bluuebunny/crossref_metadata_2025 huggingface dataset:
The homodimer of prostate-specific membrane antigen is a functional target for cancer therapy
Authors: Schülke Norbert , Varlamova Olga A. , Donovan Gerald P. , Ma Dangshe , Gardner Jason P , Morrissey Donna M. , Arrigale Robert R. , Zhan Cenchen , Chodera Amy J. , Surowitz Kenneth G. , Maddon Paul J. , Heston Warren D. W. , Olson William C.
Published: October 2003

Prostate-specific membrane antigen (PSMA) is a type 2 integral membrane glycoprotein that serves as an attractive target for cancer immunotherapy by virtue of its abundant and restricted expression on the surface of prostate carcinomas and the neovasculature of most other solid tumors. However, relatively little is known about the molecular structure of this target. Here, we report that PSMA is expressed on tumor cells as a noncovalent homodimer. A truncated PSMA protein, lacking transmembrane and cytoplasmic domains, also formed homodimers, indicating that the extracellular domain is sufficient for dimerization. PSMA dimers but not monomers displayed a native conformation and possessed high-level carboxypeptidase activity. A unique dimer-specific epitope was identified by using one of a panel of novel mAbs. When used to immunize animals, dimer but not monomer elicited antibodies that efficiently recognized PSMA-expressing tumor cells. These findings on PSMA structure and biology may have important implications for active and passive immunotherapy of prostate and other cancers.
Transabdominal near infrared oximetry of hypoxic stress in fetal sheep brain
in utero
Authors: Choe Regine , Durduran Turgut , Yu Guoqiang , Nijland Mark J. M. , Chance Britton , Yodh Arjun G. , Ramanujam Nirmala
Published: October 2003

The feasibility of transabdominal near-infrared (NIR) spectroscopy for detecting and quantifying fetal hypoxia
in utero
is demonstrated in a pregnant ewe model. A frequency domain NIR spectroscopy probe, consisting of two detectors and six sources operating at three wavelengths (675, 786, and 830 nm), was placed on the maternal abdomen directly above the fetal head. Fetal hypoxia was indirectly induced through occlusion of uterine blood flow for ≈3 min. NIR photon diffusion measurements were made during a baseline period, during hypoxia of the fetus, and during recovery. Fetal blood samples were drawn from the fetal brachial artery and jugular veins at several time points during the cycle. Seven hypoxic cycles were induced in a total of five pregnant ewes. The NIR measurements were analyzed by using a two-layer diffusion model to deconvolve the fetal blood saturation from that of the pregnant ewe. Fetal hypoxia was detected. Good agreement was found between fetal blood saturation determined by the transabdominal NIR method and arterial and venous fetal blood saturation quantified from fetal blood samples by using a hemoximeter.
Evidence that IgE molecules mediate a spectrum of effects on mast cell survival and activation via aggregation of the FcεRI
Authors: Kitaura Jiro , Song Jinming , Tsai Mindy , Asai Koichi , Maeda-Yamamoto Mari , Mocsai Attila , Kawakami Yuko , Liu Fu-Tong , Lowell Clifford A. , Barisas B. George , Galli Stephen J. , Kawakami Toshiaki
Published: October 2003

We demonstrate that binding of different IgE molecules (IgEs) to their receptor, FcεRI, induces a spectrum of activation events in the absence of a specific antigen and provide evidence that such activation reflects aggregation of FcεRI. Highly cytokinergic IgEs can efficiently induce production of cytokines and render mast cells resistant to apoptosis in an autocrine fashion, whereas poorly cytokinergic IgEs induce these effects inefficiently. Highly cytokinergic IgEs seem to induce more extensive FcεRI aggregation than do poorly cytokinergic IgEs, which leads to stronger mast cell activation and survival effects. These effects of both types of IgEs require Syk tyrosine kinase and can be inhibited by FcεRI disaggregation with monovalent hapten. In hybridoma-transplanted mice, mucosal mast cell numbers correlate with serum IgE levels. Therefore, survival effects of IgE could contribute to the pathogenesis of allergic disease.
Signature quantization
Authors: Guillemin Victor , Sternberg Shlomo , Weitsman Jonathan
Published: October 2003

We associate to the action of a compact Lie group
G
on a line bundle over a compact oriented even-dimensional manifold a virtual representation of
G
using a twisted version of the signature operator. We obtain analogues of various theorems in the more standard theory of geometric quantization.
A modulatory role for facial expressions in prosopagnosia
Authors: de Gelder Beatrice , Frissen Ilja , Barton Jason , Hadjikhani Nouchine
Published: October 2003

Brain-damaged patients experience difficulties in recognizing a face (prosopagnosics), but they can still recognize its expression. The dissociation between these two face-related skills has served as a keystone of models of face processing. We now report that the presence of a facial expression can influence face identification. For normal viewers, the presence of a facial expression influences performance negatively, whereas for prosopagnosic patients, it improves performance dramatically. Accordingly, although prosopagnosic patients show a failure to process the facial configuration in the interest of face identification, that ability returns when the face shows an emotional expression. Accompanying brain-imaging results indicate activation in brain areas (amygdala, superior temporal sulcus, parietal cortex) outside the occipitotemporal areas normally activated for face identification and lesioned in these patients. This finding suggests a modulatory role of these areas in face identification that is independent of occipitotemporal face areas.
Early phagosomes in dendritic cells form a cellular compartment sufficient for cross presentation of exogenous antigens
Authors: Ackerman Anne L. , Kyritsis Christoph , Tampé Robert , Cresswell Peter
Published: October 2003

