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  • 1985-1989  (6,772)
  • 1955-1959  (1,467)
  • 1930-1934  (1,172)
  • 1890-1899  (195)
  • Cell & Developmental Biology  (9,525)
  • gene expression
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 45 (1989), S. 526-535 
    ISSN: 1420-9071
    Keywords: Interferon ; cytokines ; interleukins ; gene expression ; transcription ; autoimmune ; disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Specific interferon genes are transcribed at low levels in the spleen, liver, and peripheral blood leukocytes of normal individuals in the apparent absence of virus infection while other interferon genes remain unexpressed in the same tissues. In contrast, the genes of cytokines such as IL-1, IL-6 and TNF are expressed at relatively high levels in the organs of normal individuals. The level of expression of the IL-1, IL-6 and TNF genes is markedly reduced in the livers of patients with autoimmune liver disease compared to the level of expression in the liver of normal individuals, whereas the expression of interferon genes is similar in both normal and diseased liver, suggesting that a defect in the expression of specific cytokines is associated with severe liver disease.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-994X
    Keywords: BAL31 nuclease ; CAT assay ; gene expression ; HTLV-I ; R region ; 5′ untranslated sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We previously demonstrated the activity of the R fragment in the long terminal repeat of human T-cell leukemia virus type I for elevation of the level of gene expression. In this study, the fragment was deleted with BAL31 nuclease to determine its functional domain. Series of the shortened R fragments were linked to the simian virus 40 promoter unit, which regulated expression of a reporter gene. Examination with the R fragments deleted from the 5′ and 3′ ends showed that borders of the functional domain were mapped within nucleotide positions 458 to 473 for the 5′ end and nucleotide positions 559 to 594 for the 3′ end, respectively. Thus we conclude that a 136-base-pair fragment corresponding to the second half of the R region was sufficient to allow elevation of the level of gene expression.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of experimental biology and medicine 108 (1989), S. 999-1001 
    ISSN: 1573-8221
    Keywords: brain ; gene expression ; mRNA ; transplantable hepatomas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-4927
    Keywords: mouse ; salivary protein ; lacrimal protein ; gene expression ; Spt locus ; multigene family
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The murine submandibular gland (SMG) produces a novel class of highly acidic salivary proteins encoded by one or more highly abundant mRNA transcripts. In inbred mice, these transcripts are encoded by members of a multigene family comprising approximately 8–12 homologues. Most, and probably all, of these homologues are clustered at a new locus near belted (bt) on chromosome 15, which we designateSpt (salivary protein). Although physically closely linked,Spt genes differ in their patterns of expression both in strains of mice and in their tissues. One gene,Spt-1, is expressed at high levels in the SMG of all inbred strains examined. This gene is also expressed at significant levels in the lacrimal gland. A second gene,Spt-2, appears to be present as a single copy in some strains and as two copies in others. This gene is expressed at high levels only in the SMG of those strains carrying two copies, andSpt-2 mRNA is not detectable in the SMG of strains carrying only one copy. In contrast toSpt-1, theSpt-2 gene is not expressed at detectable levels in the lacrimal gland.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-4927
    Keywords: mouse ; salivary protein ; lacrimal protein ; gene expression ; Spt locus ; multigene family
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The murine submandibular gland (SMG) produces a novel class of highly acidic salivary proteins encoded by one or more highly abundant mRNA transcripts. In inbred mice, these transcripts are encoded by members of a multigene family comprising approximately 8–12 homologues. Most, and probably all, of these homologues are clustered at a new locus near belted (bt) on chromosome 15, which we designateSpt (salivary protein). Although physically closely linked,Spt genes differ in their patterns of expression both in strains of mice and in their tissues. One gene,Spt-1, is expressed at high levels in the SMG of all inbred strains examined. This gene is also expressed at significant levels in the lacrimal gland. A second gene,Spt-2, appears to be present as a single copy in some strains and as two copies in others. This gene is expressed at high levels only in the SMG of those strains carrying two copies, andSpt-2 mRNA is not detectable in the SMG of strains carrying only one copy. In contrast toSpt-1, theSpt-2 gene is not expressed at detectable levels in the lacrimal gland.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular neurobiology 9 (1989), S. 281-294 
    ISSN: 1573-6830
    Keywords: cholecystokinin ; mammillary region ; development ; gene expression ; hybridization histochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. The ontogeny and adult distribution of neurons containing cholecystokinin (CCK) mRNA in the premammillary and mammillary nuclei and supramammillary region of the rat brain were studied using hybridization histochemistry. 2. The earliest detection of CCK mRNA in the mammillary region was on E14, followed by a marked increase in transcript levels during the next 4 days, a time during which neurons in this region still divide. During the first 2 weeks of life, few changes in the levels of CCK transcripts were seen, and an adult-like pattern of expression was seen on the twenty-first day of life. 3. Low levels of transcripts were present in numerous neurons located in all divisions of the medial nucleus and in the posterior nucleus known to project ipsilaterally to the anteroventral and anteromedial thalamic nuclei. In contrast, none of the neurons in the lateral nucleus (projecting bilaterally to the anterodorsal thalamic nucleus) had detectable transcripts. 4. Many neurons in the supramammillary nucleus had low, moderate, or high levels of transcripts. Some nearby nuclei (such as the dorsal premammillary nucleus) had smaller numbers of neurons with low levels of CCK mRNA, whereas others (such as the ventral premammillary nucleus) had none.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 12 (1989), S. 295-299 
    ISSN: 1573-5028
    Keywords: gene expression ; multiple transcripts ; phytochrome ; Pisum sativum ; red/far-red reversible effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The reversible effect of red and far-red light on the level of two RNA transcripts of the single-copy phytochrome gene in pea was investigated using the primer extension assay. In dark-grown seedlings, a brief irradiation with red light markedly reduced the level of one of the phytochrome transcripts, RNA1. This red light effect was reversed by subsequent irradiation with far-red light. The other phytochrome transcript, RNA2, was only slightly influenced by light. In light-grown seedlings, a brief irradiation with far-red light increased the content of both RNA1 and RNA2 when the seedlings were transferred from light to darkness. This far-red light effect was reversible by subsequent red light irradiation.
