bluuebunny/crossref_metadata_2025 huggingface dataset:
Temporal Dynamics of Neural Adaptation Effect in the Human Visual Ventral Stream
Authors: Noguchi Yasuki , Inui Koji , Kakigi Ryusuke
Published: July 2004

When the same visual stimulus is repeatedly presented with a brief interval, the brain responses to that stimulus are attenuated relative to those at first presentation [neural adaptation (NA)]. Although this effect has been widely observed in various regions of human brain, its temporal dynamics as a neuronal population has been mostly unclear. In the present study, we used a magnetoencephalography (MEG) and conducted a macrolevel investigation of the temporal profiles of the NA occurring in the human visual ventral stream. The combination of MEG with our previous random dot blinking method isolated the neural responses in the higher visual cortex relating to shape perception. We dissociated three dimensions of the NA: activation strength, peak latency, and temporal duration of neural response. The results revealed that visual responses to the repeated compared with novel stimulus showed a significant reduction in both activation strength and peak latency but not in the duration of neural processing. Furthermore, this acceleration of peak latency showed a significant correlation with reaction time of the subjects, whereas no correlation was found between the reaction time and the temporal duration of neural responses. These results indicate that (1) the NA involves the brain response changes in the temporal domain as well as the response attenuation reported previously, and (2) this temporal change is primarily observed as a rapid rising of “what” responses, rather than a temporal shortening of neural response curves within the visual ventral stream as considered previously.
Src Family Kinases Are Involved in EphA Receptor-Mediated Retinal Axon Guidance
Authors: Knöll Bernd , Drescher Uwe
Published: July 2004

EphA receptor tyrosine kinases and their ephrin ligands play important roles in wiring of the developing nervous system. We have investigated here the function of Src family kinases (SFKs) in the retinotectal projection to dissect the signaling pathways by which EphA receptors control actin/microtubule rearrangements that underlie growth cone guidance and collapse. Both EphAs and SFKs are expressed broadly in retinal growth cones, and SFKs are recruited to EphA receptors after ephrinA stimulation. In the stripe and growth cone collapse assays we observe an abolition of EphA-mediated repulsion after inhibiting SFKs, either pharmacologically or enzymatically via electroporation-mediated overexpression of the SFK inhibitor Csk. In addition, we identify cortactin and the RhoGEF ephexin, which interact with EphA receptors in retinal axons, as targets of SFK-dependent tyrosine phosphorylation. In sum, our data suggest an important role of SFKs as downstream signaling molecules in EphA receptor-mediated repulsive axon guidance.
Direct Action of Estradiol on Gonadotropin-Releasing Hormone-1 Neuronal Activity via a Transcription-Dependent Mechanism
Authors: Temple Jennifer L. , Laing Eric , Sunder Anushka , Wray Susan
Published: July 2004

Pulsatile secretion of gonadotropin-releasing hormone-1 (GnRH-1) is essential for reproduction. GnRH-1 induces gonadotropin release and is regulated by 17β-estradiol (E2). Although a subpopulation of GnRH-1 neurons expresses estrogen receptor (ER) β, it is unclear whether E2 acts directly on GnRH-1 neurons or indirectly through interneuronal connections. To test the hypothesis that E2 acts directly on GnRH-1 neurons to regulate neuronal activity, we used calcium imaging to monitor intracellular calcium oscillations in GnRH-1 neurons maintained in nasal explants. TTX was used to minimize synaptic input from other cells. Consistent with previous studies, TTX reduced the activity of individual GnRH-1 neurons to a basal level, while the population of cells maintained synchronized calcium oscillations. Exposure of GnRH-1 cells to TTX plus E2 increased the number of calcium peaks/cell, percentage of cells with ≥10 peaks, mean peak amplitude, and percentage of cells that contributed to each calcium pulse in explants maintainedin vitrofor 7 d (7 div) compared with TTX alone. These effects were induced within 30 min and were not mimicked by 17α-estradiol, E2 conjugated to BSA (which does not cross the plasma membrane), or seen at 21 div, when the percentage of GnRH-1 cells expressing ERβ transcripts declines. In addition, these effects were inhibited by the ER antagonist ICI 182,780 and prevented by inhibition of gene transcription. These data suggest that, via ERβ, E2 can rapidly act as a hormone-activated transcription complex and are the first to show that E2 directly increases GnRH-1 neuronal activity and synchronization.
The Amygdala Is Enlarged in Children But Not Adolescents with Autism; the Hippocampus Is Enlarged at All Ages
Authors: Schumann Cynthia Mills , Hamstra Julia , Goodlin-Jones Beth L. , Lotspeich Linda J. , Kwon Hower , Buonocore Michael H. , Lammers Cathy R. , Reiss Allan L. , Amaral David G.
Published: July 2004

Autism is a neurodevelopmental disorder characterized by impairments in reciprocal social interaction, deficits in verbal and nonverbal communication, and a restricted repertoire of activities or interests. We performed a magnetic resonance imaging study to better define the neuropathology of autistic spectrum disorders. Here we report findings on the amygdala and the hippocampal formation. Borders of the amygdala, hippocampus, and cerebrum were defined, and their volumes were measured in male children (7.5-18.5 years of age) in four diagnostic groups: autism with mental retardation, autism without mental retardation, Asperger syndrome, and age-matched typically developing controls. Although there were no differences between groups in terms of total cerebral volume, children with autism (7.5-12.5 years of age) had larger right and left amygdala volumes than control children. There were no differences in amygdala volume between the adolescent groups (12.75-18.5 years of age). Interestingly, the amygdala in typically developing children increases substantially in volume from 7.5 to 18.5 years of age. Thus, the amygdala in children with autism is initially larger, but does not undergo the age-related increase observed in typically developing children. Children with autism, with and without mental retardation, also had a larger right hippocampal volume than typically developing controls, even after controlling for total cerebral volume. Children with autism but without mental retardation also had a larger left hippocampal volume relative to controls. These cross-sectional findings indicate an abnormal program of early amygdala development in autism and an abnormal pattern of hippocampal development that persists through adolescence. The cause of amygdala and hippocampal abnormalities in autism is currently unknown.
Reanalysis of P2X7Receptor Expression in Rodent Brain
Authors: Sim Joan A. , Young Mark T. , Sung Hye-Youn , North R. Alan , Surprenant Annmarie
Published: July 2004