Conventionally, MHC class I-restricted antigen (Ag) processing requires the action of the multimolecular peptide-loading complex within the endoplasmic reticulum (ER). Here we show that early phagosomes from human dendritic cells (DCs) contain the peptide-loading complex, incorporating MHC class I, β2microglobulin, transporter associated with Ag processing (TAP), calreticulin, tapasin, and ERp57. Antigenic peptides could be translocated into purified phagosomes by TAP and loaded onto cognate class I molecules, inducing their specific dissociation from the loading complex. Endoglycosidase H-sensitive class I molecules were detected at the DC cell surface, suggesting that these molecules traffic there directly from phagosomes. Macropinocytosis also allowed internalized soluble Ags access to an ER-like compartment containing the class I loading complex. Blockade of TAP by endocytosis of a soluble derivative of human cytomegalovirus protein US6 confirmed that, although retrotranslocation into the cytosol is critical for processing, efficient association of class I molecules with peptides derived from exogenous Ags occurs within a compartment directly accessible to internalized proteins. Together, this evidence suggests that early phagosomes and pinosomes facilitate cross presentation of exogenous Ags by DCs.
Branched aliphatic alkanes with quaternary substituted carbon atoms in modern and ancient geologic samples
Authors: Kenig Fabien , Simons Dirk-Jan H. , Crich David , Cowen James P. , Ventura Gregory T. , Rehbein-Khalily Tatiana , Brown Todd C. , Anderson Ken B.
Published: October 2003

A pseudohomologous series of branched aliphatic alkanes with a quaternary substituted carbon atom (BAQCs, specifically 2,2-dimethylalkanes and 3,3- and 5,5-diethylalkanes) were identified in warm (65°C) deep-sea hydrothermal waters and Late Cretaceous black shales. 5,5-Diethylalkanes were also observed in modern and Holocene marine shelf sediments and in shales spanning the last 800 million years of the geological record. The carbon number distribution of BAQCs indicates a biological origin. These compounds were observed but not identified in previous studies of 2.0 billion- to 2.2 billion-year-old metasediments and were commonly misidentified in other sediment samples, indicating that BAQCs are widespread in the geological record. The source organisms of BAQCs are unknown, but their paleobiogeographic distribution suggests that they have an affinity for sulfides and might be nonphotosynthetic sulfide oxidizers.
Reverse genetics with a full-length infectious cDNA of severe acute respiratory syndrome coronavirus
Authors: Yount Boyd , Curtis Kristopher M. , Fritz Elizabeth A. , Hensley Lisa E. , Jahrling Peter B. , Prentice Erik , Denison Mark R. , Geisbert Thomas W. , Baric Ralph S.
Published: October 2003

A previously undescribed coronavirus (CoV) is the etiologic agent responsible for severe acute respiratory syndrome (SARS). Using a panel of contiguous cDNAs that span the entire genome, we have assembled a full-length cDNA of the SARS-CoV Urbani strain, and have rescued molecularly cloned SARS viruses (infectious clone SARS-CoV) that contained the expected marker mutations inserted into the component clones. Recombinant viruses replicated as efficiently as WT virus and both were inhibited by treatment with the cysteine proteinase inhibitor (2S,3S)-transepoxysuccinyl-l-leucylamido-3-methylbutane ethyl ester. In addition, subgenomic transcripts were initiated from the consensus sequence ACGAAC in both the WT and infectious clone SARS-CoV. Availability of a SARS-CoV full-length cDNA provides a template for manipulation of the viral genome, allowing for the rapid and rational development and testing of candidate vaccines and therapeutics against this important human pathogen.
Hypothalamic malonyl-CoA as a mediator of feeding behavior
Authors: Hu Zhiyuan , Cha Seung Hun , Chohnan Shigeru , Lane M. Daniel
Published: October 2003

Previous studies showed that i.p. administration of C75, a potent inhibitor of fatty acid synthase (FAS), blocked fasting-induced up-regulation of orexigenic neuropeptides and down-regulation of anorexigenic neuropeptides in the hypothalami of mice. As a result, food intake and body weight were drastically reduced. Here we provide evidence supporting the hypothesis that hypothalamic malonyl-CoA, a substrate of FAS, is an indicator of global energy status and mediates the feeding behavior of mice. We use a sensitive recycling assay to quantify malonyl-CoA to show that the hypothalamic malonyl-CoA level is low in fasted mice and rapidly (≤2 h) increases (≈5-fold) on refeeding. Intracerebroventricular (i.c.v.) administration of C75 to fasted mice rapidly (≤2 h) increased (by 4-fold) hypothalamic malonyl-CoA and blocked feeding when the mice were presented with food. Moreover, prior i.c.v. administration of an acetyl-CoA carboxylase inhibitor, 5-(tetradecyloxy)-2-furoic acid, rapidly (although only partially) prevented the C75-induced rise of hypothalamic malonyl-CoA and prevented the C75-induced decrease of food intake. These effects correlated closely with the rapid (≤2 h) and reciprocal effects of i.c.v. C75 on the expression of hypothalamic orexigenic (NPY and AgRP) and anorexigenic (proopiomelanocortin) neuropeptide mRNAs. Previous results showing that C75 administered i.c.v. rapidly activates hypothalamic neurons of the arcuate and paraventricular nuclei are consistent with the results reported in this paper. Together these findings suggest that level of hypothalamic malonyl-CoA, which depends on the relative activities of acetyl-CoA carboxylase and FAS, is an indicator of energy status and mediates feeding behavior.
Exploiting luminescence spectroscopy to elucidate the interaction between sugar and a tryptophan residue in the lactose permease of
Escherichia coli
Authors: Vázquez-Ibar José Luis , Guan Lan , Svrakic Maja , Kaback H. Ronald
Published: October 2003

