bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in multiple brain regions underlie species differences in a complex, congenital behavior
Authors: Balaban Evan
Published: July 2002

The evolutionary brain modifications that produce any complex, congenital behavioral difference between two species have never been identified. Evolutionary processes may (i) alter a single, “higher” brain area that generates and/or coordinates the diverse motor components of a complex act; (ii) separately change independent, “lower” brain areas that modulate the fine motor control of the individual components; or (iii) modify both types of areas. This study explores the brain localization of a species difference in one such behavior, the crowing of chickens (Gallus gallus domesticus) and Japanese quail (Coturnix coturnix japonica). Two major subcomponents of the behavioral difference can be independently transferred with interspecies transplantation of separate brain regions, despite the fact that these components, sound and patterned head movement, occur together in a highly integrated fashion. To our knowledge, this is the first experimental demonstration that species differences in a complex behavior are built up from separate changes to distinct cell groups in different parts of the brain and that these cell groups have independent effects on individual behavioral components.
COOH-terminal sequence of the cellular prion protein directs subcellular trafficking and controls conversion into the scrapie isoform
Authors: Kaneko Kiyotoshi , Vey Martin , Scott Michael , Pilkuhn Susanne , Cohen Fred E. , Prusiner Stanley B.
Published: July 2002

Efficient formation of scrapie isoform of prion protein (PrPSc) requires targeting PrPScby glycophosphatidyl inositol (GPI) anchors to caveolae-like domains (CLDs). Redirecting the cellular isoform of prion protein (PrPC) to clathrin-coated pits by creating chimeric PrP molecules with four different COOH-terminal transmembrane domains prevented the formation of PrPSc. To determine if these COOH-terminal transmembrane segments prevented PrPCfrom refolding into PrPScby altering the structure of the polypeptide, we fused the 28-aa COOH termini from the Qa protein. Two COOH-terminal Qa segments differing by a single residue direct the transmembrane protein to clathrin-coated pits or the GPI form to CLDs; PrPScwas formed from GPI-anchored PrPCbut not from transmembrane PrPC. Our findings argue that PrPScformation is restricted to a specific subcellular compartment and as such, it is likely to involve auxiliary macromolecules found within CLDs.
Identification of a novel pathway important for proliferation and differentiation of primary erythroid progenitors
Authors: Klingmüller Ursula , Wu Hong , Hsiao Jonathan G. , Toker Alex , Duckworth Brian C. , Cantley Lewis C. , Lodish Harvey F.
Published: July 2002

Homodimerization of the erythropoietin (EPO) receptor (EPO-R) in response to EPO binding transiently activates the receptor-associated protein tyrosine kinase JAK2. Tyrosine phosphorylation of the EPO-R creates “docking sites” for SH2 domain(s) in signaling molecules such as the protein tyrosine phosphatases SH-PTP1 and SH-PTP2, phosphoinositide 3-kinase (PI3 kinase), and STAT5. However, little is known about the specific intracellular signals essential for proliferation and differentiation of erythroid progenitors. Here we show that an EPO-R containing only one cytosolic (phospho)tyrosine residue, Y479, induces a signal transduction pathway sufficient for proliferation and differentiation of fetal liver progenitors of erythroid colony-forming units from EPO-R
−/−
mice as well as for proliferation of cultured hematopoietic cells. This cascade involves sequential EPO-induced recruitment of PI3 kinase to the EPO-R and activation of mitogen-activated protein kinase activity, independent of the Shc/Grb2-adapter pathway and of STAT5. Protein kinase Cɛ may be one of the mediators connecting PI3 kinase with the mitogen-activated protein kinase signaling cascade. Our results identify a signaling cascade important
in vivo
for erythroid cell proliferation and differentiation.
Folding of the conserved domain but not of flanking regions in the integrin β2subunit requires association with the α subunit
Authors: Huang Chichi , Lu Chafen , Springer Timothy A.
Published: July 2002

We have used immunoprecipitation with mAbs to probe folding during biosynthesis of the β2integrin subunit of lymphocyte function-associated antigen 1 (LFA-1; CD11a/CD18) before and after association with the αLsubunit. An evolutionarily conserved region is present in the β2subunit between amino acid residues 102 and 344. mAbs to one subregion before the conserved region, and two subregions after the conserved domain, immunoprecipitated both the unassociated β′2precursor and mature αL/β2complex, suggesting portions of these subregions are folded before association with αL. An activating mAb to the C-terminal cysteine-rich region, KIM127, preferentially bound to the unassociated β subunit, suggesting that it may bind to an epitope that is in an αβ interface in unactivated LFA-1. By contrast, mAbs to five different epitopes in the conserved region did not react with unassociated β′2precursor, suggesting that this region folds after αLassociation and is intimately associated with the αLsubunit in the αL/β2complex. mAbs to two different epitopes that involve the border between the conserved region and the C-terminal segment, were fully or partially reactive with the β′2precursor, suggesting that this region is partially folded before association with αL. The findings suggest that the conserved region is a distinct folding and hence structural unit, and is intimately associated with the α subunit.
Not all (possibly) “random” sequences are created equal
Authors: Pincus Steve , Kalman Rudolf E.
Published: July 2002

