothan 44% of a meal was ever vomited. Juvenile catfish (<3 months; n=8) were also sensitive to disturbance as indicated by vomiting. The emetic response in these younger fish wasas pronounced as that of the subadults even when given meals of similar relative size (approx. 2.4% wet body weight). No emesis was observed in post‐hatching catfish (<3 weeksd; n=7) after feeding and following a similar disturbance. This suggests the emetic reflex may not operate in post‐hatching catfish in reaction to a stimulus that in subadults and juveniles produced a graded, weight‐dependent vomiting response. This raises the question of whether this difference represents neuronal pathway development or learning of the reflex.
Parasites as indicators of individual feeding specialization in Arctic charr during winter in northern Norway
Authors: Knudsen R. , Klemetsen A. , Staldvik F.
Published: April 2005

The relationship between infection with the food‐transmitted parasites Diphyllobothrium dendriticum, D. ditremum (Cestoda) and Cystidicola farionis (Nematoda) and prey selection was studied in individual Arctic charr from Lake Takvatn, northern Norway. There was no correlation between parasites transmitted throughout prey organisms from benthic habitats (amphipods) and pelagic habitats (copepods). A strong relationship between infection with a parasite species and the corresponding intermediate host from the stomach content of individual charr, indicated an individual feeding specialization. Independent of size, charr specialized on the intermediate hosts of all three parasite species. Some charr maintained this specialization on specific prey items throughout the winter period. These parasite species are considered to be useful indicators of past prey selection.
Seasonal occurrence, topographical distribution and transmission of Gyrodactylus callanatis (Monogenea) infecting juvenile Atlantic cod in the Oslo Fjord, Norway
Authors: Appleby C.
Published: April 2005

The seasonal occurrence and topographi0cal distribution of Gyrodactylus callanatis on three year‐classes of juvenile Atlantic cod Gadus morhua, has been studied in the Oslo Fjord, Norway over a 2‐year period. Both prevalence and abundance increased in spring and peaked in summer on the 1992 year‐class and decreased in autumn. The highest intensities recorded in the study were observed on the 1992 year‐class in June, with some fish harbouring more than 500 worms each. On the 1993 year‐class, prevalence increased throughout the year, until it reached 100% in November; abundance, however, did not differ significantly between monthly samples, but intensities on individual fish were highest in June. The 0 + cod are probably infected when they immigrate to the nursery grounds in autumn and mingle with infected 1 + cod. About 74% of the worms infected the gill arches, oral cavity and pharynx, while 26% infected the body, head and fins. There was a significantly higher percentage of worms on the latter sites at intensities of less than 20 and more than 100 worms per fish. This is possibly related to the mode of transmission in G. callariatis. The initial infection sites are presumably the fins and head, and the most important route of transmission of G. callanatis is believed to be via the substrate. Other routes of transmission are also discussed.
Genetic polymorphism in the intron of the growth hormone gene of the bleak
Authors: Schlee P. , Fuchs H. , Blusch J. , Werner T. , Rottmann O. , Stein H.
Published: April 2005

Comparison of nucleotide sequences of the growth hormone gene of two populations of bleak from the Main Donau Rivers, Southern Germany, revealed an A/T point mutation resulting in an AluI restriction fragment length polymorphism. The frequencies of alleles T and A are 0–95/0–05 in the Donau and 0–62/0–38 in the Main.
Evidence from mtDNA RFLP analysis for the introduction of Fundulus heteroclitus to southwestern Spain
Authors: FernÁndez‐Pedrosa V. , Latorre A. , GonzÁlez A.
Published: April 2005

Restriction analysis of mitochondrial DNA confirmed the taxonomic status of a southwestern Iberian Peninsula population of Fundulus heteroclitus and its probable origin in North America.
Indomethacin‐induced ileitis is associated with tensiometric, vascular and oxidative changes in the experimental rat model
Authors: Piepoli A. L. , De Salvatore G. , De Salvia M. A. , Mitolo C. I. , Siro‐Brigiani G. , Marzullo A. , Grattagliano I. , Mitolo‐Chieppa D. , Palasciano G. , Portincasa P.
Published: April 2005

Background  Indomethacin‐induced enteritis is a model of inflammatory bowel disease.

Materials and methods  To further characterize this model, rats received two injections of indomethacin (7·5 mg kg−1) 24 h apart and histological damage of intestinal mucosa, oxidative stress, alterations of intestinal motility and mesenteric vascular bed (MVB) reactivity were investigated after 5 days.

