bluuebunny/crossref_metadata_2025 huggingface dataset:
Ocular cicatricial pemphigoid antigen: Partial sequence and biochemical characterization
Authors: Tyagi Shivraj , Bhol K. , Natarajan K. , Livir-Rallatos C. , Foster C. S. , Ahmed A. R.
Published: July 2002

Ocular cicatricial pemphigoid (OCP) is an autoimmune disease that
affects mainly conjunctiva and other squamous epithelia. OCP is
histologically characterized by a separation of the epithelium from
underlying tissues within the basement membrane zone.
Immunopathological studies demonstrate the deposition of anti-basement
membrane zone autoantibodies
in vivo
. Purified IgG from
sera of patients with active OCP identified a cDNA clone from a human
keratinocyte cDNA library that had complete homology with the
cytoplasmic domain of β4-integrin. The sera recognized a 205-kDa
protein in human epidermal, human conjunctiva, and tumor cell lysates
that was identified as β4-integrin by its reaction with polyclonal
and monoclonal antibodies to human β4-integrin. Sera from patients
with bullous pemphigoid, pemphigus vulgaris, and cicatricial
pemphigoid-like diseases did not recognize the 205-kDa protein,
indicating the specificity of the binding. These data strongly
implicate a role for human β4-integrin in the pathogenesis of OCP. It
should be emphasized that multiple antigens in the basement membrane
zone of squamous epithelia may serve as targets for a wide spectrum of
autoantibodies observed in vesiculobullous diseases. Molecular
definition of these autoantigens will facilitate the classification and
characterization of subsets of cicatricial pemphigoid and help
distinguishing them from bullous pemphigoid. This study highlights the
function and importance of β4-integrin in maintaining the attachment
of epithelial cells to the basement membrane.
Dramatically decreased high density lipoprotein cholesterol, increased remnant clearance, and insulin hypersensitivity in apolipoprotein A-II knockout mice suggest a complex role for apolipoprotein A-II in atherosclerosis susceptibility
Authors: Weng Wei , Breslow Jan L.
Published: July 2002

Apolipoprotein (apo) A-II is the second most abundant
apolipoprotein in high density lipoprotein (HDL). To study its role in
lipoprotein metabolism and atherosclerosis susceptibility, apo A-II
knockout mice were created. Homozygous knockout mice had 67% and 52%
reductions in HDL cholesterol levels in the fasted and fed states,
respectively, and HDL particle size was reduced. Metabolic turnover
studies revealed the HDL decrease to be due to both decreased HDL
cholesterol ester and apo A-I transport rate and increased HDL
cholesterol ester and apo A-I fractional catabolic rate. The apo A-II
deficiency trait was bred onto the atherosclerosis-prone apo
E-deficient background, which resulted in a surprising 66% decrease in
cholesterol levels due primarily to decreased atherogenic lipoprotein
remnant particles. Metabolic turnover studies indicated increased
remnant clearance in the absence of apo A-II. Finally, apo A-II
deficiency was associated with lower free fatty acid, glucose, and
insulin levels, suggesting an insulin hypersensitivity state. In
summary, apo A-II plays a complex role in lipoprotein metabolism, with
some antiatherogenic properties such as the maintenance of a stable HDL
pool, and other proatherogenic properties such as decreasing clearance
of atherogenic lipoprotein remnants and promotion of insulin
resistance.
Similar DNA recognition properties of alternatively spliced
Drosophila
POU factors
Authors: Turner Eric E.
Published: July 2002

The POU-IV or “Brn-3” class of POU-domain transcription
factors is represented in
Drosophila
by I-POU and
twin-of-I-POU, alternative splice products of the I-POU gene. I-POU has
been previously reported to inhibit DNA binding by the POU-III class
factor drifter/Cf1a via the formation of heterodimeric complexes.
Here we report that expression of the I-POU/tI-POU message is maximal
late in the embryonic phase of
Drosophila
development,
and I-POU is the preferred splice variant. Although I-POU lacks two
basic amino acid residues in the POU-homeodomain found in tI-POU and
Brn-3.0, these three POU-IV class proteins exhibit very similar
DNA-binding specificity. In contrast to previously published reports,
the results presented here show no effect of I-POU on DNA binding by
drifter, and no evidence for I-POU/drifter dimerization. These
results suggest that the I-POU/tI-POU gene products function by
transcriptional mechanisms similar to those of the homologous POU-IV
class factors expressed in other species, not by a unique inhibitory
mechanism.
Homocysteine induces congenital defects of the heart and neural tube: Effect of folic acid
Authors: Rosenquist Thomas H. , Ratashak S. Anne , Selhub Jacob
Published: July 2002

The biological basis or mechanism whereby folate supplementation
protects against heart and neural tube defects is unknown. It has been
hypothesized that the amino acid homocysteine may be the teratogenic
agent, since serum homocysteine increases in folate depletion; however,
this hypothesis has not been tested. In this study, avian embryos were
treated directly with
d
,
l
-homocysteine or with
l
-homocysteine thiolactone, and a dose response was
established. Of embryos treated with 50 μl of the teratogenic dose
(200 mM
d
,
l
-homocysteine or 100 mM
l
-homocysteine thiolactone) on incubation days 0, 1, and 2
and harvested at 53 h (stage 14), 27% showed neural tube defects.
To determine the effect of the teratogenic dose on the process of heart
septation, embryos were treated during incubation days 2, 3, and 4;
then they were harvested at day 9 following the completion of
septation. Of surviving embryos, 23% showed ventricular septal
defects, and 11% showed neural tube defects. A high percentage of the
day 9 embryos also showed a ventral closure defect. The teratogenic
dose was shown to raise serum homocysteine to over 150 nmol/ml,
compared with a normal level of about 10 nmol/ml. Folate
supplementation kept the rise in serum homocysteine to ≈45 nmol/ml,
and prevented the teratogenic effect. These results support the
hypothesis that homocysteine
per se
causes
dysmorphogenesis of the heart and neural tube, as well as of the
ventral wall.
Myristate exchange on the Trypanosoma brucei variant surface glycoprotein.
Authors: Buxbaum L U , Milne K G , Werbovetz K A , Englund P T
Published: July 2002

