bluuebunny/crossref_metadata_2025 huggingface dataset:
Probability of First Sexual Maturation of Male Parr in Wild Sea-run Brown Trout (Salmo trutta) Depends on Condition Factor 1 yr in Advance
Authors: Bohlin Torgny , Dellefors Claes , Faremo Ulo
Published: November 2008

In three years, in late autumn, underyearling wild sea-run brown trout (Salmo trutta) in a small stream were captured with electric fishing and tagged with microchips (passive integrated transponders). They were recaptured during the following season either as migrating smolts in a trap or by electric fishing in the stream just after the migration period and during spawning (late autumn). At spawning, they were distinguished as sexually mature male parr or immature juveniles. The smolts were longer and heavier at tagging than the mature male parr and the immature parr, which were similar in initial length and weight. The mature male parr had a significantly higher condition factor at tagging than the immature parr. The probability of parr maturation was positively associated with initial condition factor but not with initial body length. Growth of mature male parr and immature parr was similar in the early season but higher for immature parr in the late season. The result indicated that the choice of strategy was made earlier in life than previously recognized.
Fidelity of Anadromous Arctic Char (Salvelinus alpinus) to Nauyuk Lake, N.W.T., Canada
Authors: Gyselman E. C.
Published: November 2008

The estimated fidelity of anadromous Arctic char (Salvelinus alpinus) returning to Nauyuk Lake from 1974 to 1978 was low (53%). Seven percent of the fish were absent for 1 or 2 yr before returning. Fidelity was also size dependant. Intermediate-sized fish (35–65 cm) had the highest estimated fidelity, while smaller and larger fish had lower rates. The char leaving Nauyuk Lake each spring were categorized into three groups: postspawning char, char that had been observed returning to Nauyuk Lake at least once, and char that had not shown any fidelity to Nauyuk Lake in the past. The char that had shown fidelity to Nauyuk Lake previously had the highest fidelity rate (75%), while the postspawning char and those that had not shown any previous fidelity to Nauyuk Lake both had a fidelity rate of 45%. The low fidelity of the postspawning char was attributed to a higher mortality rate. Fidelity could not be correlated with the length of time a fish was at sea or when it left Nauyuk Lake in the spring.
Sublethal Effects of Tetrachloroguaiacol on Juvenile Rainbow Trout, Oncorhynchus mykiss, following Acute and Chronic Exposure
Authors: Johansen J. A. , Kennedy C. J. , Sweeting R. M. , Farrell A. P. , McKeown B. A.
Published: November 2008

Following either a 24-h (acute) or 25-d (chronic) exposure to tetrachloroguaiacol (TeCG), a component of bleached kraft mill effluent (BKME), juvenile rainbow trout, Oncorhynchus mykiss, were examined for effects on several biochemical parameters, swimming performance, and disease resistance. Acute exposure resulted in increased levels of plasma cortisol and lactate and reductions in liver glycogen and protein, spleen somatic index, leucocrit, hemoglobin, swimming performance, and disease resistance. Chronic exposure resulted in most parameters remaining at control levels with the exception of leucocrit which was elevated, plasma cortisol which decreased, and disease resistance which was impaired. These findings correlate well with a previously proposed classic stress response for mammals and are generally consistent with studies in which fish were exposed to whole BKME. The 96-h LC50 for juvenile rainbow trout exposed to TeCG was estimated at 0.37 mg∙L−1.
Influence of Sustained Exercise at Two Ration Levels on Growth and Thyroid Function of All-Female Chinook Salmon (Oncorhynchus tshawytscha) in Seawater
Authors: Kiessling A. , Higgs D. A. , Dosanjh B. S. , Eales J. G.
Published: November 2008

Duplicate groups of seawater-adapted 70-g all-female chinook salmon (Oncorhynchus tshawytscha) were held in flowing seawater (24–29‰; 8–12 °C) corresponding to swimming speeds (SS) of 0.5, 1.0, or 1.5 body lengths (bl)/s for 212 d. Fish were fed either a maximum satiating ration of 75% of maximum ration at each SS. Fish grew four- to fivefold during the study, but neither mean body weight, fork length, specific growth rate, condition factor, nor muscle morphometry was influenced by average SS. However, the SS of individually marked fish were negatively correlated with specific growth rate. At both rations, higher SS increased the internal tissue-carcass ratio, hepatosomatic index, and total body protein. More food was ingested at higher SS resulting in reduced feed efficiency. SS did not alter the plasma L-thyroxine (T4) concentration, but increased the plasma 3,5,3′-triiodo-L-thyronine (T3) concentration and T3/T4ratio. In part, this may reflect the greater food intake at higher SS. The reduced ration depressed all aspects of growth and at 212 d tended to depress both plasma T4and T3, but did not alter feed efficiency. We conclude that exercise over the range of 0.5–1.5 bl/s does not enhance growth, but reduces feed efficiency in seawater-adapted chinook salmon.
Influence of Larval Gizzard Shad (Dorosoma cepedianum) Density on Piscivory and Growth of Young-of-Year Saugeye (Stizostedion vitreum × S. canadense)
Authors: Stahl Thomas P. , Stein Roy A.
Published: November 2008