Results  The results show that indomethacin caused several histological and functional changes at the ileal level. In particular, response to carbachol as well as the nonadrenergic‐noncholinergic inhibitory response to electrical field stimulation (EFS) was lower in the treated than control rats. Moreover, nitric oxide (NO)‐component of the inhibitory response was higher in the treated than control rats. Mesenteric vessels preparations from the treated rats showed increased noradrenaline (NA)‐induced perfusion pressure, whereas relaxant responses to acetylcholine, although not significantly reduced in the treated rats, had a higher nitrergic component. This finding suggests that vascular dysfunction may contribute to chronic inflammation. Indomethacin injection also determined acute and severe oxidative stress in ileum mucosa.

Conclusions  In conclusion, our study contributes to further characterize the rat model of indomethacin‐induced enteritis and suggests that it is suitable for drug screening in rats, as this model can be obtained in a very short period and is simple and reproducible.
Does C‐reactive protein identify a subclinical metabolic disease in healthy subjects?
Authors: Bo S. , Gambino R. , Uberti B. , Mangiameli M. P. , Colosso G. , Repetti E. , Gentile L. , Cassader M. , Pagano G. F.
Published: April 2005

Background  Highly sensitive C‐reactive protein (hs‐CRP) levels are significant predictors of subsequent diabetes and metabolic syndrome (MS). Owing the strong correlations between components of the MS and obesity with hs‐CRP levels, previous studies about the associations of hs‐CRP with insulin resistance might have been confounded by the inclusion of overweight or dysmetabolic subjects.

Design  Our aim was to evaluate the associations between hs‐CRP levels and fasting insulin and insulin resistance (evaluated by the Homeostasis Model Assessment: HOMA IR) in a subgroup of subjects with normal body mass index (BMI) and without any metabolic abnormalities. Out of a cohort of 1658 middle‐aged subjects, representative of the local sanitary districts of the province of Asti (north‐western Italy) enrolled for metabolic screening: 241 (14·5%) showed normal BMI, glucose tolerance, blood pressure and waist values and no dyslipidaemia.

Results  In this subgroup of subjects, those with hs‐CRP levels ≥ 3 mg L−1 showed significantly higher median insulin and HOMA‐IR values (respectively: 20·4 vs. 6·0 pmol L−1, and 0·8 vs. 0·2 µU mL−1× mmol L−1). In a multiple regression model, insulin and insulin resistance remained significantly and independently related to hs‐CRP levels, after adjustments for age, sex, BMI, waist, alcohol consumption, level of physical activity and smoking habits. Very few individuals within lower fasting insulin quartiles showed hs‐CRP values ≥ 3 mg L−1 when compared with approximately 60% of those within the highest quartile.

Conclusions  The novel finding is that a state of low‐grade systemic inflammation is present in normal BMI subjects who show subclinical insulin resistance but no other metabolic abnormalities.
Cancer immunotherapy by fusions of dendritic and tumour cells and rh‐IL‐12
Authors: Homma S. , Kikuchi T. , Ishiji N. , Ochiai K. , Takeyama H. , Saotome H. , Sagawa Y. , Hara E. , Kufe D. , Ryan J. L. , Ohno T. , Toda G.
Published: April 2005

Background  Vaccination with fusion cells (FCs) comprising dendritic cells and tumour cells as well as administration of interleukin‐12 (IL‐12) showed a significant therapeutic effect against established tumours in mouse experimental models. We conducted immunotherapy against various malignant tumours using the FCs and rhIL‐12, and investigated the safety and efficacy of the therapy.

Materials and methods  Patients’ DCs were mixed with autologous irradiated tumour cells and treated with 50% polyethylene glycol to generate FCs. The FCs were inoculated intradermally, and then 30 ng kg−1 of rhIL‐12 was injected at the same sites 2 and 6 days later. This process was carried out as one cycle, and three of these cycles were repeated at 1‐week intervals to comprise one course. After completing the course, its safety and therapeutic effects were estimated.

Results  The most frequently observed adverse event was fever, observed in 26% of patients in the first cycle. Decrease in white blood cell and an increase in serum ALT were observed in 28% and 25%, respectively. Three out of 12 patients with a malignant brain tumour (25%) achieved a partial response (PR), but other patients with a malignant tumour showed no regression of their tumours. Thirteen out of 16 patients with a brain tumour (81%) showed cutaneous delayed hypersensitivity responses. However, only one of 16 patients (6%) with a malignant tumour other than a brain tumour developed such responses.