The glycosyl-phosphatidylinositol (GPI) anchor of the Trypanosoma brucei variant surface glycoprotein (VSG) is unique in having exclusively myristate as its fatty acid component. We previously demonstrated that the myristate specificity is the result of two independent pathways. First, the newly synthesized free GPI, which is not myristoylated, undergoes fatty acid remodeling to replace both its fatty acids with myristate. Second, the myristoylated precursor, glycolipid A, undergoes a myristate exchange reaction, detected by the replacement of unlabeled myristate by [3H]myristate. Remodeling and exchange have different enzymatic properties and apparently occur in different subcellular compartments. We now demonstrate that the GPI anchor linked to VSG is the major substrate for myristate exchange. VSG can be efficiently labeled with [3H]myristate by exchange in the presence of cycloheximide, an inhibitor that prevents new VSG synthesis and thus anchor addition to protein. Not only is newly synthesized VSG subject to exchange, but mature VSG, possibly recycling from the cell surface, also undergoes myristate exchange.
Substance P responsiveness of smooth muscle cells is regulated by the integrin ligand, thrombospondin.
Authors: Dahm L M , Bowers C W
Published: July 2002

The extracellular factors that determine a cell's responsiveness to neurotransmitters are of particular relevance for pharmacologically diverse cell types such as neurons and smooth muscle. We previously demonstrated that matrix-associated factors are capable of dramatically and specifically suppressing the responsiveness of smooth muscle to the neuropeptide, substance P. We now demonstrate that this influence of extracellular matrix on the pharmacological phenotype of smooth muscle cells can be blocked specifically by an Arg-Gly-Asp (RGD)-containing antagonist of integrins. Of a battery of integrin ligands tested, only thrombospondin mimicked the effect of the extracellular matrix on substance P responsiveness. This effect of thrombospondin was dose dependent, RGD sensitive, and blocked by an antibody directed against the RGD-containing region of thrombospondin. Because the mRNA for thrombospondin is present in the cells of the chicken amnion, this extracellular factor may normally suppress substance P responsiveness in amniotic smooth muscle. The results suggest a role for matrix-associated integrin ligands in the regulation of cellular responses to specific neurotransmitters and hormones and in the development and maintenance of tissue-specific pharmacological properties.
The catalytic mechanism of beta-lactamases: NMR titration of an active-site lysine residue of the TEM-1 enzyme.
Authors: Damblon C , Raquet X , Lian L Y , Lamotte-Brasseur J , Fonze E , Charlier P , Roberts G C , Frère J M
Published: July 2002

Beta-Lactamases are widespread in the bacterial world, where they are responsible for resistance to penicillins, cephalosporins, and related compounds, currently the most widely used antibacterial agents. Detailed structural and mechanistic understanding of these enzymes can be expected to guide the design of new antibacterial compounds resistant to their action. A number of high-resolution structures are available for class A beta-lactamases, whose catalytic mechanism involves the acylation of a serine residue at the active site. The identity of the general base which participates in the activation of this serine residue during catalysis has been the subject of controversy, both a lysine residue and a glutamic acid residue having been proposed as candidates for this role. We have used the pH dependence of chemical modification of epsilon-amino groups by 2,4,6,-trinitrobenzenesulfonate and the pH dependence of the epsilon-methylene 1H and 13C chemical shifts (in enzyme selectively labeled with [epsilon-13C]lysine) to estimate the pKa of the relevant lysine residue, lysine-73, of TEM-1 beta-lactamase. Both methods show that the pKa of this residue is > 10, making it very unlikely that this residue could act as a proton acceptor in catalysis. An alternative mechanism in which this role is performed by glutamate-166 through an intervening water molecule is described.
Numerical vorticity creation based on impulse conservation.
Authors: Summers D M , Chorin A J
Published: July 2002

The problem of creating solenoidal vortex elements to satisfy no-slip boundary conditions in Lagrangian numerical vortex methods is solved through the use of impulse elements at walls and their subsequent conversion to vortex loops. The algorithm is not uniquely defined, due to the gauge freedom in the definition of impulse; the numerically optimal choice of gauge remains to be determined. Two different choices are discussed, and an application to flow past a sphere is sketched.
A set of genes expressed in response to light in the adult cerebral cortex and regulated during development.
Authors: Nedivi E , Fieldust S , Theill L E , Hevron D
Published: July 2002

Activity-dependent plasticity is thought to underlie both formation of appropriate synaptic connections during development and reorganization of adult cortical topography. We have recently cloned many candidate plasticity-related genes (CPGs) induced by glutamate-receptor activation in the hippocampus. Screening the CPG pool for genes that may contribute to neocortical plasticity resulted in the identification of six genes that are induced in adult visual cortical areas in response to light. These genes are also naturally induced during postnatal cortical development. CPG induction by visual stimulation occurs primarily in neurons located in cortical layers II-III and VI and persists for at least 48 hr. Four of the visually responsive CPGs (cpg2, cpg15, cpg22, cpg29) are previously unreported genes, one of which (cpg2) predicts a "mini-dystrophin-like" structural protein. These results lend molecular genetic support to physiological and anatomical studies showing activity-dependent structural reorganization in adult cortex. In addition, these results provide candidate genes the function of which may underlie mechanisms of adult cortical reorganization.
The contagion indicator hypothesis for parasite-mediated sexual selection.
Authors: Able D J
Published: July 2002