Growth and survival of young-of-year saugeye (Stizostedion vitreum ♂ × S. canadense ♀) (stocked into Ohio reservoirs to create sport fisheries) are probably influenced by prey availability, variations in which may account for historically documented variability in stocking success. Because saugeye switch from a diet of zooplankton to fish once stocked, we sought to determine experimentally if saugeye size and available ichthyoplankton, i.e., larval gizzard shad (Dorosoma cepedianum), affected this switch and whether piscivory improved saugeye growth. In an enclosure experiment, saugeye (33.9 mm TL) immediately switched to piscivory when exposed to ichthyoplankton densities of 20 and 100∙m−3, growing faster when more gizzard shad were available. In another enclosure experiment, saugeye 30–49 mm TL consumed 14-mm gizzard shad. In ponds (N = 4 ponds∙treatment−1) containing zooplankton and chironomids, we compared saugeye growth with and without larval gizzard shad and found, as in the first enclosure experiment, that piscivory improved saugeye growth. Neither saugeye size nor ichthyoplankton density influenced how quickly saugeye switched to piscivory. We conclude that managers should stock saugeye ≥ 30 mm 1–2 wk before peak ichthyoplankton densities to improve saugeye growth and survival by enhancing opportunities for exploitation of young-of-year gizzard shad.
Abiotic and Seasonal Factors Influencing Trace Metal Levels (Cd, Cu, Ni, Pb, and Zn) in the Freshwater AmphipodGammarus fasciatusin Two Fluvial Lakes of the St. Lawrence River
Authors: Amyot Marc , Pinel-Alloul Bernadette , Campbell Peter G. C.
Published: November 2008

The potential use of the freshwater amphipod Gammarus fasciatus as a biomonitor of metal pollution has been assessed in two fluvial lakes of the St. Lawrence River. Metal (Cd, Cu, Fe, Mn, Ni, Pb, and Zn) concentrations were measured twice at 22 sites in Lakes St. Pierre and St. Louis, both in oxic sediments and in amphipods. Concentrations of free-metal ions at the sediment–water interface were estimated from lake water pH and sediment/water sorption equilibria. Multiple linear regression models forecasting trace metal (Cd, Cu, Ni, Pb, and Zn) levels in amphipods were developed, using abiotic variables (sediment-bound metals, sediment organic carbon, free-metal ions, hydrogen ions, dissolved calcium, and dissolved organic carbon) and biotic (size class) variables. These models explained 73–81% of the observed variation, except in the case of Zn (68%) and Cu (61%), indicating that G. fasciatus is a promising biomonitor for Cd, Ni, and Pb in littoral environments. Seasonal patterns of amphipod contamination were identified for Fe, Ni, and Pb, summer concentrations being higher than those measured during the fall. Size-dependent variation in amphipod metal levels was found, smaller organisms being more contaminated than larger ones.
Long-term Influence of Water Temperature, Photoperiod, and Food Deprivation on Metamorphosis of Sea Lamprey, Petromyzon marinus
Authors: Holmes J. A. , Beamish F. W. H. , Seelye J. G. , Sower S. A. , Youson J. H.
Published: November 2008

After 11 mo in the laboratory, significantly more sea lamprey, Petromyzon marinus, larvae from the Chippewa River, Michigan, metamorphosed in an ambient temperature regime (3 ± 2 animals∙tank−1) compared with a fixed 21 °C temperature (0 animals); photoperiod and food deprivation did not have detectable effects on the incidence of metamorphosis. Metamorphosing animals in our laboratory study were significantly smaller in size (length and weight) and had a lower condition factor (CF) than animals from the same population that metamorphosed a year earlier under field and shorter term laboratory conditions. We also predicted, using criteria of 120 mm, 3.0 g, and a CF of 1.50, that 12 and 14% of the animals in the ambient and fixed temperature regimes, respectively, would metamorphose. Our prediction for the ambient temperature did not differ significantly from observed (11%). We suggest that larvae in landlocked populations of sea lamprey that are at least 120 mm long, weigh 3.0 g, and have a CF of 1.50 or greater in the fall can be predicted to metamorphose the following summer. Furthermore, our data show that low temperature during the winter followed by rising temperature in the spring is the primary environmental cue initiating metamorphosis in sea lamprey.
Relationships between Mercury Concentrations in Walleye (Stizostedion vitreum) and Northern Pike (Esox lucius): Implications for Modelling and Biomonitoring
Authors: Parks J. W. , Craig P. C. , Ozburn G. W.
Published: November 2008

Site-specific and interlake models are developed and tested for predicting mercury levels in walleye (Stizostedion vitreum) and northern pike (Esox lucius). The models are based on empirical relationships from coexisting fish in waters impacted by atmospheric loadings, contaminated sediments, and new reservoir formations. The sizes of fish used in the model (39-cm walleye and 55-cm northern pike) are typical of those caught by sport and commercial fishermen. The relative importance of a number of environmental factors to the accumulation of mercury in coexisting populations was examined by regression of the Biotic Mercury Partitioning Index (BMPI: mercury in species 1 (39-cm walleye)/mercury in species 2 (55-cm northern pike)) on pH, alkalinity, dissolved organic carbon, and other variables that have been identified as important to the accumulation of mercury in either or both species. No species-specific differences in mercury bioavailability were identified. We postulate that development of other biotic relationships on a site-specific, watershed, or broader geographic basis will assist in attempts to model mercury in aquatic ecosystems and reduce sample requirements for biomonitoring programs.
MACROSCOPIC OBSERVABLES AND THE BORN RULE, I: LONG RUN FREQUENCIES
Authors: LANDSMAN N. P.
Published: November 2008

