bluuebunny/crossref_metadata_2025 huggingface dataset:
The transition of a multipactor to a low-pressure gas discharge
Authors: Höhn F. , Jacob W. , Beckmann R. , Wilhelm R.
Published: July 2002

Multipactor discharges can cause severe problems in high voltage rf systems like rf antennae or transmission lines of ion cyclotron resonance heating (ICRH) in nuclear fusion devices, where they may initiate gas breakdown. To study this eventual transition from a starting multipactor into an ordinary rf discharge detailed investigations were performed using a parallel plate geometry, 50 MHz operating frequency and up to one kilovolt rf amplitude. Measurements of electric data (rf amplitude, absorbed and reflected power, discharge current), electronic parameters (electron current density and energy distribution) and light emission were used for characterization. As a main result a new type of well defined discharge regime was identified, which seems important for the transition from multipactor into gas breakdown in rf devices.
Plasma screening effects on photoionizations in weakly coupled plasmas
Authors: Jung Young-Dae
Published: July 2002

Plasma screening effects on photoionizations from the 1s state of hydrogenic ions in dense weakly plasmas are investigated. The particle interaction potential in weakly coupled plasmas is obtained by the static Debye-Hückel model. The initial bound wave function and energy eigenvalue of the target ion are modified in the Debye-Hückel potential using the Ritz variation method. The final state of the ejected photoelectron is represented by a plane wave solution. The Coulomb correction is considered using the screened Coulomb wave function. The photoionization cross section is obtained the acceleration form of the matrix element in order to investigate the plasma screening effects on the interaction potential. The screening effect is obtained as a function of the Debye length and photon energy. The retardation correction effect is also considered in obtaining the total 1s photoionization cross section in plasmas. The plasma screening effects on the photoionization cross section for the interesting domain of the Debye length, Λ⩾10aZ, are found to be less than 10%. It is also found that the plasma screening effect is almost independent of the incident photon energy.
Highly damage resistant, broadband, hard antireflection coating for high power lasers in the ultraviolet to near-infrared wavelength regions
Authors: Yoshida K. , Yoshida H. , Kato Y. , Yamanaka C.
Published: July 2002

Mechanically hard and broadband gradient refractive index antireflection coating was developed. It has a high damage threshold of ≳6 J/cm2 at 355 nm and 12–13 J/cm2 in the visible to near-infrared region. It will be applicable to high power pulsed lasers as well as to industrial uses.
Strengthened solid-state laser materials
Authors: Marion J.
Published: July 2002

The tensile fracture strength of crystalline materials for high average power lasers has been increased by a factor of 15 using deep chemical polishing. Samples of gadolinium scandium gallium garnet, gadolinium gallium garnet, and yttrium aluminum garnet, which were prepared by conventional mechanical techniques to a high quality polish, were found to contain subsurface damage up to 50 μm in depth. When this damage was removed by deep chemical etching, the mean strength of small, four-point flexure specimens increased from 155 to 2280 MPa; however, these samples were no longer optically flat after etching. Specimens in which the optical figure was restored by polishing after the etch had an intermediate strength of 630 MPa.
Adhesion measurement of thin films by indentation
Authors: Matthewson M. J.
Published: July 2002

An indentation technique is described for measuring the shear strength of the interface between a thin film and a rigid substrate. A simple elastic/plastic analysis is used to describe the experimental results and good agreement between the two is found. The method may also be used to estimate the interfacial toughness so that the important parameters characterizing both initiation and propagation of adhesive failure may be determined from one simple experiment. The analysis is extended to describe the effect of residual stress in the film. Also, the stresses around a pinhole defect in a stressed film are examined.
Layer-dependent laser sputtering of BaF2 (111)
Authors: Reif J. , Fallgren H. , Nielsen H. B. , Matthias E.
Published: July 2002

Laser-induced sputtering from the (111) surface of BaF2 was investigated under ultrahigh vacuum conditions, applying fluences well below the macroscopic damage threshold. Measurement of the wavelength-dependent desorption of Ba+ indicates that Ba+ is emitted from two chemically different surroundings at the surface. For a fixed wavelength, the emission rates of Ba+ and F+ as functions of time show a distinct anticorrelation, confirming the existence of two different chemical states of the surface, and suggesting that the sputtering takes place layer by layer.
Wavelength dependence of laser-induced sputtering from the (111) surface of BaF2
Authors: Reif J. , Fallgren H. , Cooke W. E. , Matthias E.
Published: July 2002

Using blue tunable pulse laser radiation of low fluence, we have investigated laser-induced sputtering from cleaved BaF2 (111) surfaces under ultrahigh vacuum conditions. Time correlated with the laser pulses the positive ions Ba+, Ba++, (BaF)+ and F+ were observed. Practically no negative ions were found. Neutral atomic fluorine (F 0) was desorbed abundantly. A pulse correlation of F 0 as well as the relative amount of F 0 and F+ could not be established at this stage. The emission yield of all positive ions as well as of F 0 was strongly wavelength dependent and showed a broad resonance around 2.9 eV.
Gated diode leakage and lifetime measurements of misfit dislocation gettered Si epitaxy
Authors: Salih Ali S. M. , Radzimski Z. , Honeycutt J. , Rozgonyi G. A. , Bean K. E. , Lindberg K.
Published: July 2002