P2X receptors are cationic-selective ion channels gated by extracellular ATP. There are seven subunits (P2X1-7), the first six of which are expressed throughout the peripheral and central nervous systems. P2X7receptors are rapidly upregulated and activated as a result of inflammatory stimuli in immune cells, where they act not only as cationic channels but uniquely couple with rapid release of proinflammatory cytokines, cytoskeletal rearrangements, and apoptosis or necrotic cell death. The P2X7receptor has been termed the cytolytic non-neuronal P2X receptor because it had not been detected in neurons until recently when it has been immunolocalized to several brain regions, particularly the hippocampus, and has been suggested to be involved in presynaptic modulation of transmitter release. Because its expression in brain neurons may have substantial functional implications, we have performed detailed immunocytochemical, immunoblot, and immunoprecipitation studies on brain and non-neuronal tissue using all currently available antibodies. We first examined rats, but staining patterns were inconsistent among antibodies; we therefore studied mice for which there are two P2X7knock-out mice constructs available, one expressing the LacZ transgene. We found that P2X7receptor protein is strongly and reliably detected in the submandibular gland and lung of wild-type mice but not in either of the P2X7-/-mice. However, we failed to find evidence for P2X7receptor protein in hippocampal neurons or their input-output projections. Either the P2X7protein in the hippocampus is below the limits of detection by the currently available methods or it is not present.
Combinatorial Therapy with Neurotrophins and cAMP Promotes Axonal Regeneration beyond Sites of Spinal Cord Injury
Authors: Lu Paul , Yang Hong , Jones Leonard L. , Filbin Marie T. , Tuszynski Mark H.
Published: July 2004

Previous attempts to promote regeneration after spinal cord injury have succeeded in stimulating axonal growth into or around lesion sites but rarely beyond them. We tested whether a combinatorial approach of stimulating the neuronal cell body with cAMP and the injured axon with neurotrophins would propel axonal growth into and beyond sites of spinal cord injury. A preconditioning stimulus to sensory neuronal cell bodies was delivered by injecting cAMP into the L4 dorsal root ganglion, and a postinjury stimulus to the injured axon was administered by injecting neurotrophin-3 (NT-3) within and beyond a cervical spinal cord lesion site grafted with autologous bone marrow stromal cells. One to 3 months later, long-projecting dorsal-column sensory axons regenerated into and beyond the lesion. Regeneration beyond the lesion did not occur after treatment with cAMP or NT-3 alone. Thus, clear axonal regeneration beyond spinal cord injury sites can be achieved by combinatorial approaches that stimulate both the neuronal soma and the axon, representing a major advance in strategies to enhance spinal cord repair.
Subunit-Specific Regulation of NMDA Receptor Endocytosis
Authors: Lavezzari Gabriela , McCallum Jennifer , Dewey Colleen M. , Roche Katherine W.
Published: July 2004

At excitatory synapses, both NMDA and AMPA receptors are localized to the postsynaptic density (PSD). However, unlike AMPA receptors, synaptic NMDA receptors are stable components of the PSD. Even so, surface-expressed NMDA receptors undergo endocytosis, which is more robust early in development and declines during synaptic development. We investigated the subunit-specific contributions to NMDA receptor endocytosis, specifically defining the endocytic motifs and endocytic pathways preferred by the NR2A and NR2B subunits. We find that NR2A and NR2B have distinct endocytic motifs encoded in their distal C termini and that these interact with clathrin adaptor complexes with differing affinities. We also find that NR2A and NR2B sort into different intracellular pathways after endocytosis, with NR2B preferentially trafficking through recycling endosomes. In mature cultures, we find that NR2B undergoes more robust endocytosis than NR2A, consistent with previous studies showing that NR2A is more highly expressed at stable synaptic sites. Our findings demonstrate fundamental differences between NR2A and NR2B that help clarify developmental changes in NMDA receptor trafficking and surface expression.
Independent Coding of Reward Magnitude and Valence in the Human Brain
Authors: Yeung Nick , Sanfey Alan G.
Published: July 2004

Previous research has shown that two components of the event-related brain potential, the P300 and feedback negativity, are sensitive to information about rewards and penalties. The present study investigated the properties of these components in a simple gambling game that required participants to choose between cards that were unpredictably associated with monetary gains and losses of variable magnitude. The aim was to determine the sensitivity of each component to two critical features of reward stimuli: magnitude (small or large) and valence (win or loss). A double dissociation was observed, with the P300 sensitive to reward magnitude but insensitive to reward valence and the feedback negativity showing the opposite pattern, suggesting that these two fundamental features of rewarding stimuli are evaluated rapidly and separately in the human brain. Subsequent analyses provided additional evidence of functional dissociations between the feedback negativity and P300. First, the P300 (but not the feedback negativity) showed sensitivity to the reward value of alternative, nonselected stimuli. Second, individual differences in the amplitude of the feedback negativity correlated with individual differences in risk-taking behavior observed after monetary losses, whereas individual differences in P300 amplitude were related to behavioral adjustments observed in response to alternative, unchosen outcomes.
Modelling of Selective NO
x
Reduction on Ce/In-Promoted Sulfated Zirconia Catalysts
Authors: Schädlich E. Karoline , Suprun Wladimir , Schädlich H. Kuno , Papp Helmut
Published: July 2004