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  • 8
    ISSN: 1573-5028
    Keywords: antisense RNA ; β-glucuronidase ; tobacco ; transgenic plants ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Antisense RNA was used to specifically inhibit the expression of a GUS gene introduced in a transgenic plant. A tobacco transformant containing a single intact copy of the GUS gene and showing relatively high constitutive levels of GUS activity (GUS+) was re-transformed with an Agrobacterium Ti-derived binary vector containing an antisense version of this reporter gene. The sense and antisense GUS genes were each under the regulation of the CaMV 35S promoter. Re-transformed plants contained 1–5 copies of the antisense construct and all showed a greater than 90% reduction in GUS activity relative to the original GUS+ plant. This reduction in GUS activity correlated closely with the levels of GUS enzyme and steady state GUS mRNA observed in these plants. The relatively low levels of sense and antisense GUS transcripts found in the re-transformed plants may indicate a rapid degradation of the RNA:RNA duplex in the cell.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-4919
    Keywords: complement ; factor B ; gene expression ; interferon-ψ ; interleukin-1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The serine protease complement factor B (Bf), an acute phase plasma protein, is a component of the alternative pathway of complement activation. Previous studies revealed that several cytokines including IFN-γ and IL-1 are involved in mediating acute phase Bf expression. To determine the molecular details of Bf expression we isolated, sequenced and characterized the 5′ flanking regions of the human and murine Bf genes. In both species the Bf transcriptional start site in liver was located 〈400 by 3′ to the polyadenylation site of the upstream C2 gene. This upstream intergenic region contained 〉65% nucleotide homology between species. Within this region, an IRS and three heat shock consensus elements were found in the murine sequence in an identical position to that of the human. To examine the functional details of Bf expression, a series of mouse and human Bf promoter - chloramphenicol acetyltransferase (CAT) chimeric gene constructs were transfected into mouse L or human HepG2 cells. Analysis of expression of these fusion gene constructs revealed that 1) cis-acting DNA sequences identified, at least in part, in the 3′ untranslated region of the C2 gene (within the 400 by upstream of the Bf cap site) mediate responsiveness to IL-1 and IFN-γ, 2) the responsiveness to each mediator appears to be conferred by separate upstream regions similar in position and homologous in man and mouse, and 3) the IL-1 responsive region in both species appears to have the characteristics of an enhancer element. The results of this analysis suggest a selective pressure to conserve the intergenic sequence between C2 and Bf genes and that further studies of these sequences will be useful in elucidating mechanisms controlling the acute phase response.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Bioscience reports 9 (1989), S. 157-188 
    ISSN: 1573-4935
    Keywords: matrix hypothesis ; morphogenesis ; protodynamics ; growth control ; DNA ; genome organisation ; gene expression ; gene regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A theoretical concept is proposed, in order to explain some enigmatic aspects of cellular and molecular biology of eukaryotic organisms. Among these are the C-value paradox of DNA redundancy, the correlation of DNA content and cell size, the disruption of genes at DNA level, the “Chromosome field” data of Lima de Faria (Hereditas 93∶1, 1980), the “quantal mitosis” proposition of Holtzeret al. (Curr. Top. Dev. Biol. 7∶229 1972), the inheritance of morphological patterns, the relations of DNA and chromosome organisation to cellular structure and function, the molecular basis of speciation, etc. The basic proposition of the “Unified Matrix Hypothesis” is that the nuclear DNA has a direct morphogenic function, in addition to its coding function in protein synthesis. This additional genetic information is thought to be largely contained in the non-protein coding transcribed DNA, and in the untranscribed part of the genome.
    Type of Medium: Electronic Resource
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  • 11
    ISSN: 1573-5028
    Keywords: cadmium ; Datura innoxia ; gene expression ; heat shock ; tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of Cd on gene expression in suspension cultures of twoDatura innoxia cell lines with differing Cd tolerance was studied.In vivo labeling experiments using [3H] leucine showed that Cd induced the synthesis of a similar range of proteins in both cell lines at a concentration which will kill the sensitive but not the tolerant cells. Corresponding changes in levels of translatable mRNA were also observed. The induction of the synthesis of proteins by Cd was transient since Cd-tolerant cells growing continuously in 250 μM CdCl2 contained a similar set ofin vitro translation products to cells growing in the absence of Cd. Although Cd had a similar effect on gene expression in both cell lines, Cd-tolerant cells possess two abundant mRNAs which are constitutively produced. These mRNAs encode proteins of low molecular weight (about 11 kDa) and are either absent or present at a low level in Cd-sensitive cells. The functions of these proteins are not known but they may be involved in the tolerance mechanism. Two-dimensional gel electrophoresis ofin vitro translation products showed that many of the Cd-induced proteins are also induced by heat shock. A 42°C heat shock resulted in agreater range and more intense induction of translatable mRNAs than 4 h exposure to 250 μM CdCl2. However a subset of mRNAs were induced specifically by Cd while other mRNAs were heat shock-specific. There was no difference in the ability of the two cell lines to tolerate heat shock. This was also reflected by the same pattern of major proteins induced by heat shock in the two cell lines.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 12 (1989), S. 667-672 
    ISSN: 1573-5028
    Keywords: ferredoxin ; gene expression ; heterocyst ; Anabaena 7120 ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The genes for ferredoxin from heterocysts (fdx H) and vegetative cells (pet F) of Anabaena sp. strain 7120 were subcloned into plasmid pUC 18/19. Both genes were expressed in Escherichia coli at high levels (≈10% of total protein). Pet F could be expressed from its own promoter. The ferredoxins were correctly assembled to the holoprotein. Heterocyst ferredoxin was purified from E. coli extracts on a large scale. Its biochemical and biophysical properties were identical to those of the authentic ferredoxin, isolated from Anabaena heterocysts.