Hamilton and Zuk [Hamilton, W. D. & Zuk, M. (1982) Science 218, 384-387] proposed that females choosing mates based on the degree of expression of male characters obtain heritable parasite resistance for their offspring. Alternatively, the "contagion indicator" hypothesis posits that females choose mates based on the degree of expression of male characters because the latter indicate a male's degree of infestation of parasites and thus the risk that choosing females and their offspring will acquire these parasites. I examined whether parasite transmittability affects the probability that parasite intensity and male mating success are negatively correlated in intraspecific studies of parasite-mediated sexual selection. When females risk infection of themselves or their future offspring as a result of mating with a parasitized male, negative relationships between parasite intensity and male mating success are significantly more likely to occur than when females do not risk such infection. The direct benefit to females of avoiding parasitic infection is proposed to lead to the linkage between variable secondary sexual characters and the intensity of transmittable parasites. The direct benefits of avoiding associatively transmittable parasites should be considered in future studies of parasite-mediated sexual selection.
Chronic estrogen-induced cervical and vaginal squamous carcinogenesis in human papillomavirus type 16 transgenic mice.
Authors: Arbeit J M , Howley P M , Hanahan D
Published: July 2002

High-risk human papillomaviruses (HPVs), including type 16, have been identified as factors in cervical carcinogenesis. However, the presence and expression of the virus per se appear to be insufficient for carcinogenesis. Rather, cofactors most likely are necessary in addition to viral gene expression to initiate neoplasia. One candidate cofactor is prolonged exposure to sex hormones. To examine the possible effects of estrogen on HPV-associated neoplasia, we treated transgenic mice expressing the oncogenes of HPV16 under control of the human keratin-14 promoter (K14-HPV16 transgenic mice) and nontransgenic control mice with slow release pellets of 17beta-estradiol. Squamous carcinomas developed in a multistage pathway exclusively in the vagina and cervix of K14-HPV16 transgenic mice. Estrogen-induced carcinogenesis was accompanied by an incremental increase in the incidence and distribution of proliferating cells solely within the cervical and vaginal squamous epithelium of K14-HPV16 mice. Expression of the HPV transgenes in untreated transgenic mice was detectable only during estrus; estrogen treatment resulted in transgene expression that was persistent but not further upregulated, remaining at low levels at all stages of carcinogenesis. The data demonstrate a novel mechanism of synergistic cooperation between chronic estrogen exposure and the oncogenes of HPV16 that coordinates squamous carcinogenesis in the female reproductive tract of K14-HPV16 transgenic mice.
A high-resolution physical map of human chromosome 11.
Authors: Qin S , Nowak N J , Zhang J , Sait S N , Mayers P G , Higgins M J , Cheng Y , Li L , Munroe D J , Gerhard D S , Weber B H , Bric E , Housman D E , Evans G A , Shows T B
Published: July 2002

The development of a highly reliable physical map with landmark sites spaced an average of 100 kbp apart has been a central goal of the Human Genome Project. We have approached the physical mapping of human chromosome 11 with this goal as a primary target. We have focused on strategies that would utilize yeast artificial chromosome (YAC) technology, thus permitting long-range coverage of hundreds of kilobases of genomic DNA, yet we sought to minimize the ambiguities inherent in the use of this technology, particularly the occurrence of chimeric genomic DNA clones. This was achieved through the development of a chromosome 11-specific YAC library from a human somatic cell hybrid line that has retained chromosome 11 as its sole human component.To maximize the efficiency of YAC contig assembly and extension, we have employed an Alu-PCR-based hybridization screening system. This system eliminates many of the more costly and time-consuming steps associated with sequence tagged site content mapping such as sequencing, primer production, and hierarchical screening, resulting in greater efficiency with increased throughput and reduced cost. Using these approaches, we have achieved YAC coverage for >90% of human chromosome 11, with an average intermarker distance of <100 kbp. Cytogenetic localization has been determined for each contig by fluorescent in situ hybridization and/or sequence tagged site content. The YAC contigs that we have generated should provide a robust framework to move forward to sequence-ready templates for the sequencing efforts of the Human Genome Project as well as more focused positional cloning on chromosome 11.
Transgenic mice carrying a human mutant superoxide dismutase transgene develop neuronal cytoskeletal pathology resembling human amyotrophic lateral sclerosis lesions.
Authors: Tu P H , Raju P , Robinson K A , Gurney M E , Trojanowski J Q , Lee V M
Published: July 2002

