bluuebunny/crossref_metadata_2025 huggingface dataset:
Modulation of afterpotentials and firing pattern in guinea pig CA3 neurones by group I metabotropic glutamate receptors
Authors: Young Steven R. , Chuang Shih‐Chieh , Wong Robert K. S.
Published: October 2003

Activation of group I metabotropic glutamate receptors (mGluRs) alters the firing patterns of individual CA3 pyramidal cells in guinea pig hippocampal slices. Following addition of the selective group I agonist (S)‐3,5‐dihydroxyphenylglycine (DHPG) to the bathing solution, pyramidal cells initially firing regular, single action potentials switched to firing in brief bursts. This change in firing pattern resulted from modulation by mGluRs of three afterpotentials. The medium and slow afterhyperpolarizations (m and sAHPs) were blocked by mGluR activation. In addition, a voltage‐dependent afterdepolarization (ADP) was induced. Recordings from mutant mice lacking phospholipase Cβ1 (PLCβ1) showed that mGluR block of the mAHP, as well as induction of the ADP, depended on the phosphoinositide hydrolysis pathway. Block of the sAHP, however, was partly spared in the absence of PLCβ1. Optical recordings of postspike intracellular Ca2+ rises showed that mGluR block of the AHP was not mediated by alterations of action potential‐associated Ca2+ increases (Ca2+ transients). The mGluR induction of an ADP was also independent of any changes in the Ca2+ transient. The mGluR‐induced change in the firing pattern of hippocampal pyramidal cells is thus the result of multiple mechanisms, including suppression of both m and sAHPs and activation of an ADP, that act together to produce a specific excitatory effect, namely an increased likelihood that a single action potential will lead immediately to one or more following action potentials.
Ganglion cell contributions to the rat full‐field electroretinogram
Authors: Bui Bang V. , Fortune Brad
Published: October 2003

The purpose of this study was to determine what contributions are made to the rat full‐field electroretinogram (ERG) by ganglion cells (GCs). To that end, the ERG was assessed longitudinally following optic nerve transection (ONTx). Additional studies were conducted using intravitreal injections of pharmacologically active substances. The ERG was recorded simultaneously from both eyes of anaesthetized adult Brown‐Norway rats (ketamine: xylazine: acepromazine, 55: 5: 1 mg kg−1) using custom silver chloride electrodes. Stimuli were brief, white xenon discharges delivered via a Ganzfeld under dark‐adapted and light‐adapted conditions (150 cd m−2). ERGs were obtained 1, 2, 3, 4 and 9 weeks after ONTx (n= 8) or sham (n= 8) operations. ONTx reduced both positive and negative components of the scotopic threshold response (pSTR and nSTR). Scotopic ERG responses to brighter flashes, including a‐waves, b‐waves and oscillatory potentials (OPs) were unaffected by ONTx. ONTx reduced the photopic b‐wave and OPs. TTX (6 μm) reduced the pSTR and nSTR, but not the scotopic a‐wave, b‐wave or OPs. TTX had dramatic effects on the photopic ERG, surpassing the effects of ONTx. TTX application 9 weeks post‐ONTx had little additional effect on the STR. Inhibition of inner retinal responses using GABA (10 mm) or NMDA (0.8 mm) reduced the nSTR substantially. Similar results were obtained with antagonists of AMPA/KA ionotropic glutamate receptors 6‐cyano‐7‐nitroquinoxaline‐2,3(1H,4H)‐dione (CNQX, 0.2 mm) or cis‐2,3‐piperidinedicarboxylic acid (PDA, 5 mm); however, both also reduced the scotopic b‐wave by ∼40 %. By contrast, the NMDA receptor antagonist D(‐)‐2‐amino‐7‐phosphonoheptanoic acid (D‐AP7, 0.2 mm) had no effect alone, but the combination of D‐AP7 and CNQX completely abolished the STR. The results of this study indicate that: (1) both pSTR and nSTR components in the rat depend directly upon intact GC responses, and that amacrine cell contributions to these components are relatively small; (2) scotopic ERG response components to brighter flashes receive little influence from GCs; (3) the rat photopic ERG also reflects GC signals and may serve as an additional useful test of GC function; (4) TTX had dramatic effects on the rat photopic ERG that were not attributable to GC currents, but rather to voltage‐gated sodium currents in amacrine or interplexiform cells; (5) a small residual negative STR persisted after ONTx that was likely to be generated by graded responses of third‐order retinal cells, most likely amacrine cells.
Thermogenesis elicited by skin cooling in anaesthetized rats: lack of contribution of the cerebral cortex
Authors: Osaka Toshimasa
Published: October 2003