Conclusions  Immunotherapy using a FC vaccine and rhIL‐12 induced no serious adverse reactions, and provided good therapeutic responses in some of the patients with a brain tumour.
A new statistical tool to predict phenology under climate change scenarios
Authors: Gienapp Phillip , Hemerik Lia , Visser Marcel E.
Published: April 2005

Climate change will likely affect the phenology of trophic levels differently and thereby disrupt the phenological synchrony between predators and prey. To predict this disruption of the synchrony under different climate change scenarios, good descriptive models for the phenology of the different species are necessary. Many phenological models are based on regressing the observed phenological event against temperatures measured over a fixed period. This is problematic, especially when used for future predictions because the paradoxical situation could arise that the phenological event occurs before the period over which temperature is measured. Such models are unable to predict population variation in phenology. Here, we propose a ‘proportional hazards model’ to describe phenology and illustrate it with an example from breeding time in birds. This type of model circumvents the above‐mentioned problems and is generally applicable for describing phenology, which is essential when assessing the ecological impact of climate change.
The response of Alaskan arctic tundra to experimental warming: differences between short‐ and long‐term responses
Authors: Hollister Robert D. , Webber Patrick J. , Tweedie Craig E.
Published: April 2005

Global climate models predict continued rapid warming for most of the Arctic throughout the next century. To further understand the response of arctic tundra to climate warming, four sites in northern Alaska were warmed for five to seven consecutive growing seasons using open‐top chambers. Sites were located in dry heath and wet meadow communities near Barrow (71°18′N, 156°40′W) and Atqasuk (70°29′N, 157°25′W). Change in plant community composition was measured using a point frame method. During the period of observation, species richness declined in control plots by up to 2.7 species plot−1. Responses to warming varied by site but similar trends included increased canopy height (−0.1 to 2.3 cm) and relative cover of standing dead plant matter (1.5–6.0%) and graminoids (1.8–5.8%) and decreased species diversity (0.1–1.7 species plot−1) and relative cover of lichens (0.2–9.1%) and bryophytes (1.4–4.6%) (parentheses enclose the range of average values for the sites). The response to warming was separated into an initial short‐term response assessed after two growing seasons of warming and a secondary longer‐term response assessed after an additional three to five growing seasons of warming. The initial responses to warming were similar in the four sites, while the secondary responses varied by site. The response to warming was greater at Barrow than Atqasuk because of a greater initial response at Barrow. However, the long‐term response to warming was projected to be greater at Atqasuk because of a greater secondary response at Atqasuk. These findings show that predictions of vegetation change due to climate warming based on manipulative experiments will differ depending on both the duration and plant community on which the study focuses.
Vegetation responses in Alaskan arctic tundra after 8 years of a summer warming and winter snow manipulation experiment
Authors: Wahren C.‐H. A. , Walker M. D. , Bret‐Harte M. S.
Published: April 2005

We used snow fences and small (1 m2) open‐topped fiberglass chambers (OTCs) to study the effects of changes in winter snow cover and summer air temperatures on arctic tundra. In 1994, two 60 m long, 2.8 m high snow fences, one in moist and the other in dry tundra, were erected at Toolik Lake, Alaska. OTCs paired with unwarmed plots, were placed along each experimental snow gradient and in control areas adjacent to the snowdrifts. After 8 years, the vegetation of the two sites, including that in control plots, had changed significantly. At both sites, the cover of shrubs, live vegetation, and litter, together with canopy height, had all increased, while lichen cover and diversity had decreased. At the moist site, bryophytes decreased in cover, while an increase in graminoids was almost entirely because of the response of the sedgeEriophorum vaginatum. These community changes were consistent with results found in studies of responses to warming and increased nutrient availability in the Arctic. However, during the time period of the experiment, summer temperature did not increase, but summer precipitation increased by 28%. The snow addition treatment affected species abundance, canopy height, and diversity, whereas the summer warming treatment had few measurable effects on vegetation. The interannual temperature fluctuation was considerably larger than the temperature increases within OTCs (<2°C), however. Snow addition also had a greater effect on microclimate by insulating vegetation from winter wind and temperature extremes, modifying winter soil temperatures, and increasing spring run‐off. Most increases in shrub cover and canopy height occurred in the medium snow‐depth zone (0.5–2 m) of the moist site, and the medium to deep snow‐depth zone (2–3 m) of the dry site. At the moist tundra site, deciduous shrubs, particularlyBetula nana, increased in cover, while evergreen shrubs decreased. These differential responses were likely because of the larger production to biomass ratio in deciduous shrubs, combined with their more flexible growth response under changing environmental conditions. At the dry site, where deciduous shrubs were a minor part of the vegetation, evergreen shrubs increased in both cover and canopy height. These changes in abundance of functional groups are expected to affect most ecological processes, particularly the rate of litter decomposition, nutrient cycling, and both soil carbon and nitrogen pools. Also, changes in canopy structure, associated with increases in shrub abundance, are expected to alter the summer energy balance by increasing net radiation and evapotranspiration, thus altering soil moisture regimes.
A generalized, bioclimatic index to predict foliar phenology in response to climate
Authors: Jolly William M. , Nemani Ramakrishna , Running Steven W.
Published: April 2005

