bluuebunny/crossref_metadata_2025 huggingface dataset:
The loss of calretinin expression indicates aganglionosis in Hirschsprung’s disease
Authors: Barshack I , Fridman E , Goldberg I , Chowers Y , Kopolovic J
Published: June 2004

Background:Hirschsprung’s disease (HD) is a congenital disorder characterised by the absence of ganglion cells in the large bowel, leading to functional obstruction and colonic dilatation proximal to the affected segment. A subclass of nerve cell bodies in both submucosa and myenteric ganglia of the human gastrointestinal tract were found to show immunopositivity for calretinin, a calcium binding protein, which plays an important role in the organisation and functioning of the central nervous system.

Aim:To investigate calretinin immunostaining in ganglionic and aganglionic HD colon specimens, and compare it with staining for S100, neurone specific enolase, and c-kit.

Methods:Ten large bowel, full thickness specimens from patients with classic rectosigmoid HD were selected from the pathology repository. In total, 54 paraffin wax blocks—24 from the ganglionic zone, 17 from the aganglionic zone, and 13 from the transitional zone—were processed.

Results:Calretinin was not expressed in aganglionic segments of HD and associated nerve fibres, whereas in ganglionic HD segments and in normal colon both ganglion cells and nerve fibres were immunopositive. In addition, c-kit showed an altered distribution in the interstitial cells of Cajal. The transitional zone showed a broad spectrum of histomorphological and immunohistochemical patterns of both calretinin and c-kit expression.

Conclusion:The absence of calretinin expression may serve as a diagnostic aid in identifying aganglionic segments in HD.
Cytomegalovirus infection of the cervix: morphological observations in five cases of a possibly under-recognised condition
Authors: McGalie C E , McBride H A , McCluggage W G
Published: June 2004

Aims:Histologically diagnosed cytomegalovirus (CMV) infection of the cervix is rare and the associated morphological features are not well described. This study describes histopathological findings in five biopsies from four patients with CMV cervicitis.

Methods:CMV inclusions were identified in five cervical biopsies from four patients in a single institution over eight months. The clinical notes were reviewed, the morphological features documented, and immunohistochemical staining for CMV performed. CMV immunohistochemical staining was also performed on 30 consecutive cervical biopsies in which inclusions were not seen histologically.

Results:None of the patients was immunocompromised but one was postnatal. Numbers of CMV inclusions ranged from occasional to abundant and they were located mainly in endocervical glandular epithelial cells but also in endothelial and mesenchymal cells. Inclusions were not seen in squamous cells. Inclusions were eosinophilic and were intracytoplasmic rather than intranuclear. They were positive immunohistochemically for CMV. Associated morphological features included fibrin thrombi within small blood vessels (three cases), dense active inflammatory infiltrates (five cases), lymphoid follicles (two cases), vacuolation of glandular epithelial cells (two cases), and reactive changes in glandular epithelial cells (two cases). CMV inclusions were not identified in the 30 additional cases that underwent immunohistochemical staining.

Conclusions:CMV infection of the cervix may be more common than is thought. Patients are usually immunocompetent and require no treatment. Morphological features such as a dense inflammatory cell infiltrate with lymphoid follicles, and especially fibrin thrombi within small vessels, should alert the pathologist to look closely for the pathognomonic CMV inclusion bodies.
Evaluation of swab transport systems against a published standard: Table 1
Authors: Human R P , Jones G A
Published: June 2004

Background:Before the publication of the M40-A standard by the United States National Committee for Clinical Laboratory Standards (NCCLS), no quality control data for swab transport systems (STSs) had been available.

Aims:To compare three commercially available STSs against the published standard to ascertain bacterial survival after a set holding time.

Method:Charcoal and non-charcoal containing swabs were inoculated with standard volumes and numbers of a range of bacteria commonly isolated from clinical material. Bacterial counts were taken at time zero, six, 24, and 48 hours, with the results being compared against the NCCLS standard.

Results:The standard clearly differentiated between the three STSs tested, with one product being superior to the other two products in providing better survival.

Conclusion:The standard now provides manufacturers and users of STSs with meaningful data to provide, purchase, and compare an STS for routine clinical use.
Comparative analysis of balsam fir wetwood, heartwood, and sapwood properties
Authors: Jeremic Dragica , Cooper Paul , Srinivasan Usha
Published: June 2004

Physical, anatomical, chemical, and microbiological properties of wetwood in heartwood were compared with those of sapwood and normal heartwood in balsam fir (Abies balsamea (L.) Mill.). Wetwood found only in heartwood of balsam fir had significantly higher moisture content (MC) than normal heartwood but not significantly higher MC than sapwood. No differences in relative density or shrinkage properties were found among tissue types. Wetwood tissue needed longer times to dry to an equilibrium MC of 15%, not only because of its high initial MC, but also because of its lower moisture permeability (diffusion coefficient) in this particular MC range (from initial MC to 15% equilibrium MC). However, there were no significant differences in drying rates for the different tissues when drying from 15% MC to 8% MC. Anatomically, wetwood is similar to normal heartwood, and it has no distinctive characteristics except a greater frequency of bacteria. Energy dispersive X-ray analysis showed that all of the tissues contained the same inorganic elements. Both high-performance liquid chromatography and ash analysis showed that wetwood is chemically closer to normal heartwood than to sapwood. Wetwood was significantly more acidic than either normal heartwood or sapwood. A large number of bacterial genera were found in all three tissues, but there were no consistent or significant differences in bacterial presence or activity among tissue types.
An experimental demonstration of stem damage as a predictor of fire-caused mortality for ponderosa pine
Authors: Mantgem Phillip van , Schwartz Mark
Published: June 2004

