bluuebunny/crossref_metadata_2025 huggingface dataset:
Description of microcolumnar ensembles in association cortex and their disruption in Alzheimer and Lewy body dementias
Authors: Buldyrev S. V. , Cruz L. , Gomez-Isla T. , Gomez-Tortosa E. , Havlin S. , Le R. , Stanley H. E. , Urbanc B. , Hyman B. T.
Published: July 2002

The cortex of the brain is organized into clear horizontal layers, laminae, which subserve much of the connectional anatomy of the brain. We hypothesize that there is also a vertical anatomical organization that might subserve local interactions of neuronal functional units, in accord with longstanding electrophysiological observations. We develop and apply a general quantitative method, inspired by analogous methods in condensed matter physics, to examine the anatomical organization of the cortex in human brain. We find, in addition to obvious laminae, anatomical evidence for tightly packed microcolumnar ensembles containing approximately 11 neurons, with a periodicity of about 80 μm. We examine the structural integrity of this new architectural feature in two common dementing illnesses, Alzheimer disease and dementia with Lewy bodies. In Alzheimer disease, there is a dramatic, nearly complete loss of microcolumnar ensemble organization. The relative degree of loss of microcolumnar ensembles is directly proportional to the number of neurofibrillary tangles, but not related to the amount of amyloid-β deposition. In dementia with Lewy bodies, a similar disruption of microcolumnar ensemble architecture occurs despite minimal neuronal loss. These observations show that quantitative analysis of complex cortical architecture can be applied to analyze the anatomical basis of brain disorders.
Specific and heritable genetic interference by double-stranded RNA in
Arabidopsis thaliana
Authors: Chuang Chiou-Fen , Meyerowitz Elliot M.
Published: July 2002

We investigated the potential of double-stranded RNA interference
(RNAi) with gene activity in
Arabidopsis thaliana
. To
construct transformation vectors that produce RNAs capable of duplex
formation, gene-specific sequences in the sense and antisense
orientations were linked and placed under the control of a strong viral
promoter. When introduced into the genome of
A. thaliana
by
Agrobacterium
-mediated transformation,
double-stranded RNA-expressing constructs corresponding to four genes,
AGAMOUS
(
AG
),
CLAVATA3
,
APETALA1
, and
PERIANTHIA
, caused specific
and heritable genetic interference. The severity of phenotypes varied
between transgenic lines.
In situ
hybridization revealed
a correlation between a declining
AG
mRNA accumulation
and increasingly severe phenotypes in
AG
(
RNAi
) mutants, suggesting that endogenous
mRNA is the target of double-stranded RNA-mediated genetic
interference. The ability to generate stably heritable RNAi and the
resultant specific phenotypes allows us to selectively reduce gene
function in
A. thaliana
.
Appetite of an epiphyte: Quantitative monitoring of bacterial sugar consumption in the phyllosphere
Authors: Leveau Johan H. J. , Lindow Steven E.
Published: July 2002

We report here the construction, characterization, and application
of a bacterial bioreporter for fructose and sucrose that was designed
to monitor the availability of these sugars to microbial colonizers of
the phyllosphere. Plasmid pP
fruB
-
gfp
[AAV]
carries the
Escherichia coli fruB
promoter upstream from
the
gfp
[AAV] allele that codes for an unstable variant
of green fluorescent protein (GFP). In
Erwinia
herbicola,
this plasmid brings about the accumulation of GFP
fluorescence in response to both fructose and sucrose. Cells of
E. herbicola
(pP
fruB
-
gfp
[AAV]) were sprayed onto bean
plants, recovered from leaves at various time intervals after
inoculation, and analyzed individually for GFP content by quantitative
analysis of digital microscope images. We observed a positive
correlation between single-cell GFP accumulation and ribosomal content
as determined by fluorescence
in situ
hybridization,
indicating that foliar growth of
E. herbicola
occurred
at the expense of fructose and/or sucrose. One hour after
inoculation, nearly all bioreporter cells appeared to be actively
engaged in fructose consumption. This fraction dropped to approximately
11% after 7 h and to ≈1% a day after inoculation. This pattern
suggests a highly heterogeneous availability of fructose to individual
E. herbicola
cells as they colonize the phyllosphere. We
estimated that individual cells were exposed to local initial fructose
abundances ranging from less than 0.15 pg fructose to more than 4.6 pg.
A fragment of the HMGN2 protein homes to the nuclei of tumor cells and tumor endothelial cells
in vivo
Authors: Porkka Kimmo , Laakkonen Pirjo , Hoffman Jason A. , Bernasconi Michele , Ruoslahti Erkki
Published: July 2002

We used a screening procedure to identify protein domains from phage-displayed cDNA libraries that bind both to bone marrow endothelial progenitor cells and tumor vasculature. Screening phage for binding of progenitor cell-enriched bone marrow cells
in vitro
, and for homing to HL-60 human leukemia cell xenograft tumors
in vivo
, yielded a cDNA fragment that encodes an N-terminal fragment of human high mobility group protein 2 (HMGN2, formerly HMG-17). Upon i.v. injection, phage displaying this HMGN2 fragment homed to HL-60 and MDA-MB-435 tumors. Testing of subfragments localized the full binding activity to a 31-aa peptide (F3) in the HMGN2 sequence. Fluorescein-labeled F3 peptide bound to and was internalized by HL-60 cells and human MDA-MB-435 breast cancer cells, appearing initially in the cytoplasm and then in the nuclei of these cells. Fluorescent F3 accumulated in HL-60 and MDA-MB-435 tumors after an i.v. injection, appearing in the nuclei of tumor endothelial cells and tumor cells. Thus, F3 can carry a payload (phage, fluorescein) to a tumor and into the cell nuclei in the tumor. This peptide may be suitable for targeting cytotoxic drugs and gene therapy vectors into tumors.
Selenoprotein R is a zinc-containing stereo-specific methionine sulfoxide reductase
Authors: Kryukov Gregory V. , Kumar R. Abhilash , Koc Ahmet , Sun Zhaohui , Gladyshev Vadim N.
Published: July 2002