The phenological state of vegetation significantly affects exchanges of heat, mass, and momentum between the Earth's surface and the atmosphere. Although current patterns can be estimated from satellites, we lack the ability to predict future trends in response to climate change. We searched the literature for a common set of variables that might be combined into an index to quantify the greenness of vegetation throughout the year. We selected as variables: daylength (photoperiod), evaporative demand (vapor pressure deficit), and suboptimal (minimum) temperatures. For each variable we set threshold limits, within which the relative phenological performance of the vegetation was assumed to vary from inactive (0) to unconstrained (1). A combined Growing Season Index (GSI) was derived as the product of the three indices. Ten‐day mean GSI values for nine widely dispersed ecosystems showed good agreement (r>0.8) with the satellite‐derived Normalized Difference Vegetation Index (NDVI). We also tested the model at a temperate deciduous forest by comparing model estimates with average field observations of leaf flush and leaf coloration. The mean absolute error of predictions at this site was 3 days for average leaf flush dates and 2 days for leaf coloration dates. Finally, we used this model to produce a global map that distinguishes major differences in regional phenological controls. The model appears sufficiently robust to reconstruct historical variation as well as to forecast future phenological responses to changing climatic conditions.
Gross primary production is stimulated for three Populus species grown under free‐air CO2 enrichment from planting through canopy closure
Authors: Wittig Victoria E. , Bernacchi Carl J. , Zhu Xin‐Guang , Calfapietra Carlo , Ceulemans Reinhart , Deangelis Paolo , Gielen Birgit , Miglietta Franco , Morgan Patrick B. , Long Stephen P.
Published: April 2005

How forests will respond to rising [CO2] in the long term is uncertain, most studies having involved juvenile trees in chambers prior to canopy closure. Poplar free‐air CO2 enrichment (Viterbo, Italy) is one of the first experiments to grow a forest from planting through canopy closure to coppice, entirely under open‐air conditions using free‐air CO2 enrichment technology. Three Populus species: P. alba, P. nigra and P. x euramericana, were grown in three blocks, each containing one control and one treatment plot in which CO2 was elevated to the expected 2050 concentration of 550 ppm. The objective of this study was to estimate gross primary production (GPP) from recorded leaf photosynthetic properties, leaf area index (LAI) and meteorological conditions over the complete 3‐year rotation cycle. From the meteorological conditions recorded at 30 min intervals and biweekly measurements of LAI, the microclimate of leaves within the plots was estimated with a radiation transfer and energy balance model. This information was in turn used as input into a canopy microclimate model to determine light and temperature of different leaf classes at 30 min intervals which in turn was used with the steady‐state biochemical model of leaf photosynthesis to compute CO2 uptake by the different leaf classes. The parameters of these models were derived from measurements made at regular intervals throughout the coppice cycle. The photosynthetic rates for different leaf classes were summed to obtain canopy photosynthesis, i.e. GPP. The model was run for each species in each plot, so that differences in GPP between species and treatments could be tested statistically. Significant stimulation of GPP driven by elevated [CO2] occurred in all 3 years, and was greatest in the first year (223–251%), but markedly lower in the second (19–24%) and third years (5–19%). Increase in GPP in elevated relative to control plots was highest for P. nigra in 1999 and for P. x euramericana in 2000 and 2001, although in 1999 P. alba had a higher GPP than P. x euramericana. Our analysis attributed the decline in stimulation to canopy closure and not photosynthetic acclimation. Over the 3‐year rotation cycle from planting to harvest, the cumulative GPP was 4500, 4960 and 4010 g C m−2 for P. alba, P. nigra and P. x euramericana, respectively, in current [CO2] and 5260, 5800 and 5000 g C m−2 in the elevated [CO2] treatments. The relative changes were consistent with independent measurements of net primary production, determined independently from biomass increments and turnover.
Elevated atmospheric CO2 effects on biomass production and soil carbon in conventional and conservation cropping systems
Authors: Prior Stephen A. , Brett Runion G. , Rogers Hugo H. , Allen Torbert H. , Wayne Reeves D.
Published: April 2005