The need to assess the randomness of a single sequence, especially
a finite sequence, is ubiquitous, yet is unaddressed by axiomatic
probability theory. Here, we assess randomness via approximate entropy
(ApEn), a computable measure of sequential irregularity, applicable to
single sequences of both (even very short) finite and infinite length.
We indicate the novelty and facility of the multidimensional viewpoint
taken by ApEn, in contrast to classical measures. Furthermore and
notably, for finite length, finite state sequences, one can identify
maximally irregular sequences, and then apply ApEn to quantify the
extent to which given sequences differ from maximal irregularity, via a
set of deficit (def
m
) functions. The utility of these
def
m
functions which we show allows one to considerably
refine the notions of probabilistic independence and normality, is
featured in several studies, including (
i
) digits of e,
π, √2, and √3, both in base 2 and in base 10, and
(
ii
) sequences given by fractional parts of multiples of
irrationals. We prove companion analytic results, which also feature in
a discussion of the role and validity of the almost sure properties
from axiomatic probability theory insofar as they apply to specified
sequences and sets of sequences (in the physical world). We conclude by
relating the present results and perspective to both previous and
subsequent studies.
Twenty proteins containing a C-terminal SOCS box form five structural classes
Authors: Hilton Douglas J. , Richardson Rachael T. , Alexander Warren S. , Viney Elizabeth M. , Willson Tracy A. , Sprigg Naomi S. , Starr Robyn , Nicholson Sandra E. , Metcalf Donald , Nicola Nicos A.
Published: July 2002

The four members of the recently identified suppressor of cytokines signaling family (SOCS-1, SOCS-2, SOCS-3, and CIS, where CIS is cytokine-inducible SH2-containing protein) appear, by various means, to negatively regulate cytokine signal transduction. Structurally, the SOCS proteins are composed of an N-terminal region of variable length and amino acid composition, a central SH2 domain, and a previously unrecognized C-terminal motif that we have called the SOCS box. By using the SOCS box amino acid sequence consensus, we have searched DNA databases and have identified a further 16 proteins that contain this motif. These proteins fall into five classes based on the protein motifs found N-terminal of the SOCS box. In addition to four new SOCS proteins (SOCS-4 to SOCS-7) containing an SH2 domain and a SOCS box, we describe three new families of proteins that contain either WD-40 repeats (WSB-1 and -2), SPRY domains (SSB-1 to -3) or ankyrin repeats (ASB-1 to -3) N-terminal of the SOCS box. In addition, we show that a class of small GTPases also contains a SOCS box. The expression of representative members of each class of proteins differs markedly, as does the regulation of expression by cytokines. The function of the WSB, SSB, and ASB protein families remains to be determined.
Extracellular enveloped vaccinia virus is resistant to complement because of incorporation of host complement control proteins into its envelope
Authors: Vanderplasschen Alain , Mathew Elizabeth , Hollinshead Michael , Sim Robert B. , Smith Geoffrey L.
Published: July 2002

Vaccinia virus (VV) produces two antigenically and structurally distinct infectious virions, intracellular mature virus (IMV) and extracellular enveloped virus (EEV). Here we have investigated the resistance of EEV and IMV to neutralization by complement in the absence of immune antibodies. When EEV is challenged with complement from the same species as the cells used to grow the virus, EEV is resistant to neutralization by complement, whereas IMV is not. EEV resistance was not a result of EEV protein B5R, despite its similarity to proteins of the regulators of complement activation (RCA) family, or to any of the other EEV proteins tested (A34R, A36R, and A56R gene products). EEV was sensitive to complement when the virus was grown in one species and challenged with complement from a different species, suggesting that complement resistance might be mediated by host RCA incorporated into the EEV outer envelope. This hypothesis was confirmed by several observations: (
i
) immunoblot analysis revealed that cellular membrane proteins CD46, CD55, CD59, CD71, CD81, and major histocompatibility complex class I antigen were detected in purified EEV but not IMV; (
ii
) immunoelectron microscopy revealed cellular RCA on the surface of EEV retained on the cell surface; and (
iii
) EEV derived from rat cells expressing the human RCA CD55 or CD55 and CD59 were more resistant to human complement than EEV derived from control rat cells that expressed neither CD55 nor CD59. These data justify further analysis of the roles of these (and possible other) cellular proteins in EEV biology.
Estimating sequestered parasite population dynamics in cerebral malaria
Authors: Gravenor Michael B. , van Hensbroek Michael Boele , Kwiatkowski Dominic
Published: July 2002

Clinical investigation of malaria is hampered by the lack of a method for estimating the number of parasites that are sequestered in the tissues, for it is these parasites that are thought to be crucial to the pathogenesis of life-threatening complications such as cerebral malaria. We present a method of estimating this hidden population by using clinical observations of peripheral parasitemia combined with an age-structured mathematical model of the parasite erythrocyte cycle. Applying the model to data from 217 Gambian children undergoing treatment for cerebral malaria we conclude that although artemether clears parasitemia more rapidly than quinine, the clearance of sequestered parasites is similar for the two drugs. The estimated sequestered mass was found to be a more direct predictor of fatal outcome than clinically observed parasitemia. This method allows a sequential analysis of sequestered parasite population dynamics in children suffering from cerebral malaria, and the results offer a possible explanation for why artemether provides less advantage than might have been expected over quinine in reducing mortality despite its rapid effect on circulating parasites.
Dynamic characteristics and adaptability of mouse vestibulo-ocular and optokinetic response eye movements and the role of the flocculo-olivary system revealed by chemical lesions
Authors: Katoh Akira , Kitazawa Hiromasa , Itohara Shigeyoshi , Nagao Soichi
Published: July 2002