Selenoprotein R (SelR) is a mammalian
selenocysteine-containing protein with no known function. Here
we report that cysteine homologs of SelR are present in all organisms
except certain parasites and hyperthermophiles, and this pattern of
occurrence closely matches that of only one protein, peptide methionine
sulfoxide reductase (MsrA). Moreover, in several genomes, SelR and MsrA
genes are fused or clustered, and their expression patterns suggest a
role of both proteins in protection against oxidative stress.
Consistent with these computational screens, growth of
Saccharomyces cerevisiae
SelR and MsrA mutant strains
was inhibited, and the strain lacking both genes could not grow, in the
presence of H
2
O
2
and methionine sulfoxide. We
found that the cysteine mutant of mouse SelR, as well as the
Drosophila
SelR homolog, contained zinc and reduced
methionine-
R
-sulfoxide, but not
methionine-
S
-sulfoxide, in
in vitro
assays, a function that is both distinct and complementary to the
stereo-specific activity of MsrA. These findings identify a function of
the conserved SelR enzyme family, define a pathway of methionine
sulfoxide reduction, reveal a case of convergent evolution of similar
function in structurally distinct enzymes, and suggest a previously
uncharacterized redox regulatory role of selenium in mammals.
CD40 stimulation leads to effective therapy of CD40−tumors through induction of strong systemic cytotoxic T lymphocyte immunity
Authors: van Mierlo Geertje J. D. , den Boer Annemieke Th. , Medema Jan Paul , van der Voort Ellen I. H. , Fransen Marieke F. , Offringa Rienk , Melief Cornelis J. M. , Toes Rene E. M.
Published: July 2002

Adequate spontaneous activation of tumor-specific T lymphocytes in tumor-bearing hosts is rare, despite the expression of tumor antigens that are potentially highly immunogenic. For example, failure of the immune system to raise competent responses against established tumors expressing the human adenovirus E1A-antigen allows this tumor to grow in immunocompetent mice. We show that systemicin vivoadministration of agonistic anti-CD40 antibodies into tumor-bearing mice results in tumor eradication mediated by CD8+T cells. Treatment resulted in a strong expansion and systemic accumulation of E1A-specific CTL and depended on CD40 expression on host cells, as the tumor was CD40−, and therapy failed in CD40-deficient mice. Local intratumoral administration of anti-CD40 mAb is equally effective in licensing strong, systemic CTL immunity, resulting in the clearance of distant tumor nodules. Our data indicate that the immune response after cancer–host interactions can be directed toward competence, leading to the cure of established tumors merely by delivery of a CD40-dependent “license to kill” signal.
Low IGF-I suppresses VEGF-survival signaling in retinal endothelial cells: Direct correlation with clinical retinopathy of prematurity
Authors: Hellstrom Ann , Perruzzi Carole , Ju Meihua , Engström Eva , Hård Anna-Lena , Liu Jun-Li , Albertsson-Wikland Kerstin , Carlsson Björn , Niklasson Aimon , Sjödell Lena , LeRoith Derek , Senger Donald R. , Smith Lois E. H.
Published: July 2002

Retinopathy of prematurity is a blinding disease, initiated by lack
of retinal vascular growth after premature birth. We show that lack of
insulin-like growth factor I (IGF-I) in knockout mice prevents normal
retinal vascular growth, despite the presence of vascular endothelial
growth factor, important to vessel development.
In
vitro
, low levels of IGF-I prevent vascular endothelial growth
factor-induced activation of protein kinase B (Akt), a kinase critical
for endothelial cell survival. Our results from studies in premature
infants suggest that if the IGF-I level is sufficient after birth,
normal vessel development occurs and retinopathy of prematurity does
not develop. When IGF-I is persistently low, vessels cease to grow,
maturing avascular retina becomes hypoxic and vascular endothelial
growth factor accumulates in the vitreous. As IGF-I increases to a
critical level, retinal neovascularization is triggered. These data
indicate that serum IGF-I levels in premature infants can predict which
infants will develop retinopathy of prematurity and further suggests
that early restoration of IGF-I in premature infants to normal levels
could prevent this disease.
Integration of Runx and Smad regulatory signals at transcriptionally active subnuclear sites
Authors: Zaidi Sayyed K. , Sullivan Andrew J. , van Wijnen Andre J. , Stein Janet L. , Stein Gary S. , Lian Jane B.
Published: July 2002

Runx factors control lineage commitment and are transcriptional effectors of Smad signaling. Genetic defects in these pathways interfere with normal development. The
in situ
localization of Runx and Smad proteins must impact the mechanisms by which these proteins function together in gene regulation. We show that the integration of Runx and Smad signals is mediated by
in situ
interactions at specific foci within the nucleus. Activated Smads are directed to these subnuclear foci only in the presence of Runx proteins. Smad–Runx complexes are associated
in situ
with the nuclear matrix, and this association requires the intranuclear targeting signal of Runx factors. The convergence of Smad and Runx proteins at these sites supports transcription as reflected by BrUTP labeling and functional cooperativity between the proteins. Thus, Runx-mediated intranuclear targeting of Smads is critical for the integration of two distinct pathways essential for fetal development.
Balancing transcriptional interference and initiation on the
GAL7
promoter of
Saccharomyces cerevisiae
Authors: Greger Ingo H. , Aranda Agustín , Proudfoot Nick
Published: July 2002

