bluuebunny/crossref_metadata_2025 huggingface dataset:
Periodic permanent magnet focusing of an annular electron beam and its application to a 250 MW ubitron free-electron maser
Authors: McDermott D. B. , Balkcum A. J. , Phillips R. M. , Luhmann N. C.
Published: July 2002

Stable electron beam flow is shown to exist for an annular electron beam within a coaxial periodic permanent magnet wiggler and transmission line with zero guide field. When the beam is properly centered near the magnetic minimum of the wiggler, a condition exists where the magnetic radial force balances the space-charge repulsion of the beam. The stability condition relating the electron beam current to the magnetic field strength in terms of the plasma frequency, wiggler cyclotron frequency and relativistic Lorentz factor is ω2p=(γ/2)Ω2w, which is the same stability condition found for Brillouin flow in a uniform magnetic field and for focused beam flow along periodic dipole magnetic fields. The radial scallop of an annular electron beam satisfying this condition can be extremely low. Although this propagation technique can be utilized for any high power coaxial linear-beam device, it is most appropriate for free electron masers. Using parameters satisfying the stability condition, a 500 kV, 1 kA, TE01 ubitron free-electron maser design is presented that is predicted to generate 250 MW at 11.4 GHz.
On electron acceleration by intense laser pulses in the presence of a stochastic field
Authors: Meyer-ter-Vehn J. , Sheng Z. M.
Published: July 2002

Electron acceleration by intense laser pulses is studied in the presence of a stochastic field representing a background plasma. Electron distributions are generated peaked in the direction of laser propagation and having a quasi-thermal energy spectrum. Effective temperatures are obtained above the ponderomotive energy. They scale with laser intensity I0 and interaction time t0 proportional to I01/2t0α with α≈0.5−1.0.
Demonstration of time-dependent symmetry control in hohlraums by drive-beam staggering
Authors: Turner R. E. , Amendt P. , Landen O. L. , Glendinning S. G. , Bell P. , Decker C. , Hammel B. A. , Kalantar D. , Lee D. , Wallace R. , Bradley D. , Cable M. , Craxton R. S. , Kremens R. , Seka W. , Schnittman J. , Thorp K. , Murphy T. J. , Delamater N. , Barnes Cris W. , Hauer A. , Magelssen G. , Wallace J.
Published: July 2002

Indirect-drive inertial confinement fusion makes use of cavities constructed of high atomic number materials to convert laser power into x-rays for ablatively driving an implosion capsule. Obtaining spatially uniform drive on the capsule requires a careful balancing between the laser absorption region (high drive) and the laser entrance holes (low drive). This balancing is made difficult because of plasma expansion, and the associated movement of the laser absorption region with time. This paper reports the first experimental demonstration of compensation for this motion by using different laser beams at different times, in agreement with modeling.
Photoacoustic calorimetry of photovoltaic cells: Use of phase shifts to indicate thermal loss mechanisms
Authors: Cahen David , Halle Scott D.
Published: July 2002

Preliminary results are presented of the photoacoustic phase angle dependence, for a Si solar cell, on load resistance, illumination intensity, and photon energy. The data are interpreted using a simple, phenomenological model that assigns the thermal loss mechanisms occurring in the photovoltaic device to the diffused (top) layer, the junction region, and the base of the cell.
Reflected degenerate four-wave mixing on GaAs single quantum wells
Authors: Honold A. , Schultheis L. , Kuhl J. , Tu C. W.
Published: July 2002

Time-resolved degenerate four-wave mixing (DFWM) on two-dimensional (2D) excitons in GaAs single quantum wells is studied. We observe backward coherent emission (DFWM signal) from the 2D excitons comparable in efficiency to that in forward direction. This reflection or backward DFWM configuration is extremely advantageous and useful in exploring optically thin semiconductor layers.
Targeted inhibition of calcineurin attenuates cardiac hypertrophy
in vivo
Authors: De Windt Leon J. , Lim Hae W. , Bueno Orlando F. , Liang Qiangrong , Delling Ulrike , Braz Julian C. , Glascock Betty J. , Kimball Thomas F. , del Monte Federica , Hajjar Roger J. , Molkentin Jeffery D.
Published: July 2002

The Ca
2+
-calmodulin-activated Ser/Thr
protein phosphatase calcineurin and the downstream transcriptional
effectors of calcineurin, nuclear factor of activated T cells, have
been implicated in the hypertrophic response of the myocardium.
Recently, the calcineurin inhibitory agents cyclosporine A and FK506
have been extensively used to evaluate the importance of this signaling
pathway in rodent models of cardiac hypertrophy. However, pharmacologic
approaches have rendered equivocal results necessitating more specific
or genetic-based inhibitory strategies. In this regard, we have
generated Tg mice expressing the calcineurin inhibitory domains of
Cain/Cabin-1 and A-kinase anchoring protein 79 specifically in the
heart. ΔCain and ΔA-kinase-anchoring protein Tg mice demonstrated
reduced cardiac calcineurin activity and reduced hypertrophy in
response to catecholamine infusion or pressure overload. In a second
approach, adenoviral-mediated gene transfer of ΔCain was
performed in the adult rat myocardium to evaluate the effectiveness of
an acute intervention and any potential species dependency. ΔCain
adenoviral gene transfer inhibited cardiac calcineurin activity and
reduced hypertrophy in response to pressure overload without reducing
aortic pressure. These results provide genetic evidence implicating
calcineurin as an important mediator of the cardiac hypertrophic
response
in vivo
.
Primary role for adherent leukocytes in sickle cell vascular occlusion: A new paradigm
Authors: Turhan Aslihan , Weiss Linnea A. , Mohandas Narla , Coller Barry S. , Frenette Paul S.
Published: July 2002