Non‐noxious cooling stimuli were delivered to the shaved back of urethane‐chloralose‐anaesthetized, artificially ventilated rats using a plastic bag containing water at 24–40°C. Cooling of the skin by 2–6°C increased the rate of whole body oxygen consumption and triggered electromyographic (EMG) activity recorded from the neck or femoral muscles. The cooling‐induced responses did not depend on core (colonic) temperature and followed skin temperature in a graded manner. Pretreatment with the β‐blocker propranolol (10 mg kg−1, i.v.) greatly attenuated the response but did not affect the EMG response. On the other hand, pretreatment with the muscle relaxant pancuronium bromide (2 mg kg−1, i.v.) affected the response very slightly but completely abolished the EMG activity. Accordingly, the cooling stimulus activated mainly non‐shivering thermogenesis. Next, the contribution of the cerebral cortex to the cooling‐induced thermogenesis was examined. Power spectral analysis of the electroencephalogram (EEG) showed that the cooling stimulus largely inhibited delta (0.5–3 Hz) waves, enhanced theta (3–8 Hz) waves, and slightly increased frequencies higher than 8 Hz. Pinching the hindpaw elicited changes in EEG similar to those elicited by skin cooling but did not increase the . Therefore, there was no relationship between changes in the EEG and the magnitude of thermogenesis. Finally, skin cooling increased the of decorticated rats but did not increase that of decerebrated rats. The results suggest that the subcortical forebrain structure, but not cortical activation, is indispensable for non‐shivering thermogenesis elicited by cooling stimulation of the skin.
Evidence for the involvement of VPAC1 and VPAC2 receptors in pressure‐induced vasodilatation in rodents
Authors: Fizanne Lionel , Sigaudo‐Roussel Dominique , Saumet Jean Louis , Fromy Bérengère
Published: October 2003

A transient increase in skin blood flow in response to an innocuous local pressure application, defined as pressure‐induced vasodilatation (PIV), delays the occurrence of ischaemia, suggesting a protective feature against applied pressure. The PIV response depends on capsaicin‐sensitive nerve fibres and calcitonin gene‐related peptide (CGRP) has been shown to be involved. In these fibres, CGRP coexists with pituitary adenylate cyclase‐activating polypeptide (PACAP). Three distinct receptors mediate the biological effects of PACAP: VPAC1 and VPAC2 receptors binding with the same affinity for PACAP and vasoactive intestinal peptide and PAC1 receptors showing high selectivity for PACAP. Because the receptors are widely expressed in the nervous system and in the skin, we hypothesized that at least one of them is involved in PIV development. To verify this hypothesis, we used [d‐p‐Cl‐Phe6,Leu17]‐VIP (nonspecific antagonist of VPAC1/VPAC2 receptors), PG 97‐269 (antagonist of VPAC1 receptors), PACAP(6–38) (antagonist of VPAC2/PAC1 receptors) and Max.d.4 (antagonist of PAC1 receptors) in anaesthetized rodents. The blockade of VPAC1/VPAC2, VPAC1 or VPAC2/PAC1 receptors eliminated the PIV response, whereas PAC1 blockade had no effect, demonstrating an involvement of VPAC1/VPAC2 receptors in PIV development. Moreover, endothelium‐independent and ‐dependent vasodilator responses were unchanged by the VPAC1/VPAC2 antagonist. Thus, the absence of a PIV response following VPAC1/VPAC2 blockade cannot be explained by any dysfunction of the vascular smooth muscle or endothelial vasodilator capacity. The involvement of VPAC1/VPAC2 receptors in the development of PIV seems to imply a series relationship in which each receptor type (CGRP, VPAC1, VPAC2) is necessary for the full transmission of the response.
Structural changes in loaded equine tendons can be monitored by a novel spectroscopic technique
Authors: Kostyuk Oksana , Birch Helen L. , Mudera Vivek , Brown Robert A.
Published: October 2003

This study aimed to investigate the preferential collagen fibril alignment in unloaded and loaded tendons using elastic scattering spectroscopy. The device consisted of an optical probe, a pulsed light source (320–860 nm), a spectrometer and a PC. Two probes with either 2.75 mm or 300 μm source‐detector separations were used to monitor deep and superficial layers, respectively. Equine superficial digital flexor tendons were subjected toex vivoprogressive tensional loading. Seven times more backscattered light was detected parallel rather than perpendicular to the tendon axis with the 2.75 mm separation probe in unloaded tendons. In contrast, using the 300 μm separation probe the plane of maximum backscatter (3‐fold greater) was perpendicular to the tendon axis. There was no optical anisotropy in the cross‐sectional plane of the tendon (i.e. the transversely cut tendon surface), with no structural anisotropy. During mechanical loading (9–14% strain) backscatter anisotropy increased 8.5‐ to 18.5‐fold along the principal strain axis for 2.75 mm probe separation, but almost disappeared in the perpendicular plane (measured using the 300 μm probe separation). Optical (anisotropy) and mechanical (strain) measurements were highly correlated. We conclude that spatial anisotropy of backscattered light can be used for quantitative monitoring of collagen fibril alignment and tissue reorganization during loading, with the potential for minimally invasive real‐time structural monitoring of fibrous tissues in normal, pathological or repairing tissues and in tissue engineering.
Placental vascular endothelial growth factor receptor system mRNA expression in pigs selected for placental efficiency
Authors: Vonnahme Kimberly A. , Ford Stephen P.
Published: October 2003

