bluuebunny/crossref_metadata_2025 huggingface dataset:
The gene for the neuropeptide gonadotropin-releasing hormone is expressed in the mammary gland of lactating rats.
Authors: Palmon A , Ben Aroya N , Tel-Or S , Burstein Y , Fridkin M , Koch Y
Published: May 2006

The high concentration of gonadotropin-releasing hormone (GnRH) in milk of several species implies that the mammary gland is either a site of synthesis for this neuropeptide or that it is efficiently concentrated from plasma by this organ. By PCR amplification of mammary gland cDNA, we have demonstrated expression of the mRNA for GnRH. The GnRH mRNA was present in the mammary gland of pregnant and lactating rats but not of virgin rats, implying that expression of the GnRH gene is activated during pregnancy, probably by prolactin. In contrast, actin mRNA was evident in all the preparations of mammary glands. Since GnRH is also known to be synthesized by the placenta, it is likely that the placenta and the mammary gland are complementary units by which the mother exercises control over the development and the metabolism of the infant during pregnancy as well as after parturition. In addition, GnRH synthesized by the mammary gland may also affect the mother by a paracrine and/or an endocrine mechanism.
Zero-shift tuning in geonium by variation of trapped charge.
Authors: Dehmelt H
Published: May 2006

Measuring the g factor, or gyromagnetic ratio of an individual electron or positron permanently confined in ultrahigh vacuum at liquid helium temperature, provides one of the few avenues for testing the currently accepted standard model that views these elementary particles, on the same level as the quarks, as point-like objects without internal structure. Our results, even though their error limits are the smallest ever attained, would still benefit by possibly two orders of magnitude if a shift, estimated at 4 parts in 10(12), caused by interaction of the cyclotron motion with standing electromagnetic waves in the trap cavity confining the electron could be eliminated. Reexamination of experimental data obtained in another connection suggests that it is practical to identify certain critical cyclotron frequency values for that the shift disappears by testing if the cyclotron frequency measured on a cloud of electrons does not vary with the number of electrons it contains. Clouds here must be kept very much smaller than the wavelength of the above standing waves.
Molecular interactions between interferon consensus sequence binding protein and members of the interferon regulatory factor family.
Authors: Bovolenta C , Driggers P H , Marks M S , Medin J A , Politis A D , Vogel S N , Levy D E , Sakaguchi K , Appella E , Coligan J E
Published: May 2006

Interferon (IFN) consensus sequence binding protein (ICSBP) is a transcription factor expressed mostly in the cells of the immune system. ICSBP belongs to the IFN regulatory factor (IRF) family, which also includes IRF-1, IRF-2, and the IFN-alpha-stimulated gene factor 3 gamma (ISGF3 gamma). We show here that ICSBP forms a complex with IRF-1 or IRF-2 both in vivo and in vitro and, in the presence or absence of the target DNA, with the IFN-stimulated response element (ISRE). Further, electrophoretic mobility shift assays show that this interaction greatly enhances the otherwise very low binding affinity of ICSBP to the ISRE. We show, on the other hand, that ICSBP inhibits binding of the IFN-alpha-stimulated gene factor 3 gamma to the ISRE. Through these interactions ICSBP is likely to exert complex modulatory functions in the regulation of IFN-stimulated genes.
Mice lacking alpha 1 (IX) collagen develop noninflammatory degenerative joint disease.
Authors: Fässler R , Schnegelsberg P N , Dausman J , Shinya T , Muragaki Y , McCarthy M T , Olsen B R , Jaenisch R
Published: May 2006

Type IX collagen is a nonfibrillar collagen composed of three gene products, alpha 1(IX), alpha 2(IX), and alpha 3(IX). Type IX molecules are localized on the surface of type II-containing fibrils and consist of two arms, a long arm that is crosslinked to type II collagen and a short arm that projects into the perifibrillar space. In hyaline cartilage, the alpha 1(IX) collagen transcript encodes a polypeptide with a large N-terminal globular domain (NC4), whereas in many other tissues an alternative transcript encodes an alpha 1(IX) chain with a truncated NC4 domain. It has been proposed that type IX molecules are involved in the interaction of fibrils with each other or with other components of the extracellular matrix. To test this hypothesis, we have generated a mouse strain lacking both isoforms of the alpha 1(IX) chain. Homozygous mutant mice are viable and show no detectable abnormalities at birth but develop a severe degenerative joint disease resembling human osteoarthritis.
Prostaglandin E2 elicits a morphological change in cultured orbital fibroblasts from patients with Graves ophthalmopathy.
Authors: Smith T J , Wang H S , Hogg M G , Henrikson R C , Keese C R , Giaever I
Published: May 2006