Transcriptional termination of the
GAL10
gene in
Saccharomyces cerevisiae
depends on the efficiency of
polyadenylation. Either
cis
mutations in the poly(A)
signal or
trans
mutations of mRNA 3′ end cleavage
factors result in
GAL10
read-through transcripts into
the adjacent
GAL7
gene and inactivation (occlusion) of
the
GAL7
promoter. Herein, we present a molecular
explanation of this transcriptional interference phenomenon.
In
vivo
footprinting data reveal that
GAL7
promoter
occlusion is associated with the displacement of Gal4p transcription
factors from the promoter. Interestingly, overexpression of Gal4p
restores promoter occupancy, activates
GAL7
expression,
and rescues growth on the otherwise toxic galactose substrate. Our data
therefore demonstrate a precise balance between transcriptional
interference and initiation.
Mechanical behavior in living cells consistent with the tensegrity model
Authors: Wang Ning , Naruse Keiji , Stamenović Dimitrije , Fredberg Jeffrey J. , Mijailovich Srboljub M. , Tolić-Nørrelykke Iva Marija , Polte Thomas , Mannix Robert , Ingber Donald E.
Published: July 2002

Alternative models of cell mechanics depict the living cell as a simple mechanical continuum, porous filament gel, tensed cortical membrane, or tensegrity network that maintains a stabilizing prestress through incorporation of discrete structural elements that bear compression. Real-time microscopic analysis of cells containing GFP-labeled microtubules and associated mitochondria revealed that living cells behave like discrete structures composed of an interconnected network of actin microfilaments and microtubules when mechanical stresses are applied to cell surface integrin receptors. Quantitation of cell tractional forces and cellular prestress by using traction force microscopy confirmed that microtubules bear compression and are responsible for a significant portion of the cytoskeletal prestress that determines cell shape stability under conditions in which myosin light chain phosphorylation and intracellular calcium remained unchanged. Quantitative measurements of both static and dynamic mechanical behaviors in cells also were consistent with specific
a priori
predictions of the tensegrity model. These findings suggest that tensegrity represents a unified model of cell mechanics that may help to explain how mechanical behaviors emerge through collective interactions among different cytoskeletal filaments and extracellular adhesions in living cells.
4-Hydroxytamoxifen binds to and deactivates the estrogen-related receptor γ
Authors: Coward Peter , Lee Doris , Hull Mitchell V. , Lehmann Jürgen M.
Published: July 2002

The estrogen-related receptors (ERRα, ERRβ, and ERRγ) form a family of orphan nuclear receptors that share significant amino acid identity with the estrogen receptors, but for which physiologic roles remain largely unknown. By using a peptide sensor assay, we have identified the stilbenes diethylstilbestrol (DES), tamoxifen (TAM), and 4-hydroxytamoxifen (4-OHT) as high-affinity ligands for ERRγ. In direct binding assays, 4-OHT had a
K
d
value of 35 nM, and both DES and TAM displaced radiolabeled 4-OHT with
K
i
values of 870 nM. In cell-based assays, 4-OHT binding caused a dissociation of the complex between ERRγ and the steroid receptor coactivator-1, and led to an inhibition of the constitutive transcriptional activity of ERRγ. ERRα did not bind 4-OHT, but replacing a single amino acid predicted to be in the ERRα ligand-binding pocket with the corresponding ERRγ residue allowed high-affinity 4-OHT binding. These results demonstrate the existence of high-affinity ligands for the ERR family of orphan receptors, and identify 4-OHT as a molecule that can regulate the transcriptional activity of ERRγ.
Conductivity tensor mapping of the human brain using diffusion tensor MRI
Authors: Tuch David S. , Wedeen Van J. , Dale Anders M. , George John S. , Belliveau John W.
Published: July 2002

Knowledge of the electrical conductivity properties of excitable
tissues is essential for relating the electromagnetic fields generated
by the tissue to the underlying electrophysiological currents. Efforts
to characterize these endogenous currents from measurements
of the associated electromagnetic fields would significantly benefit
from the ability to measure the electrical conductivity properties of
the tissue noninvasively. Here, using an effective medium approach, we
show how the electrical conductivity tensor of tissue can be
quantitatively inferred from the water self-diffusion tensor as
measured by diffusion tensor magnetic resonance imaging. The effective
medium model indicates a strong linear relationship between the
conductivity and diffusion tensor eigenvalues (respectively, σ and
d
) in agreement with theoretical bounds and experimental
measurements presented here (σ/
d
≈ 0.844 ±
0.0545 S⋅s/mm
3
,
r
2
=
0.945). The extension to other biological transport phenomena is also
discussed.
Fine-scale mapping of a locus for severe bipolar mood disorder on chromosome 18p11.3 in the Costa Rican population
Authors: McInnes L. Alison , Service Susan K. , Reus Victor I. , Barnes Glenn , Charlat Olga , Jawahar Satya , Lewitzky Steve , Yang Qing , Duong Quyen , Spesny Mitzi , Araya Carmen , Araya Xinia , Gallegos Alvaro , Meza Luis , Molina Julio , Ramirez Rolando , Mendez Roxana , Silva Sandra , Fournier Eduardo , Batki Steven L. , Mathews Carol A. , Neylan Thomas , Glatt Charles E. , Escamilla Michael A. , Luo David , Gajiwala Paresh , Song Terry , Crook Stephen , Nguyen Jasmine B. , Roche Erin , Meyer Joanne M. , Leon Pedro , Sandkuijl Lodewijk A. , Freimer Nelson B. , Chen Hong
Published: July 2002