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  • 13
    ISSN: 1573-5028
    Keywords: acyl carrier protein ; fatty acid synthesis ; gene expression ; gene fusion ; protein A ; spinach
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A synthetic gene encoding spinach acyl carrier protein I (ACP-I) was fused to a gene encoding the Fc-binding portion of staphylococcal protein A. This gene fusion, under the control of the λPR promoter, was expressed at high levels in Escherichia coli producing a 42 kDa fusion protein. This fusion protein was phosphopantethenylated in E. coli. In vitro the ACP portion of the fusion protein was able to participate in acyl ACP synthetase reactions, plant malonyl-CoA:ACP transacylase (MCT) reactions, and plant fatty acid synthetase (FAS) reactions. Inhibitory effects of high ACP concentrations on in vitro plant FAS were observed with the unfused ACP-1 but not with the fusion protein. As with unfused ACP-I, the fusion protein was a poor substrate for E. coli FAS reactions. When injected into rabbits, the fusion protein was also able to generate antiserum to spinach ACP-I.
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  • 14
    ISSN: 1573-5028
    Keywords: cDNA sequence ; gene expression ; glutamine synthetase ; legume-Rhizobium symbiosis ; nitrogen metabolism ; Phaseolus vulgaris L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We report the sequence of an essentially full-length glutamine synthetase (GS) cDNA clone (pcGS-γ1) isolated from a root nodule library ofPhaseolus vulgaris L. The polypeptide encoded by this cDNA has been producedin vitro by transcription/translation and shown to co-migrate on two-dimensional gels with the previously identified major cytosolic GS polypeptide (γ) of nodules. Two previously identified GS cDNA clones, pR-2 and pR-1 (see Gebhardtet al., EMBO J 5: 1429–1435, 1986) have similarly been shown to encode the α and β cytosolic GS polypeptides respectively. An RNase protection technique has been used to analyse specifically and quantitatively the abundance of mRNA related to these three GS cDNAs and to the cDNA (pcGS-δ1) encoding the chloroplast-located GS, during nodulation. Differences in the abundances of these mRNAs at different times suggest that they are not coordinately regulated. Moreover, using this technique mRNA specifically related to pcGS-γ1 was found at high levels in nodules but not in roots or leaves. Surprisingly the expression of this gene is not nodule-specific as previously suggested, as its mRNA was also detected, but at lower levels, in stems, petioles and in green cotyledons. By comparison, mRNA related to a leghaemoglobin gene was detected only in nodules. Comparisons of the relative abundances of the pcGS-γ1 mRNA and the γ polypeptide in different organs and at different stages during nodulation, suggest that the appearance of the γ polypeptide is largely under transcriptional control.
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  • 15
    ISSN: 1573-5028
    Keywords: differential cDNA screening ; gene expression ; hybrid-select in vitro translation ; nuclear run-off transcription ; RNA blot hybridization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A cDNA library from cultured parsley (Petroselinum crispum) cells was differentially screened using labeled run-off transcripts derived from nucleic of elicitor-treated and untreated cells. This resulted in the isolation of 18 independent cDNA families representing putative defense-related genes. All genes are rapidly and transiently activated after elicitor application, but the time courses of transcriptional activity exhibit considerable variations, indicating differences in the mechanisms of gene regulation.
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  • 16
    ISSN: 1573-5028
    Keywords: deformation factor ; gene expression ; pea ; Rhizobium leguminosarum ; root hairs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mRNA population in pea root hairs was characterized by means of in vitro translation of total root hair RNA followed by 2-dimensional gel electrophoresis of the translation products. Root hairs contain several mRNAs not detectable in total RNA preparations from roots. Most of these root hair-specific mRNAs occur in elongating root hairs at higher levels than in mature root hairs. The expression of some genes in pea root hairs is typically affected by inoculation with Rhizobium leguminosarum. One gene, encoding RH-42, is specifically induced while the expression of another gene, encoding RH-44, is markedly enhanced. Using R. leguminosarum mutants it was shown that the nodC gene is required for the induction and enhancement of expression of the RH-42 and RH-44 genes, respectively, while the Rhizobium chromosomal gene pss1, involved in exopolysaccharide synthesis, is not essential. After induction of the nod genes with apigenin the bacteria excrete into the culture medium a factor that causes root hair deformation. This deformation factor stimulates the expression of the RH-44 gene but does not induce the expression of the gene encoding RH-42.
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  • 17
    ISSN: 1573-5028
    Keywords: C4 photosynthesis ; gene structure ; gene expression ; genetic variation ; silent substitution ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have determined the structure of the maize (Zea mays L. subsp.mays line B73) nuclear gene encoding the phosphoenolpyruvate (PEP) carboxylase isozyme involved in C4 photosynthesis. The gene is 5.3 kb long and has ten exons that range in size from 85 to 999 bp. The nine introns vary from 97 to 872 bp. The sequence of 663 bp of 5′-flanking and 205 bp of 3′-flanking DNA is reported along with the entire gene sequence. Several short repetitive sequences were found in the 5′-flanking DNA that have characteristics similar to elements important in the light regulation of pea genes encoding the small subunit of ribulose 1,5-bisphosphate carboxylase. In addition, some 5′-flanking sequence similarities were found in a comparison with other light-regulated genes from maize and wheat. The level of DNA sequence variation among different PEP carboxylase alleles is similar to the allelic variation observed for several other maize nuclear genes. The data suggest modern maize variaties have retained much of the genetic variation present in their ancestral forms. Finally, accumulation of transcripts encoding the PEP carboxylase isozyme involved in C4 photosynthesis is quite high in several structures besides leaves, including inner leaf sheaths, tassels and husks. This indicates that expression of this gene is not leaf-specific and may not necessarily be coupled to the development of Kranz anatomy.
