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  • Articles  (21)
  • Animals  (12)
  • Life and Medical Sciences  (9)
  • 1990-1994  (21)
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  • Articles  (21)
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  • 1
    Publication Date: 1992-03-20
    Description: The highly symmetric pyruvate dehydrogenase multienzyme complexes have molecular masses ranging from 5 to 10 million daltons. They consist of numerous copies of three different enzymes: pyruvate dehydrogenase, dihydrolipoyl transacetylase, and lipoamide dehydrogenase. The three-dimensional crystal structure of the catalytic domain of Azotobacter vinelandii dihydrolipoyl transacetylase has been determined at 2.6 angstrom (A) resolution. Eight trimers assemble as a hollow truncated cube with an edge of 125 A, forming the core of the multienzyme complex. Coenzyme A must enter the 29 A long active site channel from the inside of the cube, and lipoamide must enter from the outside. The trimer of the catalytic domain of dihydrolipoyl transacetylase has a topology identical to chloramphenicol acetyl transferase. The atomic structure of the 24-subunit cube core provides a framework for understanding all pyruvate dehydrogenase and related multienzyme complexes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mattevi, A -- Obmolova, G -- Schulze, E -- Kalk, K H -- Westphal, A H -- de Kok, A -- Hol, W G -- New York, N.Y. -- Science. 1992 Mar 20;255(5051):1544-50.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of Groningen, The Netherlands.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1549782" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Azotobacter vinelandii/enzymology ; Chloramphenicol O-Acetyltransferase/genetics ; Humans ; Models, Molecular ; Molecular Sequence Data ; Molecular Structure ; Pyruvate Dehydrogenase Complex/*chemistry/genetics ; Sequence Homology, Nucleic Acid
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 1990-09-07
    Description: A protein crystal structure is usually described by one single structure, which largely omits the dynamical behavior of the molecule. A molecular dynamics method with a time-averaged crystallographic restraint was used to overcome this limitation. This method yields an ensemble of structures in which all possible thermal motions are allowed, that is, in additional to isotropic distributions, anisotropic and anharmonic positional distributions occur as well. In the case of bovine pancreatic phospholipase A2, this description markedly improves agreement with the observed x-ray diffraction data compared to the results of the classical one-model structure description. Time-averaged crystallographically restrained molecular dynamics reveals large mobilities in the loops involved in lipid bilayer association.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gros, P -- van Gunsteren, W F -- Hol, W G -- New York, N.Y. -- Science. 1990 Sep 7;249(4973):1149-52.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉BIOSON Research Institute, University of Groningen, The Netherlands.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2396108" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cattle ; Crystallography ; Hot Temperature ; Models, Molecular ; Motion ; *Phospholipases ; *Phospholipases A ; Phospholipases A2 ; Protein Conformation ; X-Ray Diffraction
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 1990-04-06
    Description: The epidermal growth factor (EGF) receptor (EGFR) can efficiently couple with mitogenic signaling pathways when it is transfected into interleukin-3 (IL-3)-dependent 32D hematopoietic cells. When expression vectors for erbB-2, which is structurally related to EGFR, or its truncated counterpart, delta NerbB-2, were introduced into 32D cells, neither was capable of inducing proliferation. This was despite overexpression and constitutive tyrosine kinase activity of their products at levels associated with potent transformation of fibroblast target cells. Thus, EGFR and erbB-2 couple with distinct mitogenic signaling pathways. The region responsible for the specificity of intracellular signal transduction was localized to a 270-amino acid stretch encompassing their respective tyrosine kinase domains. Thus, tissue- or cell-specific regulation of growth factor receptor signaling can occur at a point after the initial interaction of growth factor with receptor. Such specificity in signal transduction may account for the selection of certain oncogenes in some malignancies.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Di Fiore, P P -- Segatto, O -- Taylor, W G -- Aaronson, S A -- Pierce, J H -- New York, N.Y. -- Science. 1990 Apr 6;248(4951):79-83.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2181668" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Base Sequence ; Cell Division ; Cell Line ; DNA/genetics ; DNA, Recombinant ; Fibroblasts/cytology/metabolism ; Gene Expression ; Genetic Vectors ; Hematopoietic Stem Cells/cytology/metabolism ; Immunoblotting ; Mice ; *Mitogens ; Molecular Sequence Data ; Protein-Tyrosine Kinases/genetics/*physiology ; Proto-Oncogene Proteins/genetics/*physiology ; Receptor, Epidermal Growth Factor/genetics/*physiology ; Sequence Homology, Nucleic Acid ; Signal Transduction ; Transfection
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 1994-01-28