Various pseudohomogeneous models for the selective catalytic reduction of NO
x
by methane were developed by considering reaction schemes and kinetic mechanism. The models were applied to predict the performance of Ce/In-promoted sulfated zirconia catalysts in a wide temperature range from 300 to 700 °C in a fixed bed reactor assuming plug-flow. A nonlinear kinetic model fits the experimental data better than a simple linear model. The mass balance differential equations were solved numerically. The model parameters were estimated by the Simplex-method of Nelder–Mead with a fourth order Runge–Kutta–Merson-method. The finally chosen model is better suited for the prediction of the In-free catalysts than for the mixed oxide catalysts or the Ce-free catalysts. The model suggests that CO formed in the process plays no role in the reduction of NO by CH4. This was confirmed by experimental evidence. The investigated Ce/In zirconia system was better suited for NO reduction by CH4 than those published previously.
CO Oxidation on a Pd/Fe3O4(111) Model Catalyst
Authors: Meyer R. , Shaikhutdinov Sh. K. , Freund H.-J.
Published: July 2004

Adsorption of CO and O2 on Pd particles deposited on a well-ordered Fe3O4(111) film was studied by temperature programmed desorption. Scanning tunneling microscopy was used to provide structural information. The results show that CO adsorbed on Pd particles reacts with oxygen of the oxide support and forms CO2. The reaction occurs at the particle/oxide interface and exhibits a particle size effect such that the smaller particles produce more CO2. Oxidation of Pd/Fe3O4 alters the oxide structure due to Pd catalyzed oxygen migration into the film and results in formation of an oxygen reservoir, which favors CO oxidation reaction.
The Surface Geometry of Carbon Monoxide and Oxygen Co-adsorbed on Ni{111}
Authors: Braun Wolfgang , Steinrück Hans-Peter , Held Georg
Published: July 2004

Low energy electron diffraction (LEED) structure determinations have been performed for the p(2×2) structures of pure oxygen and oxygen co-adsorbed with CO on Ni{111}. Optimisation of the non-geometric parameters led to very good agreement between experimental and theoretical IV-curves and hence to a high accuracy in the structural parameters. In agreement with earlier work atomic oxygen is found to adsorb on fcc sites in both structures. In the co-adsorbed phase CO occupies atop sites. The positions of the substrate atoms are almost identical, within 0.02 Å, in both structures, implying that the interaction with oxygen dominates the arrangement of Ni atoms at the surface.
A Statistical Mechanical Model of Polymer Brushes: Equilibrium and Growth
Authors: Livadaru Lucian , Kreuzer Hans Juergen
Published: July 2004

We construct a statistical mechanical model for a polymer brush in θ-solvent. The model is exactly solvable for realistic polymer models (e.g. the freely rotating chain and the rotational isomeric state models) and it readily accounts for inhomogeneities of the brush with respect to the plane parallel to the grafting surface. The interactions between neighboring chains is mimicked by the presence of a confinement potential centered on the grafting point of each chain. We explore the model to calculate the equilibrium and kinetic properties of the polymer brush. We find that the variations of the brush free energy and height with the coverage depend strongly on the stiffness of the polymer chain (bond angle) and on the severity of the chain confinement. The results for the growth kinetics of the brush are compared with recent measurements on the formation of a PEG2000 brush from solution.
Physisorption of Small Molecules on Single Crystal Alkali Halide Surfaces: CO and N2 Adsorbed on KCl(100)
Authors: Vogt J. , Weiss Helmut
Published: July 2004

The adsorption of CO and N2 on KCl(100) single crystal cleavage planes has been investigated by means of low energy electron diffraction (LEED) at primary currents in the nA range as well as polarization infrared spectroscopy (PIRS) in transmittance geometry. These isoelectronic adsorbates behave very similarly, and three different adsorption phases can be distinguished as a function of surface coverage for both of them. Initially a (1×1) structure is observed and assigned to a commensurate monolayer with one molecule per KCl ion pair. The CO infrared spectrum of this ‘phase I’ is characterized by a doublet absorption of the CO stretching vibration, which is discussed in the context of a correlation field splitting. The lack of superstructure diffraction peaks is attributed to a high degree of orientational disorder in this phase. From LEED adsorption isotherms the isosteric heat of adsorption of N2 has been determined to be 11±3 kJ mol−1. Upon increase in coverage by 50% ‘phase II’ is formed which exhibits a large number of additional diffraction spots. It is assigned to a bilayer in which the second layer is only half filled. Based on the LEED experiments a structure model is proposed in which the second layer is characterized by growth in rows along the [210] direction and a high degree of roughness in the perpendicular direction. This model can explain all experimentally observed main features. Finally upon further exposure formation of three-dimensional solid is observed, which proceeds via Stransky–Krastanov growth of crystalline 3D clusters with the structure of the low-temperature cubic α-phase. A simulation of the CO cluster infrared spectra within the dipole–dipole coupling approach can reproduce all major observed vibrational features.
Early responses to Avery et al.'s paper on DNA as hereditary material
Authors: DEICHMANN UTE
Published: July 2004

Avery's et al.'s 1944 paper provides the first direct evidence of DNA having gene-like properties and marks the beginning of a new phase in early molecular genetics (with a strong focus on chemistry and DNA). The study of its reception shows that on the whole, Avery's results were immediately appreciated and motivated new research on transformation, the chemical nature of DNA's biological specificity and bacteria genetics. It shows, too, that initial problems of transferring transformation to other systems and prominent criticism of its results nurtured skepticism. Avery's experiment was downplayed and neglected particularly by many of those scientists who worked in the new fields of biochemical and biophysical genetics, genetic phage, and TMV research. This was not due to the fact that the implications of the paper could not be connected to generally accepted knowledge. Contrary to a widespread belief, the assumed uniformity of DNA as opposed to proteins was not used as an argument against the validity of Avery's et al.'s finding. The indifference rather reflected, among other things, the disciplinary gap between the chemically oriented microbiologists and the old and new geneticists who remained committed to genetic and physical methods (in particular x-ray studies) and clung to the assumption that proteins were the sole carriers of biological specificity. The responses to Avery's et al.'s paper show how different research interests in the areas between microbiology, genetics, and biochemistry interacted with the prejudices, dogmas, individual farsightedness or short-sightedness, and scientific authority during a pivotal period of early molecular biology.
Scientific discovery in statu nascendi: The case of Dmitrii Mendeleev's Periodic Law
Authors: DMITRIEV IGOR S.
Published: July 2004

