bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitric oxide-induced cytostasis and cell cycle arrest of a human breast cancer cell line (MDA-MB-231): Potential role of cyclin D1
Authors: Pervin Shehla , Singh Rajan , Chaudhuri Gautam
Published: July 2002

DETA-NONOate, a nitric oxide (NO) donor, induced cytostasis in the
human breast cancer cells MDA-MB-231, and the cells were arrested in
the G
1
phase of the cell cycle. This cytostatic effect of
the NO donor was associated with the down-regulation of cyclin D1 and
hypophosphorylation of the retinoblastoma protein. No changes in the
levels of cyclin E or the catalytic partners of these cyclins, CDK2,
CDK4, or CDK6, were observed. This NO-induced cytostasis and decrease
in cyclin D1 was reversible for up to 48 h of DETA-NONOate (1 mM)
treatment. DETA-NONOate (1 mM) produced a steady-state concentration of
0.5 μM of NO over a 24-h period. Synchronized population of the cells
exposed to DETA-NONOate remained arrested at the G
1
phase
of the cell cycle whereas untreated control cells progressed through
the cell cycle after serum stimulation. The cells arrested at the
G
1
phase after exposure to the NO donor had low cyclin D1
levels compared with the control cells. The levels of cyclin E and
CDK4, however, were similar to the control cells. The decline in cyclin
D1 protein preceded the decrease of its mRNA. This decline of cyclin D1
was due to a decrease in its synthesis induced by the NO donor and not
due to an increase in its degradation. We conclude that down-regulation
of cyclin D1 protein by DETA-NONOate played an important role in the
cytostasis and arrest of these tumor cells in the G
1
phase
of the cell cycle.
Different contributions of thymopoiesis and homeostasis-driven proliferation to the reconstitution of naive and memory T cell compartments
Authors: Ge Qing , Hu Hui , Eisen Herman N. , Chen Jianzhu
Published: July 2002

Following transfer into lymphopenic hosts, naive CD8 T cells proliferate and acquire memory phenotype. Although the acquired phenotype is stable in recombination activating gene-1-deficient (RAG−/−) recipients, in sublethally irradiated mice naive CD8 T cells of donor origin gradually accumulate. The naive cells have been attributed to phenotypic reversion of homeostatic memory cells, implying instability of memory phenotype and restoration of the naive T cell compartment by homeostasis-driven proliferation. We show here that (i) the accumulation of naive CD8 T cells of donor origin only occurs in recipients that have been irradiated and have an intact thymus; (ii) the apparent reversion of memory to naive cells actually results fromde novoT cell development of hematopoietic stem cells, present in the donor spleen or lymph node cell populations, in the thymus of irradiated recipients; and (iii) the number of homeostatic memory cells generated in both RAG−/−and irradiated hosts reaches a plateau value and their phenotype is stably maintained even after retransfer into nonirradiated normal mice for 30 days. These findings demonstrate that homeostatic memory T cells do not revert to naive cells. After severe T cell depletion homeostasis-driven proliferation restores only the memory T cell compartment, whereas thymopoiesis is required for the reconstitution of the naive T cell compartment.
Transferring an inborn auditory perceptual predisposition with interspecies brain transplants
Authors: Long Kevin D. , Kennedy Grace , Balaban Evan
Published: July 2002

Inborn species' perceptual preferences are thought to serve as
important guides for neonatal learning in most species of higher
vertebrates. Although much work has been carried out on experiential
contributions to the expression of such preferences, their neural and
developmental correlates remain largely unexplored. Here we use
embryonic neural transplants between two bird species, the Japanese
quail and the domestic chicken, to demonstrate that an inborn auditory
perceptual predisposition is transferable between species. The transfer
of the perceptual preference was dissociated from changes to the
vocalizations of the resulting animals (called chimeras), suggesting
that experiential differences in auditory self-stimulation cannot
explain the perceptual change. A preliminary localization of the
effective brain region for the behavioral transfer by using a naturally
occurring species-cell marker revealed that it is not contained within
the major avian auditory pathways. To our knowledge, this is the first
demonstration that abstract aspects of auditory perception can be
transferred between species with transplants of the central nervous
system.
The pleiotropic response regulator DegU functions as a priming protein in competence development in
Bacillus subtilis
Authors: Hamoen Leendert W. , Van Werkhoven Aske F. , Venema Gerard , Dubnau David
Published: July 2002

The response regulator DegU is involved in various late-growth developmental processes in
Bacillus subtilis
, including the production of degradative enzymes and the development of genetic competence. DegU is essential for the expression of the competence transcription factor, encoded by
comK
. ComK is required for the transcription of genes encoding the DNA uptake and integration machinery, as well as for the transcription of its own gene. We have purified DegU to study its role in the expression of
comK
, and we demonstrate here that DegU binds specifically to the
comK
promoter. The binding of the response regulator DegU to a promoter target had not been reported previously. DNase I protection analyses show that the DegU binding site overlaps with the ComK binding site, and gel retardation experiments indicate that DegU strongly stimulates the binding of ComK to the
comK
promoter. We propose that DegU functions at the initiation of competence development, when ComK concentrations are insufficient to support
comK
transcription, by facilitating ComK binding to the
comK
promoter. DegU therefore acts as a priming protein that primes the autostimulatory transcription of
comK
. Such priming activity adds a function to the class of response regulator proteins.
The Y chromosome in the liverwort
Marchantia polymorpha
has accumulated unique repeat sequences harboring a male-specific gene
Authors: Okada Sachiko , Sone Takefumi , Fujisawa Masaki , Nakayama Shigeki , Takenaka Mizuki , Ishizaki Kimitsune , Kono Kaoru , Shimizu-Ueda Yuu , Hanajiri Tsutomu , Yamato Katsuyuki T. , Fukuzawa Hideya , Brennicke Axel , Ohyama Kanji
Published: July 2002