Vascular occlusion is the major cause of morbidity and mortality in sickle cell disease but its mechanisms are poorly understood. We demonstrate by using intravital microscopy in mice expressing human sickle hemoglobin (SS) that SS red blood cells (RBCs) bind to adherent leukocytes in inflamed venules, producing vasoocclusion of cremasteric venules. SS mice deficient in P- and E-selectins, which display defective leukocyte recruitment to the vessel wall, are protected from vasoocclusion. These data uncover a previously unsuspected paradigm for the pathogenesis of sickle cell vasoocclusion in which adherent leukocytes play a direct role and suggest that drugs targeting SS RBC–leukocyte or leukocyte–endothelial interactions may prevent or treat the vascular complications of this debilitating disease.
Clonally expanded mtDNA point mutations are abundant in individual cells of human tissues
Authors: Nekhaeva Ekaterina , Bodyak Natalya D. , Kraytsberg Yevgenya , McGrath Sean B. , Van Orsouw Nathalie J. , Pluzhnikov Anna , Wei Jeanne Y. , Vijg Jan , Khrapko Konstantin
Published: July 2002

Using single-cell sequence analysis, we discovered that a high proportion of cells in tissues as diverse as buccal epithelium and heart muscle contain high proportions of clonal mutant mtDNA expanded from single initial mutant mtDNA molecules. We demonstrate that intracellular clonal expansion of somatic point mutations is a common event in normal human tissues. This finding implies efficient homogenization of mitochondrial genomes within individual cells. Significant qualitative differences observed between the spectra of clonally expanded mutations in proliferating epithelial cells and postmitotic cardiomyocytes suggest, however, that either the processes generating these mutations or mechanisms driving them to homoplasmy are likely to be fundamentally different between the two tissues. Furthermore, the ability of somatic mtDNA mutations to expand (required for their phenotypic expression), as well as their apparently high incidence, reinforces the possibility that these mutations may be involved actively in various physiological processes such as aging and degenerative disease. The abundance of clonally expanded point mutations in individual cells of normal tissues also suggests that the recently discovered accumulation of mtDNA mutations in tumors may be explained by processes that are similar or identical to those operating in the normal tissue.
Acid potentiation of the capsaicin receptor determined by a key extracellular site
Authors: Jordt Sven-Eric , Tominaga Makoto , Julius David
Published: July 2002

The capsaicin (vanilloid) receptor, VR1, is a sensory neuron-specific ion channel that serves as a polymodal detector of pain-producing chemical and physical stimuli. The response of VR1 to capsaicin or noxious heat is dynamically potentiated by extracellular protons within a pH range encountered during tissue acidosis, such as that associated with arthritis, infarction, tumor growth, and other forms of injury. A molecular determinant for this important physiological activity was localized to an extracellular Glu residue (E600) in the region linking the fifth transmembrane domain with the putative pore-forming region of the channel. We suggest that this residue serves as a key regulatory site of the receptor by setting sensitivity to other noxious stimuli in response to changes in extracellular proton concentration. We also demonstrate that protons, vanilloids, and heat promote channel opening through distinct pathways, because mutations at a second site (E648) selectively abrogate proton-evoked channel activation without diminishing responses to other noxious stimuli. Our findings provide molecular evidence for stimulus-specific steps in VR1 activation and offer strategies for the development of novel analgesic agents.
Hypoxia alters gene expression in human neuroblastoma cells toward an immature and neural crest-like phenotype
Authors: Jögi Annika , Øra Ingrid , Nilsson Helén , Lindeheim Åsa , Makino Yuichi , Poellinger Lorenz , Axelson Håkan , Påhlman Sven
Published: July 2002

Insufficient oxygen and nutrient supply often restrain solid tumor growth, and the hypoxia-inducible factors (HIF) 1α and HIF-2α are key transcription regulators of phenotypic adaptation to low oxygen levels. Moreover, mouse gene disruption studies have implicated
HIF-2
α in embryonic regulation of
tyrosine hydroxylase
, a hallmark gene of the sympathetic nervous system. Neuroblastoma tumors originate from immature sympathetic cells, and therefore we investigated the effect of hypoxia on the differentiation status of human neuroblastoma cells. Hypoxia stabilized HIF-1α and HIF-2α proteins and activated the expression of known hypoxia-induced genes, such as
vascular endothelial growth factor
and
tyrosine hydroxylase
. These changes in gene expression also occurred in hypoxic regions of experimental neuroblastoma xenografts grown in mice. In contrast, hypoxia decreased the expression of several neuronal/neuroendocrine marker genes but induced genes expressed in neural crest sympathetic progenitors, for instance
c-kit
and
Notch-1
. Thus, hypoxia apparently causes dedifferentiation both
in vitro
and
in vivo
. These findings suggest a novel mechanism for selection of highly malignant tumor cells with stem-cell characteristics.
PLS1
, a gene encoding a tetraspanin-like protein, is required for penetration of rice leaf by the fungal pathogen
Magnaporthe grisea
Authors: Clergeot Pierre-Henri , Gourgues Mathieu , Cots Joaquim , Laurans F. , Latorse Marie-Pascale , Pépin Régis , Tharreau Didier , Notteghem Jean-Loup , Lebrun Marc-Henri
Published: July 2002