    Description: As changes in synaptic strength are thought to be critical for learning and memory, it would be useful to monitor the activity of individual identified synapses on mammalian central neurons. Calcium imaging of cortical neurons grown in primary culture was used to visualize the activation of individual postsynaptic elements by miniature excitatory synaptic currents elicited by spontaneous quantal release. This approach revealed that the probability of spontaneous activity differed among synapses on the same dendrite. Furthermore, synapses that undergo changes in activity induced by glutamate or phorbol ester treatment were identified.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Murphy, T H -- Baraban, J M -- Wier, W G -- Blatter, L A -- New York, N.Y. -- Science. 1994 Jan 28;263(5146):529-32.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7904774" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Calcium/*metabolism ; Cells, Cultured ; Cerebral Cortex ; Dendrites/*metabolism ; Glutamates/pharmacology ; Glutamic Acid ; Kinetics ; Microelectrodes ; Neuronal Plasticity ; Neurons/*physiology ; Phorbol Esters/pharmacology ; Rats ; Receptors, N-Methyl-D-Aspartate/physiology ; Synapses/*physiology ; *Synaptic Transmission ; Tetrodotoxin/pharmacology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 1994-05-20
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Broder, C C -- Nussbaum, O -- Gutheil, W G -- Bachovchin, W W -- Berger, E A -- New York, N.Y. -- Science. 1994 May 20;264(5162):1156-9; author reply 1162-5.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7909959" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Antigens, CD4/*physiology ; Antigens, Differentiation, T-Lymphocyte/*physiology ; Base Sequence ; *Cell Fusion ; Cell Line ; Dipeptidyl Peptidase 4 ; Gene Products, env/*physiology ; Giant Cells/physiology ; HIV-1/*physiology ; Humans ; Hybrid Cells ; Molecular Sequence Data
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
    Publication Date: 1993-05-28
    Description: The retinoblastoma gene product (Rb) is a nuclear phosphoprotein that regulates cell cycle progression. Elf-1 is a lymphoid-specific Ets transcription factor that regulates inducible gene expression during T cell activation. In this report, it is demonstrated that Elf-1 contains a sequence motif that is highly related to the Rb binding sites of several viral oncoproteins and binds to the pocket region of Rb both in vitro and in vivo. Elf-1 binds exclusively to the underphosphorylated form of Rb and fails to bind to Rb mutants derived from patients with retinoblastoma. Co-immunoprecipitation experiments demonstrated an association between Elf-1 and Rb in resting normal human T cells. After T cell activation, the phosphorylation of Rb results in the release of Elf-1, which is correlated temporally with the activation of Elf-1-mediated transcription. Overexpression of a phosphorylation-defective form of Rb inhibited Elf-1-dependent transcription during T cell activation. These results demonstrate that Rb interacts specifically with a lineage-restricted Ets transcription factor. This regulated interaction may be important for the coordination of lineage-specific effector functions such as lymphokine production with cell cycle progression in activated T cells.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wang, C Y -- Petryniak, B -- Thompson, C B -- Kaelin, W G -- Leiden, J M -- R01 AI29673-01/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 1993 May 28;260(5112):1330-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Medicine, University of Chicago, IL 60637.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8493578" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Base Sequence ; Binding Sites ; Cell Cycle ; Cell Line ; DNA-Binding Proteins/chemistry/*metabolism ; Eye Neoplasms/genetics ; Humans ; Lymphocyte Activation ; Molecular Sequence Data ; Mutation ; Oligodeoxyribonucleotides ; Phosphorylation ; Recombinant Fusion Proteins/metabolism ; Retinoblastoma/genetics ; Retinoblastoma Protein/*metabolism ; T-Lymphocytes/immunology/*metabolism ; Transcription Factors/chemistry/*metabolism ; Transcription, Genetic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 204 (1990), S. 177-196 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This light and transmission electron microscopical study shows that the first polar body is given off before ovulation and that part of its cell membrane and that of the surrounding oocyte have long microvilli at the time of its ejection. Several layers of cumulus cells initially surround the secondary oocyte and first polar body, but the ovulated oocytes in the oviducts in the process of being fertilized do not have cumulus cells around them. Partly expelled second polar bodies occur in the oviduct; they are elongated structures that lack organelles and have electron-dense nuclei. A small fertilization cone appears to form around the sperm tail at the time of sperm entry into the egg and an incorporation cone develops around the sperm head in the egg cytoplasm. In three fertilized eggs a small hole was seen in the zona, which was presumably formed by the spermatozoon during penetration. Cortical granules, present in ovarian oocytes, are not seen in fertilized tubal or uterine eggs; release of their contents probably reduces the chances of polyspermy, although at least one polyspermic fertilized egg was seen and several other fertilized eggs had spermatozoa within the zona pellucida. In the zygote the pronuclei come to lie close together, but there was no evidence of fusion. A “yolk mass,” which becomes eccentric before ovulation, is extruded by the time the two-cell embryos are formed, but many vacuoles remain in the non-yolky pole of the egg. A shell membrane of variable thickness is present around all uterine eggs but its origin remains undetermined.