The dynamic characteristics of reflex eye movements were measured in two strains of chronically prepared mice by using an infrared television camera system. The horizontal vestibulo-ocular reflex (HVOR) and horizontal optokinetic response (HOKR) were induced by sinusoidal oscillations of a turntable, in darkness, by 10° (peak to peak) at 0.11–0.50 Hz and of a checked-pattern screen, in light, by 5–20°at 0.11–0.17 Hz, respectively. The gains and phases of the HVOR and HOKR of the C57BL/6 mice were nearly equivalent to those of rabbits and rats, whereas the 129/Sv mice exhibited very low gains in the HVOR and moderate phase lags in the HOKR, suggesting an inherent sensory-motor anomaly. Adaptability of the HOKR was examined in C57BL/6 mice by sustained screen oscillation. When the screen was oscillated by 10° at 0.17 Hz, which induced sufficient retinal slips, the gain of the HOKR increased by 0.08 in 1 h on average, whereas the stimuli that induced relatively small or no retinal slips affected the gain very little. Lesions of the flocculi induced by local applications of 0.1% ibotenic acid and lesions of the inferior olivary nuclei induced by i.p. injection of 3-acetylpyridine in C57BL/6 mice little affected the dynamic characteristics of the HVOR and HOKR, but abolished the adaptation of the HOKR. These results indicate that the olivo-floccular system plays an essential role in the adaptive control of the ocular reflex in mice, as suggested in other animal species. The data presented provide the basis for analyzing the reflex eye movements of genetically engineered mice.
Functional coupling between secretory phospholipase A2and cyclooxygenase-2 and its regulation by cytosolic group IV phospholipase A2
Authors: Balsinde Jesús , Balboa María A. , Dennis Edward A.
Published: July 2002

Secretory phospholipase A2(sPLA2) is the major effector involved in arachidonic acid (AA) mobilization and prostaglandin E2(PGE2) production during stimulation of P388D1macrophages with the inflammatory stimuli bacterial lipopolysaccharide and platelet-activating factor. We herein demonstrate that PGE2in stimulated P388D1cells is accounted for by the inducible cyclooxygenase (COX)-2. COX-1, though present, appears not to participate significantly in stimulus-induced PGE2production in P388D1macrophages. Reconstitution experiments utilizing exogenous recombinant sPLA2demonstrate that activation of the sPLA2at the plasma membrane is highly dependent on previous activation of the cytosolic phospholipase A2(cPLA2). Collectively these results demonstrate (i) that functional coupling exists between sPLA2and COX-2 in activated cells, (ii) the critical role that cPLA2plays in lipid mediator production, and (iii) that there is crosstalk between cPLA2and sPLA2in the cell.
Evolvability
Authors: Kirschner Marc , Gerhart John
Published: July 2002

Evolvability is an organism’s capacity to generate heritable phenotypic variation. Metazoan evolution is marked by great morphological and physiological diversification, although the core genetic, cell biological, and developmental processes are largely conserved. Metazoan diversification has entailed the evolution of various regulatory processes controlling the time, place, and conditions of use of the conserved core processes. These regulatory processes, and certain of the core processes, have special properties relevant to evolutionary change. The properties of versatile protein elements, weak linkage, compartmentation, redundancy, and exploratory behavior reduce the interdependence of components and confer robustness and flexibility on processes during embryonic development and in adult physiology. They also confer evolvability on the organism by reducing constraints on change and allowing the accumulation of nonlethal variation. Evolvability may have been generally selected in the course of selection for robust, flexible processes suitable for complex development and physiology and specifically selected in lineages undergoing repeated radiations.
NaN, a novel voltage-gated Na channel, is expressed preferentially in peripheral sensory neurons and down-regulated after axotomy
Authors: Dib-Hajj S. D. , Tyrrell L. , Black J. A. , Waxman S. G.
Published: July 2002

Although physiological and pharmacological evidence suggests the presence of multiple tetrodotoxin-resistant (TTX-R) Na channels in neurons of peripheral nervous system ganglia, only one, SNS/PN3, has been identified in these cells to date. We have identified and sequenced a novel Na channel α-subunit (NaN), predicted to be TTX-R and voltage-gated, that is expressed preferentially in sensory neurons within dorsal root ganglia (DRG) and trigeminal ganglia. The predicted amino acid sequence of NaN can be aligned with the predicted structure of known Na channel α-subunits; all relevant landmark sequences, including positively charged S4 and pore-lining SS1–SS2 segments, and the inactivation tripeptide IFM, are present at predicted positions. However, NaN exhibits only 42–53% similarity to other mammalian Na channels, including SNS/PN3, indicating that it is a novel channel, and suggesting that it may represent a third subfamily of Na channels. NaN transcript levels are reduced significantly 7 days post axotomy in DRG neurons, consistent with previous findings of a reduction in TTX-R Na currents. The preferential expression of NaN in DRG and trigeminal ganglia and the reduction of NaN mRNA levels in DRG after axonal injury suggest that NaN, together with SNS/PN3, may produce TTX-R currents in peripheral sensory neurons and may influence the generation of electrical activity in these cells.
Unusual proliferation arrest and transcriptional control properties of a newly discovered E2F family member, E2F-6
Authors: Gaubatz Stefan , Wood Jason G. , Livingston David M.
Published: July 2002