We have searched for genes predisposing to bipolar disorder (BP) by
studying individuals with the most extreme form of the affected
phenotype, BP-I, ascertained from the genetically isolated population
of the Central Valley of Costa Rica (CVCR). The results of a previous
linkage analysis on two extended CVCR BP-I pedigrees, CR001 and CR004,
and of linkage disequilibrium (LD) analyses of a CVCR population sample
of BP-I patients implicated a candidate region on 18p11.3. We further
investigated this region by creating a physical map and developing 4
new microsatellite and 26 single-nucleotide polymorphism markers for
typing in the pedigree and population samples. We report the results of
fine-scale association analyses in the population sample, as well as
evaluation of haplotypes in pedigree CR001. Our results suggest a
candidate region containing six genes but also highlight the
complexities of LD mapping of common disorders.
On the nature of a glassy state of matter in a hydrated protein: Relation to protein function
Authors: Teeter M. M. , Yamano A. , Stec B. , Mohanty U.
Published: July 2002

Diverse biochemical and biophysical experiments indicate that all
proteins, regardless of size or origin, undergo a dynamic transition
near 200 K. The cause of this shift in dynamic behavior, termed a
“glass transition,” and its relation to protein function are
important open questions. One explanation postulated for the transition
is solidification of correlated motions in proteins below the
transition. We verified this conjecture by showing that crambin's
radius of gyration (Rg) remains constant below ≈180 K. We show that
both atom position and dynamics of protein and solvent are physically
coupled, leading to a novel cooperative state. This glassy state is
identified by negative slopes of the Debye-Waller (B) factor vs.
temperature. It is composed of multisubstate side chains and solvent.
Based on generalization of Adam-Gibbs' notion of a cooperatively
rearranging region and decrease of the total entropy with temperature,
we calculate the slope of the Debye-Waller factor. The results are in
accord with experiment.
Galanin regulates the postnatal survival of a subset of basal forebrain cholinergic neurons
Authors: O'Meara Gillian , Coumis Urania , Ma Shuang Y. , Kehr Jan , Mahoney Sally , Bacon Andrea , Allen Shelley J. , Holmes Fiona , Kahl Ulrika , Wang Fu H. , Kearns Ian R. , Ove-Ogren Sven , Dawbarn David , Mufson Elliott J. , Davies Ceri , Dawson Gerard , Wynick David
Published: July 2002

The neuropeptide galanin colocalizes with choline
acetyltransferase, the synthetic enzyme for acetylcholine, in a subset
of cholinergic neurons in the basal forebrain of rodents. Chronic
intracerebroventricular infusion of nerve growth factor induces a 3- to
4-fold increase in galanin gene expression in these neurons. Here we
report the loss of a third of cholinergic neurons in the medial septum
and vertical limb diagonal band of the basal forebrain of adult mice
carrying a targeted loss-of-function mutation in the galanin gene.
These deficits are associated with a 2-fold increase in the number of
apoptotic cells in the forebrain at postnatal day seven. This
loss is associated with marked age-dependent deficits in stimulated
acetylcholine release, performance in the Morris water maze, and
induction of long-term potentiation in the CA1 region of the
hippocampus. These data provide unexpected evidence that galanin plays
a trophic role to regulate the development and function of a subset of
septohippocampal cholinergic neurons.
The role of binding domains for dsRNA and Z-DNA in the
in vivo
editing of minimal substrates by ADAR1
Authors: Herbert Alan , Rich Alexander
Published: July 2002

RNA editing changes the read-out of genetic information, increasing the number of different protein products that can be made from a single gene. One form involves the deamination of adenosine to form inosine, which is subsequently translated as guanosine. The reaction requires a double-stranded RNA (dsRNA) substrate and is catalyzed by the adenosine deaminase that act on dsRNA (ADAR) family of enzymes. These enzymes possess dsRNA-binding domains (DRBM) and a catalytic domain. ADAR1 so far has been found only in vertebrates and is characterized by two Z-DNA-binding motifs, the biological function of which remains unknown. Here the role of the various functional domains of ADAR1 in determining the editing efficiency and specificity of ADAR1 is examined in cell-based assays. A variety of dsRNA substrates was tested. It was found that a 15-bp dsRNA stem with a single base mismatch was sufficient for editing. The particular adenosine modified could be varied by changing the position of the mismatch. Editing efficiency could be increased by placing multiple pyrimidines 5′ to the edited adenosine. With longer substrates, editing efficiency also increased and was partly due to the use of DRBMs. Additional editing sites were also observed that clustered on the complementary strand 11–15 bp from the first. An unexpected finding was that the DRBMs are not necessary for the editing of the shorter 15-bp substrates. However, mutation of the Z-DNA-binding domains of ADAR1 decreased the efficiency with which such a substrate was edited.
Natural killer T cells reactive to a single glycolipid exhibit a highly diverse T cell receptor β repertoire and small clone size
Authors: Matsuda Jennifer L. , Gapin Laurent , Fazilleau Nicolas , Warren Kris , Naidenko Olga V. , Kronenberg Mitchell
Published: July 2002