The haploid liverwort
Marchantia polymorpha
has heteromorphic sex chromosomes, an X chromosome in the female and a Y chromosome in the male. We here report on the repetitive structure of the liverwort Y chromosome through the analysis of male-specific P1-derived artificial chromosome (PAC) clones, pMM4G7 and pMM23-130F12. Several chromosome-specific sequence elements of ≈70 to 400 nt are combined into larger arrangements, which in turn are assembled into extensive Y chromosome-specific stretches. These repeat sequences contribute 2–3 Mb to the Y chromosome based on the observations of three different approaches: fluorescence
in situ
hybridization, dot blot hybridization, and the frequency of clones containing the repeat sequences in the genomic library. A novel Y chromosome-specific gene family was found embedded among these repeat sequences. This gene family encodes a putative protein with a RING finger motif and is expressed specifically in male sexual organs. To our knowledge, there have been no other reports for an active Y chromosome-specific gene in plants. The chromosome-specific repeat sequences possibly contribute to determining the identity of the Y chromosome in
M. polymorpha
as well as to maintaining genes required for male functions, as in mammals such as human.
Control of Epstein–Barr virus reactivation by activated CD40 and viral latent membrane protein 1
Authors: Adler Barbara , Schaadt Eveline , Kempkes Bettina , Zimber-Strobl Ursula , Baier Barbara , Bornkamm Georg W.
Published: July 2002

In humans, Epstein–Barr virus (EBV) establishes a persistent
latent infection in peripheral resting B lymphocytes. Virus
reactivation is highly restricted. Whereas in healthy humans the
infection usually is benign, immunocompromised patients show an
increased risk for EBV-associated malignancies, accompanied by
an increase in virus replication and in the number of virus-infected
cells. To search for viral and host factors regulating virus
reactivation, we used conditionally EBV-immortalized B cells. We found
that CD40–CD40 ligand interaction and the viral mimic of activated
CD40, EBV latent membrane protein 1, suppress virus reactivation. Both
inhibit anti-IgM or phorbolester-induced transcription of the viral
immediate early protein BZLF1, which controls entry into the viral
lytic cycle. The finding that latent membrane protein 1 and CD40
contribute to the regulation of latency may have important implications
for the balance between EBV and its host in normal as well as in
immunocompromised individuals.
A transcriptional roadmap to wood formation
Authors: Hertzberg Magnus , Aspeborg Henrik , Schrader Jarmo , Andersson Anders , Erlandsson Rikard , Blomqvist Kristina , Bhalerao Rupali , Uhlén Mathias , Teeri Tuula T. , Lundeberg Joakim , Sundberg Björn , Nilsson Peter , Sandberg Göran
Published: July 2002

The large vascular meristem of poplar trees with its highly
organized secondary xylem enables the boundaries between different
developmental zones to be easily distinguished. This property of
wood-forming tissues allowed us to determine a unique tissue-specific
transcript profile for a well defined developmental gradient. RNA was
prepared from different developmental stages of xylogenesis for DNA
microarray analysis by using a hybrid aspen unigene set consisting of
2,995 expressed sequence tags. The analysis revealed that the genes
encoding lignin and cellulose biosynthetic enzymes, as well as a number
of transcription factors and other potential regulators of xylogenesis,
are under strict developmental stage-specific transcriptional
regulation.
Earliest evolution associated with closure of the Tropical American Seaway.
Authors: Collins L S , Budd A F , Coates A G
Published: July 2002

Oceanographic changes caused by the emerging Central American isthmus, which completely severed connections between the Caribbean Sea and tropical Pacific Ocean about 3.5 million years ago, began to stimulate evolution of Caribbean reef corals and benthic foraminifera in the Late Miocene. At that time, first appearances of benthic foraminifera increased, especially those species strongly associated with carbonate-rich substrata; reef corals diversified dramatically; and the carbonate content of southern Caribbean deep-sea sediments increased. We suggest that the changes in marine environments caused by the constricting seaway and resulting in increasing carbonate content of sediments induced accelerated origination in reef corals and carbonate-associated benthic foraminifera.
Cryo-electron microscopy studies of empty capsids of human parvovirus B19 complexed with its cellular receptor.
Authors: Chipman P R , Agbandje-McKenna M , Kajigaya S , Brown K E , Young N S , Baker T S , Rossmann M G
Published: July 2002

The three-dimensional structures of human parvovirus B19 VP2 capsids, alone and complexed with its cellular receptor, globoside, have been determined to 26 resolution. The B19 capsid structure, reconstructed from cryo-electron micrographs of vitrified specimens, has depressions on the icosahedral 2-fold and 3-fold axes, as well as a canyon-like region around the 5-fold axes. Similar results had previously been found in an 8 angstrom resolution map derived from x-ray diffraction data. Other parvoviral structures have a cylindrical channel along the 5-fold icosahedral axes, whereas density covers the 5-fold axes in B19. The glycolipid receptor molecules bind into the depressions on the 3-fold axes of the B19:globoside complex. A model of the tetrasaccharide component of globoside, organized as a trimeric fiber, fits well into the difference density representing the globoside receptor. Escape mutations to neutralizing antibodies map onto th capsid surface at regions immediately surrounding the globoside attachment sites. The proximity of the antigenic epitopes to the receptor site suggests that neutralization of virus infectivity is caused by preventing attachment of viruses to cells.
Spontaneous mutations recovered as mosaics in the mouse specific-locus test
Authors: Russell L. B. , Russell W. L.
Published: July 2002