E2F transcription factors play an important role in the regulation of cell cycle progression. We report here the cloning and characterization of an additional member of this family, E2F-6. E2F-6 lacks pocket protein binding and transactivation domains, and it is a potent transcriptional repressor that contains a modular repression domain at its carboxyl terminus. Overproduction of E2F-6 had no specific effect on cell cycle progression in asynchronously growing Saos2 and NIH 3T3 cells, but it inhibited entry into S phase of NIH 3T3 cells stimulated to exit G
0
. Taken together, these data suggest that E2F-6 can regulate a subset of E2F-dependent genes whose products are required for entry into the cell cycle but not for normal cell cycle progression.
Direct immunogold labeling of aquaporin-4 in square arrays of astrocyte and ependymocyte plasma membranes in rat brain and spinal cord
Authors: Rash John E. , Yasumura Thomas , Hudson C. Sue , Agre Peter , Nielsen Søren
Published: July 2002

Aquaporin (AQP) water channels are abundant in the brain and spinal cord, where AQP1 and AQP4 are believed to play major roles in water metabolism and osmoregulation. Immunocytochemical analysis of the brain recently revealed that AQP4 has a highly polarized distribution, with marked expression in astrocyte end-feet that surround capillaries and form the glia limitans; however, the structural organization of AQP4 has remained unknown. In freeze-fracture replicas, astrocyte end-feet contain abundant square arrays of intramembrane particles that parallel the distribution of AQP4. To determine whether astrocyte and ependymocyte square arrays contain AQP4, we employed immunogold labeling of SDS-washed freeze-fracture replicas and stereoscopic confirmation of tissue binding. Antibodies to AQP4 directly labeled ≈33% of square arrays in astrocyte and ependymocyte plasma membranes in rat brain and spinal cord. Overall, 84% of labels were present beneath square arrays; 11% were beneath particle clusters that resembled square arrays that had been altered during fixation or cleaving; and 5% were beneath the much larger areas of glial plasma membrane that were devoid of square arrays. Based on this evidence that AQP4 is concentrated in glial square arrays, freeze-fracture methods may now provide biophysical insights regarding neuropathological states in which abnormal fluid shifts are accompanied by alterations in the aggregation state or the molecular architecture of square arrays.
Thermus thermophilus
: A link in evolution of the tRNA-dependent amino acid amidation pathways
Authors: Becker Hubert Dominique , Kern Daniel
Published: July 2002

Thermus thermophilus
possesses an aspartyl-tRNA synthetase (AspRS2) able to aspartylate efficiently tRNA
Asp
and tRNA
Asn
. Aspartate mischarged on tRNA
Asn
then is converted into asparagine by an ω amidase that differs structurally from all known asparagine synthetases. However, aspartate is not misincorporated into proteins because the binding capacity of aminoacylated tRNA
Asn
to elongation factor Tu is only conferred by conversion of aspartate into asparagine.
T. thermophilus
additionally contains a second aspartyl-tRNA synthetase (AspRS1) able to aspartylate tRNA
Asp
and an asparaginyl-tRNA synthetase able to charge tRNA
Asn
with free asparagine, although the organism does not contain a tRNA-independent asparagine synthetase. In contrast to the duplicated pathway of tRNA asparaginylation, tRNA glutaminylation occurs in the thermophile via the usual pathway by using glutaminyl-tRNA synthetase and free glutamine synthesized by glutamine synthetase that is unique.
T. thermophilus
is able to ensure tRNA aminoacylation by alternative routes involving either the direct pathway or by conversion of amino acid mischarged on tRNA. These findings shed light on the interrelation between the tRNA-dependent and tRNA-independent pathways of amino acid amidation and on the processes involved in fidelity of the aminoacylation systems.
Pancreas development is promoted by cyclopamine, a Hedgehog signaling inhibitor
Authors: Kim Seung K. , Melton Douglas A.
Published: July 2002

Exposure to cyclopamine, a steroid alkaloid that blocks Sonic hedgehog (
Shh
) signaling, promotes pancreatic expansion in embryonic chicks. Heterotopic development of pancreatic endocrine and exocrine structures occurs in regions adjacent to the pancreas including stomach and duodenum, and insulin-producing islets in the pancreas are enlarged. The homeodomain transcription factor PDX1, required for pancreas development, is expressed broadly in the posterior foregut but pancreas development normally initiates only in a restricted region of PDX1-expressing posterior foregut where endodermal
Shh
expression is repressed. The results suggests that cyclopamine expands the endodermal region where
Shh
signaling does not occur, resulting in pancreatic differentiation in a larger region of PDX1-expressing foregut endoderm. Cyclopamine reveals the capacity of a broad region of the posterior embryonic foregut to form pancreatic cells and provides a means for expanding embryonic pancreas development.
The thermal explosion revisited
Authors: Barenblatt G. I. , Bell J. B. , Crutchfield W. Y.
Published: July 2002

The classical problem of the thermal explosion in a long cylindrical vessel is modified so that only a fraction α of its wall is ideally thermally conducting while the remaining fraction 1−α is thermally isolated. Partial isolation of the wall naturally reduces the critical radius of the vessel. Most interesting is the case when the structure of the boundary is a periodic one, so that the alternating conductive α and isolated 1−α parts of the boundary occupy together the segments 2π/
N
(
N
is the number of segments) of the boundary. A numerical investigation is performed. It is shown that at small α and large
N
, the critical radius obeys a scaling law with the coefficients depending on
N
. For large
N
, the result is obtained that in the central core of the vessel the temperature distribution is axisymmetric. In the boundary layer near the wall having the thickness ≈2π
r
0
/
N
(
r
0
is the radius of the vessel), the temperature distribution varies sharply in the peripheral direction. The temperature distribution in the axisymmetric core at the critical value of the vessel radius is subcritical.
Termination of signaling by protease-activated receptor-1 is linked to lysosomal sorting
Authors: Trejo JoAnn , Hammes Stephen R. , Coughlin Shaun R.
Published: July 2002