The history of Mendeleev's famous discovery has long been a matter of lively debate among experts. This essay proposes a new reading of this story, which differs from the well-known reconstructions made by Kedrov, Bensaude-Vincent, Graham and others. Particular attention is paid to the context of a Mendelevian thought and the analysis of the surviving outlines of his first variants of the Periodic Table. By considering Mendeleev's discovery of the Periodic Law one can identify the three principal stages in his work: 1) the composition of the “first attempt”(pervaia proba) of the system of chemical elements and the discovery of the periodic character in dependence of the elements, properties on their atomic weights (late 1868-early 1869); 2) the composition of Attempt at a system of elements based on their atomic weights and chemical similarity as a temporary version of the Periodic Table (February 1869); 3) the composition of the Natural system of elements (November 1870).

Mendeleevian work on Attempt revealed a lack of clear chemical criteria for unifying elements of different classes—the “natural families” and “transitional metals”—into a general taxomonical scheme that forced him to reject the ideal structure of the system of elements that he had formed earlier (1868). It was only by November of 1870 that Mendeleev finally solved the “unification problem,” formulating the basic principles of his system. This article also discusses how Mendeleev's views on the structure of the Periodic System were mediated by his convictions regarding the constitution of organic compounds.
Project Vista, Caltech, and the dilemmas of Lee DuBridge
Authors: McCRAY W. PATRICK
Published: July 2004

In the summer of 1951, more than one hundred scientists and other academics participated in Project Vista, a secret study hosted by the California Institute of Technology. Its purpose was to determine how existing technologies as well as ones soon to be available—tactical nuclear weapons, in particular—could offset NATO's weaker conventional forces and repel a massive Soviet invasion of Europe many perceived as likely if not imminent. Despite the best efforts of scientists like William Fowler, Lee DuBridge, and J. Robert Oppenheimer, Vista's recommendations were eventually suppressed by the Air Force. This article examines the history of Project Vista as a circumstance of the early Cold War period. By focusing primarily on the local level, the article presents a detailed examination of how people were recruited to Project Vista, how their work was organized and managed, and the relations between Caltech's administration and trustees. Finally, this article considers the history of postwar universities as they struggled to adapt to the Cold War environment and scientists' efforts to provide counsel to the U.S. government and military.
The SIRIO satellite, 1968–1977: Between scientific engagement and managerial inexperience
Authors: ORLANDO LUCIA
Published: July 2004

The story of the first Italian communications satellite, SIRIO, started in 1968, after the failure of the European project for the vector ELDO-PAS. The story up to the launch in 1977 involved the encumbering legacy of the San Marco satellite's success in the 1960s, political uncertainty in Italy, international economic crises of the 1970s, an overtly complex management system, and an inexperienced aerospace industry. Despite these handicaps, SIRIO won the race with its nearest competitor, the European satellite OTS, which had a similar research aim in the super high frequency band. In addition to collecting a large amount of useful data, SIRIO catalyzed the process for developing an improved organizational structure for Italian space research.
Passing as a Pastor: Clerical Imposture in the Colonial Atlantic World
Authors: Kidd Thomas
Published: July 2004

Many impostors in the eighteenth century tried to pass as pastors in North America's churches. This phenomenon showed how increasing engagement with the broader Atlantic world could carry ominous implications for colonial religious leaders, implications that would become manifest in the itinerancy of the evangelical revivals and, in the early republic, finally crush any hopes of centered American religious authority. Eighteenth-century episodes of clerical imposture help illuminate the increasing loss of cultural mastery faced by religious elites as a result of Atlantic anonymities, itinerant ministries, and democratic sensibilities. This article considers why so many in the eighteenth century attempted to pass as pastors, from British wanderers like the supposed brick-maker Samuel May to notorious criminals like Tom Bell or Stephen Burroughs. Understanding the conditions that led to these cases of clerical imposture leads to greater understanding of the nature of religious and cultural power in colonial North America and in the early American republic. The eighteenth century brought a crisis to America concerning the implications of cultural and demographic fluidity as elites worried more and more about assigning true value and uncovering conspiracy in a world newly dependent on appearances to establish authority. The increasing cosmopolitanism, immigration, and commerce helped make the colonial elites more wealthy and powerful, but they also now had to scramble to resist the potential for deception and imposture that the new engagements created. Such conditions made new room for con men, many of whom posed as pastors to access the power of religious authorities.
Why Women Loved Billy Sunday: Urban Revivalism and Popular Entertainment in Early Twentieth-Century American Culture
Authors: Bendroth Margaret
Published: July 2004

Evangelist Billy Sunday (1862–1935) is well-known for an aggressively masculine platform style that was clearly aimed at attracting a male audience to his urban revival campaigns. Less recognized but equally important are Sunday's meetings for “women only,” in which the handsome, athletic evangelist preached passionate, explicit sermons on sexual vice to an audience that had been purged of all male interlopers. Though Sunday's ostensible purpose was to reinforce traditional Victorian morality—the sermons were originally meant to rail against birth control—the social context for his message subtly undermined its conservative aim. As is illustrated by his campaign in Boston during the winter of 1916–1917, Sunday was perceived by many of his contemporaries, both men and women, as scandalously frank to the point of sexual crudeness. Critics and supporters alike described him in the same terms they used for vaudeville and theater idols, a notion that ex-baseball player Sunday did little to dispel. Yet, evangelical Protestant women came to hear his muscular Christian message anyway. The ability of his female audiences to adapt to—and obviously enjoy— Sunday's physical stage presence suggests that often-used terms like “feminization” and “masculinization” are too stark to describe the transition from Victorian to modern forms of religious behavior. Women's response to Sunday, situated at the intersection of evangelical religion and popular entertainment culture, demonstrates the durability of feminine religious tastes and suggests ways in which the blurring and confusion of formal gender categories factored into the transition from Victorian piety into the more individualized, popularized forms of religious faith in the twentieth century. Women were not passive observers in the transformation of American religion but central to the nature and direction of its survival.
Intellectual Property and the Historian in the New Millennium
Authors: Herman Gerald
Published: July 2004