The specific-locus test (SLT) detects new mutants among mice
heterozygous for seven recessive visible markers. Spontaneous mutations
can be manifested not only as singleton whole-body mutants in controls
(for which we report new data), but as mosaics—either visible
(manifesting mottled coat color) in the scored generation
(G
2
) or masked, among the wild-type parental generation
(G
1
). Masked G
1
mosaics reveal themselves by
producing clusters of whole-body mutants in G
2
. We provide
evidence that most, if not all, mosaics detected in the SLT (both
radiation and control progenies) result from a single-strand
spontaneous mutation subsequent to the last premeiotic mitosis and
before the first postmeiotic one of a
parental
genome—the
“perigametic interval.” Such events in the genomes of the
G
1
and G
0
result, respectively, in visible and
masked 50:50 mosaics. Per cell cycle, the spontaneous mutation rate in
the perigametic interval is much higher than that in pregamete mitotic
divisions. A clearly different locus spectrum further supports the
hypothesis of different origin, and casts further doubt on the validity
of the doubling-dose risk-estimation method. Because mosaics cannot
have arisen in mitotic germ cells, and are not induced by radiation
exposure in the perigametic interval, they should not be included in
calculations of radiation-induced germ-line mutation rates. For
per-generation calculations, inclusion of mosaics yields a spontaneous
frequency 1.7 times that calculated from singletons alone for mutations
contributed by males; including both sexes, the multiple is 2.2.
An intestinal mucin is the target substrate for a baculovirus enhancin
Authors: Wang Ping , Granados Robert R.
Published: July 2002

An invertebrate intestinal mucin (IIM) was identified from a lepidopterous insect,
Trichoplusia ni
. The IIM is a major protein constituent of the peritrophic membrane that facilitates the digestive process, as well as protecting invertebrate digestive tracts from microbial infections. The IIM demonstrated biochemical characteristics similar to vertebrate mucins, but exhibited strong association with the chitin-containing peritrophic membrane matrix. We have demonstrated that a baculovirus enhancin, which is encoded and carried by specific baculoviruses, has mucin-degrading activity both
in vitro
and
in vivo
. The
in vivo
degradation of IIM by enhancin was correlated with the enhancement of baculovirus infections in insects. These findings have shown that viruses have evolved a novel strategy to overcome intestinal mucinous barriers against microorganisms by utilizing a mucin-degrading enzyme.
The radioactivity of atmospheric krypton in 1949–1950
Authors: Turkevich Anthony , Winsberg Lester , Flotow Howard , Adams Richard M.
Published: July 2002

The chemical element krypton, whose principal source is the
atmosphere, had a long-lived radioactive content, in the mid-1940s, of
less than 5 dpm per liter of krypton. In the late 1940s, this content
had risen to values in the range of 100 dpm per liter. It is now some
hundred times higher than the late 1940 values. This radioactivity is
the result of the dissolving of nuclear fuel for military and civilian
purposes, and the release thereby of the fission product krypton-85
(half-life = 10.71 years, fission yield = 0.2%). The present
largest emitter of krypton-85 is the French reprocessing plant at
Cap-de-la-Hague.
A secreted
Salmonella
protein with homology to an avirulence determinant of plant pathogenic bacteria
Authors: Hardt Wolf-Dietrich , Galán Jorge E.
Published: July 2002

Bacterial pathogens have evolved sophisticated mechanisms to interact with their hosts. A specialized type III protein secretion system capable of translocating bacterial proteins into host cells has emerged as a central factor in the interaction between a variety of mammalian and plant pathogenic bacteria with their hosts. Here we describe AvrA, a novel target of the centisome 63 type III protein secretion system of
Salmonella enterica
. AvrA shares sequence similarity with YopJ of the animal pathogen
Yersinia pseudotuberculosis
and AvrRxv of the plant pathogen
Xanthomonas campestris
pv.
vesicatoria
. These proteins are the first examples of putative targets of type III secretion systems in animal and plant pathogenic bacteria that share sequence similarity. They may therefore constitute a novel family of effector proteins with related functions in the cross-talk of these pathogens with their hosts.
Interleukin 3-dependent survival by the Akt protein kinase
Authors: Songyang Zhou , Baltimore David , Cantley Lewis C. , Kaplan David R. , Franke Thomas F.
Published: July 2002

Interleukin 3 (IL-3)-dependent survival of hematopoietic cells is known to rely on the activity of multiple signaling pathways, including a pathway leading to activation of phosphoinositide 3-kinase (PI 3-kinase), and protein kinase Akt is a direct target of PI 3-kinase. We find that Akt kinase activity is rapidly induced by the cytokine IL-3, suggesting a role for Akt in PI 3-kinase-dependent signaling in hematopoetic cells. Dominant-negative mutants of Akt specifically block Akt activation by IL-3 and interfere with IL-3-dependent proliferation. Overexpression of Akt or oncogenic v-akt protects 32D cells from apoptosis induced by IL-3 withdrawal. Apoptosis after IL-3 withdrawal is accelerated by expression of dominant-negative mutants of Akt, indicating that a functional Akt signaling pathway is necessary for cell survival mediated by the cytokine IL-3. Thus Akt appears to be an important mediator of anti-apoptotic signaling in this system.
A model of long-term memory storage in the cerebellar cortex: A possible role for plasticity at parallel fiber synapses onto stellate/basket interneurons
Authors: Kenyon Garrett T.
Published: July 2002

