bluuebunny/crossref_metadata_2025 huggingface dataset:
Cytotoxic T lymphocytes and viral turnover in HIV type 1 infection
Authors: Klenerman Paul , Phillips Rodney E. , Rinaldo Charles R. , Wahl Linda M. , Ogg Graham , May Robert M. , McMichael Andrew J. , Nowak Martin A.
Published: July 2002

To understand the role of the immune system in limiting HIV type 1 replication, it is critical to know to what extent the rapid turnover of productively infected cells is caused by viral cytopathicity or by immune-mediated lysis. We show that uncultured peripheral blood mononuclear cells of many patients contain cytotoxic T lymphocytes (CTL) that lyse target cells—at plausible peripheral blood mononuclear cell-to-target ratios—with half-lives of less than 1 day. In 23 patients with CD4 counts ranging from 10 to 900 per μl, the average rate of CTL-mediated lysis corresponds to a target cell half-life of 0.7 day. We develop mathematical models to calculate the turnover rate of infected cells subjected to immune-mediated lysis and viral cytopathicity and to estimate the fraction of cells that are killed by CTL as opposed to virus. The models provide new interpretations of drug treatment dynamics and explain why the observed rate of virus decline is roughly constant for different patients. We conclude that in HIV type 1 infection, CTL-mediated lysis can reduce virus load by limiting virus production, with small effects on the half-life of infected cells.
Integration of circadian and phototransduction pathways in the network controlling
CAB
gene transcription in
Arabidopsis
Authors: Millar Andrew J. , Kay Steve A.
Published: July 2002

The transcription of
CAB
genes, encoding the
c
hlorophyll
a
/b-
b
inding
proteins, is rapidly induced in dark-grown
Arabidopsis
seedlings following a light pulse. The transient induction is followed
by several cycles of a circadian rhythm. Seedlings transferred to
continuous light are known to exhibit a robust circadian rhythm of
CAB
expression. The precise waveform of
CAB
expression in light–dark cycles, however, reflects
a regulatory network that integrates information from photoreceptors,
from the circadian clock and possibly from a developmental program. We
have used the luciferase reporter system to investigate
CAB
expression with high time resolution. We demonstrate
that
CAB
expression in light-grown plants exhibits a
transient induction following light onset, similar to the response in
dark-grown seedlings. The circadian rhythm modulates the magnitude and
the kinetics of the response to light, such that the
CAB
promoter is not light responsive during the subjective night. A
signaling pathway from the circadian oscillator must therefore
antagonize the phototransduction pathways controlling the
CAB
promoter. We have further demonstrated that the
phase of maximal
CAB
expression is delayed in
light–dark cycles with long photoperiods, due to the entrainment of
the circadian oscillator. Under short photoperiods, this pattern of
entrainment ensures that dawn coincides with a phase of high light
responsiveness, whereas under long photoperiods, the light response at
dawn is reduced.
Factor XII-induced mitogenesis is mediated via a distinct signal transduction pathway that activates a mitogen-activated protein kinase.
Authors: Gordon E M , Venkatesan N , Salazar R , Tang H , Schmeidler-Sapiro K , Buckley S , Warburton D , Hall F L
Published: July 2002

Clotting factor XII (Hageman factor) contains epidermal growth factor (EGF)-homologous domains and is reported to be a potent mitogen for human hepatoma (HepG2) cells. In this study, we tested whether factor XII exhibits growth factor activity on several other EGF-sensitive target cells, including fetal hepatocytes, endothelial cells, alveolar type II cells, and aortic smooth muscle cells. We found that factor XII significantly enhanced [3H]thymidine incorporation in aortic smooth muscle cells (SMCs) and all other cells tested. Tyrphostin, a growth factor receptor/tyrosine kinase antagonist, inhibited both EGF- and factor XII-induced responses. However, differences in the levels of magnitude of DNA synthesis, the observed synergism between EGF and factor XII, and the differential sensitivity to tyrphostin suggest that the EGF receptor and the factor XII receptor may be nonidentical. The factor XII-induced mitogenic response was achieved at concentrations that were 1/10th the physiologic range for the circulating factor and was reduced by popcorn inhibitor, a specific factor XII protease inhibitor. Treatment of aortic SMCs with factor XII, as well as activated factor XII, resulted in a rapid and transient activation of a mitogen-activated/extracellular signal-regulated protein kinase with peak activity/tyrosine phosphorylation observed at 5 to 10 min of exposure. Taken together, these data (i) confirm that clotting factor XII functions as a mitogenic growth factor and (ii) demonstrate that factor XII activates a signal transduction pathway, which includes a mitogen-activated protein kinase.
Pax3 modulates expression of the c-Met receptor during limb muscle development.
Authors: Epstein J A , Shapiro D N , Cheng J , Lam P Y , Maas R L
Published: July 2002