We describe in this study
punchless
, a nonpathogenic
mutant from the rice blast fungus
M. grisea,
obtained by
plasmid-mediated insertional mutagenesis. As do most fungal plant
pathogens,
M. grisea
differentiates an infection
structure specialized for host penetration called the appressorium. We
show that
punchless
differentiates appressoria that fail
to breach either the leaf epidermis or artificial membranes such as
cellophane. Cytological analysis of
punchless
appressoria shows that they have a cellular structure, turgor, and
glycogen content similar to those of wild type before penetration, but
that they are unable to differentiate penetration pegs. The inactivated
gene,
PLS1
, encodes a putative integral membrane protein
of 225 aa (Pls1p). A functional Pls1p-green fluorescent protein fusion
protein was detected only in appressoria and was localized in plasma
membranes and vacuoles. Pls1p is structurally related to the
tetraspanin family. In animals, these proteins are components of
membrane signaling complexes controlling cell differentiation,
motility, and adhesion. We conclude that
PLS1
controls
an appressorial function essential for the penetration of the fungus
into host leaves.
Biosynthesis of a major lipofuscin fluorophore in mice and humans with
ABCR
-mediated retinal and macular degeneration
Authors: Mata Nathan L. , Weng Jian , Travis Gabriel H.
Published: July 2002

Increased accumulation of lipofuscin in cells of the retinal pigment epithelium (RPE) is seen in several forms of macular degeneration, a common cause of blindness in humans. A major fluorophore of lipofuscin is the toxic
bis
-retinoid,
N
-retinylidene-
N
-retinylethanolamine (A2E). Previously, we generated mice with a knockout mutation in the
abcr
gene. This gene encodes rim protein (RmP), an ATP-binding cassette transporter in rod outer segments. Mice lacking RmP accumulate A2E in RPE cells at a greatly increased rate over controls. Here, we identify three precursors of A2E in ocular tissues from
abcr−/−
mice and humans with
ABCR
-mediated recessive macular degenerations. Our results corroborate the scheme proposed by C. A. Parish, M. Hashimoto, K. Nakanishi, J. Dillon & J. Sparrow [
Proc. Natl. Acad. Sci. USA
(1998) 95, 14609–14613], for the biosynthesis of A2E: (
i
) condensation of all-
trans
-retinaldehyde (all-
trans
-RAL) with phosphatidylethanolamine to form a Schiff base; (
ii
) condensation of the amine product with a second all-
trans
-RAL to form a
bis
-retinoid; (
iii
) oxidation to yield a pyridinium salt; and (
iv
) hydrolysis of the phosphate ester to yield A2E. The latter two reactions probably occur within RPE phagolysosomes. As predicted by this model, formation of A2E was completely inhibited when
abcr−/−
mice were raised in total darkness. Also, once formed, A2E was not eliminated by the RPE. These data suggest that humans with retinal or macular degeneration caused by loss of RmP function may slow progression of their disease by limiting exposure to light. The precursors of A2E identified in this study may represent pharmacological targets for the treatment of
ABCR
-mediated macular degeneration.
Identification of Renox, an NAD(P)H oxidase in kidney
Authors: Geiszt Miklós , Kopp Jeffrey B. , Várnai Péter , Leto Thomas L.
Published: July 2002

Oxygen sensing is essential for homeostasis in all aerobic organisms, but its mechanism is poorly understood. Data suggest that a phagocytic-like NAD(P)H oxidase producing reactive oxygen species serves as a primary sensor for oxygen. We have characterized a source of superoxide anions in the kidney that we refer to as a renal NAD(P)H oxidase or Renox. Renox is homologous to gp91phox(91-kDa subunit of the phagocyte oxidase), the electron-transporting subunit of phagocytic NADPH oxidase, and contains all of the structural motifs considered essential for binding of heme, flavin, and nucleotide.In situRNA hybridization revealed that renox is highly expressed at the site of erythropoietin production in the renal cortex, showing the greatest accumulation of renox mRNA in proximal convoluted tubule epithelial cells. NIH 3T3 fibroblasts overexpressing transfected Renox show increased production of superoxide and develop signs of cellular senescence. Our data suggest that Renox, as a renal source of reactive oxygen species, is a likely candidate for the oxygen sensor function regulating oxygen-dependent gene expression and may also have a role in the development of inflammatory processes in the kidney.
The RecD subunit of the
Escherichia coli
RecBCD enzyme inhibits RecA loading, homologous recombination, and DNA repair
Authors: Amundsen Susan K. , Taylor Andrew F. , Smith Gerald R.
Published: July 2002

The RecBCD enzyme is required for homologous recombination and DNA repair in
Escherichia coli
. The structure and function of RecBCD enzyme is altered on its interaction with the recombination hotspot Chi (5′-GCTGGTGG-3′). It has been hypothesized that the RecD subunit plays a role in Chi-dependent regulation of enzyme activity [Thaler, D. S., Sampson, E., Siddiqi, I., Rosenberg, S. M., Stahl, F. W. & Stahl, M. (1988) in
Mechanisms and Consequences of DNA Damage Processing
, eds. Friedberg, E. & Hanawalt, P. (Liss, New York), pp. 413–422; Churchill, J. J., Anderson, D. G. & Kowalczykowski, S. C. (1999)
Genes Dev.
13, 901–911]. We tested the hypothesis that the RecD subunit inhibits recombination by deleting
recD
from the nuclease- and recombination-deficient mutant

