bluuebunny/crossref_metadata_2025 huggingface dataset:
Tree rings, carbon dioxide, and climatic change
Authors: Jacoby Gordon C. , D’Arrigo Rosanne D.
Published: July 2002

Tree rings have been used in various applications to reconstruct past climates as well as to assess the effects of recent climatic and environmental change on tree growth. In this paper we briefly review two ways that tree rings provide information about climate change and CO2: (i) in determining whether recent warming during the period of instrumental observations is unusual relative to prior centuries to millennia, and thus might be related to increasing greenhouse gases; and (ii) in evaluating whether enhanced radial growth has taken place in recent decades that appears to be unexplained by climate and might instead be due to increasing atmospheric CO2or other nutrient fertilization. It is found that a number of tree-ring studies from temperature-sensitive settings indicate unusual recent warming, although there are also exceptions at certain sites. The present tree-ring evidence for a possible CO2fertilization effect under natural environmental conditions appears to be very limited.
Tumor necrosis factor α plays a central role in immune-mediated clearance of adenoviral vectors
Authors: Elkon Keith B. , Liu Chau-Ching , Gall Jason G. , Trevejo Jose , Marino Michael W. , Abrahamsen Karil A. , Song Xin , Zhou Jun-Liang , Old Lloyd J. , Crystal Ronald G. , Falck-Pedersen Erik
Published: July 2002

Adenovirus (Ad) gene transfer vectors are rapidly cleared from infected hepatocytes in mice. To determine which effector mechanisms are responsible for elimination of the Ad vectors, we infected mice that were genetically compromised in immune effector pathways [perforin, Fas, or tumor necrosis factor α (TNF-α)] with the Ad vector, Ad5-chloramphenicol acetyl transferase (CAT). Mice were sacrificed at 7–60 days postinfection, and the levels of CAT expression in the liver determined by a quantitative enzymatic assay. When the livers of infected mice were harvested 28 days postinfection, the levels of CAT expression revealed that the effectors most important for the elimination of the Ad vector were TNF-α > Fas > perforin. TNF-α did not have a curative effect on infected hepatocytes, as the administration of TNF-α to infected severe combined immunodeficient mice or to infected culturesin vitrohad no specific effect on virus persistence. However, TNF-α-deficient mice demonstrated a striking reduction in the leukocytic infiltration early on in the infection, suggesting that TNF-α deficiency resulted in impaired recruitment of inflammatory cells to the site of inflammation. In addition, the TNF-deficient mice had a significantly reduced humoral immune response to virus infection. These results demonstrate a dominant role of TNF-α in elimination of Ad gene transfer vectors. This result is particularly important because viral proteins that disable TNF-α function have been removed from most Ad vectors, rendering them highly susceptible to TNF-α-mediated elimination.
Activation of distinct caspase-like proteases by Fas and reaper in Drosophila cells
Authors: Kondo Toru , Yokokura Takakazu , Nagata Shigekazu
Published: July 2002

The cytoplasmic region of Fas, a mammalian death factor receptor, shares a limited homology with reaper, an apoptosis-inducing protein inDrosophila. Expression of either the Fas cytoplasmic region (FasC) or of reaper inDrosophilacells caused cell death. The death process induced by FasC or reaper was inhibited by crmA or p35, suggesting that its death process is mediated by caspase-like proteases. Both Ac-YVAD aldehyde and Ac-DEVD aldehyde, specific inhibitors of caspase 1- and caspase 3-like proteases, respectively, inhibited the FasC-induced death ofDrosophilacells. However, the cell death induced by reaper was inhibited by Ac-DEVD aldehyde, but not by Ac-YVAD aldehyde. A caspase 1-like protease activity that preferentially recognizes the YVAD sequence gradually increased in the cytosolic fraction of the FasC-activated cells, whereas the caspase 3-like protease activity recognizing the DEVD sequence was observed in the reaper-activated cells. Partial purification and biochemical characterization of the proteases indicated that there are at least three distinct caspase-like proteases inDrosophilacells, which are differentially activated by FasC and reaper. The conservation of the Fas-death signaling pathway inDrosophilacells, which is distinct from that for reaper, may indicate that cell death inDrosophilais controlled not only by the reaper suicide gene, but also by a Fas-like killer gene.
An unusual histone H3 specific for early macronuclear development in
Euplotes crassus
Authors: Jahn Carolyn L. , Ling Zhong , Tebeau Christopher M. , Klobutcher Lawrence A.
Published: July 2002

Characterization of the histone H3 genes of the ciliated protozoan
Euplotes crassus
indicates that one gene functions only during the sexual phase of the life cycle. Maximum expression of this gene, as judged by transcript accumulation, correlates with DNA replications leading to polytenization of the micronuclear chromosomes before massive DNA elimination, which produces a transcriptionally active macronucleus. Transcripts of the other gene accumulate primarily during vegetative growth and in the sexual phase of the life cycle during replication phases not related to polytenization. Although both histone H3 genes encode proteins that are fairly divergent in sequence at the amino terminus, the meiotic/polytene-specific histone H3 contains two insertions in the amino terminus that increase the size of the protein by 15 amino acids. Analysis of micrococcal nuclease digests of chromatin using hybridization probes specific for micronuclear vs. macronuclear sequences indicates that a change in nucleosomal spacing correlates with the maximal expression of the meiotic/polytene-specific histone H3 gene. Thus, we surmise that this unusual histone H3 may play a key role in targeting DNA sequences for either transcriptional activation and retention in the macronucleus or heterochromatization and elimination.
Gene 4 helicase of bacteriophage T7 mediates strand transfer through pyrimidine dimers, mismatches, and nonhomologous regions
Authors: Kong Daochun , Griffith Jack D. , Richardson Charles C.
Published: July 2002