Pax3 is a transcription factor whose expression has been used as a marker of myogenic precursor cells arising in the lateral somite destined to migrate to and populate the limb musculature. Accruing evidence indicates that the embryologic origins of axial and appendicular muscles are distinct, and limb muscle abnormalities in both mice and humans harboring Pax3 mutations support this distinction. The mechanisms by which Pax3 affects limb muscle development are unknown. The tyrosine kinase receptor for hepatocyte growth factor/scatter factor encoded by the c-met protooncogene is also expressed in limb muscle progenitors and, like Pax-3, is required in the mouse for limb muscle development. Here, we show that c-met expression is markedly reduced in the lateral dermomyotome of Splotch embryos lacking Pax3. We show that Pax3 can stimulate c-met expression in cultured cells, and we identify a potential Pax3 binding site in the human c-MET promoter that may contribute to direct transcriptional regulation. In addition, we have found that several cell lines derived from patients with rhabdomyosarcomas caused by a t(2;13) chromosomal translocation activating PAX3 express c-MET, whereas those rhabdomyosarcoma cell lines examined without the translocation do not. These results are consistent with a model in which Pax3 modulates c-met expression in the lateral dermomyotome, a function that is required for the appropriate migration of these myogenic precursors to the limb where the ligand for c-met (hepatocyte growth factor/scatter factor) is expressed at high levels.
E2-C, a cyclin-selective ubiquitin carrier protein required for the destruction of mitotic cyclins.
Authors: Aristarkhov A , Eytan E , Moghe A , Admon A , Hershko A , Ruderman J V
Published: July 2002

Ubiquitin-dependent proteolysis of the mitotic cyclins A and B is required for the completion of mitosis and entry into the next cell cycle. This process is catalyzed by the cyclosome, an approximately 22S particle that contains a cyclin-selective ubiquitin ligase activity, E3-C, that requires a cyclin-selective ubiquitin carrier protein (UBC) E2-C. Here we report the purification and cloning of E2-C from clam oocytes. The deduced amino acid sequence of E2-C indicates that it is a new UBC family member. Bacterially expressed recombinant E2-C is active in in vitro cyclin ubiquitination assays, where it exhibits the same substrate specificities seen with native E2-C. These results demonstrate that E2-C is not a homolog of UBC4 or UBC9, proteins previously suggested to be involved in cyclin ubiquitination, but is a new UBC family member with unique properties.
A natural classification of the basic helix–loop–helix class of transcription factors
Authors: Atchley William R. , Fitch Walter M.
Published: July 2002

A natural (evolutionary) classification is provided for 242 basic helix–loop–helix (bHLH) motif-containing proteins. Phylogenetic analyses of amino acid sequences describe the patterns of evolutionary change within the motif and delimit evolutionary lineages. These evolutionary lineages represent well known functional groups of proteins and can be further arranged into five groups based on binding to DNA at the hexanucleotide E-box, the amino acid patterns in other components of the motif, and the presence/absence of a leucine zipper. The hypothesized ancestral amino acid sequence for the bHLH transcription factor family is given together with the ancestral sequences of the subgroups. It is suggested that bHLH proteins containing a leucine zipper are not a natural, monophyletic group.
Axial rotation of sliding actin filaments revealed by single-fluorophore imaging
Authors: Sase Ichiro , Miyata Hidetake , Ishiwata Shin’ichi , Kinosita Kazuhiko
Published: July 2002

In the actomyosin motor, myosin slides along an actin filament that has a helical structure with a pitch of ≈72 nm. Whether myosin precisely follows this helical track is an unanswered question bearing directly on the motor mechanism. Here, axial rotation of actin filaments sliding over myosin molecules fixed on a glass surface was visualized through fluorescence polarization imaging of individual tetramethylrhodamine fluorophores sparsely bound to the filaments. The filaments underwent one revolution per sliding distance of ≈1 μm, which is much greater than the 72 nm pitch. Thus, myosin does not “walk” on the helical array of actin protomers; rather it “runs,” skipping many protomers. Possible mechanisms involving sequential interaction of myosin with successive actin protomers are ruled out at least for the preparation described here in which the actin filaments ran rather slowly compared with other
in vitro
systems. The result also indicates that each “kick” of myosin is primarily along the axis of the actin filament. The successful, real-time observation of the changes in the orientation of a single fluorophore opens the possibility of detecting a conformational change(s) of a single protein molecule at the moment it functions.
Cooperation of
Pax2
and
Pax5
in midbrain and cerebellum development
Authors: Urbánek Pavel , Fetka Ingrid , Meisler Miriam H. , Busslinger Meinrad
Published: July 2002

Midbrain and cerebellum development depends on an organizing center that is located at the midbrain–hindbrain junction of the vertebrate embryo. Expression of the two closely related transcription factors Pax2 and Pax5 overlaps spatially and temporally in this region of the developing central nervous system. To study a possible interaction of these transcription factors in midbrain and cerebellum patterning, we have generated
Pax5
,
Krd
double mutant mice. The transgene-induced
Krd
mutation corresponds to an ≈7-centimorgan chromosome 19 deletion that eliminates the entire
Pax2
locus. The heterozygous
Krd
mutation deleting one
Pax2
allele had no effect on midbrain and cerebellum development. Moreover, only minor developmental defects were previously observed at the midline of the inferior colliculus and anterior cerebellum in mice that were homozygous for a targeted
Pax5
mutation. Similar morphological alterations were observed in 80% of all compound heterozygous
Pax5
(+/−)
Krd
(+/−) mice. However, in the remaining 20% of compound heterozygotes, the inferior colliculi were missing, and the vermis of the cerebellum was severely disrupted due to the failure of the cerebellar primordia to fuse at the midline. Inactivation of the second
Pax5
allele in
Pax5
(−/−)
Krd
(+/−) mice resulted in complete loss of the posterior midbrain and cerebellum, as the tissue originating from the midbrain–hindbrain boundary region was deleted in the embryo as early as day 9.5. On the basis of these data, we propose that the cooperation of Pax2 and Pax5 is essential for normal functioning of the organizing center at the midbrain–hindbrain junction.
Cilia internal mechanism and metachronal coordination as the result of hydrodynamical coupling
Authors: Gueron Shay , Levit-Gurevich Konstantin , Liron Nadav , Blum Jacob J.
Published: July 2002