The irreversible proteolytic mechanism by which protease-activated receptor-1 (PAR1), the G protein-coupled receptor (GPCR) for thrombin, is activated raises the question of how it is shut off. Like classic GPCRs, activated PAR1 is rapidly phosphorylated and internalized, but unlike classic GPCRs, which recycle, internalized PAR1 is sorted to lysosomes. A chimeric PAR1 bearing the substance P receptor’s cytoplasmic carboxyl tail sequestered and recycled like wild-type substance P receptor. In cells expressing this chimera, signaling in response to the PAR1-activating peptide SFLLRN ceased as expected upon removal of this agonist. Strikingly, however, when the chimera was activated proteolytically by thrombin, signaling persisted even after thrombin was removed. This persistent signaling was apparently due to “resignaling” by previously activated receptors that had internalized and recycled back to the cell surface. Thus the cytoplasmic carboxyl tail of PAR1 specifies an intracellular sorting pattern that is linked to its signaling properties. In striking contrast to most GPCRs, sorting of activated PAR1 to lysosomes rather than recycling is critical for terminating PAR1 signaling—a trafficking solution to a signaling problem.
Anin vitroblood–brain barrier model: Cocultures between endothelial cells and organotypic brain slice cultures
Authors: Duport S. , Robert F. , Muller D. , Grau G. , Parisi L. , Stoppini L.
Published: July 2002

This communication describes a novelin vitroblood–brain barrier (BBB) model: organotypic slice cultures from the central nervous system were overlaid on endothelial cell monolayers grown on permeable membranes. Morphological, electrophysiological, and microdialysis approaches were carried out to characterize and validate this model. After 10 days in coculture, morphological studies reveal the presence of tight junctions. Electrophysiological recordings of neuronal activity performed on organotypic cultures with or without an endothelial cell monolayer show that amplitude of evoked responses were comparable, indicating good viability of cocultures after 2 weeks. Perfusion of known BBB permeable or nonpermeable molecules was used to test the coculture tightness in conjunction with electrophysiological or microdialysis approaches: application of glutamate (Glu), which doesn’t easily cross the BBB, triggers off rhythmic activity only in control cultures, whereas epileptogenic activity was observed in both control cultures and cocultures during perfusions with picrotoxin, a molecule that can diffuse through the BBB. Finally, the microdialysis technique was used to determine the permeability of molecules coming from the perfusion chamber:l-dopa, dopamine, and Glu were employed to assess the selective permeability of the coculture model. Thus, these results indicate that thein vitromodel described possesses characteristics similar to those of the BBBin situand that cocultures of organotypic slices and endothelial cell monolayers have potential as a powerful tool for studying biochemical mechanisms regulating BBB function and drug delivery to the central nervous system.
Where the imaginal appears real: A positron emission tomography study of auditory hallucinations
Authors: Szechtman Henry , Woody Erik , Bowers Kenneth S. , Nahmias Claude
Published: July 2002

An auditory hallucination shares with imaginal hearing the property of being self-generated and with real hearing the experience of the stimulus being an external one. To investigate where in the brain an auditory event is “tagged” as originating from the external world, we used positron emission tomography to identify neural sites activated by both real hearing and hallucinations but not by imaginal hearing. Regional cerebral blood flow was measured during hearing, imagining, and hallucinating in eight healthy, highly hypnotizable male subjects prescreened for their ability to hallucinate under hypnosis (hallucinators). Control subjects were six highly hypnotizable male volunteers who lacked the ability to hallucinate under hypnosis (nonhallucinators). A region in the right anterior cingulate (Brodmann area 32) was activated in the group of hallucinators when they heard an auditory stimulus and when they hallucinated hearing it but not when they merely imagined hearing it. The same experimental conditions did not yield this activation in the group of nonhallucinators. Inappropriate activation of the right anterior cingulate may lead self-generated thoughts to be experienced as external, producing spontaneous auditory hallucinations.
Functional disruption in the organization of the brain for reading in dyslexia
Authors: Shaywitz Sally E. , Shaywitz Bennett A. , Pugh Kenneth R. , Fulbright Robert K. , Constable R. Todd , Mencl W. Einar , Shankweiler Donald P. , Liberman Alvin M. , Skudlarski Pawel , Fletcher Jack M. , Katz Leonard , Marchione Karen E. , Lacadie Cheryl , Gatenby Christopher , Gore John C.
Published: July 2002