By evoking changes in climbing fiber activity, movement errors are thought to modify synapses from parallel fibers onto Purkinje cells (pf*Pkj) so as to improve subsequent motor performance. Theoretical arguments suggest there is an intrinsic tradeoff, however, between motor adaptation and long-term storage. Assuming a baseline rate of motor errors is always present, then repeated performance of any learned movement will generate a series of climbing fiber-mediated corrections. By reshuffling the synaptic weights responsible for any given movement, such corrections will degrade the memories for other learned movements stored in overlapping sets of synapses. The present paper shows that long-term storage can be accomplished by a second site of plasticity at synapses from parallel fibers onto stellate/basket interneurons (pf*St/Bk). Plasticity at pf*St/Bk synapses can be insulated from ongoing fluctuations in climbing fiber activity by assuming that changes in pf*St/Bk synapses occur only after changes in pf*Pkj synapses have built up to a threshold level. Although climbing fiber-dependent plasticity at pf*Pkj synapses allows for the exploration of novel motor strategies in response to changing environmental conditions, plasticity at pf*St/Bk synapses transfers successful strategies to stable long-term storage. To quantify this hypothesis, both sites of plasticity are incorporated into a dynamical model of the cerebellar cortex and its interactions with the inferior olive. When used to simulate idealized motor conditioning trials, the model predicts that plasticity develops first at pf*Pkj synapses, but with additional training is transferred to pf*St/Bk synapses for long-term storage.
The biochemical basis for
l
-canavanine tolerance by the tobacco budworm
Heliothis virescens
(Noctuidae)
Authors: Melangeli Coromoto , Rosenthal Gerald A. , Dalman Douglas L.
Published: July 2002

The tobacco budworm,
Heliothis virescens
(Noctuidae), a destructive insect pest, is remarkably resistant to
l
-canavanine,
l
-2-amino-4-(guanidinooxy)butyric acid, an arginine antimetabolite that is a potent insecticide for nonadapted species.
H. virescens
employs a constitutive enzyme of the larval gut, known trivially as canavanine hydrolase (CH), to catalyze an irreversible hydrolysis of
l
-canavanine to
l
-homoserine and hydroxyguanidine. As such, it represents a new type of hydrolase, one acting on oxygen–nitrogen bonds (EC
3.13.1.1
). This enzyme has been isolated from the excised gut of
H. virescens
and purified to homogeneity; it exhibits an apparent
K
m
value for
l
-canavanine of 1.1 mM and a turnover number of 21.1 μmol·min
−1
·μmol
−1
. This enzyme has a mass of 285 kDa and is composed of two subunits with a mass of 50 kDa or 47.5 kDa. CH has a high degree of specificity for
l
-canavanine as it cannot function effectively with either
l
-2-amino-5-(guanidinooxy)pentanoate or
l
-2-amino-3-(guanidinooxy)propionate, the higher or lower homolog of
l
-canavanine, respectively.
l
-Canavanine derivatives such as methyl-
l
-canavanine, or
l
-canaline and
O
-ureido-
l
-homoserine, are not metabolized significantly by CH.
Snapshot of a phosphorylated substrate intermediate by kinetic crystallography
Authors: Käck Helena , Gibson Katharine J. , Lindqvist Ylva , Schneider Gunter
Published: July 2002

The ATP-dependent enzyme dethiobiotin synthetase from
Escherichia coli
catalyses the formation of dethiobiotin from CO
2
and 7,8-diaminopelargonic acid. The reaction is initiated by the formation of a carbamate and proceeds through a phosphorylated intermediate, a mixed carbamic phosphoric anhydride. Here, we report the crystal structures at 1.9- and 1.6-Å resolution, respectively, of the enzyme–MgATP–diaminopelargonic acid and enzyme–MgADP–carbamic–phosphoric acid anhydride complexes, observed by using kinetic crystallography. Reaction initiation by addition of either NaHCO
3
or diaminopelargonic acid to crystals already containing cosubstrates resulted in the accumulation of the phosphorylated intermediate at the active site. The phosphoryl transfer step shows inversion of the configuration at the phosphorus atom, consistent with an in-line attack by the carbamate oxygen onto the phosphorus atom of ATP. A key feature in the structure of the complex of the enzyme with the reaction intermediate is two magnesium ions, bridging the phosphates at the cleavage site. These magnesium ions compensate the negative charges at both phosphate groups after phosphoryl transfer and contribute to the stabilization of the reaction intermediate.
CTXφ immunity: Application in the development of cholera vaccines
Authors: Kimsey Harvey H. , Waldor Matthew K.
Published: July 2002