We subjected 159 small ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) to treatments designed to test the relative importance of stem damage as a predictor of postfire mortality. The treatments consisted of a group with the basal bark artificially thinned, a second group with fuels removed from the base of the stem, and an untreated control. Following prescribed burning, crown scorch severity was equivalent among the groups. Postfire mortality was significantly less frequent in the fuels removal group than in the bark removal and control groups. No model of mortality for the fuels removal group was possible, because dead trees constituted <4% of subject trees. Mortality in the bark removal group was best predicted by crown scorch and stem scorch severity, whereas death in the control group was predicted by crown scorch severity and bark thickness. The relative lack of mortality in the fuels removal group and the increased sensitivity to stem damage in the bark removal group suggest that stem damage is a critical determinant of postfire mortality for small ponderosa pine.
Effect of water stress on germination of beechnuts treated before and after storage
Authors: Falleri Elisabetta , Muller Claudine , Laroppe Elyane
Published: June 2004

Beechnuts from two seedlots were pretreated, without medium, at a controlled moisture content (MC) of 30% before or after 1-year storage at 7 °C. Seeds treated with the two methods were germinated on substrates at decreasing osmotic potential down to 1.2 MPa. A moderate stress of 0.2 MPa caused a slight but significant decrease in germination percentage. Each further increment in water stress produced additional significant decreases in germination capacity. At 1.2 MPa, germination was almost prevented. Seeds pretreated before storage showed lower germination percentage and speed at all osmotic potentials, but this result was due to a marked effect of seed initial MC, rather than a lower resistance to water deficit. In fact, MC of beechnuts pretreated before storage was 8%, whereas beechnuts pretreated after storage started germination tests under water stress with an initial MC of 30%. Moreover, seeds at lower initial MC need more time to imbibe before the germination process can start. Seeds with higher initial MC were probably able to cope better with water deficit, at least during the 30-day germination test in the laboratory. A second experiment carried out on beechnuts treated only before storage but made to have different initial MC seemed to confirm this conclusion. Ungerminated seeds were not damaged, as revealed by a tetrazolium test performed at the end of each germination test. Advantages in nursery practice shown by dry, nondormant beechnuts (pretreated before storage) are discussed in relation to the possibility of sowing when water availability in the soil is not a limiting factor.
Timber production versus old-growth preservation with endogenous prices and forest age-classes
Authors: Tahvonen Olli
Published: June 2004

This study combines timber production and environmental values, applying a dynamic forest-level economic model with any number of forest age-classes. The model includes endogenous timber price or nonlinear harvesting costs and various possibilities to specify the dependence of environmental values (related e.g. to species persistence) on the forest age-class structure. The nonlinearities in the net benefits from timber production have the consequence that fluctuations in optimal timber harvesting may totally vanish or at least become smaller than in forest scheduling models without ad hoc even flow constraints. If environmental values are specified to depend on the fraction of forest land preserved as old growth, the optimal long run allocation between timber production and old growth is represented by an equilibrium continuum. Thus the optimal long run allocation depends on the initial age-class distribution. The continuum and the dependence of initial age-class distribution vanish when the rate of discount approaches zero. If the environmental values of age-classes increase smoothly with age, the long run equilibrium may simultaneously include multiple rotation periods. The model determines the optimality of producing timber and environmental values separately at different parts of the forest or at the same piece of forest land. Numerical computation suggests that the optimal solution always converges toward some optimal long run stationary age-class distribution.
Genetic variation in veneer quality and its correlation to growth in white spruce
Authors: Zhang S Y , Yu Qibin , Beaulieu Jean
Published: June 2004

This study investigated the genetic variation in veneer quality of white spruce (Picea glauca (Moench) Voss) and its correlation with tree growth and wood density. A total of 270 sample trees from 35 families were harvested from 36-year-old provenance-progeny trials at two sites through a thinning operation. A 36-cm long bolt was collected from each sample tree at an 8-foot (or 2.45 m) height for this veneer quality study. The results indicate that conversion of fast-grown white spruce into veneer and plywood may present some problems. Low wood density, numerous knots, and possibly a high proportion of juvenile wood appear to be major factors contributing to low veneer stress grading, resulting in a production of low-quality veneer. This study also showed that the environmental factors at the two sites played an important role in determining veneer quality and tree radial growth. The narrow-sense heritability for veneer density, veneer modulus of elasticity, and veneer roughness were 0.62, 0.13, and 0.14, respectively. The results revealed considerable phenotypic variation and relatively high additive genetic variation in the veneer modulus of elasticity. The phenotypic and genetic correlations between ring width and veneer density or veneer modulus of elasticity were negative. A positive phenotypic and genetic correlation was found between veneer density and veneer modulus of elasticity. This suggests that selection for tree volume growth in white spruce would lead to a decrease in wood density and veneer stiffness.
Harvest retention patches are insufficient as stand analogues of fire residuals for litter-dwelling beetles in northern coniferous forests
Authors: Gandhi Kamal JK , Spence John R , Langor David W , Morgantini Luigi E , Cryer Karen J
Published: June 2004

