bluuebunny/crossref_metadata_2025_split huggingface dataset:
Does optimal egg size vary with demographic stage because of a physiological constraint?
Authors: BOWDEN R. M. , HARMS H. K. , PAITZ R. T. , JANZEN F. J. 
Published: July 2004

Summary

Optimal egg size theory predicts that females should produce propagules of a size and number that maximize maternal fitness. However, studies of the allocation of resources to eggs have rarely provided evidence of such optimization. This is presumably because of constraints that limit reproductive allocation. One such example is that of pelvic aperture morphology constraining egg size in turtles.
Growing evidence suggests that even this classic example is incomplete. Hormones that regulate both the reproductive cycle and vitellogenic activity in turtles may provide a novel physiological mechanism for control of egg size.
This physiological constraint hypothesis was explored by examining the relationship between maternally derived yolk hormones and egg mass in the Painted Turtle (Chrysemys picta, Schneider).
Eggs from younger females contained significantly more testosterone in the yolk than did eggs from older females. Younger females laid eggs nearly 20% smaller than those of older females even where body sizes overlapped.
Elevated testosterone levels in younger females may thus constrain egg size physiologically, beyond the well‐known physical constraints imposed by pelvic aperture morphology. The endocrine system may play an important but previously unrecognized role in the evolution of egg size in this model system.
Nitrogen‐use efficiency: trade‐offs between N productivity and mean residence time at organ, plant and population levels
Authors: SILLA F. , ESCUDERO A. 
Published: July 2004

Summary

Nitrogen‐use efficiency (NUEN) is often decomposed into the product of N productivity (AN) and the mean residence time of N (MRTN). Theory suggests a trade‐off between both components, but direct experimental evidence is still scarce. A field study with young trees of the evergreen Quercus ilex and the marcescent‐evergreen Quercus faginea was carried out to test this trade‐off through analysis of plant traits at organ, whole‐plant and population levels.
Specific leaf area (SLA) was the main trait positively related to AN in Q. faginea. By contrast, greater litter production and consumption by caterpillars resulted in larger N losses and shorter MRTN in Q. faginea. Early leaf senescence in Q. faginea produced leaf litter with high N concentration that contributed significantly to N loss. Moreover, Q. ilex had higher plant survivorship. The inverse relationship between leaf longevity and SLA is probably a key component of the trade‐off between N losses and plant N productivity.
Quercus faginea had greater N uptake from soil, linked to its longer specific root length of fine roots and greater biomass allocation to underground tissues. Smaller N losses in Q. ilex compensated for its smaller N uptake and allowed a similar N balance at whole‐plant level.
Our results support the hypothesis of a trade‐off between AN and MRTN. Quercus ilex had a long MRTN, while Q. faginea has a high AN, and vice versa. The long MRTN in Q. ilex involves not only reduced N loss through long intrinsic leaf life span, but also resistance to harsh environmental factors and defence against herbivores. This suggests that a long MRTN is a potentially successful strategy in nutrient‐poor environments.
Seed mass, seedling herbivory and the reserve effect in tropical rainforest seedlings
Authors: GREEN P. T. , JUNIPER P. A. 
Published: July 2004

Summary

The seedlings of larger‐seeded species typically perform better than those of smaller‐seeded species in the face of a variety of hazards. One mechanism that might explain this general pattern is the reserve effect, where larger‐seeded species commit a smaller proportion of their initial seed reserves to seedling construction, keeping a greater proportion in reserve to sustain seedlings during times of resource deficit or imposed hazards.
This study tested two hypotheses: (1) that seedlings of larger‐seeded rainforest species can resprout more often, following simulated herbivory, than those of smaller‐seeded species; and (2) that any such correlation is consistent with the reserve effect.
To test these hypotheses we grew the seedlings of 15 rainforest species with hypogeal storage cotyledons in a shade house, excised the initial shoot, and sequentially clipped each resprout. Previous work had demonstrated a reserve effect among these species.
The first hypothesis was proved true: seedlings of larger‐seeded species resprouted significantly more often than those of smaller‐seeded species.
The second hypothesis was proved false: although large‐seeded species resprouted more often, the total mass invested in resprouts scaled isometrically with seed mass across species. The reserve effect predicted that total resprout mass should have scaled more than proportionately with seed mass.
This study adds to a growing body of work demonstrating that the seedlings of larger‐seeded species often perform better than those of their smaller‐seeded counterparts. However, the results presented here are at odds with the view that the reserve effect might be a common mechanism explaining this pattern.
Extramedullary hematopoiesis in a pyogenic granuloma: a case report and review
Authors: Vega Harring Suzana M. , Niyaz Madinyet , Okada Shinya , Kudo Motoshige 
Published: July 2004