CTXφ is a filamentous bacteriophage that encodes cholera toxin, the principal virulence factor of
Vibrio cholerae
. CTXφ is unusual among filamentous phages because it encodes a repressor and forms lysogens. CTXφ can infect the existing live-attenuated
V. cholerae
vaccine strains derived from either the El Tor or classical
V. cholerae
biotypes and result in vaccine reversion to toxinogenicity. Intraintestinal CTXφ transduction assays were used to demonstrate that El Tor biotype strains of
V. cholerae
are immune to infection with the El Tor-derived CTXφ, whereas classical strains are not. The El Tor CTXφ repressor, RstR, was sufficient to render classical strains immune to infection with the El Tor CTXφ. The DNA sequences of the classical and El Tor CTXφ repressors and their presumed cognate operators are highly diverged, whereas the sequences that surround this “immunity” region are nearly identical. Transcriptional fusion studies revealed that the El Tor RstR mediated repression of an El Tor
rstA-lacZ
fusion but did not repress a classical
rstA-lacZ
fusion. Likewise, the classical RstR only repressed a classical
rstA-lacZ
fusion. Thus, similar to the mechanistic basis for heteroimmunity among lambdoid phages, the specificity of CTXφ immunity is based on the divergence of the sequences of repressors and their operators. Expression of the El Tor
rstR
in either El Tor or classical live-attenuated
V. cholerae
vaccine strains effectively protected these vaccines from CTXφ infection. Introduction of
rstR
into
V. cholerae
vaccine strains should enhance their biosafety.
Can ends justify the means?: Telomeres and the mechanisms of replicative senescence and immortalization in mammalian cells
Authors: Sedivy John M.
Published: July 2002

Finite replicative lifespan, or senescence, of mammalian
cells in culture is a phenomenon that has generated much curiosity
since its description. The obvious significance of senescence to
organismal aging and the development of cancer has engendered a
long-lasting and lively debate about its mechanisms. Recent discoveries
concerning the phenotypes of telomerase knockout mice, the consequences
of telomerase reexpression in somatic cells, and genes that regulate
senescence have provided striking molecular insights but also have
uncovered important new questions. The objective of this review is to
reconcile old observations with new molecular details and to focus
attention on the key remaining puzzles.
Transgenes are dispensable for the RNA degradation step of cosuppression
Authors: Palauqui Jean-Christophe , Vaucheret Hervé
Published: July 2002

Cosuppression results in the degradation of RNA from host genes and homologous transgenes after transcription in the nucleus. By using grafting experiments, we have shown previously that a systemic signal mediates the propagation of cosuppression ofNiahost genes and 35S-Nia2transgenes from silenced 35S-Nia2transgenic stocks to nonsilenced 35S-Nia2transgenic scions but not to wild-type scions. Here, we examined the requirements for triggering and maintenance of cosuppression in various types of scions. Grafting-induced silencing occurred in 35S-Nia2transgenic lines over-accumulatingNiamRNA whether they are able to spontaneously trigger cosuppression or not and in 35S-Nia2transgene-free plants over-accumulating hostNiamRNA caused by metabolic derepression. When grafting-induced silenced scions were removed from the silenced stocks and regrafted onto wild-type plants, silencing was not maintained in the 35S-Nia2transgene-free plants and in the 35S-Nia2transgenic lines that are not able to trigger cosuppression spontaneously. Conversely, silencing was maintained in the 35S-Nia2transgenic lines that are able to trigger cosuppression spontaneously. Our results indicate that the presence of a 35S-Nia2transgene is dispensable for the RNA degradation step of posttranscriptional silencing when hostNiamRNA over-accumulate above the level of wild-type plants. They also suggest that grafting-induced RNA degradation does not result in the production of the systemic silencing signal required for spontaneous triggering and maintenance.
Propagation by sporulation in the guinea pig symbiont
Metabacterium polyspora
Authors: Angert Esther R. , Losick Richard M.
Published: July 2002

The Gram-positive bacterium
Metabacterium polyspora
is an uncultivated symbiont of the guinea pig gastrointestinal tract. Here we present evidence that in
M. polyspora
vegetative cell division has taken on a minor, and apparently dispensable, role in propagation. Instead, this unusual bacterium has evolved the capacity to produce progeny in the form of multiple endospores. Endospore formation is coordinated with transit of the bacterium through the gastrointestinal tract of the guinea pig. For the majority of cells, sporulation is initiated in the ileum, whereas later stages of development take place in the cecum. We show that multiple endospores are generated both by asymmetric division at both poles of the cell and by symmetric division of the endospores at an early stage of their development. Our findings suggest that
M. polyspora
represents an intermediate step in the evolution of a novel mode of cellular propagation that originates with endospore-forming
Bacillus
and
Clostridium
spp., which reproduce by binary fission, and extends to
Epulopiscium
spp., which create multiple viviparous offspring by a process of internal reproduction.
The three members of the pocket proteins family share the ability to repress E2F activity through recruitment of a histone deacetylase
Authors: Ferreira Roger , Magnaghi-Jaulin Laura , Robin Philippe , Harel-Bellan Annick , Trouche Didier
Published: July 2002