We clarify the role of the Born rule in the Copenhagen Interpretation of quantum mechanics by deriving it from Bohr's doctrine of classical concepts, translated into the following mathematical statement: a quantum system described by a noncommutative C*-algebra of observables is empirically accessible only through associated commutative C*-algebras. The Born probabilities emerge as the relative frequencies of outcomes in long runs of measurements on a quantum system; it is not necessary to adopt the frequency interpretation of single-case probabilities (which will be the subject of a sequel paper). Our derivation of the Born rule uses ideas from a program begun by Finkelstein [17] and Hartle [21], intending to remove the Born rule as a separate postulate of quantum mechanics. Mathematically speaking, our approach refines previous elaborations of this program — notably the one due to Farhi, Goldstone, and Gutmann [15] as completed by Van Wesep [50] — in replacing infinite tensor products of Hilbert spaces by continuous fields of C*-algebras. Furthermore, instead of relying on the controversial eigenstate-eigenvalue link in quantum theory, our derivation just assumes that pure states in classical physics have the usual interpretation as truthmakers that assign sharp values to observables.
SEMICLASSICAL ANALYSIS FOR SPECTRAL SHIFT FUNCTIONS IN MAGNETIC SCATTERING BY TWO SOLENOIDAL FIELDS
Authors: TAMURA HIDEO
Published: November 2008

We study the Aharonov–Bohm effect through the semiclassical analysis for the spectral shift function and its derivative in magnetic scattering by two solenoidal fields in two dimensions, assuming that the total magnetic flux vanishes. The corresponding classical system has a trajectory oscillating between the centers of two solenoidal fields. The emphasis is placed on analyzing how the trapping effect is reflected in the semiclassical asymptotic formula. We also make a comment on the case of scattering by a finite number of solenoidal fields and discuss the relation between the Aharonov–Bohm effect from quantum mechanics and the trapping effect from classical mechanics.
ABELIAN TODA SOLITONS REVISITED
Authors: NIROV KH. S. , RAZUMOV A. V.
Published: November 2008

We present a systematic and detailed review of the application of the method of Hirota and the rational dressing method to abelian Toda systems associated with the untwisted loop groups of complex general linear groups. Emphasizing the rational dressing method, we compare the soliton solutions constructed within these two approaches, and show that the solutions obtained by the Hirota's method are a subset of those obtained by the rational dressing method.
AN ANALYTIC APPROACH TO TURAEV'S SHADOW INVARIANT
Authors: HAHN ATLE
Published: November 2008

In the present paper, we extend the "torus gauge fixing" approach by Blau and Thompson, which was developed in [10] for the study of Chern–Simons models with base manifolds M of the form M = Σ × S1, in a suitable way. We arrive at a heuristic path integral formula for the Wilson loop observables associated to general links in M. We then show that the right-hand side of this formula can be evaluated explicitly in a non-perturbative way and that this evaluation naturally leads to the face models in terms of which Turaev's shadow invariant is defined.
FIBER QUADRISECANTS IN KNOT ISOTOPIES
Authors: FIEDLER T. , KURLIN V.
Published: November 2008

Fix a straight line L in Euclidean 3-space and consider the fibration of the complement of L by half-planes. A generic knot K in the complement of L has neither fiber quadrisecants nor fiber extreme secants such that K touches the corresponding half-plane at 2 points. Both types of secants occur in generic isotopies of knots. We give lower bounds for the number of these fiber secants in all isotopies connecting given isotopic knots. The bounds are expressed in terms of invariants calculable in linear time with respect to the number of crossings.
Activation of estrogen response elements is mediated both via estrogen and muscle contractions in rat skeletal muscle myotubes
Authors: Wiik A. , Hellsten Y. , Berthelson P. , Lundholm L. , Fischer H. , Jansson E.
Published: November 2008

The aim of the present study was to investigate the activation of estrogen response elements (EREs) by estrogen and muscle contractions in rat myotubes in culture and to assess whether the activation is dependent on the estrogen receptors (ERs). In addition, the effect of estrogen and contraction on the mRNA levels of ERα and ERβ was studied to determine the functional consequence of the transactivation. Myoblasts were isolated from rat skeletal muscle and transfected with a vector consisting of sequences of EREs coupled to the gene for luciferase. The transfected myoblasts were then differentiated into myotubes and subjected to either estrogen or electrical stimulation. Activation of the ERE sequence was determined by measurement of luciferase activity. The results show that both ERα and ERβ are expressed in myotubes from rats. Both estrogen stimulation and muscle contraction increased ( P < 0.05) transactivation of the ERE sequence and enhanced ERβ mRNA, whereas ERα was unaffected by estrogen and attenuated ( P < 0.05) by muscle contraction. Use of ER antagonists showed that, whereas the estrogen-induced transactivation is mediated via ERs, the effect of muscle contraction is ER independent. The muscle contraction-induced transactivation of ERE and increase in ERβ mRNA were instead found to be MAP kinase (MAPK) dependent. This study demonstrates for the first time that muscle contractions have a similar functional effect as estrogen in skeletal muscle myotubes, causing ERE activation and an enhancement in ERβ mRNA. However, in contrast to estrogen, the effect is independent of ERs and dependent on MAPK, suggesting activation via the estrogen related receptor (ERR).
Histone H3 as a novel substrate for MAP kinase phosphatase-1
Authors: Kinney Corttrell M. , Chandrasekharan Unni M. , Yang Lin , Shen Jianzhong , Kinter Michael , McDermott Michael S. , DiCorleto Paul E.
Published: November 2008