Mutations in the human Cu,Zn superoxide dismutase gene (SOD1) are found in 20% of kindreds with familial amyotrophic lateral sclerosis. Transgenic mice (line G1H) expressing a human SOD1 containing a mutation of Gly-93 --> Ala (G93A) develop a motor neuron disease similar to familial amyotrophic lateral sclerosis, but transgenic mice (line N1029) expressing a wild-type human SOD1 transgene do not. Because neurofilament (NF)-rich inclusions in spinal motor neurons are characteristic of amyotrophic lateral sclerosis, we asked whether mutant G1H and/or N1029 mice develop similar NF lesions. NF inclusions (i.e., spheroids, Lewy body-like inclusions) were first detected in spinal cord motor neurons of the G1H mice at 82 days of age about the time these mice first showed clinical evidence of disease. Other neuronal intermediate filament proteins (alpha-internexin, peripherin) also accumulated in these spheroids. The onset of accumulations of ubiquitin immunoreactivity in the G1H mice paralleled the emergence of vacuoles and NF-rich spheroids in neurons, but they did not colocalize exclusively with spheroids. In contrast, NF inclusions were not seen in the N1029 mice until they were 132 days old, and ubiquitin immunoreactivity was not increased in the N1029 mice even at 199 days of age. Astrocytosis in spinal cord was associated with a marked increase in glial fibrillary acidic protein immunoreactivity in the G1H mice, but not in the N1029 mice. Finally, comparative studies revealed a striking similarity between the cytoskeletal pathology in the G1H transgenic mice and in patients with amyotrophic lateral sclerosis. These findings link a specific SOD1 mutation with alterations in the neuronal cytoskeleton of patients with amyotrophic lateral sclerosis. Thus, neuronal cytoskeletal abnormalities may be implicated in the pathogenesis of human familial amyotrophic lateral sclerosis.
Targeted gene disruption of Hsp70-2 results in failed meiosis, germ cell apoptosis, and male infertility.
Authors: Dix D J , Allen J W , Collins B W , Mori C , Nakamura N , Poorman-Allen P , Goulding E H , Eddy E M
Published: July 2002

In addition to the five 70-kDa heat shock proteins (HSP70) common to germ cells and somatic tissues of mammals, spermatogenic cells synthesize HSP70-2 during meiosis. To determine if this unique stress protein has a critical role in meiosis, we used gene-targeting techniques to disrupt Hsp70-2 in mice. Male mice homozygous for the mutant allele (Hsp70-2 -/-) did not synthesize HSP70-2, lacked postmeiotic spermatids and mature sperm, and were infertile. However, neither meiosis nor fertility was affected in female Hsp70-2 -/- mice. We previously found that HSP70-2 is associated with synaptonemal complexes in the nucleus of meiotic spermatocytes from mice and hamsters. While synaptonemal complexes assembled in Hsp70-2 -/- spermatocytes, structural abnormalities became apparent in these cells by late prophase, and development rarely progressed to the meiotic divisions. Furthermore, analysis of nuclei and genomic DNA indicated that the failure of meiosis in Hsp70-2 -/- mice was coincident with a dramatic increase in spermatocyte apoptosis. These results suggest that HSP70-2 participates in synaptonemal complex function during meiosis in male germ cells and is linked to mechanisms that inhibit apoptosis.
Metalloelastase is required for macrophage-mediated proteolysis and matrix invasion in mice.
Authors: Shipley J M , Wesselschmidt R L , Kobayashi D K , Ley T J , Shapiro S D
Published: July 2002

Macrophages secrete a variety of proteinases that are thought to participate in remodeling of the extracellular matrix associated with inflammatory processes. We have eliminated expression of the macrophage metalloelastase (MME) gene by targeted disruption to assess the role of this protein in macrophage-mediated proteolysis. We found that the macrophages of MME-deficient (MME-/-) mice have a markedly diminished capacity to degrade extracellular matrix components. In addition, MME-/- macrophages are essentially unable to penetrate reconstituted basement membranes in vitro and in vivo. MME is therefore required for macrophage-mediated extracellular matrix proteolysis and tissue invasion.
Increased cytosine DNA-methyltransferase activity is target-cell-specific and an early event in lung cancer.
Authors: Belinsky S A , Nikula K J , Baylin S B , Issa J P
Published: July 2002

The association between increased DNA-methyltransferase (DNA-MTase) activity and tumor development suggest a fundamental role for this enzyme in the initiation and progression of cancer. A true functional role for DNA-MTase in the neoplastic process would be further substantiated if the target cells affected by the initiating carcinogen exhibit changes in enzyme activity. This hypothesis was addressed by examining DNA-MTase activity in alveolar type II (target) and Clara (nontarget) cells from A/J and C3H mice that exhibit high and low susceptibility, respectively, for lung tumor formation. Increased DNA-MTase activity was found only in the target alveolar type II cells of the susceptible A/J mouse and caused a marked increase in overall DNA methylation in these cells. Both DNA-MTase and DNA methylation changes were detected 7 days after carcinogen exposure and, thus, were early events in neoplastic evolution. Increased gene expression was also detected by RNA in situ hybridization in hypertrophic alveolar type II cells of carcinogen-treated A/J mice, indicating that elevated levels of expression may be a biomarker for premalignancy. Enzyme activity increased incrementally during lung cancer progression and coincided with increased expression of the DNA-MTase activity are strongly associated with neoplastic development and constitute a key step in carcinogenesis. The detection of premalignant lung disease through increased DNA-MTase expression and the possibility of blocking the deleterious effects of this change with specific inhibitors will offer new intervention strategies for lung cancer.
Population regulation in snowshoe hare and Canadian lynx: Asymmetric food web configurations between hare and lynx
Authors: Stenseth Nils Chr. , Falck Wilhelm , Bjørnstad Ottar N. , Krebs Charles J.
Published: July 2002

