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Showing papers by "Max Planck Society published in 1990"


Journal ArticleDOI
27 Sep 1990-Nature
TL;DR: In this article, a new form of pure, solid carbon has been synthesized consisting of a somewhat disordered hexagonal close packing of soccer-ball-shaped C60 molecules.
Abstract: A new form of pure, solid carbon has been synthesized consisting of a somewhat disordered hexagonal close packing of soccer-ball-shaped C60 molecules. Infrared spectra and X-ray diffraction studies of the molecular packing confirm that the molecules have the anticipated 'fullerene' structure. Mass spectroscopy shows that the C70 molecule is present at levels of a few per cent. The solid-state and molecular properties of C60 and its possible role in interstellar space can now be studied in detail.

6,650 citations


Journal ArticleDOI
20 Apr 1990-Cell
TL;DR: Cet article synthese montre comment des recepteurs membranaires a activite tyrosine kinase peuvent etre impliques dans la transduction and notamment jouent le role de signal de the transduction.

5,536 citations


Book ChapterDOI
01 Nov 1990
TL;DR: Baltes et al. as discussed by the authors presented a psychological model for the study of successful aging that, they contend, is consistent with the propositional framework, based on the premise that successful individual development (including aging) is a process involving three components: selection, optimization, and compensation.
Abstract: The purpose of this chapter is twofold. First, we review research on the nature of psychological aging in terms of seven propositions. Second, we present a psychological model for the study of successful aging that, we contend, is consistent with the propositional framework. The approach advanced is based on the premise that successful, individual development (including aging) is a process involving three components: selection, optimization, and compensation. How these components of adaption are realized depends on the specific personal and societal circumstances individuals face and produce as they age. Introduction Two scientific concepts have had a major impact on our thinking about successful aging: interindividual variability and intraindividual plasticity (M. Baltes & P. Baltes, 1982; P. Baltes & M. Baltes, 1980; P. Baltes & Schaie, 1976). Reflection on the theoretical and policy-related implications of both concepts has suggested to us that there is much opportunity for the continual optimization of human development (see also Brim & Kagan, 1980; Labouvie-Vief, 1981; Lerner, 1984). Over the years, we have begun to believe that systematic age-related shifts in the extent of variability and plasticity are cornerstones for a developmental theory of human adaptation. Initial evidence for this perspective is available in our first attempt to formulate an agenda for successful aging (P. Baltes & M. Baltes, 1980). After reviewing research on variability and plasticity, we laid the groundwork for a prototheory of successful aging as an adaptive process involving the components of selection, optimization, and compensation.

3,419 citations


Book
01 Jan 1990
TL;DR: In this paper, the theory of the internal structure of stars and their evolution in time is introduced and the basic physics of stellar interiors, methods for solving the underlying equations, and the most important results necessary for understanding the wide variety of stellar types and phenomena.
Abstract: This book introduces the theory of the internal structure of stars and their evolution in time. It presents the basic physics of stellar interiors, methods for solving the underlying equations, and the most important results necessary for understanding the wide variety of stellar types and phenomena. The evolution of stars is discussed from their birth through normal evolution to possibly spectacular final stages. Chapters on stellar oscillations and rotation are included.

2,450 citations


Journal ArticleDOI
21 Dec 1990-Science
TL;DR: Widespread burning of biomass serves to clear land for shifting cultivation, to convert forests to agricultural and pastoral lands, and to remove dry vegetation in order to promote agricultural productivity and the growth of higher yield grasses, but it may also disturb biogeochemical cycles, especially that of nitrogen.
Abstract: The use of fire as a tool to manipulate the environment has been instrumental in the human conquest of Earth, the first evidence of the use of fires by early hominids dating back to 1–1.5 million years ago [1]. Even today, most human-ignited vegetation fires take place on the African continent, and its widespread, frequently burned savannas bear ample witness to this. Although natural fires can occur even in tropical forest regions [2, 3], the extent of fires has greatly expanded on all continents with the arrival of Homo sapiens. Measurements of charcoal in dated sediment cores have shown clear correlations between the rate of burning and human settlement [4]. Pollen records show a shift with human settlement from pyrophobic vegetation to pyrotolerant and pyrophilic species, testimony to the large ecological impact of human-induced fires.