We compared litter-dwelling beetle assemblages of <1- to 2-ha unharvested coniferous patches embedded in 1-year-old clearcuts with beetle assemblages from <1- to 10-ha unburned fire residuals within 15- and 37-year-old burned forests. Our primary objective was to determine whether unharvested patches retain biotic elements that are similar to those of the surrounding uncut forests and to those of patches of forest skipped by wildfires. Beetle assemblages of the harvest residuals were similar to those of the uncut forest, suggesting that harvest residuals retain elements of the mature forest. However, beetle assemblages of harvest residuals differed from those of fire residuals. Thus, harvest residuals sited without regard to microhabitat characteristics or stand structure in fire residuals are insufficient analogues for the late successional habitats provided by fire residuals. There was no relationship between size of harvest residuals and either beetle catch or diversity. Beetle catches were higher in round harvest residuals, and a number of forest species also appeared to be aggregated in round residuals. Forest managers may preserve biotic elements of young uncut forest by leaving round harvest residuals in clearcuts; however, a closer habitat match between harvest and fire residuals is likely required to preserve and maintain landscape-level forest biodiversity.
Quercus michauxii regeneration in and around aging canopy gaps
Authors: Battaglia L L , Collins B S , Weisenhorn P B
Published: June 2004

Floodplain forests are subject to frequent windstorms, which create canopy gaps and microtopographic heterogeneity. Forest regeneration may be enhanced when light and microtopographic conditions are both favorable, but slower growing canopy species may still require multiple disturbance events to reach the canopy. In 2001, we revisited a cohort of Quercus michauxii Nutt. seedlings planted in 1995 on pitmound microsites that were constructed in and around canopy gaps to determine patterns of seedling persistence and investigate the effects of canopy openness and microtopography on seedling survival and growth. After 7 years, canopy openness in gap centers had decreased to levels that did not differ from levels in forest canopy. Seedling height and maximum root depth were greatest in gap centers, where light was initially greater but seedling growth rates declined over time. Soil moisture was greater in pits, where establishment and survival were very low. Roots of some seedlings reached from mound surfaces to depths and moisture levels comparable to those of adjacent pits, which might facilitate survival in both floods and droughts. Quercus michauxii can persist on elevated sites in aging gaps, and positive feedback in sites favorable for recruitment can enhance seedling growth; ascent into the canopy will likely require additional canopy-opening events.
Improving growth and yield estimates with a process model derived growth index
Authors: Henning Jason G , Burk Thomas E
Published: June 2004

Forest managers have long made use of the regular and predictable nature of tree growth by using empirical growth and yield models to update forest inventories. Updated inventories support better decision making without requiring on the ground reassessment of the forest resource. Growth and yield model predictions can suffer from inaccuracies due to the influence of climate and environmental variability on the growth of trees. Researchers have been attempting to assess and predict the effect of this variation by developing mechanistic process models that often do not generate outputs applicable to inventory update. Here we create a growth index dependent on process model outputs to improve growth and yield estimates. Estimate accuracy was modestly improved over the basic growth and yield estimates and was comparable to previous efforts to account for environmental variability in growth and yield estimates. Using a process model we are nominally considering the entire environment, and by adjusting the growth and yield estimates external to both model types we have avoided difficulties involved with refitting or recreating either model. These are key differences from previous efforts to include environmental variability in growth and yield estimates.
Preventive and Therapeutic Effects of Acupuncture on Bone Mass in Osteopenic Ovariectomized Rats
Authors: Zhang Wenping , Kanehara Masayuki , Ishida Torao , Guo Yi , Wang Xiuyun , Li Guilan , Zhang Bingli , Kondo Hiroyo , Tachi Saori
Published: June 2004

This study was designed to (1) test the preventive and therapeutic effects of acupuncture on osteopenia in ovariectomized (OVX) rats, and (2) assess whether treatment of different acupuncture points causes different effects on tibiae, femora or lumbar spines. Thirty-five female Sprague-Dawley rats were divided into four groups: Sham (sham-operated, non-acupuncture); Model (OVX, non-acupuncture); Acp-A [OVX, bilateral needling of points Tsu-San-Li (ST-36) and San-Yin- Chiao (SP-6)]; and Acp-B (OVX, bilateral needling of P'i-Shu (Bl-20) and Shen Shu (Bl-23)). Operations were performed at 8 weeks of age, 1 week later the study was started and continued for 16 weeks. Ovariectomy resulted in decreased bone mineral density (BMD) compared to the sham group over time, and Acp-A tended to have higher BMD than the other OVX groups, especially for tibiae. In addition, the bone ash weight of the Acp groups tended to be heavier than the model group. Deoxypyridinoline, the urinary marker of bone resorption, also appeared to be decreased in both acupuncture groups. Similarly, microarchitecture and bone morphometry of lumbar vertebrae and tibiae, such as bone volume, trabecular thickness, trabecular number, mineralizing surface, bone formation rate, mineral apposition rate, number of nodes and number of node-terminus struts, also showed the same improvement in the acupuncture groups as compared to the model control group. Our findings showed that acupuncture may prevent the development of osteopenia in rats induced by ovariectomy. Needling of Tsu-San-Li (ST-36) and San-Yin- Chiao (SP-6) seems more effective than needling of P'i-Shu (Bl-20) and Shen Shu (Bl-23) in bone anabolic regulation.
EFFECTIVE ADMISSION CONTROL FOR POWER-CONTROLLED DS-CDMA SYSTEMS
Authors: SHIN SEUNG HOON , KWAK KYUNG SUP
Published: June 2004