The transcription factor E2F plays a major role in cell cycle control in mammalian cells. E2F binding sites, which are present in the promoters of a variety of genes required for S phase, shift from a negative to a positive role in transcription at the commitment point, a crucial point in G
1
that precedes the G
1
/S transition. Before the commitment point, E2F activity is repressed by members of the pocket proteins family. This repression is believed to be crucial for the proper control of cell growth. We have previously shown that Rb, the founding member of the pocket proteins family, represses E2F1 activity by recruiting the histone deacetylase HDAC1. Here, we show that the two other members of the pocket proteins family, p107 and p130, also are able to interact physically with HDAC1 in live cells. HDAC1 interacts with p107 and Rb through an “LXCXE”-like motif, similar to that used by viral transforming proteins to bind and inactivate pocket proteins. Indeed, we find that the viral transforming protein E1A competes with HDAC1 for p107 interaction. We also demonstrate that p107 is able to interact simultaneously with HDAC1 and E2F4, suggesting a model in which p107 recruits HDAC1 to repress E2F sites. Indeed, we demonstrate that histone deacetylase activity is involved in the p107- or p130-induced repression of E2F4. Taken together, our data suggest that all members of the E2F family are regulated in early G
1
by similar complexes, containing a pocket protein and the histone deacetylase HDAC1.
Adeno-associated viral-mediated catalase expression suppresses optic neuritis in experimental allergic encephalomyelitis
Authors: Guy John , Qi Xiaoping , Hauswirth William W.
Published: July 2002

Suppression of oxidative injury by viral-mediated transfer of the human catalase gene was tested in the optic nerves of animals with experimental allergic encephalomyelitis (EAE). EAE is an inflammatory autoimmune disorder of primary central nervous system demyelination that has been frequently used as an animal model for the human disease multiple sclerosis (MS). The optic nerve is a frequent site of involvement common to both EAE and MS. Recombinant adeno-associated virus containing the human gene for catalase was injected over the right optic nerve heads of SJL/J mice that were simultaneously sensitized for EAE. After 1 month, cell-specific catalase activity, evaluated by quantitation of catalase immunogold, was increased approximately 2-fold each in endothelia, oligodendroglia, astrocytes, and axons of the optic nerve. Effects of catalase on the histologic lesions of EAE were measured by computerized analysis of the myelin sheath area (for demyelination), optic disc area (for optic nerve head swelling), extent of the cellular infiltrate, extravasated serum albumin labeled by immunogold (for blood–brain barrier disruption), and
in vivo
H
2
O
2
reaction product. Relative to control, contralateral optic nerves injected with the recombinant virus without a therapeutic gene, catalase gene inoculation reduced demyelination by 38%, optic nerve head swelling by 29%, cellular infiltration by 34%, disruption of the blood–brain barrier by 64%, and
in vivo
levels of H
2
O
2
by 61%. Because the efficacy of potential treatments for MS are usually initially tested in the EAE animal model, this study suggests that catalase gene delivery by using viral vectors may be a therapeutic strategy for suppression of MS.
Blood-borne seeding by hematopoietic and endothelial precursors from the allantois
Authors: Caprioli Arianna , Jaffredo Thierry , Gautier Rodolphe , Dubourg Cécile , Dieterlen-Lièvre Françoise
Published: July 2002

Until now the allantois has not been considered as a hematopoietic organ. Here we report experimental evidence demonstrating the
in situ
emergence of both hematopoietic and endothelial precursors in the avian allantoic bud. When the prevascularized allantoic bud from a quail embryo was grafted in the coelom of a chicken host, hematopoietic and endothelial cells later were found in the bone marrow of the host. Because the graft was located at a distance from the limb bud, these cells could reach the bone marrow only by the circulatory pathway. This blood-borne seeding may be accomplished by distinct hematopoietic and endothelial precursors, or by hemangioblasts, the postulated common precursors of these two lineages; we consider the latter interpretation more likely. We also show by reverse transcription–PCR that the allantois region expresses very early the
GATA
genes involved in hematopoiesis and some β-globin chain genes.
Investigation of the bottleneck leading to the domestication of maize
Authors: Eyre-Walker Adam , Gaut Rebecca L. , Hilton Holly , Feldman Dawn L. , Gaut Brandon S.
Published: July 2002

Maize (Zea maysssp.mays) is genetically diverse, yet it is also morphologically distinct from its wild relatives. These two observations are somewhat contradictory: the first observation is consistent with a large historical population size for maize, but the latter observation is consistent with strong, diversity-limiting selection during maize domestication. In this study, we sampled sequence diversity, coupled with simulations of the coalescent process, to study the dynamics of a population bottleneck during the domestication of maize. To do this, we determined the DNA sequence of a 1,400-bp region of theAdh1 locus from 19 individuals representing maize, its presumed progenitor (Z. maysssp.parviglumis), and a more distant relative (Zea luxurians). The sequence data were used to guide coalescent simulations of population bottlenecks associated with domestication. Our study confirms high genetic diversity in maize—maize contains 75% of the variation found in its progenitor and is more diverse than its wild relative,Z. luxurians—but it also suggests that sequence diversity in maize can be explained by a bottleneck of short duration and very small size. For example, the breadth of genetic diversity in maize is consistent with a founding population of only 20 individuals when the domestication event is 10 generations in length.
Isolation of a cytokinin gene,
ZOG1
, encoding zeatin
O
-glucosyltransferase from
Phaseolus lunatus
Authors: Martin Ruth C. , Mok Machteld C. , Mok David W. S.
Published: July 2002