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 12 (1989), S. 673-682 
    ISSN: 1573-5028
    Keywords: amylase inhibitor ; barley ; cDNA sequence ; gene expression ; hormonal regulation ; protease inhibitor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have cloned and sequenced a full-length cDNA from barley (Hordeum vulgare L.) seeds encoding the bifunctional α-amylase/subtilisin inhibitor (BASI). The nucleotide sequence predicts an open reading frame coding for a protein of 203 amino acids. The first 22 amino acids exhibit the sequence characteristic of a signal peptide, as found in several other plant protease inhibitors. Northern blot hybridization experiments indicate that BASI mRNA accumulation is strictly tissue-specific and is developmentally programmed. BASI mRNA transcripts were only identified in 1) developing starchy endosperm tissue from 14 days after flowering and 2) aleurone tissue of germinating seeds. In this latter tissue, BASI mRNA accumulation is enhanced by abscisic acid and abolished by gibberellic acid. Expression of BASI mRNA was also studied in the lys 3a high-lysine barley mutants Risø No. 1508 and Piggy. These high-lysine barleys show 2–4-fold higher levels as well as prolonged accumulation of BASI mRNA compared to the normal motherline Bomi. This correlates with the increased deposition of BASI protein in lys 3a barley mutants. Genomic blot analysis of barley DNA suggests that there are one or two BASI structural genes per haploid genome. Possible roles of BASI as part of a defence mechanism against precocious germination and pathogens are discussed.
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  • 19
    ISSN: 1573-5028
    Keywords: cDNA ; gene expression ; hydroxypyruvate reductase ; light regulation ; peroxisomal enzyme
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A full-length cDNA encoding NADH-dependent hydroxypyruvate reductase (HPR), a photorespiratory enzyme localized in leaf peroxisomes, was isolated from a λgt11 cDNA library made by reverse transcription of poly(A)+ RNA from cucumber cotyledons. In vitro transcription and translation of this clone yielded a major polypeptide which was identical in size, 43 kDA, to the product of in vitro translation of cotyledonary poly(A)+ RNA and subsequent immunoprecipitation with HPR antiserum. Escherichia coli cultures transformed with a plasmid construct containing the cDNA insert were induced to express HPR enzyme activity. RNA blot analysis showed that HPR transcript levels rise significantly in the first eight days of light-grown seedling development. This closely resembles the pattern seen for HPR-specific translatable mRNA. DNA blot analysis indicated that a single HPR gene is likely present per haploid genome. Nucleotide sequence analysis revealed an open reading frame of 1146 bases which encodes a polypeptide with a calculated molecular weight of 41.7 kDa. The derived amino acid sequence from this open reading frame is 26% identical and 50% similar to the amino acid sequence of the E. coli enzyme phosphoglycerate dehydrogenase, which catalyzes a similar reaction and functions in a related pathway. Statistical analyses show that this similarity is significant (z〉10). The derived amino acid sequence for HPR also contains the characteristics of an NAD-binding domain.
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  • 20
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 12 (1989) 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 21
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 12 (1989), S. 78-89 
    ISSN: 0886-1544
    Keywords: mitosis ; actin and myosin ; agar-overlay method ; immunofluorescence ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Synchronized cultures of Dictyostelium discoideum were used to study organizational changes of the cytoskeleton during mitotic cell division. The agar-overlay technique (Yumura et al.: J. Cell Biol. 99:894-899, 1984) was employed for immunofluorescence localization and video microscopic observation of living mitotic cells. The mitotic phase was defined by changes in chromosome configuration by using a double stain with the fluorescent dye DAPI.This study showed that the actin- and myosin-containing cytoskeleton was reversibly redistributed between the cortical ectoplasm and the endoplasm during prophase and telophase. Both actin and myosin filaments were dissociated from the cell cortex in prophase. Most of the actin and myosin was filamentous and remained in the endoplasm until telophase. Saltatory movements of organelles stopped suddenly, coincident with the breakdown of the cytoplasmic microtubule network. This change in the microtubule system was temporally coupled with the disappearance of actomyosin from the cortex. At the same time, the local vibrating movement of particles almost stopped, suggesting that the viscoelastic nature of the endoplasm was altered. In the late anaphase, actin and myosin relocalized to the cortical ectoplasm. Early in this phase, myosin filaments were localized specifically at the anticipated cleavage furrow region of the cleavage furrow, whereas actin filaments were redistributed more uniformly in the cell cortex, with an extremely large accumulation in the polar pseudopods. Subsequently the actin formed an orderly parallel array of cables along with myosin filaments in the contractile ring.The spatial segregation of actin and myosin in late anaphase was clearly demonstrated by multipolar cell division of artificially induced giant cells. Actin was relocalized in both the polar and the proximal constricting regions whereas myosin was only localized in the center of each pair of daughter microtubule networks where the cleavage furrow was formed. This study demonstrates that actin and myosin are reorganized by a temporally coordinated but spatially different mechanism during cytokinesis of Dictyostelium.
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  • 22
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 12 (1989), S. 90-103 
    ISSN: 0886-1544
    Keywords: mitosis ; spindles ; microtubule-organizing centers ; antiphosphoprotein antibodies ; phosphorylation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Protein phosphorylation during development of sea urchin eggs from fertilization to first cleavage was examined by labeling cells with specific antiphosphoprotein antibodies. Indirect immunofluorescence staining with monoclonal antithiophos-phoprotein antibody (Gerhart et al.: Cytobios 43:335-347, 1985) has revealed that nuclei as well as centrosomes, kinetochores, and midbodies were specifically thiophosphorylated in developing eggs incubated with adenosine 5′-O (3-thiotriphosphate) (ATP-γ-S). The phosphorylation reaction required Mg2+ but was not dependent on cAMP or calmodulin in detergent-extracted models. Centrosomes were purified by fractionation of isolated mitotic spindles with 0.5 M KCl extraction. The thiophosphoproteins were retained in the purified centrosomes and the antibody recognized a major 225-Kd polypeptide on immunoblots. In an independent preparation, a monoclonal antiphosphoprotein antibody (CHO3) was found also to react with mitotic poles and stained a 225-Kd polypeptide, confirming the centrosome specificity of this protein. Immunoelectron microscopy showed that the 225-Kd thiophosphoprotein was found at mitotic poles associated with granules to which mitotic microtubules were directly attached. Unlike centrosomes in permeabilized eggs, those in isolated spindles could not be thiophosphorylated, possibly due to inactivation or loss of either phosphorylation enzymes or cofactors, or both, during isolation. The immunofluorescence labeling of thiophosphate could be inhibited by ATP and AMP-PNP in a concentration-dependent manner. Exogenous ATP could abolish thiophosphate-staining more effectively when added with phosphatase inhibitors, suggesting a dynamic state in which centrosomal proteins are being phosphorylated and dephosphorylated in rapid succession by the action of protein kinase(s) and phosphatase(s).