The snowshoe hare and the Canadian lynx in the boreal forests of North America show 9- to 11-year density cycles. These are generally assumed to be linked to each other because lynx are specialist predators on hares. Based on time series data for hare and lynx, we show that the dominant dimensional structure of the hare series appears to be three whereas that of the lynx is two. The three-dimensional structure of the hare time series is hypothesized to be due to a three-trophic level model in which the hare may be seen as simultaneously regulated from below and above. The plant species in the hare diet appear compensatory to one another, and the predator species may, likewise, be seen as an internally compensatory guild. The lynx time series are, in contrast, consistent with a model of donor control in which their populations are regulated from below by prey availability. Thus our analysis suggests that the classic view of a symmetric hare–lynx interaction is too simplistic. Specifically, we argue that the classic food chain structure is inappropriate: the hare is influenced by many predators other than the lynx, and the lynx is primarily influenced by the snowshoe hare.
High-affinity binding of bioactive glycosylation-inhibiting factor to antigen-primed T cells and natural killer cells
Authors: Sugie Katsuji , Nakano Tatsumi , Tomura Takafumi , Takakura Kenji , Mikayama Toshifumi , Ishizaka Kimishige
Published: July 2002

High-affinity binding was demonstrated between suppressor-T-cell-derived bioactive glycosylation-inhibiting factor (GIF) and helper T hybridomas and natural killer cell line cells. Inactive GIF present in cytosol of suppressor T cells andEscherichia coli-derived recombinant human GIF (rhGIF) failed to bind to these cells. However, affinity of rhGIF for the target cells was generated by replacement of Cys-57 in the sequence with Ala or of Asn-106 with Ser or binding of 5-thio-2-nitrobenzoic acid to Cys-60 in the molecule. Such mutations and the chemical modification of rhGIF synergistically increased the affinity of GIF molecules for the target cells. The results indicated that receptors on the target cells recognize conformational structures of bioactive GIF. Equilibrium dissociation constant (Kd) of the specific binding between bioactive rGIF derivatives and high-affinity receptors was 10–100 pM. Receptors for bioactive GIF derivatives were detected on Th1 and Th2 T helper clones and natural killer NK1.1+cells in normal spleen but not on naive T or B cells. Neither the inactive rGIF nor bioactive rGIF derivatives bound to macrophage and monocyte lines or induced macrophages for tumor necrosis factor α production.
Isotopes, ice ages, and terminal Proterozoic earth history
Authors: Kaufman Alan J. , Knoll Andrew H. , Narbonne Guy M.
Published: July 2002

Detailed correlations of ancient glacial deposits, based on temporal records of carbon and strontium isotopes in seawater, indicate four (and perhaps five) discrete ice ages in the terminal Proterozoic Eon. The close and repeated stratigraphic relationship between C-isotopic excursions and glaciogenic rocks suggests that unusually high rates of organic carbon burial facilitated glaciation by reducing atmospheric greenhouse capacity. The emerging framework of time and environmental change contributes to the improved resolution of stratigraphic and evolutionary pattern in the early fossil record of animals.
Polycaps: Reversibly formed polymeric capsules
Authors: Castellano Ronald K. , Rudkevich Dmitry M. , Rebek Julius
Published: July 2002

Described are assemblies consisting of polymeric capsules, “polycaps,” formed from two calix[4]arene tetraureas covalently connected at their lower rims. In these structures self-assembly leads to reversibly formed capsule sites along a chain, reminiscent of beads on a string. Their dynamic behavior is characterized by
1
H NMR spectroscopy through encapsulation of guest species, reversible polymerization, and the formation of sharply defined hybrid capsules.
Ethanolamine modulates the rate of rat hepatocyte proliferationin vitroandin vivo
Authors: Sasaki Hajime , Kume Hisae , Nemoto Atushi , Narisawa Sonoko , Takahashi Naommy
Published: July 2002

A low molecular weight, heat-resistant hepatotrophic factor in an extract from the bovine intestinal mucosa was purified and identified as ethanolamine by structural analyses. The mode of action of ethanolaminein vitroandin vivocoincided with that of the crude extract of the tissue, indicating that ethanolamine is the active component. Ethanolamine synergistically elevated the stimulation of DNA synthesis in hepatocytes in primary culture when added together with a growth factor, such as epidermal growth factor, with the ED50being 20 μM, although it showed little stimulatory effect by itself. Contrary to thesein vitroresults, the intraperitoneal administration of ethanolamine hydrochloride (24 mg of ethanolamine per kg of body weight) enhanced hepatocyte proliferation in regenerating rat livers after two-thirds hepatectomy without the administration of any growth factors. In the regenerating liver, hepatocyte proliferation may be initiated by an endogenous growth factor, but the supply of ethanolamine in circulation may not be sufficient for optimal hepatocyte proliferation; thus, the exogenous administration of ethanolamine may further enhance hepatocyte proliferation. Ethanolamine in circulation may be a humoral hepatotrophic factor.
Transposable elements as sources of variation in animals and plants
Authors: Kidwell Margaret G. , Lisch Damon
Published: July 2002

A tremendous wealth of data is accumulating on the variety and distribution of transposable elements (TEs) in natural populations. There is little doubt that TEs provide new genetic variation on a scale, and with a degree of sophistication, previously unimagined. There are many examples of mutations and other types of genetic variation associated with the activity of mobile elements. Mutant phenotypes range from subtle changes in tissue specificity to dramatic alterations in the development and organization of tissues and organs. Such changes can occur because of insertions in coding regions, but the more sophisticated TE-mediated changes are more often the result of insertions into 5′ flanking regions and introns. Here, TE-induced variation is viewed from three evolutionary perspectives that are not mutually exclusive. First, variation resulting from the intrinsic parasitic nature of TE activity is examined. Second, we describe possible coadaptations between elements and their hosts that appear to have evolved because of selection to reduce the deleterious effects of new insertions on host fitness. Finally, some possible cases are explored in which the capacity of TEs to generate variation has been exploited by their hosts. The number of well documented cases in which element sequences appear to confer useful traits on the host, although small, is growing rapidly.
The
Bacillus subtilis crh
gene encodes a HPr-like protein involved in carbon catabolite repression
Authors: Galinier Anne , Haiech Jacques , Kilhoffer Marie-Claude , Jaquinod Michel , Stülke Jörg , Deutscher Josef , Martin-Verstraete Isabelle
Published: July 2002