CD1d-restricted natural killer (NK) T cells reactive with the glycolipid α-galactosylceramide (α-GalCer) are a distinct lymphocyte sublineage. They express an invariant Vα14-Jα18 T cell receptor (TcR), but the role of the β chain has been controversial. Here, we have used CD1d tetramers to identify and isolate NK T cells based on their antigen specificity. In mice lacking germline Vβ8, most of the α-GalCer-reactive T cells express either Vβ2 or Vβ7, strong Vβ selection being revealed by the lack of an increase in other Vβ regions. By contrast to the selection for complementarity determining region (CDR) 3β sequences in some anti-peptide responses, α-GalCer-reactive T cells have polyclonal CDR3β sequences. There is little CDR3β sequence redundancy between organs or individual mice, and, surprisingly, there also is no evidence for organ-specific CDR3β sequence motifs. These data argue against a T cell receptor-mediated self-reactivity for tissue-specific CD1d-bound ligands. Each NKT clone is represented by only 5–10 cells. This clone size is similar to naive conventional T cells, and much lower than that reported for memory T cells, although NK T cells have an activated/memory phenotype.
Molecular phylogenetic analysis of evolutionary trends in stonefly wing structure and locomotor behavior
Authors: Thomas Michael A. , Walsh Kathleen A. , Wolf Melisande R. , McPheron Bruce A. , Marden James H.
Published: July 2002

Insects in the order Plecoptera (stoneflies) use a form of
two-dimensional aerodynamic locomotion called surface skimming to move
across water surfaces. Because their weight is supported by water,
skimmers can achieve effective aerodynamic locomotion even with small
wings and weak flight muscles. These mechanical features stimulated the
hypothesis that surface skimming may have been an intermediate stage in
the evolution of insect flight, which has perhaps been retained in
certain modern stoneflies. Here we present a phylogeny of Plecoptera
based on nucleotide sequence data from the small subunit rRNA (18S)
gene. By mapping locomotor behavior and wing structural data onto the
phylogeny, we distinguish between the competing hypotheses that
skimming is a retained ancestral trait or, alternatively, a relatively
recent loss of flight. Our results show that basal stoneflies are
surface skimmers, and that various forms of surface skimming are
distributed widely across the plecopteran phylogeny. Stonefly wings
show evolutionary trends in the number of cross veins and the thickness
of the cuticle of the longitudinal veins that are consistent with
elaboration and diversification of flight-related traits. These data
support the hypothesis that the first stoneflies were surface skimmers,
and that wing structures important for aerial flight have become
elaborated and more diverse during the radiation of modern stoneflies.
Peptide vaccination can lead to enhanced tumor growth through specific T-cell tolerance induction.
Authors: Toes R E , Offringa R , Blom R J , Melief C J , Kast W M
Published: July 2002

Vaccination with synthetic peptides representing cytotoxic T lymphocyte (CTL) epitopes can lead to a protective CTL-mediated immunity against tumors or viruses. We now report that vaccination with a CTL epitope derived from the human adenovirus type 5 E1A-region (Ad5E1A234-243), which can serve as a target for tumor-eradicating CTL, enhances rather than inhibits the growth of Ad5E1A-expressing tumors. This adverse effect of peptide vaccination was rapidly evoked, required low doses of peptide (10 micrograms), and was achieved by a mode of peptide delivery that induces protective T-cell-mediated immunity in other models. Ad5E1A-specific CTL activity could no longer be isolated from mice after injection of Ad5E1A-peptide, indicating that tolerization of Ad5E1A-specific CTL activity causes the enhanced tumor outgrowth. In contrast to peptide vaccination, immunization with adenovirus, expressing Ad5E1A, induced Ad5E1A-specific immunity and prevented the outgrowth of Ad5E1A-expressing tumors. These results show that immunization with synthetic peptides can lead to the elimination of anti-tumor CTL responses. These findings are important for the design of safe peptide-based vaccines against tumors, allogeneic organ transplants, and T-cell-mediated autoimmune diseases.
The hippocampal formation participates in novel picture encoding: evidence from functional magnetic resonance imaging.
Authors: Stern C E , Corkin S , González R G , Guimaraes A R , Baker J R , Jennings P J , Carr C A , Sugiura R M , Vedantham V , Rosen B R
Published: July 2002

Considerable evidence exists to support the hypothesis that the hippocampus and related medial temporal lobe structures are crucial for the encoding and storage of information in long-term memory. Few human imaging studies, however, have successfully shown signal intensity changes in these areas during encoding or retrieval. Using functional magnetic resonance imaging (fMRI), we studied normal human subjects while they performed a novel picture encoding task. High-speed echo-planar imaging techniques evaluated fMRI signal changes throughout the brain. During the encoding of novel pictures, statistically significant increases in fMRI signal were observed bilaterally in the posterior hippocampal formation and parahippocampal gyrus and in the lingual and fusiform gyri. To our knowledge, this experiment is the first fMRI study to show robust signal changes in the human hippocampal region. It also provides evidence that the encoding of novel, complex pictures depends upon an interaction between ventral cortical regions, specialized for object vision, and the hippocampal formation and parahippocampal gyrus, specialized for long-term memory.
XMCM7, a novel member of the Xenopus MCM family, interacts with XMCM3 and colocalizes with it throughout replication.
Authors: Romanowski P , Madine M A , Laskey R A
Published: July 2002