recB
D1080A

CD. We report here that the resulting strain,

recB
D1080A

C, was proficient for recombination and DNA repair. Recombination proficiency was accompanied by a change in enzyme activity: RecB
D1080A
C enzyme loaded RecA protein onto DNA during DNA unwinding whereas RecB
D1080A
CD enzyme did not. Together, these genetic and biochemical results demonstrate that RecA loading by RecBCD enzyme is required for recombination in
E. coli
cells and suggest that RecD interferes with the enzyme domain required for its loading. A nuclease-dependent signal appears to be required for a change in RecD that allows RecA loading. Because RecA loading is not observed with wild-type RecBCD enzyme until it acts at a Chi site, our observations support the view that RecD inhibits recombination until the enzyme acts at Chi.
Regulatory function ofin vivoanergized CD4+T cells
Authors: Jooss Karin , Gjata Bernard , Danos Olivier , von Boehmer Harald , Sarukhan Adelaida
Published: July 2002

It has been suggested that anergic T cells may not be only inert cells but may rather play an active role, for example by regulating immune responses. We have previously reported the existence of “anergic” IL-10-producing CD4+T cells generatedin vivoby continuous antigenic stimulation. Using a gene transfer system where the antigen recognized by such T cells is expressed in skeletal muscle by two different DNA viral vectors, we show that these cells not only remain tolerant toward their cognate antigen but also can suppress the immune response of naïve T cells against the immunogenic adenoviral proteins. Furthermore, they can completely inhibit tissue destruction that takes place as a result of an immune response. The system presented here is unique in that the T cells have been anergizedin vivo, their antigen specificity and functional status are known, and the amount, form, and timing of antigen expression can be manipulated. This model will therefore permit us to carefully dissect the mechanisms by which these anergic T cells regulate the priming and/or effector function of naïve T cells.
The Cα—H⋅⋅⋅O hydrogen bond: A determinant of stability and specificity in transmembrane helix interactions
Authors: Senes Alessandro , Ubarretxena-Belandia Iban , Engelman Donald M.
Published: July 2002

The Cα—H⋅⋅⋅O hydrogen bond has been given little attention as a determinant of transmembrane helix association. Stimulated by recent calculations suggesting that such bonds can be much stronger than has been supposed, we have analyzed 11 known membrane protein structures and found that apparent carbon α hydrogen bonds cluster frequently at glycine-, serine-, and threonine-rich packing interfaces between transmembrane helices. Parallel right-handed helix–helix interactions appear to favor Cα—H⋅⋅⋅O bond formation. In particular, Cα—H⋅⋅⋅O interactions are frequent between helices having the structural motif of the glycophorin A dimer and the GxxxG pair. We suggest that Cα—H⋅⋅⋅O hydrogen bonds are important determinants of stability and, depending on packing, specificity in membrane protein folding.
Mobilized bone marrow cells repair the infarcted heart, improving function and survival
Authors: Orlic Donald , Kajstura Jan , Chimenti Stefano , Limana Federica , Jakoniuk Igor , Quaini Federico , Nadal-Ginard Bernardo , Bodine David M. , Leri Annarosa , Anversa Piero
Published: July 2002

Attempts to repair myocardial infarcts by transplanting cardiomyocytes or skeletal myoblasts have failed to reconstitute healthy myocardium and coronary vessels integrated structurally and functionally with the remaining viable portion of the ventricular wall. The recently discovered growth and transdifferentiation potential of primitive bone marrow cells (BMC) prompted us, in an earlier study, to inject in the border zone of acute infarcts Lin
−
c-
kit
POS
BMC from syngeneic animals. These BMC differentiated into myocytes and vascular structures, ameliorating the function of the infarcted heart. Two critical determinants seem to be required for the transdifferentiation of primitive BMC: tissue damage and a high level of pluripotent cells. On this basis, we hypothesized here that BMC, mobilized by stem cell factor and granulocyte-colony stimulating factor, would home to the infarcted region, replicate, differentiate, and ultimately promote myocardial repair. We report that, in the presence of an acute myocardial infarct, cytokine-mediated translocation of BMC resulted in a significant degree of tissue regeneration 27 days later. Cytokine-induced cardiac repair decreased mortality by 68%, infarct size by 40%, cavitary dilation by 26%, and diastolic stress by 70%. Ejection fraction progressively increased and hemodynamics significantly improved as a consequence of the formation of 15 × 10
6
new myocytes with arterioles and capillaries connected with the circulation of the unaffected ventricle. In conclusion, mobilization of primitive BMC by cytokines might offer a noninvasive therapeutic strategy for the regeneration of the myocardium lost as a result of ischemic heart disease and, perhaps, other forms of cardiac pathology.
Mitochondria play no roles in Mn(II)-induced apoptosis in HeLa cells
Authors: Oubrahim Hammou , Stadtman Earl R. , Chock P. Boon
Published: July 2002