The crystal structure of the
Escherichia coli
lactose permease at 3.5 Å with a bound substrate has been reported recently. The structure reveals the sugar–protein contacts, which include hydrophobic stacking between the galactopyranosyl ring of substrate and the indole side chain of Trp-151, as proposed previously. The nature of this interaction is studied here by exploiting the luminescence properties of Trp-151 in a mutant devoid of other tryptophan residues. The following phenomena are observed. (
i
) The fluorescence emission spectrum of Trp-151 and fluorescence-quenching experiments with water-soluble quenchers demonstrate that Trp-151 is in a hydrophilic environment. (
ii
) Substrate binding leads to a blue shift in the emission spectrum and reduction in accessibility to polar quenchers, indicating that Trp-151 becomes less exposed to aqueous solvent. (
iii
) The phosphorescence spectrum of Trp-151 is red-shifted in the presence of substrate, indicating charge separation of the triplet state due to a direct stacking interaction between the galactopyranosyl and indole rings. The spectroscopic data fully complement the x-ray structure and demonstrate the feasibility of fluorescence spectroscopy for studying sugar–protein interactions.
Differential regulation of symmetry genes and the evolution of floral morphologies
Authors: Hileman Lena C. , Kramer Elena M. , Baum David A.
Published: October 2003

Shifts in flower symmetry have occurred frequently during the diversification of angiosperms, and it is thought that such shifts play important roles in plant–pollinator interactions. In the model developmental system
Antirrhinum majus
(snapdragon), the closely related genes
CYCLOIDEA
(
CYC
) and
DICHOTOMA
(
DICH
) are needed for the development of zygomorphic flowers and the determination of adaxial (dorsal) identity of floral organs, including adaxial stamen abortion and asymmetry of adaxial petals. However, it is not known whether these genes played a role in the divergence of species differing in flower morphology and pollination mode. We compared
A. majus
with a close relative,
Mohavea confertiflora
(desert ghost flower), which differs from
Antirrhinum
in corolla (petal) symmetry and pollination mode. In addition,
Mohavea
has undergone a homeotic-like transformation in stamen number relative to
Antirrhinum
, aborting the lateral and adaxial stamens during flower development. Here we show that the patterns of expression of
CYC
and
DICH
orthologs have shifted in concert with changes in floral morphology. Specifically, lateral stamen abortion in
Mohavea
is correlated with an expansion of
CYC
and
DICH
expression, and internal symmetry of
Mohavea
adaxial petals is correlated with a reduction in
DICH
expression during petal differentiation. We propose that changes in the pattern of
CYC
and
DICH
expression have contributed to the derived flower morphology of
Mohavea
and may reflect adaptations to a pollination strategy resulting from a mimetic relationship, linking the genetic basis for morphological evolution to the ecological context in which the morphology arose.
Probable extirpation of a breeding colony of Short-tailed Albatross (Phoebastria albatrus) on Bermuda by Pleistocene sea-level rise
Authors: Olson Storrs L. , Hearty Paul J.
Published: October 2003

Albatrosses (Diomedeidae) do not occur in the North Atlantic Ocean today except as vagrants, although five species were present in the early Pliocene. No fossil breeding sites of albatrosses were known previously. The timing of extinction of albatrosses in the North Atlantic was likewise unknown. Deposits that formed near present-day sea level along the southeastern shore of Bermuda contain remains of a former breeding colony and include intact eggshells and bones of embryos, juveniles, and adults of Short-tailed Albatross (Phoebastria albatrus), a critically endangered species now confined to a few islets in the northwestern Pacific Ocean. These deposits are correlated with the middle Pleistocene Lower Town Hill Formation, which at other sites have a radiometric age of ≈405,000 years ago. This equates with the marine isotope stage 11 interglacial, which culminated in a rise in sea-level to >+20 m. Bones of a juvenile Short-tailed Albatross were also found in beach deposits at +21.3 m from this same interglacial. We interpret the extirpation of albatrosses on Bermuda as probably resulting from lack of nesting sites protected from storm surges over the little emergent land that remained at the height of the marine isotope stage 11 sea level rise.
Localization and roles of Ski8p protein in Sordaria meiosis and delineation of three mechanistically distinct steps of meiotic homolog juxtaposition
Authors: Tessé Sophie , Storlazzi Aurora , Kleckner Nancy , Gargano Silvana , Zickler Denise
Published: October 2003

Ski8p is implicated in degradation of non-poly(A) and double-stranded RNA, and in meiotic DNA recombination. We have identified the
Sordaria macrospora
SKI8 gene. Ski8p is cytoplasmically localized in all vegetative and sexual cycle cells, and is nuclear localized, specifically in early-mid-meiotic prophase, in temporal correlation with Spo11p, the meiotic double-strand break (DSB) transesterase. Localizations of Ski8p and Spo11p are mutually interdependent.
ski8
mutants exhibit defects in vegetative growth, entry into the sexual program, and sporulation. Diverse meiotic defects, also seen in
spo11
mutants, are diagnostic of DSB absence, and they are restored by exogenous DSBs. These results suggest that Ski8p promotes meiotic DSB formation by acting directly within meiotic prophase chromosomes. Mutant phenotypes also divide meiotic homolog juxtaposition into three successive, mechanistically distinct steps; recognition, presynaptic alignment, and synapsis, which are distinguished by their differential dependence on DSBs.
A genetic lesion that arrests plasma cell homing to the bone marrow
Authors: Erickson Loren D. , Lin Ling-Li , Duan Biyan , Morel Laurence , Noelle Randolph J.
Published: October 2003