In bacteriophage T7 the gene
2.5
single-stranded DNA-binding protein and the gene
4
helicase together promote the annealing of homologous regions of two DNA partners to form a joint molecule and subsequent strand transfer. In this reaction T7 gene
2.5
protein is essential for joint molecule formation, but is not required for T7 gene
4
protein-mediated strand transfer. T7 gene
4
helicase alone is able to mediate strand transfer, provided that a joint molecule is available. The present paper shows that, in addition, strand transfer proceeds at a normal rate even when both DNA partners contain ultraviolet-induced pyrimidine dimers (0.6 dimer per 100 nt). An insert of a relatively long (842-nt) segment of nonhomologous DNA in the single-stranded DNA partner has no effect on strand transfer, whereas its presence in the double-stranded partner prevents strand transfer. A short insert (37 nt) can be tolerated in either partner. Thus, DNA helicase is able to participate in recombinational DNA repair through its role in strand exchange, providing a pathway distinct from nucleotide excision repair.
T and B lymphocytes play a minor role in atherosclerotic plaque formation in the apolipoprotein E-deficient mouse
Authors: Dansky Hayes M. , Charlton Sherri A. , Harper Monnie McGee , Smith Jonathan D.
Published: July 2002

Cellular and humoral immunity have been implicated in the pathogenesis of atherosclerosis. To determine whether an intact immune system is necessary for the formation of atherosclerotic lesions, we have generated immunodeficient mice with hypercholesterolemia and atherosclerosis by crossbreeding the apolipoprotein E (apoE)-deficient mouse with the recombinase activating gene 1 (
Rag-1
) knockout mouse. Chow-fed immunodeficient mice with targeted disruption in both apoE and
Rag-1
(E0/R0) had a 2-fold decrement in aortic root lesion size at 16 weeks of age, compared with immunocompetent littermates, which were heterozygotes at the
Rag-1
locus (E0/R1). Nearly all atherosclerotic lesions from chow-fed animals were limited to raised foam cell fatty streaks. In contrast, when a second group of animals was fed a high-fat Western-type diet to accelerate lesion development, there were no differences in either aortic root lesion size or the percent of the total aorta occupied by lesions. Fibrous plaques with well-defined caps and necrotic cores were detected in both Western diet-fed E0/R0 and E0/R1 animals. We conclude that T and B lymphocytes play only a minor role in the rate of forming foam cell lesions, and they are not necessary for the formation of fibroproliferative plaques.
Alternative splicing of rearranged T cell receptor δ sequences to the constant region of the α locus
Authors: Livák Ferenc , Schatz David G.
Published: July 2002

The T cell receptor (TCR) α/δ locus is composed of a common, shared set of variable (V) and distinct diversity (D), joining (J), and constant (C) genes. It has been recognized for several years that transcripts of the rearranged VDJδ or VJα genes are spliced to the Cδ or Cα genes, respectively, encoding distinct TCR δ and α proteins. Herein, we describe the discovery of a splicing variation that allows the assembled VDJδ genes to be fused with the Cα gene. This variation is prominent in TCRδ gene-deficient mice but is also detectable in wild-type mice. Furthermore, we show that several in-frame VDJδ rearrangements in TCRδ gene-deficient mice are strikingly underrepresented, suggesting that the alternative transcripts, with protein coding capacity, influence the development of αβ thymocytes. In-frame TCRγ gene rearrangements do not appear underrepresented, indicating that the effect is not mediated by the γ chain. Instead, indirect evidence supports the hypothesis that the δ/α chimeric protein acts in conjunction with the TCRβ chain. These results have implications for the transcriptional control of the TCRα/δ locus and provide a novel insight into the distinct functional capacities of the TCR α and δ proteins during thymocyte development.
Lineage commitment in the progeny of murine hematopoietic preprogenitor cells: Influence of thrombopoietin and interleukin 5
Authors: Metcalf Donald
Published: July 2002

Normal mouse marrow cells were stimulated by stem cell factor (SCF) to form dispersed or multicentric blast colonies containing progenitor cells committed to various hematopoietic lineages. Combination of the eosinophil-specific regulator interleukin 5 with SCF increased the frequency of colonies containing eosinophil-committed progenitor cells with multicentric but not dispersed blast colonies. Combination of thrombopoietin with SCF increased the frequency of colonies containing megakaryocyte-committed progenitor cells with both types of blast colony. Neither interleukin 5 nor thrombopoietin significantly altered the number or total cell content of blast colonies or progenitor cell numbers in blast colonies from those stimulated by SCF alone. No correlation was observed between total progenitor cell content and the presence or absence of either eosinophil or megakaryocyte progenitors in either type of blast colony. The data argue against a random process as being responsible for the formation of particular committed progenitor cells or the possibility that lineage-specific regulators merely enhance survival of such committed progenitor cells formed in developing blast colonies.
Retardation of skeletal development and cervical abnormalities in transgenic mice expressing a dominant-negative retinoic acid receptor in chondrogenic cells
Authors: Yamaguchi Masahiro , Nakamoto Mika , Honda Hiroaki , Nakagawa Toshiyuki , Fujita Hiroshi , Nakamura Takashi , Hirai Hisamaru , Narumiya Shuh , Kakizuka Akira
Published: July 2002