Manganese(II) has been shown to exhibit catalase-like
activity under physiological conditions. In the course of studies to
test the antioxidant activity of Mn(II) on HeLa cells, it was observed
at high concentrations (1–2 mM) that Mn(II) also induced
apoptosis, as judged by changes in cell morphology, caspase-3
activation, cleavage of poly(ADP) ribose, and DNA condensation.
However, in contrast to established mechanisms, the Mn(II)-induced
apoptosis is associated with an increase rather than a decrease
in mitochondrial inner-membrane potential, as monitored by the
fluorescent probe tetramethylrhodamine ethyl ester. Based on
immunochemical analysis, Mn(II)-induced apoptosis does not lead
to the release of cytochrome
c
into the cytosol. These
and other measurements show that treatment with Mn(II) leads to
enhancement of the mitochondrial “membrane mass,” has no effect
on mitochondrial volume, and does not affect the permeability
transition pore. Together, these results support the view that
Mn(II)-induced apoptosis occurs by a heretofore unrecognized
mechanism. In addition, it was demonstrated that Mn(II) treatment leads
to an increase in the production of reactive oxygen species (peroxides)
and to the induction of the manganese superoxide dismutase and catalase
activities but has no effect on the Cu,Zn-superoxide dismutase level.
Identification of proteins that interact with mammalian peptide:
N
-glycanase and implicate this hydrolase in the proteasome-dependent pathway for protein degradation
Authors: Park Hangil , Suzuki Tadashi , Lennarz William J.
Published: July 2002

Peptide:
N
-glycanase (PNGase) cleaves
oligosaccharide chains from glycopeptides and glycoproteins. Recently
the deduced amino acid sequence of a cytoplasmic PNGase has been
identified in various eukaryotes ranging from yeast to mammals,
suggesting that deglycosylation may play a central role in some
catabolic process. Several lines of evidence indicate that the
cytoplasmic enzyme is involved in the quality control system for newly
synthesized glycoproteins. Two-hybrid library screening by using mouse
PNGase as the target yielded several PNGase-interacting proteins that
previously had been implicated in proteasome-dependent protein
degradation: mHR23B, ubiquitin, a regulatory subunit of the 19S
proteasome, as well as a protein containing an ubiquitin
regulatory motif (UBX) and an ubiquitin-associated motif (UBA). These
findings by using the two-hybrid system were further confirmed either
by
in vitro
binding assays or size fractionation assays.
These results suggest that PNGase may be required for efficient
proteasome-mediated degradation of misfolded glycoproteins in mammalian
cells.
Functional redundancy of cryptochromes and classical photoreceptors for nonvisual ocular photoreception in mice
Authors: Selby Christopher P. , Thompson Carol , Schmitz Therese M. , Van Gelder Russell N. , Sancar Aziz
Published: July 2002

The daily light–dark (LD) cycle exerts a powerful influence on the
temporal organization of behavior and physiology. Much of this
influence is preserved in behaviorally blind retinally degenerate mice;
the photoreceptors underlying this nonvisual phototransduction are
unknown. The mammalian eye contains at least two classes of photoactive
pigments, the vitamin A-based opsins and the vitamin
B
2
-based cryptochromes. To genetically define the roles of
these pigments in light modulation of behavior, we generated
rd/rd
;
mCry1
−
/mCry1
−
;mCry2
−
/mCry2
−
mutant mice lacking rods and most cones as well as both cryptochrome
proteins. The response of the mutant mouse to photic input was analyzed
at both behavioral and molecular levels. Behaviorally, mice lacking
either classical photoreceptors or cryptochromes exhibited strongly
rhythmic locomotor responses to 10 and 100 lux daily LD 12 h/12-h
cycles; however, triple mutant mice carrying both cryptochrome and
retinal degenerate mutations were nearly arrhythmic under both LD
cycles and in constant darkness. At the molecular level, the light
induction of c-
fos
transcription in the suprachiasmatic
nucleus was markedly reduced in the triple mutant mouse compared with
either
rd/rd
or cryptochrome mutant mice. These data
indicate that classical opsins and cryptochromes serve functionally
redundant roles in the transduction of light information to behavioral
modulation and suggest a pleomorphic role for cryptochromes in both
photoreception and central clock mechanism.
The estrogen receptor locus is associated with a major gene influencing litter size in pigs.
Authors: Rothschild M , Jacobson C , Vaske D , Tuggle C , Wang L , Short T , Eckardt G , Sasaki S , Vincent A , McLaren D , Southwood O , van der Steen H , Mileham A , Plastow G
Published: July 2002

Identification of individual major genes affecting quantitative traits in livestock species has been limited to date. By using a candidate gene approach and a divergent breed cross involving the Chinese Meishan pig, we have shown that a specific allele of the estrogen receptor (ER) locus is associated with increased litter size. Female pigs from synthetic lines with a 50% Meishan background that were homozygous for this beneficial allele produced 2.3 more pigs in first parities and 1.5 more pigs averaged over all parities than females from the same synthetic lines and homozygous for the undesirable allele. This beneficial ER allele was also found in pigs with Large White breed ancestory. Analysis of females with Large White breed background showed an advantage for females homozygous for the beneficial allele as compared to females homozygous for the other allele of more than 1 total pig born. Analyses of growth performance test records detected no significant unfavorable associations of the beneficial allele with growth and developmental traits. Mapping of the ER gene demonstrated that the closest known genes or markers were 3 centimorgans from ER. To our knowledge, one of these, superoxide dismutase gene (SOD2), was mapped for the first time in the pig. Analysis of ER and these linked markers indicated that ER is the best predictor of litter size differences. Introgression of the beneficial allele into commercial pig breeding lines, in which the allele was not present, and marker-assisted selection for the beneficial allele in lines with Meishan and Large White background have begun.
A potential pathogenetic mechanism for multiple endocrine neoplasia type 2 syndromes involves ret-induced impairment of terminal differentiation of neuroepithelial cells.
Authors: Califano D , D'Alessio A , Colucci-D'Amato G L , De Vita G , Monaco C , Santelli G , Di Fiore P P , Vecchio G , Fusco A , Santoro M , de Franciscis V
Published: July 2002