We present a simple but realistic model for the internal bend-generating mechanism of cilia, using parameters obtained from the analysis of data of the beat of a single cilium, and incorporate it into a recently developed dynamical model. Comparing the results to experimental data for two-dimensional beats, we demonstrate that the model captures the essential features of the motion, including many properties that are not built in explicitly. The beat pattern and frequency change in response to increased viscosity and the presence of neighboring cilia in a realistic fashion. Using the model, we are able to investigate multicilia configurations such as rows of cilia and two-dimensional arrays of cilia. When two adjacent model cilia start beating at different phase, they synchronize within two cycles, as observed in experiments in which two flagella beating out of phase are brought close together. Examination of various multicilia configurations shows that metachronal patterns (i.e., beats with a constant phase difference between neighboring cilia) evolve autonomously. This provides modeling evidence in support of the conjecture that metachronism may occur as a self-organized phenomenon due to hydrodynamical interactions between the cilia.
Molecular evidence that echiurans and pogonophorans are derived annelids
Authors: McHugh Damhnait
Published: July 2002

The Annelida, which includes the polychaetes and the clitellates, has long held the taxonomic rank of phylum. The unsegmented, mud-dwelling echiuran spoon worms and the gutless, deep-sea pogonophoran tube worms (including vestimentiferans) share several embryological and morphological features with annelids, but each group also has been considered as a separate metazoan phylum based on the unique characters each group displays. Phylogenetic analyses of DNA sequences from the nuclear gene elongation factor-1α place echiurans and pogonophorans within the Annelida. This result, indicating the derived loss of segmentation in echiurans, has profound implications for our understanding of the evolution of metazoan body plans and challenges the traditional view of the phylum-level diversity and evolutionary relationships of protostome worms.
Hypoxia-inducible factor-1 modulates gene expression in solid tumors and influences both angiogenesis and tumor growth
Authors: Maxwell P. H. , Dachs G. U. , Gleadle J. M. , Nicholls L. G. , Harris A. L. , Stratford I. J. , Hankinson O. , Pugh C. W. , Ratcliffe P. J.
Published: July 2002

Recent studies of tissue culture cells have defined a widespread system of oxygen-regulated gene expression based on the activation of a heterodimeric transcription factor termed hypoxia-inducible factor-1 (HIF-1). To determine whether the HIF-1 transcriptional response is activated within solid tumors and to define the consequences, we have studied tumor xenografts of a set of hepatoma (Hepa-1) cells that are wild type (wt), deficient (c4), and revertant (Rc4) for an obligatory component of the HIF-1 heterodimer, HIF-1β. Because HIF-1β is also essential for the xenobiotic response (in which it is termed the aryl hydrocarbon receptor nuclear translocator), we also studied c31 cells, which have a different defect in the xenobiotic response and form the HIF-1 complex normally. Two genes that show different degrees of HIF-1-dependent hypoxia-inducible expression in cell culture were selected for analysis—the glucose transporter, GLUT3, and vascular endothelial growth factor (VEGF).
In situ
hybridization showed intense focal induction of gene expression in tumors derived from wt, Rc4, and c31 cells, which was reduced (VEGF) or not seen (GLUT3) in those derived from c4 cells. In association with these changes, tumors of c4 cells had reduced vascularity and grew more slowly. These findings show that HIF-1 activation occurs in hypoxic regions of tumors and demonstrate a major influence on gene expression, tumor angiogenesis, and growth.
Inheritance, gene expression, and lignin characterization in a mutant pine deficient in cinnamyl alcohol dehydrogenase
Authors: MacKay John J. , O’Malley David M. , Presnell Timothy , Booker Fitzgerald L. , Campbell Malcolm M. , Whetten Ross W. , Sederoff Ronald R.
Published: July 2002

We have discovered a mutant loblolly pine (
Pinus taeda
L.) in which expression of the gene encoding cinnamyl alcohol dehydrogenase (CAD; EC
1.1.1.195
) is severely reduced. The products of CAD, cinnamyl alcohols, are the precursors of lignin, a major cell wall polymer of plant vascular tissues. Lignin composition in this mutant shows dramatic modifications, including increased incorporation of the substrate of CAD (coniferaldehyde), indicating that CAD may modulate lignin composition in pine. The recessive
cad-n1
allele, which causes this phenotype, was discovered in a tree heterozygous for this mutant allele. It is inherited as a simple Mendelian locus that maps to the same genomic region as the
cad
locus. In mutant plants, CAD activity and abundance of
cad
RNA transcript are low, and free CAD substrate accumulates to a high level. The wood of the mutant is brown, whereas the wood in wild types is nearly white. The wood phenotype resembles that of brown midrib (
bm
) mutants and some transgenic plants in which xylem is red-brown due to a reduction in CAD activity. However, unlike transgenics with reduced CAD, the pine mutant has decreased lignin content. Wood in which the composition of lignin varies beyond previous expectations still provides vascular function and mechanical support.
Reorganization of an arid ecosystem in response to recent climate change
Authors: Brown James H. , Valone Thomas J. , Curtin Charles G.
Published: July 2002