Skeletal formation is a fundamental element of body patterning and is strictly regulated both temporally and spatially by a variety of molecules. Among these, retinoic acid (RA) has been shown to be involved in normal skeletal development. However, its pleiotropic effects have caused difficulty in identifying its crucial target cells and molecular mechanisms for each effect. Development of cartilage primordia is an important process in defining the skeletal structures. To address the role of RA in skeletal formation, we have generated mice expressing a dominant-negative retinoic acid receptor (RAR) in chondrogenic cells by using the type II collagen α1 promoter, and we have analyzed their phenotypes. These mice exhibited small cartilage primordia during development and retarded skeletal formation in both embryonic and postnatal periods. They also showed selective degeneration in their cervical vertebrae combined with homeotic transformations, but not in their extremities. The cervical phenotypes are reminiscent of phenotypes involving homeobox genes. We found that the expression of
Hoxa-4
was indeed reduced in the cartilage primordia of cervical vertebrae of embryonic day 12.5 embryos. These observations demonstrate that endogenous RA acts directly on chondrogenic cells to promote skeletal growth in both embryonic and growing periods, and it regulates the proper formation of cervical vertebrae. Furthermore, RA apparently specifies the identities of the cervical vertebrae through the regulation of homeobox genes in the chondrogenic cells. Great similarities of the phenotypes between our mice and reported RAR knockout mice revealed that chondrogenic cells are a principal RA target during complex cascades of skeletal development.
Mitogen-activated protein kinases enhance long-range activation by the β-globin locus control region
Authors: Versaw Wayne K. , Blank Volker , Andrews Nancy M. , Bresnick Emery H.
Published: July 2002

The human β-globin locus control region (LCR), which consists of four erythroid-specific DNase I hypersensitive sites (HS1–HS4), functions over a long distance to control the transcription, chromatin structure, and replication of the β-globin genes. We have used stable transfection assays to show that activation of the mitogen-activated protein (MAP) kinase pathway by low concentrations of the phorbol ester phorbol 12-tetradecanoate 13-acetate (TPA) induces enhancer activity of the LCR subregion HS2, but not HS3. Although HS2 enhancer activity is diminished with increasing distance from the promoter, the relative level of induction by TPA is independent of HS2–promoter distance. Mutation of cis-elements within HS2 reveals that the tandem-binding sites for the hematopoietic-specific transcription factor NF-E2 are required for induction by TPA, and induction is conferred by expressing NF-E2 in an NF-E2-null cell line. These results show that MAP kinases target factors functioning through the NF-E2 sites to enhance long-range transactivation by the LCR.
Ferredoxin-1 mRNA is destabilized by changes in photosynthetic electron transport
Authors: Petracek Marie E. , Dickey Lynn F. , Nguyen Tuyen T. , Gatz Christiane , Sowinski Dolores A. , Allen George C. , Thompson William F.
Published: July 2002

In transgenic tobacco, pea Ferredoxin-1 (
Fed-1
) mRNA accumulates rapidly in response to photosynthesis even when the transgene is driven by a constitutive promoter. To investigate the role of photosynthesis on
Fed-1
mRNA stability, we used the tetracycline repressible Top10 promoter system to specifically shut off transcription of the
Fed-1
transgene. The
Fed-1
mRNA has a half-life of approximately 2.4 hr in the light and a half-life of only 1.2 hr in the dark or in the presence of the photosynthetic electron transport inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). These data indicate that cessation of photosynthesis, either by darkness or DCMU results in a destabilization of the
Fed-1
mRNA. Furthermore, the
Fed-1
mRNA half-life is reduced immediately upon transfer to darkness, suggesting that
Fed-1
mRNA destabilization is a primary response to photosynthesis rather than a secondary response to long-term dark adaptation. Finally, the two different methods for efficient tetracycline delivery reported here generally should be useful for half-life measurements of other mRNAs in whole plants.
Design, synthesis, and characterization of a photoactivatable flavocytochrome molecular maquette
Authors: Sharp R. Eryl , Moser Christopher C. , Rabanal Francesc , Dutton P. Leslie
Published: July 2002

We report the construction of a synthetic flavo-heme protein that incorporates two major physiological activities of flavoproteins: light activation of flavin analogous to DNA photolyase and rapid intramolecular electron transfer between the flavin and heme cofactors as in several oxidoreductases. The functional tetra-α-helix protein comprises two 62-aa helix-loop-helix subunits. Each subunit contains a single cysteine to which flavin (7-acetyl-10-methylisoalloxazine) is covalently attached and two histidines appropriately positioned for
bis
-his coordination of heme cofactors. Both flavins and hemes are situated within the hydrophobic core of the protein. Intramolecular electron transfer from flavosemiquinone generated by photoreduction from a sacrificial electron donor in solution was examined between protoporphyrin IX and 1-methyl-2-oxomesoheme XIII. Laser pulse-activated electron transfer from flavin to meso heme occurs on a 100-ns time scale, with a favorable free energy of approximately −100 meV. Electron transfer from flavin to the lower potential protoporphyrin IX, with an unfavorable free energy, can be induced after a lag phase under continuous light illumination. Thus, the supporting peptide matrix provides an excellent framework for the positioning of closely juxtaposed redox groups capable of facilitating intramolecular electron transfer and begins to clarify in a simplified and malleable system the natural engineering of flavoproteins.
Segment-specific pattern of sympathetic preganglionic projections in the chicken embryo spinal cord is altered by retinoids
Authors: Forehand Cynthia J. , Ezerman Elizabeth B. , Goldblatt John P. , Skidmore David L. , Glover Joel C.
Published: July 2002