Background:  Extramedullary hematopoiesis in the adult life is usually associated with hematological disorders. It can often occur in several organs under certain pathological conditions, including the spleen, liver, and skin, which are normal sites during the embryogenesis, the skin being very uncommon.Case report:  A case of extramedullary hematopoiesis in a granuloma pyogenicum at the anterior aspect of the right thigh of a 31‐year‐old Japanese man is reported.Results:  Histologic examination revealed an ulcerated polypoid lesion composed of numerous newly formed capillaries and a myxoid edematous stroma. In addition, three islands of hematopoietic precursors were found.Conclusions:  This is, to our knowledge, the second case of extramedullary hematopoiesis in a granuloma pyogenicum. We believe that vascular lesions have potential to generate hematopoietic precursor cells; however, hematopoiesis will only occur in a setting of adequate microenvironment, as it occurs in the bone marrow.
Identification of mariner elements from house flies (Musca domestica) and German cockroaches (Blattella germanica)
Authors: Liu N. , Pridgeon J. W. , Wang H. , Liu Z. , Zhang L. 
Published: July 2004

AbstractFull‐length mariner elements were isolated and sequenced from house flies (Musca domestica) and German cockroaches (Blattella germanica). The amino acid sequence of the house fly mariner element (accession number: AF373028) showed 99.5% identity with Mos1 and peach elements, whereas the German cockroach mariner element (accession number: AF355143) showed 98.8% and 99.8% identity, respectively. Sequence analysis revealed that the mariner elements in house flies and German cockroaches differed from the active Mos1 mariner element by seven and 15 nucleotides, respectively. Four essential nucleotide substitutions at positions 64, 154, 305, and 1203, which have been proposed to contribute to the loss of activity of the inactive elements, were detected in the German cockroach mariner element. In contrast, although the mariner element in house flies contained substitutions at positions 64, 154, and 305, it retained T at position 1203, identical to active mariner elements. Mariner is present in approximately eight copies in the German cockroach genome.
Water relations under root chilling in a sensitive and tolerant tomato species
Authors: BLOOM A. J. , ZWIENIECKI M. A. , PASSIOURA J. B. , RANDALL L. B. , HOLBROOK N. M. , ST. CLAIR D. A. 
Published: July 2004

ABSTRACTThe shoots of cultivated tomato (Lycopersicon esculentum cv. T5) wilt if their roots are exposed to chilling temperatures of around 5 °C. Under the same treatment, a chilling‐tolerant congener (Lycopersicon hirsutum LA 1778) maintains shoot turgor. To determine the physiological basis of this differential response, the effect of chilling on both excised roots and roots of intact plants in pressure chambers were investigated. In excised roots and intact plants, root hydraulic conductance declined with temperature to nearly twice the extent expected from the temperature dependence of the viscosity of water, but the response was similar in both species. The species differed markedly, however, in stomatal behaviour: in L. hirsutum, stomatal conductance declined as root temperatures were lowered, whereas the stomata of L. esculentum remained open until the roots reached 5 °C, and the plants became flaccid and suffered damage. Grafted plants with the shoots of one genotype and roots of another indicated that the differential stomatal behaviour during root chilling has distinct shoot and root components.
Ascorbic acid, a familiar small molecule intertwined in the response of plants to ozone, pathogens, and the onset of senescence
Authors: CONKLIN P. L. , BARTH C. 
Published: July 2004