Natural ecosystems contain many individuals and species interacting with each other and with their abiotic environment. Such systems can be expected to exhibit complex dynamics in which small perturbations can be amplified to cause large changes. Here, we document the reorganization of an arid ecosystem that has occurred since the late 1970s. The density of woody shrubs increased 3-fold. Several previously common animal species went locally extinct, while other previously rare species increased. While these changes are symptomatic of desertification, they were not caused by livestock grazing or drought, the principal causes of historical desertification. The changes apparently were caused by a shift in regional climate: since 1977 winter precipitation throughout the region was substantially higher than average for this century. These changes illustrate the kinds of large, unexpected responses of complex natural ecosystems that can occur in response to both natural perturbations and human activities.
Plasminogen deficiency accelerates vessel wall disease in mice predisposed to atherosclerosis
Authors: Xiao Qing , Danton Mary Jo S. , Witte David P. , Kowala Mark C. , Valentine Maria T. , Bugge Thomas H. , Degen Jay L.
Published: July 2002

A critical link between hemostatic factors and atherosclerosis has been inferred from a variety of indirect observations, including the expression of procoagulant and fibrinolytic factors within atherosclerotic vessels, the presence of fibrin in intimal lesions, and the cellular infiltration of mural thrombi leading to their incorporation into developing plaques. To directly examine the role of the key fibrinolytic factor, plasminogen, in atherogenesis, plasminogen-deficient mice were crossed to hypercholesterolemic, apolipoprotein E-deficient mice predisposed to atherosclerosis. We report that the loss of plasminogen greatly accelerates the formation of intimal lesions in apolipoprotein E-deficient animals, whereas plasminogen deficiency alone does not cause appreciable atherosclerosis. These studies provide direct evidence that circulating hemostatic factors strongly influence vessel wall disease in the context of a disorder in lipid metabolism.
Substrate specificity determinants in the farnesyltransferase β-subunit
Authors: Trueblood Cynthia Evans , Boyartchuk Victor L. , Rine Jasper
Published: July 2002

Protein prenyltransferases catalyze the covalent attachment of isoprenoid lipids (farnesyl or geranylgeranyl) to a cysteine near the C terminus of their substrates. This study explored the specificity determinants for interactions between the farnesyltransferase of
Saccharomyces cerevisiae
and its protein substrates. A series of substitutions at amino acid 149 of the farnesyltransferase β-subunit were tested in combination with a series of substitutions at the C-terminal amino acid of CaaX protein substrates Ras2p and a-factor. Efficient prenylation was observed when oppositely charged amino acids were present at amino acid 149 of the yeast farnesyltransferase β-subunit and the C-terminal amino acid of the CaaX protein substrate, but not when like charges were present at these positions. This evidence for electrostatic interaction between amino acid 149 and the C-terminal amino acid of CaaX protein substrates leads to the prediction that the C-terminal amino acid of the protein substrate binds near amino acid 149 of the yeast farnesyltransferase β-subunit.
Impaired CD19 expression and signaling, enhanced antibody response to type II T independent antigen and reduction of B-1 cells in CD81-deficient mice
Authors: Tsitsikov Erdyni N. , Gutierrez-Ramos Jose Carlos , Geha Raif S.
Published: July 2002

The tetraspanin CD81 is ubiquitously expressed and associated with CD19 on B lymphocytes and with CD4 and CD8 on T lymphocytes. Analysis of mice with disrupted CD81 gene reveals normal T cells but a distinct abnormality in B cells consisting of decreased expression of CD19 and severe reduction in peritoneal B-1 cells. CD81-deficient B cells responded normally to surface IgM crosslinking, but had severely impaired calcium influx following CD19 engagement. CD81-deficient mice had increased serum IgM and IgA and an exaggerated antibody response to the type II T independent antigen TNP-Ficoll. These results suggest that CD81 is important for CD19 signaling and B cell function.
Binding of high-risk human papillomavirus E6 oncoproteins to the human homologue of the
Drosophila
discs large tumor suppressor protein
Authors: Kiyono Tohru , Hiraiwa Atsuro , Fujita Masatoshi , Hayashi Yasuyuki , Akiyama Tetsu , Ishibashi Masahide
Published: July 2002

In the majority of cervical cancers, DNAs of high-risk mucosotpropic human papillomaviruses (HPVs), such as type 16, are maintained so as to express two viral proteins, E6 and E7, suggesting an essential importance to carcinogenesis. The high-risk HPV E6 proteins are known to inactivate p53 tumor suppressor protein but appear to have an additional, molecularly unknown function(s). In this study, we demonstrate that these E6 proteins can bind to the second PDZ domain of the human homologue of the
Drosophila
discs large tumor suppressor protein (hDLG) through their C-terminal XS/TXV/L (where X represents any amino acid, S/T serine or threonine, and V/L valine or leucine) motif. This finding is similar to the interaction between the adenomatous polyposis coli gene product and hDLG. E6 mutants losing the ability to bind to hDLG are no longer able to induce E6-dependent transformation of rodent cells. These results suggest an intriguing possibility that interaction between the E6 protein and hDLG or other PDZ domain-containing proteins could be an underlying mechanism in the development of HPV-associated cancers.
A dileucine motif in the C terminus of the β
2
-adrenergic receptor is involved in receptor internalization
Authors: Gabilondo Ane M. , Hegler Jutta , Krasel Cornelius , Boivin-Jahns Valerie , Hein Lutz , Lohse Martin J.
Published: July 2002