    Additional Material: 9 Ill.
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  • 23
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 13 (1989), S. 212-220 
    ISSN: 0886-1544
    Keywords: meiosis ; live observation ; oscillatory movements ; microtubule assembly-disassembly ; spindle forces ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Chromosome movements in Mesostoma ehrenbergii spermatocytes were studied using conventional video light microscopy. Kinetochore regions of the three bipolarly oriented bivalents displayed periodic back and forth movements directed to both poles at metaphase I, leading to periodic lenght changes of the bivalents. Velocity was 8-10 μm/min (maximum 17 μ/min), about one order of magnitude higher than the normal meiotic or mitotic chromosome movements of other species. One cycle of movement lasted for about 100 seconds. The movement of kinetochore regions implies that the antagonistic chromosome fibres periodically grow (assemble) and shorten (disassemble) at comparable rates. Poleward movements must be caused by forces generated in disassembling fibres, whereas movements away from the poles, accompanied by fibre growth, are probably brought about by the internal elastic force of the chromosomes. Antagonistic fibres of a bivalent can operate in or out of phase. The movements of the three kinetochore regions are coordinated insofar as growing and shortening fibres coexist in a half-spindle at almost any time [Fuge, H. (1987): European Journal of Cell Biology 44:294-298]. These observations are discussed in terms of microtubule dynamics.
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  • 24
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 13 (1989), S. 239-244 
    ISSN: 0886-1544
    Keywords: sperm ; nucleotide analog ; kinetics ; Stronglyocentrotus purpuratus ; reactivation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The 2-substituted ATP analog 2-Chloro ATP was tested for its capacity to support axonemal movement. The movement of sea urchin axonemes reactivated with 2-CI ATP appeared very similar to that with ATP. Detailed waveform analysis indicated that bend angle and shear amplitude were not significantly different for ATP and 2-CI ATP. Although wavelength differs at particular nucleotide concentrations, if normalized to the beat frequency, it is similar for ATP and 2-CI ATP. The main difference in the movement with the two analogs was seen in beat frequency and sliding velocity. The Vmax for beat frequency and mean sliding velocity was lower for 2-CI ATP. The apparent Km for beat frequency and sliding velocity was much lower for 2-CI ATP. The ratio of these two effects, that is, (Vmax/Km) is higher for 2-CI ATP. Thus 2-CI ATP is a good substrate for axonemal movement. The significantly lower Km of 2-CI ATP was also demonstrated by its ability to support oscillatory motion at concentrations below that for ATP. The observations identify the structures and conformation of substrate necessary to support axonemal movement.
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  • 25
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    Cell Motility and the Cytoskeleton 12 (1989), S. 53-65 
    ISSN: 0886-1544
    Keywords: reversible binding ; computer simulation ; transport rates ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A model for slow axonal transport is developed in which the essential features are reversible binding of cytoskeletal elements and of soluble cytosolic proteins to each other and to motile elements such as actin microfilaments. Computer simulation of the equations of the model demonstrate that the model can account for many of the features of the SCa and SCb waves observed in pulse experiments. The model also provides a unified explanation for the increase and decrease of neurofilament transport rates observed in various toxicant-induced neuropathies.
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  • 26
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    Cell Motility and the Cytoskeleton 12 (1989), S. 113-122 
    ISSN: 0886-1544
    Keywords: mitosis ; spindle ; kinetochore ; centrosome ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: To investigate the association of calmodulin (CaM) with microtubules (MTs) in the mitotic apparatus (MA), the distributions of CaM and tubulin were examined in cells in which the normal spindle organization had been altered. A fluorescent CaM conjugate with tetramethylrhodamine isothiocyanate (CaM-TRITC) and a dichlorotriazinyl aminofluorescein conjugate with tubulin (tubulin-DTAF) were injected into cells that had been treated with the MT inhibitor nocodazole. With moderate nocodazole concentration (0.3 μg/ml, 37°C, 4 h) in live cells, CaM-TRITC and tubulin-DTAF concentrated identically on or near the centrosomes and kinetochores. In serial sections of these cells, small MT segments were observed by transmission electron microscopy (TEM) in the regions where fluorescent protein had concentrated. When a higher drug concentration was used (3.0 μg/ml, 37°C, 4 h), no regions of CaM-TRITC or tubulin-DTAF localization were observed, and no MTs were observed when serial sections were examined by TEM. However, following release from the high-concentration nocodazole block, CaM-TRITC colocalized with newly formed MTs at the kinetochores and centrosomes. Later in the recovery period, when chromosome-to-pole fibers had formed, CaM association with kinetochores diminished, ultimately attaining its normal pole-proximal association with kinetochore MTs in cells that progressed through mitosis. We interpret these observations as supporting the hypothesis that in the MA, CaM attains a physical association with kinetochore MTs and suggest that CaM-associated MTs may be inherently more stable.