Zeatin is the most active and ubiquitous of the naturally occurring cytokinins. The
O
-glucoside of zeatin, found in all plants examined, is considered to be important in cytokinin transport, storage, and protection against cytokinin oxidases. The enzyme UDPglucose:zeatin
O
-glucosyltransferase (EC
2.4.1.203
) was previously isolated from
Phaseolus lunatus
seeds. Immunoscreening of an expression library with monospecific antibody resulted in the isolation of a cDNA encoding the enzyme. The recombinant protein efficiently converts labeled zeatin to
O
-glucosylzeatin and has properties similar to the native enzyme. The cDNA of 1.5 kb contains an ORF encoding a 51.4-kDa polypeptide of 459 amino acids. The sequence is unique based on a
blast
search of data bases. The genomic sequence, isolated with PCR using specific primers based on the cDNA sequence, does not contain introns. The cloning of this gene provides the tools for further study of the regulation of cytokinin metabolism and analysis of the precise role of
O
-glucosylzeatin in plant development.
Phosphorylation-independent inhibition of parathyroid hormone receptor signaling by G protein-coupled receptor kinases
Authors: Dicker Frank , Quitterer Ursula , Winstel Rainer , Honold Konrad , Lohse Martin J.
Published: July 2002

Homologous desensitization of G protein-coupled receptors is thought to occur in several steps: binding of G protein-coupled receptor kinases (GRKs) to receptors, receptor phosphorylation, kinase dissociation, and finally binding of β-arrestins to phosphorylated receptors. It generally is assumed that only the last step inhibits receptor signaling. Investigating the parathyroid hormone (PTH) receptor → inositol phosphate pathway, we report here that GRKs can inhibit receptor signaling already under nonphosphorylating conditions. GRKs phosphorylated the PTH receptor in membranes and in intact cells; the order of efficacy was GRK2>GRK3>GRK5. Transient transfection of GRKs with the PTH receptor into COS-1 cells inhibited PTH-stimulated inositol phosphate generation. Such an inhibition also was seen with the kinase-negative mutant GRK2-K220R and also for a C-terminal truncation mutant of the PTH receptor that could not be phosphorylated. Several lines of evidence indicated that this phosphorylation-independent inhibition was exerted by an interaction between GRKs and receptors: (
a
) this inhibition was not mimicked by proteins binding to G proteins, phosducin, and GRK2 C terminus, (
b
) GRKs caused an agonist-dependent inhibition (= desensitization) of receptor-stimulated G protein GTPase-activity (this effect also was seen with the kinase-inactive GRK2-mutant and the phosphorylation-deficient receptor mutant), and (
c
) GRKs bound directly to the PTH receptor. These data suggest that signaling by the PTH receptor already is inhibited by the first step of homologous desensitization, the binding of GRKs to the receptors.
Self-assembly of helical ribbons
Authors: Zastavker Yevgeniya V. , Asherie Neer , Lomakin Aleksey , Pande Jayanti , Donovan Joanne M. , Schnur Joel M. , Benedek George B.
Published: July 2002

The self-assembly of helical ribbons is examined in a variety of multicomponent enantiomerically pure systems that contain a bile salt or a nonionic detergent, a phosphatidylcholine or a fatty acid, and a steroid analog of cholesterol. In almost all systems, two different pitch types of helical ribbons are observed: high pitch, with a pitch angle of 54 ± 2°, and low pitch, with a pitch angle of 11 ± 2°. Although the majority of these helices are right-handed, a small proportion of left-handed helices is observed. Additionally, a third type of helical ribbon, with a pitch angle in the range 30–47°, is occasionally found. These experimental findings suggest that the helical ribbons are crystalline rather than liquid crystal in nature and also suggest that molecular chirality may not be the determining factor in helix formation. The large yields of helices produced will permit a systematic investigation of their individual kinetic evolution and their elastic moduli.
Pronounced acute immunosuppression
in vivo
mediated by HIV Tat challenge
Authors: Cohen Sandra S. , Li Chiang , Ding Linna , Cao Yunzhen , Pardee Arthur B. , Shevach Ethan M. , Cohen David I.
Published: July 2002

HIV infection is accompanied by an early immune dysfunction limiting host control of virus and likely contributing to difficulties in achieving a successful vaccine against HIV. We report here that the HIV Tat protein is strongly immunosuppressive, both immediately after immunization of mice with soluble protein (sTat), and in seroconverting humans, and propose that Tat-induced suppression cripples immune surveillance to HIV infection. We show that macrophages are sensitive to sTat stimulation at concentrations 1,000-fold lower (500 pM) than T cells, and this stimulation is accompanied by the immunosuppressive induction of Fas ligand on the macrophage. T cell proliferative defects induced by sTat
in vitro
can be completely (at lower concentrations of sTat) or partially (at higher concentrations) reversed by antagonists to Fas/Fas ligand interaction. We further report a method to preserve immunogenicity while inactivating Tat immunosuppression through oxidation, which advances the use of oxidized Tat as a component of an anti-HIV vaccine. These observations define additional methods to study the immunosuppressive functions of sTat that now may be rapidly applied to primary isolates from individuals with differing clinical courses. Our findings have immediate relevance for vaccine development, by describing and supporting a strategy that includes inactivated sTat in a multicomponent, anti-HIV vaccine.
Glutamate infused posttraining into the hippocampus or caudate-putamen differentially strengthens place and response learning
Authors: Packard Mark G.
Published: July 2002