Sympathetic preganglionic neurons exhibit segment-specific projections. Preganglionic neurons located in rostral spinal segments project rostrally within the sympathetic chain, those located in caudal spinal segments project caudally, and those in midthoracic segments project either rostrally or caudally in segmentally graded proportions. Moreover, rostrally and caudally projecting preganglionic neurons are skewed toward the rostral and caudal regions, respectively, of each midthoracic segment. The mechanisms that establish these segment-specific projections are unknown. Here we show that experimental manipulation of retinoid signaling in the chicken embryo alters the segment-specific pattern of sympathetic preganglionic projections and that this effect is mediated by the somitic mesoderm. Application of exogenous retinoic acid to a single rostral thoracic somite decreases the number of rostrally projecting preganglionic neurons at that level. Conversely, disrupting endogenous synthesis of retinoic acid in a single caudal thoracic somite increases the number of rostrally projecting preganglionic neurons at that level. The number of caudally projecting neurons does not change in either case, indicating that the effect is specific for rostrally projecting preganglionic neurons. These results indicate that the sizes of the rostrally and caudally projecting populations may be independently regulated by different factors. Opposing gradients of such factors along the longitudinal axis of the thoracic region of the embryo could be sufficient, in combination, to determine the segment-specific identity of preganglionic projections.
Expression and crystallization of the complex of HLA-DR2 (DRA, DRB1*1501) and an immunodominant peptide of human myelin basic protein
Authors: Gauthier Laurent , Smith Kathrine J. , Pyrdol Jason , Kalandadze Avtandil , Strominger Jack L. , Wiley Don C. , Wucherpfennig Kai W.
Published: July 2002

HLA-DR2 is associated with susceptibility to multiple sclerosis (MS). A peptide from human myelin basic protein (MBP, residues 85–99) was previously found to bind to purified HLA-DR2 (DRA, DRB1*1501) and to be recognized by human MBP-specific T cell clones. Soluble HLA-DR2 was expressed in the baculovirus system by replacing the hydrophobic transmembrane regions and cytoplasmic segments of DRα and DRβ with leucine zipper dimerization domains from the transcription factors Fos and Jun. In the expression construct, the MBP(85–99) sequence was covalently linked to the N terminus of the mature DRβ chain. The recombinant protein was secreted by Sf9 cells infected with the recombinant baculovirus and purified by affinity chromatography. The leucine zipper dimerization domains were then cleaved from the assembled HLA-DR2/MBP peptide complex with V8 protease, and the protein was further purified by anion-exchange HPLC. Analysis by HPLC gel filtration indicated that the HLA-DR2/MBP peptide complex did not have a tendency to aggregate. The purified HLA-DR2/MBP peptide complex readily crystallized by the hanging drop method in 15–18% polyethylene glycol 6000/100 mM glycine, pH 3.5. At a synchrotron radiation source, a crystal with a tetragonal space group diffracted to a resolution of 2.6 Å. The expression of such homogenous HLA-DR/peptide complexes may facilitate cocrystallization with T cell receptors as well as other molecules involved in T cell receptor recognition and signaling.
In vivo
characterization of the type A and B vancomycin-resistant enterococci (VRE) VanRS two-component systems in
Escherichia coli
: A nonpathogenic model for studying the VRE signal transduction pathways
Authors: Silva Jeffrey C. , Haldimann Andreas , Prahalad Murali K. , Walsh Christopher T. , Wanner Barry L.
Published: July 2002

Escherichia coli
reporter strains modeling the high-level type A and B vancomycin resistances of
Enterococcus faecium
BM4147 and
Ent. faecalis
have been developed to study the respective VanR-VanS two-component regulatory systems.
P
vanH
-,
P
vanRa
-,
P
vanY
-, and
P
vanRb
-
lacZ
fusions report on expression from the vancomycin-resistant enterococci promoters of the type A
vanRSHAXYZ
and type B
vanRSYWHBX
gene clusters. These strains also express from single-copy chromosomal genes
vanR
a
,
vanR
b
, or
vanRS
b
behind their respective promoter (
P
vanRa
or
P
vanRb
) or
vanS
a
or
vanS
b
behind the rhamnose-inducible
P
rhaB
. Results show that activation (phosphorylation) of the response regulator VanR
a
by its sensor kinase VanS
a
leads to transcriptional activation of both
P
vanH
and
P
vanRa
. Additionally, VanR
b
activates its cognate promoters
P
vanY
and
P
vanRb
, although this occurs only in the absence of VanS
b
and presumably is caused by VanR
b
phosphorylation by an unidentified endogenous
E. coli
kinase. Thus, VanS
b
interferes with activation of VanR
b
, probably by acting as a phospho-VanR
b
phosphatase. Although both VanR
a
and VanR
b
activate their cognate promoters, neither activates the heterologous
P
vanR
,
P
vanH
, or
P
vanY
, arguing against the interchangeability of type A and B two-component regulatory switches in vancomycin-resistant enterococci. VanR
a
also is activated by the nonpartner kinase PhoR. Because this occurs in the absence of its inducing signal (P
i
limitation), PhoR autophosphorylation apparently is regulated
in vivo
. Furthermore, the activation of VanR
a
caused by cross talk from PhoR in the absence of a signal allows distinction of cross talk from crossregulation as the latter, but not the former, responds to environmental cues.
Activity and nature of p21
WAF1
complexes during the cell cycle
Authors: Cai Kang , Dynlacht Brian David
Published: July 2002