Selecting Yorkshire breeding stock for increased placental efficiency (PE; piglet weight divided by its placental weight) results in larger litters (i.e. ∼3 more piglets litter−1) and reduced placental sizes. Placental vessel density increases progressively after day 50 of gestation in the pig, and is positively correlated with PE and placental expression of vascular endothelial growth factor (VEGF), a potent angiogenic and permeability factor. To elicit its vascular effects, VEGF must bind to its receptors (R), VEGF‐R1 and VEGF‐R2. The objective of this study was to compare placental and endometrial blood vessel density and placental VEGF, VEGF‐R1 and VEGF‐R2 mRNA expression in day 70 and 90 conceptuses from Yorkshire females selected for high PE, low PE, and from unselected controls. A greater (P < 0.05) PE was observed for conceptuses in the high PE selection group when compared to the low PE selection group. Placental blood vessel density increased (P < 0.05) from day 70 to 90 (1.8 ± 0.1 versus 2.8 ± 0.2) in association with increases (P < 0.05) in placental VEGF mRNA expression. No selection group differences were observed in expression of VEGF, VEGF‐R1, or VEGF‐R2 on day 70. By day 90, however, placentae of conceptuses from the high PE group expressed greater (P < 0.05) amounts of VEGF and VEGF‐R1 mRNA than the unselected controls and the low PE group. These data demonstrate that increased placental expression of the VEGF receptor system is associated with increased placental vascular density observed with the advancement of gestation in the pig. Although placental blood vessel density was not increased in the high PE selection group, elevated levels of the VEGF receptor system suggest an effect on increasing placental and endometrial blood vessel permeability and/or proximity in the high PE group.
Modulation of the excitability of cholinergic basal forebrain neurones by KATP channels
Authors: Allen T. G. J. , Brown D. A.
Published: October 2003

The expression of ATP‐sensitive K+ (KATP) channels by magnocellular cholinergic basal forebrain (BF) neurones was investigated in thin brain slice and dissociated cell culture preparations using a combination of whole‐cell, perforated‐patch and single‐channel recording techniques. Greater than 95% of BF neurones expressed functional KATP channels whose activation resulted in membrane hyperpolarization and a profound fall in excitability. The whole‐cell KATP conductance was 14.0 ± 1.5 nS and had a reversal potential of –91.4 ± 0.9 mV that shifted by 59.6 mV with a tenfold increase in [K+]o. IKATP was inhibited reversibly by tolbutamide (IC50 of 34.1 μm) and irreversibly by glibenclamide (0.3–3 nm) and had a low affinity for [ATP]i (67% reduction with 6 mm[MgATP]i). Using perforated‐patch recording, a small proportion of the conductance was found to be tonically active. This was weakly potentiated by diazoxide (0.1 mm extracellular glucose) but insensitive to pinacidil (≤500 μm). Single‐channel KATP currents recorded in symmetrical 140 mm K+‐containing solutions exhibited weak inward rectification with a mean conductance of 66.2 ± 1.9 pS. Channel activity was inhibited by MgATP (>50 μm) and activated by MgADP (200 μm). The K+ channels opener diazoxide (200–500 μm) increased channel opening probability (NPo) by 486 ± 120% whereas pinacidil (500 μm) had no effect. In conclusion, the characteristics of the KATP channels expressed by BF neurones are very similar to channels composed of SUR1 and Kir6.2 subunits. In the native cell, their affinity for ATP is close to the resting [ATP]i, potentially allowing them to be modulated by physiologically relevant changes in [ATP]i. The effect of these channels on the level of ascending cholinergic excitation of the cortex and hippocampus is discussed.
Targeted Protein Degradation and Synapse Remodeling by an Inducible Protein Kinase
Authors: Pak Daniel T. S. , Sheng Morgan
Published: October 2003

Synaptic plasticity involves the reorganization of synapses at the protein and the morphological levels. Here, we report activity-dependent remodeling of synapses by serum-inducible kinase (SNK). SNK was induced in hippocampal neurons by synaptic activity and was targeted to dendritic spines. SNK bound to and phosphorylated spine-associated Rap guanosine triphosphatase activating protein (SPAR), a postsynaptic actin regulatory protein, leading to degradation of SPAR. Induction of SNK in hippocampal neurons eliminated SPAR protein, depleted postsynaptic density–95 and Bassoon clusters, and caused loss of mature dendritic spines. These results implicate SNK as a mediator of activity-dependent change in the molecular composition and morphology of synapses.
A Transient Rise in Tropical Sea Surface Temperature During the Paleocene-Eocene Thermal Maximum
Authors: Zachos James C. , Wara Michael W. , Bohaty Steven , Delaney Margaret L. , Petrizzo Maria Rose , Brill Amanda , Bralower Timothy J. , Premoli-Silva Isabella
Published: October 2003

The Paleocene-Eocene Thermal Maximum (PETM) has been attributed to a rapid rise in greenhouse gas levels. If so, warming should have occurred at all latitudes, although amplified toward the poles. Existing records reveal an increase in high-latitude sea surface temperatures (SSTs) (8° to 10°C) and in bottom water temperatures (4° to 5°C). To date, however, the character of the tropical SST response during this event remains unconstrained. Here we address this deficiency by using paired oxygen isotope and minor element (magnesium/calcium) ratios of planktonic foraminifera from a tropical Pacific core to estimate changes in SST. Using mixed-layer foraminifera, we found that the combined proxies imply a 4° to 5°C rise in Pacific SST during the PETM. These results would necessitate a rise in atmospheric pCO
2
to levels three to four times as high as those estimated for the late Paleocene.
R57K Polymorphism in the Human Immunodeficiency Virus Type 1 Protease as Predictor of Early Virological Failure in a Cohort of Antiretroviral-Naive Patients Treated Mostly with a Nelfinavir-Containing Regimen
Authors: Masquelier Bernard , Droz Cecile , Dary Martin , Perronne Christian , Ferré Virginie , Spire Bruno , Descamps Diane , Raffi François , Brun-Vézinet Françoise , Chêne Geneviève ,   the APROCO/COPILOTE Study Group
Published: October 2003