2,424 citations



Journal ArticleDOI
TL;DR: Current knowledge of P-loops is discussed with the additional aim of illustrating the fascinating relationship between protein sequence, structure and function.

1,972 citations


Journal ArticleDOI
TL;DR: Inducible defenses are responses activated through a previous encounter with a consumer or competitor that confer some degree of resistance to subsequent attacks as discussed by the authors, which can affect the probability of individual survival and growth.
Abstract: Inducible defenses are responses activated through a previous encounter with a consumer or competitor that confer some degree of resistance to subsequent attacks. While the importance of inducible resistance has long been known in host-parasite interactions, it is only recently that its importance has emerged in other natural systems. Althought the structural defenses produced by invertebrates to their competitors and predators are by no means the same as an immune response triggered by parasites, these responses all share the properties of (1) specificity, (2) amplification and (3) memory. This review discusses the following ecological consequences and evolutionary causes of inducible defenses: (1) Inducible defenses render historical factors important in biological interactions and can affect the probability of individual survival and growth, as well as affect population dynamics of consumers in some circumstances. (2) Although the benefits of inducible defenses are often balanced by fitness costs, incl...

1,923 citations


Journal ArticleDOI
06 Sep 1990-Nature
TL;DR: The atomic models of the complex between rabbit skeletal muscle actin and bovine pancreatic deoxyribonuclease I both in the ATP and ADP forms have been determined byo X-ray analysis at an effective resolution of 2.8 Å and 3 Å.
Abstract: The atomic models of the complex between rabbit skeletal muscle actin and bovine pancreatic deoxyribonuclease I both in the ATP and ADP forms have been determined by X-ray analysis at an effective resolution of 2.8 A and 3A, respectively. The two structures are very similar. The actin molecule consists of two domains which can be further subdivided into two subdomains. ADP or ATP is located in the cleft between the domains with a calcium ion bound to the beta- or beta- and gamma-phosphates, respectively. The motif of a five-stranded beta sheet consisting of a beta meander and a right handed beta alpha beta unit appears in each domain suggesting that gene duplication might have occurred. These sheets have the same topology as that found in hexokinase.

1,802 citations


Journal ArticleDOI
06 Sep 1990-Nature
TL;DR: A unique orientation of the monomer with respect to the actin helix has been found and the main interactions are along the two-start helix with a contribution from a loop extending across the filament axis provided by the molecule in the adjacent strand.
Abstract: The F-actin filament has been constructed from the atomic structure of the actin monomer to fit the observed X-ray fibre diagram from oriented gels of F-actin. A unique orientation of the monomer with respect to the actin helix has been found. The main interactions are along the two-start helix with a contribution from a loop extending across the filament axis provided by the molecule in the adjacent strand. There are also contacts along the left-handed genetic helix.

1,636 citations


BookDOI
01 Jan 1990
TL;DR: In this article, the Bonn longitudinal study of aging: coping, life adjustment, and life satisfaction is presented, as well as risk and protective factors in the transition to young adulthood.
Abstract: Foreword Preface 1. Psychological perspectives on successful aging: the model of selective optimization with compensation 2. Medical perspectives upon successful aging 3. Successful aging in a post-retired society 4. The optimization of cognitive functioning in old age: predictions based on cohort-sequential and longitudinal data 5. The optimization of episodic remembering in old age 6. Peak performance and age: an examination of peak performance in sports 7. Personal control over development and quality of life perspectives in adulthood 8. Successful mastery of bereavement and widowhood: a life-course perspective 9. The Bonn longitudinal study of aging: coping, life adjustment, and life satisfaction 10. Risk and protective factors in the transition to young adulthood 11. Avoiding negative life outcomes: evidence from a forty-five year study 12. Developing behavioural genetics and successful aging Name index Subject index.