Mitogen-activated protein (MAP) kinase phosphatase-1 (MKP-1) is a nuclear, dual-specificity phosphatase that has been shown to dephosphorylate MAP kinases. We used a “substrate-trap” technique involving a mutation in MKP-1 of the catalytically critical cysteine to a serine residue (“CS” mutant) to capture novel MKP-1 substrates. We transfected the MKP-1 (CS) mutant and control (wild-type, WT) constructs into phorbol 12-myristate 13-acetate (PMA)-activated COS-1 cells. MKP-1-substrate complexes were immunoprecipitated, which yielded four bands of 17, 15, 14, and 10 kDa with the CS MKP-1 mutant but not the WT MKP-1. The bands were identified by mass spectrometry as histones H3, H2B, H2A, and H4, respectively. Histone H3 was phosphorylated, and purified MKP-1 dephosphorylated histone H3 (phospho-Ser-10) in vitro; whereas, histone H3 (phospho-Thr-3) was unaffected. We have previously shown that thrombin and vascular endothelial growth factor (VEGF) upregulated MKP-1 in human endothelial cells (EC). We now show that both thrombin and VEGF caused dephosphorylation of histone H3 (phospho-Ser-10) and histone H3 (phospho-Thr-3) in EC with kinetics consistent with MKP-1 induction. Furthermore, MKP-1-specific small interfering RNA (siRNA) prevented VEGF- and thrombin-induced H3 (phospho-Ser-10) dephosphorylation but had no effect on H3 (phospho-Thr-3 or Thr-11) dephosphorylation. In summary, histone H3 is a novel substrate of MKP-1, and VEGF- and thrombin-induced H3 (phospho-Ser-10) dephosphorylation requires MKP-1. We propose that MKP-1-mediated H3 (phospho-Ser-10) dephosphorylation is a key regulatory step in EC activation by VEGF and thrombin.
Requirement of Notch activation during regeneration of the intestinal epithelia
Authors: Okamoto Ryuichi , Tsuchiya Kiichiro , Nemoto Yasuhiro , Akiyama Junko , Nakamura Tetsuya , Kanai Takanori , Watanabe Mamoru
Published: November 2008

Notch signaling regulates cell differentiation and proliferation, contributing to the maintenance of diverse tissues including the intestinal epithelia. However, its role in tissue regeneration is less understood. Here, we show that Notch signaling is activated in a greater number of intestinal epithelial cells in the inflamed mucosa of colitis. Inhibition of Notch activation in vivo using a γ-secretase inhibitor resulted in a severe exacerbation of the colitis attributable to the loss of the regenerative response within the epithelial layer. Activation of Notch supported epithelial regeneration by suppressing goblet cell differentiation, but it also promoted cell proliferation, as shown in in vivo and in vitro studies. By utilizing tetracycline-dependent gene expression and microarray analysis, we identified a novel group of genes that are regulated downstream of Notch1 within intestinal epithelial cells, including PLA2G2A, an antimicrobial peptide secreted by Paneth cells. Finally, we show that these functions of activated Notch1 are present in the mucosa of ulcerative colitis, mediating cell proliferation, goblet cell depletion, and ectopic expression of PLA2G2A, thereby contributing to the regeneration of the damaged epithelia. This study showed the critical involvement of Notch signaling during intestinal tissue regeneration, regulating differentiation, proliferation, and antimicrobial response of the epithelial cells. Thus Notch signaling is a key intracellular molecular pathway for the proper reconstruction of the intestinal epithelia.
Chronic intermittent hypoxia impairs heart rate responses to AMPA and NMDA and induces loss of glutamate receptor neurons in nucleus ambiguus of F344 rats
Authors: Yan Binbin , Li Lihua , Harden Scott W. , Gozal David , Lin Ying , Wead William B. , Wurster Robert D. , Cheng Zixi (Jack)
Published: November 2008

Chronic intermittent hypoxia (CIH), as occurs in sleep apnea, impairs baroreflex-mediated reductions in heart rate (HR) and enhances HR responses to electrical stimulation of vagal efferent. We tested the hypotheses that HR responses to activation of α-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) and N-methyl-d-aspartate (NMDA) receptors in the nucleus ambiguus (NA) are reduced in CIH-exposed rats and that this impairment is associated with degeneration of glutamate receptor (GluR)-immunoreactive NA neurons. Fischer 344 rats (3–4 mo) were exposed to room air (RA) or CIH for 35–50 days ( n = 18/group). At the end of the exposures, AMPA (4 pmol, 20 nl) and NMDA (80 pmol, 20 nl) were microinjected into the same location of the left NA (−200 μm to +200 μm relative to caudal end of area postrema; n = 6/group), and HR and arterial blood pressure responses were measured. In addition, brain stem sections at the level of −800, −400, 0, +400, and +800 μm relative to obex were processed for AMPA and NMDA receptor immunohistochemistry. The number of NA neurons expressing AMPA receptors and NMDA receptors (NMDARs) was quantified. Compared with RA, we found that after CIH 1) HR responses to microinjection of AMPA into the left NA were reduced (RA −290 ± 30 vs. CIH −227 ± 15 beats/min, P < 0.05); 2) HR responses to microinjection of NMDA into the left NA were reduced (RA −302 ± 16 vs. CIH −238 ± 27 beats/min, P < 0.05); and 3) the number of NMDAR1, AMPA GluR1, and AMPA GluR2/3-immunoreactive cells in the NA was reduced ( P < 0.05). These results suggest that degeneration of NA neurons expressing GluRs contributes to impaired baroreflex control of HR in rats exposed to CIH.
Characterization of Dent's disease mutations of CLC-5 reveals a correlation between functional and cell biological consequences and protein structure
Authors: Smith Andrew J. , Reed Anita A. C. , Loh Nellie Y. , Thakker Rajesh V. , Lippiat Jonathan D.
Published: November 2008