Fibroblasts derived from distinct anatomical regions appear to differ in regard to their behavior in culture. These differences may reflect functions of these cells in vivo that are tissue specific. Moreover, intrinsic differences in fibroblasts may underlie the site-specific connective tissue manifestations associated with systemic disease. We have demonstrated previously that orbital fibroblasts exhibit different cytokine response domains and protein synthetic programs when compared to those emanating from the skin. In the present communication, we demonstrate that prostaglandin E2 (PGE2) elicits in cultured human orbital fibroblasts from patients with Graves ophthalmopathy a rapid and dramatic change in cell morphology in vitro as assessed by phase-contrast and scanning electron microscopy. The central areas of the cells become elevated with respect to the plane of the substratum and are stellate, with long processes that touch neighboring cells. These changes occur within 6 hr of prostanoid addition to culture medium at an apparent concentration threshold of approximately 10 nM. Shape changes are accompanied by marked alterations in monolayer impedance as assessed by electric cell-substrate impedance sensing as described previously. Both morphologic and impedance changes elicited by PGE2 revert over 24 hr toward those found in untreated cells despite the continued presence of the prostanoid in the culture medium. In contrast, dermal fibroblasts fail to respond to PGE2. These observations define a previously unrecognized phenotypic attribute of orbital fibroblasts. Intrinsic differences in these cells may account for the anatomic site-selective vulnerability of the orbit in Graves ophthalmopathy. The culture system described here may be useful for studying the morphogenic actions of prostanoids.
Induction of calcium-dependent nitric oxide synthases by sex hormones.
Authors: Weiner C P , Lizasoain I , Baylis S A , Knowles R G , Charles I G , Moncada S
Published: May 2006

We have examined the effects of pregnancy and sex hormones on calcium-dependent and calcium-independent nitric oxide synthases (NOSs) in the guinea pig. Pregnancy (near term) caused a > 4-fold increase in the activity of calcium-dependent NOS in the uterine artery and at least a doubling in the heart, kidney, skeletal muscle, esophagus, and cerebellum. The increase in NOS activity in the cerebellum during pregnancy was inhibited by the estrogen-receptor antagonist tamoxifen. Treatment with estradiol (but not progesterone) also increased calcium-dependent NOS activity in the tissues examined from both females and males. Testosterone increased calcium-dependent NOS only in the cerebellum. No significant change in calcium-independent NOS activity was observed either during pregnancy or after the administration of any sex hormone. Both pregnancy and estradiol treatment increased the amount of mRNAs for NOS isozymes eNOS and nNOS in skeletal muscle, suggesting that the increases in NOS activity result from enzyme induction. Thus both eNOS and nNOS are subject to regulation by estrogen, an action that could explain some of the changes that occur during pregnancy and some gender differences in physiology and pathophysiology.
Epithelial differentiation of metanephric mesenchymal cells after stimulation with hepatocyte growth factor or embryonic spinal cord.
Authors: Karp S L , Ortiz-Arduan A , Li S , Neilson E G
Published: May 2006

Mammalian kidney emerges from metanephric mesenchyme following the insertion of a migrating ureteric bud. The pattern morphology of mesenchymal specialization during tubular segmentation is remarkably complex, and the relative contribution of pattern gradients from the microenvironment versus the instructive role of individual cells is not known. We have started to examine the differentiation of metanephric mesenchyme using cultures of metanephric ridge (MMR) cells from day 13.5 mouse embryos to investigate the conversion of mesenchyme toward kidney epithelium in vitro. One of our mesenchymal clones, MMR1, expresses little Pax2, uvomorulin, or cytokeratin but does express neural cell adhesion molecule, bc12, and desmin; these are properties consistent with an early stem cell. Coculture of MMR1 cells with embryonic spinal cord leads to the induction of a more differentiated cell phenotype characterized by decreased expression of neural cell adhesion molecule, the appearance of uvomorulin, and the emergence of cytokeratin, all consistent with an evolution toward epithelium. We were also able to detect the hepatocyte growth factor receptor c-met on MMR1 cells by indirect immunofluorescence. When MMR1 cells were stimulated with hepatocyte growth factor, neural cell adhesion molecule expression decreased and uvomorulin appeared. This effect of hepatocyte growth factor, as a single cytokine, may be important in the early assemblage of kidney, since we were able to detect mRNA transcripts encoding c-met from mouse embryo metanephric kidneys.
Pregnancy-related steroids are potential negative regulators of B lymphopoiesis.
Authors: Medina K L , Kincade P W
Published: May 2006

B lymphopoiesis is selectively suppressed in normal pregnant mice, suggesting that fluctuations in systemic hormone levels might influence local events within bone marrow. This has now been tested by sustained experimental elevation of sex steroids by hormone-containing pellet implants. We found that while numbers of total nucleated cells declined after treatment with estrone, beta-estradiol, or estriol, there was preferential suppression of B-lymphocyte lineage precursors. Progesterone pellets had no effect when used alone, but mice exposed to progesterone were sensitive to several-logarithm lower concentrations of estrogen. Changes in subpopulations of B-lymphocyte lineage cells with hormone pellets were similar to those previously recorded in pregnancy. B-lymphocyte lineage precursors in male and female mice were sensitive to these sex hormones. Acute treatment with single injections of water-soluble beta-estradiol allowed temporal effects on B-lineage cells to be documented. With this protocol, total numbers of nucleated cells and myeloid progenitor cells remained unchanged. Interleukin 7-responsive precursors dramatically declined within 1 day of injection, suggesting that estrogen influences that stage in the B-lymphocyte lineage. There was a subsequent sharp drop in small pre-B cells 4 days after this transient elevation in estrogen. These experiments demonstrate that B lymphopoiesis is sensitive to negative regulation by sex steroids. They extend findings made with pregnant animals and parallel previous studies of the thymus. Sex steroids might contribute to control of steady-state lymphopoiesis, and fluctuations in their levels could have implications for human disease.
Two distinct signaling pathways trigger the expression of inducible nitric oxide synthase in rat renal mesangial cells.
Authors: Kunz D , Mühl H , Walker G , Pfeilschifter J
Published: May 2006

