bluuebunny/crossref_metadata_2025 huggingface dataset:
Self-Organization of Binocular Disparity Tuning by Reciprocal Corticogeniculate Interactions
Authors: Grunewald Alexander , Grossberg Stephen
Published: July 2002

This article develops a neural model of how sharp disparity tuning can arise through experience-dependent development of cortical complex cells. This learning process clarifies how complex cells can binocularly match left and right eye image features with the same contrast polarity, yet also pool signals with opposite contrast polarities. Antagonistic rebounds between LGN ON and OFF cells and cortical simple cells sensitive to opposite contrast polarities enable anticorrelated simple cells to learn to activate a shared set of complex cells. Feedback from binocularly tuned cortical cells to monocular LGN cells is proposed to carry out a matching process that dynamically stabilizes the learning process. This feedback represents a type of matching process that is elaborated at higher visual processing areas into a volitionally controllable type of attention. We show stable learning when both of these properties hold. Learning adjusts the initially coarsely tuned disparity preference to match the disparities present in the environment, and the tuning width decreases to yield high disparity selectivity, which enables the model to quickly detect image disparities. Learning is impaired in the absence of either antagonistic rebounds or corticogeniculate feedback. The model also helps to explain psychophysical and neurobiological data about adult 3-D vision.
Encapsulation of Implicit and Explicit Memory in Sequence Learning
Authors: Reber Paul J. , Squire Larry R.
Published: July 2002

Contrasts between implicit and explicit knowledge in the serial reaction time (SRT) paradigm have been challenged because they have depended on a single dissociation: intact implicit knowledge in the absence of corresponding explicit knowledge. In the SRT task, subjects respond with a corresponding keypress to a cue that appears in one of four locations. The cue follows a repeating sequence of locations, and subjects can exhibit knowledge of the repeating sequence through increasingly rapid performance (an implicit test) or by being able to recognize the sequence (an explicit test). In our study, amnesic patients were given extensive SRT training. Their implicit and explicit test performance was compared to the performance of control subjects who memorized the training sequence. Compared with control subjects, amnesic patients exhibited superior performance on the implicit task and impaired performance on the explicit task. This crossover interaction suggests that implicit and explicit knowledge of the embedded sequence are separate and encapsulated and that they presumably depend on different brain systems.
Effects of Parietal Lesions in Humans on Color and Location Priming
Authors: Marangolo Paola , Di Pace Enrico , Rafal Robert , Scabini Donatella
Published: July 2002

To determine whether the parietal lobes contribute to the selection of nonspatial features known to be processed in the ventral stream, the current study examined the effect of chronic unilateral parietal lobe lesions in humans on color and location priming. Patients and normal controls performed a go/no-go color discrimination task in which either the same color and different color pairs of stimuli (prime and probe) were projected sequentially either in the same hemifield or in opposite hemifields. Control subjects and patients both showed independent effects of color and location priming. In the patients, primes in either field produced color priming for target probes in the ipsilesional field but not for probes in the contralesional field. This observation implicates the parietal cortex in processing activated codes of stimulus attributes not only for spatial information but also for visual features processed in the ventral visual pathways.
An Analysis of Orientation and Ocular Dominance Patterns in the Visual Cortex of Cats and Ferrets
Authors: Müller T. M , Stetter M. , Hübener M. , Sengpiel F. , Bonhoeffer T. , Gödecke I. , Chapman B. , Löwel S. , Obermayer K.
Published: July 2002

We report an analysis of orientation and ocular dominance maps that were recorded optically from area 17 of cats and ferrets. Similar to a recent study performed in primates (Obermayer & Blasdel, 1997), we find that 80% (for cats and ferrets) of orientation singularities that are nearest neighbors have opposite sign and that the spatial distribution of singularities deviates from a random distribution of points, because the average distances between nearest neighbors are significantly larger than expected for a random distribution. Orientation maps of normally raised cats and ferrets show approximately the same typical wavelength; however, the density of singularities is higher in ferrets than in cats. Also, we find the well-known overrepresentation of cardinal versus oblique orientations in young ferrets (Chapman & Bonhoeffer, 1998; Coppola, White, Fitzpatrick, & Purves, 1998) but only a weak, not quite significant overrepresentation of cardinal orientations in cats, as has been reported previously (Bonhoeffer & Grinvald, 1993). Orientation and ocular dominance slabs in cats exhibit a tendency of being orthogonal to each other (Hüubener, Shoham, Grinvald, & Bonhoeffer, 1997), albeit less pronounced, as has been reported for primates (Obermayer & Blasdel, 1993). In chronic recordings from single animals, a decrease of the singularity density and an increase of the ocular dominance wavelength with age but no change of the orientation wavelengths were found.