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  • 27
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    Cell Motility and the Cytoskeleton 12 (1989), S. 157-168 
    ISSN: 0886-1544
    Keywords: axolotl ; cell differentiation ; cell shape ; cytoskeleton ; nucleated erythrocyte ; microtubule ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The spleen of Ambystoma mexicanum (axolotl) larvae develops as a closed sac containing differentiating nucleated erythrocytes, and is typically isolated from the general circulation for about 10 days post-hatching. Beginning 3-4 days posthatching, it can be removed intact for examination of the morphology and cytoskeletal structure of the erythropoietic cells. In the smallest (earliest) spleens, spheroidal cells predominate, while older ones contain a preponderance of cells exhibiting the flattened elliptical morphology typical of all non-mammalian vertebrate erythrocytes. Most striking in the splenic erythroid population are cells with singly or doubly pointed morphology. Though common in the developing spleen and circulation of young larvae, pointed cells are less frequently encountered in the circulation of older larvae, indicating that they are intermediate stages in the differentiation of spheroids to flattened ellipsoids. This is supported by structural observations on cytoskeletons prepared from the splenic cells. Incomplete singly and doubly pointed marginal bands of microtubules are observed, many of which contain a pair of centrioles within or close to a pointed end, suggestive of organizing center function. The observations are consistent with a sequence of changes in cell morphology from spherical to doubly pointed to singly pointed to flattened ellipse, causally linked to stages of marginal band biogenesis.
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  • 28
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    Cell Motility and the Cytoskeleton 12 (1989), S. 185-194 
    ISSN: 0886-1544
    Keywords: myofibril assembly ; focal contacts ; vinculin ; α-actinin ; connectin ; immunocytochemistry ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The relationship of nascent myofibrils with the accumulation of adhesion plaque proteins and the formation of focal cell contacts was studied in embryonic chick cardiac myocytes in vitro. The cultures were double-stained with various combinations of the specific antiactin drug phalloidin and antibodies against vinculin, α-actinin, connectin (titin), myosin heavy chain, fibronectin, and desmin and examined under fluorescence and interference reflection microscopy.In the areas of myofibril assembly, vinculin and α-actinin plaques were formed at the ventral sarcolemmae. These areas overlapped with the sites of cell-to-substrate focal contacts and extracellular fibronectin. Because the myofibrils always ran in a straight line between these sites, polarized lines appeared to be generated within the cells in response to their physical (e.g., stress) and/or biochemical environment (e.g., adhesion plaque proteins). The possible presence of other factors cannot be ruled out for the proper alignment of myofibrils. As soon as myofibrils came to span between these adhesion sites, they exhibited typically mature cross-striated characteristics. Thus, the formation of these inferred lines has some relation to or is in fact necessary for the maturation of myofibrils, in addition to the directional arrangement of sarcomeric proteins.Additionally, synthesis and distribution of myosin and connectin were tightly linked during early developmental (premyofibril and myofibril) stages. The spatial deployment of desmin was not coupled with vinculin. Thus, connectin and desmin do not appear to form the initial scaffold of sarcomeres.
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  • 29
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    Cell Motility and the Cytoskeleton 12 (1989), S. 283-283 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 30
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    Cell Motility and the Cytoskeleton 12 (1989), S. 273-282 
    ISSN: 0886-1544
    Keywords: cytoskeleton ; microtubules ; axons ; sensory neurons ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The comparative distribution of tyrosinated, detyrosinated, and acetylated α-tubulins was examined in neurites of rat dorsal root ganglion neurones in culture using immunofluorescence microscopy. Phase contrast observations of single neurones revealed that the neurites were actively motile, and rhodamine phalloidin staining of actin filaments showed the extent of lamellopodia and microspike projections from the growth cones. From double-labelling experiments using antibodies against tyrosinated, detryrosinated, or acetylated α-tubulin, it was found that the three different isoforms were differentially localised in neurites and growth cones. Detyrosinated and acetylated forms of α-tubulin were in the main restricted to the neurites extending no further than the base of the growth cones. Tyrosinated α-tubulin was, however, distributed throughout the body of the growth cone and into the base of some microspikes. Following treatment with taxol to promote microtubule assembly, detyrosinated and acetylated α-tubulins were found to be colocalised with tyrosinated α-tubulins throughout the growth cones of all cells examined. These results would be consistent with axonal transport of tyrosinated α-tubulin followed by assembly in the growth cone and subsequent detyrosination and acetylation. In addition the presence of unmodified α-tubulin in the growth cone may be necessary for the provision of labile microtubules for growth cone motility and extension.
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  • 31
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    Cell Motility and the Cytoskeleton 13 (1989), S. 158-169 
    ISSN: 0886-1544
    Keywords: chemotaxis ; cAMP ; cytoskeleton ; ameba ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The distribution of myosin was studied in amebae of the Ax-3 and NC-4 strains of Dictyostelium migrating at room temperature, using indirect immunofluorescence of aggregation-competent amebae and the agar-overlay technique. Amebae were fixed in methanol-formaldehyde or absolute acetone at -15°C before or after stimulation with micromolar cyclic AMP at room temperature (20-25°C). Myosin was detected by monoclonal antibodies to Dictyostelium myosin heavy chain followed by a fluorescent secondary antibody that had been preabsorbed to remove nonspecific staining. In both strains there was a striking increase in intensity of anti-myosin immunofluorescence in the cortex where it appeared as a continuous ring 30 seconds after addition of cyclic AMP. This correlated with a rounding up of the cell body. Sixty seconds after stimulation there was a clear reduction of cytoplasmic myosin rods in conjunction with the increased cortical localization. At this time extensions of largely hyaline cytoplasm were observed that extended beyond the cortical shell of myosin. Two minutes after the stimulus the immunofluorescence remained as a distinct line at the cortex, but the cells began to resume in elongated shape. By 3 minutes (NC-4 strain) or 5 minutes (Ax-3 strain) the amebae had largely returned to the control shape, and myosin had returned to its control distribution. Counts of the treated cells at different time points substantiated the observations of individual cells. The time course of translocation of myosin in the Ax-3 strain parallels the time course of myosin phosphorylation reported in previous studies. The results are interpreted in terms of a working hypothesis for the mechanism of translocation.