In 243 antiretroviral-naive human immunodeficiency-infected patients starting a first-line-protease inhibitor (mainly nelfinavir)-containing therapy, the presence of the polymorphism R57K in the protease at the inception of therapy was independently associated with a higher rate of virological failure.
Understanding latitudinal trends in fish body size through models of optimal seasonal energy allocation
Authors: Garvey James E , Marschall Elizabeth A
Published: October 2003

For fish at high latitudes, short growing seasons should constrain size-at-age, although the converse often occurs. We used a dynamic state variable model to find energy allocation strategies to length, fat, and ovaries that maximize expected egg production of largemouth bass (Micropterus salmoides). We determined how latitudes and rations affect optimal allocation and then simulated growth using optimal strategies. A theoretical reciprocal transplant explored how latitude-specific optimal strategies affected growth at other latitudes. At low ration, allocation and growth were similar among latitudes, with length selected in small individuals and reproductive tissue and fat in large counterparts. At high rations, low-latitude fish invested most energy to length and reproduction; high-latitude fish allocated to length during summer and fat during fall and developed ovaries earlier in the year. Transplants revealed that smaller size-at-age occurs in the north than in the south, consistent with field patterns for largemouth bass. Although northern strategies allowed fish to be successful in the south, southern strategies were unsuccessful in the north. Latitude-specific energetic adaptations may compromise success of fish transplanted beyond their native distribution.
Functional responses of haemocytes in the clamTapes philippinarumfrom the Lagoon of Venice: fishing impact and seasonal variations
Authors: Matozzo Valerio , Ros Luisa Da , Ballarin Loriano , Meneghetti Francesca , Marin Maria Gabriella
Published: October 2003

In the last few years, the Manila clam (Tapes philippinarum) has been subjected to intense fishing effort in the Lagoon of Venice owing to their commercial importance. Because of the lack of data concerning fishing-induced immunomodulation in bivalves, the consequences of fishing impact on functional responses of clam haemocytes were investigated. Clams were seasonally collected from September 2000 to July 2001 from three sites: S. Angelo, a free-fishing area, and Chioggia, inside a licensed area for clam culture, in two zones characterised by fishing and non fishing, respectively. Haematocrit, phagocytosis, Neutral Red retention time, and lysozyme and superoxide dismutase activities were evaluated. No clear fishing effect was recorded, whereas a seasonal pattern of the cell para meters analysed was revealed. Alterations in functional responses of haemocytes seem to be more closely dependent on seasonal variations in both environmental parameters and physiological status of clams than on stress caused by fishing, and they may also be related to adaptation strategies of bivalves.
Mapping the abundance of riverine fish populations: integrating hierarchical Bayesian models with a geographic information system (GIS)
Authors: Wyatt Robin J
Published: October 2003

A hierarchical Bayesian model is described for mapping the abundance of fish throughout a watershed from single- and multiple-pass removal sampling. A geographic information system (GIS) was used to generate a raster-based model of the river network, which provided three benefits for estimating fish density. Firstly, the horizontal resolution of the raster (50 m) provided an approximation to the statistical sampling frame and allowed correction for the finite number of potential sampling sites in a reach. Secondly, the modelled river network generated explanatory variables for every site in the network, facilitating the mapping of predicted densities and providing the basis for stratified or regression estimators for reach-specific densities. Finally, the spatial autocorrelation of fish densities was modelled in terms of the distance along the river network. A similar Bayesian model was also developed for the wetted width of the river network, and this was combined with the density model to provide estimates of the total stock size. The model was implemented using Markov chain Monte Carlo simulation in the statistical package WinBUGS. Application of the hierarchical model is illustrated with electrofishing data for age-1+ sea trout (Salmo trutta) in a small tributary of the River Conwy, Wales.
Interactions between hatchery and wild salmonids in streams: differences in biology and evidence for competition
Authors: Weber Edward D , Fausch Kurt D
Published: October 2003

Competition between hatchery-reared and wild salmonids in streams has frequently been described as an important negative ecological interaction, but differences in behavior, physiology, and morphology that potentially affect competitive ability have been studied more than direct tests of competition. We review the differences reported, designs appropriate for testing different hypotheses about competition, and tests of competition reported in the literature. Many studies have provided circumstantial evidence for competition, but the effects of competition were confounded with other variables. Most direct experiments of competition used additive designs that compared treatments in which hatchery fish were introduced into habitats containing wild fish with controls without hatchery fish. These studies are appropriate for quantifying the effects of hatchery fish at specific combinations of fish densities and stream carrying capacity. However, they do not measure the relative competitive ability of hatchery versus wild fish because the competitive ability of hatchery fish is confounded with the increased density that they cause. We are aware of only two published studies that used substitutive experimental designs in which density was held equal among treatments, thereby testing for differences in competitive ability. Additional substitutive experiments will help managers to better understand the ecological risk of stocking hatchery fish.
Physical constraints on trout (Oncorhynchus spp.) distribution in the Cascade Mountains: a comparison of logged and unlogged streams
Authors: Latterell Joshua J , Naiman Robert J , Fransen Brian R , Bisson Peter A
Published: October 2003