A minichromosome maintenance (MCM) protein complex has been implicated in restricting DNA replication to once per cell cycle in Xenopus egg extracts, based on the behavior of a single protein, XMCM3. Using a two-hybrid screen with XMCM3, we have identified a novel member of the MCM family in Xenopus that is essential for DNA replication. The protein shows strong homology to Saccharomyces cerevisiae MCM7 (CDC47) and has thus been named XMCM7. XMCM7 is present in a multiprotein complex with other MCM proteins. It binds to chromatin and is displaced from chromatin by the act of replication. XMCM7 does not preferentially colocalize with sites of DNA replication but colocalizes with XMCM3 throughout replication. Immunodepletion of the MCM complex from Xenopus egg extract by anti-XMCM7 antibodies inhibits DNA replication of sperm and permeable HeLa G2 nuclei but not permeable HeLa G1 nuclei. Replication capacity of the Xenopus egg extract immunodepleted of the MCM complex by anti-XMCM7 antibody can be rescued by MCM proteins eluted from anti-XMCM3 antibody. We conclude that both proteins are present in the same complex in Xenopus egg extract throughout the cell cycle, that they remain together after binding to chromatin and during DNA replication, and that they perform similar functions.
Multineuronal codes in retinal signaling.
Authors: Meister M
Published: July 2002

The visual world is presented to the brain through patterns of action potentials in the population of optic nerve fibers. Single-neuron recordings show that each retinal ganglion cell has a spatially restricted receptive field, a limited integration time, and a characteristic spectral sensitivity. Collectively, these response properties define the visual message conveyed by that neuron's action potentials. Since the size of the optic nerve is strictly constrained, one expects the retina to generate a highly efficient representation of the visual scene. By contrast, the receptive fields of nearby ganglion cells often overlap, suggesting great redundancy among the retinal output signals. Recent multineuron recordings may help resolve this paradox. They reveal concerted firing patterns among ganglion cells, in which small groups of nearby neurons fire synchronously with delays of only a few milliseconds. As there are many more such firing patterns than ganglion cells, such a distributed code might allow the retina to compress a large number of distinct visual messages into a small number of optic nerve fibers. This paper will review the evidence for a distributed coding scheme in the retinal output. The performance limits of such codes are analyzed with simple examples, illustrating that they allow a powerful trade-off between spatial and temporal resolution.
Regulation of topographic projection in the brain: Elf-1 in the hippocamposeptal system.
Authors: Gao P P , Zhang J H , Yokoyama M , Racey B , Dreyfus C F , Black I B , Zhou R
Published: July 2002

The hippocampus and septum play central roles in one of the most important spheres of brain function: learning and memory. Although their topographic connections have been known for two decades and topography may be critical for cognitive functions, the basis for hippocamposeptal topographic projection is unknown. We now report for the first time that Elf-1, a membrane-bound eph family ligand, is a candidate molecular tag for the genesis of the hippocamposeptal topographic projection. Elf-1 is expressed in an increasing gradient from dorsal to ventral septum. Furthermore, Elf-1 selectively allows growth of neurites from topographically appropriate lateral hippocampal neurons, while inhibiting neurite outgrowth by medial hippocampal neurons. Complementary to the expression of Elf-1, an eph family receptor, Bsk, is expressed in the hippocampus in a lateral to medial gradient, consistent with a function as a receptor for Elf-1. Further, Elf-1 specifically bound Bsk, eliciting tyrosine kinase activity. We conclude that the Elf-1/Bsk ligand-receptor pair exhibits traits of a chemoaffinity system for the organization of hippocamposeptal topographic projections.
A complete genome screen for genes predisposing to severe bipolar disorder in two Costa Rican pedigrees
Authors: McInnes L. Alison , Escamilla Michael A. , Service Susan K. , Reus Victor I. , Leon Pedro , Silva Sandra , Rojas Eugenia , Spesny Mitzi , Baharloo Siamak , Blankenship Kathleen , Peterson Amy , Tyler David , Shimayoshi Norito , Tobey Christa , Batki Steven , Vinogradov Sophia , Meza Luis , Gallegos Alvaro , Fournier Eduardo , Smith Lauren B. , Barondes Samuel H. , Sandkuijl Lodewijk A. , Freimer Nelson B.
Published: July 2002

Bipolar mood disorder (BP) is a debilitating syndrome characterized
by episodes of mania and depression. We designed a multistage study to
detect all major loci predisposing to severe BP (termed BP-I) in two
pedigrees drawn from the Central Valley of Costa Rica, where the
population is largely descended from a few founders in the 16th–18th
centuries. We considered only individuals with BP-I as affected and
screened the genome for linkage with 473 microsatellite markers. We
used a model for linkage analysis that incorporated a high phenocopy
rate and a conservative estimate of penetrance. Our goal in this study
was not to establish definitive linkage but rather to detect all
regions possibly harboring major genes for BP-I in these pedigrees. To
facilitate this aim, we evaluated the degree to which markers that were
informative in our data set provided coverage of each genome region; we
estimate that at least 94% of the genome has been covered, at a
predesignated threshold determined through prior linkage simulation
analyses. We report here the results of our genome screen for BP-I loci
and indicate several regions that merit further study, including
segments in 18q, 18p, and 11p, in which suggestive lod scores were
observed for two or more contiguous markers. Isolated lod scores that
exceeded our thresholds in one or both families also occurred on
chromosomes 1, 2, 3, 4, 5, 7, 13, 15, 16, and 17. Interesting regions
highlighted in this genome screen will be followed up using linkage
disequilibrium (LD) methods.
cdc18+ regulates initiation of DNA replication in Schizosaccharomyces pombe.
Authors: Muzi Falconi M , Brown G W , Kelly T J
Published: July 2002