Orientation maps are compared with two pattern models for orientation preference maps: bandpass-filtered white noise and the field analogy model. Bandpass-filtered white noise predicts sign correlations between orientation singularities, but the correlations are significantly stronger (87% opposite sign pairs) than what we have found in the data. Also, bandpass-filtered noise predicts a deviation of the spatial distribution of singularities from a random dot pattern. The field analogy model can account for the structure of certain local patches but not for the whole orientation map. Differences between the predictions of the field analogy model and experimental data are smaller than what has been reported for primates (Obermayer & Blasdel, 1997), which can be explained by the smaller size of the imaged areas in cats and ferrets.
Spatiotemporal Connectionist Networks: A Taxonomy and Review
Authors: Kremer Stefan C.
Published: July 2002

This article reviews connectionist network architectures and training algorithms that are capable of dealing with patterns distributed across both space and time—spatiotemporal patterns. It provides common mathematical, algorithmic, and illustrative frameworks for describing spatiotemporal networks, making it easier to compare and contrast their representational and operational characteristics. Computational power, representational issues, and learning are discussed. In additional references to the relevant source publications are provided. This article can serve as a guide to prospective users of spatiotemporal networks by providing an overview of the operational and representational alternatives available.
Synaptic Runaway in Associative Networks and the Pathogenesis of Schizophrenia
Authors: Greenstein-Messica Asnat , Ruppin Eytan
Published: July 2002

Synaptic runaway denotes the formation of erroneous synapses and premature functional decline accompanying activity-dependent learning in neural networks. This work studies synaptic runaway both analytically and numerically in binary-firing associative memory networks. It turns out that synaptic runaway is of fairly moderate magnitude in these networks under normal, baseline conditions. However, it may become extensive if the threshold for Hebbian learning is reduced. These findings are combined with recent evidence for arrested N-methyl-D-aspartate (NMDA) maturation in schizophrenics, to formulate a new hypothesis concerning the pathogenesis of schizophrenic psychotic symptoms in neural terms.
A Computational Model for Visual Selection
Authors: Amit Yali , Geman Donald
Published: July 2002

We propose a computational model for detecting and localizing instances from an object class in static gray-level images. We divide detection into visual selection and final classification, concentrating on the former: drastically reducing the number of candidate regions that require further, usually more intensive, processing, but with a minimum of computation and missed detections. Bottom-up processing is based on local groupings of edge fragments constrained by loose geometrical relationships. They have no a priori semantic or geometric interpretation. The role of training is to select special groupings that are moderately likely at certain places on the object but rare in the background. We show that the statistics in both populations are stable. The candidate regions are those that contain global arrangements of several local groupings. Whereas our model was not conceived to explain brain functions, it does cohere with evidence about the functions of neurons in V1 and V2, such as responses to coarse or incomplete patterns (e.g., illusory contours) and to scale and translation invariance in IT. Finally, the algorithm is applied to face and symbol detection.
Narrow Versus Wide Tuning Curves: What's Best for a Population Code?
Authors: Pouget Alexandre , Deneve Sophie , Ducom Jean-Christophe , Latham Peter E.
Published: July 2002

Neurophysiologists are often faced with the problem of evaluating the quality of a code for a sensory or motor variable, either to relate it to the performance of the animal in a simple discrimination task or to compare the codes at various stages along the neuronal pathway. One common belief that has emerged from such studies is that sharpening of tuning curves improves the quality of the code, although only to a certain point; sharpening beyond that is believed to be harmful. We show that this belief relies on either problematic technical analysis or improper assumptions about the noise. We conclude that one cannot tell, in the general case, whether narrow tuning curves are better than wide ones; the answer depends critically on the covariance of the noise. The same conclusion applies to other manipulations of the tuning curve profiles such as gain increase.
Multioperator Teleoperation of Multirobot Systems with Time Delay: Part II—Testbed Description
Authors: Chong Nak Young , Kotoku Tetsuo , Ohba Kohtaro , Sasaki Hisayuki , Komoriya Kiyoshi , Tanie Kazuo
Published: July 2002

The Mechanical Engineering Laboratory (MEL) 1 has been developing coordinated control technologies for multi-telerobot cooperation in a common environment remotely controlled from multiple operators physically distant from each other. Previously, we learned about how the transmission delay over the network deteriorates the performance of telerobots through simulations. To overcome the operator's delayed visual perception arising from network throughput limitations, we have suggested several coordinated control aids at the local operator site. The testbed facilitates experiments with physical robots for validation beyond simulation. This paper mainly discusses the details of the testbed and investigates the use of an online predictive simulator to assist the operator in coping with time delay over the network. Practically, a common data relay station is suggested to reduce the travel distance of the master data over the network and enable multirobot predictive simulation at one's master station. Operators control their master to get their telerobot to cooperate with the counterpart telerobot using the predictive simulator as well as video image feedback. Specifically, exploiting the audio-visual resources of the simulator, operators can detect a priori the possibility of collision and coordinate conflicting motions between telerobots. We have demonstrated an object rearrangement task by two telerobots and two operators via an ethernet LAN that is subject to simulated delays and evaluated the validity of the online predictive simulator in Multioperator-Multirobot (MOMR) tele-cooperation.

1 On April 1, 2001, MEL merged into the National Institute of Advanced Industrial Science and Technology (AIST).
Efficient and Scalable Pareto Optimization by Evolutionary Local Selection Algorithms
Authors: Menczer Filippo , Degeratu Melania , Street W. Nick
Published: July 2002

Local selection is a simple selection scheme in evolutionary computation. Individual fitnesses are accumulated over time and compared to a fixed threshold, rather than to each other, to decide who gets to reproduce. Local selection, coupled with fitness functions stemming from the consumption of finite shared environmental resources, maintains diversity in a way similar to fitness sharing. However, it is more efficient than fitness sharing and lends itself to parallel implementations for distributed tasks. While local selection is not prone to premature convergence, it applies minimal selection pressure to the population. Local selection is, therefore, particularly suited to Pareto optimization or problem classes where diverse solutions must be covered. This paper introduces ELSA, an evolutionary algorithm employing local selection and outlines three experiments in which ELSA is applied to multiobjective problems: a multimodal graph search problem, and two Pareto optimization problems. In all these experiments, ELSA significantly outperforms other well-known evolutionary algorithms. The paper also discusses scalability, parameter dependence, and the potential distributed applications of the algorithm.
Duplication of Modules Facilitates the Evolution of Functional Specialization
Authors: Calabretta Raffaele , Nolfi Stefano , Parisi Domenico , Wagner Günter P.
Published: July 2002