ABSTRACTAscorbic acid is a well‐known antioxidant and cellular reductant with an intimate and complex role in the response of plants to ozone. It is clear from a number of studies that sensitivity to ozone is correlated with total ascorbic acid levels, and that a first line of defence against the reactive oxygen species generated in the apoplastic space by ozone is ascorbic acid. For activity, ascorbic acid must be in the fully reduced state. Therefore, both the rate of ascorbic acid synthesis and recycling via dehydroascorbate and monodehydroascorbate reductases are critical in the maintenance of a high ascorbic acid redox state. Active transport of ascorbic acid across the plasma membrane is necessary to achieve reduction of oxidized ascorbic acid by cytoplasm‐localized reductases. It has been known for some time that the chlorotic lesions produced by exposure to ozone are not unlike lesions produced by the hypersensitive response to avirulent pathogen attack. Surprisingly, activation of a defence gene‐signalling network by both ozone and pathogens is influenced by the level of ascorbic acid. Indeed, in addition to acting simply as an antioxidant in the apoplastic space, ascorbic acid appears to be involved in a complex phytohormone‐mediated signalling network that ties together ozone and pathogen responses and influences the onset of senescence.
Dynamics and precision of thermoregulatory responses of eastern skunk cabbageSymplocarpus foetidus
Authors: SEYMOUR R. S. 
Published: July 2004

ABSTRACTInflorescences of the arum lilySymplocarpus foetidusare thermogenic and thermoregulatory. The spadix increases respiratory heat production rate as ambient temperature decreases. This study examined the relationships between spadix temperature (Ts), respiration rate () and ambient temperature (Ta) at equilibrium and during transient responses to step changes inTa. Intact inflorescences inside a miniature constant temperature cabinet in the field showed the most precise temperature regulation yet recorded; over a 37.4 °C range inTa(−10.3 to 27.1 °C),Tschanged only 3.5 °C (22.7 to 26.2 °C). Regulated temperatures were not related to spadix size (1.9–7.3 g) or circadian cycle. Dynamic responses to step changes inTainvolved a phasic change inTs, first in the same direction asTa, then reversing at 38.3 min, and finally approaching equilibrium at 87.6 min, on average. Meanwhilechanged in a monotonic curve toward equilibrium. Models revealed that the dynamics of temperature change were inconsistent with simply a physical lag in the system, but involved some form of biochemical regulation, possibly by changes in activity of a rate‐limiting functional protein.
The contribution of fog to the water relations of Sequoia sempervirens (D. Don): foliar uptake and prevention of dehydration
Authors: BURGESS S. S. O. , DAWSON T. E. 
Published: July 2004

ABSTRACTFog is a defining feature of the coastal California redwood forest and fog inputs via canopy drip in summer can constitute 30% or more of the total water input each year. A great deal of occult precipitation (fog and light rain) is retained in redwood canopies, which have some of the largest leaf area indices known (Westman & Whittaker, Journal of Ecology 63, 493–520, 1975). An investigation was carried out to determine whether some fraction of intercepted fog water might be directly absorbed through leaf surfaces and if so, the importance of this to the water relations physiology of coast redwood, Sequoia sempervirens. An array of complimentary techniques were adopted to demonstrate that fog is absorbed directly by S. sempervirens foliage. Xylem sap transport reversed direction during heavy fog, with instantaneous flow rates in the direction of the soil peaking at approximately 5–7% of maximum transpiration rate. Isotopic analyses showed that up to 6% of a leaf's water content could be traced to a previous night's fog deposition, but this amount varied considerably depending on the age and water status of the leaves. Old leaves, which appear most able to absorb fog water were able to absorb distilled water when fully submersed at an average rate of 0.90 mmol m2 s−1, or about 80% of transpiration rates measured at the leaf level in the field. Sequoia sempervirens has poor stomatal control in response to a drying atmosphere, with rates of water loss on very dry nights up to 40% of midday summer values and rates above 10% being extremely common. Owing to this profligate water use behaviour of S. sempervirens, it appears that fog has a greater role in suppressing water loss from leaves, and thereby ameliorating daily water stress, than in providing supplemental water to foliar tissues per se. Although direct foliar absorption from fog inputs represents only a small fraction of the water used each day, fog's in reducing transpiration and rehydrating leaf tissues during the most active growth periods in summer may allow for greater seasonal carbon fixation and thus contribute to the very fast growth rates and great size of this species.
Involvement of abscisic acid and ethylene in the responses of rice grains to water stress during filling
Authors: YANG J. C. , ZHANG J. H. , YE Y. X. , WANG Z. Q. , ZHU Q. S. , LIU L. J. 
Published: July 2004

