Showing papers in "Science in 1993"
TL;DR: The APOE-epsilon 4 allele is associated with the common late onset familial and sporadic forms of Alzheimer9s disease (AD) in 42 families with late onset AD.
Abstract: The apolipoprotein E type 4 allele (APOE-epsilon 4) is genetically associated with the common late onset familial and sporadic forms of Alzheimer9s disease (AD). Risk for AD increased from 20% to 90% and mean age at onset decreased from 84 to 68 years with increasing number of APOE-epsilon 4 alleles in 42 families with late onset AD. Thus APOE-epsilon 4 gene dose is a major risk factor for late onset AD and, in these families, homozygosity for APOE-epsilon 4 was virtually sufficient to cause AD by age 80.
8,669Â citations
TL;DR: A role for TNF-alpha in obesity and particularly in the insulin resistance and diabetes that often accompany obesity is indicated.
Abstract: Tumor necrosis factor-alpha (TNF-alpha) has been shown to have certain catabolic effects on fat cells and whole animals. An induction of TNF-alpha messenger RNA expression was observed in adipose tissue from four different rodent models of obesity and diabetes. TNF-alpha protein was also elevated locally and systemically. Neutralization of TNF-alpha in obese fa/fa rats caused a significant increase in the peripheral uptake of glucose in response to insulin. These results indicate a role for TNF-alpha in obesity and particularly in the insulin resistance and diabetes that often accompany obesity.
7,347Â citations
Journal Article•
5,981Â citations
TL;DR: Two broad mechanisms--oxidative stress and excessive activation of glutamate receptors--are converging and represent sequential as well as interacting processes that provide a final common pathway for cell vulnerability in the brain.
Abstract: There is an increasing amount of experimental evidence that oxidative stress is a causal, or at least an ancillary, factor in the neuropathology of several adult neurodegenerative disorders, as well as in stroke, trauma, and seizures. At the same time, excessive or persistent activation of glutamate-gated ion channels may cause neuronal degeneration in these same conditions. Glutamate and related acidic amino acids are thought to be the major excitatory neurotransmitters in brain and may be utilized by 40 percent of the synapses. Thus, two broad mechanisms--oxidative stress and excessive activation of glutamate receptors--are converging and represent sequential as well as interacting processes that provide a final common pathway for cell vulnerability in the brain. The broad distribution in brain of the processes regulating oxidative stress and mediating glutamatergic neurotransmission may explain the wide range of disorders in which both have been implicated. Yet differential expression of components of the processes in particular neuronal systems may account for selective neurodegeneration in certain disorders.
3,844Â citations
TL;DR: Analysis of cortical and thalamic networks at many levels, from molecules to single neurons to large neuronal assemblies, with a variety of techniques, is beginning to yield insights into the mechanisms of the generation, modulation, and function of brain oscillations.
Abstract: Sleep is characterized by synchronized events in billions of synaptically coupled neurons in thalamocortical systems. The activation of a series of neuromodulatory transmitter systems during awakening blocks low-frequency oscillations, induces fast rhythms, and allows the brain to recover full responsiveness. Analysis of cortical and thalamic networks at many levels, from molecules to single neurons to large neuronal assemblies, with a variety of techniques, ranging from intracellular recordings in vivo and in vitro to computer simulations, is beginning to yield insights into the mechanisms of the generation, modulation, and function of brain oscillations.
3,382Â citations
TL;DR: In embryonic midbrain cultures, recombinant human GDNF promoted the survival and morphological differentiation of dopaminergic neurons and increased their high-affinity dopamine uptake and did not increase total neuron or astrocyte numbers or transmitter uptake.
Abstract: A potent neurotrophic factor that enhances survival of midbrain dopaminergic neurons was purified and cloned. Glial cell line-derived neurotrophic factor (GDNF) is a glycosylated, disulfide-bonded homodimer that is a distantly related member of the transforming growth factor-beta superfamily. In embryonic midbrain cultures, recombinant human GDNF promoted the survival and morphological differentiation of dopaminergic neurons and increased their high-affinity dopamine uptake. These effects were relatively specific; GDNF did not increase total neuron or astrocyte numbers nor did it increase transmitter uptake by gamma-aminobutyric-containing and serotonergic neurons. GDNF may have utility in the treatment of Parkinson's disease, which is marked by progressive degeneration of midbrain dopaminergic neurons.