The evolution of simulated robots with three different architectures is studied in this article. We compare a nonmodular feed-forward network, a hardwired modular, and a duplication-based modular motor control network. We conclude that both modular architectures outperform the non-modular architecture, both in terms of rate of adaptation as well as the level of adaptation achieved. The main difference between the hardwired and duplication-based modular architectures is that in the latter the modules reached a much higher degree of functional specialization of their motor control units with regard to high-level behavioral functions. The hardwired architectures reach the same level of performance, but have a more distributed assignment of functional tasks to the motor control units. We conclude that the mechanism through which functional specialization is achieved is similar to the mechanism proposed for the evolution of duplicated genes. It is found that the duplication of multifunctional modules first leads to a change in the regulation of the module, leading to a differentiation of the functional context in which the module is used. Then the module adapts to the new functional context. After this second step the system is locked into a functionally specialized state. We suggest that functional specialization may be an evolutionary absorption state.
Talking Helps: Evolving Communicating Agents for the Predator-Prey Pursuit Problem
Authors: Jim Kam-Chuen , Giles C. Lee
Published: July 2002

We analyze a general model of multi-agent communication in which all agents communicate simultaneously to a message board. A genetic algorithm is used to evolve multi-agent languages for the predator agents in a version of the predator-prey pursuit problem. We show that the resulting behavior of the communicating multi-agent system is equivalent to that of a Mealy finite state machine whose states are determined by the agents' usage of the evolved language. Simulations show that the evolution of a communication language improves the performance of the predators. Increasing the language size (and thus increasing the number of possible states in the Mealy machine) improves the performance even further. Furthermore, the evolved communicating predators perform significantly better than all previous work on similar prey. We introduce a method for incrementally increasing the language size, which results in an effective coarse-to-fine search that significantly reduces the evolution time required to find a solution. We present some observations on the effects of language size, experimental setup, and prey difficulty on the evolved Mealy machines. In particular, we observe that the start state is often revisited, and incrementally increasing the language size results in smaller Mealy machines. Finally, a simple rule is derived that provides a pessimistic estimate on the minimum language size that should be used for any multi-agent problem.
John von Neumann: The Founding Father of Artificial Life
Authors: Marchal Pierre
Published: July 2002

Aside from being known for his contributions to mathematics and physics, John von Neumann is considered one of the founding fathers of computer science and engineering. Not only did he do pioneering work on sequential computing systems, but he also carried out a major investigation of parallel architectures, leading to his work on cellular automata. His exceptional vision and daring, borrowing from biology the concept of genomic information even before the discovery of DNA's double helix, led him to propose the concept of self-reproducing automata.
A Simulation Tool for Industrial Ecology: Creating a Board Game
Authors: Cushman‐Roisin Benoit , Rice III Norman J. , Moldaver Michael A.
Published: July 2002

This article presents a board game that was developed for use as a simulation tool in teaching the basic concepts of industrial ecology (IE). The game, with the automobile industry as its theme, includes realistic numbers and displays a variety of IE principles. The objectives of the simulation, however, transcend the automobile industry and apply to other manufacturing industries. They include: pollution prevention, design for environment (in several forms, including design for disassembly), environmental management, and life‐cycle assessment. The game has already been played by engineering and business professors, graduate students in environmental engineering, government representatives, and industry executives. A statistical analysis performed on pre‐ and post‐game questionnaires indicates that the game is an effective teaching tool.
BETWEEN HADĪTH AND FIQH: THE "CANONICAL" IMĀMĪ COLLECTIONS OF AKHBĀR
Authors: Gleave Robert
Published: July 2002

In Imāmī legal theory, the akhbār of the Imams form one of the material sources of law, alongside the Qur'ān and Prophetic hadīths. The akhbār are presented in compendia, assembled by Shi'ite collectors in the fourth and fifth century AH/tenth and eleventh century CE, four of which subsequently came to be regarded as "canonical" in Imāmī law. In this essay, I examine the processes at work in the collation of these "canonical" akhbār collections. These processes, I argue, were influenced by an emerging juristic tradition in Imāmī Shi'ism. As Imāmī thinkers became increasingly concerned with fiqh and the elucidation of the Sharī'a, the collectors developed new techniques of selection, presentation and organisation. The akhbār collections became a material source upon which jurists could draw in their fiqh discussions, rather than the law itself. As an example of the processes at work in the collection and presentation of akhbār, I examine the issue of tayammum, ritual purification by sand rather than water.
MUSLIM ORPHANS AND THE SHARĪ'A IN OTTOMAN PALESTINE ACCORDING TO SIJILL RECORDS
Authors: Yazbak Mahmoud
Published: July 2002