Elevated levels of the p21
WAF1
(p21) cyclin-dependent kinase inhibitor induce growth arrest. We have characterized a panel of monoclonal antibodies against human p21 in an effort to understand the dynamic regulatory interactions between this and other cellular proteins during the cell cycle. The use of these reagents has allowed us to address several important, yet unresolved, issues concerning the biological activity of p21, including the potential kinase activity of complexes that associate with this cyclin-dependent kinase inhibitor. We have found that the kinase activity of cyclin A/Cdk2 associated with p21 is significantly lower than that of cyclin A/Cdk2 free of p21, suggesting that p21 abolishes its activity
in vivo
, and the use of multiple antibodies has enabled us to begin the study of the molecular architecture of p21 complexes
in vivo
. In addition, we found that human fibroblasts released from a quiescent state display abundant amounts of p21 devoid of associated proteins (“free” p21), the levels of which decrease as cells approach S phase. Cyclin A levels increase as the amount of monomeric p21 decreases, resulting in an excess of cyclin A/Cdk2 complexes that are not bound to, or inactivated by, p21. Our data strengthen the notion that the G
1
-to-S phase transition in human fibroblasts occurs when the concentration of cyclin A/Cdk2 surpasses that of p21.
Oncogene-dependent apoptosis is mediated by caspase-9
Authors: Fearnhead Howard O. , Rodriguez Joe , Govek Eve-Ellen , Guo Wenjun , Kobayashi Ryuji , Hannon Greg , Lazebnik Yuri A.
Published: July 2002

Understanding how oncogenic transformation sensitizes cells to apoptosis may provide a strategy to kill tumor cells selectively. We previously developed a cell-free system that recapitulates oncogene dependent apoptosis as reflected by activation of caspases, the core of the apoptotic machinery. Here, we show that this activation requires a previously identified apoptosis-promoting complex consisting of caspase-9, APAF-1, and cytochrome
c
. As predicted by the
in vitro
system, preventing caspase-9 activation blocked drug-induced apoptosis in cells sensitized by E1A, an adenoviral oncogene. Oncogenes, such as E1A, appear to facilitate caspase-9 activation by several mechanisms, including the control of cytochrome
c
release from the mitochondria.
Anti-CD14 mAb treatment provides therapeutic benefit after
in vivo
exposure to endotoxin
Authors: Schimke Jan , Mathison John , Morgiewicz Janice , Ulevitch Richard J.
Published: July 2002

The presence of endotoxin from Gram-negative bacteria signals the innate immune system to up-regulate bacterial clearance and/or killing mechanisms. Paradoxically, such responses also contribute to septic shock, a clinical problem occurring with high frequency in Gram-negative septicemia. CD14 is a receptor for endotoxin (lipopolysaccharide, LPS) and is thought to have an essential role in innate immune responses to infection and thereby in the development of septic shock. Using a novel rabbit model of endotoxic shock produced by multiple exposures to endotoxin, we show that anti-rabbit CD14 mAb, which blocks LPS-CD14 binding, protects against organ injury and death even when the antibody is administered after initial exposures to LPS. In contrast, anti-rabbit tumor necrosis factor mAb treatment fails to protect when administered after LPS injections. These results support the concept that anti-CD14 treatment provides a new therapeutic window for the prevention of pathophysiologic changes that result from cumulative exposures to LPS during septic shock in man.
Plant genome values: How much do we know?
Authors: Bennett Michael D.
Published: July 2002

Plants are the basis of life on earth. We cannot overemphasize
their importance. The value of plant genome initiatives is
self-evident. The need is to identify priorities for action. The
angiosperm genome is highly variable, but the extent of this
variability is unknown. Uncertainties remain about the number of genes
and the number of species living. Many plants will become extinct
before they are discovered. We risk losing both genes and vital
information about plant uses. There are also major gaps in our
karyotypic knowledge. No chromosome count exists for >70% of
angiosperm species. DNA C values are known for only ≈1% of
angiosperms, a sample unrepresentative of the global flora. Researchers
reported new relationships between genome size and characters of major
interest for plant breeding and the environment and the need for more
data. In 1997, a Royal Botanic Gardens Kew workshop identified gaps and
planned international collaboration to fill them. An electronic version
of the Angiosperm DNA C value database also was published. Another
initiative, which will make a very significant contribution to the
conservation of plant genetic diversity on a global scale is Kew’s
Millennium Seed Bank, partly funded by the U.K. Millennium Commission,
celebrating the year 2000. Costing up to £80 million (£1 =
$1.62), its main aims are to collect and conserve the seed of almost
all of the U.K. spermatophyte flora by the year 2000, to collect and
conserve a further 10% of the world spermatophyte flora principally
from the drylands by 2009, and to provide a world class building as the
focus of this activity by 2000.
Identification of a substrate-targeting domain in cyclin E necessary for phosphorylation of the retinoblastoma protein
Authors: Kelly Beth L. , Wolfe Karen G. , Roberts James M.
Published: July 2002

Considerable advances have been made in characterizing the cyclins and cyclin-dependent kinases (CDKs) that are necessary for progression through the cell cycle, but there has been relatively lesser success in identifying the specific biochemical pathways and cell cycle events that are directly under CDK control. To identify physiologically significant CDK substrates we generated mutations in cyclin E that altered the ability of the cyclin to direct the cyclin–CDK holoenzyme to specific
in vivo
substrates. We show that one of these mutations defines a domain in cyclin E necessary for phosphorylation of the retinoblastoma protein (Rb). These observations confirm the idea that cyclins contribute to substrate recognition by cyclin–CDK complexes, demonstrate the utility of targeting mutants in the identification of essential cyclin–CDK substrates, and put cyclin E squarely into the family of proteins designed to regulate Rb.
Recruitment of SH2-containing protein tyrosine phosphatase SHP-1 to the interleukin 2 receptor; loss of SHP-1 expression in human T-lymphotropic virus type I-transformed T cells
Authors: Migone Thi-Sau , Cacalano Nicholas A. , Taylor Naomi , Yi Taolin , Waldmann Thomas A. , Johnston James A.
Published: July 2002