Gated diode leakage current and minority-carrier lifetime are compared between Si wafers extrinsically gettered with epitaxial misfit dislocations and reference homoepitaxial material. The stability and gettering efficiency of the interfacial misfit dislocations have been verified by measuring leakage currents of less than 1 nA/cm2 for both gate depletion and accumulation for a large number of diodes. In either mode, the gated diodes with misfit dislocation gettering exhibited more than an order of magnitude lower leakage current than that produced by standard epi without misfit dislocations. In addition, minority-carrier generation lifetimes greater than 2 ms were typical of material extrinsically gettered via misfit dislocations, while reference epi was two to three times lower. The lifetme was found to be uniform in the near-surface region, but was drastically reduced in the immediate vicinity of the misfit locations, indicating that the defects may provide useful options in high-speed devices, latch-up control, and radiation hard devices.
Bistability and switching in nonlinear prism coupling
Authors: Stegeman G. I. , Assanto G. , Zanoni R. , Seaton C. T. , Garmire E. , Maradudin A. A. , Reinisch R. , Vitrant G.
Published: July 2002

We demonstrate that when a nonlinear coupler is operated in the switching regime, small amounts of either nonlocality in the optically induced refractive index change or of longitudinal feedback can lead to optical bistability. Outside the switching regime, there is a threshold for the amount of nonlocality or feedback required for bistability. The diverse predictions of previous theoretical formulations are therefore reconciled.
The capsular polysaccharide of
Enterococcus faecalis
and its relationship to other polysaccharides in the cell wall
Authors: Hancock Lynn E. , Gilmore Michael S.
Published: July 2002

With the goal of identifying and characterizing traits of
Enterococcus faecalis
that play key roles in human disease, we identified an operon specifying synthesis of a capsular carbohydrate of the type most commonly expressed by clinical isolates. This surface-exposed carbohydrate consists of glycerol phosphate, glucose, and galactose residues, and its biosynthesis is encoded by a determinant that includes 11 ORFs. Insertional inactivation of genes in this pathway yielded mutants with enhanced susceptibility to phagocytic killing
in vitro
and compromised in the ability to persist in regional lymph nodes
in vivo
.
Requirement for natural killer T (NKT) cells in the induction of allograft tolerance
Authors: Seino Ken-ichiro , Fukao Katashi , Muramoto Kenzo , Yanagisawa Kazuhiko , Takada Yasutsugu , Kakuta Shigeru , Iwakura Yoichiro , Van Kaer Luc , Takeda Kazuyoshi , Nakayama Toshinori , Taniguchi Masaru , Bashuda Hisashi , Yagita Hideo , Okumura Ko
Published: July 2002

In this study, we investigated the role of Vα14 natural killer T (NKT) cells in transplant immunity. The ability to reject allografts was not significantly different between wild-type (WT) and Vα14 NKT cell-deficient mice. However, in models in which tolerance was induced against cardiac allografts by blockade of lymphocyte function-associated antigen-1/intercellular adhesion molecule-1 or CD28/B7 interactions, long-term acceptance of the grafts was observed only in WT but not Vα14 NKT cell-deficient mice. Adoptive transfer with Vα14 NKT cells restored long-term acceptance of allografts in Vα14 NKT cell-deficient mice. The critical role of Vα14 NKT cells to mediate immunosuppression was also observedin vitroin mixed lymphocyte cultures in which lymphocyte function-associated antigen-1/intercellular adhesion molecule-1 or CD28/B7 interactions were blocked. Experiments using IL-4- or IFN-γ-deficient mice suggested a critical contribution of IFN-γ to the Vα14 NKT cell-mediated allograft acceptancein vivo. These results indicate a critical contribution of Vα14 NKT cells to the induction of allograft tolerance and provide a useful model to investigate the regulatory role of Vα14 NKT cells in various immune responses.
α10: A determinant of nicotinic cholinergic receptor function in mammalian vestibular and cochlear mechanosensory hair cells
Authors: Elgoyhen A. Belén , Vetter Douglas E. , Katz Eleonora , Rothlin Carla V. , Heinemann Stephen F. , Boulter Jim
Published: July 2002

We report the cloning and characterization of rat α10, a
previously unidentified member of the nicotinic acetylcholine receptor
(nAChR) subunit gene family. The protein encoded by the α10 nAChR
subunit gene is most similar to the rat α9 nAChR, and both α9 and
α10 subunit genes are transcribed in adult rat mechanosensory hair
cells. Injection of
Xenopus laevis
oocytes with α10 cRNA alone or in pairwise combinations with either
α2-α6 or β2-β4 subunit cRNAs yielded no detectable ACh-gated
currents. However, coinjection of α9 and α10 cRNAs resulted in the
appearance of an unusual nAChR subtype. Compared with homomeric α9
channels, the α9α10 nAChR subtype displays faster and more
extensive agonist-mediated desensitization, a distinct current–voltage
relationship, and a biphasic response to changes in extracellular
Ca
2+
ions. The pharmacological profiles of homomeric α9
and heteromeric α9α10 nAChRs are essentially indistinguishable and
closely resemble those reported for endogenous cholinergic
eceptors found in vertebrate hair cells. Our data suggest that
efferent modulation of hair cell function occurs, at least in part,
through heteromeric nAChRs assembled from both α9 and α10 subunits.
Noninvasive functional optical spectroscopy of human breast tissue
Authors: Shah Natasha , Cerussi Albert , Eker Charlotta , Espinoza Jenny , Butler John , Fishkin Joshua , Hornung Rene , Tromberg Bruce
Published: July 2002