The cytoplasmic C terminus of the β
2
-adrenergic receptor and many other G protein-coupled receptors contains a dileucine sequence that has been implicated in endosome/lysosome targeting of diverse proteins. In the present study, we provide evidence for an essential role of this motif in the agonist-induced internalization of the β
2
-adrenergic receptor. Mutation of Leu-339 and/or Leu-340 to Ala caused little changes in surface expression, ligand binding, G protein coupling, and signaling to adenylyl cyclase, when these receptors were transiently or stably expressed in CHO or HEK-293 cells. However, agonist-induced receptor internalization was markedly impaired in the L
339,340
A double mutant and reduced in the two single mutants. This impairment in receptor internalization was seen by using various approaches to determine internalization: binding of hydrophobic vs. hydrophilic ligands, loss of surface β
2
-adrenergic receptor immunoreactivity, and immunofluorescence microscopy. The selective effects of these mutations suggest that the C-terminal dileucine motif is involved in agonist-induced internalization of the β
2
-adrenergic receptor.
A very limited number of keywords (main patterns) describes all sequences of the human variable heavy (V
H
) and κ (V
κ
) domains
Authors: Gelfand Israel M. , Kister Alexander E.
Published: July 2002

Sequences of the variable heavy (V
H
) and κ (V
κ
) domains of Ig structures were divided into 21 fragments that correspond to strands, loops, or parts of these structural units of the variable domains. Amino acid sequences of fragments (termed “words”) were collected from the 1,172 human heavy and 668 human κ chains available in the Kabat database. Statistical analysis of words of 17 fragments was performed (fragments that comprise the complementary determining regions′ fragments will not be discussed in this paper). The number of different words (those with different residues in at least one position) ranged, for various fragments, from 11 to 75 in the κ chains, and from 23 to 189 in the heavy chains. The main result of this study is that very few keywords, or main patterns of words, were necessary to describe over 90% of the sequences (no more than two keywords per fragment in the κ and no more than five per fragment in the heavy chains). No identical keywords were found for different fragments of the variable domains. Keywords of aligned fragments of the V
H
and V
κ
domains were different in all but two instances. Thus, knowing the keywords, one can determine whether any given small part of a sequence belongs to a heavy or κ chain and predict its precise localization in the sequence. In addition, by using all of the keywords obtained through analysis of the Kabat database, it was possible to describe completely the sequences of the human V
H
and V
κ
germ-line segments.
Scavenger receptor class B, type I (SR-BI) is the major route for the delivery of high density lipoprotein cholesterol to the steroidogenic pathway in cultured mouse adrenocortical cells
Authors: Temel Ryan E. , Trigatti Bernardo , DeMattos Ronald B. , Azhar Salman , Krieger Monty , Williams David L.
Published: July 2002

The class B, type I scavenger receptor, SR-BI, binds high density
lipoprotein (HDL) and mediates the selective uptake of HDL cholesteryl
ester (CE) by cultured transfected cells. The high levels of SR-BI
expression in steroidogenic cells
in vivo
and its
regulation by tropic hormones provides support for the hypothesis that
SR-BI is a physiologically relevant HDL receptor that supplies
substrate cholesterol for steroid hormone synthesis. This hypothesis
was tested by determining the ability of antibody directed against
murine (m) SR-BI to inhibit the selective uptake of HDL CE in Y1-BS1
adrenocortical cells. Anti-mSR-BI IgG inhibited HDL CE-selective uptake
by 70% and cell association of HDL particles by 50% in a
dose-dependent manner. The secretion of [
3
H]steroids
derived from HDL containing [
3
H]CE was inhibited by 78%
by anti-mSR-BI IgG. These results establish mSR-BI as the major route
for the selective uptake of HDL CE and the delivery of HDL cholesterol
to the steroidogenic pathway in cultured mouse adrenal cells.
Glucocorticoid enhancement of memory storage involves noradrenergic activation in the basolateral amygdala
Authors: Quirarte Gina L. , Roozendaal Benno , McGaugh James L.
Published: July 2002

Evidence indicates that the modulatory effects of the adrenergic stress hormone epinephrine as well as several other neuromodulatory systems on memory storage are mediated by activation of β-adrenergic mechanisms in the amygdala. In view of our recent findings indicating that the amygdala is involved in mediating the effects of glucocorticoids on memory storage, the present study examined whether the glucocorticoid-induced effects on memory storage depend on β-adrenergic activation within the amygdala. Microinfusions (0.5 μg in 0.2 μl) of either propranolol (a nonspecific β-adrenergic antagonist), atenolol (a β
1
-adrenergic antagonist), or zinterol (a β
2
-adrenergic antagonist) administered bilaterally into the basolateral nucleus of the amygdala (BLA) of male Sprague–Dawley rats 10 min before training blocked the enhancing effect of posttraining systemic injections of dexamethasone (0.3 mg/kg) on 48-h memory for inhibitory avoidance training. Infusions of these β-adrenergic antagonists into the central nucleus of the amygdala did not block the dexamethasone-induced memory enhancement. Furthermore, atenolol (0.5 μg) blocked the memory-enhancing effects of the specific glucocorticoid receptor (GR or type II) agonist RU 28362 infused concurrently into the BLA immediately posttraining. These results strongly suggest that β-adrenergic activation is an essential step in mediating glucocorticoid effects on memory storage and that the BLA is a locus of interaction for these two systems.
The degree of nonlinearity and anisotropy of blood vessel elasticity
Authors: Zhou J. , Fung Y. C.
Published: July 2002