According to sharī'a, an orphan is an under-aged infant or child, until the age of puberty, whose father or both his/her parents have died. In the sijill cases (Muslim court records) under study here, under-aged children who lost their mother are not defined as orphans. This way of defining orphans reflects the different socio-economic roles fathers and mothers played. This paper, depending essentially upon the sijillāt of Nablus, Jerusalem and Haifa during the Ottoman period, investigates the social status of the orphans, how families and relatives acted, and how the sharī'a court fulfilled its job in this sphere. Selon la sharī'a, un orphelin est un enfant mineur, n'ayant pas atteint l'âge de la puberté, dont le père ou les deux parents sont décédés. Parmi les cas notés dans les sijill (registres des tribunaux) étudiés ici, les mineurs ayant perdu leur mère ne sont pas considérés comme des orphelins. Cette définition de l'orphelin reflète les différents rôles socio-économiques du père et de la mère. La présente étude est fondée sur l'exploitation des documents des registres des tribunaux de Naplouse, Jérusalem et Haïfa à l'époque ottomane. Elle examine le statut social des orphelins, les comportements des familles et parents proches à leur égard et également le fonctionnement du tribunal dans ce domaine.
THE COSMIC JOURNEY OF ODYSSEUS
Authors: Marinatos Nanno
Published: July 2002

In vain have scholars tried to produce a coherent geographical picture of Odysseus' travels. It is argued here that Odysseus makes a cosmic journey at the edges of the earth (perata ges), a phrase used in the text to describe several lands that the hero visits. The cosmic journey was a genre current in the East Mediterranean region in the Iron Age. It was modeled on the Egyptian the journey of the sun god who travels twelve hours in the darkness of the underworld and twelve hours in the sky. Evidence of similar concepts in the Near East is provided by a Babylonian circular map (now in the British Museum) as well as by Phoenician circular bowls. Gilgamesh seems to perform a cosmic journey. As well, Early Greek cosmology utilizes the concept of a circular cosmos. Odysseus' journey spans the two cosmic junctures of the universe: East, where Circe resides, and West, where Calypso lives. Another polar axis is the underworld and the island of the sun.
VIRGIN-MALE MATING ADVANTAGE IN SAGEBRUSH CRICKETS: DIFFERENTIAL MALE COMPETITIVENESS OR NON-INDEPENDENT FEMALE MATE CHOICE?
Authors: Sakaluk Scott , Ivy Tracie
Published: July 2002

Female sagebrush crickets (Cyphoderris strepitans) feed on males' fleshy hind wings during copulation and ingest haemolymph oozing from the wounds they inflict. The wounds are not fatal and usually only a portion of the hind wings are eaten at any one mating, so that mated males are not precluded from mating again. However, based on their relative abundance in the population, virgin males have a higher mating success than non-virgin males. One explanation for this virgin-male mating advantage is that non-virgin males, having been depleted of their energy reserves through the wing-feeding behaviour of their mates, are unable to sustain the same level of acoustic signalling they produce prior to copulation. Previous assays of male signalling behaviour have provided some support to this hypothesis. However, an alternative explanation is that females actively seek out virgin males as mates because of the greater material resources they offer. If the acoustic structure of males' signals were systematically altered by the loss of hind-wing material underlying the sound-producing tegmina, females could potentially discriminate against mated males through reduced phonotaxis to their calls. We tested this hypothesis by experimentally removing one hind wing from virgin males, thereby simulating the non-virgin condition without the attendant costs of copulation. We compared the mating success of these 'asymmetrical' males with that of sham-operated virgin males when competing under natural conditions. In a companion laboratory study, we used time-lapse video recording to examine the possibility that female preferences are exerted only after pair formation has occurred. There was no significant difference in male mating success across treatments in either study. We conclude, therefore, that the virgin-male mating advantage does not stem from an acoustically mediated, non-independent female mating preference, but rather, from the differential competitiveness of males.
DUET SONGS OF THE SIAMANG, HYLOBATES SYNDACTYLUS: II. TESTING THE PAIR-BONDING HYPOTHESIS DURING A PARTNER EXCHANGE
Authors: Geissmann Thomas
Published: July 2002

It has repeatedly been suggested for several duetting bird and primate species that duetting might act as a reinforcement of the pair bond. Until now, it has apparently not been demonstrated that the premises underlying the pair-bonding hypothesis are met by any duetting species. Siamangs (Hylobates syndactylus) are monogamous apes which produce long and complex duet songs. This study analyses the changes in duet structure in two pairs of siamangs during a forced partner exchange. The duet songs of the siamangs underwent many notable changes during partner exchange. Of 33 different variants of the great call sequence, 29% in one pair and 21% in the other were restricted to the first stage just after the partner exchange. Some of these changes were certainly due to individualistic traits of the new partner, and for some other changes, this possibility cannot be reliably excluded. At least two changes, however, can only be interpreted in terms of a learning effort by which one partner adapts its duetting behaviour to that of its new mate. The two newly formed pairs of this report appear to be the first documented cases to fulfil the requirements underlying Wickler's (1980) pair-bonding hypothesis: The animals under study were showing a stable song pattern with pair-specific traits. After the partner exchange, new pair-specific traits occurred, some of them obviously achieved through a partner-directed effort of one or both individual(s). Moreover, the pair-bonding hypothesis appears to be one of the few biological functions suggested so far which could explain a high degree of duet-complexity as adaptive. However, the loudness of the siamang song alone suggests that other functions are also involved. These are most probably related to territorial advertisement, pair bond advertisement and (possibly) mate attraction.
Paratylenchinae: evaluation of diagnostic morpho-biometrical characters of females in the genus Paratylenchus Micoletzky, 1922 (Nematoda: Tylenchulidae)
Authors: Háněl Ladislav , Brzeski Michał
Published: July 2002