Effective call admission control (CAC) is one of the most important techniques to provide the desired quality of service (QoS) in wireless networks. This paper investigates the call admission control problem for the power-controlled CDMA systems. With a macroscopic description for the power control problem, the call admission control for the power-constrained system is analyzed and an admissibility condition is derived. Based on the derived condition, we propose two CAC algorithms. One is an interactive method that provides the optimum performance, but requires some information exchange between base stations. The other can be implemented in a distributed manner and provide a reasonable performance. Through simulations, we show that the proposed algorithms provide an improved performance.
MULTI-USER DETECTION TO ENHANCE THE CAPACITY OF W-CDMA BASED ON THE CONJUGATE GRADIENT METHOD
Authors: ARAI YOSHIKAZU , IGARASHI KIYOMI , FUKASAWA ATSUSHI , TAKIZAWA YUMI
Published: June 2004

Multiple users communicate with individually-assigned codes on a single radio carrier frequency in a DS-CDMA system. Mutual interference among codes limits the capacity of the system. Conventional detectors of receivers are designed for a single-user neglecting the mutual interference. Multi-user detection is expected to enhance the capacity by removing the interference factors.

In this paper, a new scheme is proposed corresponding to solving a huge matrix equation under multiple access interference (MAI) environments. This scheme is obtained by the mathematical approach to solve a huge matrix equation. The modeling of multi-user detection is shown, and the algorithm is given based on mathematical approach: the Conjugate Gradient Method (CGM). The characteristics of the proposed scheme are evaluated with comparison to the conventional single-user detector. The proposed scheme has been shown to be three times in capacity against single user detection with reduced complexity comparing conventional technologies based on serial and parallel configurations.
A CHANNEL ASSIGNMENT PROBLEM IN MULTIHOP WIRELESS NETWORKS AND GRAPH THEORY
Authors: TAMURA HIROSHI , WATANABE KAORU , SENGOKU MASAKAZU , SHINODA SHOJI
Published: June 2004

Multihop wireless networks consist of mobile terminals with personal communication devices. Each terminal can receive a message and then send it to another terminal. In these networks, it is important to assign channels for communications to each terminal efficiently. There are some studies on this assignment problem using a conventional edge coloring in graph theory. In this paper, we propose a new edge coloring problem in graph and network theory on this assignment problem and we discuss the computational complexity of the problem. This edge coloring problem takes the degree of interference into consideration. Therefore, we can reuse the channels more efficiently compared with the conventional method.
DIMINISHING CAPACITY REQUIREMENT FOR MOBILITY DATABASE IN WIRELESS ATM
Authors: SUE KUEN-LIANG , LO CHI-CHUN
Published: June 2004

In wireless ATM, Visitor Location Register (VLR) is the database that supports mobility management. In case the number of roaming users exceeds the VLR supports, the arriving users cannot receive any service. To solve the problem, the Random Replacement (RR) policy randomly selects a victim record in VLR to be replaced with the record of the arriving user. The quality of services for the victim user will certainly drop. Therefore, the proportion of affected users is not allowed to exceed a tolerable threshold. Apparently, VLR size is the key factor of the threshold. The cost for maintaining a VLR increases significantly as its size grows. So, how to utilize the capacity efficiently is an important issue in VLR planning. We propose a Second Chance Replacement (SCR) policy to reduce the requirements for VLR capacity. As compared with the RR policy, the discrete-event simulation results show that the SCR policy can save 2.5% to 28% VLR size under various QoS thresholds.
FORMALIZATION OF MULTI-LEVEL GAMES
Authors: HAUSKEN KJELL , CRESSMAN ROSS
Published: June 2004

The article presents multilevel game theory, as a generalization of conventional single-level game theory as it has developed since von Neumann and Morgenstern (1944). We define a multilevel game structure, multilevel games, payoffs and distribution rules, upward feasible strategies and the solution concept multilevel Nash equilibrium (MNE) in such games. A MNE must be, for each player, a best reply against itself with respect to alternative strategies that may have other players deviate as well, in contrast to the NE for conventional games where simultaneous deviations by more than one player are not considered. Although every pure or mixed MNE must give the same outcome as a NE of the extensive form representation, a NE is not necessarily a MNE. It is shown that a MNE need not exist in pure or mixed strategies and, if it does, it may not be unique. In the former case, the multilevel structure is considered unmaintainable.
TECHNICAL NOTE: NONTRANSFERABLE INDIVIDUAL PAYOFFS IN COOPERATIVE STOCHASTIC DIFFERENTIAL GAMES
Authors: YEUNG DAVID W. K.
Published: June 2004

This note develops a mechanism for the derivation of individual player's payoff functions in cooperative stochastic differential games with nontransferable payoffs. An illustrative example is provided.
ELECTRON AND HOLE EFFECTIVE g FACTORS IN InAs/GaSb QUANTUM WELLS
Authors: ZAKHAROVA A. , YEN S. T. , CHAO K. A.
Published: June 2004