Mutations of the human CLCN5 gene, which encodes the CLC-5 Cl−/H+exchanger, lead to Dent's disease. Mutations result in functional defects that range from moderate reductions to complete loss of whole cell currents, although the severity of the functional defect rarely correlates with the severity of the disease. To further elucidate the basis of CLC-5 mutations causing Dent's disease, we examined the functional and cell biological consequences of seven previously reported missense mutants, utilizing electrophysiological and cell biological techniques. This revealed three classes of Dent's disease-causing CLC-5 mutations. Class 1 mutations lead to endoplasmic reticulum retention and degradation of CLC-5. Class 2 mutations appear to have little effect on subcellular distribution of CLC-5 but cause defective function resulting in severe defects in endosomal acidification. Class 3 mutations lead to alterations in the endosomal distribution of CLC-5 but are otherwise able to support endosomal acidification. Molecular modeling demonstrates a structural basis that may underlie the nature of the defect resulting from each mutation with each class occupying discrete regions of the protein quaternary structure. Thus these results demonstrate that the cell biological consequences of CLC-5 mutations are heterogeneous and can be classified into three major groups and that a correlation between the nature of the defect and the location of the mutation in the structure may be drawn. This model may prove to be useful as a tool to aid in the diagnosis and future therapeutic intervention of the disease.
Dense-core vesicle proteins IA-2 and IA-2β affect renin synthesis and secretion through the β-adrenergic pathway
Authors: Kim Soo Mi , Theilig Franziska , Qin Yan , Cai Tao , Mizel Diane , Faulhaber-Walter Robert , Hirai Hiroki , Bachmann Sebastian , Briggs Josephine P. , Notkins Abner L. , Schnermann Jurgen
Published: November 2008

IA-2 and IA-2β, major autoantigens in type 1 diabetes, are transmembrane proteins in dense-core vesicles, and their expression influences the secretion of hormones and neurotransmitters. The present experiments were performed to examine whether IA-2 and IA-2β modulate the release of renin from dense-core vesicles of juxtaglomerular granular cells in the kidney. Plasma renin concentration (PRC; ng angiotensin I·ml−1·h−1) was significantly reduced in mice with null mutations in IA-2, IA-2β, or both IA-2 and IA-2β compared with wild-type mice (876 ± 113, 962 ± 130, and 596 ± 82 vs. 1,367 ± 93; P < 0.01, P < 0.02, and P < 0.001). Renin mRNA levels were reduced to 26.4 ± 5.1, 39 ± 5.4, and 35.3 ± 5.5% of wild-type in IA-2−/−, IA-2β−/−, and IA-2/IA-2β−/− mice. Plasma aldosterone levels were not significantly different among genotypes. The regulation of PRC by furosemide and salt intake, and of aldosterone by salt intake, was maintained in all genotypes. IA-2 and IA-2β expression did not colocalize with renin but showed overlapping immunoreactivity with tyrosine hydroxylase. While propranolol reduced PRC in wild-type mice, it had no effect on PRC in IA-2/ IA-2β−/− mice. Renal tyrosine hydroxylase mRNA and immunoreactivity were reduced in IA-2/IA-2β−/− mice as was the urinary excretion of catecholamines. We conclude that IA-2 and IA-2β are required to maintain normal levels of renin expression and renin release, most likely by permitting normal rates of catecholamine release from sympathetic nerve terminals.
Hypophagia induced by glucocorticoid deficiency is associated with an increased activation of satiety-related responses
Authors: Uchoa Ernane Torres , Sabino Henrique Augusto C. , Ruginsk Silvia Graciela , Antunes-Rodrigues Jose , Elias Lucila Leico K.
Published: November 2008

Glucocorticoids have major effects on food intake, demonstrated by the decrease of food intake following adrenalectomy. Satiety signals are relayed to the nucleus of the solitary tract (NTS), which has reciprocal projections with the arcuate nucleus (ARC) and paraventricular nucleus (PVN) of the hypothalamus. We evaluated the effects of glucocorticoids on the activation of hypothalamic and NTS neurons induced by food intake in rats subjected to adrenalectomy (ADX) or sham surgery 7 days before the experiments. One-half of ADX animals received corticosterone (ADX+B) in the drinking water (B: 25 mg/l). Fos/tyrosine hydroxylase (TH), Fos/corticotrophin-releasing factor (CRF) and Fos immunoreactivity were assessed in the NTS, PVN, and ARC, respectively. Food intake and body weight were reduced in the ADX group compared with sham and ADX+B groups. Fos and Fos/TH in the NTS, Fos, and Fos/CRF immunoreactive neurons in the PVN and Fos in the ARC were increased after refeeding, with higher number in the ADX group, compared with sham and ADX+B groups. CCK administration showed no hypophagic effect on ADX group despite a similar increase of Fos/TH immunoreactive neurons in the NTS compared with sham and ADX+B groups, suggesting that CCK alone cannot further increase the anorexigenic effect induced by glucocorticoid deficiency. The present data indicate that glucocorticoid withdrawal reduced food intake, which was associated with higher activation of ARC, CRF neurons of the PVN, and catecholaminergic neurons of the NTS. In the absence of glucocorticoids, satiety signals elicited during a meal lead to an augmented activation of brain stem and hypothalamic pathways.
The telomerase tale in vascular aging: regulation by estrogens and nitric oxide signaling
Authors: Farsetti Antonella , Grasselli Annalisa , Bacchetti Silvia , Gaetano Carlo , Capogrossi Maurizio C.
Published: November 2008