Interleukin 2 (IL-2) rapidly induces tyrosine phosphorylation of intracellular substrates, including the IL-2 receptor β chain (IL-2Rβ), Janus kinase 1 (Jak1), Jak3, signal transducer/activator of transcription proteins, and Shc, but the mechanism underlying dephosphorylation of these proteins is not known. The src homology 2 (SH2) containing tyrosine phosphatase 1 (SHP-1) is recruited by several hematopoietic surface receptors indicating that this phosphatase plays an important role as a regulator of signaling. We have found that IL-2 induces association of SHP-1 with the IL-2 receptor complex, and that once SHP-1 is recruited to the activated receptor it is able to decrease tyrosine phosphorylation of IL-2Rβ and the associated tyrosine kinases Jak1 and Jak3. This dephosphorylation is specific as expression of a catalytically inactive form of SHP-1, or expression of the related phosphatase SHP-2 did not result in dephosphorylation of the IL-2 receptor components. Furthermore, we have found that SHP-1 expression is greatly decreased or undetectable in a number of IL-2 independent HTLV-I transformed T cell lines that exhibit constitutive Jak/signal transducer/activator of transcription activation. In HTLV-I infected T cells, down-regulation of SHP-1 expression was also found to correlate with the acquisition of IL-2 independence. These observations suggest that SHP-1 normally functions to antagonize the IL-2 signal transduction pathway and that HTLV-I infection and oncogenic transformation can lead to loss of SHP-1 expression resulting in constitutive activation of IL-2 regulated T cell responses.
The C terminus of β-tubulin regulates vinblastine-induced tubulin polymerization
Authors: Rai Sadananda S. , Wolff J.
Published: July 2002

Oligoanions such as sodium triphosphate or GTP prevent and/or reverse vinblastine-induced polymerization of tubulin. We now show that the anions of glutamate-rich extreme C termini of tubulin are similarly involved in the regulation of the vinblastine effect. Cleavage of the C termini by limited proteolysis with subtilisin enhances vinblastine-induced tubulin polymerization and abolishes the anion effect. Only the β-tubulin C terminus needs to be removed to achieve these changes and the later cleavage of the α-tubulin C terminus has little additional effect. In fact, vinblastine concentrations >20 μM block cleavage of the α-tubulin C terminus in the polymer, whereas cleavage of the β-tubulin C terminus proceeds unimpeded over the time used. The vinblastine effect on tubulin polymerization is also highly pH-dependent between pH 6.5 and 7.5; this is less marked, but not absent, after subtilisin treatment. A working model is proposed wherein an anionic domain proximal to the extreme C terminus must interact with a cationic domain to permit vinblastine to promote polymerization. Both exogenous and extreme C-terminal anions compete for the cationic domain with the proximal anionic domain to prevent vinblastine-induced polymerization. We conclude that the electrostatic regulation of tubulin polymerization induced by vinblastine resides primarily in the β-tubulin C terminus but that additional regulation proximal in the tubulin molecule also plays a role.
Distinct leukemia phenotypes in transgenic mice and different corepressor interactions generated by promyelocytic leukemia variant fusion genes
PLZF–RAR
α and
NPM–RAR
α
Authors: Cheng G.-X. , Zhu X.-H. , Men X.-Q. , Wang L. , Huang Q.-H. , Jin X. L. , Xiong S.-M. , Zhu J. , Guo W.-M. , Chen J.-Q. , Xu S.-F. , So E. , Chan L.-C. , Waxman S. , Zelent A. , Chen G.-Q. , Dong S. , Liu J.-X. , Chen S.-J.
Published: July 2002

Acute promyelocytic leukemia (APL) is characterized by a specific chromosome translocation involving
RAR
α and one of four fusion partners:
PML
,
PLZF
,
NPM
, and
NuMA
genes. To study the leukemogenic potential of the fusion genes
in vivo
, we generated transgenic mice with
PLZF–RAR
α and
NPM–RAR
α.
PLZF–RAR
α transgenic animals developed chronic myeloid leukemia-like phenotypes at an early stage of life (within 3 months in five of six mice), whereas three
NPM–RAR
α transgenic mice showed a spectrum of phenotypes from typical APL to chronic myeloid leukemia relatively late in life (from 12 to 15 months). In contrast to bone marrow cells from
PLZF–RAR
α transgenic mice, those from
NPM–RAR
α transgenic mice could be induced to differentiate by all-
trans
-retinoic acid (ATRA). We also studied RARE binding properties and interactions between nuclear corepressor SMRT and various fusion proteins in response to ATRA. Dissociation of SMRT from different receptors was observed at ATRA concentrations of 0.01 μM, 0.1 μM, and 1.0 μM for RARα–RXRα, NPM–RARα, and PML–RARα, respectively, but not observed for PLZF–RARα even in the presence of 10 μM ATRA. We also determined the expression of the tissue factor gene in transgenic mice, which was detected only in bone marrow cells of mice expressing the fusion genes. These data clearly establish the leukemogenic role of PLZF–RARα and NPM–RARα and the importance of fusion receptor/corepressor interactions in the pathogenesis as well as in determining different clinical phenotypes of APL.
Activity regulation of Hox proteins, a mechanism for altering functional specificity in development and evolution
Authors: Li Xuelin , McGinnis William
Published: July 2002