We investigate the Landau level structures and the electron and hole effective g factors in InAs / GaSb quantum wells under electric and quantizing magnetic fields perpendicular to interfaces. In these structures, the lowest electron level in InAs can be below the highest heavy-hole level in GaSb at zero magnetic field B. Thus the electron and hole levels anticross with the increasing magnetic field and the strong dependence of the Landau level structures as well as g factors on B is obtained. We have found that the voltage across the structure and the lattice-mismatched strain also produce the essential changes in the Landau level structures as well as the electron and hole g factors.
STARK SPECTROSCOPY OF Ge/Si(001) SELF-ASSEMBLED QUANTUM DOTS
Authors: YAKIMOV A. I. , DVURECHENSKII A. V. , NIKIFOROV A. I. , ULYANOV V. V. , MILEKHIN A. G. , SCHULZE S. , ZAHN D. R. T.
Published: June 2004

Stark spectroscopy was employed to study interband optical transitions in an array of Ge / Si self-assembled quantum dots. The mean diameter and height of the Ge nanoclusters are about 6 nm and 4 nm, respectively. Under an applied electric field splitting of the exciton ground state is observed, implying that the dots possess two permanent dipole moments of opposite sign. We argue that the two possible orientations of the electron-hole dipole in each Ge dot are the result of the spatial separation of electrons which can be excited in Si as well as on top and below the Ge nanocluster. The separation of electron and hole is determined to be (5.1±0.2) nm for the top (apex) electron, and (0.8±0.3) nm for the bottom (base) electron, yielding a distance between the electrons of (5.9±0.5) nm, which is consistent with the staggered band line-up inherent to type-II quantum dots.
ANTILOCALIZATION IN GATED 2D QUANTUM WELL STRUCTURES WITH COMPOSITION GRADIENT
Authors: MINKOV G. M. , GERMANENKO A. V. , RUT O. E. , SHERSTOBITOV A. A. , ZVONKOV B. N.
Published: June 2004

Low-field magnetoconductivity caused by the quantum interference is studied in the gated 2D quantum well structures with the composition gradient. It is shown that the Dresselhaus mechanism describes well an antilocalization minimum on the conductivity-magnetic field curve.
RELAXATION OSCILLATIONS AND DYNAMICAL PROPERTIES OF A BISTABLE QUANTUM HALL SYSTEM
Authors: KALUGIN N. G. , SAĞOL B. E. , STELLMACH C. , BUß A. , HIRSCH A. , NACHTWEI G. , HEIN G.
Published: June 2004

We present a simple relaxation oscillator based on a quantum Hall device with Corbino geometry near the breakdown of the quantum Hall effect. The amplitude of the observed relaxation oscillations is found many times bigger than one can expect from the hysteresis of the quantum Hall effect breakdown, measured at constant currents. This result is explained by a dynamical suppression of hopping contribution to the conductivity σxx, and corresponding dynamical reduction of localization length ξ.
NONEQUILIBRIUM EFFECTS AND MANY-PARTICLE INTERACTION IN TUNNELING SPECTROSCOPY OF IMPURITY d-ORBITAL
Authors: ARSEYEV P. I. , MASLOVA N. S. , PANOV V. I. , SAVINOV S. V. , VAN HAESENDONCK CHRIS
Published: June 2004

We report the direct observation by low temperature scanning tunneling microscopy and scanning tunneling spectroscopy of the d-orbital of a Mn p-type impurity appearing on a cleaved InAs (110) surface. STM images reveal remarkable cross-like protrusions and round depressions around isolated impurity atom on the surface at opposite polarity of tunneling bias voltage. By means of diagram technique for nonequilibrium processes we show that the crucial interplay between nonequilibrium charging effects and many-particle interaction leading to Coulomb singularities provides a consistent description of the experimental results.
HALL CONDUCTIVITY AND OPTICS OF A TWO-DIMENSIONAL ELECTRON GAS AT THE LACK OF INVERSION SYMMETRY
Authors: Ya. DEMIKHOVSKII V. , PEROV A. A.
Published: June 2004

Quantum states of 2D electrons are studied in a periodic potential without the inversion center in the presence of a magnetic field. It is shown that the energy spectrum in magnetic subbands is not symmetric with respect to the center of magnetic Brillouin zone: E(k)≠E(-k). Singularities (phase branching points) of the electron wave function, which determine the quantization law of Hall conductivity σxy, are studied in the k space. It is found that the number of singular points and the correspondent topological invariants which determine Hall conductivity of occupied subbands change drastically with respect to variation of periodic potential parameters. It is predicted that in such system the photogalvanic effect can be observed under the action of external electromagnetic field.
ELECTRICAL SYNAPSES IN THE MAMMALIAN BRAIN
Authors: Connors Barry W. , Long Michael A.
Published: June 2004