Examination of morphological variability within single female lines of Paratylenchus microdorus, P. straeleni, P. bukowinensis and P. projectus showed that females offer a limited number of characters useful for differentiation of similar species. The most stable were index V, followed by stylet length, conus length and index m. The most variable were tail length and shape, indices c' and c, and these are considered unreliable for separation of similar species. It is concluded that the description of a Paratylenchus species should be based on adults of both sexes as well as resistant juvenile stage.L'étude de la variabilité morphologique dans des lignées issues d'une femelle de Paratylenchus microdorus, P. straeleni, P. bukowinensis et P. projectus a montré que les femelles possédaient un nombre limité de caractères utiles pour la différenciation d'espèces proches. Les plus stables sont le rapport V, puis la longueur du stylet, la longueur du cône et le rapport m. Les plus variables sont la longueur et la forme de la queue, les rapports c' et c, ces caractères étant considérés comme inutilisables pour séparer des espèces proches. Il en découle que la description d'une espèce de Paratylenchus devrait être fondée tant sur les adultes des deux sexes que sur les stades juvéniles résistants.
The effect of clay minerals on the formation of goethite and hematite from ferrihydrite after 16 years’ ageing at 25°C and pH 4 – 7
Authors: Schwertmann U. , Friedl J. , Stanjek H. , Schulze D. G.
Published: July 2002

In soils and other weathering environments, hematite and goethite are usually formed in the presence of clay minerals. Two-line ferrihydrite was aged in the presence of six different clay minerals in aqueous suspension at 25°C and pH 4, 5, 6 and 7 for 16 years. The transformation into hematite/goethite mixtures was complete in the systems with gibbsite, kaolinite, illite and smectite, but incomplete in those with soil smectite and allophane. Soil smectite and allophane, as well as increasing pH, favoured hematite over goethite. The grainy and multi-domainic hematite crystals in the allophane system contained Si and Al (EDX) and showed a Si – O vibration at ∼920 cm– 1(FTIR). The unit-cell contraction due to structural Al was counteracted by structural OH, which was removed at 200°C. Heating also increased the magnetic hyperfine field at RT by 1.2 – 1.6 T. Hematite crystals with irregular shape and grainy interior have also been observed in soils.
Influence of the Ti precursor on the properties of Ti–pillared smectites
Authors: Vicente M. A. , Bañares-Muñoz M. A. , Toranzo R. , Gandía L. M. , Gil A.
Published: July 2002

The pillaring of smectites (two saponites and a montmorillonite) with various Ti precursors was studied. The minerals were intercalated with ‘classical ’ Ti precursors, such as titanium tetrachloride and titanium tetraethoxide, and also with new precursors, such as solutions of titanium tetraisopropoxide in acetic acid, or titanium (bis (ethylacetoacetato) diisopropoxide) in acetone. A complete characterization of the intercalated solids was carried out and a comparison of the properties of the solids as a function of the precursors used in the intercalation established. The influence of the severe conditions in which the intercalation with Ti oligomers is usually carried out (low pH and/or high temperature) on the properties of the intercalated solids was analysed. Intercalation with TiCl4 and Ti(EtO)4 strongly affected the structure of the clays, not by acid attack on the octahedral sheet, but mainly by disaggregation of particles. Ti(isop)4 was found to be less aggressive for the clays, while Ti(etacet)2(isop)2 did not form pillared solids but organo-clays, and therefore was of no use as a pillaring agent. The solids were thermally stable up to 300°C, showing a high specific surface area.
The origins of kaolinite-rich rocks associated with coal measures in China
Authors: Liu Qinfu , Spears D. A. , Zhang Pengfei , Xu Hongliang
Published: July 2002

Kaolinite-rich rocks are widespread in Chinese coal-bearing strata. Three main types of deposits are recognized. Those deposits identified as flint clays are several metres thick and show lateral variations in bed composition. The kaolinite is thought to have formed mainly on the adjacent landmass, but some crystallization of gels within the basin is not ruled out. Tonsteins, which formed from the in situ alteration of airfall volcanic ashes, are very common in the coal measures and are up to 0.5 m thick. Finally, kaolinite deposits are described where the development of kaolin is related to weathering of coals either close to or at the present land surface.
The role of argillic alteration in the zeolitization of volcanic glass
Authors: Leggo P. J. , Cochemé J.-J. , Demant A. , Lee W. T.
Published: July 2002

The pseudomorphic replacement of glass shards by zeolite minerals is a common feature of volcanoclastic sediments. In the majority of cases the initial stage of this reaction is the alteration of the glass surface to a clay mineral or celadonite after which the bulk of the glass is altered to zeolite. This replacement feature is seen particularly well in glass of rhyolitic composition; the zeolite mineral usually being clinoptilolite. Volcanoclastic rocks of Oligocene age exposed in the Rhodope Massif, Bulgaria offered an opportunity to study this reaction experimentally as rocks containing unaltered glass shards are known to be close stratigraphic equivalents of zeolitized tuffs and in this respect are considered to be precursor rocks. Low-temperature hydrothermal reactions conducted on the unaltered glass, which had been clay coated in the laboratory, demonstrates the importance of the clay-glass interface. An hypothesis is put forward to explain this type of zeolitization process and a distinction is drawn between these rocks and other sediments in which zeolite minerals form from volcanic glass without the presence of a clay interface.
Depletion of circulating α2-antiplasmin by intravenous plasmin or immunoneutralization reduces focal cerebral ischemic injury in the absence of arterial recanalization
Authors: Nagai Nobus , De Mol Maria , Van Hoef Berthe , Verstreken Maria , Collen Désiré
Published: July 2002