On April 12, 2002, a roundtable discussion was held during the joint National Council on Public History/Organization of American Historians annual meetings in Washington D.C. This roundtable, “Intellectual Property and the Historian in the New Millennium,” addressed issues of copyright for public historians as authors and users in the digital age, when the technologies of reproduction and dissemination have exploded and Congress has struggled to keep up. Roundtable chair Gerald Herman summarizes the challenges faced by public historians in the new millennium and introduces a transcript of the roundtable discussion.
Egy gyökérzónás-nádastavas szennyvíztisztító rendszer talajának és szennyvizének elemtartalma
Authors: Németh Nóra , Baczó Gáborné , Radimszky László
Published: July 2004

A gyökérzónás-nádastavas szennyvíztisztító rendszer muködését a Nógrád megyei Szügy község térségében tanulmányoztuk, ahol 1994 óta muködik egy ilyen típusú rendszer. A vízzáró fóliával burkolt, ülepített szennyvizet fogadó nádas szuroágyak humuszos feltalaj-, homokos kavics-, homok- és kavicsrétegekbol állnak. Nyomon követtük a talaj elemtartalmának alakulását a kétéves vizsgálati periódus során és feltártuk az esetleges akkumulációkat. A mintaterületekrol havonkénti gyakorisággal vett talaj- és szennyvízmintákban a következo paramétereket vizsgáltuk: Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Sr, Ti, V, Zn, NH4-N, NO3-N és összes-N. Mind a talajban, mind a vízben mért átlagos koncentrációadatokat összehasonlítottuk a szakirodalomból vett természetes nádas élohelyek vizsgálati adataival. Megállapítható, hogy a szennyvízben mért koncentrációértékek a Ca, K, Na, P, NH4-N és a Zn elemeknél többszörösek voltak összevetve a balatoni élovíz adataival. A Mg, Fe, Sr, NO3-N és Mn elemek koncentrációi lényegesen nem különböztek a természetes és mesterséges élohelyen. A talaj, illetve az üledék koncentrációértékeit elemezve megállapítható, hogy a Ca, Mg, Na, P, Mn és a Cu esetében egy nagyságrenddel nagyobbak voltak a szügyi telepen mért értékek, míg a K és a Fe esetében ketto, az összes-N esetében három nagyságrendi különbség volt megfigyelheto. A Sr és a Zn esetében nem volt tapasztalható nagyságrendbeli különbség a balatoni üledék és a nádas szuromezo talaja között.
Foszfor-cink kölcsönhatás-vizsgálatok a trágyázási kutatásokban
Authors: Turán Tamás Levente
Published: July 2004

A P-Zn kölcsönhatások vizsgálata az 1930-as évektol indult, amikor növény- és talajvizsgálatok alapján arra következtettek, hogy e két elem egymás növényi felvételét befolyásolja. A P-trágyák egyre elterjedtebb alkalmazásával megjeleno P-indukálta Zn-hiány gyakori jelenséggé vált a XX. század második felében. A Zn-hiány, és az emiatt fellépo élettani zavarok okaiként több lehetséges változatot is megemlítenek a kutatók. Általános az a vélemény, hogy a P-trágyázással kiváltott Zn-hiány nem a foszfátok általi közvetlen Zn-kicsapódás következménye, hanem növényfiziológiai alapú.  A növényben végbemeno folyamatok megítélése azonban eltéro. Egyesek a talaj nagy CaCO3-tartalmát teszik felelossé a mérsékelt Zn-felvételért és növénybeni szállítódásért, mások a Zn-hiányos szövetekben kialakult nagy Fe-tartalomban látják az élettani zavarok okát. A harmadik vélemény szerint a Zn-hiány következtében egy, a hajtásban jelenlévo, a gyökerek P-felvételét és a P-transzportot szabályozó visszacsatolási mechanizmus károsodik, melynek eredményeképpen toxikus mértékben halmozódik fel a foszfor a levelekben a gyökér felé irányuló visszaszállítódás lecsökkenése, esetleg elmaradása miatt. A vizsgálatok egységesen következtettek azonban arra, hogy a P/Zn arány eltolódásának és a gyökér, valamint a levelek erosen eltéro P- és Zn-tartalmának az oka, hogy a Zn-hiány által kiváltott rendellenesség következtében a gyökérbol a levelek irányába zajló Zn-szállítódás lecsökken, a P-szállítódás pedig megno.  Magyarországon elsoként a gyümölcstermesztok körében vált ismertté a Zn-hiány fogalma. A P-trágyázás és meszezés Zn-felvételre gyakorolt hatásairól azonban a kertészek is csak a 1970-es évek elején tesznek említést, csakúgy, mint a szántóföldi kultúrákkal foglalkozó kutatók. A vizsgálatok sok tekintetben hasonló eredményre vezettek mint külföldi kollegáiké, de pl. a P-mutrágyázásra bekövetkezett Fe-tartalom változásában a megállapítások eltéroek.  Látható tehát, hogy a P-Zn kölcsönhatás kérdése nem tisztázott, számos egymásnak ellentmondó közlés található a nemzetközi irodalomban. Míg az 50-60-as években rendszeresen jelentek meg cikkek a témából, az utóbbi 10-15 évben már csak néhány szerzo foglalkozott vele keveset publikálva. További elemzésre szorul, hogy az említett hazai kísérletekben milyen gyakorisággal erosödhet a PxZn kölcsönhatás, milyen az idojárási tényezok befolyásoló szerepe és hogyan hatnak mindezek a hozamokra.
Könyvismertető
Authors: Tamás János , Simon László
Published: July 2004