Learning to read requires an awareness that spoken words can be decomposed into the phonologic constituents that the alphabetic characters represent. Such phonologic awareness is characteristically lacking in dyslexic readers who, therefore, have difficulty mapping the alphabetic characters onto the spoken word. To find the location and extent of the functional disruption in neural systems that underlies this impairment, we used functional magnetic resonance imaging to compare brain activation patterns in dyslexic and nonimpaired subjects as they performed tasks that made progressively greater demands on phonologic analysis. Brain activation patterns differed significantly between the groups with dyslexic readers showing relative underactivation in posterior regions (Wernicke’s area, the angular gyrus, and striate cortex) and relative overactivation in an anterior region (inferior frontal gyrus). These results support a conclusion that the impairment in dyslexia is phonologic in nature and that these brain activation patterns may provide a neural signature for this impairment.
Calcimimetics with potent and selective activity on the parathyroid calcium receptor
Authors: Nemeth Edward F. , Steffey Michael E. , Hammerland Lance G. , Hung Benjamin C. P. , Van Wagenen Bradford C. , DelMar Eric G. , Balandrin Manuel F.
Published: July 2002

Parathyroid hormone (PTH) secretion is regulated by a cell surface Ca
2+
receptor that detects small changes in the level of plasma Ca
2+
. Because this G protein-coupled receptor conceivably provides a distinct molecular target for drugs useful in treating bone and mineral-related disorders, we sought to design small organic molecules that act on the Ca
2+
receptor. We discovered that certain phenylalkylamine compounds, typified by NPS R-568 and its deschloro derivative NPS R-467, increased the concentration of cytoplasmic Ca
2+
([Ca
2+
]
i
) in bovine parathyroid cells and inhibited PTH secretion at nanomolar concentrations. These effects were stereoselective and the
R
enantiomers were 10- to 100-fold more potent than the
S
enantiomers. NPS R-568 potentiated the effects of extracellular Ca
2+
on [Ca
2+
]
i
and PTH secretion but was without effect in the absence of extracellular Ca
2+
. Both compounds shifted the concentration–response curves for extracellular Ca
2+
to the left. Presumably, these compounds act as positive allosteric modulators to increase the sensitivity of the Ca
2+
receptor to activation by extracellular Ca
2+
. Both NPS R-467 and NPS R-568 increased [Ca
2+
]
i
in HEK 293 cells expressing the human parathyroid Ca
2+
receptor but were without effect in wild-type HEK 293 cells. Neither compound affected the cytoplasmic Ca
2+
responses elicited by several other G protein-coupled receptors in HEK 293 cells or in bovine parathyroid cells. Significantly, these compounds did not affect responses elicited by the homologous metabotropic glutamate receptors, mGluR1a, mGluR2, or mGluR8. These compounds therefore act selectively on the Ca
2+
receptor. Compounds that mimic or potentiate the effects of extracellular Ca
2+
at the Ca
2+
receptor are termed calcimimetics. The discovery of calcimimetic compounds with potent and selective activity enables a pharmacological approach to regulating plasma levels of PTH. Calcimimetic compounds could conceivably provide a specific medical therapy for primary hyperparathyroidism.
High expression levels in cones of RGS9, the predominant GTPase accelerating protein of rods
Authors: Cowan Christopher W. , Fariss Robert N. , Sokal Izabela , Palczewski Krzysztof , Wensel Theodore G.
Published: July 2002

RGS9 is a member of the RGS family of GTPase accelerating proteins (GAPs) for heterotrimeric G proteins. We have explored its contribution to GTPase acceleration in mammalian rod and cone photoreceptors. When RGS9 was specifically removed from detergent extracts of rod outer segments by immunodepletion, the extracts lost nearly all of their GAP activity stimulatable by the inhibitory subunit of cGMP phosphodiesterase. Immunolocalization using monoclonal antibodies and confocal microscopy revealed that RGS9 is present in cones at significantly higher levels than in rods. Thus, RGS9 is the predominant source of GAP activity in rod outer segments, and RGS9 concentration emerges as a potentially important determinant of the faster response kinetics and lower sensitivity of mammalian cones, as compared with rods.
Stripe formation in juvenile
Pomacanthus
explained by a generalized Turing mechanism with chemotaxis
Authors: Painter K. J. , Maini P. K. , Othmer H. G.
Published: July 2002

Current interest in pattern formation can be traced to a seminal paper by Turing, who demonstrated that a system of reacting and diffusing chemicals, called morphogens, can interact so as to produce stable nonuniform concentration patterns in space. Recently, a Turing model has been suggested to explain the development of pigmentation patterns on species of growing angelfish such as
Pomacanthus semicirculatus
, which exhibit readily observed changes in the number, size, and orientation of colored stripes during development of juvenile and adult stages, but the model fails to predict key features of the observations on stripe formation. Here we develop a generalized Turing model incorporating cell growth and movement, we analyze the effects of these processes on patterning, and we demonstrate that the model can explain important features of pattern formation in a growing system such as
Pomacanthus.
The applicability of classical Turing models to biological pattern formation is limited by virtue of the sensitivity of patterns to model parameters, but here we show that the incorporation of growth results in robustly generated patterns without strict parameter control. In the model, chemotaxis in response to gradients in a morphogen distribution leads to aggregation of one type of pigment cell into a striped spatial pattern.
PTEN modulates cell cycle progression and cell survival by regulating phosphatidylinositol 3,4,5,-trisphosphate and Akt/protein kinase B signaling pathway
Authors: Sun Hong , Lesche Ralf , Li Da-Ming , Liliental Joanna , Zhang Hui , Gao Jing , Gavrilova Nadia , Mueller Brenda , Liu Xin , Wu Hong
Published: July 2002