Germ-line missense mutations of the receptor-like tyrosine kinase ret are the causative genetic event of the multiple endocrine neoplasia (MEN) type 2A and type 2B syndromes and of the familial medullary thyroid carcinoma. We have used the rat pheochromocytoma cell line, PC12, as a model system to investigate the mechanism or mechanisms by which expression of activated ret alleles contributes to the neoplastic phenotype in neuroendocrine cells. Here we show that stable expression of ret mutants (MEN2A and MEN2B alleles) in PC12 cells causes a dramatic conversion from a round to a flat morphology, accompanied by the induction of genes belonging to the early as well as the delayed response to nerve growth factor. However, in the transfected PC12 cells, the continuous expression of neuronal specific genes is not associated with the suppression of cell proliferation. Furthermore, expression of ret mutants renders PC12 cells unresponsive to nerve growth factor-induced inhibition of proliferation. These results suggest that induction of an aberrant pattern of differentiation, accompanied by unresponsiveness to growth-inhibitory physiological signals, may be part of the mechanism of action of activated ret alleles in the pathogenesis of neuroendocrine tumors associated with MEN2 syndromes.
The chromosomal distribution of mouse odorant receptor genes.
Authors: Sullivan S L , Adamson M C , Ressler K J , Kozak C A , Buck L B
Published: July 2002

Odorant receptors (ORs) on nasal olfactory sensory neurons are encoded by a large multigene family. Each member of the family is expressed in a small percentage of neurons that are confined to one of several spatial zones in the nose but are randomly distributed throughout that zone. This pattern of expression suggests that when the sensory neuron selects which OR gene to express it may be confined to a particular zonal gene set of several hundred OR genes but select from among the members of that set via a stochastic mechanism. Both locus-dependent and locus-independent models of OR gene choice have been proposed. To investigate the feasibility of these models, we determined the chromosomal locations of 21 OR genes expressed in four different spatial zones. We found that OR genes are clustered within multiple loci that are broadly distributed in the genome. These loci lie within paralogous chromosomal regions that appear to have arisen by duplications of large chromosomal domains followed by extensive gene duplication and divergence. Our studies show that OR genes expressed in the same zone map to numerous loci; moreover, a single locus can contain genes expressed in different zones. These findings raise the possibility that OR gene choice may be locus-independent or involve consecutive stochastic choices.
Nitration and inactivation of manganese superoxide dismutase in chronic rejection of human renal allografts.
Authors: MacMillan-Crow L A , Crow J P , Kerby J D , Beckman J S , Thompson J A
Published: July 2002

Inflammatory processes in chronic rejection remain a serious clinical problem in organ transplantation. Activated cellular infiltrate produces high levels of both superoxide and nitric oxide. These reactive oxygen species interact to form peroxynitrite, a potent oxidant that can modify proteins to form 3-nitrotyrosine. We identified enhanced immunostaining for nitrotyrosine localized to tubular epithelium of chronically rejected human renal allografts. Western blot analysis of rejected tissue demonstrated that tyrosine nitration was restricted to a few specific polypeptides. Immunoprecipitation and amino acid sequencing techniques identified manganese superoxide dismutase, the major antioxidant enzyme in mitochondria, as one of the targets of tyrosine nitration. Total manganese superoxide dismutase protein was increased in rejected kidney, particularly in the tubular epithelium; however, enzymatic activity was significantly decreased. Exposure of recombinant human manganese superoxide dismutase to peroxynitrite resulted in a dose-dependent (IC50 = 10 microM) decrease in enzymatic activity and concomitant increase in tyrosine nitration. Collectively, these observations suggest a role for peroxynitrite during development and progression of chronic rejection in human renal allografts. In addition, inactivation of manganese superoxide dismutase by peroxynitrite may represent a general mechanism that progressively increases the production of peroxynitrite, leading to irreversible oxidative injury to mitochondria.
Faithful representation of similarities among three-dimensional shapes in human vision.
Authors: Cutzu F , Edelman S
Published: July 2002

Efficient and reliable classification of visual stimuli requires that their representations reside a low-dimensional and, therefore, computationally manageable feature space. We investigated the ability of the human visual system to derive such representations from the sensory input-a highly nontrivial task, given the million or so dimensions of the visual signal at its entry point to the cortex. In a series of experiments, subjects were presented with sets of parametrically defined shapes; the points in the common high-dimensional parameter space corresponding to the individual shapes formed regular planar (two-dimensional) patterns such as a triangle, a square, etc. We then used multidimensional scaling to arrange the shapes in planar configurations, dictated by their experimentally determined perceived similarities. The resulting configurations closely resembled the original arrangements of the stimuli in the parameter space. This achievement of the human visual system was replicated by a computational model derived from a theory of object representation in the brain, according to which similarities between objects, and not the geometry of each object, need to be faithfully represented.
The wing of the enhancer-binding domain of Mu phage transposase is flexible and is essential for efficient transposition.
Authors: Clubb R T , Mizuuchi M , Huth J R , Omichinski J G , Savilahti H , Mizuuchi K , Clore G M , Gronenborn A M
Published: July 2002