Increasing atmospheric CO2 concentration has led to concerns about potential effects on production agriculture as well as agriculture's role in sequestering C. In the fall of 1997, a study was initiated to compare the response of two crop management systems (conventional and conservation) to elevated CO2. The study used a split‐plot design replicated three times with two management systems as main plots and two CO2 levels (ambient=375 μL L−1 and elevated CO2=683 μL L−1) as split‐plots using open‐top chambers on a Decatur silt loam (clayey, kaolinitic, thermic Rhodic Paleudults). The conventional system was a grain sorghum (Sorghum bicolor (L.) Moench.) and soybean (Glycine max (L.) Merr.) rotation with winter fallow and spring tillage practices. In the conservation system, sorghum and soybean were rotated and three cover crops were used (crimson clover (Trifolium incarnatum L.), sunn hemp (Crotalaria juncea L.), and wheat (Triticum aestivum L.)) under no‐tillage practices. The effect of management on soil C and biomass responses over two cropping cycles (4 years) were evaluated. In the conservation system, cover crop residue (clover, sunn hemp, and wheat) was increased by elevated CO2, but CO2 effects on weed residue were variable in the conventional system. Elevated CO2 had a greater effect on increasing soybean residue as compared with sorghum, and grain yield increases were greater for soybean followed by wheat and sorghum. Differences in sorghum and soybean residue production within the different management systems were small and variable. Cumulative residue inputs were increased by elevated CO2 and conservation management. Greater inputs resulted in a substantial increase in soil C concentration at the 0–5 cm depth increment in the conservation system under CO2‐enriched conditions. Smaller shifts in soil C were noted at greater depths (5–10 and 15–30 cm) because of management or CO2 level. Results suggest that with conservation management in an elevated CO2 environment, greater residue amounts could increase soil C storage as well as increase ground cover.
Decomposition of soybean grown under elevated concentrations of CO2 and O3
Authors: Booker Fitzgerald L. , Prior Stephen A. , Torbert H. Allen , Fiscus Edwin L. , Pursley Walter A. , Hu Shuijin
Published: April 2005

A critical global climate change issue is how increasing concentrations of atmospheric CO2 and ground‐level O3 will affect agricultural productivity. This includes effects on decomposition of residues left in the field and availability of mineral nutrients to subsequent crops. To address questions about decomposition processes, a 2‐year experiment was conducted to determine the chemistry and decomposition rate of aboveground residues of soybean (Glycine max (L.) Merr.) grown under reciprocal combinations of low and high concentrations of CO2 and O3 in open‐top field chambers. The CO2 treatments were ambient (370 μmol mol−1) and elevated (714 μmol mol−1) levels (daytime 12 h averages). Ozone treatments were charcoal‐filtered air (21 nmol mol−1) and nonfiltered air plus 1.5 times ambient O3 (74 nmol mol−1) 12 h day−1. Elevated CO2 increased aboveground postharvest residue production by 28–56% while elevated O3 suppressed it by 15–46%. In combination, inhibitory effects of added O3 on biomass production were largely negated by elevated CO2. Plant residue chemistry was generally unaffected by elevated CO2, except for an increase in leaf residue lignin concentration. Leaf residues from the elevated O3 treatments had lower concentrations of nonstructural carbohydrates, but higher N, fiber, and lignin levels. Chemical composition of petiole, stem, and pod husk residues was only marginally affected by the elevated gas treatments. Treatment effects on plant biomass production, however, influenced the content of chemical constituents on an areal basis. Elevated CO2 increased the mass per square meter of nonstructural carbohydrates, phenolics, N, cellulose, and lignin by 24–46%. Elevated O3 decreased the mass per square meter of these constituents by 30–48%, while elevated CO2 largely ameliorated the added O3 effect. Carbon mineralization rates of component residues from the elevated gas treatments were not significantly different from the control. However, N immobilization increased in soils containing petiole and stem residues from the elevated CO2, O3, and combined gas treatments. Mass loss of decomposing leaf residue from the added O3 and combined gas treatments was 48% less than the control treatment after 20 weeks, while differences in decomposition of petiole, stem, and husk residues among treatments were minor. Decreased decomposition of leaf residues was correlated with lower starch and higher lignin levels. However, leaf residues only comprised about 20% of the total residue biomass assayed so treatment effects on mass loss of total aboveground residues were relatively small. The primary influence of elevated atmospheric CO2 and O3 concentrations on decomposition processes is apt to arise from effects on residue mass input, which is increased by elevated CO2 and suppressed by O3.
Stripping Bacillus: ComK auto‐stimulation is responsible for the bistable response in competence development
Authors: Smits Wiep Klaas , Eschevins Caroline C. , Susanna Kim A. , Bron Sierd , Kuipers Oscar P. , Hamoen Leendert W.
Published: April 2005