Near infrared diffuse optical spectroscopy and diffuse optical
imaging are promising methods that eventually may enhance or replace
existing technologies for breast cancer screening and diagnosis. These
techniques are based on highly sensitive, quantitative measurements of
optical and functional contrast between healthy and diseased tissue. In
this study, we examine whether changes in breast physiology caused by
exogenous hormones, aging, and fluctuations during the menstrual cycle
result in significant alterations in breast tissue optical contrast. A
noninvasive quantitative diffuse optical spectroscopy technique,
frequency-domain photon migration, was used. Measurements were
performed on 14 volunteer subjects by using a hand-held probe.
Intrinsic tissue absorption and reduced scattering parameters were
calculated from frequency-domain photon migration data.
Wavelength-dependent absorption (at 674, 803, 849, and 956 nm) was used
to determine tissue concentration of oxyhemoglobin, deoxyhemoglobin,
total hemoglobin, tissue hemoglobin oxygen saturation, and bulk water
content. Results show significant and dramatic differences in optical
properties between menopausal states. Average premenopausal intrinsic
tissue absorption and reduced scattering values at each wavelength are
2.5- to 3-fold higher and 16–28% greater, respectively, than
absorption and scattering for postmenopausal subjects. Absorption and
scattering properties for women using hormone replacement therapy are
intermediate between premenopausal and postmenopausal populations.
Physiological properties show differences in mean total hemoglobin (7.0
μM, 11.8 μM, and 19.2 μM) and water concentration relative to
pure water (10.9%, 15.3%, and 27.3%) for postmenopausal, hormone
replacement therapy, and premenopausal subjects, respectively. Because
of their unique, quantitative information content, diffuse optical
methods may play an important role in breast diagnostics and improving
our understanding of breast disease.
Hydrogen peroxide mediates the cell growth and transformation caused by the mitogenic oxidase Nox1
Authors: Arnold Rebecca S. , Shi Jing , Murad Emma , Whalen Anne M. , Sun Carrie Q. , Polavarapu Rathnagiri , Parthasarathy Sampath , Petros John A. , Lambeth J. David
Published: July 2002

Nox1, a homologue of gp91
phox
, the catalytic
moiety of the superoxide (O

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)-generating NADPH
oxidase of phagocytes, causes increased O

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generation, increased mitotic rate, cell transformation, and
tumorigenicity when expressed in NIH 3T3 fibroblasts. This study
explores the role of reactive oxygen species (ROS) in regulating cell
growth and transformation by Nox1. H
2
O
2
concentration increased ≈10-fold in Nox1-expressing cells, compared
with <2-fold increase in O

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. When human catalase was
expressed in Nox1-expressing cells, H
2
O
2
concentration decreased, and the cells reverted to a normal appearance,
the growth rate normalized, and cells no longer produced tumors in
athymic mice. A large number of genes, including many related to cell
cycle, growth, and cancer (but unrelated to oxidative stress), were
expressed in Nox1-expressing cells, and more than 60% of these
returned to normal levels on coexpression of catalase. Thus,
H
2
O
2
in low concentrations functions as an
intracellular signal that triggers a genetic program related to cell
growth.
An endogenous capsaicin-like substance with high potency at recombinant and native vanilloid VR1 receptors
Authors: Huang Susan M. , Bisogno Tiziana , Trevisani Marcello , Al-Hayani Abdulmonem , De Petrocellis Luciano , Fezza Filomena , Tognetto Michele , Petros Timothy J. , Krey Jocelyn F. , Chu Constance J. , Miller Jeffrey D. , Davies Stephen N. , Geppetti Pierangelo , Walker J. Michael , Di Marzo Vincenzo
Published: July 2002

The vanilloid receptor VR1 is a nonselective cation channel that is most abundant in peripheral sensory fibers but also is found in several brain nuclei. VR1 is gated by protons, heat, and the pungent ingredient of “hot” chili peppers, capsaicin. To date, no endogenous compound with potency at this receptor comparable to that of capsaicin has been identified. Here we examined the hypothesis, based on previous structure-activity relationship studies and the availability of biosynthetic precursors, that
N
-arachidonoyl-dopamine (NADA) is an endogenous “capsaicin-like” substance in mammalian nervous tissues. We found that NADA occurs in nervous tissues, with the highest concentrations being found in the striatum, hippocampus, and cerebellum and the lowest concentrations in the dorsal root ganglion. We also gained evidence for the existence of two possible routes for NADA biosynthesis and mechanisms for its inactivation in rat brain. NADA activates both human and rat VR1 overexpressed in human embryonic kidney (HEK)293 cells, with potency (EC
50
≈ 50 nM) and efficacy similar to those of capsaicin. Furthermore, NADA potently activates native vanilloid receptors in neurons from rat dorsal root ganglion and hippocampus, thereby inducing the release of substance P and calcitonin gene-related peptide (CGRP) from dorsal spinal cord slices and enhancing hippocampal paired-pulse depression, respectively. Intradermal NADA also induces VR1-mediated thermal hyperalgesia (EC
50
= 1.5 ± 0.3 μg). Our data demonstrate the existence of a brain substance similar to capsaicin not only with respect to its chemical structure but also to its potency at VR1 receptors.
Mechanism of DNA polymerase II-mediated frameshift mutagenesis
Authors: Becherel Olivier J. , Fuchs Robert P. P.
Published: July 2002