A tetramer of the Mu transposase (MuA) pairs the recombination sites, cleaves the donor DNA, and joins these ends to a target DNA by strand transfer. Juxtaposition of the recombination sites is accomplished by the assembly of a stable synaptic complex of MuA protein and Mu DNA. This initial critical step is facilitated by the transient binding of the N-terminal domain of MuA to an enhancer DNA element within the Mu genome (called the internal activation sequence, IAS). Recently we solved the three-dimensional solution structure of the enhancer-binding domain of Mu phage transposase (residues 1-76, MuA76) and proposed a model for its interaction with the IAS element. Site-directed mutagenesis coupled with an in vitro transposition assay has been used to assess the validity of the model. We have identified five residues on the surface of MuA that are crucial for stable synaptic complex formation but dispensable for subsequent events in transposition. These mutations are located in the loop (wing) structure and recognition helix of the MuA76 domain of the transposase and do not seriously perturb the structure of the domain. Furthermore, in order to understand the dynamic behavior of the MuA76 domain prior to stable synaptic complex formation, we have measured heteronuclear 15N relaxation rates for the unbound MuA76 domain. In the DNA free state the backbone atoms of the helix-turn-helix motif are generally immobilized whereas the residues in the wing are highly flexible on the pico- to nanosecond time scale. Together these studies define the surface of MuA required for enhancement of transposition in vitro and suggest that a flexible loop in the MuA protein required for DNA recognition may become structurally ordered only upon DNA binding.
Immune response of HLA-DQ8 transgenic mice to peptides from the third hypervariable region of HLA-DRB1 correlates with predisposition to rheumatoid arthritis.
Authors: Zanelli E , Krco C J , Baisch J M , Cheng S , David C S
Published: July 2002

The major histocompatibility complex class II genes play an important role in the genetic predisposition to many autoimmune diseases. In the case of rheumatoid arthritis (RA), the human leukocyte antigen (HLA)-DRB1 locus has been implicated in the disease predisposition. The "shared epitope" hypothesis predicts that similar motifs within the third hypervariable (HV3) regions of some HLA-DRB1 alleles are responsible for the class II-associated predisposition to RA. Using a line of transgenic mice expressing the DQB1*0302/DQA1*0301 (DQ8) genes in the absence of endogenous mouse class II molecules, we have analyzed the antigenicity of peptides covering the HV3 regions of RA-associated and nonassociated DRB1 molecules. Our results show that a correlation exists between proliferative response to peptides derived from the HV3 regions of DRB1 chains and nonassociation of the corresponding alleles with RA predisposition. While HV3 peptides derived from nonassociated DRB1 molecules are highly immunogenic in DQ8 transgenic mice, all the HV3 peptides derived from RA-associated DRB1 alleles fail to induce a DQ8-restricted T-cell response. These data suggest that the role of the "shared epitope" in RA predisposition may be through the shaping of the T-cell repertoire.
Nitric oxide-induced p53 accumulation and regulation of inducible nitric oxide synthase expression by wild-type p53.
Authors: Forrester K , Ambs S , Lupold S E , Kapust R B , Spillare E A , Weinberg W C , Felley-Bosco E , Wang X W , Geller D A , Tzeng E , Billiar T R , Harris C C
Published: July 2002

The tumor suppressor gene product p53 plays an important role in the cellular response to DNA damage from exogenous chemical and physical mutagens. Therefore, we hypothesized that p53 performs a similar role in response to putative endogenous mutagens, such as nitric oxide (NO). We report here that exposure of human cells to NO generated from an NO donor or from overexpression of inducible nitric oxide synthase (NOS2) results in p53 protein accumulation. In addition, expression of wild-type (WT) p53 in a variety of human tumor cell lines, as well as murine fibroblasts, results in down-regulation of NOS2 expression through inhibition of the NOS2 promoter. These data are consistent with the hypothesis of a negative feedback loop in which endogenous NO-induced DNA damage results in WT p53 accumulation and provides a novel mechanism by which p53 safeguards against DNA damage through p53-mediated transrepression of NOS2 gene expression, thus reducing the potential for NO-induced DNA damage.
Cultural universals: Measuring the semantic structure of emotion terms in English and Japanese
Authors: Romney A. Kimball , Moore Carmella C. , Rusch Craig D.
Published: July 2002

Research is presented on the semantic structure of 15 emotion terms as measured by judged-similarity tasks for monolingual English-speaking and monolingual and bilingual Japanese subjects. A major question is the relative explanatory power of a single shared model for English and Japanese versus culture-specific models for each language. The data support a shared model for the semantic structure of emotion terms even though some robust and significant differences are found between English and Japanese structures. The Japanese bilingual subjects use a model more like English when performing tasks in English than when performing the same task in Japanese.
Two sterol regulatory element-like sequences mediate up-regulation of caveolin gene transcription in response to low density lipoprotein free cholesterol
Authors: Bist Anita , Fielding Phoebe E. , Fielding Christopher J.
Published: July 2002