In the absence of arterial recanalization, thrombolytic agents induce a dose-related extension of focal cerebral ischemic injury (FII) in experimental animals. However, FII is smaller in mice lacking α2-antiplasmin (α2-AP), the physiologic inhibitor of plasmin, suggesting its depletion might reduce FII in the absence of reperfusion. Therefore, the effect of human plasmin (Pli), human miniplasmin (mPli), and an Fab fragment neutralizing murine α2-AP (Fab-4H9) on FII after middle cerebral artery (MCA) ligation was studied in mice and in hamsters. In BALB/c mice, the median FII after 24 hours was 28 μL (range, 20-34) (n = 10) with saline and 23 μL (range, 17-26) (n = 9) with a single bolus of 0.07 mg Pli, given after MCA ligation (P = .010), which reduced α2-AP to 44% and fibrinogen from 0.75 to 0.44 g/L. FII was 20 μL (range, 13-26) (n = 6, P = .025) with 0.2 mg mPli and was 24 μL (range, 20-27) (n = 6,P = .020) with 1.7 mg Fab-4H9. Neuronal atrophy and reduction of laminin immunoreactivity were comparably observed in the infarct area after saline and Pli. In hamsters, a single bolus injection of 1 mg Pli, after MCA ligation, depleted α2-AP and fibrinogen and reduced FII at 24 hours from 20 μL (range, 9.9-38) (n = 6) to 7.0 μL (range, 0.44-31) (n = 7,P = .032). Thus, reduction of circulating α2-AP, with a single bolus of plasmin or of a neutralizing antibody fragment, significantly reduced FII after MCA ligation in mouse and hamster models, suggesting that, provided these observations can be extrapolated to human beings, transient depletion of circulating α2-AP might reduce ischemic stroke in the absence of reperfusion.
Role of galactosylation in the renal pathogenicity of murine immunoglobulin G3 monoclonal cryoglobulins
Authors: Mizuochi Tsuguo , Pastore Yves , Shikata Kohdoh , Kuroki Aki , Kikuchi Shuichi , Fulpius Thierry , Nakata Munehiro , Fossati-Jimack Liliane , Reininger Luc , Matsushita Misao , Fujita Teizo , Izui Shozo
Published: July 2002

Cryoglobulin activity associated with murine immunoglobulin G3 (IgG3) has been shown to play a significant role in the development of murine lupuslike glomerulonephritis. A fraction, but not all, IgG3 monoclonal antibodies are capable of inducing a severe acute lupuslike glomerulonephritis as a result of direct localization of IgG3 cryoglobulins, suggesting the importance of qualitative features of cryoglobulins in their nephritogenic activities. Here a remarkable difference is shown in the renal pathogenicity of 2 murine IgG3 monoclonal cryoglobulins, identical in the amino acid sequences of their heavy and light chains but different in galactosylation patterns of oligosaccharide side chains because of their synthesis in different myeloma cells. The antibody lacking the capacity to induce severe glomerulonephritis displayed an increased proportion of galactosylated heavy chains. Changes in conformation, as revealed by gel filtration analysis, reduced cryoglobulin activity, and accelerated clearance could account for the lack of the renal pathogenicity of the more galactosylated variant. This observation provides a direct demonstration for the role of IgG galactosylation in the pathogenic potential of cryoglobulins.
Differential requirements for the O-linked branching enzyme core 2 β1-6-N-glucosaminyltransferase in biosynthesis of ligands for E-selectin and P-selectin
Authors: Snapp Karen R. , Heitzig Christine E. , Ellies Lesley G. , Marth Jamey D. , Kansas Geoffrey S.
Published: July 2002

Selectins are carbohydrate-binding adhesion molecules that play important roles in control of leukocyte traffic. Glycosyltransferases involved in selectin ligand biosynthesis include the α1,3-fucosyltransferases FucT-VII and FucT-IV, one or more sialyltransferases, and at least one O-linked branching enzyme. Previous studies have shown that core 2 β1-6-N-glucosaminyltransferase (C2GlcNAcT-I; EC 2.4.1.102) is required for functional modification of PSGL-1, the leukocyte P-selectin ligand, but have been ambiguous on whether this enzyme is involved in E-selectin ligand formation. Using an attachment and rolling assay under defined shear flow in vitro, this study shows that C2GlcNAcT-I− lymphoid cells stably transfected with FucT-VII complementary DNA attach and roll well on E-selectin at 1.5 dynes/cm.2 Further, attachment and rolling on P-selectin of neutrophils is sharply reduced and that of short- term polarized Th1 cells is virtually abolished, with leukocytes from C2GlcNAcT-I−/− mice. In contrast, both neutrophils and Th1 cells from C2GlcNAcT-I−/− mice attach and roll as well as wild-type cells on E-selectin. These results show that C2GlcNAcT-I is selectively required for biosynthesis of ligands for P-selectin, but is not essential for at least some E-selectin ligands. Distinct requirements for C2GlcNAcT-I in the formation of ligands for E-selectin versus P-selectin represents a novel level of regulation of expression of selectin ligands and lymphocyte traffic.
Epithelial membrane protein 2, a 4-transmembrane protein that suppresses B-cell lymphoma tumorigenicity
Authors: Wang Chun-Xiang , Wadehra Madhuri , Fisk Bernard C. , Goodglick Lee , Braun Jonathan
Published: July 2002