The upstream extent of coastal cutthroat (Oncorhynchus clarki clarki) and rainbow (Oncorhynchus mykiss) trout distribution in logged and unlogged streams of the western Cascade Mountains appears to be primarily constrained by steep channel gradient and sparse pool habitat. Narrow or intermittent wetted channels are also important constraints in logged drainages. The upstream extent of trout distribution appears to be resilient to the combined impacts of historic and current forest management activities, in the absence of impassable road culverts. The probability of trout presence decreased with channel gradient and increased with pool abundance in both logged and unlogged streams, as indicated by logistic regression analysis of physical stream attributes flanking the trout distribution limit in 37 logged and 21 unlogged streams. Reductions in wetted channel width reduced the likelihood of trout presence in logged streams. Logistic regression models fit to data from logged drainages generated accurate predictions of trout presence or absence when applied to data from unlogged drainages. The pervasive extent of native trout in the channel networks of the Cascade Mountains emphasizes the ecological importance of small streams in watershed planning.
Relationship between natural productivity and the frequency of wild fish in mixed spawning populations of wild and hatchery steelhead (Oncorhynchus mykiss)
Authors: Chilcote Mark W
Published: October 2003

The proportion of wild fish in 12 mixed populations of hatchery and wild steelhead (Oncorhynchus mykiss) was evaluated for its relationship to mean and intrinsic measures of population productivity. The population mean of ln(recruits/spawner) was used to represent mean productivity. Intrinsic productivity was represented by values for the Ricker a parameter as estimated from fits of spawner and recruit data. Significant regressions (p < 0.001) were found between both measures of productivity and the proportion of wild fish in the spawning population (Pw). The slopes of the two regressions were not significantly different (p = 0.55) and defined a relationship suggesting that a spawning population comprised of equal numbers of hatchery and wild fish would produce 63% fewer recruits per spawner than one comprised entirely of wild fish. Study findings were not sensitive to likely levels of data error or confounded by extraneous habitat correlation with Pw. Population status assessments and conservation monitoring efforts should include Pw as a critical variable. For natural populations, removal rather than addition of hatchery fish may be the most effective strategy to improve productivity and resilience.
The effects of adjacent land use on wetland amphibian species richness and community composition
Authors: Houlahan Jeff E , Findlay C Scott
Published: October 2003

Habitat destruction and fragmentation have been identified as possible causes of large-scale amphibian declines. Here, we examine the effects of adjacent land use and water quality on wetland amphibian species richness, abundance, and community composition in 74 Ontario wetlands. Species richness was positively correlated with wetland area, forest cover, and the amount of wetlands on adjacent lands and negatively correlated with road density and nitrogen levels. The land-use effects peak at 20003000 m. Amphibian abundance was positively correlated with forest cover, distance to wetlands >20 ha, and amount of marsh habitat and negatively correlated with road density. The effects of adjacent land use were strongest at around 200 m. Land-use and water quality effects varied widely across species, although most species are positively correlated with forest cover and amount of wetlands on adjacent lands and negatively correlated with road density and water quality. These results suggest that the effects of adjacent land use on amphibian communities can extend over comparatively large distances. As such, effective wetland conservation will not be achieved merely through the creation of narrow buffer zones between wetlands and intensive land uses, but rather will require maintaining a heterogeneous regional landscape containing relatively large areas of natural forest and wetlands.
Finding fish: grouping and catch-per-unit-effort in the Pacific hake (Merluccius productus) fishery
Authors: Ruttan Lore M
Published: October 2003

Numerous papers have documented the problems in estimating stock abundance using only catch-per-unit-effort (CPUE) data. In this paper, logbook data from the onshore processing sector of the Pacific hake (Merluccius productus) fishery in Oregon from 1992 to 1996 are used to analyze the effect of grouping on CPUE and on search time. Two groups are investigated: (i) simple daily aggregations of vessels on fishing grounds and (ii) yearly information-sharing groups. It is found that both groups are positively associated with CPUE; however, in 1995, this result may be the spurious result of more vessels being drawn into the fishery by good conditions. It is argued that in other years, fishers benefit from grouping by being able to find high-quality patches. Fishers in larger groups also experienced lower search times from 1993 to 1995. However, a pattern of declining effect of information-sharing groups from 1993 to 1996 suggests that fishers who were relatively new to this fishery became less reliant on information-sharing networks for finding patches of fish, although fishers in larger groups still may have benefitted by being able to find higher quality patches.
A temperature- and size-dependent model of sand shrimp (Crangon septemspinosa) predation on juvenile winter flounder (Pseudopleuronectes americanus)
Authors: Taylor David L , Collie Jeremy S
Published: October 2003

We investigated the temperature-mediated vulnerability of postsettled winter flounder (Pseudopleuronectes americanus) to sand shrimp (Crangon septemspinosa) predation. Small increases in flounder growth rates substantially decreased predator-induced mortality. Recent warming trends in Northwest Atlantic estuaries can increase flounder survival by accelerating growth and minimizing the duration during which juveniles are susceptible to size-dependent predation. Extreme temperature increases, however, depress growth because a disproportionate amount of energy is devoted to increased metabolism, leaving less for somatic development. Flounder survival is also reduced during warm years because of intensified shrimp predation. Moreover, interannual variations in temperature affect the relative timing of shrimp migration and flounder settlement, thus controlling the spatial and temporal overlap between predator and prey. Predicted flounder abundance and survival were statistically unrelated to observed flounder abundance sampled annually during late spring. However, model predictions and field data suggest that flounder abundance is maximal in years when seasonally averaged temperature is approximately 16 °C. Above and below this temperature, flounder year-class size is considerably lower, possibly as a result of temperature effects on trophic dynamics. We conclude that shrimp predation is a significant source of mortality for postsettled flounder, but it is not the sole determinant of interannual variations in recruitment.
Physical forcing and the dynamics of the pelagic ecosystem in the eastern tropical Pacific: simulations with ENSO-scale and global-warming climate drivers
Authors: Watters George M , Olson Robert J , Francis Robert C , Fiedler Paul C , Polovina Jeffrey J , Reilly Stephen B , Aydin Kerim Y , Boggs Christofer H , Essington Timothy E , Walters Carl J , Kitchell James F
Published: October 2003