3,236Â citations
TL;DR: This regulatory pathway may have evolved to enable innate immune cells, through interactions with microbial pathogens, to direct development of specific immunity toward the appropriate TH1 phenotype.
Abstract: Development of the appropriate CD4+ T helper (TH) subset during an immune response is important for disease resolution. With the use of naive, ovalbumin-specific alpha beta T cell receptor transgenic T cell, it was found that heat-killed Listeria monocytogenes induced TH1 development in vitro through macrophage production of interleukin-12 (IL-12). Moreover, inhibition of macrophage production of IL-12 may explain the ability of IL-10 to suppress TH1 development. Murine immune responses to L. monocytogenes in vivo are of the appropriate TH1 phenotype. Therefore, this regulatory pathway may have evolved to enable innate immune cells, through interactions with microbial pathogens, to direct development of specific immunity toward the appropriate TH phenotype.
3,193Â citations
TL;DR: Colorectal tumor DNA was examined for somatic instability at (CA)n repeats on human chromosomes 5q, 15q, 17p, and 18q, and this instability was significantly correlated with the tumor's location in the proximal colon and with increased patient survival and loss of heterozygosity.
Abstract: Colorectal tumor DNA was examined for somatic instability at (CA)n repeats on human chromosomes 5q, 15q, 17p, and 18q. Differences between tumor and normal DNA were detected in 25 of the 90 (28 percent) tumors examined. This instability appeared as either a substantial change in repeat length (often heterogeneous in nature) or a minor change (typically two base pairs). Microsatellite instability was significantly correlated with the tumor's location in the proximal colon (P = 0.003), with increased patient survival (P = 0.02), and, inversely, with loss of heterozygosity for chromosomes 5q, 17p, and 18q. These data suggest that some colorectal cancers may arise through a mechanism that does not necessarily involve loss of heterozygosity.
3,093Â citations
TL;DR: The results suggest that integrins act as mechanoreceptors and transmit mechanical signals to the cytoskeleton, which may be mediated simultaneously at multiple locations inside the cell through force-induced rearrangements within a tensionally integrated cytos skeleton.
Abstract: Mechanical stresses were applied directly to cell surface receptors with a magnetic twisting device. The extracellular matrix receptor, integrin beta 1, induced focal adhesion formation and supported a force-dependent stiffening response, whereas nonadhesion receptors did not. The cytoskeletal stiffness (ratio of stress to strain) increased in direct proportion to the applied stress and required intact microtubules and intermediate filaments as well as microfilaments. Tensegrity models that incorporate mechanically interdependent struts and strings that reorient globally in response to a localized stress mimicked this response. These results suggest that integrins act as mechanoreceptors and transmit mechanical signals to the cytoskeleton. Mechanotransduction, in turn, may be mediated simultaneously at multiple locations inside the cell through force-induced rearrangements within a tensionally integrated cytoskeleton.
2,899Â citations
TL;DR: Molecular features of "familial" cancers were compared with those of sporadic colon cancers, and a mechanism for familial tumorigenesis different from that mediated by classic tumor suppressor genes is suggested.
Abstract: A predisposition to colorectal cancer is shown to be linked to markers on chromosome 2 in some families. Molecular features of "familial" cancers were compared with those of sporadic colon cancers. Neither the familial nor sporadic cancers showed loss of heterozygosity for chromosome 2 markers, and the incidence of mutations in KRAS, P53, and APC was similar in the two groups of tumors. Most of the familial cancers, however, had widespread alterations in short repeated DNA sequences, suggesting that numerous replication errors had occurred during tumor development. Thirteen percent of sporadic cancers had identical abnormalities and these cancers shared biologic properties with the familial cases. These data suggest a mechanism for familial tumorigenesis different from that mediated by classic tumor suppressor genes.
2,717Â citations
TL;DR: A gene discovered by positional cloning has been identified as the von Hippel-Lindau (VHL) disease tumor suppressor gene, and a restriction fragment encompassing the gene showed rearrangements in 28 of 221 VHL kindreds.