In Bacillus subtilis competence for genetic transformation develops only in a subpopulation of cells in an isogenic culture. The molecular mechanisms underlying this phenotypic heterogeneity are unknown. In this study, we stepwise simplify the signal transduction cascade leading to competence, yielding a strain devoid of all regulatory inputs for this process that have been identified so far. We demonstrate that auto‐stimulation of ComK, the master regulator for competence development, is essential and in itself can be sufficient to generate a bistable expression pattern. We argue that transcriptional regulation determines the threshold of ComK to initiate the auto‐stimulatory response, and that the basal level of ComK (in a wild‐type strain governed by MecA‐mediated proteolytic control) determines the fraction of cells that reach this threshold, and thus develop competence.
Control of speed modulation (chemokinesis) in the unidirectional rotary motor of Sinorhizobium meliloti
Authors: Attmannspacher Ursula , Scharf Birgit , Schmitt Rüdiger
Published: April 2005

Swimming cells of Sinorhizobium meliloti are driven by flagella that rotate only clockwise. They can modulate rotary speed (achieve chemokinesis) and reorient the swimming path by slowing flagellar rotation. The flagellar motor is energized by proton motive force, and torque is generated by electrostatic interactions at the rotor/stator (FliG/MotA‐MotB) interface. Like the Escherichia coli flagellar motor that switches between counterclockwise and clockwise rotation, the S. meliloti rotary motor depends on electrostatic interactions between conserved charged residues, namely, Arg294 and Glu302 (FliG) and Arg90, Glu98 and Glu150 (MotA). Unlike in E. coli, however, Glu150 is essential for torque generation, whereas residues Arg90 and Glu98 are crucial for the chemotaxis‐controlled variation of rotary speed. Substitutions of either Arg90 or Glu98 by charge‐neutralizing residues or even by their smaller, charge‐maintaining isologues, lysine and aspartate, resulted in top‐speed flagellar rotation and decreased potential to slow down in response to tactic signalling (chemokinesis‐defective mutants). The data infer a novel mechanism of flagellar speed control by electrostatic forces acting at the rotor/stator interface. These features have been integrated into a working model of the speed‐modulating rotary motor.
A bZIP transcription factor from Phytophthora interacts with a protein kinase and is required for zoospore motility and plant infection
Authors: Blanco Flavio A. , Judelson Howard S.
Published: April 2005

Zoospores are critical in the disease cycle of Phytophthora infestans, a member of the oomycete group of fungus‐like microbes and the cause of potato late blight. A protein kinase induced during zoosporogenesis, Pipkz1, was shown to interact in the yeast two‐hybrid system with a putative bZIP transcription factor. This interaction was confirmed in vitro using a pull‐down assay. The transcription factor gene, Pibzp1, was single copy and expressed in all tissues. Transformants of P. infestans stably silenced for Pibzp1 were generated using plasmids expressing its coding region in sense or antisense orientations. A protoplast transformation method induced silencing more efficiently than transformation by an electroporation scheme. Wild‐type and silenced strains exhibited no differences in hyphal growth or morphology, mating, sporangia production or zoospore release. However, zoospores from the mutants spun in tight circles, instead of exhibiting the normal pattern of straight swimming punctuated by turns. Zoospore encystment was unaffected by silencing, but cysts germinated more efficiently than controls. Germinated cysts from the mutants failed to develop appressoria and were unable to infect plants; however, they could colonize wounded tissue. These phenotypes indicate that Pibzp1 is a key regulator of several stages of the zoospore‐mediated infection pathway.
Seeing is believing: the role of videoconferencing in distance learning
Authors: Martin Marie
Published: April 2005

The potential of videoconferencing to enrich distance learning needs to be widely recognised as well as the technology embedded in curriculum delivery and in distance learning programmes. The argument is supported by reference to a wide range of case studies from the author's experiences over a period of six years as International Officer with the Western Education and Library Board in Northern Ireland, and to exemplars of good practice from other sources in different parts of the world. As videoconferencing becomes more widely available in schools and in public libraries, it is important that there is a new awareness of its vast potential in order to ensure that this technology is fully exploited for the benefit of learning communities.
Netskills and the current state of beliefs and practices in student learning: an assessment and recommendations
Authors: Murray Liam , Hourigan Triona , Jeanneau Catherine , Chappell Dominic
Published: April 2005