Hormones and nitric oxide (NO), a free radical, are ancestral molecules, conserved through evolution, that modulate many aspects of the physiology and pathophysiology of living organisms by regulating transcription of genes involved in development, metabolism, and differentiation. Of interest, both estrogen and NO signaling, specifically through the estrogen receptor-α (ERα) and the endothelial isoform of the nitric oxide synthase (eNOS), have been shown to counteract endothelial senescence through a shared downstream effector, the catalytic subunit of human telomerase (hTERT), a key molecule in the aging process. Since aging is the first and most relevant risk factor in cardiovascular diseases, it is tempting to speculate that hTERT may be at the cross point between the NO and estrogen pathways. The present review will focus on the evolutionary and molecular aspects linking eNOS, ERs, and hTERT in counteracting the process of endothelial cell aging.
Visuomotor Adaptation Does Not Recalibrate Kinesthetic Sense of Felt Hand Path
Authors: Wong Teser , Henriques Denise Y. P.
Published: November 2008

Motor control relies on multiple sources of information. To estimate the position and motion of the hand, the brain uses both vision and body-position (proprioception and kinesthesia) senses from sensors in the muscles, tendons, joints, and skin. Although performance is better when more than one sensory modality is present, visuomotor adaptation suggests that people tend to rely much more on visual information of the hand to guide their arm movements to targets, even when the visual information and kinesthetic information about the hand motion are in conflict. The aim of this study is to test whether adapting hand movements in response to false visual feedback of the hand will result in the change or recalibration of the kinesthetic sense of hand motion. The advantage of this cross-sensory recalibration would ensure on-line consistency between the senses. To test this, we mapped participants' sensitivity to tilted and curved hand paths and then examined whether adapting their hand movements in response to false visual feedback affected their felt sense of hand path. We found that participants could accurately estimate hand path directions and curvature after adapting to false visual feedback of their hand when reaching to targets. Our results suggest that although vision can override kinesthesia to recalibrate arm motor commands, it does not recalibrate the kinesthetic sense of hand path geometry.
Relevance of Error: What Drives Motor Adaptation?
Authors: Wei Kunlin , Körding Konrad
Published: November 2008

During motor adaptation the nervous system constantly uses error information to improve future movements. Today's mainstream models simply assume that the nervous system adapts linearly and proportionally to errors. However, not all movement errors are relevant to our own action. The environment may transiently disturb the movement production—for example, a gust of wind blows the tennis ball away from its intended trajectory. Apparently the nervous system should not adapt its motor plan in the subsequent tennis strokes based on this irrelevant movement error. We hypothesize that the nervous system estimates the relevance of each observed error and adapts strongly only to relevant errors. Here we present a Bayesian treatment of this problem. The model calculates how likely an error is relevant to the motor plant and derives an ideal adaptation strategy that leads to the most precise movements. This model predicts that adaptation should be a nonlinear function of the size of an error. In reaching experiments we found strong evidence for the predicted nonlinear strategy. The model also explains published data on saccadic gain adaptation, adaptation to visuomotor rotations, and force perturbations. Our study suggests that the nervous system constantly and effortlessly estimates the relevance of observed movement errors for successful motor adaptation.
Quantifying Neural Coding of Event Timing
Authors: Soteropoulos Demetris S. , Baker Stuart N.
Published: November 2008

Single-neuron firing is often analyzed relative to an external event, such as successful task performance or the delivery of a stimulus. The perievent time histogram (PETH) examines how, on average, neural firing modulates before and after the alignment event. However, the PETH contains no information about the single-trial reliability of the neural response, which is important from the perspective of a target neuron. In this study, we propose the concept of using the neural activity to predict the timing of the occurrence of an event, as opposed to using the event to predict the neural response. We first estimate the likelihood of an observed spike train, under the assumption that it was generated by an inhomogeneous gamma process with rate profile similar to the PETH shifted by a small time. This is used to generate a probability distribution of the event occurrence, using Bayes’ rule. By an information theoretic approach, this method yields a single value (in bits) that quantifies the reduction in uncertainty regarding the time of an external event following observation of the spike train. We show that the approach is sensitive to the amplitude of a response, to the level of baseline firing, and to the consistency of a response between trials, all of which are factors that will influence a neuron's ability to code for the time of the event. The technique can provide a useful means not only of determining which of several behavioral events a cell encodes best, but also of permitting objective comparison of different cell populations.
Fischer‐Tropsch Synthesis over Iron Manganese Catalysts: Effect of Preparation and Operating Conditions on Catalyst Performance
Authors: Mirzaei Ali A. , Vahid Samaneh , Feyzi Mostafa
Published: November 2008