Blood vessel elasticity is important to physiology and clinical problems involving surgery, angioplasty, tissue remodeling, and tissue engineering. Nonlinearity in blood vessel elasticity
in vivo
is important to the formation of solitons in arterial pulse waves. It is well known that the stress–strain relationship of the blood vessel is nonlinear in general, but a controversy exists on how nonlinear it is in the physiological range. Another controversy is whether the vessel wall is biaxially isotropic. New data on canine aorta were obtained from a biaxial testing machine over a large range of finite strains referred to the zero-stress state. A new pseudo strain energy function is used to examine these questions critically. The stress–strain relationship derived from this function represents the sum of a linear stress–strain relationship and a definitely nonlinear relationship. This relationship fits the experimental data very well. With this strain energy function, we can define a parameter called
the degree of nonlinearity
, which represents the fraction of the nonlinear strain energy in the total strain energy per unit volume. We found that for the canine aorta, the degree of nonlinearity varies from 5% to 30%, depending on the magnitude of the strains in the physiological range. In the case of canine pulmonary artery in the arch region, Debes and Fung [Debes, J. C. & Fung, Y. C.(1995)
Am. J. Physiol
. 269, H433–H442] have shown that the linear regime of the stress–strain relationship extends from the zero-stress state to the homeostatic state and beyond. Both vessels, however, are anisotropic in both the linear and nonlinear regimes.
Generation of secretable and nonsecretable interleukin 15 isoforms through alternate usage of signal peptides
Authors: Tagaya Yutaka , Kurys Gloria , Thies Tiffany A. , Losi Jacqueline M. , Azimi Nazli , Hanover John A. , Bamford Richard N. , Waldmann Thomas A.
Published: July 2002

Two isoforms of human interleukin 15 (IL-15) exist. One isoform has a shorter putative signal peptide (21 amino acids) and its transcript shows a tissue distribution pattern that is distinct from that of the alternative IL-15 isoform with a 48-aa signal peptide. The 21-aa signal isoform is preferentially expressed in tissues such as testis and thymus. Experiments using different combinations of signal peptides and mature proteins (IL-2, IL-15, and green fluorescent protein) showed that the short signal peptide regulates the fate of the mature protein by controlling the intracellular trafficking to nonendoplasmic reticulum sites, whereas the long signal peptide both regulates the rate of protein translation and functions as a secretory signal peptide. As a consequence, the IL-15 associated with the short signal peptide is not secreted, but rather is stored intracellularly, appearing in the nucleus and cytoplasmic components. Such production of an intracellular lymphokine is not typical of other soluble interleukin systems, suggesting a biological function for IL-15 as an intracellular molecule.
Asian genotypes of JC virus in Native Americans and in a Pacific Island population: Markers of viral evolution and human migration
Authors: Agostini Hansjürgen T. , Yanagihara Richard , Davis Victor , Ryschkewitsch Caroline F. , Stoner Gerald L.
Published: July 2002

The human polyomavirus JC (JCV) causes the central nervous system demyelinating disease progressive multifocal leukoencephalopathy. Previously, we showed that 40% of Caucasians in the United States excrete JCV in the urine as detected by PCR. We have now studied 68 Navaho from New Mexico, 25 Flathead from Montana, and 29 Chamorro from Guam. By using PCR amplification of a fragment of the
VP1
gene, JCV DNA was detected in the urine of 45 (66%) Navaho, 14 (56%) Flathead, and 20 (69%) Chamorro. Genotyping of viral DNAs in these cohorts by cycle sequencing showed predominantly type 2 (Asian), rather than type 1 (European). Type 1 is the major type in the United States and Hungary. Type 2 can be further subdivided into 2A, 2B, and 2C. Type 2A is found in China and Japan. Type 2B is a subtype related to the East Asian type, and is now found in Europe and the United States. The large majority (56–89%) of strains excreted by Native Americans and Pacific Islanders were the type 2A subtype, consistent with the origin of these strains in Asia. These findings indicate that JCV infection of Native Americans predates contact with Europeans, and likely predates migration of Amerind ancestors across the Bering land bridge around 12,000–30,000 years ago. If JCV had already differentiated into stable modern genotypes and subtypes prior to first settlement, the origin of JCV in humans may date from 50,000 to 100,000 years ago or more. We conclude that JCV may have coevolved with the human species, and that it provides a convenient marker for human migrations in both prehistoric and modern times.
Hypertension, cardiac hypertrophy, and sudden death in mice lacking natriuretic peptide receptor A
Authors: Oliver Paula M. , Fox Jennifer E. , Kim Ron , Rockman Howard A. , Kim Hyung-Suk , Reddick Robert L. , Pandey Kailash N. , Milgram Sharon L. , Smithies Oliver , Maeda Nobuyo
Published: July 2002