We used a model of the pelagic ecosystem in the eastern tropical Pacific Ocean to explore how climate variation at El Niño  Southern Oscillation (ENSO) scales might affect animals at middle and upper trophic levels. We developed two physical-forcing scenarios: (1) physical effects on phytoplankton biomass and (2) simultaneous physical effects on phytoplankton biomass and predator recruitment. We simulated the effects of climate-anomaly pulses, climate cycles, and global warming. Pulses caused oscillations to propagate through the ecosystem; cycles affected the shapes of these oscillations; and warming caused trends. We concluded that biomass trajectories of single populations at middle and upper trophic levels cannot be used to detect bottom-up effects, that direct physical effects on predator recruitment can be the dominant source of interannual variability in pelagic ecosystems, that such direct effects may dampen top-down control by fisheries, and that predictions about the effects of climate change may be misleading if fishing mortality is not considered. Predictions from ecosystem models are sensitive to the relative strengths of indirect and direct physical effects on middle and upper trophic levels.
The effect of turbulence on the cost of swimming for juvenile Atlantic salmon (Salmo salar)
Authors: Enders Eva C , Boisclair Daniel , Roy André G
Published: October 2003

Fish activity costs are often estimated by transforming their swimming speed in energy expenditures with respirometry models developed while forcing fish to swim against a flow of constant velocity. Forced swimming models obtained using a procedure that minimizes flow heterogeneity may not represent the costs of swimming in rivers characterized by turbulence and by a wide range of instantaneous flow velocities. We assessed the swimming cost of juvenile Atlantic salmon (Salmo salar) in turbulent flows using two means (18 and 23 cm·s1) and two standard deviations of flow velocity (5 and 8 cm·s1). Twenty respirometry experiments were conducted at 15 °C with fish averaging 10 g. Our results confirmed that swimming costs are affected by the level of turbulence. For a given mean flow velocity, swimming costs increased 1.3- to 1.6-fold as turbulence increased. Forced swimming models under estimated actual swimming costs in turbulent flow by 1.9- to 4.2-fold. Spontaneous swimming models overestimated the real cost of swimming in turbulent flow by 2.8- to 6.6-fold. Our analyses suggest that models in which both the mean and the standard deviation of flow velocity are explicitly represented are needed to adequately estimate the costs of swimming against turbulent flows.
Molecular mapping of seed aliphatic glucosinolates inBrassica juncea
Authors: Mahmood T , Ekuere U , Yeh F , Good A G , Stringam G R
Published: October 2003

An RFLP genomic map with 316 loci was used to study the inheritance of aliphatic glucosinolates in Brassica juncea using doubled-haploid (DH) populations developed from a cross between RLM-514, an agronomically superior non-canola quality B. juncea (high erucic acid and high glucosinolates), and an agronomically poor canola quality B. juncea breeding line. Two QTLs (GSL-A2a and GSL-A2b) associated with 3-butenyl were consistent across years and locations, and explained 75% of the phenotypic variance in the population. Three QTLs (GSL-A2a, GSL-F, GSL-B3) affected 2-propenyl and explained 78% of the phenotypic variance in the population. For total aliphatic glucosinolates, five QTLs explained 30% to 45% of the total phenotypic variance in the population in different environments. Several QTLs (GSL-A7 and GSL-A3) were highly inconsistent in different environments. Major QTLs (GSL-A2a and GSL-A2b) associated with individual glucosinolates were non-significant for total aliphatic glucosinolates. A marker-assisted selection strategy based on QTLs associated with individual glucosinolates rather than total aliphatic glucosinolates is proposed for B. juncea.Key words: Brassica juncea, aliphatic glucosinolate, 2-propenyl, 3-butenyl, RFLP genome map, QTLs, marker-assisted selection.
Molecular characterization of a wheat  Thinopyrum ponticum partial amphiploid and its derivatives for resistance to leaf rust
Authors: Li Hongjie , Chen Qin , Conner Robert L , Guo Beihai , Zhang Yanmin , Graf Robert J , Laroche André , Jia Xu , Liu Gongshe , Chu Chihching
Published: October 2003