Journal ArticleDOI
03 Aug 1990-Science
TL;DR: Four cloned cDNAs encoding 900-amino acid putative glutamate receptors with approximately 70 percent sequence identity were isolated from a rat brain cDNA library and in situ hybridization revealed differential expression patterns of the cognate mRNAs throughout the brain.
Abstract: Four cloned cDNAs encoding 900-amino acid putative glutamate receptors with approximately 70 percent sequence identity were isolated from a rat brain cDNA library. In situ hybridization revealed differential expression patterns of the cognate mRNAs throughout the brain. Functional expression of the cDNAs in cultured mammalian cells generated receptors displaying alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-selective binding pharmacology (AMPA = quisqualate greater than glutamate greater than kainate) as well as cation channels gated by glutamate, AMPA, and kainate and blocked by 6,7-dinitroquinoxaline-2,3-dione (CNQX).

Journal ArticleDOI
TL;DR: A novel application of dynamic programming to the folding problem for RNA enables one to calculate the full equilibrium partition function for secondary structure and the probabilities of various substructures by a recursive scheme of polynomial order N3 in the sequence length N.
Abstract: A novel application of dynamic programming to the folding problem for RNA enables one to calculate the full equilibrium partition function for secondary structure and the probabilities of various substructures. In particular, both the partition function and the probabilities of all base pairs are computed by a recursive scheme of polynomial order N3 in the sequence length N. The temperature dependence of the partition function gives information about melting behavior for the secondary structure. The pair binding probabilities, the computation of which depends on the partition function, are visually summarized in a “box matrix” display and this provides a useful tool for examining the full ensemble of probable alternative equilibrium structures. The calculation of this ensemble representation allows a proper application and assessment of the predictive power of the secondary structure method, and yields important information on alternatives and intermediates in addition to local information about base pair opening and slippage. The results are illustrated for representative tRNA, 5S RNA, and self-replicating and self-splicing RNA molecules, and allow a direct comparison with enzymatic structure probes. The effect of changes in the thermodynamic parameters on the equilibrium ensemble provides a further sensitivity check to the predictions.

Journal ArticleDOI
07 Sep 1990-Cell
TL;DR: Identification of two unique mutations within cardiac MHC genes in all individuals with FHC from two unrelated families demonstrates that defects in the cardiac M HC genes can cause this disease.

Journal ArticleDOI
28 Sep 1990-Science
TL;DR: These results identify a switch in the molecular and functional properties of glutamate receptors operated by alternative splicing.
Abstract: In the central nervous system (CNS), the principal mediators of fast synaptic excitatory neurotransmission are L-glutamate-gated ion channels that are responsive to the glutamate agonist alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA). In each member of a family of four abundant AMPA receptors, a small segment preceding the predicted fourth transmembrane region has been shown to exist in two versions with different amino acid sequences. These modules, designated "flip" and "flop," are encoded by adjacent exons of the receptor genes and impart different pharmacological and kinetic properties on currents evoked by L-glutamate or AMPA, but not those evoked by kainate. For each receptor, the alternatively spliced messenger RNAs show distinct expression patterns in rat brain, particularly in the CA1 and CA3 fields of the hippocampus. These results identify a switch in the molecular and functional properties of glutamate receptors operated by alternative splicing.

Journal ArticleDOI
22 Mar 1990-Nature
TL;DR: Taking advantage of sequence identities between NGF and BDNF, a third member of this family of secretory proteins is identified, which is named neurotrophin-3, and a remarkable number of amino acid identities are revealed, including all cys-teine residues.
Abstract: The survival and functional maintenance of vertebrate neurons critically depends on the availability of specific neurotrophic factors. So far, only two such factors, nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) have been characterized and shown to have the typical features of secretory proteins. This characterization has been possible because of the extraordinarily large quantities of NGF in some adult tissues, and the virtually unlimited availability of brain tissue from which BDNF was isolated. Both NGF and BDNF promote the survival of distinct neuronal populations in vivo and are related in their primary structure, suggesting that they are members of a gene family. Although there is little doubt about the existence of other such proteins, their low abundance has rendered their identification and characterization difficult. Taking advantage of sequence identities between NGF and BDNF, we have now identified a third member of this family, which we name neurotrophin-3. Both the tissue distribution of the messenger RNA and the neuronal specificity of this secretory protein differ from those of NGF and BDNF. Alignment of the sequences of the three proteins reveals a remarkable number of amino acid identities, including all cysteine residues. This alignment also delineates four variable domains, each of 7-11 amino acids, indicating structural elements presumably involved in the neuronal specificity of these proteins.