▪ Abstract  Many neurons in the mammalian central nervous system communicate through electrical synapses, defined here as gap junction–mediated connections. Electrical synapses are reciprocal pathways for ionic current and small organic molecules. They are often strong enough to mediate close synchronization of subthreshold and spiking activity among clusters of neurons. The most thoroughly studied electrical synapses occur between excitatory projection neurons of the inferior olivary nucleus and between inhibitory interneurons of the neocortex, hippocampus, and thalamus. All these synapses require the gap junction protein connexin36 (Cx36) for robust electrical coupling. Cx36 appears to interconnect neurons exclusively, and it is expressed widely along the mammalian neuraxis, implying that there are undiscovered electrical synapses throughout the central nervous system. Some central neurons may be electrically coupled by other connexin types or by pannexins, a newly described family of gap junction proteins. Electrical synapses are a ubiquitous yet underappreciated feature of neural circuits in the mammalian brain.
CONTROL OF CENTRAL SYNAPTIC SPECIFICITY IN INSECT SENSORY NEURONS
Authors: Blagburn Jonathan M. , Bacon Jonathan P.
Published: June 2004

▪ Abstract  Synaptic specificity is the culmination of several processes, beginning with the establishment of neuronal subtype identity, followed by navigation of the axon to the correct subdivision of neuropil, and finally, the cell-cell recognition of appropriate synaptic partners. In this review we summarize the work on sensory neurons in crickets, cockroaches, moths, and fruit flies that establishes some of the principles and molecular mechanisms involved in the control of synaptic specificity. The identity of a sensory neuron is controlled by combinatorial expression of transcription factors, the products of patterning and proneural genes. In the nervous system, sensory axon projections are anatomically segregated according to modality, stimulus quality, and cell-body position. A variety of cell-surface and intracellular signaling molecules are used to achieve this. Synaptic target recognition is also controlled by transcription factors such as Engrailed and may be, in part, mediated by cadherin-like molecules.
NEURONAL CIRCUITS OF THE NEOCORTEX
Authors: Douglas Rodney J. , Martin Kevan A.C.
Published: June 2004

▪ Abstract  We explore the extent to which neocortical circuits generalize, i.e., to what extent can neocortical neurons and the circuits they form be considered as canonical? We find that, as has long been suspected by cortical neuroanatomists, the same basic laminar and tangential organization of the excitatory neurons of the neocortex is evident wherever it has been sought. Similarly, the inhibitory neurons show characteristic morphology and patterns of connections throughout the neocortex. We offer a simple model of cortical processing that is consistent with the major features of cortical circuits: The superficial layer neurons within local patches of cortex, and within areas, cooperate to explore all possible interpretations of different cortical input and cooperatively select an interpretation consistent with their various cortical and subcortical inputs.
THE AMYGDALA MODULATES THE CONSOLIDATION OF MEMORIES OF EMOTIONALLY AROUSING EXPERIENCES
Authors: McGaugh James L.
Published: June 2004

▪ Abstract  Converging findings of animal and human studies provide compelling evidence that the amygdala is critically involved in enabling us to acquire and retain lasting memories of emotional experiences. This review focuses primarily on the findings of research investigating the role of the amygdala in modulating the consolidation of long-term memories. Considerable evidence from animal studies investigating the effects of posttraining systemic or intra-amygdala infusions of hormones and drugs, as well as selective lesions of specific amygdala nuclei, indicates that (a) the amygdala mediates the memory-modulating effects of adrenal stress hormones and several classes of neurotransmitters; (b) the effects are selectively mediated by the basolateral complex of the amygdala (BLA); (c) the influences involve interactions of several neuromodulatory systems within the BLA that converge in influencing noradrenergic and muscarinic cholinergic activation; (d) the BLA modulates memory consolidation via efferents to other brain regions, including the caudate nucleus, nucleus accumbens, and cortex; and (e) the BLA modulates the consolidation of memory of many different kinds of information. The findings of human brain imaging studies are consistent with those of animal studies in suggesting that activation of the amygdala influences the consolidation of long-term memory; the degree of activation of the amygdala by emotional arousal during encoding of emotionally arousing material (either pleasant or unpleasant) correlates highly with subsequent recall. The activation of neuromodulatory systems affecting the BLA and its projections to other brain regions involved in processing different kinds of information plays a key role in enabling emotionally significant experiences to be well remembered.
THE HUMAN VISUAL CORTEX
Authors: Grill-Spector Kalanit , Malach Rafael
Published: June 2004

▪ Abstract  The discovery and analysis of cortical visual areas is a major accomplishment of visual neuroscience. In the past decade the use of noninvasive functional imaging, particularly functional magnetic resonance imaging (fMRI), has dramatically increased our detailed knowledge of the functional organization of the human visual cortex and its relation to visual perception. The fMRI method offers a major advantage over other techniques applied in neuroscience by providing a large-scale neuroanatomical perspective that stems from its ability to image the entire brain essentially at once. This bird's eye view has the potential to reveal large-scale principles within the very complex plethora of visual areas. Thus, it could arrange the entire constellation of human visual areas in a unified functional organizational framework. Here we review recent findings and methods employed to uncover the functional properties of the human visual cortex focusing on two themes: functional specialization and hierarchical processing.
THE MIRROR-NEURON SYSTEM
Authors: Rizzolatti Giacomo , Craighero Laila
Published: June 2004