Abstract: A gene discovered by positional cloning has been identified as the von Hippel-Lindau (VHL) disease tumor suppressor gene. A restriction fragment encompassing the gene showed rearrangements in 28 of 221 VHL kindreds. Eighteen of these rearrangements were due to deletions in the candidate gene, including three large nonoverlapping deletions. Intragenic mutations were detected in cell lines derived from VHL patients and from sporadic renal cell carcinomas. The VHL gene is evolutionarily conserved and encodes two widely expressed transcripts of approximately 6 and 6.5 kilobases. The partial sequence of the inferred gene product shows no homology to other proteins, except for an acidic repeat domain found in the procyclic surface membrane glycoprotein of Trypanosoma brucei.
TL;DR: To generate a viral antigen for presentation to the immune system without the limitations of direct peptide delivery or viral vectors, plasmid DNA encoding influenza A nucleop protein was injected into the quadriceps of BALB/c mice and resulted in the generation of nucleoprotein-specific CTLs.
Abstract: Cytotoxic T lymphocytes (CTLs) specific for conserved viral antigens can respond to different strains of virus, in contrast to antibodies, which are generally strain-specific. The generation of such CTLs in vivo usually requires endogenous expression of the antigen, as occurs in the case of virus infection. To generate a viral antigen for presentation to the immune system without the limitations of direct peptide delivery or viral vectors, plasmid DNA encoding influenza A nucleoprotein was injected into the quadriceps of BALB/c mice. This resulted in the generation of nucleoprotein-specific CTLs and protection from a subsequent challenge with a heterologous strain of influenza A virus, as measured by decreased viral lung titers, inhibition of mass loss, and increased survival.
TL;DR: Parallel recording methods outlined here make possible the study of the dynamics of neuronal interactions during unique behavioral events, which suggests that new spatial information creates conditions in the hippocampal circuitry that are conducive to the synaptic modification presumed to be involved in learning.
Abstract: Ensemble recordings of 73 to 148 rat hippocampal neurons were used to predict accurately the animals' movement through their environment, which confirms that the hippocampus transmits an ensemble code for location. In a novel space, the ensemble code was initially less robust but improved rapidly with exploration. During this period, the activity of many inhibitory cells was suppressed, which suggests that new spatial information creates conditions in the hippocampal circuitry that are conducive to the synaptic modification presumed to be involved in learning. Development of a new population code for a novel environment did not substantially alter the code for a familiar one, which suggests that the interference between the two spatial representations was very small. The parallel recording methods outlined here make possible the study of the dynamics of neuronal interactions during unique behavioral events.
TL;DR: A large number of key technical issues need to be resolved before gene therapy can be safely and effectively applied in the clinic, and future technological developments will be critical for the successful practice of gene therapy.
Abstract: The development over the past decade of methods for delivering genes to mammalian cells has stimulated great interest in the possibility of treating human disease by gene-based therapies. However, despite substantial progress, a number of key technical issues need to be resolved before gene therapy can be safely and effectively applied in the clinic. Future technological developments, particularly in the areas of gene delivery and cell transplantation, will be critical for the successful practice of gene therapy.
TL;DR: A mathematical definition of this "local multiple alignment" problem suitable for full computer automation has been used to develop a new and sensitive algorithm, based on the statistical method of iterative sampling, that finds an optimized local alignment model for N sequences in N-linear time, requiring only seconds on current workstations.
Abstract: A wealth of protein and DNA sequence data is being generated by genome projects and other sequencing efforts. A crucial barrier to deciphering these sequences and understanding the relations among them is the difficulty of detecting subtle local residue patterns common to multiple sequences. Such patterns frequently reflect similar molecular structures and biological properties. A mathematical definition of this "local multiple alignment" problem suitable for full computer automation has been used to develop a new and sensitive algorithm, based on the statistical method of iterative sampling. This algorithm finds an optimized local alignment model for N sequences in N-linear time, requiring only seconds on current workstations, and allows the simultaneous detection and optimization of multiple patterns and pattern repeats. The method is illustrated as applied to helix-turn-helix proteins, lipocalins, and prenyltransferases.
TL;DR: The three-dimensional structure of the head portion of myosin, or subfragment-1, which contains both the actin and nucleotide binding sites, is described, and this structure of a molecular motor was determined by single crystal x-ray diffraction.