Journal ArticleDOI
TL;DR: In this paper, the authors study the singularities of (1) which can occur for nonconvex initial data and characterize the asymptotic behavior of the hypersurface Mt near a singularity using rescaling techniques.
Abstract: is satisfied. Here H(p,ή is the mean curvature vector of the hypersurface Mt at F(/?, t). We saw in [7] that (1) is a quasilinear parabolic system with a smooth solution at least on some short time interval. Moreover, it was shown that for convex initial data Mo the surfaces Mt contract smoothly to a single point in finite time and become spherical at the end of the contraction. Here we want to study the singularities of (1) which can occur for nonconvex initial data. Our aim is to characterize the asymptotic behavior of Mt near a singularity using rescaling techniques. These methods have been used in the theory of minimal surfaces and more recently in the study of semilinear heat equations [3], [4]. An important tool of this approach is a monotonicity formula, which we establish in §3. Assuming then a natural upper bound for the growth rate of the curvature we show that after appropriate rescaling near the singularity the surfaces Mt approach a selfsimilar solution of (1). In §4 we consider surfaces Mt9 n > 2, of positive mean curvature and show that in this case the only compact selfsimilar solutions of (1) are spheres. Finally, in §5 we study the model-problem of a rotationally symmetric shrinking neck. We prove that the natural growth rate estimate is valid in this case and that the rescaled solution asymptotically approaches a cylinder.

01 Jan 1990
TL;DR: The focus of this chapter is on the course of action, which is understood to be a temporal, horizontal path starting with a person's desires and ending with the evaluation of the achieved action outcome.
Abstract: The focus of this chapter is on the course of action, which is understood to be a temporal, horizontal path starting with a person's desires and ending with the evaluation of the achieved action outcome. The phenomena of choosing an action goal, initiating the appropriate actions, and executing these actions are assumed to be situated in between. This comprehensive perspective conceives of the course of action as a number of consecutive, distinct segments or phases. It raises questions concerning how people choose action goals, plan and enact their execution, and eaaluate thek efforts. The concept of "mind-set" is employed to find answers to these questions in terms of the cognitive processes or orientations that allow for easy completion of the different action phases.

Journal ArticleDOI
TL;DR: A mechanism for GTP hydrolysis involving mainly Gln61 and Glu63 as activating species for in‐line attack of water as well as a mechanism for rate enhancement by GAP is proposed.
Abstract: The crystal structure of the H-ras oncogene protein p21 complexed to the slowly hydrolysing GTP analogue GppNp has been determined at 1.35 A resolution. 211 water molecules have been built into the electron density. The structure has been refined to a final R-factor of 19.8% for all data between 6 A and 1.35 A. The binding sites of the nucleotide and the magnesium ion are revealed in high detail. For the stretch of amino acid residues 61-65, the temperature factors of backbone atoms are four times the average value of 16.1 A2 due to the multiple conformations. In one of these conformations, the side chain of Gln61 makes contact with a water molecule, which is perfectly placed to be the nucleophile attacking the gamma-phosphate of GTP. Based on this observation, we propose a mechanism for GTP hydrolysis involving mainly Gln61 and Glu63 as activating species for in-line attack of water. Nucleophilic displacement is facilitated by hydrogen bonds from residues Thr35, Gly60 and Lys16. A mechanism for rate enhancement by GAP is also proposed.