Simon László (szerk.): Talajszennyezodés, talajtisztítás (Környezetügyi Muszaki Gazdasági Tájékoztató 5. kötet) (Környezetgazdálkodási Intézet, Budapest, 1999) Tamás János: Precíziós mezőgazdaság elmélete és gyakorlata (Mezőgazdasági Szaktudás Kiadó, Budapest, 2001)
Nitrátlemosódás vizsgálata liziméteres és szabadföldi tartamkísérletben
Authors: Szalókiné Zima Ildikó , Szalóki Sándor
Published: July 2004

Liziméteres és szabadföldi kísérletekben vizsgáltuk a víz- és a tápanyagforgalmat különbözo szintu víz- és tápanyagellátás mellett. Megállapítottuk, hogy a szivárgó víz mennyiségét az öntözés éves átlagban 10-40 mm-rel növelte, amíg a tápanyagpótlás 5-20 mm-rel mérsékelte. A szivárgó víz koncentrációját a mutrágya jelentosen fokozta, az öntözés pedig csökkentette. A legtöbb NO3-N-kimosódást, és a talajban is a legtöbb nitrogént a nagy adaggal (200 kg/ha) mutrágyázott öntözetlen lizimétereknél (14) mértük, ahol a tápanyagmérleg je-lentosen pozitív volt; a legkevesebbet pedig a legkisebb N-pótlásnál (50 kg/ha) az öntözött kezelésben. A parcellák 210 cm-es talajrétegében jelentos nitrát-felhalmozódást sehol sem tapasztaltunk, bár a kezelések között nagyarányú különbségek alakultak ki. A N-mérleg egyensúlya kukoricánál 150-200 kg/ha N-pótlásnál van, viszont a legkisebb mutrágyaadag esetében a mérleghiány eléri a 60-80 kg/ha/év közötti értéket a vízellátástól függoen. A kedvezo vízellátású kezelésekben a 210 cm rétegben csupán 130-140 kg/ha között van a felveheto N-mennyiség, sot még a legnagyobb (200 kg-os) adagnál sem magas, 260-270 kg/ha körüli NO3-N- t találtunk. Az a tény, hogy a nem öntözött liziméterekben jóval alacsonyabbak a termésátlagok, mint az ugyanolyan kezelésu parcellákon, arra utal, hogy a 90 cm alatti talajnak, az oda leszivárgó víznek, valamint tápanyagoknak jelentos szerepe van a növények víz- és tápanyagellátásában.
Észak-amerikai és magyarországi talajok víztartó képességének összehasonlító vizsgálata
Authors: Ács Ferenc , Drucza Miklós
Published: July 2004

Észak-amerikai és magyarországi talajok víztartó képességét hasonlítottuk össze. Az észak-amerikai és magyarországi talajok víztartó képességét Clapp és Hornberger (1978) (?CH(?)), valamint Rajkai (1988) (?R(?)) parametrizá-ciója alapján elemeztük. Az elemzést homok, vályog, agyag fizikai talajféleségre, valamint homogén (?H/YH) és inhomogén (?INH/YINH) területi eloszlású talajnedvességre vonatkozóan végeztük el. Az inhomogén területi eloszlású ?-t normális eloszlással szimuláltuk.  A legfontosabb eredményeket a következokben foglaljuk össze:  1. A ?CHH(?) és a ?RH(?) közötti eltérések a legnagyobbak az agyag fizikai féleség esetén, száraz viszonyokban (pl. log½?CH(0,15 m3m-3)½-log½?R(0,15 m3m-3)½= 2 pF érték).  2. A ?RH(?)- és a ?RINH(?)-függvények közötti eltérések minden fizikai féleségre és ?-értékre vonatkozóan kicsik. 3. Számszerusítettük a ?INH(?)- és a ?H(?)-függvények közötti kapcsolatokat. Az eredmények a talaj vízháztartásának becslése során hasznosíthatók.
Módszer a talaj szerves-C-tartalmának gyors helyszíni meghatározására
Authors: Tóth Tibor , Szabó Brigitta
Published: July 2004