Natriuretic peptides, produced in the heart, bind to the natriuretic peptide receptor A (NPRA) and cause vasodilation and natriuresis important in the regulation of blood pressure. We here report that mice lacking a functional
Npr1
gene coding for NPRA have elevated blood pressures and hearts exhibiting marked hypertrophy with interstitial fibrosis resembling that seen in human hypertensive heart disease. Echocardiographic evaluation of the mice demonstrated a compensated state of systemic hypertension in which cardiac hypertrophy and dilatation are evident but with no reduction in ventricular performance. Nevertheless, sudden death, with morphologic evidence indicative in some animals of congestive heart failure and in others of aortic dissection, occurred in all 15 male mice lacking
Npr1
before 6 months of age, and in one of 16 females in our study. Thus complete absence of NPRA causes hypertension in mice and leads to cardiac hypertrophy and, particularly in males, lethal vascular events similar to those seen in untreated human hypertensive patients.
Vascular imprints of neuronal activity: Relationships between the dynamics of cortical blood flow, oxygenation, and volume changes following sensory stimulation
Authors: Malonek Dov , Dirnagl Ulrich , Lindauer Ute , Yamada Katsuya , Kanno Iwao , Grinvald Amiram
Published: July 2002

Modern functional neuroimaging methods, such as positron-emission tomography (PET), optical imaging of intrinsic signals, and functional MRI (fMRI) utilize activity-dependent hemodynamic changes to obtain indirect maps of the evoked electrical activity in the brain. Whereas PET and flow-sensitive MRI map cerebral blood flow (CBF) changes, optical imaging and blood oxygenation level-dependent MRI map areas with changes in the concentration of deoxygenated hemoglobin (HbR). However, the relationship between CBF and HbR during functional activation has never been tested experimentally. Therefore, we investigated this relationship by using imaging spectroscopy and laser-Doppler flowmetry techniques, simultaneously, in the visual cortex of anesthetized cats during sensory stimulation. We found that the earliest microcirculatory change was indeed an increase in HbR, whereas the CBF increase lagged by more than a second after the increase in HbR. The increased HbR was accompanied by a simultaneous increase in total hemoglobin concentration (Hbt), presumably reflecting an early blood volume increase. We found that the CBF changes lagged after Hbt changes by 1 to 2 sec throughout the response. These results support the notion of active neurovascular regulation of blood volume in the capillary bed and the existence of a delayed, passive process of capillary filling.
Elevated levels of mutation in multiple tissues of mice deficient in the DNA mismatch repair gene
Pms2
Authors: Narayanan Latha , Fritzell James A. , Baker Sean M. , Liskay R. Michael , Glazer Peter M.
Published: July 2002

The
Pms2
gene has been implicated in hereditary colon cancer and is one of several mammalian homologs of the
Escherichia coli mutL
DNA mismatch repair gene. To determine the effect of
Pms2
inactivation on genomic integrity
in vivo
, hybrid transgenic mice were constructed that carry targeted disruptions at the
Pms2
loci along with a chromosomally integrated mutation reporter gene. In the absence of any mutagenic treatment, mice nullizygous for
Pms2
showed a 100-fold elevation in mutation frequency in all tissues examined compared with both wild-type and heterozygous litter mates. The mutation pattern in the nullizygotes was notable for frequent 1-bp deletions and insertions within mononucleotide repeat sequences, consistent with an essential role for PMS2 in the repair of replication slippage errors. Further, the results demonstrate that high rates of mutagenesis in multiple tissues are compatible with normal development and life and are not necessarily associated with accelerated aging. Also, the finding of genetic instability in all tissues tested contrasts with the limited tissue distribution of cancers in the animals, raising important questions regarding the role of mutagenesis in carcinogenesis.
The CAG repeat within the androgen receptor gene and its relationship to prostate cancer
Authors: Giovannucci Edward , Stampfer Meir J. , Krithivas Krishna , Brown Myles , Brufsky Adam , Talcott James , Hennekens Charles H. , Kantoff Philip W.
Published: July 2002

The length of a polymorphic CAG repeat sequence, occurring in the androgen receptor gene, is inversely correlated with transcriptional activity by the androgen receptor. Because heightened androgenic stimulation may increase risk of prostate cancer development and progression, we examined whether shorter CAG repeats in the androgen receptor gene are related to higher risk of prostate cancer. We conducted a nested case-control study of 587 newly diagnosed cases of prostate cancer detected between 1982 and 1995, and 588 controls without prostate cancer, within the Physician’s Health Study. An association existed between fewer androgen receptor gene CAG repeats and higher risk of total prostate cancer [relative risk (RR) = 1.52; 95% confidence interval (CI) = 0.92–2.49;
P
trend = 0.04; for men with CAG repeat lengths ≤18 relative to ≥26 repeats]. In particular, a shorter CAG repeat sequence was associated with cancers characterized by extraprostatic extension or distant metastases (stage C or D) or high histologic grade (RR = 2.14; CI = 1.14–4.01;
P
trend = 0.001). This association was observed individually both for high stage (RR = 2.23) and high grade prostate cancer (RR = 1.89). Men with shorter repeats were at particularly high risk for distant metastatic and fatal prostate cancer. Variability in the CAG repeat length was not associated with low grade or low stage disease. These results demonstrate that a shorter CAG repeat sequence in the androgen receptor gene predicts higher grade and advanced stage of prostate cancer at diagnosis, and metastasis and mortality from the disease. The clinical implications of these results should be evaluated further.
Time-course changes of nerve growth factor, corticotropin-releasing hormone, and nitric oxide synthase isoforms and their possible role in the development of inflammatory response in experimental allergic encephalomyelitis
Authors: Calzà Laura , Giardino Luciana , Pozza Monica , Micera Alessandra , Aloe Luigi
Published: July 2002