Journal ArticleDOI
TL;DR: The distribution of the BDNF mRNA in the adult mouse brain is reported on, using quantitative Northern blot analysis and in situ hybridization, to suggest that BDNF may play an important role in the CNS for a wide variety of adult neurons.
Abstract: Brain-derived neurotrophic factor (BDNF) is a protein that allows the survival of specific neuronal populations. This study reports on the distribution of the BDNF mRNA in the adult mouse brain, where the BDNF gene is strongly expressed, using quantitative Northern blot analysis and in situ hybridization. All brain regions examined were found to contain substantial amounts of BDNF mRNA, the highest levels being found in the hippocampus followed by the cerebral cortex. In the hippocampus, which is also the site of highest nerve growth factor (NGF) gene expression in the central nervous system (CNS), there is approximately 50-fold more BDNF mRNA than NGF mRNA. In other brain regions, such as the granule cell layer of the cerebellum, the differences between the levels of BDNF and NGF mRNAs are even more pronounced. The BDNF mRNA was localized by in situ hybridization in hippocampal neurons (pyramidal and granule cells). These data suggest that BDNF may play an important role in the CNS for a wide variety of adult neurons.

PatentDOI
TL;DR: In this article, the authors proposed a method for cloning and expression of ciliary neurotrophic factor (CNTF) and provided a means for producing human CNTF utilizing human CCL-encoding nucleic acid sequences.
Abstract: The present invention relates to nucleic acid sequences encoding ciliary neurotrophic factor (CNTF) and to the proteins, peptides, and derivatives produced therefrom. In various embodiments of the invention, the nucleic acid sequences, proteins, and peptides of the invention may be used in the treatment of a variety of neurological diseases and disorders, including Alzheimer's disease. In a specific embodiment of the invention, CNTF may be used to support the growth of spinal cord neurons, thereby providing a method of treating spinal cord damage caused by trauma infarction, infection, nutritional deficiency or toxic agents. The present invention also relates to a novel method for producing substantially pure CNTF. The invention also relates to pharmaceutical compositions comprising effective amounts of CNTF gene products which may be used in the diagnosis and treatment of a variety of neurological diseases and disorders. The present invention relates to the cloning sequencing and expression of CNTF and provides, for the first time, a means for producing human CNTF utilizing human CNTF-encoding nucleic acid sequences. Furthermore, the CNTF nucleic acid sequences of the invention may be utilized to identify nucleic acid sequences encoding CNTF or CNTF-homologous molecules in a variety of species and tissues.

Journal ArticleDOI
TL;DR: In this article, it was shown that there is a stage of lexical access to a content word where only its meaning is activated, followed by a stage where only their form is activated.

Journal ArticleDOI
TL;DR: The results suggest that the synthesis of these two neurotrophic factors in the brain is regulated by neuronal activity via non‐NMDA glutamate receptors.
Abstract: The mRNAs of nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF) exhibit a similar, though not identical, regional and cellular distribution in the rodent brain. In situ hybridization experiments have shown that BDNF, like NGF, is predominantly expressed by neurons. The neuronal localization of the mRNAs of these two neurotrophic molecules raised the question as to whether neuronal activity might be involved in the regulation of their synthesis. After we had demonstrated that depolarization with high potassium (50 mM) resulted in an increase in the levels of both BDNF and NGF mRNAs in cultures of hippocampal neurons, we investigated the effect of a large number of transmitter substances. Kainic acid, a glutamate receptor agonist, was by far the most effective in increasing BDNF and NGF mRNA levels in the neurons, but neither N-methyl-D-aspartic acid (NMDA) nor inhibitors of the NMDA glutamate receptors had any effect. However, the kainic acid mediated increase was blocked by antagonists of non-NMDA receptors. Kainic acid also elevated levels of BDNF and NGF mRNAs in rat hippocampus and cortex in vivo. These results suggest that the synthesis of these two neurotrophic factors in the brain is regulated by neuronal activity via non-NMDA glutamate receptors.

Journal ArticleDOI
TL;DR: Graham Collingridge and Wolf Singer describe how NMDA receptors can endow synapses with hebbian-like properties and discuss how these may be used by vertebrates for associative learning and experience-dependent modifications of synaptic connections during development.