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  • 32
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    Cell Motility and the Cytoskeleton 13 (1989), S. 225-238 
    ISSN: 0886-1544
    Keywords: centrosome ; DAPI ; immunofluorescence ; immunoperoxidase ; microtubules ; mitosis ; scleroderma serum ; tubulin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Double-label immunofluorescence of tubulin and preicentriolar material (PCM) was carried out with mitotic nuclei in the coenocytic green alga Ernodesmis. Spindle poles are heavily labeled with serum 5051 (anti-PCM) from midprophase through mid- to late anaphase, and bright fluorescence is also evident at the tips of the elongated interzonal spindle in telophase nuclei. Very faint labeling with anti-PCM is also detected throughout the spindle (and/or its matrix) at all mitotic stages. Control treatments demonstrated that nonspecific surface labeling of chloroplasts with anti-PCM may be due to some naturally occurring component of human sera rather than to specific labeling by the anti-PCM serum. Ultrastructural work indicates that the centrosome is always associated with spindle poles through anaphase, but not with the tips of the interzonal telophase Immunoper-oxidase electron microscopy verifies that anti-PCM labels the centrosomes of mitotic nuclei in these cells. However, labeling is also present inside the presistent nuclear envelope at the spindle poles, during metaphase, anaphase, and at the tips of the interzonal spindles. Regions of heaviest labeling correspond with amorphous material near the centrioles and at the spindle poles, as evident in conventional electron microscope preparations. The origin of intranuclear amorphous material that labels with anti-PCM is unclear, but the ends of many spindle microtubules are embedded in it, especially at anaphase, and the tips of microtubules near the amorphous material are often labeled with the antiserum. These results indicate for the first time that serum 5051 does indeed label PCM at the poles of centric spindles in plant cells. Although the location of the labeled material suggests it is associated with the nucleation of spindle microtubules, this conclusion requires more information about microtubule dynamics in these cells. Caution is also warranted in interpreting variant anti-PCM labeling patterns in other plant cells because of spurious labeling of the spindle itself and other cytoplasmic organelles.
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  • 33
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 34
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    Cell Motility and the Cytoskeleton 14 (1989), S. 92-102 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 35
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    Cell Motility and the Cytoskeleton 14 (1989), S. 163-168 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 36
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    Cell Motility and the Cytoskeleton 14 (1989) 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 37
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    Cell Motility and the Cytoskeleton 14 (1989), S. 177-177 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 38
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    Cell Motility and the Cytoskeleton 14 (1989), S. 178-182 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 39
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    Cell Motility and the Cytoskeleton 14 (1989), S. 183-186 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 40
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    Cell Motility and the Cytoskeleton 14 (1989), S. 187-193 
    ISSN: 0886-1544
    Keywords: centrosphere ; locomotion ; MTOC ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have previously shown that BHK syncytia have the ability to locomote provided the centrospheres are clustered and located adjacent to the cluster of nuclei. This article reports that experimental reorganizations of the centrospheres or the nuclei change the motile behavior of BHK syncytia in a way that is consistent with our previous observations: When fusion of the multiple nuclei occurred in stationary syncytia whose multiple nuclei encircled the centrosphere cluster, the centrospheres were expelled from the ring of nuclei. Consequently, locomotion was initiated in these syncytia even if they had been previously stationary for up to 5 days. Conversely, when a 2-hour incubation in 5 μg/ml cytocholasin B caused the cluster of nuclei to surround the centrosphere cluster, the locomotion of the syncytia was inhibited. Similarly, the dispersal of the centrosphere cluster induced by a 4-hour incubation in 1 μg/ml of colcemid resulted in the long-term cessation of locomotion in motile syncytia.
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  • 41
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    Cell Motility and the Cytoskeleton 14 (1989), S. 201-219 
    ISSN: 0886-1544
    Keywords: cytokinesis ; microinjection ; cleavage furrow ; mitosis ; midbody ; stress fibers ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Actin and the light chains of myosin were labeled with fluorescent dyes and injected into interphase PtK2 cells in order to study the changes in distribution of actin and myosin that occurred when the injected cells subsequently entered mitosis and divided. The first changes occurred when stress fibers in prophase cells began to disassemble. During this process, which began in the center of the cell, individual fibers shortened, and in a few fibers, adjacent bands of fluorescent myosin could be seen to move closer together. In most cells, stress fiber disassembly was complete by metaphase, resulting in a diffuse distribution of the fluorescent proteins throughout the cytoplasm with the greatest concentration present in the mitotic spindle. The first evidence of actin and myosin concentration in a cleavage ring occurred at late anaphase, just before furrowing could be detected. Initially, the intensity of fluorescence and the width of the fluorescent ring increased as the ring constricted. In cells with asymmetrically positioned mitotic spindles, both protein concentration and furrowing were first evident in the cortical regions closest to the equator of the mitotic spindle. As cytokinesis progressed in such asymmetrically dividing cells, fluorescent actin and myosin appeared at the opposite side of the cell just before furrowing activity could be seen there. At the end of cytokinesis, myosin and actin were concentrated beneath the membrane of the midbody and subsequently became organized in two rings at either end of the midbody.
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  • 42
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    Cell Motility and the Cytoskeleton 12 (1989), S. 33-41 
    ISSN: 0886-1544
    Keywords: phosphorylation ; MPM-2 ; mitotic spindle ; microtubule-associated protein ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Mitotic spindles isolated from the diatom Stephanopyxis turris become thiophosphorylated in the presence of ATPγS at specific locations within the mitotic apparatus, resulting in a stimulation of ATP-dependent spindle elongation in vitro. Here, using indirect immunofluorescence, we compare the staining pattern of an antibody against thiophosphorylated proteins to that of MPM-2, an antibody against mitosis-specific phosphoproteins, in isolated spindles. Both antibodies label spindle poles, kinetochores, and the midzone. Neither antibody exhibits reduced labeling in salt-extracted spindles, although prior salt extraction inhibits thiophosphorylation in ATPγS. Furthermore, both antibodies recognize a 205 kd band on immunoblots of spindle extracts. Microtubule-organizing centers and mitotic spindles label brightly with the MPM-2 antibody in intact cells. These results show that functional mitotic spindles isolated from S. turris are phosphorylated both in vivo and in vitro. We discuss the possible role of phosphorylated cytoskeletal proteins in the control of mitotic spindle function.