The closely related Hox transcription factors Ultrabithorax (Ubx) and Antennapedia (Antp) respectively direct first abdominal (A1) and second thoracic (T2) segment identities in
Drosophila
. It has been proposed that their functional differences derive from their differential occupancy of DNA target sites. Here we show that a hybrid version of Ubx (Ubx-VP16), which possesses an enhanced transcriptional activation function, no longer directs A1 denticle pattern in embryonic epidermal cells. Instead, it mimics Antp in directing T2 denticle pattern, and it can rescue the cuticular loss-of-function phenotype of
Antp
mutants. In cells that do not produce denticles, Ubx-VP16 appears to have largely retained its normal repressive regulatory functions. These results suggest that the modulation of Hox activation and repression functions can account for segment-specific morphological differences that are controlled by different members of the Hox family. Our results also are consistent with the idea that activity regulation underlies the phenotypic suppression phenomenon in which a more posterior Hox protein suppresses the function of a more anterior member of the Hox cluster. The acquisition of novel activation and repression potentials in Hox proteins may be an important mechanism underlying the generation of subtle morphological differences during evolution.
rRNA-complementarity in the 5′ untranslated region of mRNA specifying the Gtx homeodomain protein: Evidence that base- pairing to 18S rRNA affects translational efficiency
Authors: Hu Michael C.-Y. , Tranque Pedro , Edelman Gerald M. , Mauro Vincent P.
Published: July 2002

Numerous eukaryotic mRNAs contain sequences complementary to
segments of the 18S and 28S rRNAs. Previous studies raised the
possibility that these complementarities might allow mRNA–rRNA
interactions and affect rates of translation. In the present study, we
investigated the mRNA encoding the mouse Gtx homeodomain protein. This
mRNA contains within its 5′ untranslated region (UTR) a segment that is
complementary to two regions of the 18S rRNA, located at nucleotides
701–741 and 1104–1136. A Gtx RNA probe containing this
complementarity could be photochemically cross-linked to ribosomal
subunits through a linkage to 18S rRNA but not to 28S rRNA.
Oligonucleotide-directed RNase H digestion of the rRNA and a reverse
transcription analysis localized the cross-linked probe to the
complementary segment of 18S rRNA at nucleotides 1104–1136 but not at
nucleotides 701–741. To determine whether complementarity in the Gtx
mRNA affected translation, a mutational analysis was performed with a
Gtx-luciferase fusion construct and four related constructs with
altered complementarity to the 18S rRNA. These constructs were examined
for their ability to be translated in cell-free lysates prepared from
P19 embryonal carcinoma and C6 glioma cell lines and after cellular
transfection into these same cell lines. In both cell-free translation
and transfection studies, the rate of translation decreased more than
9-fold as the degree of complementarity to nucleotides 1104–1136 of
the 18S rRNA increased. We hypothesize that segments complementary to
rRNA, such as those contained within the Gtx mRNA, form a category of
cis-acting regulatory elements in mRNAs that affect translation by base
pairing to rRNA within ribosomes.
Zeitgeist, Ortgeist, and personalities in the development of Scandinavian psychology
Authors: Lundberg Ingvar
Published: July 2002

Although the Scandinavian countries Denmark, Norway, Finland, and Sweden are most often perceived as a rather homogeneous set of nations there are interesting diversities in the paths and patterns of the development of psychology. The strong experimental, neurobiological, and cognitive orientation of psychology in Finland and Sweden is contrasted with the more phenomenologically and clinically oriented psychology in Norway and Denmark. The concepts of Zeitgeist, Ortgeist, and personalities are used to explain the different courses of development in the Scandinavian countries. In Denmark and Norway a few dominant personalities in a few dominant university departments seem to have shaped the formation of psychology to a greater extent than in Finland and Sweden. The relatively late start of psychology as an independent academic discipline has opened Sweden and Finland to impulses from the Anglo‐American empirical tradition. Within‐country differences are highlighted with special reference to the Swedish development. Various local “schools” of psychology are characterized with Stockholm as the most notable example. Although psychophysics plays an insignificant role in Swedish psychology today, a pedigree with reference to Gösta Ekman demonstrates its critical and dominating role for the development of psychology in Sweden.
Activities of the IUPsyS at the UN
Authors: Sabourin Michel
Published: July 2002

In the months to come, two major UN events are to take place and for both, the delegates of the IUPsyS have participated actively in the preparatory meetings that took place in 2000 and 2001. The first event to take place in New York is the UN Special Session on Children; it will be followed in July by the World Summit on Sustainable Development (26 August–4 September 2002) that will be held in Johannesburg, South Africa. The following descriptions are taken from the documentation available in preparation of these meetings.
Measuring Memory Span
Authors: Groeger John A. , Field David , Hammond Sean M.
Published: July 2002

This study, conducted on a sample of 403 adult subjects, set out to explore the relationships between measures of digit span (forward and reversed), motor and spatial span, and their dependence on a broad range of measures of cognitive function. The results revealed that measures of digit span are closely related, as are measures of motor and spatial span, but these pairs of memory span measures are relatively independent of each other. Furthermore, reverse digit span, motor span, and spatial span appear to rely on what might be regarded as intellectual or executive cognitive functions. As such, the results provide little support for accounts of serial recall, which suggest that order and/or item information are more adequately modelled in a modality‐independent form.
Item and Associative Interactions in Short‐term Memory: Multiple Memory Systems?
Authors: Murdock Bennet
Published: July 2002