Abstract: Directed movement is a characteristic of many living organisms and occurs as a result of the transformation of chemical energy into mechanical energy. Myosin is one of three families of molecular motors that are responsible for cellular motility. The three-dimensional structure of the head portion of myosin, or subfragment-1, which contains both the actin and nucleotide binding sites, is described. This structure of a molecular motor was determined by single crystal x-ray diffraction. The data provide a structural framework for understanding the molecular basis of motility.
TL;DR: The calcium spark is the consequence of elementary events underlying excitation-contraction coupling and provides an explanation for both spontaneous and triggered changes in the intracellular calcium concentration in the mammalian heart.
Abstract: Spontaneous local increases in the concentration of intracellular calcium, called "calcium sparks," were detected in quiescent rat heart cells with a laser scanning confocal microscope and the fluorescent calcium indicator fluo-3 Estimates of calcium flux associated with the sparks suggest that calcium sparks result from spontaneous openings of single sarcoplasmic reticulum (SR) calcium-release channels, a finding supported by ryanodine-dependent changes of spark kinetics At resting intracellular calcium concentrations, these SR calcium-release channels had a low rate of opening (approximately 00001 per second) An increase in the calcium content of the SR, however, was associated with a fourfold increase in opening rate and resulted in some sparks triggering propagating waves of increased intracellular calcium concentration The calcium spark is the consequence of elementary events underlying excitation-contraction coupling and provides an explanation for both spontaneous and triggered changes in the intracellular calcium concentration in the mammalian heart
TL;DR: In this article, the authors demonstrated a miniaturized system for sample handling and separation using electrophoresis-based separations of amino acids with up to 75,000 theoretical plates in about 15 seconds.
Abstract: Micromachining technology was used to prepare chemical analysis systems on glass chips (1 centimeter by 2 centimeters or larger) that utilize electroosmotic pumping to drive fluid flow and electrophoretic separation to distinguish sample components. Capillaries 1 to 10 centimeters long etched in the glass (cross section, 10 micrometers by 30 micrometers) allow for capillary electrophoresis-based separations of amino acids with up to 75,000 theoretical plates in about 15 seconds, and separations of about 600 plates can be effected within 4 seconds. Sample treatment steps within a manifold of intersecting capillaries were demonstrated for a simple sample dilution process. Manipulation of the applied voltages controlled the directions of fluid flow within the manifold. The principles demonstrated in this study can be used to develop a miniaturized system for sample handling and separation with no moving parts.
TL;DR: IFN-gamma is essential for the function of several cell types of the murine immune system and has impaired production of macrophage antimicrobial products and reduced expression of Macrophage major histocompatibility complex class II antigens.
Abstract: Interferon-gamma (IFN-gamma) is a pleiotrophic cytokine with immunomodulatory effects on a variety of immune cells. Mice with a targeted disruption of the IFN-gamma gene were generated. These mice developed normally and were healthy in the absence of pathogens. However, mice deficient in IFN-gamma had impaired production of macrophage antimicrobial products and reduced expression of macrophage major histocompatibility complex class II antigens. IFN-gamma-deficient mice were killed by a sublethal dose of the intracellular pathogen Mycobacterium bovis. Splenocytes exhibited uncontrolled proliferation in response to mitogen and alloantigen. After a mixed lymphocyte reaction, T cell cytolytic activity was enhanced against allogeneic target cells. Resting splenic natural killer cell activity was reduced in IFN-gamma-deficient mice. Thus, IFN-gamma is essential for the function of several cell types of the murine immune system.
TL;DR: A reconciliation of findings with the traditional analysis is presented based on the "pseudospectra" of the linearized problem, which imply that small perturbations to the smooth flow may be amplified by factors on the order of 105 by a linear mechanism even though all the eigenmodes decay monotonically.
Abstract: Fluid flows that are smooth at low speeds become unstable and then turbulent at higher speeds. This phenomenon has traditionally been investigated by linearizing the equations of flow and testing for unstable eigenvalues of the linearized problem, but the results of such investigations agree poorly in many cases with experiments. Nevertheless, linear effects play a central role in hydrodynamic instability. A reconciliation of these findings with the traditional analysis is presented based on the "pseudospectra" of the linearized problem, which imply that small perturbations to the smooth flow may be amplified by factors on the order of 105 by a linear mechanism even though all the eigenmodes decay monotonically. The methods suggested here apply also to other problems in the mathematical sciences that involve nonorthogonal eigenfunctions.