ABSTRACTThis study was to test the hypothesis that the interaction between abscisic acid (ABA) and ethylene may be involved in mediating the effects of water stress on grain filling. Two high lodging‐resistant rice (Oryza sativa L.) cultivars were pot‐grown. Three treatments, well‐watered, moderate water‐stressed (MD), and severe water‐stressed (SD), were imposed from 9 d post‐anthesis until maturity. Grain filling rate and grain weight were significantly increased under MD but decreased under SD. The two cultivars behaved the same. ABA concentration in the grains was very low during the grain filling stage, reaching a maximum when the grain filling rate was highest. Both the grain filling rate and ABA concentration were substantially enhanced by water stress. In contrast to ABA, concentrations of ethylene and 1‐aminocylopropane ‐1‐carboxylic acid (ACC) in the grains were very high at early grain filling stage and sharply decreased during the linear period of grain growth. MD reduced, whereas SD remarkably increased, their accumulation. The ratio of ABA to ACC was increased in MD grains but decreased in SD grains, indicating that there was a greater enhancement of ABA concentration than ethylene production in the MD treatment only. Application of cobalt ion (inhibitor of ethylene synthesis) or ABA at the early grain filling stage significantly increased grain filling rate. Spraying with ethephon (ethylene‐releasing agent) or fluridone (inhibitor of ABA synthesis) had the opposite effect. The results suggest that antagonistic interactions between ABA and ethylene mediate the grain filling rate, and a high ratio of ABA to ethylene enhances grain filling rate.
Predation Risk Avoidance by Terrestrial Amphibians: The Role of Prey Experience and Vulnerability to Native and Exotic Predators
Authors: Murray D. L. , Roth J. D. , Wirsing A. J. 
Published: July 2004

AbstractWe studied avoidance, by four amphibian prey species (Rana luteiventris, Ambystoma macrodactylum, Pseudacris regilla, Tarichia granulosa), of chemical cues associated with native garter snake (Thamnophis elegans) or exotic bullfrog (R. catesbeiana) predators. We predicted that avoidance of native predators would be most pronounced, and that prey species would differ in the intensity of their avoidance based on relative levels of vulnerability to predators in the wild. Adult R. luteiventris (presumably high vulnerability to predation) showed significant avoidance of chemical cues from both predators, A. macrodactylum (intermediate vulnerability to predation) avoided T. elegans only, while P. regilla (intermediate vulnerability to predation) and T. granulosa (low vulnerability to predation) showed no avoidance of either predator. We assessed if predator avoidance was innate and/or learned by testing responses of prey having disparate levels of prior exposure to predators. Wild‐caught (presumably predator‐exposed) post‐metamorphic juvenile R. luteiventris and P. regilla avoided T. elegans cues, while laboratory‐reared (predator‐naive) conspecifics did not; prior exposure to R. catesbeiana was not related to behavioural avoidance among adult or post‐metamorphic juvenile wild‐reared A. macrodactylum and P. regilla. These results imply that (i) some but not all species of amphibian prey avoid perceived risk from garter snake and bullfrog predators, (ii) the magnitude of this response probably differs according to prey vulnerability to predation in the wild, and (iii) avoidance tends to be largely learned rather than innate. Yet, the limited prevalence and intensity of amphibian responses to predation risk observed herein may be indicative of either a relatively weak predator–prey relationship and/or the limited importance of predator chemical cues in this particular system.
Characterization of a Single‐Spore Isolate Population of Plasmodiophora brassicae Resulting from a Single Club
Authors: Fähling M. , Graf H. , Siemens J. 
Published: July 2004

AbstractThe single‐spore isolates ‘e3’ and ‘e6’ of Plasmodiophora brassicae with different virulence patterns were distinguished by restriction fragment length polymorphisms in fingerprint‐like patterns and by electrophoretic karyotypes using repetitive fragments as hybridization probes. These molecular tools were used to characterize a set of isolates originated from an infected root, which was inoculated with a mixture of the two single‐spore isolates (e3 and e6). Spores harvested from mixed‐infected roots were used to establish 53 new single‐spore isolates. All these single‐spore isolates revealed parental patterns according to their molecular fingerprints and their virulence pattern. No sexual recombination could be detected with repetitive molecular probes. However, one isolate (M36ES49) showed the same fingerprint pattern and virulence pattern but different sizes of small chromosomes than the parental type ‘e6’, which is taken as an indication of chromosome rearrangement during the infection cycle.
Impact of adiposity and plasma adipocytokines on diabetic angiopathies in Japanese Type 2 diabetic subjects
Authors: Matsuda M. , Kawasaki F. , Yamada K. , Kanda Y. , Saito M. , Eto M. , Matsuki M. , Kaku K. 
Published: July 2004