Escherichia coli
possesses three SOS-inducible DNA polymerases (Pol II, IV, and V) that were recently found to participate in translesion synthesis and mutagenesis. Involvement of these polymerases appears to depend on the nature of the lesion and its local sequence context, as illustrated by the bypass of a single
N-
2-acetylaminofluorene adduct within the
NarI
mutation hot spot. Indeed, error-free bypass requires Pol V (
umuDC
), whereas mutagenic (−2 frameshift) bypass depends on Pol II (
polB
). In this paper, we show that purified DNA Pol II is able
in vitro
to generate the −2 frameshift bypass product observed
in vivo
at the
NarI
sites. Although the Δ
polB
strain is completely defective in this mutation pathway, introduction of the
polB
gene on a low copy number plasmid restores the −2 frameshift pathway. In fact, modification of the relative copy number of
polB
versus
umuDC
genes results in a corresponding modification in the use of the frameshift versus error-free translesion pathways, suggesting a direct competition between Pol II and V for the bypass of the same lesion. Whether such a polymerase competition model for translesion synthesis will prove to be generally applicable remains to be confirmed.
Metabolic engineering of essential oil yield and composition in mint by altering expression of deoxyxylulose phosphate reductoisomerase and menthofuran synthase
Authors: Mahmoud Soheil S. , Croteau Rodney B.
Published: July 2002

Peppermint (
Mentha
×
piperita
L.) was independently transformed with a homologous sense version of the 1-deoxy-
d
-xylulose-5-phosphate reductoisomerase cDNA and with a homologous antisense version of the menthofuran synthase cDNA, both driven by the CaMV 35S promoter. Two groups of transgenic plants were regenerated in the reductoisomerase experiments, one of which remained normal in appearance and development; another was deficient in chlorophyll production and grew slowly. Transgenic plants of normal appearance and growth habit expressed the reductoisomerase transgene strongly and constitutively, as determined by RNA blot analysis and direct enzyme assay, and these plants accumulated substantially more essential oil (about 50% yield increase) without change in monoterpene composition compared with wild-type. Chlorophyll-deficient plants did not afford detectable reductoisomerase mRNA or enzyme activity and yielded less essential oil than did wild-type plants, indicating cosuppression of the reductoisomerase gene. Plants transformed with the antisense version of the menthofuran synthase cDNA were normal in appearance but produced less than half of this undesirable monoterpene oil component than did wild-type mint grown under unstressed or stressed conditions. These experiments demonstrate that essential oil quantity and quality can be regulated by metabolic engineering. Thus, alteration of the committed step of the mevalonate-independent pathway for supply of terpenoid precursors improves flux through the pathway that leads to increased monoterpene production, and antisense manipulation of a selected downstream monoterpene biosynthetic step leads to improved oil composition.
A zinc-sensing receptor triggers the release of intracellular Ca
2+
and regulates ion transport
Authors: Hershfinkel Michal , Moran Arie , Grossman Nili , Sekler Israel
Published: July 2002

Changes in extracellular zinc concentration participate in
modulating fundamental cellular processes such as proliferation,
secretion, and ion transport in a mechanism that is not well
understood. Here, we show that a micromolar concentration of
extracellular zinc triggers a massive release of calcium from
thapsigargin-sensitive intracellular pools in the colonocytic cell line
HT29. Calcium release was blocked by a phospholipase-C inhibitor,
indicating that formation of inositol 1,4,5-triphosphate is required
for zinc-dependent calcium release. Zinc influx was not observed,
indicating that extracellular zinc triggered the release. The
Ca
i
2+
release was zinc specific and could not
be triggered by other heavy metals. Furthermore, zinc failed to
activate the Ca
2+
-sensing receptor heterologously expressed
in HEK293 cells. The zinc-induced Ca
i
2+
rise
stimulated the activity of the Na
+
/H
+
exchanger in HT29 cells. Our results indicate that a previously
uncharacterized extracellular, G protein-coupled,
Zn
2+
-sensing receptor is functional in colonocytes. Because
Ca
i
2+
rise is known to regulate key cellular
and signal-transduction processes, the zinc-sensing receptor may
provide the missing link between extracellular zinc concentration
changes and the regulation of cellular processes.
Increased levels of forkhead box M1B transcription factor in transgenic mouse hepatocytes prevent age-related proliferation defects in regenerating liver
Authors: Wang Xinhe , Quail Elizabeth , Hung Nai-Jung , Tan Yongjun , Ye Honggang , Costa Robert H.
Published: July 2002

The forkhead box (Fox) family of transcription factors share
homology in the winged helix/forkhead DNA-binding domain and
play important roles in regulating cellular proliferation,
differentiation, longevity, and cellular transformation. Forkhead box
M1B (FoxM1B) is a ubiquitously expressed member of the Fox
transcription factor family whose expression is restricted to
proliferating cells and that mediates hepatocyte entry into DNA
synthesis and mitosis during liver regeneration. Recent cDNA microarray
studies indicated that age-related defects in cellular proliferation
are associated with diminished expression of the FoxM1B transcription
factor. Here, we show that increased levels of FoxM1B in regenerating
liver of old transgenic mice restore the sharp peaks in hepatocyte DNA
replication and mitosis that are the hallmarks of young regenerating
mouse liver. Restoration of the young regenerating liver phenotype is
associated with increased expression of numerous cell cycle regulatory
genes that include cyclin D1, cyclin A2, cyclin F, cyclin B1, cyclin
B2, Cdc25B, and p55cdc. Cotransfection assays in the human hepatoma
HepG2 cell line demonstrated that FoxM1B protein stimulated expression
of both the cyclin B1 and cyclin D1 promoters, suggesting that these
cyclin genes are a direct FoxM1B transcriptional target. These results
suggest that FoxM1B controls the transcriptional network of genes that
are essential for cell division and exit from mitosis. Our results
indicate that reduced expression of the FoxM1B transcription factor
contributes to the decline in cellular proliferation observed in the
aging process.
CD26-mediated signaling for T cell activation occurs in lipid rafts through its association with CD45RO
Authors: Ishii Tomonori , Ohnuma Kei , Murakami Akikazu , Takasawa Naruhiko , Kobayashi Seiji , Dang Nam H. , Schlossman Stuart F. , Morimoto Chikao
Published: July 2002