The coordinated regulation of chemokine responsiveness plays a critical role in the development of humoral immunity. After antigen challenge and B cell activation, the emerging plasma cells (PCs) undergo CXCL12-induced chemotaxis to the bone marrow, where they produce Ab and persist. Here we show that PCs, but not B cells or T cells from lupus-prone NZM mice, are deficient in CXCL12-induced migration. PC unresponsiveness to CXCL12 results in a marked accumulation of PCs in the spleen of mice, and a concordant decrease in bone marrow PCs. Unlike normal mice, in NZM mice, a majority of the splenic PCs are long-lived. This deficiency is a consequence of the genetic interactions of multiple systemic lupus erythematosus susceptibility loci.
Immunodominance among herpes simplex virus-specific CD8 T cells expressing a tissue-specific homing receptor
Authors: Koelle David M. , Liu Zhi , McClurkan Christopher L. , Cevallos Randal C. , Vieira Jeffrey , Hosken Nancy A. , Meseda Clement A. , Snow Devon C. , Wald Anna , Corey Lawrence
Published: October 2003

The study of immunodominance within microbe-specific CD8 T cell responses has been challenging. We used a previously undescribed approach to create unbiased panels of CD8 cytotoxic T lymphocyte clones specific for herpes simplex virus type 2, a pathogen with a complex genome encoding at least 85 polypeptides. Circulating herpes simplex virus type 2-specific cells were enriched and cloned after sorting for expression of the skin homing-associated receptor, cutaneous lymphocyte-associated antigen, bypassing restimulation with antigen. The specificity of the resultant cytotoxic clones was determined. Clonal frequencies were compared with each other and with the total number of cytotoxic clones. For each subject within the homing receptor-positive compartment, the CD8 cytotoxic response was dominated by T cells specific for only a few peptides. Previously undescribed antigens and epitopes in viral tegument, capsid, or scaffold proteins were immunodominant in some subjects. Clone enumeration analyses were confirmed in some subjects with dominance studies by using herpes simplex mutants, vaccinia recombinants, and/or enzyme-linked immune spots. We conclude that among circulating cells expressing a homing-associated receptor, during chronic herpes type 2 infection, the CD8 T cell response becomes quite focused despite the presence of many potential antigenic peptides.
Methylated DNA-binding domain 1 and methylpurine–DNA glycosylase link transcriptional repression and DNA repair in chromatin
Authors: Watanabe Sugiko , Ichimura Takaya , Fujita Naoyuki , Tsuruzoe Shu , Ohki Izuru , Shirakawa Masahiro , Kawasuji Michio , Nakao Mitsuyoshi
Published: October 2003

The methyl–CpG dinucleotide containing a symmetrical 5-methylcytosine (mC) is involved in gene regulation and genome stability. We report here that methylation-mediated transcriptional repressor methylated DNA-binding domain 1 (MBD1) interacts with methylpurine–DNA glycosylase (MPG), which excises damaged bases from substrate DNA. MPG itself actively represses transcription and has a synergistic effect on gene silencing together with MBD1. Chromatin immunoprecipitation analysis reveals the molecular movement of MBD1 and MPG
in vivo
: (
i
) The MBD1–MPG complex normally exists on the methylated gene promoter; (
ii
) treatment of cells with alkylating agent methylmethanesulfonate (MMS) induces the dissociation of MBD1 from the methylated promoter, and MPG is located on both methylated and unmethylated promoters; and (
iii
) after completion of the repair, the MBD1–MPG complex is restored on the methylated promoter. Mobility-shift and structural analyses show that the MBD of MBD1 binds a methyl–CpG pair (mCpG × mCpG) but not the methyl–CpG pair containing a single 7-methylguanine (N) (mCpG × mCpN) that is known as one of the major lesions caused by MMS. We further demonstrate that knockdown of MBD1 by specific small interfering RNAs significantly increases cell sensitivity to MMS. These data suggest that MBD1 cooperates with MPG for transcriptional repression and DNA repair. We hypothesize that MBD1 functions as a reservoir for MPG and senses the base damage in chromatin.
Brain-derived neurotrophic factor-dependent unmasking of “silent” synapses in the developing mouse barrel cortex
Authors: Itami Chiaki , Kimura Fumitaka , Kohno Tomoko , Matsuoka Masato , Ichikawa Masumi , Tsumoto Tadaharu , Nakamura Shun
Published: October 2003