The expression of nitric oxide synthase (NOS; EC 1.14.13.39) is induced in rat glomerular mesangial cells by exposure to the inflammatory cytokine interleukin 1 beta (IL-1 beta) or cAMP-elevating agents. Stimulation with IL-1 beta alone leads to an approximately 40-fold increase in NOS activity and nitrite synthesis, whereas the elevation of cAMP with forskolin, cholera toxin, salbutamol, or dibutyryl-cAMP for 24 h resulted in a 2- to 12-fold increase in NOS activity. Moreover, the combinations of IL-1 beta with each of the cAMP-elevating agents greatly enhanced NOS activity in a synergistic fashion. Northern-blot analysis demonstrated a single band of approximately 4.5 kb for the NOS mRNA in rat mesangial cells. IL-1 beta increased NOS mRNA levels in a dose- and time-dependent fashion with a peak of NOS mRNA at 24 h. Dibutyryl-cAMP also increased NOS mRNA levels in mesangial cells in a dose- and time-dependent manner. Furthermore, combination of IL-1 beta and forskolin revealed a strong synergy with maximal mRNA levels 12 h after stimulation. Nuclear run-on transcription experiments suggest that IL-1 beta and cAMP synergistically interact to increase NOS gene expression at the transcriptional level. Furthermore, message stability studies established that NOS mRNA induced by cAMP has a longer half-life than the IL-1 beta-induced message. Moreover, cAMP exposure markedly prolonged the half-life of NOS mRNA from 1 h to 3 h. These data suggest that the level of NOS mRNA is controlled by at least two different signaling pathways, one involving cAMP and the other being triggered by cytokines such as IL-1 beta. The two pathways act synergistically and thus potently up-regulate the expression of inducible NOS in rat mesangial cells.
Limb and lower-body duplications induced by retinoic acid in mice.
Authors: Rutledge J C , Shourbaji A G , Hughes L A , Polifka J E , Cruz Y P , Bishop J B , Generoso W M
Published: May 2006

The zygote and subsequent preimplantation stages of early mammalian development are susceptible to certain chemical perturbations that cause abnormal development of the conceptus. In certain cases, disruption in patterns of gene expression could be a primary event leading to abnormal development. To investigate this hypothesis, we treated pregnant mice with trans-retinoic acid, a known modulator of gene expression. Treatments were administered at various times during pregastrulation stages and the presumed onset of gastrulation. trans-Retinoic acid induced a distinctive set of malformations, as manifest by supernumerary and ectopic limbs and duplication of portions of the lower body, but only when administered during the period of 4.5-5.5 days after mating. (Other malformations were induced at different stages.) The limb and lower-body duplications suggest that exogenous trans-retinoic acid may influence not only the pattern for the hindlimbs but also that for the entire lower body. Since it appears likely that the embryos were affected in the late blastocyst and proamniotic-embryo stages, the provocative possibility arises that aspects of pattern formation of limbs and lower body actually occur prior to gastrulation.
Evidence that inactive p42 mitogen-activated protein kinase and inactive Rsk exist as a heterodimer in vivo.
Authors: Hsiao K M , Chou S Y , Shih S J , Ferrell J E
Published: May 2006

Mitogen-activated protein kinases (MAP kinases) are active only when phosphorylated. Here we examine whether the activation of Xenopus p42 MAP kinase might involve changes in its association with other proteins as well as changes in its phosphorylation state. We find that when p42 MAP kinase is phosphorylated and active, it is monomeric, and that when p42 MAP kinase is nonphosphorylated and inactive, about half of it is monomeric and half is a component of a 110-kDa complex. We identify Rsk, an 82-kDa protein kinase that can be phosphorylated and partially activated by p42 MAP kinase, as being specifically associated with inactive p42 MAP kinase. It is possible that the complex of inactive p42 MAP kinase and inactive Rsk acts as a single signal reception particle and that the activation of the two kinases may be better described as a fork in a bifurcating signal transduction pathway than as successive levels in a kinase cascade.
Alterations in major histocompatibility complex association of myocarditis induced by coxsackievirus B3 mutants selected with monoclonal antibodies to group A streptococci.
Authors: Huber S A , Moraska A , Cunningham M
Published: May 2006

Three monoclonal antibodies (mAbs), 49.8.9, 36.2.2, and 54.2.8, made to the group A streptococcus M5 serotype identify crossreactive epitopes in cardiac tissues and also neutralize a highly myocarditic variant of coxsackievirus B3 (H3). Mutants of H3 were selected with these mAbs and evaluated for pathogenicity compared with the wild-type virus. H3 and the mutant variants selected with mAbs 36.2.2 (H3-36) and 54.2.8 (H3-54) induced severe myocarditis in DBA/2 (H-2d) and A/J (H-2a) male mice, whereas CBA (H-2k) mice were disease resistant. The virus variant isolated with mAb 49.8.9 (H3-49) was strikingly different and caused disease in CBA and A/J mice but not in DBA/2 animals, suggesting that the major histocompatibility complex association of the disease had been altered. This hypothesis was confirmed by using B10 congenic mice. In addition, T lymphocytes from the H3 and H3-49 virus-infected mice responded to distinctly different peptides in the streptococcal M protein, suggesting that certain epitopes of infectious agents which are shared with host tissues may be critical in determining disease susceptibility in genetically distinct individuals.
Granulocyte/macrophage colony-stimulating factor-deficient mice show no major perturbation of hematopoiesis but develop a characteristic pulmonary pathology.
Authors: Stanley E , Lieschke G J , Grail D , Metcalf D , Hodgson G , Gall J A , Maher D W , Cebon J , Sinickas V , Dunn A R
Published: May 2006