60 reprezentatív minta használatával olyan terepi módszereket hasonlítottunk össze laboratóriumban, amelyek alkalmasak a talaj szerves-C-tartalmának meghatározására. A módszereket a szabvány szerinti Tyurin-módszerrel összevetve értékeltük. A talajminták színe, elsosorban a Munsell-féle színmélység (Value) szoros korrelációt (R = 0,73**) mutatott a talajok humusztartalmának logaritmusával. Ez az összefüggés rámutat, hogy további vizsgálatokat érdemes folytatni a talajok szerves-C-tartalma és színe közötti részletes összefüggések feltárására. A terepi Walkley-Black módszer a laboratóriumi meghatározástól csak a szükséges reagensek mennyiségében tér el, így a vizsgálat során tömény kénsavas kálium-bikromáttal oxidáljuk el a szerves anyagot. A kénsav hozzáadásakor az oldat nagyon felmelegszik, ezért csak hulés után öntheto át kémcsobe, ami az oldatok színének összehasonlítása miatt szükséges. A vizsgálat veszélyessége miatt a módszer nem alkalmas terepi alkalmazásra. Mind a terepi módszerrel meghatározott abszorbancia (R = 0,73**), mind a minták abszorbancia szerinti sorrendje (R = 0,87**) szoros korrelációt mutatott a Tyurin-módszerrel kapott humusztartalommal. A humusztartalom logaritmusa és a lúgos EDTA transzmittancia között 0,78** volt a korrelációs koefficiens értéke. A vizsgálatok során kitunt, hogy egyes talajalkotók (CaCO3, vas- és alumínium-oxidok) megváltoztatják az oldat színét és így zavarják a szervesanyag-becslést. Az újonnan kidolgozott kálium-permanganátos szén-dioxid-fejlesztéses módszer lényege a talaj savas kálium-permanganát oldattal történo kezelése, majd a lefedett edényben három perc elteltével a képzodött szén-dioxid-koncentráció muszeres mérése. A helyszíni szén-dioxid-mérést infravörös érzékelovel muködo hordozható berendezéssel végezzük. A talaj szervetlen karbonáttartalmának hatását párhuzamos, kálium-permanganát hozzáadása nélkül végzett reakcióval vesszük figyelembe. A Tyurin-módszerrel kapott humusztartalom és a módszer alkalmazása során képzodött CO2-tartalom közötti korrelációs koefficiens 0,76** volt, a 20 %-nál kisebb karbonáttartalmú minták esetén pedig 0,81**. Az új módszer továbbfejlesztéséhez tervezzük a talajhoz adott kénsav és víz mennyiségének olyan megválasztását, hogy a karbonát- és szervesanyag-meghatározás esetén a végeredmény ugyanolyan kénsavkon-centráció legyen. A 12,5 %-os karbonát- és 0,7 %-os szerves-C-visszanyerést szintén javítani kell, hogy a minták heterogenitása esetén a két szénforrás nagyon különbözo hatása kevésbé érvényesüljön a meghatározás folyamán. A módszerek megbízhatóságát 12 kiválasztott minta négy ismétlésben történt vizsgálata alapján, a variációs koefficiens alkalmazásával értékeltük. A sorrenden alapuló módszerek mutatták a legkisebb variációs koefficienst, majd a terepi Walkley-Black, Tyurin szerinti humusz, lúgos EDTA transzmittancia és a kálium-permanganátos CO2-fejlesztéses módszer egyre nagyobbat. A laboratóriumban összehasonlított módszerek alkalmazhatóságát a terepen fogjuk véglegesen tesztelni.
A mezőgazdasági területekről a felszíni vizekbe kerülő foszforterhelések
Authors: Osztoics Erzsébet , Sárdi Katalin , Sisák István , Osztoics András , Magyar Marianna , Szűcs Péter
Published: July 2004

Amennyiben a talajok P-tartalma az agronómiailag indokolt szint fölé emelkedik, ugrásszeruen megnohet a talajból a felszíni vizekbe, ill. bizonyos körülmények között a felszín alatti vizekbe jutó foszfor mennyisége. A csatornák, patakok, folyók és tavak stb. vizének kritikus szint feletti P-koncentrációja az eutrofizáció felgyorsulásához vezethet.  Az 1960-as évek közepétol a több mint két évtizedes talajgazdagító P-trágyázás (+20 és +40 kg/ha P2O5 többletek) következtében rohamosan javulni kezdett talajaink P-ellátottsága és az 1990-es évek elejére a szántóterület mintegy 2/3-a foszforral jól, vagy igen jól (túlzottan) ellátottá vált. 1990-tol kezdodoen a hazai P-mérlegek erosen negatívak, évi -10 és -20 kg/ha P2O5-hiányt mutatnak. A fejlett nyugat-európai országokban ma is erosen pozitívak a P-mérlegek. Annak ellenére, hogy a megnövekedett P-tartalmú talajok fokozott környezeti kockázatot jelentenek, hazánkban mind a mai napig az indokoltnál jóval kevesebb kutatás irányult a környezetvédelmi célú P-talajvizsgálatok hazai adaptációjára.  A kérdéskör vizsgálata azért is kiemelten fontos, mivel Magyarország EU-csatlakozásának elofeltételeként, a városok szennyvíztisztítása megvalósul, felszíni vizeink pontszeru P-terhelése ily módon jelentosen csökken, másrészt nagyobb hangsúlyt kapnak a legnagyobb diffúz szennyezo forrás, a mezogazdasági eredetu P-terhelés csökkentésének lehetoségei. A P-megkötodés mértéke talajonként különbözo lehet. Mivel a szorpciós folyamat az agyagfrakcióhoz és az oxid-hidroxid frakciókhoz kötheto, a P-fixáció a nagy agyagtartalmú talajokban eroteljesebb. Ennek megfeleloen, a szervetlen kolloidokban szegény talajok P-megkötése gyenge. Általában véve, a 6,0 és 6,5 közötti pH(H2O)-értékek mellett legkisebb a P-megkötodés. Erosen savanyú talajokon alacsony oldékonyságú Fe- és Al-foszfátok (strengit, variscit), erosen meszes talajokon a szintén gyenge oldékonyságú Ca-foszfát vegyületek (oktokalcium-foszfát, hidroxiapatit, fluorapatit) képzodése jelzi az eroteljes P-megkötodést.  Az összes P-terhelésbol a mezogazdasági terhelés részarányát 39 %-ra becsülik Dániában, 54 %-ra Norvégiában, 73 %-ra Svédországban, és 79 %-ra Finnországban. Becslések szerint Magyarországon 10 % az agrár P-terhelés aránya. Ez utóbbinak oka a lakossági terhelés rendkívül magas részaránya, a szennyvizeknek kezelés nélküli, közvetlen felszíni vizekbe való vezetése.  A kutatóknak, talajvizsgáló laboratóriumoknak erofeszítéseket kell tenniük a könnyen oldható P-tartalmak, az értéküket befolyásoló talajtulajdonságok (pH, mészállapot, talaj fizikai félesége, szervesanyag-tartalom stb.) minél pontosabb meghatározására, a kalibráció minél pontosabb elvégzésére.  A talaj könnyen oldható P-tartalmát az egyéb információkkal együtt (talajerózió, felszíni elfolyás, P-adag, és P-kijuttatás módja stb.) figyelembe kell venni a potenciális P-terhelés becslésekor.
Mezőföldi talajok KCl-EDTA kivonószerrel oldható mikroelem-tartalmának hosszú idő alatt bekövetkezett változása
Authors: Szűcs Mihály , Szűcs Mihályné
Published: July 2004