Leaf rust (caused by Puccinia triticina Eriks.) occurs annually in most wheat-growing areas of the world. Thinopyrum ponticum (Podp.) Z.-W. Liu & R.-C. Wang has provided several leaf rust resistance genes to protect wheat from this fungal disease. Three chromosome substitution lines, Ji806, Ji807, and Ji859, and two chromosome addition lines, Ji791 and Ji924, with a winter growing habit were developed from crosses between wheat (Triticum aestivum L. em Thell.) and the wheat  Th. ponticum partial amphiploid line 693. These lines were resistant to leaf rust isolates from China. Sequence-tagged site (STS) analysis with the J09-STS marker, which is linked to the gene Lr24, revealed that the partial amphiploid line 693 and all of the substitution and addition lines carried gene Lr24. Genomic in situ hybridization (GISH) analysis was carried out on chromosome preparations using total genomic DNA from Pseudoroegneria strigosa (M. Bieb) A. Löve (St genome, 2n = 14) as a probe in the presence of total genomic DNA from T. aestivum 'Chinese Spring' wheat (ABD genomes, 2n = 42). The GISH analysis demonstrated that these lines had a pair of chromosomes displaying the typical pattern of a Js genome chromosome. This indicates that the chromosome that carries gene Lr24 belonged to the Js genome of Th. ponticum. In addition to 40 wheat chromosomes, eight Js and eight J genome chromosomes were also differentiated by GISH in the partial amphiploid line 693. Since most sources of Lr24 have a red grain color, the white-colored seeds in all of these substitution and addition lines, together with high protein content in some of the lines, make them very useful as a donor source for winter wheat breeding programs.Key words: Lr24, genomic in situ hybridization, sequence-tagged site, random amplified polymorphic DNA.
Microsatellite-AFLP for genetic mapping of complex polyploids
Authors: Albertini Emidio , Porceddu Andrea , Marconi Gianpiero , Barcaccia Gianni , Pallottini Luca , Falcinelli Mario
Published: October 2003

In spite of the economical relevance of polyploid crops, genetic mapping of these species has been relatively overlooked. This is because of intrinsic difficulties such as the uncertainty of the chromosome behavior at meiosis I and the need for very large segregating populations. An important, yet underestimated issue, in mapping polyploids is the choice of the molecular marker system. An ideal molecular marker system for polyploid mapping should maximize the percentage of single dose markers (SDMs) detected and the possibility of recognizing allelic markers. In the present work, the marker index for genetic mapping (MIgm) of M-AFLP is compared with that of AFLP and SAMPL. M-AFLPs have the highest MIgmvalues (22 vs. 18.5 of SAMPL and 9.83 of AFLP) mostly because of their high power to detect polymorphism. Owing to their prevalent codominant inheritance, it is proposed that M-AFLP can be used for the preliminary identification of hom(e)ologous groups.Key words: AFLP, mapping, microsatellite-AFLP, polyploids, SSR.
Linkage map ofCucumis meloincluding phenotypic traits and sequence-characterized genes
Authors: Silberstein Leah , Kovalski Irina , Brotman Yariv , Perin Christophe , Dogimont Catherine , Pitrat Michel , Klingler John , Thompson Gary , Portnoy Vitali , Katzir Nurit , Perl-Treves Rafael
Published: October 2003

A new linkage map of Cucumis melo, derived from the F2progeny of a cross between PI 414723 and C. melo 'TopMark' is presented. The map spans a total of 1421 cM and includes 179 points consisting of random amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), inter-simple sequence repeats (ISSRs), simple sequence repeats (SSRs), and restriction fragment length polymorphism (RFLP) markers. The map also includes an aphid resistance trait (Vat) and the sex type gene, andromonoecious (a), the two of which are important in resistance breeding and the control of hybrid seed production, as well as a seed-color gene, Wt-2. Most RFLPs represent sequence-characterized cDNA probes from C. melo and Cucumis sativus. These include resistance gene homologues and genes involved in various aspects of plant development and metabolism. A sub-set of our SSR and RFLP markers were also mapped, as part of this study, on additional mapping populations that were published for this species. This provides important reference points ("anchors"), enabling us to identify several linkage groups with respect to other melon maps.Key words: Cucumis melo, melon, genetic map, molecular markers, resistance gene homologues.
Structure and evolution of theCinfulretrotransposon family of maize
Authors: Sanz-Alferez Soledad , SanMiguel Phillip , Jin Young-Kwan , Springer Patricia S , Bennetzen Jeffrey L
Published: October 2003

A maize cDNA clone was isolated by virtue of its intense hybridization to total maize genomic DNA, indicating homology to highly repetitive sequences. Genomic homologues were identified and subcloned from an adh1-bearing maize yeast artificial chromosome (YAC). Sequencing revealed that the expressed sequence was part of a Ty3-gypsy-type retrotransposon. We discovered and sequenced two complete retrotransposons of this family, and named them Cinful elements because they are members of a family of maize retrotransposons including Zeon-1 and the first plant transposable element sequenced, the solo long terminal repeat (LTR) called Cin1. All are defective, as Cinful-1 and Cinful-2 elements lack gag and Zeon-1 lacks pol homology. Despite the apparent lack of an intact "autonomous" element, the Cinful family has expanded to a copy number of about 18 000, representing just under 9% of the maize genome. Both point mutations and major rearrangements, including possible gene acquisition, differentiate members of the Cinful family. Cinful family members were found to have an unusual feature that we also observed in two other Ty3-class retrotransposons of teosinte and tobacco: related tandem repeats that separate their internal domains with a gag- or pol-containing homology from a 3' segment of unknown function. The conserved and variable features identified provide insights into the origin, mutational history, and functional components of this major constituent of the maize genome.Key words: Cin1, genome evolution, sequence divergence, Ty3-gypsy elements, Zeon-1.
The use of multiple alien chromosome addition aneuploids facilitates genetic linkage mapping of theGossypiumG genome
Authors: Brubaker Curt L , Brown Anthony H.D
Published: October 2003