Brain-derived neurotrophic factor (BDNF) is a critical modulator of central synaptic functions such as long-term potentiation in the hippocampal and visual cortex. Little is known, however, about its role in the development of excitatory glutamatergic synapsesin vivo. We investigated the development ofN-methyl-D-aspartate (NMDA) receptor (NMDAR)-only synapses (silent synapses) and found that silent synapses were prominent in acute thalamocortical brain slices from BDNF knockout mice even after the critical period. These synapses could be partially converted to α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-containing ones by adding back BDNF alone to the slice or fully converted to together with electric stimulation without affecting NMDAR transmission. Electric stimulation alone was ineffective under the BDNF knockout background. Postsynaptically applied TrkB kinase inhibitor or calcium-chelating reagent blocked this conversion. Furthermore, the AMPAR C-terminal peptides essential for interaction with PDZ proteins postsynaptically prevented the unmasking of silent synapses. These results suggest that endogenous BDNF and neuronal activity synergistically activate AMPAR trafficking into synaptic sites.
A subset of familial colorectal neoplasia kindreds linked to chromosome 9q22.2-31.2
Authors: Wiesner Georgia L. , Daley Denise , Lewis Susan , Ticknor Christine , Platzer Petra , Lutterbaugh James , MacMillen Melissa , Baliner Boris , Willis Joseph , Elston Robert C. , Markowitz Sanford D.
Published: October 2003

Colorectal cancer is the second most leading cause of cancer death among adult Americans. Two autosomal dominant hereditary forms of the disease, familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer, together account for perhaps 5% of all cases. However, in ≈20% of additional colon cancer cases, the affected individuals report a family history of colon cancer in a first-degree relative. Similar familial clusters of colon cancer and early-onset colon adenomas have also been reported. To determine whether such familial aggregations arise by chance or reflect a hereditary colon cancer susceptibility, we conducted a whole genome scan to test for genetic linkage in 53 kindreds in which two or more siblings were affected by age 65 or younger with colon cancer or with advanced colon adenomas that were >1 cm in size or that showed high-grade dysplasia. In this cohort we found genetic linkage of disease (
P
= 0.00045) to chromosomal region 9q22.2-31.2 in a pattern consistent with autosomal dominant disease alleles. These data suggest that a single locus can contribute to disease susceptibility in a subset of patients with nonsyndromic forms of familial colorectal neoplasia.
Trace but not delay fear conditioning requires attention and the anterior cingulate cortex
Authors: Han C. J. , O'Tuathaigh Colm M. , van Trigt Laurent , Quinn Jennifer J. , Fanselow Michael S. , Mongeau Raymond , Koch Christof , Anderson David J.
Published: October 2003

Higher cognitive functions such as attention have been difficult to model in genetically tractable organisms. In humans, attention-distracting stimuli interfere with trace but not delay conditioning, two forms of associative learning. Attention has also been correlated with activation of anterior cingulate cortex (ACC), but its functional significance is unclear. Here we show that a visual distractor interferes selectively with trace but not delay auditory fear conditioning in mice. Trace conditioning is associated with increased neuronal activity in ACC, as assayed by relative levels ofc-fosexpression, and is selectively impaired by lesions of this structure. The effects of the ACC lesions are unlikely to be caused by indirect impairment of the hippocampus, which is required for mnemonic aspects of trace conditioning. These data suggest that trace conditioning may be useful for studying neural substrates of attention in mice, and implicate the ACC as one such substrate.
Genomewide screening for fusogenic human endogenous retrovirus envelopes identifies syncytin 2, a gene conserved on primate evolution
Authors: Blaise Sandra , de Parseval Nathalie , Bénit Laurence , Heidmann Thierry
Published: October 2003

Screening human sequence databases for endogenous retroviral elements with coding envelope genes has revealed 16 candidate genes that we assayed for their fusogenic properties. All 16 genes were cloned in a eukaryotic expression vector and assayed for cell–cell fusion by using a large panel of mammalian cells in transient transfection assays. Fusion was observed for two human endogenous retrovirus (HERV) envelopes, the previously characterized HERV-W envelope, also called syncytin, and a previously uncharacterized gene from the HERV-FRD family. Cells prone to env-mediated fusion were different for the two envelopes, indicating different receptor usage. A search for the FRD
env
gene in primates indicated that the corresponding proviral element is present in all simians, from New World monkeys to humans, being absent only in prosimians. Cloning of the corresponding
env
genes in simians disclosed conservation of the fully coding status of the gene, and most remarkably, conservation of its fusogenic property. Finally, a Northern blot analysis for the expression of the FRD family among a series of human tissues demonstrated specific expression in the placenta, as previously demonstrated for the other fusogenic human envelope of the HERV-W family. Altogether, the present data have identified a previously uncharacterized envelope (that we propose to name syncytin 2 after renaming syncytin as syncytin 1) with a potential role in placenta formation, and the identification of the complete set of retroviral envelopes with fusogenic properties now allows a definite analysis of the possible role of HERV in this physiological process, via classical genetic approaches.
mTor is required for hypertrophy of Pten-deficient neuronal soma
in vivo
Authors: Kwon Chang-Hyuk , Zhu Xiaoyan , Zhang Junyuan , Baker Suzanne J.
Published: October 2003

The mechanisms that regulate mammalian cell size during development and homeostatic maintenance are poorly understood. The tumor suppressor Pten is required for correct maintenance of mammalian neuronal soma size. Selective inactivation of
Pten
in postnatal granule neurons of the cerebellum and dentate gyrus in mouse causes cell-autonomous hypertrophy as well as more complex phenotypes, including progressive macrocephaly, seizures, and premature death. To determine the contribution of mTor signaling to Pten-mediated growth regulation in the mammalian nervous system, we treated
Pten
conditional knockout mice with CCI-779, a specific mTor inhibitor. mTor inhibition decreased the seizure frequency and death rate in
Pten
mutant mice, prevented the increase in Pten-deficient neuronal soma size in young mice, and reversed neuronal soma enlargement in adult mice. mTor inhibition did not decrease the size of wild-type adult neurons. Thus, mTor is required for neuronal hypertrophy downstream of Pten deficiency, but is not required for maintenance of normal neuronal soma size. mTOR inhibitors may be useful therapeutic agents for diseases in brain resulting from PTEN deficiency such as Lhermitte–Duclos disease or glioblastoma multiforme.
The complexity of alternative splicing of
hagoromo
mRNAs is increased in an explosively speciated lineage in East African cichlids
Authors: Terai Yohey , Morikawa Naoko , Kawakami Koichi , Okada Norihiro
Published: October 2003