In the fission yeast Schizosaccharomyces pombe the cdc18'+gene is required both for initiation of DNA replication and for coupling mitosis to the completion of S phase. Cells lacking Cdc18 fail to enter S phase but still undergo nuclear division. Expression of cdc18+ is sufficient to drive a G1-arrested cdc10ts mutant into the S phase of the cell cycle, indicating that cdc18+ represents a critical link between passage through START and the initiation of DNA replication. Here we show that Cdcl8 is a highly unstable protein that is expressed only once per cell cycle at the boundary between GI and S phase. De novo synthesis of Cdc18 is required before, but not after, the initiation of DNA replication, indicating that Cdc18 function is not necessary once the initiation event has occurred. Overproduction of the protein results in an accumulation of cells with DNA content of greater than 2C and delays mitosis, suggesting that Cdc18 is sufficient to cause reinitiation of DNA replication within a given cell cycle. Our data indicate that the synthesis of Cdc18 protein is a critical rate-limiting step in the initiation of DNA replication during each cell cycle. The extreme lability of the protein may contribute to the prevention of reinitiation.
Role of oxidation in the neurotoxic effects of intrastriatal dopamine injections.
Authors: Hastings T G , Lewis D A , Zigmond M J
Published: July 2002

We have examined the biochemical and histological effects of high concentrations of dopamine (0.05-1.0 micromol) injected into the rat striatum. Twenty-four hours after such injections, the oxidation products of dopamine and dihydroxyphenylacetic acid were detected as both free and protein-bound cysteinyl dopamine and cysteinyl dihydroxyphenylacetic acid. Protein-bound cysteinyl catechols were increased 7- to 20-fold above control tissue levels. By 7 days postinjection, the protein-bound cysteinyl catechols were still detectable, although reduced in concentration, whereas the free forms could no longer be measured. Histological examination of striatum at 7 days revealed a central core of nonspecific damage including neuronal loss and gliosis. This core was surrounded by a region containing a marked reduction in tyrosine hydroxylase immunoreactivity but no apparent loss of serotonin or synaptophysin immunoreactivity. When dopamine was injected with an equimolar concentration of either ascorbic acid or glutathione, the formation of protein-bound cysteinyl catechols was greatly reduced. Moreover, the specific loss of tyrosine hydroxylase immunoreactivity associated with dopamine injections was no longer detectable, although the nonspecific changes in cytoarchitecture were still apparent. Thus, following its oxidation, dopamine in high concentrations binds to protein in the striatum, an event that is correlated with the specific loss of dopaminergic terminals. We suggest that the selective degeneration of dopamine neurons in Parkinson's disease may be caused by an imbalance between the oxidation of dopamine and the availability of antioxidant defenses.
The human CAS protein which is homologous to the CSE1 yeast chromosome segregation gene product is associated with microtubules and mitotic spindle.
Authors: Scherf U , Pastan I , Willingham M C , Brinkmann U
Published: July 2002

Human CAS cDNA contains a 971-aa open reading frame that is homologous to the essential yeast gene CSE1. CSE1 is involved in chromosome segregation and is necessary for B-type cyclin degradation in mitosis. Using antibodies to CAS, it was shown that CAS levels are high in proliferating and low in nonproliferating cells. Here we describe the distribution of CAS in cells and tissues analyzed with antibodies against CAS. CAS is an approximately 100-kDa protein present in the cytoplasm of proliferating cells at levels between 2 x 10(5) and 1 x 10(6) molecules per cell. The intracellular distribution of CAS resembles that of tubulin. In interphase cells, anti-CAS antibody shows microtubule-like patterns and in mitotic cells it labels the mitotic spindle. CAS is removed from microtubules by mild detergent treatment (cytoskeleton preparations) and in vincristine- or taxol-treated cells. CAS is diffusely distributed in the cytoplasm with only traces present in tubulin paracrystals or bundles. Thus, CAS appears to be associated with but not to be an integral part of microtubules. Immunohistochemical staining of frozen tissues shows elevated amounts of CAS in proliferating cells such as testicular spermatogonia and cells in the basal layer cells of the colon. CAS was also concentrated in the respiratory epithelium of the trachea and in axons and Purkinje cells in the cerebellum. These cells contain many microtubules. The cellular location of CAS is consistent with an important role in cell division as well as in ciliary movement and vesicular transport.
Comparative analysis of ribonuclease P RNA using gene sequences from natural microbial populations reveals tertiary structural elements.
Authors: Brown J W , Nolan J M , Haas E S , Rubio M A , Major F , Pace N R
Published: July 2002

PCR amplification of template DNAs extracted from mixed, naturally occurring microbial populations, using oligonucleotide primers complementary to highly conserved sequences, was used to obtain a large collection of diverse RNase P RNA-encoding genes. An alignment of these sequences was used in a comparative analysis of RNase P RNA secondary and tertiary structure. The new sequences confirm the secondary structure model based on sequences from cultivated organisms (with minor alterations in helices P12 and P18), providing additional support for nearly every base pair. Analysis of sequence covariation using the entire RNase P RNA data set reveals elements of tertiary structure in the RNA; the third nucleotides (underlined) of the GNRA tetraloops L14 and L18 are seen to interact with adjacent Watson-Crick base pairs in helix P8, forming A:G/C or G:A/U base triples. These experiments demonstrate one way in which the enormous diversity of natural microbial populations can be used to elucidate molecular structure through comparative analysis.
Why are some proteins structures so common?
Authors: Govindarajan S , Goldstein R A
Published: July 2002

Many biological proteins are observed to fold into one of a limited number of structural motifs. By considering the requirements imposed on proteins by their need to fold rapidly, and the ease with which such requirements can be fulfilled as a function of the native structure, we can explain why certain structures are repeatedly observed among proteins with negligible sequence similarity. This work has implications for the understanding of protein sequence structure relationships as well as protein evolution.
Rapid appearance and asymmetric distribution of glucose transporter SGTP4 at the apical surface of intramammalian-stage Schistosoma mansoni.
Authors: Skelly P J , Shoemaker C B
Published: July 2002