▪ Abstract  A category of stimuli of great importance for primates, humans in particular, is that formed by actions done by other individuals. If we want to survive, we must understand the actions of others. Furthermore, without action understanding, social organization is impossible. In the case of humans, there is another faculty that depends on the observation of others' actions: imitation learning. Unlike most species, we are able to learn by imitation, and this faculty is at the basis of human culture. In this review we present data on a neurophysiological mechanism—the mirror-neuron mechanism—that appears to play a fundamental role in both action understanding and imitation. We describe first the functional properties of mirror neurons in monkeys. We review next the characteristics of the mirror-neuron system in humans. We stress, in particular, those properties specific to the human mirror-neuron system that might explain the human capacity to learn by imitation. We conclude by discussing the relationship between the mirror-neuron system and language.
PLASTICITY OF THE SPINAL NEURAL CIRCUITRY AFTER INJURY
Authors: Edgerton V. Reggie , Tillakaratne Niranjala J.K. , Bigbee Allison J. , de Leon Ray D. , Roy Roland R.
Published: June 2004

▪ Abstract  Motor function is severely disrupted following spinal cord injury (SCI). The spinal circuitry, however, exhibits a great degree of automaticity and plasticity after an injury. Automaticity implies that the spinal circuits have some capacity to perform complex motor tasks following the disruption of supraspinal input, and evidence for plasticity suggests that biochemical changes at the cellular level in the spinal cord can be induced in an activity-dependent manner that correlates with sensorimotor recovery. These characteristics should be strongly considered as advantageous in developing therapeutic strategies to assist in the recovery of locomotor function following SCI. Rehabilitative efforts combining locomotor training pharmacological means and/or spinal cord electrical stimulation paradigms will most likely result in more effective methods of recovery than using only one intervention.
UBIQUITIN-DEPENDENT REGULATION OF THE SYNAPSE
Authors: DiAntonio Aaron , Hicke Linda
Published: June 2004

▪ Abstract  Posttranslational modification of cellular proteins by the covalent attachment of ubiquitin regulates protein stability, activity, and localization. Ubiquitination is rapid and reversible and is a potent mechanism for the spatial and temporal control of protein activity. By sculpting the molecular composition of the synapse, this versatile posttranslational modification shapes the pattern, activity, and plasticity of synaptic connections. Synaptic processes regulated by ubiquitination, as well as ubiquitination enzymes and their targets at the synapse, are being identified by genetic, biochemical, and electrophysiological analyses. This work provides tantalizing hints that neuronal activity collaborates with ubiquitination pathways to regulate the structure and function of synapses.
E PLURIBUS UNUM, EX UNO PLURA: Quantitative and Single-Gene Perspectives on the Study of Behavior
Authors: Greenspan Ralph J.
Published: June 2004

▪ Abstract  Genetic studies of behavior have traditionally come in two flavors: quantitative genetic studies of natural variants and single-gene studies of induced mutants. Each employed different techniques and methods of analysis toward the common, ultimate goal of understanding how genes influence behavior. With the advent of new genomic technologies, and also the realization that mechanisms underlying behavior involve a considerable degree of complex gene interaction, the traditionally separate strands of behavior genetics are merging into a single, synthetic strategy.
THE NOGO SIGNALING PATHWAY FOR REGENERATION BLOCK
Authors: He Zhigang , Koprivica Vuk
Published: June 2004

▪ Abstract  A hostile environment and decreased regenerative capacity may contribute to the failure of axon regeneration in the adult central nervous system. Recent studies leading to the identification of several myelin-associated inhibitors and their signaling molecules provide opportunitities to assess the contribution of these inhibitory molecules in restricting axon regeneration. These findings may ultimately allow for the development of strategies to alleviate the inhibitory effects of such molecules in an effort to encourage axon regeneration after spinal cord and brain injury.
Regulation of CCK-induced amylase release by PKC-δ in rat pancreatic acinar cells
Authors: Li Chenwei , Chen Xuequn , Williams John A.
Published: June 2004

PKC is known to be activated by pancreatic secretagogues such as CCK and carbachol and to participate along with calcium in amylase release. Four PKC isoforms, α, δ, ε, and ζ, have been identified in acinar cells, but which isoforms participate in amylase release are unknown. To identify the responsible isoforms, we used translocation assays, chemical inhibitors, and overexpression of individual isoforms and their dominant-negative variants by means of adenoviral vectors. CCK stimulation caused translocation of PKC-α, -δ, and -ε, but not -ζ from soluble to membrane fraction. CCK-induced amylase release was inhibited ∼30% by GF109203X, a broad spectrum PKC inhibitor, and by rottlerin, a PKC-δ inhibitor, but not by Gö6976, a PKC-α inhibitor, at concentrations from 1 to 5 μM. Neither overexpression of wild-type or dominant-negative PKC-α affected CCK-induced amylase release. Overexpression of PKC-δ and -ε enhanced amylase release, whereas only dominant-negative PKC-δ inhibited amylase release by 25%. PKC-δ overexpression increased amylase release at all concentrations of CCK, but dominant-negative PKC-δ only inhibited the maximal concentration; both similarly affected carbachol and JMV-180-induced amylase release. Overexpression of both PKC-δ and its dominant-negative variant affected the late but not the early phase of amylase release. GF109203X totally blocked the enhancement of amylase release by PKC-δ but had no further effect in the presence of dominant-negative PKC-δ. These results indicate that PKC-δ is the PKC isoform involved with amylase secretion.
Rat intestinal ceramidase: purification, properties, and physiological relevance
Authors: Olsson Maria , Duan Rui-Dong , Ohlsson Lena , Nilsson Åke
Published: June 2004