CD26 is a T cell activation antigen that contains dipeptidyl peptidase IV activity and is known to bind adenosine deaminase. The mechanism by which CD26 costimulation potentiates T cell receptor-mediated T cell activation, leading to subsequent exertion of T cell effector function, is still not clearly defined. In this article, we demonstrate that CD26 localizes into lipid rafts, and targeting of CD26 to rafts is necessary for signaling events through CD26. Importantly, aggregation of CD26 by anti-CD26 mAb crosslinking also causes coaggregation of CD45 into rafts. Moreover, we show that CD26 directly binds to the cytoplasmic domain of CD45. Our results therefore indicate a mechanism whereby CD26 engagement promotes aggregation of lipid rafts and facilitates colocalization of CD45 to T cell receptor signaling molecules p56Lck, ZAP-70, and TCRζ, thereby enhancing protein tyrosine phosphorylation of various signaling molecules and subsequent interleukin-2 production.
Signal interactions between nitric oxide and reactive oxygen intermediates in the plant hypersensitive disease resistance response
Authors: Delledonne Massimo , Zeier Jürgen , Marocco Adriano , Lamb Chris
Published: July 2002

Nitric oxide (NO) and reactive oxygen intermediates (ROIs) play key roles in the activation of disease resistance mechanisms both in animals and plants. In animals NO cooperates with ROIs to kill tumor cells and for macrophage killing of bacteria. Such cytotoxic events occur because unregulated NO levels drive a diffusion-limited reaction with O
2
−
to generate peroxynitrite (ONOO
−
), a mediator of cellular injury in many biological systems. Here we show that in soybean cells unregulated NO production at the onset of a pathogen-induced hypersensitive response (HR) is not sufficient to activate hypersensitive cell death. The HR is triggered only by balanced production of NO and ROIs. Moreover, hypersensitive cell death is activated after interaction of NO not with O
2
−
but with H
2
O
2
generated from O
2
−
by superoxide dismutase. Increasing the level of O
2
−
reduces NO-mediated toxicity, and ONOO
−
is not a mediator of hypersensitive cell death. During the HR, superoxide dismutase accelerates O
2
−
dismutation to H
2
O
2
to minimize the loss of NO by reaction with O
2
−
and to trigger hypersensitive cell death through NO/H
2
O
2
cooperation. However, O
2
−
rather than H
2
O
2
is the primary ROI signal for pathogen induction of glutathione
S
-transferase, and the rates of production and dismutation of O
2
−
generated during the oxidative burst play a crucial role in the modulation and integration of NO/H
2
O
2
signaling in the HR. Thus although plants and animals use a similar repertoire of signals in disease resistance, ROIs and NO are deployed in strikingly different ways to trigger host cell death.
Generation of the mu opioid receptor (MOR-1) protein by three new splice variants of the
Oprm
gene
Authors: Pan Ying-Xian , Xu Jin , Mahurter Loriann , Bolan Elizabeth , Xu Mingming , Pasternak Gavril W.
Published: July 2002

Using 5′ RACE, we have isolated four additional exons of the mu opioid receptor gene (
Oprm
), resulting in a gene spanning over 250 kb. The four new exons are contained within eight additional splice variants containing exon 11 at the 5′ terminus. Exon 11, which is under the control of a previously unknown upstream promoter, and exon 12 are located ≈10 kb and ≈8 kb upstream from exon 1, respectively. Exon 13 and 14 are located between exons 1 and 2. The regional distributions of the variants, as determined by reverse transcription-PCR, varied among themselves and were distinct from that of MOR-1, implying region-specific RNA processing. Three variants (MOR-1H, MOR-1I, and MOR-1J) contained two potential translational start points, with the translational start point in exon 1 producing proteins identical to the original MOR-1 protein. When expressed, the receptor binding of these three variants was indistinguishable from that of MOR-1. The remaining eight proteins using the translation start point in exon 11 were all truncated, with three (MOR-1G, MOR-1M, and MOR-1N) predicting proteins of only six transmembrane domains and the rest giving proteins under 10 kDa. Western blots with an exon 11-specific antiserum revealed bands consistent with the six transmembrane domain proteins within the brain, but the shorter proteins were not detected. Thus, the MOR-1 protein can be generated by four different splice variants of the
Oprm
gene under the control of two physically distinct promoters. Although the truncated proteins are expressed in brain with a unique regional distribution, their functional significance remains unknown.
CD5 expression by B lymphocytes and its regulation upon Epstein–Barr virus transformation
Authors: Kaplan David , Smith Dawn , Meyerson Howard , Pecora Nicole , Lewandowska Kristine
Published: July 2002