    Additional Material: 51 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 32 (1992), S. 277-292 
    ISSN: 1040-452X
    Keywords: Oocyte maturation ; Sperm - egg interaction ; Sperm incorporation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Various morphological aspects of in vivo egg maturation and sperm - egg interaction were investigated in the Australian marsupial Sminthopsis crassicaudata with the transmission and scanning electron microscopes. Cortical granules invariably occurred in primary oocytes, with the number increasing after resumption of the first meiotic division. They generally occurred close to the oolemma, including the region near the oocyte nucleus. After mating, spermatozoa with intact acrosomes, which had a homogeneous electron-dense matrix, were found on the outer zona surface, but loss of acrosomal contents had occurred by the time of zona penetration. Sperm incorporation into the egg took place at the metaphase II stage of meiosis, and, at this time, cortical granules disappeared from the egg cortex. Sperm heads with condensed chromatin in the egg cytoplasm had an electron-dense layer of subacrosomal material over part of the dorsal nuclear surface, but no membranes were present around these incorporated spermatozoa. Sperm chromatin decondensation resulted in an elevation of egg cytoplasm, and the cell membrane over this area lacked microvilli. The pronuclear envelope was not laid down until after chromatin decondensation had occurred. By this time the fertilized egg had reached the uterus, and a smooth, electron-dense, shell membrane had been deposited. These observations, together with our previous findings, indicate that some of the processes of sperm - egg interaction are similar to those in eutherian mammals, whereas others appear highly divergent.
    Additional Material: 47 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 37 (1994), S. 78-86 
    ISSN: 1040-452X
    Keywords: Marsupial ; Sperm head ; Chromatin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The organization of sperm chromatin in the dasyurid marsupial, Sminthopsis crassicaudata, was investigated using various morphological techniques. Transmission electron microscopy indicates two quite distinct chromatin regions became evident late in spermiogenesis with an outer globular region containing blocks of very electron-dense chromatin. Fluorescent light microscopical studies after staining with DNA dyes and 7-amino actinomycin D of testicular, caput, and cauda epididymal spermatozoa showed that this region fluoresced less brightly than the rest of the nucleus, indicating the presence of fewer DNA binding sites. Freeze fracture showed that the chromatin in most of the nucleus had randomly arranged particles of various sizes, but that of the outer region was composed entirely of small particles. This outer region was more resistant to low concentrations of the ionic detergent, SDS, whereas both guanidine hydrochloride and urea together with sodium chloride generally dispersed all the chromatin except that in the outer globular region and in a localized area of the nucleus beneath the acrosome. This study has thus revealed that the outer globular chromatin of these spermatozoa responds differently to ionic detergents and protein denaturing agents and has a different chromatin organization than most of the rest of the nucleus. The significance of these differences remains, however, to be determined. © 1994 Wiley-Liss, Inc.
    Additional Material: 23 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 30 (1991), S. 369-384 
    ISSN: 1040-452X
    Keywords: F-actin ; Sperm head ; Australian rodents ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The distribution of filamentous actin around the maturing sperm head and in spermatozoa of four species of Australian conilurine rodents was investigated at the light and electron microscopic levels. Similar results were obtained for all the species studied. Mechanically isolated spermatids had NBD-phallacidin-positive longitudinal bands of fluorescence over the dorsolateral surface and, in late spermatids, bands of bright fluorescence passed perpendicularly from the dorsal convex to ventral concave surface. TEM observations indicated that these regions corresponded to filaments of ectoplasmic specializations and granular filamentous material around the tubulobulbar complexes, respectively. In testicular and cauda spermatozoa NBD-phallacidin fluorescent material was present in the two ventral processes that extended from the upper concave surface of the sperm head; also fainter material occurred along the concave border and as a dorsocaudal spur. Its distribution was identical for testicular and cauda spermatozoa. TEM of late spermatids showed that in the ventral process closest to the apical hook there were between 170 and 245 filaments, which attached to the inner surface of the postacrosomal dense lamina; in the more caudal ventral process about 70 filaments occurred. No filaments were, however, visible in the mature spermatozoon but, after immunocytochemical labelling for actin, deposition of gold particles was evident over ventral processes of both late spermatids and cauda spermatozoa. Within the female tract these ventral processes made contact with the zona matrix and were taken into the egg cytoplasm unchanged in morphology. The possible functional significance of the filamentous actin in these structures is discussed.
    Additional Material: 39 Ill.
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