This article analyses data from over 1000 student questionnaires dealing with how students currently use the web to support their learning. It discusses student understanding, needs, and expectations of the web and the overwhelming perception that the web now forms an integral part of their study and research practices. However, these practices require greater definition and refinement for and by the student. Evidence from some teaching staff is compared with that from students for validation purposes and has also revealed striking differences in perception and attitudes between the two groups. We identify specific needs on the part of most students in our survey who require greater guidance and study skills when using the web. These “Netskills” are described and recommendations are made concerning their acquisition and future development by students who are demanding that such skills become part of their own learning strategies.
Do two heads search better than one? Effects of student collaboration on web search behaviour and search outcomes
Authors: Lazonder Ard W.
Published: April 2005

This study compared Pairs of students with Single students in web search tasks. The underlying hypothesis was that peer‐to‐peer collaboration encourages students to articulate their thoughts, which in turn has a facilitative effect on the regulation of the search process as well as search outcomes. Both hypotheses were supported by the results. Pairs located the target information more often and in less time than Singles did. Pairs also employed a richer repertoire of search strategies and were more proficient in monitoring and evaluating their search behaviour. Implications of these findings for practice and further research are discussed.
What campus‐based students think about the quality and benefits of e‐learning
Authors: Concannon Fiona , Flynn Antoinette , Campbell Mark
Published: April 2005

There is a trend in Irish universities to utilise the benefits of the e‐learning as a mechanism to improve learning performance of campus‐based students. Whilst traditional methods, such as face‐to‐face lectures, tutorials, and mentoring, remain dominant in the educational sector, universities are investing heavily in learning technologies, to facilitate improvements with respect to the quality of learning. The technology to support reuse and sharing of educational resources, or learning objects, is becoming more stable, with interoperability standards maturing. However, debate has raged about what constitutes effective use of learning technology.

This research expands upon a study carried out in 2003 examining students’ perceptions of e‐learning in a large undergraduate accounting class environment. As a result, improvements were made to the instructional design of the course, to enable students to engage interactively with content. The subsequent study, reported in this paper, adopted a broad range of techniques to understand students’ learning experience in depth. The findings of this research provide an insight into how these students really work and learn using technologies, if at all. It is hoped that our findings will improve the experience for both students and lecturers who engage in teaching and learning through this medium.
Causes and Consequences of Changes in Nutrient Structure in the Jiaozhou Bay
Authors: ZHAO Shu‐Jiang , JIAO Nian‐Zhi , SHEN Zhi‐Liang , WU Yu‐Lin
Published: April 2005

Abstract: Concentrations and ratios of nutrients in Jiaozhou Bay, China, have changed much in the past decades, with trends indicating an increase in nitrogen and a decrease in silicate. Statistical analysis has shown that the long‐term variations of nutrients are associated with agricultural activities, precipitation, and anthropogenic factors. Stoichiometric calculations indicate that the nutrient structure has become more and more unbalanced. There has been almost no possibility for nitrogen limitation since the 1980s, the probability of P limitation has increased, and the probability of Si limitation has also increased markedly from the 1980s to the 1990s. As a consequence of changes in nutrient structure, a decrease in the abundance of net phytoplankton was evident, whereas total chlorophyll a, levels have remained roughly unchanged at around 3.55 g/L. Thus, it is likely that smaller species have taken the niche vacated by the larger species. Changes in phytoplankton size and species composition may ultimately lead to various functional and structural changes at the system level.

(Managing editor: Ya‐Qin HAN)
OsDREB4 Genes in Rice Encode AP2‐Containing Proteins that Bind Specifically to the Dehydration‐Responsive Element
Authors: TIAN Xiu‐Hong , LI Xue‐Ping , ZHOU Hua‐Lin , ZHANG Jin‐Song , GONG Zhi‐Zhong , CHEN Shou‐Yi
Published: April 2005

Abstract: Most dehydration‐responsive element‐binding (DREB) factors interact specifically with the dehydration‐responsive element (DRE) and control the expression of many stress‐inducible genes in Arabidopsis. In rice (Oryza sativa L. cv. Lansheng), we cloned three DREB homologs: OsDREB1‐1, OsDREB4‐1, and OsDREB4‐2. The deduced amino acid sequences revealed that each protein contained a potential nuclear localization signal, an AP2 DNA‐binding domain, and a possible acidic activation domain. The yeast one‐hybrid assay indicated that both OsDREB4‐1 and OsDREB4‐2 proteins specifically bound to DRE and activated expression of the dual reporter genes of histidine (HIS3) and galactosidase (LacZ). In rice seedlings, expression of OsDREB4‐1 was induced by dehydration and high salt, whereas OsDREB1‐1 and OsDREB4‐2 were expressed constitutively. Under normal growth conditions, OsDREB1‐1 was expressed strongly in the leaf, sheath, and spike, was expressed relatively weak in the stem and only faintly expressed in the roots, whereas expression of transcripts of OsDREB4‐1 and OsDREB4‐2 was higher in the roots, stem, and spike, lower in the leaf, and undetectable in the sheath. Together, these results imply that expression of the OsDREB genes could be controlled by specific aspects of differentiation or development. Thus, OsDREB4‐1 could function as a trans ‐acting factor in the DRE/DREB regulated stress‐responsive pathway.