Journal ArticleDOI
TL;DR: The differential oxidation of HE and DCFH during simultaneous cellular staining permits the analysis of up to three functionally different neutrophil populations in septic patients and is of interest for the determination of disease‐related alterations of oxygen metabolism in quiescent and stimulated leukocytes.
Abstract: Hydroethidine (HE) and 2',7'-dichlorofluorescin (DCFH) were used for the flow cytometric measurement of reactive oxygen metabolites in leukocytes. Hydroethidine and DCFH were both rapidly oxidized in a cell-free cuvette assay to ethidium bromide (EB) and 2',7'-dichlorofluorescein (DCF) by H2O2 and peroxidase, but not by H2O2 alone, while only HE was oxidized by KO2, a source of O2-. Quiescent lymphocytes, monocytes, and neutrophils spontaneously oxidized HE to EB, while DCFH was only oxidized to a low degree. Neutrophils increased 6.9-fold in EB red fluorescence and 12.5-fold in DCF green fluorescence during the respiratory burst induced by phorbol 12-myristate 13-acetate or 6.1-fold and 4.7-fold, respectively, during the respiratory burst induced by Escherichia coli bacteria. The HE or DCFH oxidation during the respiratory burst, unlike the spontaneous HE oxidation, was not inhibitable by 10 mM NaNe indicating a non-mitochondrial source of cellular oxidants during the respiratory burst such as NADPH oxidase, which produces O2-. The oxidation of DCFH, but not of HE, was decreased in stimulated neutrophils, which were simultaneously loaded with HE and DCFH. Intracellular DCFH oxidation induced by incubation of resting neutrophils with extracellular H2O2 was not influenced by the presence of HE. This indicates that HE is oxidized at an earlier step in the reactive oxygen metabolism of neutrophils than DCFH, i.e., by early oxygen metabolites like O2-, while DCFH is oxidized in part by H2O2 and phagosomal peroxidases. The differential oxidation of HE and DCFH during simultaneous cellular staining permits the analysis of up to three functionally different neutrophil populations in septic patients. This is of interest for the determination of disease-related alterations of oxygen metabolism in quiescent and stimulated leukocytes.

Journal ArticleDOI
06 Sep 1990-Nature
TL;DR: It is shown that LTD can occur in neurons of slices of the rat visual cortex and that the same tetanic stimulation can induce either LTP or LTD depending on the level of depolarization of the postsynaptic neuron.
Abstract: IN the hippocampus and neocortex, high-frequency (tetanic) stimu-lation of an afferent pathway leads to long-term potentiation (LTP) of synaptic transmission1–5. In the hippocampus it has recently been shown that long-term depression (LTD) of excitatory transmission can also be induced by certain combinations of synaptic activation6,7. In most hippocampal8 and all neocortical pathways4,9–11 studied so far, the induction of LTP requires the activation of JV-methyl-D-aspartate (NMDA) receptorgated conductances. Here we report that LTD can occur in neurons of slices of the rat visual cortex and that the same tetanic stimulation can induce either LTP or LTD depending on the level of depolarization of the postsynaptic neuron. By applying intracellular current injections or pharmacological disinhibition to modify the depolarizing response of the postsynaptic neuron to tetanic stimulation, we show that the mechanisms of induction of LTD and LTP are both postsynaptic. LTD is obtained if postsynaptic depolarization exceeds a critical level but remains below a threshold related to NMDA receptorgated conductances, whereas LTP is induced if this second threshold is reached.