Mice homozygous for a disrupted granulocyte/macrophage colony-stimulating factor (GM-CSF) gene develop normally and show no major perturbation of hematopoiesis up to 12 weeks of age. While most GM-CSF-deficient mice are superficially healthy and fertile, all develop abnormal lungs. There is extensive peribronchovascular infiltration with lymphocytes, predominantly B cells. Alveoli contain granular eosinophilic material and lamellar bodies, indicative of surfactant accumulation. There are numerous large intraalveolar phagocytic macrophages. Some mice have subclinical lung infections involving bacterial or fungal organisms, occasionally with focal areas of acute purulent inflammation or lobar pneumonia. Some features of this pathology resemble the human disorder alveolar proteinosis. These observations indicate that GM-CSF is not essential for the maintenance of normal levels of the major types of mature hematopoietic cells and their precursors in blood, marrow, and spleen. However, they implicate GM-CSF as essential for normal pulmonary physiology and resistance to local infection.
Cloning and expression of a cDNA encoding a brain-specific Na(+)-dependent inorganic phosphate cotransporter.
Authors: Ni B , Rosteck P R , Nadi N S , Paul S M
Published: May 2006

We have isolated a brain-specific cDNA that encodes a Na(+)-dependent inorganic phosphate (Pi) cotransporter (BNPI). The nucleotide sequence of BNPI predicts a protein of 560 amino acids with 6-8 putative transmembrane-spanning segments that is approximately 32% identical to the rabbit kidney Na(+)-dependent Pi cotransporter. Expression of BNPI mRNA in Xenopus oocytes results in Na(+)-dependent Pi transport similar to that reported for the recombinantly expressed or native kidney Na(+)-dependent cotransporter. RNA blot analysis reveals that BNPI mRNA is expressed predominantly (if not exclusively) in brain, and in situ hybridization histochemistry reveals BNPI transcripts in neurons of the cerebral cortex, hippocampus, and cerebellum. Furthermore, we have confirmed the presence of saturable Na(+)-dependent Pi cotransport in cultured cerebellar granule cells. Together, these data demonstrate the presence of a specific neuronal Na(+)-dependent transport system for Pi in brain.
Anti-peptidyl transferase leader peptides of attenuation-regulated chloramphenicol-resistance genes.
Authors: Gu Z , Harrod R , Rogers E J , Lovett P S
Published: May 2006

The chloramphenicol (Cm)-inducible cmlA gene of Tn1696 specifies nonenzymatic resistance to Cm and is regulated by attenuation. The first eight codons of the leader specify a peptide that inhibits peptidyl transferase in vitro. Functionally similar, but less inhibitory, peptides are encoded by the leaders of Cm-inducible cat genes. However, the cat and cmlA coding sequences are unrelated and specify proteins of unrelated function. The inhibition of peptidyl transferase by the leader peptides is additive with that of Cm. Erythromycin competes with the inhibitory action of the peptides, and erythromycin and the peptides footprint to overlapping sites at the peptidyl transferase center of 23S rRNA. It is proposed that translation of the cmlA and cat leaders transiently pauses upon synthesis of the inhibitor peptides. The predicted site of pausing is identical to the leader site where long-term occupancy by a ribosome (ribosome stalling) will activate downstream gene expression. We therefore propose the inducer, Cm, converts a peptide-paused ribosome to the stalled state. We discuss the idea that cooperativity between leader peptide and inducer is necessary for ribosome stalling and may link the activation of a specific drug-resistance gene with a particular antibiotic.
Differences in dorsal and ventral pigmentation result from regional expression of the mouse agouti gene.
Authors: Vrieling H , Duhl D M , Millar S E , Miller K A , Barsh G S
Published: May 2006

The agouti coat color gene encodes a paracrine signaling molecule that controls the production of yellow and black pigment by melanocytes within hair follicles. Some agouti alleles affect the dorsum and ventrum independently, which has provided the basis for speculation that agouti gene action in different regions of the body is controlled by distinct genetic loci that are closely linked. Using a combination of cDNA cloning and RNA expression studies, we find that alternative isoforms of agouti mRNA contain different noncoding first exons located 100 kb apart, whose patterns of expression indicate independent control by regulatory elements that are either ventral specific or hair cycle specific. These results demonstrate that the apparent genetic complexity of the agouti locus is explained by the existence of multiple regulatory elements exerting control over a single coding sequence and provide a conceptual basis for understanding differences in dorsal and ventral hair coloration in many mammalian species. The ventral-specific agouti isoform represents an example of a transcript whose expression is restricted to ventral skin and provide an approach to investigate the mechanisms by which dorsal-ventral differences in gene expression are established and maintained.
D1 dopamine receptor immunoreactivity in human and monkey cerebral cortex: predominant and extrasynaptic localization in dendritic spines.
Authors: Smiley J F , Levey A I , Ciliax B J , Goldman-Rakic P S
Published: May 2006