(Managing editor: Li‐Hui ZHAO)
Chemical Constituents from the Seeds of Ziziphus jujuba var. spinosa (Bunge) Hu
Authors: LI Li‐Mei , LIAO Xun , PENG Shu‐Lin , DING Li‐Sheng
Published: April 2005

Abstract: To search for new and bioactive minor components from traditional Chinese medicines, a new compound, named jujuphenoside (1), was isolated from the seeds of Ziziphus jujuba var. spinosa (Bunge) Hu. The structure of jujuphenoside was elucidated by spectral and chemical methods, particularly two‐dimensional nuclear magnetic resonance analysis. Together with the new compound, 22 known compounds were also isolated and identified from the seeds of Z. jujuba var. spinosa, among which, epiceanothic acid (2) was first obtained from natural resources, whereas compounds 7–16 were first obtained from this plant.

(Managing editor: Wei WANG)
Effects of Phosphorus Nutrient on the Hydraulic Conductivity of Sorghum (Sorghum vulgare Pers.) Seedling Roots Under Water Deficiency
Authors: SHANGGUAN Zhou‐Ping , LEI Ting‐Wu , SHAO Ming‐An , XUE Qing‐Wu
Published: April 2005

Abstract: Hydroponic experiments were conducted in a growth chamber and changes in the hydraulic conductivity of sorghum (Sorghum vulgare Pers.) roots (Lpr) at the three‐leaf stage were measured using the pressure chamber method. Water deficiency was imposed with polyethylene glycol (PEG) 6000 and the phosphorus (P) levels were controlled by complete Hoagland solution with and without P nutrient. The objective of this study was to investigate the effect of P nutrition on root Lpr under water deficiency. The results showed that the Lpr in P deficiency treatments decreased markedly, but the Lpr recovered to the same value as that of control when sufficient P was supplied for 4–24 h. Water deficiency decreased Lpr, but the hydraulic conductivity of the roots with sufficient P supply was still higher than that of plants without P supply. When resuming water supply, the Lpr of the water‐deficient plants under P supply recovered faster than that of plants without P supply, which indicates that plants with sufficient P nutrient are more drought tolerant and have a greater ability to recover after drought. The treatment of HgCl2 indicated that P nutrient could regulate the Lpr by affecting the activity and the expression levels of aquaporins.

(Managing editor: Ya‐Qin HAN)
THE ROLE OF FINANCIAL RELATIONSHIPS IN THE HISTORY OF AMERICAN CORPORATE FINANCE
Authors: Calomiris Charles W. , Ramirez Carlos D.
Published: April 2005

The American corporate financing system, unlike that of most other countries, has not been organized around a set of “universal banks” that perform a variety of functions for their clients. Indeed, the distinguishing feature of American financial history is the number and variety of financial intermediaries, and their relationships with corporations (and one another). Besides commercial banks, there are investment banks, insurance companies, venture capitalists, commercial paper dealers, mutual funds, and many others. The economic role of such intermediaries is to reduce market frictions such as “asymmetric information” and “agency problems” that otherwise raise the cost of outside capital for U.S. companies.

This article views the changing menu of such intermediaries and their networks as the driving force behind the evolution of American corporate finance. U.S. financial history is seen as a series of institutional and financial innovations designed in large part to work around costly restrictions on relationships–particularly, limits on the scale and scope of U.S. banks–that do not exist in most other countries. In terms of its success in reducing the information and control costs of corporate finance, the history of the American financial system includes periods of significant progress as well as major reversals. Three relatively successful periods– the early 19th‐century in New England, the “incipient” universal banking of the 1920s, and modernday financial capitalism–are separated by periods of drastic reductions in the menu of financial relationships– particularly the Great Depression and its 20‐year aftermath.

Besides new financial claims like preferred stock and new intermediaries such as venture capitalists, another important innovation is new forms of cooperation among intermediaries– especially among banks, venture capitalists, trusts, pensions, and investment banks–that have enabled the U.S. financial system to provide some of the key advantages of universal banking systems. Some of the largest U.S. commercial banks today can be viewed as positioning themselves to play a central coordinating role in these new coalitions of intermediaries. In so doing, they may become the platform for a distinctively American universal banking system.