Neutral ceramidase activity has previously been identified in the intestinal mucosa and gut lumen and postulated to be important in the digestion of sphingolipids. It is found throughout the intestine but has never been fully characterized. We have purified rat intestinal neutral ceramidase from an eluate obtained by perfusing the intestinal lumen with 0.9% NaCl and 3 mM sodium taurodeoxycholate. Using a combination of acetone precipitation and ion-exchange, hydrophobic-interaction, and gel chromatographies, we obtained a homogenous enzyme protein with a molecular mass of ∼116 kDa. The enzyme acts on both [14C]octanoyl- and [14C]palmitoyl-sphingosine in the presence of glycocholic and taurocholic acid and the bile salt analog 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate but is inhibited by 2 mM or more of other bile salts. It is a glycosylated protein stable to trypsin and chymotrypsin exposure, is not influenced by Ca2+, Mg2+, or Mn2+, and is inhibited by Zn2+and Cu2+. Mass fragmentographic analysis identified 12 fragments covering 17.5% of the sequence for neutral/alkaline ceramidase 2 purified (Mitsutake S, Tani M, Okino N, Mori K, Ichinose S, Omori A, Iida H, Nakamura T, and Ito M. J Biol Chem 276: 26249–262459, 2001) from rat kidney and located in apical membrane of renal tubular cells. Intestinal and kidney ceramidases also have similar molecular mass and ion dependence. Intestinal ceramidase thus is a neutral ceramidase 2 released by bile salts and resistant to pancreatic proteases. It is well suited to metabolize ceramide formed from dietary and brush border sphingolipids to generate other bioactive sphingolipid messengers.
Characterization of the 5′-regulatory region of the human thiamin transporter SLC19A3: in vitro and in vivo studies
Authors: Nabokina Svetlana M. , Said Hamid M.
Published: June 2004

Transcriptional regulation of expression of the human thiamin transporter-2 (the product of the SLC19A3 gene) is unknown. In this study, we cloned the 5′-regulatory region of the human SLC19A3 gene (2,016 bp), identified the minimal promoter region required for basal activity, demonstrated a critical role for specific cis-regulatory elements in determining the promoter activity, and confirmed activity and physiological relevance of the cloned SLC19A3 promoter in vivo. With the use of transiently transfected human intestinal epithelial Caco-2 cells and 5′-deletion analysis, the minimal promoter region required for basal activity of the SLC19A3 promoter was found to be encoded in a sequence between −77 and +59 by using the start of transcription initiation as position 1. This minimal region was found to contain a number of putative cis-regulatory elements, with a critical role for a stimulating protein-1 (SP1)/GC-box binding site (at position −48/−45 bp) established by means of mutational analysis. With the use of EMSA and supershift assays, the binding of SP1 and SP3 to the minimal promoter region was also demonstrated. In transiently transfected Drosophila SL2 cells, both SP1 and SP3 transactivated the SLC19A3 minimal promoter in a dose-dependent manner and in combination demonstrated an additive stimulatory effect. Functionality of the full-length SLC19A3 promoter was confirmed in vivo in transgenic mice expressing the promoter-luciferase reporter gene. These studies report the first characterization of the SLC19A3 promoter in vitro and in vivo and demonstrate the importance of an SP1 cis-regulatory element in regulating promoter activity of this important human gene.
Attenuation of fatty acid-induced apoptosis by low-dose alcohol in neonatal rat cardiomyocytes
Authors: Sparagna Genevieve C. , Jones Chad E. , Hickson-Bick Diane L. M.
Published: June 2004

Moderate alcohol consumption has been shown to reduce the morbidity and mortality from coronary heart disease. Ethanol elicits its protective effects via mechanisms that include activation of protein kinases linked to growth and survival. Our results in isolated neonatal rat cardiomyocytes demonstrate that repeated short-term, low-dose exposure to ethanol is sufficient to activate the growth and/or survival pathways that involve PKC-ε, Akt, and AMP-activated kinase. In addition, we are able to induce apoptosis in these cardiomyocytes using the saturated fatty acid palmitate. Pretreatment with multiple low-dose ethanol exposures attenuates the apoptotic response to palmitate. This protection is manifested by a reduction in caspase-3-like activity, decreased mitochondrial loss of cytochrome c, and decreased loss of the mitochondrial lipid cardiolipin. We previously reported that incubation of cardiomyocytes with palmitate results in decreased production of reactive oxygen species compared with cells incubated with the nonapoptotic fatty acid oleate. In the present study, we observed an increase in the production of superoxide and the rates of fatty acid oxidation in cardiomyocytes pretreated with ethanol and then exposed to fatty acids. The level of superoxide production in palmitate-treated cells returns to the levels observed in oleate-treated cells after ethanol exposure. Taken together with our observed increase in AMP-activated kinase activity, we propose that ethanol pretreatments stimulate oxidative metabolism and electron transport within cardiomyocytes. We postulate that stimulation of palmitate metabolism may protect cardiomyocytes by preventing accumulation of unsaturated precursor molecules of cardiolipin synthesis. Maintaining cardiolipin levels may be sufficient to prevent the mitochondrial loss of cytochrome c and the downstream activation of caspases.