Légszáraz állapotban tárolt talajminták és mintavételi helyeiknek 27-31 év elteltével végzett ismételt mintavételezése után vizsgáltuk a Mezőföld 4 településének határában a KCl-EDTA-oldható mikroelem-tartalom változását üzemi viszonyok között. A vizsgálat a természetes és humán eredetű környezeti tényezők együttes, hosszú távú hatása törvényszerűségeinek tanulmányozására irányult.  A vizsgált, döntően mészlepedékes csernozjomok által borított régióban a talajok kémhatása az expozíciós idő alatt nagyon kis mértékben csökkent, a szervesanyag-tartalom viszont nem változott. A talajokban jelentősen nőtt a mért oldható Pb-tartalom, amelynek mennyisége az M7-es autópályától való távolságtól függően változott.  A savanyú talajokhoz hasonlóan nőtt az oldható Fe- és Al-mennyiség. A többszörös determinációs együttható felbontása azt mutatta, hogy az oldható Fe-tartalom pozitív, az oldható Al-tartalom pedig negatív irányban befolyásolja az oldható Pb-mennyiséget. A kapcsolatrendszerben az oldható mangán szerepe kisebb volt, mint azt a savanyú talajok esetében tapasztaltuk.  A vizsgált meszes talajokon nem tapasztaltuk a savanyú talajoknál elsősorban kilúgozódásra visszavezethető mikroelemtartalom-csökkenés jelenségeket.
Histological studies on embryonic development of the rabbit heart
Authors: Balogh Emese , Sótonyi P.
Published: July 2004

Two experiments were performed to evaluate the normal development of the rabbit heart. In the first experiment the most intensive period of heart development was determined in rabbit embryos. The second experiment studied the most intensive period of heart development, determined in the first experiment, by concentrated sampling at 8-hour intervals. After cutting open the uterine wall opposite the discoid placenta, rabbit embryos were removed from the ampullae of the uterus using capillary tubes, under stereomicroscope at fivefold magnification. The embryos were subsequently placed into 4% formalin solution for 24 h. After fixation, slides stained with haematoxylin and eosin were made for histological examination. In the first experiment 51 embryos were examined, while during the second experiment a total of 113 embryos, representing different stages of development, were collected. Finally the data obtained on rabbits were compared with the well-known development of the heart in humans and mice.
Spontaneous antibiotic resistance mutation associated pleiotropic changes in Escherichia coli O157:H7
Authors: Tóth I. , Csík Márta , Emçdy L.
Published: July 2004

Besides the well-known O157:H7 clone causing enterohaemorrhagic colitis and haemolytic uraemic syndrome in Europe, Japan and North America, the number of Escherichia coli isolates with non-motile (NM) phenotype has considerably increased. We supposed that spontaneous antibiotic resistance mutation could cause this phenotypic change. To model our hypothesis we isolated rifampicin- (Rif) and ampicillin- (Amp) resistant mutants from E. coli O157:H7 prototype strains 7785 and EDL933. Among Rif r mutants we could isolate strains with no or reduced motility, while the Ampr mutants became hypermotile. The biochemical profile of the mutants had not changed but phage sensitivity and generation time of the mutants were altered. Among the representative strains we did not find polymorphism with Southern blot analysis and no polymorphism was found in the fliC gene of the mutants. The described characteristics have proven to be stable. In a mice virulence assay by intravenous infections the virulence of the derivatives was also found to be changed. In summary, we found that the antibiotic-resistant phenotype in E. coli O157:H7 was coexpressed with several other phenotypic changes including motility and virulence. It can be assumed that expression of the involved phenotypes may be under the influence of a common regulatory cascade. Further work is needed to identify the components and mechanism of this regulatory system.
Immunological anomalies and thrombocytopenia in 117 dogs and cats diagnosed with Chronic Fatigue Syndrome (cfs)
Authors: Tarello W.
Published: July 2004

Medical records of thirty-five consecutive cases of canine granulocytic ehrlichiosis (CGE) diagnosed cytologically in Central Italy in 1995-2000 were analysed retrospectively. Tick exposure was reported in 16 dogs (45.7%) and concurrent babesiosis in 19 dogs (54.3%). Ehrlichia-like inclusion bodies were found in neutrophils in a percentage varying from 0.5% to 11%. Frequently recorded clinical signs included anorexia (71.4%), lethargy (45.7%), conjunctivitis (31.4%), fever (25.7%), lameness (20%) and ataxia (20%). Among the 16 representative dogs in which protein electrophoresis was performed, 10 (62.5%) showed high globulin levels and 6 (37.5%) had concurrent high total protein levels. During treatment with doxycycline, all associated symptoms, including those unusually described, such as pyoderma intertrigo, erythema, apparent blindness and oral papillomatosis, progressively disappeared in 31 (89%) out of 35 dogs. The efficacy of treatment was marked in dogs simultaneously treated twice with imidocarb dipropionate: among the 14 dogs in which a fast recovery was noted, 11 (80%) were concurrently affected by babesiosis and consequently treated with the specific medicament leading to excellent outcomes. The main conclusion is that CGE is present among dogs from Central Italy and should be included in the differential diagnosis of possible zoonotic agents affecting the canine population.
{\rtf1\ansi\ansicpg1250\deff0\deflang1038\deflangfe1038\deftab708{\fonttbl{\f0\froman\fprq2\fcharset238{\*\fname Times New Roman;}Times New Roman CE;}} \viewkind4\uc1\pard\f0\fs24 N-ras mutation in a canine lymphoma: Short communication \par}
Authors: Mayr B. , Holzheu M. , Schaffner G. ,   et al.
Published: July 2004

Lymphomas of dogs were investigated by molecular genetic methods. Regions of exon 1 and 2 of the N-ras gene, which harbours the mutation hot spots (codons 12, 13 and 61) were screened. A GGT Ţ GAT (glycine Ţ aspartic acid) mutation in codon 13 was present in a multicentric-type lymphoma of a 1-year-old male dog.