Caveolae form the terminus for a major pathway of intracellular free cholesterol (FC) transport. Caveolin mRNA levels in confluent human skin fibroblasts were up-regulated following increased uptake of low density lipoprotein (LDL) FC. The increase induced by FC was not associated with detectable change in mRNA stability, indicating that caveolin mRNA levels were mediated at the level of gene transcription. A total of 924 bp of 5′ flanking region of the caveolin gene were cloned and sequenced. The promoter sequence included three G+C-rich potential sterol regulatory elements (SREs), a CAAT sequence and a Sp1 consensus sequence. Deletional mutagenesis of individual SRE-like sequences indicated that of these two (at −646 and −395 bp) were essential for the increased transcription rates mediated by LDL-FC, whereas the third was inconsequential. Gel shift analysis of protein binding from nuclear extracts to these caveolin promoter DNA sequences, together with DNase I footprinting, confirmed nucleoprotein binding to the SRE-like elements as part of the transcriptional response to LDL-FC. A supershift obtained with antibody to SRE-binding protein 1 (SPEBP-1) indicated that this protein binds at −395 bp. There was no reaction at −395 bp with anti-Sp1 antibody nor with either antibody at −646 bp. The cysteine protease inhibitor
N
-acetyl-leu-leu-norleucinal (ALLN), which inhibits SREBP catabolism, superinhibited caveolin mRNA levels regardless of LDL-FC. This finding suggests that SREBP inhibits caveolin gene transcription in contrast to its stimulating effect on other promoters. The findings of this study are consistent with the postulated role for caveolin as a regulator of cellular FC homeostasis in quiescent peripheral cells, and the coordinate regulation by SREBP of FC influx and efflux.
Enhancement of DNA repair in human skin cells by thymidine dinucleotides: Evidence for a p53-mediated mammalian SOS response
Authors: Eller Mark S. , Maeda Tomoko , Magnoni Cristina , Atwal Diana , Gilchrest Barbara A.
Published: July 2002

Thymidine dinucleotide (pTpT) stimulates melanogenesis in mammalian pigment cells and intact skin, mimicking the effects of UV irradiation and UV-mimetic DNA damage. Here it is shown that, in addition to tanning, pTpT induces a second photoprotective response, enhanced repair of UV-induced DNA damage. This enhanced repair results in a 2-fold increase in expression of a UV-damaged chloramphenicol acetyltransferase expression vector transfected into pTpT-treated skin fibroblasts and keratinocytes, compared with diluent-treated cells. Direct measurement of thymine dimers and (6–4) photoproducts by immunoassay demonstrates faster repair of both of these UV-induced photoproducts in pTpT-treated fibroblasts. This enhanced repair capacity also improves cell survival and colony-forming ability after irradiation. These effects of pTpT are accomplished, at least in part, by the up-regulation of a set of genes involved in DNA repair (
ERCC3
and
GADD45
) and cell cycle inhibition (
SDI1
). At least two of these genes (
GADD45
and
SDI1
) are known to be transcriptionally regulated by the p53 tumor suppressor protein. Here we show that pTpT activates p53, leading to nuclear accumulation of this protein, and also increases the specific binding of this transcription factor to its DNA consensus sequence.
Shuttling of initiating kinase between discrete aggregates of the high affinity receptor for IgE regulates the cellular response
Authors: Torigoe Chikako , Goldstein Byron , Wofsy Carla , Metzger Henry
Published: July 2002

Using defined oligomers of IgE, our group previously studied the quantitative relationship between the aggregation of the high affinity receptors for IgE (FcɛRI) and the earliest signals initiated by such aggregation: the phosphorylation of tyrosines on the receptor. Notably, at certain doses of the oligomers such phosphorylation reached a plateau level well before the aggregation of the receptors had reached a maximum. These findings and others led us to propose that aggregates of the receptor were competing for a limited amount of the critical kinase—thought to be Lyn in this system. This paper describes a test of this proposal. We incubated cells with two distinguishable IgEs and examined the effect of aggregating one or the other or both types on the phosphorylation. When receptors binding antigen-specific IgE were aggregated with polyvalent antigen, they became rapidly phosphorylated as expected. Remarkably, however, FcɛRI that had already been phosphorylated by the binding of dimers of IgE, became dephosphorylated simultaneously. Furthermore, when the antigen-driven aggregates were dissociated with hapten, the phosphorylation pattern reverted to that seen prior to the addition of antigen: as the antigen-driven aggregates became dephosphorylated, the receptors stably aggregated by the bound oligomers became rapidly rephosphorylated. Dephosphorylation of oligomer-driven aggregates was also partially reversed during the “spontaneous” dephosphorylation of the antigen-driven receptors seen at longer times after addition of antigen. Thus signal transduction in this system is in part regulated by the shuttling of limited amounts of the kinase that initiates the cascade of phosphorylations.
Quorum sensing in
Escherichia coli
and
Salmonella typhimurium
Authors: Surette Michael G. , Bassler Bonnie L.
Published: July 2002

Escherichia coli
and
Salmonella typhimurium
strains grown in Luria–Bertani medium containing glucose secrete a small soluble heat labile organic molecule that is involved in intercellular communication. The factor is not produced when the strains are grown in Luria–Bertani medium in the absence of glucose. Maximal secretion of the substance occurs in midexponential phase, and the extracellular activity is degraded as the glucose is depleted from the medium or by the onset of stationary phase. Destruction of the signaling molecule in stationary phase indicates that, in contrast to other quorum-sensing systems, quorum sensing in
E. coli
and
S. typhimurium
is critical for regulating behavior in the prestationary phase of growth. Our results further suggest that the signaling factor produced by
E. coli
and
S. typhimurium
is used to communicate both the cell density and the metabolic potential of the environment. Several laboratory and clinical strains of
E. coli
and
S. typhimurium
were screened for production of the signaling molecule, and most strains make it under conditions similar to those shown here for
E. coli
AB1157 and
S. typhimurium
LT2. However, we also show that
E. coli
strain DH5α does not make the soluble factor, indicating that this highly domesticated strain has lost the gene(s) or biosynthetic machinery necessary to produce the signaling substance. Implications for the involvement of quorum sensing in pathogenesis are discussed.