Primary germplasm pools represent the most accessible source of new alleles for crop improvement, but not all effective alleles are available in the primary germplasm pool, and breeders must sometimes confront the difficulties of introgressing genes from the secondary and tertiary germplasm pools in cotton by using synthetic polyploids as introgression bridges. Two parental Gossypium nelsonii × Gossypium australe AFLP genetic linkage maps were used to identify G genome chromosome-specific molecular markers, which in turn were used to track the fidelity and frequency of G. australe chromosome transmission in a Gossypium hirsutum × G. australe hexaploid bridging family. Conversely, when homoeologous recombination is low, first generation aneuploids are useful adjuncts to genetic linkage mapping. Although locus ordering was not possible, the distribution of AFLP markers among 18 multiple chromosome addition aneuploids identified mapping errors among the G. australe and G. nelsonii linkage groups and assigned non-segregating G. australe AFLPs to linkage groups. Four putatively recombined G. australe chromosomes were identified in 5 of the 18 aneuploids. The G. australe and G. nelsonii genetic linkage maps presented here represent the first AFLP genetic linkage maps for the Gossypium G genome.Key words: Gossypium, G genome, AFLP, cotton, aneuploid.
Some morphological, growth, and genomic properties of human cells chronically infected with porcine endogenous retrovirus (PERV)
Authors: Kuddus Ruhul H , Gandhi Chandrashekhar R , Rehman Khaja K , Guo Fengli , Watkins Simon C , Valdivia Luis A , Fung John J
Published: October 2003

A major concern in using porcine organs for transplantation is the potential of transmission of porcine endogenous retrovirus (PERV). To investigate the long-term effects of PERV infection on human cells, human embryonic kidney cell line HEK-293 infected with PERV PK-15 was maintained for up to 72 passages and samples were harvested at intervals for use in morphological, growth, and genomic analyses. Morphology, DNA content/cell, and doubling time of uninfected and infected cells were similar. Restriction fragment length polymorphism (RFLP) analysis of PCR-amplified nearly full-length PERV genome showed no alterations in band pattern. RFLP analysis of the long terminal repeats (LTR) showed some changes in band pattern, but not in length. Southern blot analysis of genomic DNA of infected cells indicated random integration of PERV without structural alterations in proviral genome. Semi-quantitative PCR demonstrated a gradual increase of proviral load in the infected cells. Sequence analysis of the LTR region of PERV from infected cells indicated a relatively low rate (6.0 × 104/bp or about 2 × 106/bp/generation) of mutation. There were also indications of recombination of PERV strains A and B. Finally, PERV infection had no effect on transcription of human endogenous retrovirus-K (HERV-K) genes. Together, no significant effect attributable to PERV infection was evident on chronically PERV-infected HEK-293 cells.Key words: porcine endogenous retrovirus (PERV), human endogenous retrovirus-K (HERV-K), xenotransplantation, zoonosis.
Linking porcine microsatellite markers to known genome regions by identifying their human orthologs
Authors: Jiang Zhihua , Michal Jennifer J
Published: October 2003

Microsatellites, or tandem simple sequence repeats (SSRs), have become one of the most popular molecular markers in genome mapping because of their abundance across genomes and because of their high levels of polymorphism. However, information on which genes surround or flank them has remained very limited for most SSRs, especially in livestock species. In this study, an in silico comparative mapping approach was developed to link porcine SSRs to known genome regions by identifying their human orthologs. From a total of 1321 porcine microsatellites used in this study, 228 were found to have blocks in alignment with human genomic sequences. These 228 SSRs span about 1459 cM of the porcine genome, but with uneven distributions, ranging from 2 on SSC12 to 24 on SSC14. Linking these porcine SSRs to the known genome regions in the human genome also revealed 16 new putative synteny groups between these two species. Fifteen SSRs on SSC3 with identified human orthologs were typed on a pig-hamster radiation hybrid (RH) panel and used in a joint analysis with 80 known gene markers previously mapped on SSC3 using the same panel. The analysis revealed that they were all highly linked to either one or both adjacent markers. These results indicated that assigning the porcine SSRs to known genome regions by identifying their human orthologs is a reliable approach. The process will provide a foundation for positional cloning of causative genes for economically important traits.Key words: pig, microsatellite markers, human orthologs, RH mapping.
Targeted molecular mapping of a major wheat QTL forFusariumhead blight resistance using wheat ESTs and synteny with rice
Authors: Liu Sixin , Anderson James A
Published: October 2003

A major QTL for resistance to Fusarium head blight (FHB) in wheat, Qfhs.ndsu-3BS, has been identified and verified by several research groups. The objective of this study was to increase the marker density in this QTL region using STS (sequence-tagged site) markers developed from wheat expressed sequence tags (ESTs) near Qfhs.ndsu-3BS. Because wheat chromosome 3BS and rice chromosome 1S are syntenous, the sequences of P1-derived artificial chromosome (PAC) and (or) bacterial artificial chromosome (BAC) clones covering the sub-distal portion of rice chromosome 1S were used as queries for a BLASTn search to identify wheat ESTs most likely near Qfhs.ndsu-3BS. Sixty-eight out of 79 STS primer pairs designed from wheat ESTs amplified PCR products from the genomic DNA of Triticum aestivum 'Chinese Spring'. Twenty-eight STS markers were localized on chromosome 3BS by aneuploid analysis. Six out of the nine STS markers that could be mapped in the T. aestivum 'Sumai 3'/T. aestivum 'Stoa' population had higher R2and LOD values for this QTL than the most significant marker reported previously. Therefore, leveraging genome sequence information available in rice for wheat genetics is an effective strategy to develop DNA markers for Qfhs.ndsu-3BS, and this strategy may have broad applications for targeted mapping of other traits in cereal crops.Key words: comparative mapping, genomics.