Iron manganese oxides are prepared using a coprecipitation procedure and studied for the conversion of synthesis gas to light olefins and hydrocarbons. In particular, the effect of a range of preparation variables such
as [Fe]/[Mn] molar ratios of the precipitation solution, pH of precipitation, temperature of precipitation,
and precipitate aging times was investigated in detail. The results are interpreted in terms of the structure of
the active catalyst and it has been generally concluded that the calcined catalyst
(at 650 ∘C for 6 hours) containing 50%Fe/50%Mn‐on
molar basis which is the most active catalyst for the conversion of synthesis gas to light olefins.
The effects of different promoters and supports with loading of optimum support on the catalytic performance of catalysts are also studied. It was found that the catalyst containing 50%Fe/50%Mn/5 wt.%Al2O3 is an optimum‐modified catalyst. The catalytic performance of optimal catalyst has been studied in operation conditions such as a range of reaction temperatures, H2/CO molar feed ratios and a range of total pressures. Characterization of both precursors and calcined catalysts is carried out by powder X‐ray diffraction (XRD), scanning electron microscopy (SEM), BET specific surface area and thermal analysis methods such as TGA and DSC.
Blow Flies Visiting Decaying Alligators: Is Succession Synchronous or Asynchronous?
Authors: Nelder Mark P. , McCreadie John W. , Major Clinton S.
Published: November 2008

Succession patterns of adult blow flies (Diptera: Calliphoridae) on decaying alligators were investigated in Mobile (Ala, USA) during August 2002. The most abundant blow fly species visiting the carcasses wereChrysomya rufifacies(Macquart),Cochliomyia macellaria(Fabricus),Chrysomya megacephala(Fabricus),Phormia regina(Meigen), andLucilia coeruleiviridis(Macquart).Lucilia coeruleiviridiswas collected more often during the early stages of decomposition, followed byChrysomyaspp.,Cochliomyia macellaria, andPhormia reginain the later stages.Lucilia coeruleiviridiswas the only synchronous blow fly on the three carcasses; other blow fly species exhibited only site-specific synchrony. Using dichotomous correlations and analyses of variance, we demonstrated that blow fly-community succession was asynchronous among three alligators; however, Monte Carlo simulations indicate that there was some degree of synchrony between the carcasses.
Automatic Estimation of the Dynamics of Channel Conductance Using a Recurrent Neural Network
Authors: Takahashi Masaaki , Natsume Kiyohisa
Published: November 2008

In order to simulate neuronal electrical activities, we must estimate the dynamics of channel conductances from physiological experimental data. However, this approach requires the formulation of differential equations that express the time course of channel conductance. On the other hand, if the dynamics are automatically estimated, neuronal activities can be easily simulated. By using a recurrent neural network (RNN), it is possible to estimate the dynamics of channel conductances without formulating the differential equations. In the present study, we estimated the dynamics of the Na+ and K+ conductances of a squid giant axon using two different fully connected RNNs and were able to reproduce various neuronal activities of the axon. The reproduced activities were an action potential, a threshold, a refractory phenomenon, a rebound action potential, and periodic action potentials with a constant stimulation. RNNs can be trained using channels other than the Na+ and K+ channels. Therefore, using our RNN estimation method, the dynamics of channel conductance can be automatically estimated and the neuronal activities can be simulated using the channel RNNs. An RNN can be a useful tool to estimate the dynamics of the channel conductance of a neuron, and by using the method presented here, it is possible to simulate neuronal activities more easily than by using the previous methods.
Downscaling Climate over Complex Terrain: High Finescale (<1000 m) Spatial Variation of Near-Ground Temperatures in a Montane Forested Landscape (Great Smoky Mountains)*
Authors: Fridley Jason D.
Published: November 2008

Landscape-driven microclimates in mountainous terrain pose significant obstacles to predicting the response of organisms to atmospheric warming, but few if any studies have documented the extent of such finescale variation over large regions. This paper demonstrates that ground-level temperature regimes in Great Smoky Mountains National Park (Tennessee and North Carolina) vary considerably over fine spatial scales and are only partially linked to synoptic weather patterns and environmental lapse rates. A 120-sensor network deployed across two watersheds in 2005–06 exhibited finescale (<1000-m extent) temperature differences of over 2°C for daily minima and over 4°C for daily maxima. Landscape controls over minimum temperatures were associated with finescale patterns of soil moisture content, and maximum temperatures were associated with finescale insolation differences caused by topographic exposure and vegetation cover. By linking the sensor array data to 10 regional weather stations and topographic variables describing site radiation load and moisture content, multilevel spatial models of 30-m resolution were constructed to map daily temperatures across the 2090-km2 park, validated with an independent 50-sensor network. Maps reveal that different landscape positions do not maintain relative differences in temperature regimes across seasons. Near-stream locations are warmer in the winter and cooler in the summer, and sites of low elevation more closely track synoptic weather patterns than do wetter high-elevation sites. This study suggests a strong interplay between near-ground heat and water balances and indicates that the influence of past and future shifts in regional temperatures on the park’s biota may be buffered by soil moisture surfeits from high regional rainfall.
Observed 1970–2005 Cooling of Summer Daytime Temperatures in Coastal California
Authors: Lebassi Bereket , González Jorge , Fabris Drazen , Maurer Edwin , Miller Norman , Milesi Cristina , Switzer Paul , Bornstein Robert
Published: November 2008

This study evaluated 1950–2005 summer [June–August (JJA)] mean monthly air temperatures for two California air basins: the South Coast Air Basin (SoCAB) and the San Francisco Bay Area (SFBA). The study focuses on the more rapid post-1970 warming period, and its daily minima temperature Tmin and maxima temperature Tmax values were used to produce average monthly values and spatial distributions of trends for each air basin. Additional analyses included concurrent SSTs, 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) sea level coastal pressure gradients, and GCM-downscaled average temperature Tave values.