Dim expression of CD5 on human B lymphocytes has been used to delineate B1 and B2 subsets. Nevertheless, others have suggested that the molecule is an activation marker and does not predicate a subset distinction. We have used enzymatic amplification staining, a technology that enhances the resolution of flow cytometric analysis of cell surface molecules by as much as 100-fold, to determine that essentially all human B cells express CD5. Furthermore, we show that this expression is regulated during Epstein–Barr virus transformation.
Cubilin dysfunction causes abnormal metabolism of the steroid hormone 25(OH) vitamin D
3
Authors: Nykjaer Anders , Fyfe John C. , Kozyraki Renata , Leheste Jörg-Robert , Jacobsen Christian , Nielsen Morten S. , Verroust Pierre J. , Aminoff Maria , de la Chapelle Albert , Moestrup Søren K. , Ray Rahul , Gliemann Jørgen , Willnow Thomas E. , Christensen Erik I.
Published: July 2002

Steroid hormones are central regulators of a variety of biological processes. According to the free hormone hypothesis, steroids enter target cells by passive diffusion. However, recently we demonstrated that 25(OH) vitamin D
3
complexed to its plasma carrier, the vitamin D-binding protein, enters renal proximal tubules by receptor-mediated endocytosis. Knockout mice lacking the endocytic receptor megalin lose 25(OH) vitamin D
3
in the urine and develop bone disease. Here, we report that cubilin, a membrane-associated protein colocalizing with megalin, facilitates the endocytic process by sequestering steroid–carrier complexes on the cellular surface before megalin-mediated internalization of the cubilin-bound ligand. Dogs with an inherited disorder affecting cubilin biosynthesis exhibit abnormal vitamin D metabolism. Similarly, human patients with mutations causing cubilin dysfunction exhibit urinary excretion of 25(OH) vitamin D
3
. This observation identifies spontaneous mutations in an endocytic receptor pathway affecting cellular uptake and metabolism of a steroid hormone.
Interocular transfer in perceptual learning of a pop-out discrimination task.
Authors: Schoups A A , Orban G A
Published: July 2002

The specificity of the improvement in perceptual learning is often used to localize the neuronal changes underlying this type of adult plasticity. We investigated a visual texture discrimination task previously reported to be accomplished preattentively and for which learning-related changes were inferred to occur at a very early level of the visual processing stream. The stimulus was a matrix of lines from which a target popped out, due to an orientation difference between the three target lines and the background lines. The task was to report the global orientation of the target and was performed monocularly. The subjects' performance improved dramatically with training over the course of 2-3 weeks, after which we tested the specificity of the improvement for the eye trained. In all subjects tested, there was complete interocular transfer of the learning effect. The neuronal correlate of this learning are therefore most likely localized in a visual area where input from the two eyes has come together.
Characterization of GMP-17, a granule membrane protein that moves to the plasma membrane of natural killer cells following target cell recognition.
Authors: Medley Q G , Kedersha N , O'Brien S , Tian Q , Schlossman S F , Streuli M , Anderson P
Published: July 2002

Cytotoxic lymphocytes are characterized by their inclusion of cytoplasmic granules that fuse with the plasma membrane following target cell recognition. We previously identified a cytotoxic granule membrane protein designated p15-TIA-1 that is immunochemically related to an RNA-recognition motif (RRM)-type RNA-binding protein designated p40-TIA-1. Although it was suggested that p15-TIA-1 might be derived from p40-T1A-1 by proteolysis, N-terminal amino acid sequencing of p15-TIA-1 immunoaffinity purified from a natural killer (NK) cell line by using monoclonal antibody (mAb) 2G9 revealed that p15-T1A-1 is identical to the deduced amino acid sequence of NKG7 and GIG-1, cDNAs isolated from NK cells and granulocyte-colony-stimulating factor-treated mononuclear cells, respectively. Epitope mapping revealed that mAb 2G9 recognizes the C terminus of p15-T1A-1 and p40-T1A-1. The deduced amino acid sequence of p15-T1A-1/NKG7/GIG-1 predicts that the protein possesses four transmembrane domains, and immuno-electron microscopy localizes the endogenous protein to the membranes of cytotoxic granules in NK cells. Given its subcellular localization, we propose to rename-this protein GMP-17, for granule membrane protein of 17 kDa. Immunofluorescence microscopy of freshly isolated NK cells confirms this granular localization. Target cell-induced NK cell degranulation results in translocation of GMP-17 from granules to the plasma membrane, suggesting a possible role for GMP-17 in regulating the effector function of lymphocytes and neutrophils.
Alphavirus-based expression vectors: strategies and applications.
Authors: Frolov I , Hoffman T A , Prágai B M , Dryga S A , Huang H V , Schlesinger S , Rice C M
Published: July 2002

Alphaviruses are positive-strand RNA viruses that can mediate efficient cytoplasmic gene expression in insect and vertebrate cells. Through recombinant DNA technology, the alphavirus RNA replication machinery has been engineered for high-level expression of heterologous RNAs and proteins. Amplification of replication-competent alpha-virus RNAs (replicons) can be initiated by RNA or DNA transfection and a variety of packaging systems have been developed for producing high titers of infectious viral particles. Although normally cytocidal for vertebrate cells, variants with adaptive mutations allowing noncytopathic replication have been isolated from persistently infected cultures or selected using a dominant selectable marker. Such mutations have been mapped and used to create new alphavirus vectors for noncytopathic gene expression in mammalian cells. These vectors allow long-term expression at moderate levels and complement previous vectors designed for short-term high-level expression. Besides their use for a growing number of basic research applications, recombinant alphavirus RNA replicons may also facilitate genetic vaccination and transient gene therapy.
Functional breakdown of the lipid bilayer of the myelin membrane in central and peripheral nervous system by disrupted galactocerebroside synthesis
Authors: Bosio Andreas , Binczek Erika , Stoffel Wilhelm
Published: July 2002