The adaptive radiation of cichlid fishes in the lakes of East Africa is a prime example of speciation. The choice of cichlid mates on the basis of a variety of coloration represents a potential basis for speciation that led to adaptive radiation. Here, we characterize the cichlid homolog of the zebrafish
hagoromo
(
hag
) gene that was recently cloned and characterized from a pigmentation mutant. Although only one
hag
mRNA was reported in zebrafish, cichlids express nine different
hag
mRNAs resulting from alternative splicing. The
hag
mRNAs are expressed between the myotome and the epidermis where pigment cells are located, suggesting the cichlid
hag
gene is involved in pigmentation. The
hag
mRNA splicing pattern does not fluctuate among individuals from each of two species, suggesting that alternative splice site choice is fixed within species. Furthermore, cichlids in lineages that underwent explosive speciation expressed a greater variety of
hag
mRNAs than those in lineages that did not undergo such a degree of speciation, suggesting that species in the explosively speciated lineage acquired a complex regulatory mechanism of alternative splicing over a very short evolutionary period. Here, we provide an example in which alternative splicing may play a role in mate choice, leading to cichlid speciation through diversification of gene function by production of multiple mRNAs from a single gene.
Synchronous coadaptation in an ancient case of herbivory
Authors: Becerra Judith X.
Published: October 2003

Coevolution has long been considered a major force leading to the adaptive radiation and diversification of insects and plants. A fundamental aspect of coevolution is that adaptations and counteradaptations interlace in time. A discordant origin of traits long before or after the origin of the putative coevolutionary selective pressure must be attributed to other evolutionary processes. Despite the importance of this distinction to our understanding of coevolution, the macroevolutionary tempo of innovation in plant defenses and insect counterdefenses has not been documented. Molecular clocks for a lineage of chrysomelid beetles of the genus
Blepharida
and their Burseraceae hosts were independently calibrated. Results show that these plants' defenses and the insect's counterdefensive feeding traits evolved roughly in synchrony, providing macroevolutionary confirmation of synchronous plant–herbivore coadaptation. The association between these two groups of organisms was determined to be about 112 million years old, the oldest age so far for a specialized plant–herbivore association.
Conformation-dependent hydrophobic photolabeling of the nicotinic receptor: Electrophysiology-coordinated photochemistry and mass spectrometry
Authors: Leite John F. , Blanton Michael P. , Shahgholi Mona , Dougherty Dennis A. , Lester Henry A.
Published: October 2003

We characterized the differential accessibility of the nicotinic acetylcholine receptor α1 subunit in the open, closed, and desensitized states by using electrophysiology-coordinated photolabeling by several lipophilic probes followed by mass spectrometric analysis. Voltage-clamped oocytes expressing receptors were preincubated with one of the lipophilic probes and were continually exposed to acetylcholine; UV irradiation was applied during 500-ms pulses to + 40 or to -140 mV (which produced closed or ≈50% open receptors, respectively). In the open state, there was specific probe incorporation within the N-terminal domain at residues that align with the β8–β9 loop of the acetylcholine-binding protein. In the closed state, probe incorporation was identified at several sites of the N-terminal domain within the conserved cysteine loop (residues 128–142), the cytoplasmic loop (M3–M4), and M4. The labeling pattern in the M4 region is consistent with previous results, further defining the lipid-exposed face of this transmembrane α-helix. These results show regions within the N-terminal domain that are involved in gating-dependent conformational shifts, confirm that the cysteine loop resides at or near the protein-membrane interface, and show that segments of the M3–M4 loop are near to the lipid bilayer.
Coloration strategies in peacock feathers
Authors: Zi Jian , Yu Xindi , Li Yizhou , Hu Xinhua , Xu Chun , Wang Xingjun , Liu Xiaohan , Fu Rongtang
Published: October 2003

We report the mechanism of color production in peacock feathers. We find that the cortex in differently colored barbules, which contains a 2D photonic-crystal structure, is responsible for coloration. Simulations reveal that the photonic-crystal structure possesses a partial photonic bandgap along the direction normal to the cortex surface, for frequencies within which light is strongly reflected. Coloration strategies in peacock feathers are very ingenious and simple: controlling the lattice constant and the number of periods in the photonic-crystal structure. Varying the lattice constant produces diversified colors. The reduction of the number of periods brings additional colors, causing mixed coloration.
Cyclothiazide potently inhibits γ-aminobutyric acid type A receptors in addition to enhancing glutamate responses
Authors: Deng Lunbin , Chen Gong
Published: October 2003