Results for all 253 California National Weather Service (NWS) Cooperative Observer Program (COOP) sites together showed increased Tave values (0.23°C decade−1); asymmetric warming, as Tmin values increase faster than Tmax values (0.27° versus 0.04°C decade−1) and thus decreased daily temperature range (DTR) values (0.15°C decade−1). The spatial distribution of observed SoCAB and SFBA Tmax values exhibited a complex pattern, with cooling (−0.30°C decade−1) in low-elevation coastal areas open to marine air penetration and warming (0.32°C decade−1) in inland areas. Results also showed that decreased DTR values in the basins arose from small increases at inland sites (0.16°C decade−1) combined with large decreases (−0.58°C decade−1) at coastal sites. It is also possible that some of the current observed temperature trends could be associated with low-frequency decadal variability, expected even with a constant radiative forcing.

Previous studies suggest that cooling JJA Tmax values in coastal California were a result of increased irrigation, coastal upwelling, or cloud cover. The current hypothesis is that they arise (as a possible “reverse reaction”) from the global warming of inland areas, which results in increased sea-breeze flow activity. GCM model Tave warming decreased from 0.13°C decade−1 at inland sites to 0.08°C decade−1 in coastal areas. Sea level pressure increased in the Pacific high and decreased in the thermal low. The corresponding gradient thus showed a trend of 0.04 hPa 100 km−1 decade−1, supportive of the hypothesis of increased sea-breeze activity.
Arctic Cloud Fraction and Radiative Fluxes in Atmospheric Reanalyses
Authors: Walsh John E. , Chapman William L. , Portis Diane H.
Published: November 2008

Arctic radiative fluxes, cloud fraction, and cloud radiative forcing are evaluated from four currently available reanalysis models using data from the North Slope of Alaska (NSA) Barrow site of the Atmospheric Radiation Measurement Program (ARM). A primary objective of the ARM–NSA program is to provide a high-resolution dataset of direct measurements of Arctic clouds and radiation so that global climate models can better parameterize high-latitude cloud radiative processes. The four reanalysis models used in this study are the 1) NCEP–NCAR global reanalysis, 2) 40-yr ECMWF Re-Analysis (ERA-40), 3) NCEP–NCAR North American Regional Reanalysis (NARR), and 4) Japan Meteorological Agency and Central Research Institute of Electric Power Industry 25-yr Reanalysis (JRA25). The reanalysis models simulate the radiative fluxes well if/when the cloud fraction is simulated correctly. However, the systematic errors of climatological reanalysis cloud fractions are substantial. Cloud fraction and radiation biases show considerable scatter, both in the annual mean and over a seasonal cycle, when compared to those observed at the ARM–NSA. Large seasonal cloud fraction biases have significant impacts on the surface energy budget. Detailed comparisons of ARM and reanalysis products reveal that the persistent low-level cloud fraction in summer is particularly difficult for the reanalysis models to capture creating biases in the shortwave radiation flux that can exceed 160 W m−2. ERA-40 is the best performer in both shortwave and longwave flux seasonal representations at Barrow, largely because its simulation of the cloud coverage is the most realistic of the four reanalyses. Only two reanalyses (ERA-40 and NARR) capture the observed transition from positive to negative surface net cloud radiative forcing during a 2–3-month period in summer, while the remaining reanalyses indicate a net warming impact of Arctic clouds on the surface energy budget throughout the entire year. The authors present a variable cloud radiative forcing metric to diagnose the erroneous impact of reanalysis cloud fraction on the surface energy balance. The misrepresentations of cloud radiative forcing in some of the reanalyses are attributable to errors in both simulated cloud amounts and the models’ radiative response to partly cloudy conditions.
Hindcasts of Tropical Atlantic SST Gradient and South American Precipitation: The Influences of the ENSO Forcing and the Atlantic Preconditioning
Authors: Huang Huei-Ping , Robertson Andrew W. , Kushnir Yochanan , Peng Shiling
Published: November 2008

Hindcast experiments for the tropical Atlantic sea surface temperature (SST) gradient G1, defined as tropical North Atlantic SST anomaly minus tropical South Atlantic SST anomaly, are performed using an atmospheric general circulation model coupled to a mixed layer ocean over the Atlantic to quantify the contributions of the El Niño–Southern Oscillation (ENSO) forcing and the preconditioning in the Atlantic to G1 in boreal spring. The results confirm previous observational analyses that, in the years with a persistent ENSO SST anomaly from boreal winter to spring, the ENSO forcing plays a primary role in determining the tendency of G1 from winter to spring and the sign of G1 in late spring. In the hindcasts, the initial perturbations in Atlantic SST in boreal winter are found to generally persist beyond a season, leaving a secondary but nonnegligible contribution to the predicted Atlantic SST gradient in spring. For 1993/94, a neutral year with a large preexisting G1 in winter, the hindcast using the information of Atlantic preconditioning alone is found to reproduce the observed G1 in spring. The seasonal predictability in precipitation over South America is examined in the hindcast experiments. For the recent events that can be validated with high-quality observations, the hindcasts produced dryness in boreal spring 1983, wetness in spring 1996, and wetness in spring 1994 over northern Brazil that are qualitatively consistent with observations. An inclusion of the Atlantic preconditioning is found to help the prediction of South American rainfall in boreal spring. For the ENSO years, discrepancies remain between the hindcast and observed precipitation anomalies over northern and equatorial South America, an error that is partially attributed to the biased atmospheric response to ENSO forcing in the model. The hindcast of the 1993/94 neutral year does not suffer this error. It constitutes an intriguing example of useful seasonal forecast of G1 and South American rainfall anomalies without ENSO.