The lipid bilayer of the myelin membrane of the central nervous
system (CNS) and the peripheral nervous system (PNS) contains the
oligodendrocyte- and Schwann cell-specific glycosphingolipids
galactocerebrosides (GalC) and GalC-derived sulfatides (sGalC). We have
generated a UDP-galactose ceramide galactosyltransferase (CGT) null
mutant mouse (
cgt
−/−
) with CNS and PNS
myelin completely depleted of GalC and derived sGalC. Oligodendrocytes
and Schwann cells are unable to restore the structure and function of
these galactosphingolipids to maintain the insulator function of the
membrane bilayer. The velocity of nerve conduction of homozygous
cgt
−/−
mice is reduced to that of
unmyelinated axons. This indicates a severely altered ion permeability
of the lipid bilayer. GalC and sGalC are essential for the unperturbed
lipid bilayer of the myelin membrane of CNS and PNS. The severe
dysmyelinosis leads to death of the
cgt
−/−
mouse at the end of the myelination period.
Sequence-specific antitumor activity of a phosphorothioate oligodeoxyribonucleotide targeted to human C-
raf
kinase supports an antisense mechanism of action
in vivo
Authors: Monia Brett P. , Sasmor Henri , Johnston Joseph F. , Freier Susan M. , Lesnik Elena A. , Muller Marcel , Geiger Thomas , Altmann Karl-Heinz , Moser Heinz , Fabbro Doriano
Published: July 2002

To determine the mechanism of action responsible for the
in
vivo
antitumor activity of a phosphorothioate antisense
inhibitor targeted against human C-
raf
kinase (ISIS
5132, also known as CGP69846A), a series of mismatched phosphorothioate
analogs of ISIS 5132 or CGP69846A were synthesized and characterized
with respect to hybridization affinity, inhibitory effects on
C-
raf
gene expression
in vitro
, and
antitumor activity
in vivo
. Incorporation of a single
mismatch into the sequence of ISIS 5132 or CGP69846A resulted in
reduced hybridization affinity toward C-
raf
RNA
sequences and reduced inhibitory activity against C-
raf
expression
in vitro
and tumor growth
in
vivo
. Moreover, incorporation of additional mismatches resulted
in further loss of
in vitro
and
in vivo
activity in a manner that correlated well with a hybridization-based
(i.e., antisense) mechanism of action. These results provide important
experimental evidence supporting an antisense mechanism of action
underlying the
in vivo
antitumor activity displayed by
ISIS 5132 or CGP69846A.
A quantitative test to estimate neutralizing antibodies to the hepatitis C virus: cytofluorimetric assessment of envelope glycoprotein 2 binding to target cells.
Authors: Rosa D , Campagnoli S , Moretto C , Guenzi E , Cousens L , Chin M , Dong C , Weiner A J , Lau J Y , Choo Q L , Chien D , Pileri P , Houghton M , Abrignani S
Published: July 2002

Hepatitis C virus (HCV) is a major cause of chronic hepatitis. The virus does not replicate efficiently in cell cultures, and it is therefore difficult to assess infection-neutralizing antibodies and to evaluate protective immunity in vitro. To study the binding of the HCV envelope to cell-surface receptors, we developed an assay to assess specific binding of recombinant envelope proteins to human cells and neutralization thereof. HCV recombinant envelope proteins expressed in various systems were incubated with human cells, and binding was assessed by flow cytometry using anti-envelope antibodies. Envelope glycoprotein 2 (E2) expressed in mammalian cells, but not in yeast or insect cells, binds human cells with high affinity (Kd approximately 10(-8) M). We then assessed antibodies able to neutralize E2 binding in the sera of both vaccinated and carrier chimpanzees, as well as in the sera of humans infected with various HCV genotypes. Vaccination with recombinant envelope proteins expressed in mammalian cells elicited high titers of neutralizing antibodies that correlated with protection from HCV challenge. HCV infection does not elicit neutralizing antibodies in most chimpanzees and humans, although low titers of neutralizing antibodies were detectable in a minority of infections. The ability to neutralize binding of E2 derived from the HCV-1 genotype was equally distributed among sera from patients infected with HCV genotypes 1, 2, and 3, demonstrating that binding of E2 is partly independent of E2 hypervariable regions. However, a mouse monoclonal antibody raised against the E2 hypervariable region 1 can partially neutralize binding of E2, indicating that at least two neutralizing epitopes, one of which is hypervariable, should exist on the E2 protein. The neutralization-of-binding assay described will be useful to study protective immunity to HCV infection and for vaccine development.
Pathogenic autoantibodies are routinely generated during the response to foreign antigen: a paradigm for autoimmune disease.
Authors: Ray S K , Putterman C , Diamond B
Published: July 2002