Ionotropic glutamate and γ-aminobutyric acid type A (GABA
A
) receptors mediate critical excitatory and inhibitory actions in the brain. Cyclothiazide (CTZ) is well known for its effect of enhancing glutamatergic transmission and is widely used as a blocker for α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptor desensitization. Here, we report that in addition to its action on AMPA receptors, CTZ also exerts a powerful but opposite effect on GABA
A
receptors. We found that CTZ reversibly inhibited both evoked and spontaneous inhibitory postsynaptic currents, as well as GABA application-induced membrane currents, in a dose-dependent manner. Single-channel analyses revealed further that CTZ greatly reduced the open probability of GABA
A
receptor channels. These results demonstrate that CTZ interacts with both glutamate and GABA
A
receptors and shifts the excitation–inhibition balance in the brain by two independent mechanisms. Understanding the molecular mechanism of this double-faceted drug–receptor interaction may help in designing new therapies for neurological diseases.
Multiple, recurring origins of aposematism and diet specialization in poison frogs
Authors: Santos Juan Carlos , Coloma Luis A. , Cannatella David C.
Published: October 2003

Aposematism is the association, in a prey organism, of the presence of a warning signal with unprofitability to predators. The origin of aposematism is puzzling, because of its predicted low probability of establishment in a population due to the prey's increased conspicuousness. Aposematism is a widespread trait in invertebrate taxa, but, in vertebrates, it is mostly evident in amphibians, reptiles, and fishes. Poison frogs (Dendrobatidae) are one of the most well known examples of the co-occurrence of warning coloration and toxicity. This monophyletic group of mostly diurnal leaf-litter Neotropical anurans has both toxic/colorful and palatable/cryptic species. Previous studies suggested a single origin of toxicity and warning coloration, dividing the family in two discrete groups of primitively cryptic and more derived aposematic frogs. Recent molecular phylogenetic analyses using mostly aposematic taxa supported this conclusion and proposed a single tandem origin of toxicity and conspicuous warning coloration. By using expanded taxon and character sampling, we reexamined the phylogenetic correlation between the origins of toxicity and warning coloration. At least four or five independent origins of aposematism have occurred within poison frogs; by using simulations, we rejected hypotheses of one, two, or three origins of aposematism (
P
< 0.002). We also found that diet specialization is linked with the evolution of aposematism. Specialization on prey, such as ants and termites, may have evolved independently at least two times.
Evolution of eusociality and the soldier caste in termites: Influence of intraspecific competition and accelerated inheritance
Authors: Thorne Barbara L. , Breisch Nancy L. , Muscedere Mario L.
Published: October 2003

We present new hypotheses and report experimental evidence for powerful selective forces impelling the evolution of both eusociality and the soldier caste in termites. Termite ancestors likely had a nesting and developmental life history similar to that of the living family Termopsidae, in which foraging does not occur outside the host wood, and nonsoldier helpers retain lifelong options for differentiation into reproductives. A local neighborhood of families that live exclusively within a limited resource results in interactions between conspecific colonies, high mortality of founding reproductives, and opportunities for accelerated inheritance of the nest and population by offspring that differentiate into nondispersing neotenic reproductives. In addition, fertile reproductive soldiers, a type of neotenic previously considered rare and docile, frequently develop in this intraspecific competitive context. They can be highly aggressive in subsequent interactions, supporting the hypothesis that intercolonial battles influenced the evolution of modern sterile termite soldier weaponry and behaviors.
Requirement for the TIE family of receptor tyrosine kinases in adult but not fetal hematopoiesis
Authors: Puri Mira C. , Bernstein Alan
Published: October 2003

In mammals, the continuous production of hematopoietic cells (HCs) is sustained by a small number of hematopoietic stem cells (HSCs) residing in the bone marrow. Early HSC activity arises in the aorta-gonad mesonephros region, within cells localized to the ventral floor of the major blood vessels, suggesting that the first HSCs may be derived from cells capable of giving rise to the hematopoietic system and to the endothelial cells of the vasculature. TIE1 (TIE) and TIE2 (TEK) are related receptor tyrosine kinases with an embryonic expression pattern in endothelial cells, their precursors, and HCs, suggestive of a role in the divergence and function of both lineages. Indeed, gene targeting approaches have shown that TIE1, TIE2, and ligands for TIE2, the angiopoietins, are essential for vascular development and maintenance. To explore possible roles for these receptors in HCs, we have examined the ability of embryonic cells lacking both TIE1 and TIE2 to contribute to developmental and adult hematopoiesis by generating chimeric animals between normal embryonic cells and cells lacking these receptors. We show here that TIE receptors are not required for differentiation and proliferation of definitive hematopoietic lineages in the embryo and fetus; surprisingly, however, these receptors are specifically required during postnatal bone marrow hematopoiesis.
Two-photon imaging of capillary blood flow in olfactory bulb glomeruli
Authors: Chaigneau Emmanuelle , Oheim Martin , Audinat Etienne , Charpak Serge
Published: October 2003

Analysis of the spatiotemporal coupling between neuronal activity and cerebral blood flow requires the precise measurement of the dynamics of RBC flow in individual capillaries that irrigate activated neurons. Here, we use two-photon microscopy
in vivo
to image individual RBCs in glomerular capillaries in the rat dorsal olfactory bulb. We find that odor stimulation evokes capillary vascular responses that are odorant- and glomerulus-specific. These responses consist of increases as well as decreases in RBC flow, both resulting from independent changes in RBC velocity or linear density. Finally, measuring RBC flow with micrometer spatial resolution and millisecond temporal resolution, we demonstrate that, in olfactory bulb superficial layers, capillary vascular responses precisely outline regions of synaptic activation.
Damped elastic recoil of the titin spring in myofibrils of human myocardium
Authors: Opitz Christiane A. , Kulke Michael , Leake Mark C. , Neagoe Ciprian , Hinssen Horst , Hajjar Roger J. , Linke Wolfgang A.
Published: October 2003