Three interactions of item and associative information are discussed: differential forgetting (item recognition declines over lag ranges where pair recognition does not; Hockley, 1991); differential emphasis (instructions to attend to items degrade later pair recognition but instructions to attend to pairs does not degrade later item recognition; Hockley & Cristi, 1996a), and multiple presentations of pairs or items from pairs has little effect on judgements of frequency of items and pairs (Hockley & Cristi, 1996b). Taken as a whole, these results seem to be inconsistent with a separate memory‐systems view of memory. TODAM, a global‐matching model, has always assumed a single memory system for the storage and retrieval of item and associative information and, with the addition of context and mediators, it can generate the whole pattern of data.
Symbolism and racism in drug history and policy
Authors: MANDERSON DESMOND
Published: July 2002

The modern history of drug regulation began 100 years ago with the enactment of laws prohibiting the smoking of opium. In Australia and elsewhere, these laws manifested a fear of Chinese immigration. It was not opium as a substance with particular health effects which concerned the community, but opium as a symbol of transgression which the Chinese presence had elicited. Opium was prohibited because it represented an amalgam of race, sex and fear. This symbolic meaning was developed through the use of metaphor and metonymy. The author examines the way in which these strategies were deployed in the particular context of Australian anti‐opium laws. Drug laws continue to be about symbols and not substances, and are still and not least an expression of racism and fears of difference
Rapid opiate detoxification treatments
Authors: BEARN JENNIFER , GOSSOP MICHAEL , STRANG JOHN
Published: July 2002

Recent endeavours to improve the efficiency of treatment of the opiate withdrawal syndrome have resulted in the development of a variety of rapid opiate detoxification schedules, some of which are now in regular clinical use. The neuropharamacological basis of rapid withdrawal techniques, the evolution of treatment schedules and issues relating to clinical efficacy and safety are reviewed. Early studies with naloxone provided the basis for later refinements using opiate antagonists in conjunction with clonidine, benzodiazepines sedation and full anaesthesia. These treatments may accelerate the resolution of the opiate withdrawal syndrome; however, controlled studies comparing them with conventional treatments are lacking. There is insufficient evidence available to carry out an informed risk/benefit analysis. Rapid opiate detoxification treatments have considerable potential for increasing the speed and reducing the discomfort of the opiate withdrawal syndrome, but there is an urgent need for controlled clinical trials and outcome studies to determine their longer‐term impact on opiate use.
Separate and interactive effects of cocaine and alcohol dependence on brain structures and metabolites: quantitative MRI and proton MR spectroscopic imaging
Authors: O'Neill J. , Cardenas V. A. , Meyerhoff D. J.
Published: July 2002

The effects of chronic cocaine and alcohol abuse on human brain structure and metabolites are not fully known. We studied controls (n = 13) and abstinent subjects dependent on cocaine (8), alcohol (12), and cocaine and alcohol (17) using quantitative MRI and proton MR spectroscopic imaging. Talairach‐based techniques yielded tissue and CSF volumes and gray‐ and white‐matter concentrations of N‐acetylaspartate (NAA), creatine and choline metabolites in multiple brain regions. Alcohol dependents had lower gray‐matter NAA concentrations and more sulcal CSF than non‐alcohol dependents throughout the brain. They also had less subcortical gray matter and (regionally) less white matter. Cocaine dependents compared with non‐cocaine dependents had higher posterior parietal white‐matter creatine concentration. They also had less gray and white matter in the prefrontal lobes and in a region encompassing the temporal lobes and cerebellum. Structural white‐matter deficits in cocaine dependents were greater with longer duration of cocaine use. Subjects with concurrent cocaine and alcohol dependence had less prefrontal white matter, especially in the anterior cingulate, than subjects dependent on only one substance. Chronically abused cocaine and alcohol each leave multiple metabolic and structural brain defects after long‐term abstinence. Concurrent dependence on both substances may aggravate white‐matter structural defects, primarily in frontal brain.
Cerebrospinal fluid neuroendocrinology of alcohol misusers
Authors: GERACIOTI THOMAS D. , GOLDSMITH R. JEFFREY , FRIEDMAN LOREN M. , NORMAN ANDREW B. , SOMOZA EUGENE , KASCKOW JOHN W. , BAKER DEWLEEN G. , RICHTAND NEIL M. , ANTHENELLI ROBERT M. , KECK PAUL E.
Published: July 2002

Cerebrospinal fluid (CSF) neurohumors reflect central nervous system physiology in a way that peripheral indices can not. We reviewed clinical studies of CSF biogenic amines and neurohormones in alcohol misusers during various stages of withdrawal or abstinence and found them difficult to compare because of highly variable experimental methods, reliance on single time collections (lumbar punctures) that fail to control for potential stress‐induced effects of the procedure, lack of control for tobacco use, and a paucity of non‐alcoholmisusing controls. However, taken together, the data thus far show that a variety of neuroactive substances are reduced in concentration in the CSF of some alcohol misusers. Low CSF levels of corticotropinreleasing hormone, beta‐endorphin, norepinephrine, diazepam‐binding inhibitor, 5‐hydroxyindoleacetic acid and somatostatin have all been reported. Whether the decreased CSF levels of these neurohormones and neurotransmitters are a cause or consequence of alcoholism has not been determined. In fact, further studies using serial or continuous CSF sampling techniques with homogeneous, better‐characterized patients and normal volunteers are still needed to establish the precise CSF neurochemical abnormalities in alcohol misusers.