To investigate the molecular basis of PTEN-mediated tumor suppression, we introduced a null mutation into the mouse
Pten
gene by homologous recombination in embryonic stem (ES) cells.
Pten
−/−
ES cells exhibited an increased growth rate and proliferated even in the absence of serum. ES cells lacking PTEN function also displayed advanced entry into S phase. This accelerated G
1
/S transition was accompanied by down-regulation of p27
KIP1
, a major inhibitor for G
1
cyclin-dependent kinases. Inactivation of PTEN in ES cells and in embryonic fibroblasts resulted in elevated levels of phosphatidylinositol 3,4,5,-trisphosphate, a product of phosphatidylinositol 3 kinase. Consequently, PTEN deficiency led to dosage-dependent increases in phosphorylation and activation of Akt/protein kinase B, a well-characterized target of the phosphatidylinositol 3 kinase signaling pathway. Akt activation increased Bad phosphorylation and promoted
Pten
−/−
cell survival. Our studies suggest that PTEN regulates the phosphatidylinositol 3,4,5,-trisphosphate and Akt signaling pathway and consequently modulates two critical cellular processes: cell cycle progression and cell survival.
Tetrodotoxin-resistant Na+currents and inflammatory hyperalgesia
Authors: Gold Michael S.
Published: July 2002

Several mechanisms have been identified that may underlie inflammation-induced sensitization of high-threshold primary afferent neurons, including the modulation of voltage- and Ca2+-dependent ion channels and ion channels responsible for the production of generator potentials. One such mechanism that has recently received a lot of attention is the modulation of a tetrodotoxin (TTX)-resistant voltage-gated Na+current. Evidence supporting a role for TTX-resistant Na+currents in the sensitization of primary afferent neurons and inflammatory hyperalgesia is reviewed. Such evidence is derived from studies on the distribution of TTX-resistant Na+currents among primary afferent neurons and other tissues of the body that suggest that these currents are expressed only in a subpopulation of primary afferent neurons that are likely to be involved in nociception. Data from studies on the biophysical properties of these currents suggest that they are ideally suited to mediate the repetitive discharge associated with prolonged membrane depolarizations. Data from studies on the effects of inflammatory mediators and antinociceptive agents on TTX-resistant Na+currents suggest that modulation of these currents is an underlying mechanism of primary afferent neuron sensitization. In addition, the second-messenger pathways underlying inflammatory mediator-induced modulation of these currents appear to underlie inflammatory mediator-induced hyperalgesia. Finally, recent antisense studies have also yielded data supporting a role for TTX-resistant Na+currents in inflammatory hyperalgesia. Although data from these studies are compelling, data presented at the Neurobiology of Pain colloquium raised a number of interesting questions regarding the role of TTX-resistant Na+currents in inflammatory hyperalgesia; implications of three of these questions are discussed.
RNase P RNAs from some Archaea are catalytically active
Authors: Pannucci James A. , Haas Elizabeth S. , Hall Thomas A. , Harris J. Kirk , Brown James W.
Published: July 2002

The RNA subunits of RNase Ps of Archaea and eukaryotes have been thought to depend fundamentally on protein for activity, unlike those of Bacteria that are capable of efficient catalysis in the absence of protein. Although the eukaryotic RNase P RNAs are quite different than those of Bacteria in both sequence and structure, the archaeal RNAs generally contain the sequences and structures of the bacterial, phylogenetically conserved catalytic core. A spectrum of archaeal RNase P RNAs were therefore tested for activity in a wide range of conditions. Many remain inactive in ionically extreme conditions, but catalytic activity could be detected from those of the methanobacteria, thermococci, and halobacteria. Chimeric holoenzymes, reconstituted from the
Methanobacterium
RNase P RNA and the
Bacillus subtilis
RNase P protein subunits, were functional at low ionic strength. The properties of the archaeal RNase P RNAs (high ionic-strength requirement, low affinity for substrate, and catalytic reconstitution by bacterial RNase P protein) are similar to synthetic RNase P RNAs that contain all of the catalytic core of the bacterial RNA but lack phylogenetically variable, stabilizing elements.
Mitomycin resistance in mammalian cells expressing the bacterial mitomycin C resistance protein MCRA
Authors: Belcourt Michael F. , Penketh Philip G. , Hodnick William F. , Johnson David A. , Sherman David H. , Rockwell Sara , Sartorelli Alan C.
Published: July 2002

The mitomycin C-resistance gene,
mcrA
, of
Streptomyces lavendulae
produces MCRA, a protein that protects this microorganism from its own antibiotic, the antitumor drug mitomycin C. Expression of the bacterial
mcrA
gene in mammalian Chinese hamster ovary cells causes profound resistance to mitomycin C and to its structurally related analog porfiromycin under aerobic conditions but produces little change in drug sensitivity under hypoxia. The mitomycins are prodrugs that are enzymatically reduced and activated intracellularly, producing cytotoxic semiquinone anion radical and hydroquinone reduction intermediates.
In vitro
, MCRA protects DNA from cross-linking by the hydroquinone reduction intermediate of these mitomycins by oxidizing the hydroquinone back to the parent molecule; thus, MCRA acts as a hydroquinone oxidase. These findings suggest potential therapeutic applications for MCRA in the treatment of cancer with the mitomycins and imply that intrinsic or selected mitomycin C resistance in mammalian cells may not be due solely to decreased bioactivation, as has been hypothesized previously, but instead could involve an MCRA-like mechanism.
Morphological, physiological, and biochemical changes in rhodopsin knockout mice
Authors: Lem J. , Krasnoperova N. V. , Calvert P. D. , Kosaras B. , Cameron D. A. , Nicolò M. , Makino C. L. , Sidman R. L.
Published: July 2002