Antibodies to the D1 dopamine receptor were used to localize this protein in several areas of human and monkey cerebral cortex with light and electron microscopy. In addition to cell body labeling in monkeys, all areas of humans and monkeys had a neuropil label with a laminar distribution predicted by previous D1 receptor autoradiography studies. Using electron microscopy, this neuropil label was seen in numerous dendritic spines, in dendritic shafts, and in occasional axon terminals. While labeled spines were common, they represented only a subset of all cortical spines. Serial sectioning through labeled spines showed that the diaminobenzidine reaction product was usually not at postsynaptic densities but instead was displaced to the side of the large asymmetric (presumed glutamatergic) synapse. Furthermore, most labeled spines did not receive synapses with dopaminergic features, suggesting that many D1 receptors are at extrasynaptic sites, possibly receiving dopamine via diffusion in the neuropil. Similarly, double labeling failed to reveal D1 labeling at synapses of tyrosine hydroxylase immunoreactive axons. Localization to numerous dendritic spines suggests that a primary role of D1 receptors is modulation of glutamatergic input to cortical pyramidal cells.
Inhibition of human immunodeficiency virus type 1 integrase by 3'-azido-3'-deoxythymidylate.
Authors: Mazumder A , Cooney D , Agbaria R , Gupta M , Pommier Y
Published: May 2006

The effects of 3'-azido-3'-deoxythymidine (AZT) and three of its intracellular metabolites, azido- thymidine mono-, di-, and triphosphates, on the human immunodeficiency virus type 1 integrase have been determined. AZT mono-, di-, and triphosphate have an IC50 for integration between 110 and 150 microM, whereas AZT does not inhibit the integrase. The inhibition by AZT monophosphate can be partially reversed by coincubation with either thymidine monophosphate or 2',3'-dideoxythymidine monophosphate, suggesting that either of these monophosphates can bind to the integrase but that the azido group at the 3' position could be responsible for the inhibition. Integrase inhibition is associated with reduced enzyme-DNA binding but does not appear to be competitive with respect to the DNA substrate. Inhibition of an integrase deletion mutant containing only amino acids 50-212 suggests that these nucleotides bind in the catalytic core. Concentrations up to 1 mM AZT monophosphate can accumulate in vivo, indicating that integrase inhibition may contribute to the antiviral effects of AZT. The increasing incidence of AZT-resistant virus strains may, therefore, be associated with mutations not only in the reverse transcriptase but also in the human immunodeficiency virus integrase. Finally, these observations suggest that additional strategies for antiviral drug development could be based upon nucleotide analogs as inhibitors of human immunodeficiency virus integrase.
Optimal sequence selection in proteins of known structure by simulated evolution.
Authors: Hellinga H W , Richards F M
Published: May 2006

Rational design of protein structure requires the identification of optimal sequences to carry out a particular function within a given backbone structure. A general solution to this problem requires that a potential function describing the energy of the system as a function of its atomic coordinates be minimized simultaneously over all available sequences and their three-dimensional atomic configurations. Here we present a method that explicitly minimizes a semiempirical potential function simultaneously in these two spaces, using a simulated annealing approach. The method takes the fixed three-dimensional coordinates of a protein backbone and stochastically generates possible sequences through the introduction of random mutations. The corresponding three-dimensional coordinates are constructed for each sequence by "redecorating" the backbone coordinates of the original structure with the corresponding side chains. These are then allowed to vary in their structure by random rotations around free torsional angles to generate a stochastic walk in configurational space. We have named this method protein simulated evolution, because, in loose analogy with natural selection, it randomly selects for allowed solutions in the sequence of a protein subject to the "selective pressure" of a potential function. Energies predicted by this method for sequences of a small group of residues in the hydrophobic core of the phage lambda cI repressor correlate well with experimentally determined biological activities. This "genetic selection by computer" approach has potential applications in protein engineering, rational protein design, and structure-based drug discovery.
Comparison of directional selectivity in identified spiking and nonspiking mechanosensory neurons in the crayfish Orconectes limosus.
Authors: Tautz J , Plummer M R
Published: May 2006

We have recorded electrical activity from two identified synaptically coupled mechanosensory interneurons in the abdominal nervous system of the crayfish Orconectes limosus and have studied their responses to constant-velocity water-jet stimuli presented from different directions. The two neurons, the ascending caudal photoreceptor (CPR) and the local directionally selective neuron, responded preferentially to stimuli delivered ipsilaterally to their dendritic input regions. Both neurons featured responses consisting of a phasic excitatory "on" response and a tonic depolarizing plateau. The different response components showed various degrees of directional selectivity: The initial "on" peak of the response was the least sensitive and the plateau was the most sensitive to stimulus direction. The CPR showed a sharp cut-off in responsiveness to contralateral stimuli, whereas the local directionally selective neuron showed a more gradual decrease in its directional responsiveness. This difference is a consequence of the feed-forward lateral inhibition that the local directionally selective neuron exerts on the CPR and of the threshold for initiation of action potentials in the CPR. A comparison of the spiking response of the CPR with its generator potential shows that the number and frequency of action potentials are a more sensitive indicator of directional preference than the generator potential response. The directional characteristic of the CPR is discussed as a filter matched to a specific spatial aspect of biologically relevant water movements.
Excision of hypoxanthine from DNA containing dIMP residues by the Escherichia coli, yeast, rat, and human alkylpurine DNA glycosylases.
Authors: Saparbaev M , Laval J
Published: May 2006