A cross-maze task that can be acquired through either place or response learning was used to examine the hypothesis that posttraining neurochemical manipulation of the hippocampus or caudate-putamen can bias an animal toward the use of a specific memory system. Male Long-Evans rats received four trials per day for 7 days, a probe trial on day 8, further training on days 9–15, and an additional probe trial on day 16. Training occurred in a cross-maze task in which rats started from a consistent start-box (south), and obtained food from a consistent goal-arm (west). On days 4–6 of training, rats received posttraining intrahippocampal (1 μg/0.5 μl) or intracaudate (2 μg/0.5 μl) injections of either glutamate or saline (0.5 μl). On days 8 and 16, a probe trial was given in which rats were placed in a novel start-box (north). Rats selecting the west goal-arm were designated “place” learners, and those selecting the east goal-arm were designated “response” learners. Saline-treated rats predominantly displayed place learning on day 8 and response learning on day 16, indicating a shift in control of learned behavior with extended training. Rats receiving intrahippocampal injections of glutamate predominantly displayed place learning on days 8 and 16, indicating that manipulation of the hippocampus produced a blockade of the shift to response learning. Rats receiving intracaudate injections of glutamate displayed response learning on days 8 and 16, indicating an accelerated shift to response learning. The findings suggest that posttraining intracerebral glutamate infusions can (
i
) modulate the distinct memory processes mediated by the hippocampus and caudate-putamen and (
ii
) bias the brain toward the use of a specific memory system to control learned behavior and thereby influence the timing of the switch from the use of cognitive memory to habit learning to guide behavior.
Revival and Survival in Iugra
Authors: Ruttkay-Miklián Eszter
Published: July 2002

In the administrative usage of the Soviet Union, the category “minor peoples of the North” embraced 26 ethnic groups of the North and the Far East. According to 1989 data, the populations of these groups ranged from 179 to 34,190 and together totaled 181,500. In addition to being small in numbers, the common denominators of the groups include a northern location and dependence on such sources of livelihood as hunting, reindeer herding, and fishing. Furthermore, some of these peoples remain nomadic or semi-nomadic.
Soil Contamination and Human Exposure: A Comprehensive Assessment Framework
Authors: McKone Thomas E. , Maddalena Randy L.
Published: July 2002

Soil is the thin outer zone of the earth's crust that supports rooted plants and is the product of climate and living organisms acting on rock. Throughout the world, soils are contaminated to some extent by local, regional, and global pollution sources of both natural and human origin. Sources of soil contamination are identified and discussed. With the possible exception of agricultural applications of pesticides and fertilizers, most contaminant releases to soil are not easily quantified and, as a result, remain highly uncertain. In establishing a comprehensive framework for human exposure to soil contaminants, it is revealed that such exposure occurs through multiple transfer processes. The process for linking human exposure to soil contact is considered and it is found that the magnitude and persistence of exposure depend not only on the level of soil contamination but also on physical and chemical properties of soil, chemical properties of the contaminant, and the frequency and duration of human factors such as occupational and recreational activities or the consumption of home-grown food, which result in direct and indirect soil contact. All of these factors possess some degree of variance that leads to probability distributions for representing total exposure and risk.
Public Health Needs for Exposure Assessment and its Realization in Germany
Authors: Sagunski Helmut , Neus Hermann , Ollroge Inga , Kappos Andreas D.
Published: July 2002

In 1995, the Committee for Environmental Hygiene of the German State Ministers of Health released a report entitled “Exposure Assessment Standards.” To respond to public needs of communicating potential environmental health risks, the report is divided into two parts. The methodological chapter addresses several key issues in the field of exposure assessment, such as variability and uncertainty of environmental and human data, the effects of typical versus worst-case scenarios and of point estimates versus probabilistic density functions, and the hidden safety of cumulative models. Based on these prerequisites and limitations, the report describes the underlying studies from which recommendations for exposure factors are derived. Regarding soil contamination, regulatory consequences remain questionable. Because assumptions about soil intake by children are still based on very limited data and even the source (house dust or soil) is not well defined, the basis for regulatory efforts is unsatisfactory. Whenever feasible, human biomonitoring should be used to validate exposure assessment.
Toxicokinetic Modeling as a Tool for Risk Estimation: 2,3,7,8-Tetrachlorodibenzo-P-Dioxin
Authors: Filser J. G. , Baur C. , Csan Ädy A. , Kessler W. , Kreuzer P. E.
Published: July 2002

Concepts of toxicokinetic modeling and the relevance of toxicokinetics for understanding dose-response relationships, species scaling, and risk estimation are broached. A physiological one-compartment model for 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD) is presented in detail. It describes the TCDD burden of the human body, which results from TCDD-contaminated food, in dependence of age. The model was validated using a series of measured values obtained by other authors and this group. They represent lipid-based concentrations of TCDD in liver, blood, adipose tissue, feces, and mother's milk in dependence of age. Special attention was paid to the TCDD burden in infants resulting from feeding with mother's milk or formula. Model simulations demonstrate that TCDD burden can amount to 10 mg/kg of lipids after nursing for 6 months with mother's milk exclusively This is still within the range of the concentrations found in adults. After the nursing period, TCDD burden declines. From the age of 7 years on, there is no longer a difference in the TCDD burden, independently of the food they had received as infants. According to the model, elimination half-life of TCDD from the body is not constant but increases during life starting from a few months in newborns to several years in adults.
Macroglossia and speech in Beckwith‐Wiedemann syndrome: a sample survey study
Authors: Van Borsel John , Van Snick Kathleen , Leroy Jules
Published: July 2002

In a sample survey study (questionnaires filled out by parents), all 40 patients with Beckwith‐Wiedemann Syndrome (BWS) presented with macroglossia. Articulation problems were reported in 29 of them, which persisted in some following corrective tongue surgery. The impression emerges that the value of surgical treatment needs prospective assessment, that the parents are insufficiently informed, and that the adequacy of direct articulation therapy in BWS needs to be evaluated.