Mutations in rod opsin, the visual pigment protein of rod photoreceptors, account for ≈15% of all inherited human retinal degenerations. However, the physiological and molecular events underlying the disease process are not well understood. One approach to this question has been to study transgenic mice expressing opsin genes containing defined mutations. A caveat of this approach is that even the overexpression of normal opsin leads to photoreceptor cell degeneration. To overcome the problem, we have reduced or eliminated endogenous rod opsin content by targeted gene disruption. Retinas in mice lacking both opsin alleles initially developed normally, except that rod outer segments failed to form. Within months of birth, photoreceptor cells degenerated completely. Retinas from mice with a single copy of the opsin gene developed normally, and rods elaborated outer segments of normal size but with half the normal complement of rhodopsin. Photoreceptor cells in these retinas also degenerated but did so over a much slower time course. Physiological and biochemical experiments showed that rods from mice with a single opsin gene were ≈50% less sensitive to light, had accelerated flash-response kinetics, and contained ≈50% more phosducin than wild-type controls.
Individuality and adaptation across levels of selection: How shall we name and generalize the unit of Darwinism?
Authors: Gould Stephen Jay , Lloyd Elisabeth A.
Published: July 2002

Two major clarifications have greatly abetted the understanding and fruitful expansion of the theory of natural selection in recent years: the acknowledgment that interactors, not replicators, constitute the causal unit of selection; and the recognition that interactors are Darwinian individuals, and that such individuals exist with potency at several levels of organization (genes, organisms, demes, and species in particular), thus engendering a rich hierarchical theory of selection in contrast with Darwin’s own emphasis on the organismic level. But a piece of the argument has been missing, and individuals at levels distinct from organisms have been denied potency (although granted existence within the undeniable logic of the theory), because they do not achieve individuality with the same devices used by organisms and therefore seem weak by comparison. We show here that different features define Darwinian individuality across scales of size and time. In particular, species-individuals may develop few emergent features as direct adaptations. The interactor approach works with emergent fitnesses, not with emergent features; and species, as a consequence of their different mechanism for achieving individuality (reproductive exclusivity among subparts, that is, among organisms), express many effects from other levels. Organisms, by contrast, suppress upwardly cascading effects, because the organismic style of individuality (by functional integration of subparts) does not permit much competition or differential reproduction of parts from within. Species do not suppress the operation of lower levels; such effects therefore become available as exaptations conferring emergent fitness—a primary source of the different strength that species achieve as effective Darwinian individuals in evolution.
PICKLE is a CHD3 chromatin-remodeling factor that regulates the transition from embryonic to vegetative development in
Arabidopsis
Authors: Ogas Joe , Kaufmann Scott , Henderson Jim , Somerville Chris
Published: July 2002

The life cycle of angiosperms is punctuated by a dormant phase that separates embryonic and postembryonic development of the sporophyte. In the
pickle
(
pkl
) mutant of
Arabidopsis
, embryonic traits are expressed after germination. The penetrance of the
pkl
phenotype is strongly enhanced by inhibitors of gibberellin biosynthesis. Map-based cloning of the
PKL
locus revealed that it encodes a CHD3 protein. CHD3 proteins have been implicated as chromatin-remodeling factors involved in repression of transcription. PKL is necessary for repression of
LEC1
, a gene implicated as a critical activator of embryo development. We propose that PKL is a component of a gibberellin-modulated developmental switch that functions during germination to prevent reexpression of the embryonic developmental state.
Syndecan-4 signals cooperatively with integrins in a Rhodependent manner in the assembly of focal adhesions and actin stress fibers
Authors: Saoncella Stefania , Echtermeyer Frank , Denhez Fabienne , Nowlen Julie K. , Mosher Deane F. , Robinson Stephen D. , Hynes Richard O. , Goetinck Paul F.
Published: July 2002

The assembly of focal adhesions and actin stress fibers by cells plated on fibronectin depends on adhesion-mediated signals involving both integrins and cell-surface heparan sulfate proteoglycans. These two cell-surface receptors interact with different domains of fibronectin. To attempt to identify the heparan sulfate proteoglycans involved, we used fibronectin-null (FN−/−) mouse fibroblasts to eliminate the contribution of endogenous fibronectin during the analysis. FN−/− fibroblasts plated on the cell-binding domain of fibronectin or on antibodies directed against mouse β1 integrin chains attach but fail to spread and do not form focal adhesions or actin stress fibers. When such cells are treated with antibodies directed against the ectodomain of mouse syndecan-4, they spread fully and assemble focal adhesions and actin stress fibers indistinguishable from those seen in cells plated on intact fibronectin. These results identify syndecan-4 as a heparan sulfate proteoglycan involved in the assembly process. The antibody-stimulated assembly of focal adhesions and actin stress fibers in cells plated on the cell-binding domain of fibronectin can be blocked with C3 exotransferase, an inhibitor of the small GTP-binding protein Rho. Treatment of cells with lysophosphatidic acid, which activates Rho, results in full spreading and assembly of focal adhesions and actin stress fibers in fibroblasts plated on the cell-binding domain of fibronectin. We conclude that syndecan-4 and integrins can act cooperatively in generating signals for cell spreading and for the assembly of focal adhesions and actin stress fibers. We conclude further that these joint signals are regulated in a Rho-dependent manner.