The deamination of adenine residues in DNA generates hypoxanthine, which is mutagenic since it gives rise to an A.T to G.C transition. Hypoxanthine is removed by hypoxanthine DNA glycosylase activity present in Escherichia coli and mammalian cells. Using polydeoxyribonucleotides or double-stranded synthetic oligonucleotides that contain dIMP residues, we show that this activity in E. coli is associated with the 3-methyladenine DNA glycosylase II coded for by the alkA gene. This conclusion is based on the following facts: (i) the two enzymatic activities have the same chromatographic behavior on various supports and they have the same molecular weight, (ii) both are induced during the adaptive response, (iii) a multicopy plasmid bearing the alkA gene overproduces both activities, (iv) homogeneous preparation of AlkA has both enzymatic activities, (v) the E. coli alkA- mutant does not show any detectable hypoxanthine DNA glycosylase activity. Under the same experimental conditions, but using different substrates, the same amount of AlkA protein liberates 1 pmol of 3-methyladenine from alkylated DNA and 1.2 fmol of hypoxanthine from dIMP-containing DNA. The Km for the latter substrate is 420 x 10(-9) M as compared to 5 x 10(-9) M for alkylated DNA. Hypoxanthine is released as a free base during the reaction. Duplex oligodeoxynucleotides containing hypoxanthine positioned opposite T, G, C, and A were cleaved efficiently. ANPG protein, APDG protein, and MAG protein--the 3-methyladenine DNA glycosylases of human, rat, and yeast origin, respectively--were also able to release hypoxanthine from various DNA substrates containing dIMP residues. The mammalian enzyme is by far the most efficient hypoxanthine DNA glycosylase of all the enzymes tested.
Sequence-independent induction of Sp1 transcription factor activity by phosphorothioate oligodeoxynucleotides.
Authors: Perez J R , Li Y , Stein C A , Majumder S , van Oorschot A , Narayanan R
Published: May 2006

Modified analogues of antisense oligodeoxynucleotides (ODNs), particularly phosphorothioates ([S]ODNs), have been extensively used to inhibit gene expression. The potential sequence specificity of antisense oligomers makes them attractive as molecular drugs for human diseases. The use of antisense [S]ODNs to inhibit gene expression has been complicated by frequent nonspecific effects. In this study we show in diverse cell types that [S]ODNs, independent of their base sequence, mediated the induction of an Sp1 nuclear transcription factor. The [S]ODN-mediated Sp1 induction was rapid and was associated with elevated levels of Sp1 protein. This induction was dependent on NF-kappa B activity, since inhibition of NF-kappa B activity abolished the [S]ODN-induced Sp1 activity. [S]ODN-induced Sp1 activity was seen in mouse spleen cells following in vivo administration. Sp1 activity induced by [S]ODNs required the tyrosine kinase pathway and did not have transactivating potential. These results may help to explain some of the non-specific effects often seen with [S]ODNs.
New phenotype of mutations deficient in glucosylation of the lipid-linked oligosaccharide: cloning of the ALG8 locus.
Authors: Stagljar I , te Heesen S , Aebi M
Published: May 2006

Glc3Man9GlcNAc2 is the preferred substrate of the oligosaccharyltransferase of N-linked glycosylation of proteins, but nonglucosylated oligosaccharides can be transferred to proteins in Saccharomyces cerevisiae. Mutations affecting the addition of the three terminal glucose residues lead to accumulation of Man9GlcNAc2 or Glc1Man9GlcNAc2 in vivo but do not show any detectable growth defect. When these mutations were introduced into a strain with reduced oligosaccharyltransferase activity (due to the wbp1-1 mutation), a severe growth defect was observed: accumulation of suboptimal lipid-linked oligosaccharide and reduced oligosaccharyltransferase activity resulted in a severe underglycosylation of secreted proteins. This new synthetic phenotype made it possible to isolate the ALG8 locus, encoding a potential glucosyltransferase of the endoplasmic reticulum. The ALG8 protein is a 63.5-kDa hydrophobic protein that is not essential for the vegetative growth of yeast. However, the lack of this protein resulted in underglycosylation of secreted proteins.
Oncogenic Ras activates c-Jun via a separate pathway from the activation of extracellular signal-regulated kinases.
Authors: Westwick J K , Cox A D , Der C J , Cobb M H , Hibi M , Karin M , Brenner D A
Published: May 2006

c-Jun transcriptional activity is augmented by expression of oncogenic Ras and Raf proteins. This study demonstrates a direct correlation between Ras transforming activity and c-Jun activation, supporting an important role for c-Jun in transformation by Ras. Since we observed that Ras activated c-Jun transcriptional activity by increasing phosphorylation of the c-Jun activation domain at residues Ser-63/Ser-73 and that oncogenic Ras proteins activated extracellular signal-regulated protein kinases (ERK1 and ERK2) (also known as mitogen-activated protein kinases), we evaluated the possibility that ERKs were directly responsible for c-Jun activation. Coexpression of wild-type ERKs with oncogenic Ras proteins potentiated, while kinase-defective ERKs inhibited, Ras-induced transcriptional activation from the Ras-responsive element (Ets-1/AP-1) present in the NVL-3 enhancer and the serum-response element in the c-fos promoter. In contrast, coexpression of either wild-type or kinase-defective ERKs inhibited Ras and Raf activation of c-Jun transcriptional activity. Thus, although activation of both ERK and c-Jun are downstream consequences of activation of the Ras signal transduction pathway, our results suggest that Ras-induced c-Jun phosphorylation and transcriptional activation are not a direct consequence of ERK1 and ERK2 activation.
Dynamic reorientation of cortical microtubules, from transverse to longitudinal, in living plant cells.
Authors: Yuan M , Shaw P J , Warn R M , Lloyd C W
Published: May 2006