Adult Schistosoma mansoni blood flukes reside in the mesenteric veins of their vertebrate hosts, where they absorb immense quantities of glucose through their tegument by facilitated diffusion. Previously, we obtained S. mansoni cDNAs encoding facilitated-diffusion schistosome glucose transporter proteins 1 and 4 (SGTP1 and SGTP4) and localized SGTP1 to the basal membranes of the tegument and the underlying muscle. In this study, we characterize the expression and localization of SGTP4 during the schistosome life cycle. Antibodies specific to SGTP4 appear to stain only the double-bilayer, apical membranes of the adult parasite tegument, revealing an asymmetric distribution relative to the basal transporter SGTP1. On living worms, SGTP4 is available to surface biotinylation, suggesting that it is exposed at the hose-parasite interface. SGTP4 is detected shortly after the transformation of free-living, infectious cercariae into schistosomula and coincides with the appearance of the double membrane. Within 15 min after transformation, anti-SGTP4 staining produces a bright, patchy distribution at the surface of schistosomula, which becomes contiguous over the entire surface of the schistosomula by 24 hr after transformation. SGTP4 is not detected in earlier developmental stages (eggs, sporocysts, and cercariae) that do not possess the specialized double membrane. Thus, SGTP4 appears to be expressed only in the mammalian stages of the parasite's life cycle and specifically localized within the host-interactive, apical membranes of the tegument.
The ALIAmide palmitoylethanolamide and cannabinoids, but not anandamide, are protective in a delayed postglutamate paradigm of excitotoxic death in cerebellar granule neurons.
Authors: Skaper S D , Buriani A , Dal Toso R , Petrelli L , Romanello S , Facci L , Leon A
Published: July 2002

The amino acid L-glutamate is a neurotransmitter that mediates fast neuronal excitation in a majority of synapses in the central nervous system. Glutamate stimulates both N-methyl-D-aspartate (NMDA) and non-NMDA receptors. While activation of NMDA receptors has been implicated in a variety of neurophysiologic processes, excessive NMDA receptor stimulation (excitotoxicity) is thought to be primarily responsible for neuronal injury in a wide variety of acute neurological disorders including hypoxia-ischemia, seizures, and trauma. Very little is known about endogenous molecules and mechanisms capable of modulating excitotoxic neuronal death. Saturated N-acylethanolamides like palmitoylethanolamide accumulate in ischemic tissues and are synthesized by neurons upon excitatory amino acid receptor activation. Here we report that palmitoylethanolamide, but not the cognate N-acylamide anandamide (the ethanolamide of arachidonic acid), protects cultured mouse cerebellar granule cells against glutamate toxicity in a delayed postagonist paradigm. Palmitoylethanolamide reduced this injury in a concentration-dependent manner and was maximally effective when added 15-min postglutamate. Cannabinoids, which like palmitoylethanolamide are functionally active at the peripheral cannabinoid receptor CB2 on mast cells, also prevented neuron loss in this delayed postglutamate model. Furthermore, the neuroprotective effects of palmitoylethanolamide, as well as that of the active cannabinoids, were efficiently antagonized by the candidate central cannabinoid receptor (CB1) agonist anandamide. Analogous pharmacological behaviors have been observed for palmitoylethanolamide (ALI-Amides) in downmodulating mast cell activation. Cerebellar granule cells expressed mRNA for CB1 and CB2 by in situ hybridization, while two cannabinoid binding sites were detected in cerebellar membranes. The results suggest that (i) non-CB1 cannabinoid receptors control, upon agonist binding, the downstream consequences of an excitotoxic stimulus; (ii) palmitoylethanolamide, unlike anandamide, behaves as an endogenous agonist for CB2-like receptors on granule cells; and (iii) activation of such receptors may serve to downmodulate deleterious cellular processes following pathological events or noxious stimuli in both the nervous and immune systems.
Expression of a divergent expansin gene is fruit-specific and ripening-regulated
Authors: Rose Jocelyn K. C. , Lee Howard H. , Bennett Alan B.
Published: July 2002

Expansins are proteins that induce extension in isolated plant cell wallsin vitroand have been proposed to disrupt noncovalent interactions between hemicellulose and cellulose microfibrils. Because the plant primary cell wall acts as a constraint to cell enlargement, this process may be integral to plant cell expansion, and studies of expansins have focused on their role in growth. We report the identification of an expansin (LeExp1) from tomato that exhibits high levels of mRNA abundance and is specifically expressed in ripening fruit, a developmental period when growth has ceased but when selective disassembly of cell wall components is pronounced. cDNAs closely related toLeExp1were also identified in ripening melons and strawberries, suggesting that they are a common feature of fruit undergoing rapid softening. Furthermore, the sequence ofLeExp1and its homologs from other ripening fruit define a subclass of expansin genes. Expression ofLeExp1is regulated by ethylene, a hormone known to coordinate and induce ripening in many species.LeExp1is differentially expressed in the ripening-impaired tomato mutantsNr,rin, andnor, and mRNA abundance appears to be influenced directly by ethylene and by a developmentally modulated transduction pathway. The identification of a ripening-regulated expansin gene in tomato and other fruit suggests that, in addition to their role in facilitating the expansion of plant cells, expansins may also contribute to cell wall disassembly in nongrowing tissues, possibly by enhancing the accessibility of noncovalently bound polymers to endogenous enzymic action.