TL;DR: The effects of C2-ceramide on DNA fragmentation were prevented by the protein kinase C activator phorbol 12-myristate 13-acetate, which suggests the existence of two opposing intracellular pathways in the regulation of apoptosis.
Abstract: Sphingomyelin hydrolysis and ceramide generation have been implicated in a signal transduction pathway that mediates the effects of tumor necrosis factor-alpha (TNF-alpha) and other agents on cell growth and differentiation In many leukemic cells, TNF-alpha causes DNA fragmentation, which leads to programmed cell death (apoptosis) C2-ceramide (06 to 5 microM), a synthetic cell-permeable ceramide analog, induced internucleosomal DNA fragmentation, which was inhibited by zinc ion Other amphiphilic lipids failed to induce apoptosis The closely related C2-dihydroceramide was also ineffective, which suggests a critical role for the sphingolipid double bond The effects of C2-ceramide on DNA fragmentation were prevented by the protein kinase C activator phorbol 12-myristate 13-acetate, which suggests the existence of two opposing intracellular pathways in the regulation of apoptosis
TL;DR: Salicylic acid is essential for the development of systemic acquired resistance in tobacco and was investigated in transgenic tobacco plants harboring a bacterial gene encoding salicylate hydroxylase.
Abstract: It has been proposed that salicylic acid acts as an endogenous signal responsible for inducing systemic acquired resistance in plants. The contribution of salicylic acid to systemic acquired resistance was investigated in transgenic tobacco plants harboring a bacterial gene encoding salicylate hydroxylase, which converts salicylic acid to catechol. Transgenic plants that express salicylate hydroxylase accumulated little or no salicylic acid and were defective in their ability to induce acquired resistance against tobacco mosaic virus. Thus, salicylic acid is essential for the development of systemic acquired resistance in tobacco.
TL;DR: The proto-oncogene bcl-2 inhibits apoptotic and necrotic neural cell death by decreasing the net cellular generation of reactive oxygen species and lipid peroxides as discussed by the authors.
Abstract: The proto-oncogene bcl-2 inhibits apoptotic and necrotic neural cell death. Expression of Bcl-2 in the GT1-7 neural cell line prevented death as a result of glutathione depletion. Intracellular reactive oxygen species and lipid peroxides rose rapidly in control cells depleted of glutathione, whereas cells expressing Bcl-2 displayed a blunted increase and complete survival. Modulation of the increase in reactive oxygen species influenced the degree of cell death. Yeast mutants null for superoxide dismutase were partially rescued by expression of Bcl-2. Thus, Bcl-2 prevents cell death by decreasing the net cellular generation of reactive oxygen species.
TL;DR: The spatial relation between the ATP binding pocket on myosin and the major contact area on actin suggests a working hypothesis for the crossbridge cycle that is consistent with previous independent structural and biochemical studies.
Abstract: Muscle contraction consists of a cyclical interaction between myosin and actin driven by the concomitant hydrolysis of adenosine triphosphate (ATP). A model for the rigor complex of F actin and the myosin head was obtained by combining the molecular structures of the individual proteins with the low-resolution electron density maps of the complex derived by cryo-electron microscopy and image analysis. The spatial relation between the ATP binding pocket on myosin and the major contact area on actin suggests a working hypothesis for the crossbridge cycle that is consistent with previous independent structural and biochemical studies.
TL;DR: Plankton samples from Japanese ballast water released in Oregon contained 367 taxa, and most taxa with a planktonic phase in their life cycle were found in ballastWater, as were all major marine habitat and trophic groups.
Abstract: Ocean-going ships carry, as ballast, seawater that is taken on in port and released at subsequent ports of call. Plankton samples from Japanese ballast water released in Oregon contained 367 taxa. Most taxa with a planktonic phase in their life cycle were found in ballast water, as were all major marine habitat and trophic groups. Transport of entire coastal planktonic assemblages across oceanic barriers to similar habitats renders bays, estuaries, and inland waters among the most threatened ecosystems in the world. Presence of taxonomically difficult or inconspicuous taxa in these samples suggests that ballast water invasions are already pervasive.
TL;DR: A synthesis of laboratory studies and geophysical and geological observations shows that transitions between diffusion and dislocation creep likely occur in the Earth's upper mantle.