The direction in which plant tissue cells expand is reflected in the alignment of microtubules in the cortical array. When microtubules and coaligned wall microfibrils are arranged transversely around the cell, turgor pressure is chaneled into cell elongation. However, various agents (such as wounding, ethylene, abscisic acid) can cause the microtubules to reorientate by 90 degrees so that they become aligned parallel to the cell's long axis, allowing lateral expansion instead of elongation. The mechanism by which microtubules undergo rapid shifts of alignment is crucial to understanding growth control in plants, but because current models are derived from studies on fixed cells, nothing is known about the dynamics of converting one microtubule alignment to another. Cells tend to have one predominant microtubule alignment--transverse, oblique, or longitudinal--but it is not established whether each represents a stable independent set that only changes by rounds of complete de- and repolymerization, or whether reorientation is a more continuous process involving movement of stable or dynamic microtubules. By microinjecting pea (Pisum sativum) epidermal cells with rhodamine-conjugated brain tubulin and optically sectioning them by confocal laser scanning microscopy, we could follow labeled microtubules for up to 2 hr as they reorientate. Reorientation does not occur by complete depolymerization of microtubules in one orientation followed by polymerization of a new array in another orientation. Instead, increased numbers of discordant microtubules in nontransverse alignment appear in particular locations. Neighboring microtubules then adopt the new alignment, so that there is a stage during which different alignments coexist before the array on the outer tangential cell face finally adopts a uniform steeply oblique/longitudinal configuration. Rapid fluorescence recovery after photobleaching confirms that bundles of cortical microtubules are not stable but exhibit properties consistent with dynamic instability. Dynamic microtubules offer a mechanism for rapid growth responses to a range of physiological stimuli.
Frameshift mutations at two hotspots in vasopressin transcripts in post-mitotic neurons.
Authors: Evans D A , van der Kleij A A , Sonnemans M A , Burbach J P , van Leeuwen F W
Published: May 2006

Mutations in DNA underlie carcinogenesis, inherited pathology, and aging and are generally thought to be introduced during meiosis and mitosis. Here we report that in post-mitotic neurons specific frameshift mutations occur at high frequency. These mutations were identified in vasopressin transcripts in magnocellular neurons of the homozygous Brattleboro rat and predominantly consist of a GA deletion in GAGAG motifs. Immunocytochemistry provides evidence for similar events in wild-type rats. However, the diseased state of the Brattleboro rat, resulting in a permanent activation of vasopressin neurons, enhanced the mutational rate. These data reveal hitherto unrecognized somatic mutations in nondividing neurons.
Positive control mutations in the MyoD basic region fail to show cooperative DNA binding and transcriptional activation in vitro.
Authors: Bengal E , Flores O , Rangarajan P N , Chen A , Weintraub H , Verma I M
Published: May 2006

An in vitro transcription system from HeLa cells has been established in which MyoD and E47 proteins activate transcription both as homodimers and heterodimers. However, heterodimers activate transcription more efficiently than homodimers, and function synergistically from multiple binding sites. Positive control mutants in the basic region of MyoD that have previously been shown to be defective in initiating the myogenic program, can bind DNA but have lost their ability to function as transcriptional activators in vitro. Additionally, positive control mutants, unlike wild-type MyoD, fail to bind cooperatively to DNA. We propose that binding of MyoD complexes to high affinity MyoD binding sites induces conformational changes that facilitate cooperative binding to multiple sites and promote transcriptional activation.
Decay-accelerating factor (CD55), a glycosylphosphatidylinositol-anchored complement regulatory protein, is a receptor for several echoviruses.
Authors: Bergelson J M , Chan M , Solomon K R , St John N F , Lin H , Finberg R W
Published: May 2006

Echoviruses are human pathogens belonging to the picornavirus family. Decay-accelerating factor (DAF) is a glycosylphosphatidylinositol (GPI)-anchored surface protein that protects cells from lysis by autologous complement. Anti-DAF monoclonal antibodies prevented echovirus 7 attachment to susceptible cells and protected cells from infection. HeLa cells specifically lost the capacity to bind echovirus 7 when treated with phosphatidylinositol-specific phospholipase C, an enzyme that releases GPI-anchored proteins from the cell surface, indicating that the virus receptor, like DAF, is a GPI-anchored protein. Although Chinese hamster ovary cells do not bind echovirus 7, transfectants expressing human DAF bound virus efficiently, and binding was prevented by pretreatment with an anti-DAF monoclonal antibody. Anti-DAF antibodies prevented infection by at least six echovirus serotypes. These results indicate that DAF is the receptor mediating attachment and infection by several echoviruses.
Molecular cloning and expression of a member of the aquaporin family with permeability to glycerol and urea in addition to water expressed at the basolateral membrane of kidney collecting duct cells.
Authors: Ishibashi K , Sasaki S , Fushimi K , Uchida S , Kuwahara M , Saito H , Furukawa T , Nakajima K , Yamaguchi Y , Gojobori T
Published: May 2006