Carbon catabolite repression (CCR) of several
Bacillus subtilis
catabolic genes is mediated by ATP-dependent phosphorylation of histidine-containing protein (HPr), a phosphocarrier protein of the phosphoenolpyruvate (PEP): sugar phosphotransferase system. In this study, we report the discovery of a new
B. subtilis
gene encoding a HPr-like protein, Crh (for catabolite repression HPr), composed of 85 amino acids. Crh exhibits 45% sequence identity with HPr, but the active site His-15 of HPr is replaced with a glutamine in Crh. Crh is therefore not phosphorylated by PEP and enzyme I, but is phosphorylated by ATP and the HPr kinase in the presence of fructose-1,6-bisphosphate. We determined Ser-46 as the site of phosphorylation in Crh by carrying out mass spectrometry with peptides obtained by tryptic digestion or CNBr cleavage. In a
B. subtilis ptsH1
mutant strain, synthesis of β-xylosidase, inositol dehydrogenase, and levanase was only partially relieved from CCR. Additional disruption of the
crh
gene caused almost complete relief from CCR. In a
ptsH1 crh1
mutant, producing HPr and Crh in which Ser-46 is replaced with a nonphosphorylatable alanyl residue, expression of β-xylosidase was also completely relieved from glucose repression. These results suggest that CCR of certain catabolic operons requires, in addition to CcpA, ATP-dependent phosphorylation of Crh, and HPr at Ser-46.
Increased B-lymphopoiesis by interleukin 7 induces bone loss in mice with intact ovarian function: Similarity to estrogen deficiency
Authors: Miyaura Chisato , Onoe Yoshiko , Inada Masaki , Maki Kazushige , Ikuta Koichi , Ito Masako , Suda Tatsuo
Published: July 2002

Estrogen deficiency caused by ovariectomy (OVX) results in a marked bone loss due to stimulated bone resorption by osteoclasts. During our investigations of the pathogenesis of bone loss in estrogen deficiency, we found that OVX selectively stimulates B-lymphopoiesis which results in marked accumulation of B220-positive pre-B cells in mouse bone marrow. To examine the possible correlation between stimulated B-lymphopoiesis and bone loss, 8-week-old female mice were treated with interleukin (IL) 7, which stimulates B-lymphopoiesis in bone marrow. We also examined bone mass in IL-7 receptor-knockout mice that exhibit marked suppression of B-lymphopoiesis in the bone marrow. The increased B-lymphopoiesis induced by IL-7 administration resulted in marked bone loss by stimulation of osteoclastic bone resorption in mice with intact ovarian function. The changes in both B-lymphopoiesis and bone mass in IL-7-treated female mice were similar to those in age-matched OVX mice. In contrast, the trabecular bone volume of the femur was greatly increased in both female and male IL-7 receptor-knockout mice when compared with the respective wild-type and heterozygous littermates. These results show that the perturbation of B-lymphopoiesis in the bone marrow is closely linked to the change in bone mass. We propose here that the increased B-lymphopoiesis due to estrogen deficiency is involved in the mechanism of stimulated bone resorption.
Wolbachia
, normally a symbiont of
Drosophila
, can be virulent, causing degeneration and early death
Authors: Min Kyung-Tai , Benzer Seymour
Published: July 2002

Wolbachia
, a maternally transmitted microorganism of the Rickettsial family, is known to cause cytoplasmic incompatibility, parthenogenesis, or feminization in various insect species. The bacterium–host relationship is usually symbiotic: incompatibility between infected males and uninfected females can enhance reproductive isolation and evolution, whereas the other mechanisms enhance progeny production. We have discovered a variant
Wolbachia
carried by
Drosophila melanogaster
in which this cozy relationship is abrogated. Although quiescent during the fly’s development, it begins massive proliferation in the adult, causing widespread degeneration of tissues, including brain, retina, and muscle, culminating in early death. Tetracycline treatment of carrier flies eliminates both the bacteria and the degeneration, restoring normal life-span. The 16s rDNA sequence is over 98% identical to
Wolbachia
known from other insects. Examination of laboratory strains of
D. melanogaster
commonly used in genetic experiments reveals that a large proportion actually carry
Wolbachia
in a nonvirulent form, which might affect their longevity and behavior.
RecA tests homology at both pairing and strand exchange
Authors: Bazemore L. Rochelle , Folta-Stogniew Ewa , Takahashi Masayuki , Radding Charles M.
Published: July 2002