AbstractAims  Adipocytokines, products from adipose tissue, have biological activities on the vascular system, and may affect diabetic angiopathy. In this study, we assessed the relationship between adiposity and plasma adipocytokine levels, and investigated the clinical significance of adiposity and plasma adipocytokine levels on diabetic micro‐ and macroangiopathy in Type 2 diabetic subjects.Methods  We studied 231 Japanese Type 2 diabetic subjects (135 men and 96 women, aged 60.4 ± 12.3 years, body mass index 24.8 ± 5.2 kg/m2). We measured adipocytokine [adiponectin, leptin, resistin, and tumour necrosis factor (TNF)‐α] levels, lipid profiles and urine albumin excretion. We also performed optic fundus examination and measured carotid intramedia thickness (IMT) using B‐mode ultrasonography, and the localization of fat with abdominal computed tomography. A group of 93 subjects with microalbuminuria or overt proteinuria was compared with the other 148 to assess the effect on nephropathy. A group of 191 eyes with simple retinopathy or more advanced changes was compared with 263 eyes without retinal changes to assess the effect on retinopathy.Results  Plasma adiponectin level was negatively correlated with both visceral (r = −0.37, P < 0.01) and subcutaneous (r = −0.25, P < 0.01) fat areas. Resistin concentration was positively related with visceral fat area (r = 0.15, P < 0.05). Adiponectin concentration was positively correlated with age (r = 0.26, P < 0.01). TNF‐α was correlated with IMT (r = 0.16, P < 0.05) after correction for age. Logistic regression analysis indicates a 4085 times greater chance of having retinopathy with a one unit increase in TNF‐α (pmol/l) and a 30.64 times greater chance of having nephropathy with one unit increase in leptin (nmol/l).Conclusions  The present observations suggest that visceral and subcutaneous fat has an impact on microangiopathy as well as macroangiopathy, possibly through different adipocytokines.
Initiation of glucose‐lowering therapy in Type 2 diabetes mellitus patients in general practice
Authors: Spoelstra J. A. , Stolk R. P. , Klungel O. H. , Erkens J. A. , Rutten G. E. H. M. , Leufkens H. G. M. , Grobbee D. E. 
Published: July 2004

AbstractAim  The purpose of this study was to investigate which factors determine the initiation of glucose‐lowering therapy in patients with Type 2 diabetes mellitus in general practice and their future glycaemic control.Methods  All incident Type 2 diabetic patients in the general practices in a Dutch middle‐sized town from 1994 to 2000 were identified. Factors associated with initiation of glucose‐lowering therapy were obtained from clinical files and examined by Cox's regression analyses. Using anova, the associations between clinical characteristics at diagnosis and future glycaemic control were investigated.Results  In total, 603 newly diagnosed patients with Type 2 diabetes mellitus were included in the study. In the first month following diagnosis, 319 (53%) started with oral therapy. One, two and three years after diagnosis of diabetes, the cumulative incidences were 71% (95% CI 66–73%), 75% (71–79%) and 81% (77–84%), respectively. Age, gender, body weight, blood pressure, history of cardiovascular disease or total serum cholesterol values were not associated with time to start of drug therapy. An increased plasma glucose level at diagnosis was strongly related to faster initiation of drug therapy and worse future glycaemic control. Immediate initiation of glucose‐lowering medication was not related to future glycaemic control.Conclusion  This study shows that the initial severity of diabetes, assessed by the degree of hyperglycaemia at time of diagnosis, is a major factor in determining the time to start of glucose‐lowering drugs and the likelihood of achieving target levels of glycaemic control in the future, independent of glucose‐lowering strategy. Therefore, patients with high glucose levels at diagnosis need close monitoring from the beginning of their disease.