Abstract: Rheological properties of the upper mantle of the Earth play an important role in the dynamics of the lithosphere and asthenosphere. However, such fundamental issues as the dominant mechanisms of flow have not been well resolved. A synthesis of laboratory studies and geophysical and geological observations shows that transitions between diffusion and dislocation creep likely occur in the Earth's upper mantle. The hot and shallow upper mantle flows by dislocation creep, whereas cold and shallow or deep upper mantle may flow by diffusion creep. When the stress increases, grain size is reduced and the upper mantle near the transition between these two regimes is weakened. Consequently, deformation is localized and the upper mantle is decoupled mechanically near these depths.
TL;DR: Mutant mice offer the possibility for the further elucidation of IFN-gamma-mediated functions by transgenic cell- or tissue-specific reconstitution of a functional receptor.
Abstract: Interferon-gamma (IFN-gamma) exerts pleiotropic effects, including antiviral activity, stimulation of macrophages and natural killer cells, and increased expression of major histocompatibility complex antigens. Mice without the IFN-gamma receptor had no overt anomalies, and their immune system appeared to develop normally. However, mutant mice had a defective natural resistance, they had increased susceptibility to infection by Listeria monocytogenes and vaccinia virus despite normal cytotoxic and T helper cell responses. Immunoglobulin isotype analysis revealed that IFN-gamma is necessary for a normal antigen-specific immunoglobulin G2a response. These mutant mice offer the possibility for the further elucidation of IFN-gamma-mediated functions by transgenic cell- or tissue-specific reconstitution of a functional receptor.
TL;DR: Taxomyces andreanae, a fungal endophyte, was isolated from the phloem (inner bark) of the Pacific yew, Taxus brevifolia, and taxol was identified by mass spectrometry, chromatography, and reactivity with monoclonal antibodies specific for taxol.
Abstract: Taxomyces andreanae, a fungal endophyte, was isolated from the phloem (inner bark) of the Pacific yew, Taxus brevifolia. The fungus is hyphomyceteous and, when grown in a semi-synthetic liquid medium, produced taxol and related compounds. Taxol was identified by mass spectrometry, chromatography, and reactivity with monoclonal antibodies specific for taxol. Both [1-14C]acetic acid and L-[U-14C]phenylalanine served as precursors of [14C]taxol in fungal cultures. No taxol was detected in zero-time cultures or in the small agar plugs used to inoculate the culture flasks.
TL;DR: Although this rate of deforestation is lower than previous estimates, the effect on biological diversity is greater and tropical forest habitat, severely affected with respect to biological diversity, increased.
Abstract: Landsat satellite imagery covering the entire forested portion of the Brazilian Amazon Basin was used to measure, for 1978 and 1988, deforestation, fragmented forest, defined as areas less than 100 square kilometers surrounded by deforestation, and edge effects of 1 kilometer into forest from adjacent areas of deforestation. Tropical deforestation increased from 78,000 square kilometers in 1978 to 230,000 square kilometers in 1988 while tropical forest habitat, severely affected with respect to biological diversity, increased from 208,000 to 588,000 square kilometers. Although this rate of deforestation is lower than previous estimates, the effect on biological diversity is greater.
TL;DR: In primary cultures of olfactory neurons, zinc protoporphyrin-9, a potent selective inhibitor of heme oxygenase, depletes endogenous guanosine 3',5'-monophosphate (cGMP), suggesting that carbon monoxide may be a physiologic regulator of cGMP.
Abstract: Carbon monoxide, an activator of guanylyl cyclase, is formed by the action of the enzyme heme oxygenase. By in situ hybridization in brain slices, discrete neuronal localization of messenger RNA for the constitutive form of heme oxygenase throughout the brain has been demonstrated. This localization is essentially the same as that for soluble guanylyl cyclase messenger RNA. In primary cultures of olfactory neurons, zinc protoporphyrin-9, a potent selective inhibitor of heme oxygenase, depletes endogenous guanosine 3',5'-monophosphate (cGMP). Thus, carbon monoxide, like nitric oxide, may be a physiologic regulator of cGMP. These findings, together with the neuronal localizations of heme oxygenase, suggest that carbon monoxide may function as a neurotransmitter.