RecA is a 38-kDa protein from
Escherichia coli
that polymerizes on single-stranded DNA, forming a nucleoprotein filament that pairs with homologous duplex DNA and carries out strand exchange
in vitro
. To observe the effects of mismatches on the kinetics of the RecA-catalyzed recombination reaction, we used assays based upon fluorescence energy transfer that can differentiate between the pairing and strand displacement phases. Oligonucleotide sequences that produced 2–14% mismatches in the heteroduplex product of strand exchange were tested, as well as completely homologous and heterologous sequences. The equilibrium constant for pairing decreased as the number of mismatches increased, which appeared to result from both a decrease in the rate of formation and an increase in the rate of dissociation of the intermediates. In addition, the rate of strand displacement decreased with increasing numbers of mismatches, roughly in proportion to the number of mismatches. The equilibrium constant for pairing and the rate constant for strand displacement both decreased 6-fold as the heterology increased to 14%. These results suggest that discrimination of homology from heterology occurs during both pairing and strand exchange.
Mechanical stretch induces vascular permeability factor in human mesangial cells: Mechanisms of signal transduction
Authors: Gruden Gabriella , Thomas Stephen , Burt Davina , Lane Stephen , Chusney Gary , Sacks Steven , Viberti GianCarlo
Published: July 2002

Hemodynamic abnormalities have been implicated in the pathogenesis of the increased glomerular permeability to protein of diabetic and other glomerulopathies. Vascular permeability factor (VPF) is one of the most powerful promoters of vascular permeability. We studied the effect of stretch on VPF production by human mesangial cells and the intracellular signaling pathways involved. The application of mechanical stretch (elongation 10%) for 6 h induced a 2.4-fold increase over control in the VPF mRNA level (
P
< 0.05). There was a corresponding 3-fold increase in VPF protein level by 12 h (
P
< 0.001), returning to the baseline by 24 h. Stretch-induced VPF secretion was partially prevented both by the protein kinase C (PKC) inhibitor H7 (50 μM: 72% inhibition,
P
< 0.05) and by pretreatment with phorbol ester (phorbol-12-myristate-13 acetate 10
−
7
M: 77% inhibition,
P
< 0.05). A variety of protein tyrosine kinase (PTK) inhibitors, genistein (20 μg/ml), herbimycin A (3.4 μM), and a specific pp60
src
peptide inhibitor (21 μM) also significantly reduced, but did not entirely prevent, stretch-induced VPF protein secretion (respectively 63%, 80%, and 75% inhibition;
P
< 0.05 for all). The combination of both PKC and PTK inhibition completely abolished the VPF response to mechanical stretch (100% inhibition,
P
< 0.05). Stretch induces VPF gene expression and protein secretion in human mesangial cells via PKC- and PTK-dependent mechanisms.
A total system approach to sustainable pest management
Authors: Lewis W. J. , van Lenteren J. C. , Phatak Sharad C. , Tumlinson J. H.
Published: July 2002

A fundamental shift to a total system approach for crop protection is urgently needed to resolve escalating economic and environmental consequences of combating agricultural pests. Pest management strategies have long been dominated by quests for “silver bullet” products to control pest outbreaks. However, managing undesired variables in ecosystems is similar to that for other systems, including the human body and social orders. Experience in these fields substantiates the fact that therapeutic interventions into any system are effective only for short term relief because these externalities are soon “neutralized” by countermoves within the system. Long term resolutions can be achieved only by restructuring and managing these systems in ways that maximize the array of “built-in” preventive strengths, with therapeutic tactics serving strictly as backups to these natural regulators. To date, we have failed to incorporate this basic principle into the mainstream of pest management science and continue to regress into a foot race with nature. In this report, we establish why a total system approach is essential as the guiding premise of pest management and provide arguments as to how earlier attempts for change and current mainstream initiatives generally fail to follow this principle. We then draw on emerging knowledge about multitrophic level interactions and other specific findings about management of ecosystems to propose a pivotal redirection of pest management strategies that would honor this principle and, thus, be sustainable. Finally, we discuss the potential immense benefits of such a central shift in pest management philosophy.
Attenuated
T
2
relaxation by mutual cancellation of dipole–dipole coupling and chemical shift anisotropy indicates an avenue to NMR structures of very large biological macromolecules in solution
Authors: Pervushin Konstantin , Riek Roland , Wider Gerhard , Wüthrich Kurt
Published: July 2002

Fast transverse relaxation of
1
H,
15
N, and
13
C by dipole-dipole coupling (DD) and chemical shift anisotropy (CSA) modulated by rotational molecular motions has a dominant impact on the size limit for biomacromolecular structures that can be studied by NMR spectroscopy in solution. Transverse relaxation-optimized spectroscopy (TROSY) is an approach for suppression of transverse relaxation in multidimensional NMR experiments, which is based on constructive use of interference between DD coupling and CSA. For example, a TROSY-type two-dimensional
1
H,
15
N-correlation experiment with a uniformly
15
N-labeled protein in a DNA complex of molecular mass 17 kDa at a
1
H frequency of 750 MHz showed that
15
N relaxation during
15
N chemical shift evolution and
1
H
N
relaxation during signal acquisition both are significantly reduced by mutual compensation of the DD and CSA interactions. The reduction of the linewidths when compared with a conventional two-dimensional
1
H,
15
N-correlation experiment was 60% and 40%, respectively, and the residual linewidths were 5 Hz for
15
N and 15 Hz for
1
H
N
at 4°C. Because the ratio of the DD and CSA relaxation rates is nearly independent of the molecular size, a similar percentagewise reduction of the overall transverse relaxation rates is expected for larger proteins. For a
15
N-labeled protein of 150 kDa at 750 MHz and 20°C one predicts residual linewidths of 10 Hz for
15
N and 45 Hz for
1
H
N
, and for the corresponding uniformly
15
N,
2
H-labeled protein the residual linewidths are predicted to be smaller than 5 Hz and 15 Hz, respectively. The TROSY principle should benefit a variety of multidimensional solution NMR experiments, especially with future use of yet somewhat higher polarizing magnetic fields than are presently available, and thus largely eliminate one of the key factors that limit work with larger molecules.
Growth suppression of glioma cells by PTEN requires a functional phosphatase catalytic domain
Authors: Furnari Frank B. , Lin Hong , Huang H.-J. Su , Cavenee Webster K.
Published: July 2002