A murine homologue of the epithelial membrane protein 2(EMP2) gene was identified in a search for genes associated with B-cell lymphoma tumorigenicity by using suppression subtractive hybridization. Expression of EMP2 messenger RNA in primary mouse tissues was limited to certain epithelial cell types and the peritoneal lymphoid compartment. EMP2 was expressed in the poorly tumorigenic DAC B-lymphoma cell line but was significantly down-regulated in a subline selected for in vivo tumor formation in Balb/c mice. Recombinant restoration of EMP2 expression in the subline suppressed its tumorigenicity, suggesting that loss ofEMP2 was a causal factor in the malignant phenotype. Recombinant overexpression of EMP2 was studied in B lymphoma and NIH3T3 cells. EMP2 in both cell types induced cell death on serum deprivation. EMP2-induced cell death correlated with the expression level of EMP2 protein and was prevented by caspase inhibitors Z-VAD and Z-DEVD. These findings for the first time describe an apoptotic effect of a GAS3family gene in lymphocytes. They also suggest that EMP2 may influence B-lymphoma tumorigenicity through a functional tumor suppressor phenotype.
H4(D10S170), a gene frequently rearranged in papillary thyroid carcinoma, is fused to the platelet-derived growth factor receptor β gene in atypical chronic myeloid leukemia with t(5;10)(q33;q22)
Authors: Schwaller Juerg , Anastasiadou Ema , Cain Danielle , Kutok Jeff , Wojiski Sarah , Williams Ifor R. , LaStarza Roberta , Crescenzi Barbara , Sternberg David W. , Andreasson Patrick , Schiavo Roberta , Siena Salvatore , Mecucci Cristina , Gilliland D. Gary
Published: July 2002

The molecular cloning of the t(5;10)(q33;q22) associated with atypical chronic myeloid leukemia (CML) is reported. Fluorescence in situ hybridization (FISH), Southern blot, and reverse transcriptase– polymerase chain reaction analysis demonstrated that the translocation resulted in an H4/platelet-derived growth factor receptor βR (PDGFβR) fusion transcript that incorporated 5′ sequences from H4 fused in frame to 3′PDGFβR sequences encoding the transmembrane, WW-like, and tyrosine kinase domains. FISH combined with immunophenotype analysis showed that t(5;10)(q33;q22) was present in CD13+ and CD14+ cells but was not observed in CD3+ or CD19+ cells. H4 has previously been implicated in pathogenesis of papillary thyroid carcinoma as a fusion partner of RET. The H4/RET fusion incorporates 101 amino acids of H4, predicted to encode a leucine zipper dimerization domain, whereas the H4/PDGFβR fusion incorporated an additional 267 amino acids of H4. Retroviral transduction of H4/PDGFβR, but not a kinase-inactive mutant, conferred factor-independent growth to Ba/F3 cells and caused a T-cell lymphoblastic lymphoma in a murine bone marrow transplantation assay of transformation. Mutational analysis showed that the amino-terminal H4 leucine zipper domain (amino acids 55-93), as well as H4 amino acids 101 to 386, was required for efficient induction of factor-independent growth of Ba/F3 cells. Tryptophan-to-alanine substitutions in the PDGFβR WW-like domain at positions 566/593, or tyrosine-to-phenylalanine substitutions at PDGFβR positions 579/581 impaired factor-independent growth of Ba/F3 cells. H4/PDGFβR is an oncoprotein expressed in t(5;10)(q33;q22) atypical CML and requires dimerization motifs in the H4 moiety, as well as residues implicated in signal transduction by PDGFβR, for efficient induction of factor-independent growth of Ba/F3 cells.
Bone morphogenetic protein-4 inhibits proliferation and induces apoptosis of multiple myeloma cells
Authors: Hjertner Öyvind , Hjorth-Hansen Henrik , Börset Magne , Seidel Carina , Waage Anders , Sundan Anders
Published: July 2002

Bone morphogenetic proteins (BMPs) can be isolated from organic bone matrix and are able to initiate de novo cartilage and bone formation. Here it is shown that BMP-4 inhibited DNA synthesis in a dose-dependent manner in 3 IL-6–dependent multiple myeloma (MM) cell lines (OH-2, IH-1, and ANBL-6). In contrast, no effect on DNA synthesis was observed in 3 IL-6–independent MM cell lines (JJN-3, U266, and RPMI 8226). BMP-4 induced cell cycle growth arrest in the G0/G1 phase in OH-2 and ANBL-6 cells but not in IH-1 cells. BMP-4 induced apoptosis in OH-2 and IH-1 cells, but not significantly in ANBL-6 cells. Furthermore, BMP-4 induced apoptosis in freshly isolated MM cells from 4 of 13 patients. In the OH-2 and ANBL-6 cell lines and in a patient sample, immunoblotting showed that BMP-4 down-regulated IL-6–induced tyrosine phosphorylation of Stat3, suggesting a mechanism for the apparent antagonism between IL-6 and BMP-4. BMP-4 or analogues may be attractive therapeutic agents in MM because of possible beneficial effects on both tumor burden and bone disease.
A novel syndrome of variant leukocyte adhesion deficiency involving defects in adhesion mediated by β1 and β2 integrins
Authors: Harris Estelle S. , Shigeoka Ann O. , Li Wenhua , Adams Roberta H. , Prescott Stephen M. , McIntyre Thomas M. , Zimmerman Guy A. , Lorant Diane E.
Published: July 2002