The immune system's ability to distinguish self and nonself is essential for both host defense against foreign agents and protection of self-antigens from autoimmune destruction. Such discrimination is complicated by extensive structural homology shared between foreign and self antigens. One hypothesis to explain the development of an autoimmune response is that some B cells activated by foreign antigen acquire, through somatic mutation, specificity for both the eliciting foreign antigen and self antigen. If such clones arise frequently, there must be a mechanism for their elimination. We have analyzed the extent of autoreactivity arising in a nonautoimmune host during the response to a foreign antigen. To overcome the process of apoptosis in primary B cells that might routinely eliminate autoreactive clones, we generated B-cell hybridomas from spleen cells of immunized mice by using a fusion partner constitutively expressing bcl-2. Multiple lines were obtained that recognize simultaneously the hapten phosphorylcholine and the self antigen double-stranded DNA. This dual specificity was not present early but was detected by day 10 after immunization. Some of these cross-reactive antibodies deposit in kidneys in a pattern similar to what is seen in autoimmune disease. These results demonstrate that autoantibodies arise at a high frequency as part of a response to foreign antigen. It has previously been shown that autoreactivity is regulated by central deletion; these data demonstrate a need for negative selection in peripheral lymphoid organs also, to regulate autoantibodies acquiring their self-specificity by somatic mutation.
The molecular biology of apoptosis.
Authors: Vaux D L , Strasser A
Published: July 2002

All multicellular organisms have mechanisms for killing their own cells, and use physiological cell death for defence, development, homeostasis, and aging. Apoptosis is a morphologically recognizable form of cell death that is implemented by a mechanism that has been conserved throughout evolution from nematode to man. Thus homologs of the genes that implement cell death in nematodes also do so in mammals, but in mammals the process is considerably more complex, involving multiple isoforms of the components of the cell death machinery. In some circumstances this allows independent regulation of pathways that converge upon a common end point. A molecular understanding of this mechanism may allow design of therapies that either enhance or block cell death at will.
Balancing immunity and tolerance: deleting and tuning lymphocyte repertoires.
Authors: Goodnow C C
Published: July 2002

Immunological self-tolerance is ensured by eliminating or inhibiting self-reactive lymphocyte clones, creating physical or functional holes in the B- and T-lymphocyte antigen receptor repertoires. The nature and size of these gaps in our immune defenses must be balanced against the necessity of mounting rapid immune responses to an everchanging array of foreign pathogens. To achieve this balance, only a fraction of particularly hazardous self-reactive clones appears to be physically eliminated from the repertoire in a manner that fully prevents their recruitment into an antimicrobial immune response. Many self-reactive cells are retained with a variety of conditional and potentially flexible restraints: (i) their ability to be triggered by antigen is diminished by mechanisms that tune down signaling by their antigen receptors, (ii) their ability to carry out inflammatory effector functions can be inhibited, and (iii) their capacity to migrate and persist is constrained. This balance between tolerance and immunity can be shifted, altering susceptibility to autoimmune disease and to infection by genetic or environmental differences either in the way antigens are presented, in the tuning molecules that adjust triggering set points for lymphocyte responses to antigen, or in the effector molecules that eliminate, retain, or expand particular clones.
Intracortical and corticothalamic coherency of fast spontaneous oscillations.
Authors: Steriade M , Amzica F
Published: July 2002

We report that fast (mainly 30- to 40-Hz) coherent electric field oscillations appear spontaneously during brain activation, as expressed by electroencephalogram (EEG) rhythms, and they outlast the stimulation of mesopontine cholinergic nuclei in acutely prepared cats. The fast oscillations also appear during the sleep-like EEG patterns of ketamine/xylazine anesthesia, but they are selectively suppressed during the prolonged phase of the slow (<1-Hz) sleep oscillation that is associated with hyperpolarization of cortical neurons. The fast (30- to 40-Hz) rhythms are synchronized intracortically within vertical columns, among closely located cortical foci, and through reciprocal corticothalamic networks. The fast oscillations do not reverse throughout the depth of the cortex. This aspect stands in contrast with the conventional depth profile of evoked potentials and slow sleep oscillations that display opposite polarity at the surface and midlayers. Current-source-density analyses reveal that the fast oscillations are associated with alternating microsinks and microsources across the cortex, while the evoked potentials and the slow oscillation display a massive current sink in midlayers, confined by two sources in superficial and deep layers. The synchronization of fast rhythms and their high amplitudes indicate that the term "EEG desynchronization," used to designate brain-aroused states, is incorrect and should be replaced with the original term, "EEG activation" [Moruzzi, G. & Magoun, H.W. (1949) Electroencephalogr. Clin. Neurophysiol. 1, 455-473].
Phylogeny of the genus
Pistacia
as determined from analysis of the chloroplast genome
Authors: Parfitt Dan E. , Badenes Maria L.
Published: July 2002

Classification within the genus
Pistacia
has been based on leaf morphology and geographical distribution. Molecular genetic tools (PCR amplification followed by restriction analysis of a 3.2-kb region of variable chloroplast DNA, and restriction fragment length polymorphism analysis of the
Pistacia
cpDNA with tobacco chloroplast DNA probes) provided a new set of variables to study the phylogenetic relationships of 10
Pistacia
species. Both parsimony and cluster analyses were used to divide the genus into two major groups.
P. vera
was determined to be the least derived species.
P. weinmannifolia
, an Asian species, is most closely related to
P. texana
and
P. mexicana
, New World species. These three species share a common origin, suggesting that a common ancestor of
P. texana
and
P. mexicana
originated in Asia.
P. integerrima
and
P. chinensis
were shown to be distinct whereas the pairs of species were monophyletic within each of two tertiary groups,
P. vera
:
P. khinjuk
and
P. mexicana
:
P. texana
. An evolutionary trend from large to small nuts and leaves with few, large leaflets to many, small leaflets was supported. The genus
Pistacia
was shown to have a low chloroplast DNA mutation rate: 0.05–0.16 times that expected of annual plants.