Water transport in highly water-permeable membranes is conducted by water-selective pores--namely, water channels. The recent cloning of water channels revealed the water-selective characteristics of these proteins when expressed in Xenopus oocytes or reconstituted in liposomes. Currently, it is assumed that the function of water channels is to transport only water. We now report the cloning of a member of the water channel that also transports nonionic small molecules such as urea and glycerol. We named this channel aquaporin 3 (AQP3) for its predominant water permeability. AQP3 has amino acid sequence identity with major intrinsic protein (MIP) family proteins including AQP-channel-forming integral membrane protein, AQP-collecting duct, MIP, AQP-gamma tonoplast intrinsic protein, nodulin 26, and glycerol facilitator (33-42%). Thus, AQP3 is an additional member of the MIP family. Osmotic water permeability of Xenopus oocytes measured by videomicroscopy was 10-fold higher in oocytes injected with AQP3 transcript than with water-injected oocytes. The increase in osmotic water permeability was inhibited by HgCl2, and this effect was reversed by a reducing agent, 2-mercaptoethanol. Although to a smaller degree, AQP3 also facilitated the transport of nonionic small solutes such as urea and glycerol, while the previously cloned water channels are permeable only to water when expressed in Xenopus oocytes. AQP3 mRNA was expressed abundantly in kidney medulla and colon. In kidney, it was exclusively immunolocalized at the basolateral membrane of collecting duct cells. AQP3 may function as a water and urea exit mechanism in antidiuresis in collecting duct cells.
Trapped electron cloud bolometer relying on frequency shift.
Authors: Dehmelt H
Published: May 2006

An improved electron cloud bolometer is analyzed. In this device the cloud temperature is read out not via thermal noise induced by the electrons in a coupled LC circuit but via shift in their axial oscillation frequency in the Penning trap confining them. This shift occurs because as the electron cloud expands with increasing temperature, the average restoring force in the slightly anharmonic trap does change perceptibly. The scheme will be useful in exploring the microwave mode structure of the trap cavity and in locating magnetic field values for which the cavity-induced shift in the measured electron g factor disappears.
A membrane-delimited pathway of G-protein regulation of the guard-cell inward K+ channel.
Authors: Wu W H , Assmann S M
Published: May 2006

GTP-binding protein (G-protein) regulation of inward rectifying K+ channels in the plasma membrane of Vicia (Vicia faba L.) guard cells has previously been demonstrated at the whole-cell level. However, whether a cytosolic signal transduction chain is required for G-protein regulation of K+ channels in Vicia guard cells, or in any plant cell type, remains unknown. In the present study, we assayed effects of several G-protein regulators on inward K+ channels in isolated inside-out membrane patches from Vicia guard cell protoplasts. Guanosine 5'-[gamma-thio]triphosphate, a nonhydrolyzable GTP analog that locks G proteins into their activated state, decreased the open state probability (Po) of single inward K+ channels. This decrease in Po was accompanied by an increase in one of the closed time constants of the K+ channel. Guanosine 5'-[beta-thio]diphosphate, a GDP analog that locks G proteins into their inactivated state, slightly increased the Po of the inward K+ channel and shortened the closed time constants. Pertussis toxin and cholera toxin, which ADP-ribosylate G proteins at different sites, decreased the Po of the inward K+ channel. Our data indicate that G proteins can act via a membrane-delimited pathway to regulate inward K+ channels in the guard-cell plasma membrane.
Central effects of baroreceptor activation in humans: attenuation of skeletal reflexes and pain perception.
Authors: Dworkin B R , Elbert T , Rau H , Birbaumer N , Pauli P , Droste C , Brunia C H
Published: May 2006

Activating the arterial baroreceptors blunts pain sensation and produces other forms of central nervous system inhibition in animals. These effects may be important to blood pressure regulation but have not been rigorously verified in humans. We describe (i) a noninvasive behaviorally unbiased method for baroreceptor stimulation and (ii) the application of this method to measurement of baroreceptor-mediated attenuation of pain perception and of the Achilles tendon reflex. The findings are relevant to basic mechanisms of blood pressure stabilization and cardiovascular reactivity and may also have implications for noncompliance with antihypertensive medications and for the pathophysiology of essential hypertension.
Nonneutral evolution at the mitochondrial NADH dehydrogenase subunit 3 gene in mice.
Authors: Nachman M W , Boyer S N , Aquadro C F
Published: May 2006

The neutral theory of molecular evolution asserts that while many mutations are deleterious and rapidly eliminated from populations, those that we observe as polymorphisms within populations are functionally equivalent to each other and thus neutral with respect to fitness. Mitochondrial DNA (mtDNA) is widely used as a genetic marker in evolutionary studies and is generally assumed to evolve according to a strictly neutral model of molecular evolution. One prediction of the neutral theory is that the ratio of replacement (nonsynonymous) to silent (synonymous) nucleotide substitutions will be the same within and between species. We tested this prediction by measuring DNA sequence variation at the mitochondrially encoded NADH dehydrogenase subunit 3 (ND3) gene among 56 individual house mice, Mus domesticus. We also compared ND3 sequence from M. domesticus to ND3 sequence from Mus musculus and Mus spretus. A significantly greater number of replacement polymorphisms were observed within M. domesticus than expected based on comparisons to either M. musculus or M. spretus. This result challenges the conventional view that mtDNA evolves according to a strictly neutral model. However, this result is consistent with a nearly neutral model of molecular evolution and suggests that most amino acid polymorphisms at this gene may be slightly deleterious.