Deletions of all or part of chromosome 10 are the most common genetic alterations in high-grade gliomas. The
PTEN
gene (also called
MMAC1
and
TEP1
) maps to chromosome region 10q23 and has been implicated as a target of alteration in gliomas and also in other cancers such as those of the breast, prostate, and kidney. Here we sought to provide a functional test of its candidacy as a growth suppressor in glioma cells. We used a combination of Northern blot analysis, protein truncation assays, and sequence analysis to determine the types and frequency of
PTEN
mutations in glioma cell lines so that we could define appropriate recipients to assess the growth suppressive function of
PTEN
by gene transfer. Introduction of wild-type
PTEN
into glioma cells containing endogenous mutant alleles caused growth suppression, but was without effect in cells containing endogenous wild-type
PTEN
. The ectopic expression of
PTEN
alleles, which carried mutations found in primary tumors and have been shown or are expected to inactivate its phosphatase activity, caused little growth suppression. These data strongly suggest that PTEN is a protein phosphatase that exhibits functional and specific growth-suppressing activity.
Identification of genes differentially expressed by nerve growth factor- and neurotrophin-3-dependent sensory neurons
Authors: Friedel Roland H. , Schnürch Harald , Stubbusch Jutta , Barde Yves-Alain
Published: July 2002

The neurotrophins nerve growth factor (NGF) and neurotrophin-3 (NT3) support the survival of subpopulations of primary sensory neurons with defined and distinct physiological characteristics. Only a few genes have been identified as being differentially expressed in these subpopulations, and not much is known about the nature of the molecules involved in the processing of sensory information in NGF-dependent nociceptive neurons or NT3-dependent proprioceptive neurons. We devised a simple dorsal root ganglion (DRG) explant culture system, allowing the selection of neuronal populations preferentially responsive to NGF or NT3. The reliability of this assay was first monitored by the differential expression of the NGF and NT3 receptors trkA and trkC, as well as that of neuropeptides and calcium-binding proteins. We then identified four differentially expressed sodium channels, two enriched in the NGF population and two others in the NT3 population. Finally, using an optimized RNA fingerprinting protocol, we identified 20 additional genes, all differentially expressed in DRG explants cultured with NGF or NT3. This approach thus allows the identification of large number of genes expressed in subpopulations of primary sensory neurons and opens the possibility of studying the molecular mechanisms of nociception and proprioception.
Base excision repair deficient mice lacking the Aag alkyladenine DNA glycosylase
Authors: Engelward Bevin P. , Weeda Geert , Wyatt Michael D. , Broekhof José L. M. , de Wit Jan , Donker Ingrid , Allan James M. , Gold Barry , Hoeijmakers Jan H. J. , Samson Leona D.
Published: July 2002

3-methyladenine (3MeA) DNA glycosylases remove 3MeAs from alkylated DNA to initiate the base excision repair pathway. Here we report the generation of mice deficient in the 3MeA DNA glycosylase encoded by the
Aag
(
Mpg
) gene. Alkyladenine DNA glycosylase turns out to be the major DNA glycosylase not only for the cytotoxic 3MeA DNA lesion, but also for the mutagenic 1,
N
6
-ethenoadenine (ɛA) and hypoxanthine lesions. Aag appears to be the only 3MeA and hypoxanthine DNA glycosylase in liver, testes, kidney, and lung, and the only ɛA DNA glycosylase in liver, testes, and kidney; another ɛA DNA glycosylase may be expressed in lung. Although alkyladenine DNA glycosylase has the capacity to remove 8-oxoguanine DNA lesions, it does not appear to be the major glycosylase for 8-oxoguanine repair. Fibroblasts derived from
Aag
−/− mice are alkylation sensitive, indicating that
Aag
−/− mice may be similarly sensitive.
Baculovirus inhibitors of apoptosis (IAPs) block activation of Sf-caspase-1
Authors: Seshagiri Somasekar , Miller Lois K.
Published: July 2002

We have investigated the ability of Sf-caspase-1 and two mammalian caspases, caspase-1 and caspase-3, to induce apoptosis in
Spodoptera frugiperda
Sf-21 insect cells. While the transient expression of the pro-Sf-caspase-1 did not induce apoptosis, expression of the pro-domain deleted form, p31, or coexpression of the two subunits of mature Sf-caspase-1, p19 and p12, induced apoptosis in Sf-21 cells. The behavior of Sf-caspase-1 resembled that of the closely related mammalian caspase, caspase-3, and contrasted with that of the mammalian caspase-1, the pro-form of which was active in inducing apoptosis in Sf-21 cells. The baculovirus caspase inhibitor P35 blocked apoptosis induced by active forms of all three caspases. In contrast, members of the baculovirus inhibitor of apoptosis (IAP) family failed to block active caspase-induced apoptosis. However, during viral infection, expression of OpIAP or CpIAP blocked the activation of pro-Sf-caspase-1 and the associated induction of apoptosis. Thus, the mechanism by which baculovirus IAPs inhibit apoptosis is distinct from the mechanism by which P35 blocks apoptosis and involves inhibition of the activation of pro-caspases like Sf-caspase-1.