The giant protein titin functions as a molecular spring in muscle and is responsible for most of the passive tension of myocardium. Because the titin spring is extended during diastolic stretch, it will recoil elastically during systole and potentially may influence the overall shortening behavior of cardiac muscle. Here, titin elastic recoil was quantified in single human heart myofibrils by using a high-speed charge-coupled device-line camera and a nanonewtonrange force sensor. Application of a slack-test protocol revealed that the passive shortening velocity (
V
p
) of nonactivated cardiomyofibrils depends on: (
i
) initial sarcomere length, (
ii
) release-step amplitude, and (
iii
) temperature. Selective digestion of titin, with low doses of trypsin, decelerated myofibrillar passive recoil and eventually stopped it. Selective extraction of actin filaments with a Ca
2+
-independent gelsolin fragment greatly reduced the dependency of
V
p
on release-step size and temperature. These results are explained by the presence of viscous forces opposing myofibrillar passive recoil that are caused mainly by weak actin–titin interactions. Thus,
V
p
is determined by two distinct factors: titin elastic recoil and internal viscous drag forces. The recoil could be modeled as that of a damped entropic spring consisting of independent worm-like chains. The functional importance of myofibrillar elastic recoil was addressed by comparing instantaneous
V
p
to unloaded shortening velocity, which was measured in demembranated, fully Ca
2+
-activated, human cardiac fibers. Titin-driven passive recoil was much faster than active unloaded shortening velocity in early phases of isotonic contraction. Damped myofibrillar elastic recoil could help accelerate active contraction speed of human myocardium during early systolic shortening.
Alu elements and hominid phylogenetics
Authors: Salem Abdel-Halim , Ray David A. , Xing Jinchuan , Callinan Pauline A. , Myers Jeremy S. , Hedges Dale J. , Garber Randall K. , Witherspoon David J. , Jorde Lynn B. , Batzer Mark A.
Published: October 2003

Alu elements have inserted in primate genomes throughout the evolution of the order. One particular Alu lineage (Ye) began amplifying relatively early in hominid evolution and continued propagating at a low level as many of its members are found in a variety of hominid genomes. This study represents the first conclusive application of short interspersed elements, which are considered nearly homoplasy-free, to elucidate the phylogeny of hominids. Phylogenetic analysis of Alu Ye5 elements and elements from several other subfamilies reveals high levels of support for monophyly of Hominidae, tribe Hominini and subtribe Hominina. Here we present the strongest evidence reported to date for a sister relationship between humans and chimpanzees while clearly distinguishing the chimpanzee and human lineages.
HIV-1 in genital tract and plasma of women: Compartmentalization of viral sequences, coreceptor usage, and glycosylation
Authors: Kemal Kimdar Sherefa , Foley Brian , Burger Harold , Anastos Kathryn , Minkoff Howard , Kitchen Christina , Philpott Sean M. , Gao Wei , Robison Esther , Holman Susan , Dehner Carolyn , Beck Suzanne , Meyer William A. , Landay Alan , Kovacs Andrea , Bremer James , Weiser Barbara
Published: October 2003

Worldwide, 90% of HIV-1 infections are transmitted heterosexually. Because the genital mucosa are the sites of initial contact with HIV-1 for most exposed individuals, study of the virus from the genital tract is critical for the development of vaccines and therapeutics. Previous analyses of HIV-1 in various tissues have documented compartmentalization of viral genomes. Whether compartmentalization was associated with viral phenotypic differences or immune status, however, was not well understood. We compared HIV-1 gp120
env
sequences from the genital tract and plasma of 12 women. Eight women displayed compartmentalized HIV-1 RNA genomes, with viral sequences from each site that were clearly discrete, yet phylogenetically related. The remaining four exhibited
env
sequences that were intermingled between the two sites. Women with compartmentalized HIV-1 genomes had higher CD4
+
cell counts than those displaying intermingled strains (
P
= 0.02). Intrapatient HIV-1 recombinants comprising sequences that were characteristic of both sites were identified. We next compared viral phenotypes in each compartment. HIV-1 coreceptor usage was often compartmentalized (
P
≤ 0.01). The number of N-linked glycosylation sites, associated with neutralization resistance, also differed between compartments (
P
< 0.01). Furthermore, disparities between the density of gp120 glycosylations in each compartment correlated with higher CD4
+
counts (
P
= 0.03). These data demonstrate that the genital tract and plasma can harbor populations of replicating HIV-1 with different phenotypes. The association of higher CD4
+
cell counts with compartmentalization of viral genomes and density of gp120 glycosylations suggests that the immune response influences the development of viral genotypes in each compartment. These findings are relevant to the prevention and control of HIV-1 infection.
Genetic requirements for mycobacterial survival during infection
Authors: Sassetti Christopher M. , Rubin Eric J.
Published: October 2003

Despite the importance of tuberculosis as a public health problem, we know relatively little about the molecular mechanisms used by the causative organism,Mycobacterium tuberculosis, to persist in the host. To define these mechanisms, we have mutated virtually every nonessential gene ofM. tuberculosisand determined the effect disrupting each gene on the growth rate of this pathogen during infection. A total of 194 genes that are specifically required for mycobacterial growthin vivowere identified. The behavior of these mutants provides a detailed view of the changing environment that the bacterium encounters as infection proceeds. A surprisingly large fraction of these genes are unique to mycobacteria and closely related species, indicating that many of the strategies used by this unusual group of organisms are fundamentally different from other pathogens.