Journal ArticleDOI
20 Sep 1990-Nature
TL;DR: A novel, highly sensitive confocal Raman microspec-trometer for nonresonant Raman spectroscopy is developed, which makes it possible to study single cells and chromosomes with a high spatial resolution (≲1 μm3).
Abstract: Many indirect methods have been developed to study the constitution and conformation of macromolecules inside the living cell. Direct analysis by Raman spectroscopy is an ideal complement to techniques using directly labelled fluorescent probes or of indirect labelling with mono- and polyclonal antibodies. The high information content of Raman spectra can characterize biological macromolecules both in solution and in crystals. The positions, intensities and linewidths of the Raman lines (corresponding to vibrational energy levels) in spectra of DNA-protein complexes yield information about the composition, secondary structure and interactions of these molecules, including the chemical microenvironment of molecular subgroups. The main drawback of the method is the low Raman scattering cross-section of biological macromolecules, which until now has prohibited studies at the level of the single cell with the exception of (salmon) sperm heads, in which the DNA is condensed to an exceptionally high degree. Ultraviolet-resonance Raman spectroscopy has been used to obtain single cell spectra (and F. Sureau and P. Y. Turpin, personal communication), but in this method absorption of laser light may impair the integrity of the sample. We have avoided this problem in developing a novel, highly sensitive confocal Raman microspectrometer for nonresonant Raman spectroscopy. Our instrument makes it possible to study single cells and chromosomes with a high spatial resolution (approximately less than 1 micron 3).

Journal ArticleDOI
31 May 1990-Nature
TL;DR: To determine whether the vulnerability of motor neurons to axotomy in the early postnatal phase is due to insufficient availability of ciliary neurotrophic factor, transected the axons of newborn rat motor neurons and demonstrated that local application of CNTF prevents the degeneration of the corresponding cell bodies.
Abstract: THE period of natural cell death in the development of rodent motor neurons is followed by a period of sensitivity to axonal injury1-3. In the rat this early postnatal period of vulnerability coincides with that of very low ciliary neurotrophic factor (CNTF) levels in the sciatic nerve before CNTF increases to the high, adult levels4. The developmental time course of CNTF expression, its regional tissue distribution and its cytosolic localization (as suggested by its primary structure)4,5 favour a role for CNTF as a lesion factor rather than a target-derived neurotrophic molecule like nerve growth factor. Nevertheless CNTF exhibits neurotrophic activity in vitro on different populations of embryonic neurons6. To determine whether the vulnerability of motor neurons to axotomy in the early postnatal phase is due to insufficient availability of CNTF, we transected the axons of newborn rat motor neurons and demonstrated that local application of CNTF prevents the degeneration of the corresponding cell bodies.

Journal ArticleDOI
16 Nov 1990-Science
TL;DR: The isolation and molecular analysis of several homeotic genes in Antirrhinum majus provide insights into the underlying molecular regulatory mechanisms of flower development.
Abstract: Homeotic mutants have been useful for the study of animal development. Such mutants are also known in plants. The isolation and molecular analysis of several homeotic genes in Antirrhinum majus provide insights into the underlying molecular regulatory mechanisms of flower development. A model is presented of how the characteristic sequential pattern of developing organs, comprising the flower, is established in the process of morphogenesis.

Journal ArticleDOI
15 Nov 1990-Nature
TL;DR: It is shown that naturally processed viral peptides can be extracted from virus-infected cells by acid elution, both smaller than the corresponding synthetic peptides, which have first been used to determine the respective CTL epitopes.
Abstract: Virus-infected cells can be eliminated by cytotoxic T lymphocytes (CTL), which recognize virus-derived peptides bound to major histocompatibility complex (MHC) class I molecules on the cell surface. Until now, this notion has relied on overwhelming but indirect evidence, as the existence of naturally processed viral peptides has not been previously reported. Here we show that such peptides can be extracted from virus-infected cells by acid elution. Both the naturally processed H-2-Db-restricted and H-2-Kd-restricted peptides from influenza nucleoprotein are smaller than the corresponding synthetic peptides, which have first been used to determine the respective CTL epitopes. As with minor histocompatibility antigens, occurrence of viral peptides seems to be heavily dependent on MHC class I molecules, because infected H-2d cells do not contain the H-2-Db-restricted peptide, and infected H-2b cells do not contain the H-2-Kd-restricted peptide. Our data provide direct experimental proof for the above notion on MHC-associated viral peptides on virus-infected cells.