In this paper we report a time-course study of development of experimental allergic encephalomyelitis in Lewis rats, by monitoring neuroendocrine regulation of the hypothalamus–pituitary–adrenal axis through corticotropin-releasing hormone mRNA expression, inflammatory cellular infiltrate, macrophagic and neuronal nitric oxide synthase, nerve growth factor (NGF), and NGF p75 and trkA receptors in the brain and spinal cord. We analyzed animals during 20 days after immunization, a time interval that corresponds to the acute immunological phase. We have described a severe, early fall of corticotropin-releasing hormone mRNA expression, which could account for the decreased response of the hypothalamus–pituitary–adrenal axis to inflammatory stress. During this period, an increase of neuronal nitric oxide synthase was observed in the cerebral cortex and spinal cord, and macrophagic nitric oxide synthase positive cells were found in the inflammatory cellular infiltrate, which was abundant in perivascular and submeningeal areas 20 days after immunization. Concomitantly, we found a dramatic up-regulation of NGF receptors on the wall of blood vessels and adjacent neurons in perivascular areas. NGF content also had increased in some brain areas, such as the thalamus, while it had decreased in others, like the spinal cord and medulla oblongata, at time points in which the most serious cellular infiltrate was found.
Targeted disruption of the mouse
Stat3
gene leads to early embryonic lethality
Authors: Takeda Kiyoshi , Noguchi Koichi , Shi Wei , Tanaka Takashi , Matsumoto Makoto , Yoshida Nobuaki , Kishimoto Tadamitsu , Akira Shizuo
Published: July 2002

Signal transducer and activator of transcription (STAT) proteins have been shown to mediate biological actions in response to cytokines. Stat3, a member of the STAT family, is activated by a variety of cytokines, including the interleukin 6 family of cytokines, leptin, granulocyte colony-stimulating factor, and epidermal growth factor. To address the biological function of Stat3, we generated mice deficient in Stat3 by gene targeting. No viable Stat3-deficient mice could be obtained from heterozygote intercross. Analysis of embryos at several gestation times revealed that Stat3-deficient embryos showed a rapid degeneration between embryonic days 6.5 and 7.5, although they developed into the egg cylinder stage until embryonic day 6.0. These results demonstrate that Stat3 is essential for the early development of mouse embryos.
Cytosine methylation determines hot spots of DNA damage in the human
P
53 gene
Authors: Denissenko Mikhail F. , Chen James X. , Tang Moon-shong , Pfeifer Gerd P.
Published: July 2002

In the
P53
tumor suppressor gene, a remarkably large number of somatic mutations are found at methylated CpG dinucleotides. We have previously mapped the distribution of (±)
anti
-7β,8α-dihydroxy-9α,10α-epoxy-7,8,9,10-tetrahydrobenzo[
a
]pyrene (BPDE) adducts along the human
P53
gene [Denissenko, M. F., Pao, A., Tang, M.-s. & Pfeifer, G. P. (1996)
Science
274, 430–432]. Strong and selective formation of adducts occurred at guanines in CpG sequences of codons 157, 248, and 273, which are the major mutational hot spots in lung cancer. Chromatin structure was not involved in preferential modification of these sites by BPDE. To investigate other possible mechanisms underlying the selectivity of BPDE binding, we have mapped the adducts in plasmid DNA containing genomic
P53
sequences. The adduct profile obtained was different from that in genomic DNA. However, when cytosines at CpG sequences were converted to 5-methylcytosines by the CpG-specific methylase
Sss
I and the DNA was subsequently treated with BPDE, adduct hot spots were created which were similar to those seen in genomic DNA where all CpGs are methylated. A strong positive effect of 5-methylcytosine on BPDE adduct formation at CpG sites was also documented with sequences of the
PGK1
gene derived from an active or inactive human X chromosome and having differential methylation patterns. These results show that methylated CpG dinucleotides, in addition to being an endogenous promutagenic factor, may represent a preferential target for exogenous chemical carcinogens. The data open new avenues concerning the reasons that the majority of mutational hot spots in human genes are at CpGs.
Fatty acids and eicosanoids regulate gene expression through direct interactions with peroxisome proliferator-activated receptors α and γ
Authors: Kliewer Steven A. , Sundseth Scott S. , Jones Stacey A. , Brown Peter J. , Wisely G. Bruce , Koble Cecilia S. , Devchand Pallavi , Wahli Walter , Willson Timothy M. , Lenhard James M. , Lehmann Jürgen M.
Published: July 2002

Peroxisome proliferator-activated receptors (PPARs) α and γ are key regulators of lipid homeostasis and are activated by a structurally diverse group of compounds including fatty acids, eicosanoids, and hypolipidemic drugs such as fibrates and thiazolidinediones. While thiazolidinediones and 15-deoxy-Δ
12,14
-prostaglandin J
2
have been shown to bind to PPARγ, it has remained unclear whether other activators mediate their effects through direct interactions with the PPARs or via indirect mechanisms. Here, we describe a novel fibrate, designated GW2331, that is a high-affinity ligand for both PPARα and PPARγ. Using GW2331 as a radioligand in competition binding assays, we show that certain mono- and polyunsaturated fatty acids bind directly to PPARα and PPARγ at physiological concentrations, and that the eicosanoids 8(S)-hydroxyeicosatetraenoic acid and 15-deoxy-Δ
12,14
-prostaglandin J
2
can function as subtype-selective ligands for PPARα and PPARγ, respectively. These data provide evidence that PPARs serve as physiological sensors of lipid levels and suggest a molecular mechanism whereby dietary fatty acids can modulate lipid homeostasis.