Leukocyte adhesion deficiency type I (LAD-1) is a disorder associated with severe and recurrent bacterial infections, impaired extravascular targeting and accumulation of myeloid leukocytes, altered wound healing, and significant morbidity that is caused by absent or greatly diminished surface expression of integrins of the β2 class. We report clinical features and analysis of functions of cells from a patient with a myelodysplastic syndrome and infectious complications similar to those in the severe form of LAD-1, but whose circulating neutrophils displayed normal levels of β2 integrins. Analysis of adhesion of these cells to immobilized ligands and to endothelial cells and assays of cell-cell aggregation and chemotaxis demonstrated a profound defect in adhesion mediated by β2 integrins indicative of a variant form of LAD-1. A novel cell line established from Epstein-Barr virus–transformed lymphoblasts from the subject demonstrated deficient β2 integrin–dependent adhesive function similar to that of the primary leukocytes. In addition, these cells had markedly impaired β1 integrin–dependent adhesion. Sequence analysis and electrophoretic mobility of β1 and β2 proteins from the cell line demonstrated that the defects were not a result of structural abnormalities in the integrin subunit chains themselves and suggest that the adhesive phenotype of these cells is due to one or more abnormalities of inside-out signaling mechanisms that regulate the activity of integrins of these classes. These features define a unique LAD-1 variant syndrome that may reveal important insights that are generally relevant to inside-out signaling of integrins, a molecular process that is as yet incompletely understood.
Fas-L up-regulation by highly malignant myeloma plasma cells: role in the pathogenesis of anemia and disease progression
Authors: Silvestris Franco , Tucci Marco , Cafforio Paola , Dammacco Franco
Published: July 2002

Highly malignant myeloma cells up-regulate their Fas-ligand (Fas-L) to escape immune surveillance by Fas+ cytotoxic cells. Here it is demonstrated that this abnormality is involved in the pathogenesis of the severe anemia associated with progression of multiple myeloma (MM). By measuring Fas and Fas-L in plasma cells and erythroblasts from 19 MM patients and 5 with monoclonal gammopathies of undetermined significance (MGUS), it was found that both Fas-L+ myeloma cells and Fas+ erythroid progenitors were significantly increased in patients with stage III MM whose erythroblasts, cultured in the presence of autologous plasma cells or their supernatant, underwent prompt apoptosis as evaluated by propidium iodide staining, the TUNEL assay, and detection of the APO2.7-reactive mitochondrial antigen. Flow cytometry of fresh erythroblasts revealed a considerable expression of the caspases CPP32 and FLICE in both their constitutive proenzymatic forms and in cleaved subunits. By contrast, their intracytoplasmic expression was defective in patients with inactive disease and MGUS controls. The evidence that Fas-L+ myeloma clones directly prime erythroblast apoptosis in vivo was further supported by the occurrence of fluorescein isothiocyanate–TUNEL+ erythroblasts juxtaposed to myeloma cells in bone marrow smears. These results strongly suggest that the deregulated apoptosis in myeloma clones plays an active role in the progressive destruction of the erythroid matrix by a cytotoxic mechanism based on up-regulation of Fas-L.
Inhibition of antigen-receptor signaling by Platelet Endothelial Cell Adhesion Molecule-1 (CD31) requires functional ITIMs, SHP-2, and p56lck
Authors: Newman Debra K. , Hamilton Christin , Newman Peter J.
Published: July 2002

Platelet Endothelial Cell Adhesion Molecule-1 (PECAM-1, CD31) is a 130-kd member of the immunoglobulin gene superfamily that is expressed on the surface of platelets, endothelial cells, myeloid cells, and certain lymphocyte subsets. PECAM-1 has recently been shown to contain functional immunoreceptor tyrosine-based inhibitory motifs (ITIMs) within its cytoplasmic domain, and co-ligation of PECAM-1 with the T-cell antigen receptor (TCR) results in tyrosine phosphorylation of PECAM-1, recruitment of Src homology 2 domain-containing protein tyrosine phosphatase-2 (SHP-2), and attenuation of TCR-mediated cellular signaling. To determine the molecular basis of PECAM-1 inhibitory signaling in lymphocytes, the study sought to (1) establish the importance of the PECAM-1 ITIMs for its inhibitory activity, (2) determine the relative importance of SHP-2 versus SHP-1 in mediating the inhibitory effect of PECAM-1, and (3) identify the protein tyrosine kinases required for PECAM-1 tyrosine phosphorylation in T cells. Co-ligation of wild-type PECAM-1 with the B-cell antigen receptor expressed on chicken DT40 B cells resulted in a marked reduction of calcium mobilization—similar to previous observations in T cells. In contrast, co-ligation of an ITIM-less form of PECAM-1 had no inhibitory effect. Furthermore, wild-type PECAM-1 was unable to attenuate calcium mobilization in SHP-2–deficient DT40 variants despite abundant levels of SHP-1 in these cells. Finally, PECAM-1 failed to become tyrosine phosphorylated in p56lck-deficient Jurkat T cells. Together, these data provide important insights into the molecular requirements for PECAM-1 regulation of antigen receptor signaling.