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  • 43
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    Cell Motility and the Cytoskeleton 12 (1989), S. 66-66 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 44
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    Cell Motility and the Cytoskeleton 12 (1989), S. 71-77 
    ISSN: 0886-1544
    Keywords: microtubule ; colchicine ; cold-treatment ; kinesin localization ; EBTr cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The localization of kinesin in EBTr (bovine embryonic trachea fibroblast) cells was studied by indirect immunofluorescence microscopy using an affinity-purified antibody against bovine adrenal kinesin.It has already been shown that in interphase cells a part of kinesin is located on microtubules and the rest diffusely distributed throughout the cytoplasm [Murofushi et al., 1988]. When microtubules were depolymerized with cold or colchicine treatment, antikinesin antibody-stained fibrous components distinct from microtubules. These fibrous structures were considered to be stress fibers because they were stained with rhodamine-phalloidin and because the fibrous staining with antikinesin antibody was completely lost by treating the cells with cytochalasin D along with colchicine. When cold-treated cells in which a major part of kinesin had been localized on stress fibers were incubated at 37°C, kinesin reappeared on reconstituted microtubules. These observations strongly suggest that kinesin has affinity not only to microtubules but also to stress fibers in culture cells.
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  • 45
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    Cell Motility and the Cytoskeleton 12 (1989), S. 123-123 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 46
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    Cell Motility and the Cytoskeleton 12 (1989), S. 139-149 
    ISSN: 0886-1544
    Keywords: spectrin ; hamster ; cardiac tissue ; cytoskeletal-membrane ; myofibrils ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The spectrins are a family of cytoskeletal-membrane proteins that have a wide tissue distribution. In the present study, we employed polyclonal antibodies made against mammalian and avian erythroid spectrins as well as mammalian brain spectrin to assess their presence and distributions in the mammalian heart. Western blot analyses revealed that all three antibodies were specific for a 240,000 molecular weight α-spectrin subunit found in hamster erythrocyte ghost homogenates, whole hamster heart, and isolated hamster cardiac myofibril homogenates. Spectrin staining was absent from the Triton X-100-extracted supernatant fraction of myofibril preparations, suggesting that the protein is linked to the myofibril precipitate after exposure to the detergent. Frozen, unfixed, 2-μm-thick; sections of adult, Syrian golden hamster cardiac tissue exhibited strong immunofluorescent staining of intercalated discs and Z-bands using all three antibodies. In addition, the mammalian erythroid spectrin antibodies showed staining of the sarcolemma, and in cross section, revealed a delicate internal network of staining that appears to surround individual myofibrils. This may be T-tubule-associated staining. Myofibrils isolated from cardiac myocytes using Triton X-100 show positive Z-band staining using all three antibodies. Double staining with Texas Red-labeled monoclonal desmin and FITC-labeled polyclonal spectrin antibodies revealed that both stained the myofibrillar Z-line regions. These results demonstrate that spectrin is closely associated with the membranes, myofibrils, and intermediate filaments in the mammalian heart.
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  • 47
    ISSN: 0886-1544
    Keywords: stress fibers ; fibroblasts ; myosin ; bipolar filaments ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The authors examined the molecular organization of myosin in stress fibers (microfilament bundles) of cultured mouse embryo fibroblasts. To visualize the organization of myosin filaments in these cells, fibroblast cytoskeletons were treated with gelsolin-like protein from bovine brain (hereafter called brain gelsolin), which selectively disrupts actin filaments. As shown earlier [Verkhovsky et al., 1987], this treatment did not remove myosin from the stress fibers. The actin-free cytoskeletons then were lightly sonicated to loosen the packing of the remaining stress fiber components and fixed with glutaraldehyde.Electron microscopy of platinum replicas of these preparations revealed dumbbell-shaped structures of approximately 0.28 μm in length, which were identified as bipolar myosin filaments by using antibodies to fragments of myosin molecule (subfragment I and light meromyosin) and colloidal gold label. Bipolar filaments of myosin in actin-free cytoskeletons were often organized in chains and lattices formed by end-to-end contacts of individual filaments at their head-containing regions. Therefore, after extraction of actin, it was possible for the first time to display bipolar myosin filaments in the stress fibers of cultured cells.
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  • 48
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    Cell Motility and the Cytoskeleton 12 (1989) 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 49
    ISSN: 0886-1544
    Keywords: mechanochemistry ; fast axonal transport ; cytoskeleton ; vesicle ; motor protein ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Determination of kinetic properties for kinesin adenosine triphosphatase (ATPase), a proposed motor for transport of membranous organelles, requires adequate amounts of kinesin with a consistent level of enzymatic activity. A purification procedure is detailed that produces approximately 2 mg of kinesin at up to 96% purity from 800 g of bovine brain. This protocol consists of a microtubule affinity step using 5′-adenylylimidodiphosphate (AMP-PNP); followed by gel filtration, ion exchange, and hydroxylapatite chromatography; and then sucrose density gradient centrifugation. The microtubule-activated ATPase activity of kinesin coeluted with kinesin polypeptides throughout the purification. Highly purified kinesin had a Vmax of 0.31 μmol/min/mg in the presence of microtubules, with a Km for ATP of 0.20 mM. The kinetic constants obtained in these studies compare favorably with physiological levels of ATP and microtubules. Variations in buffer conditions for the assay were found to affect ATPase activity significantly. A study of the ability of kinesin to utilize a variety of cation-ATP complexes indicated that kinesin is a microtubule-stimulated Mg-ATPase, but kinesin is able to hydrolyze Ca-ATP, Mn-ATP, and Co-ATP as well as Mg-ATP in the presence of microtubules. In the absence of microtubules, Ca-ATP appears to be the best substrate. Studies with several inhibitors of ATPases determined that vanadate inhibited kinesin ATPase at the lowest concentrations of inhibitor, but significant inhibition of the ATPase also occurred with submillimolar concentrations of AMP-PNP. Other inhibitors of kinesin include N-ethylmaleimide, adenosine diphosphate (ADP), pyrophosphate, and tripolyphosphate. Further characterization of the kinetic properties of the kinesin ATPase is important for understanding the molecular mechanisms for transport of membranous organelles along microtubules.
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  • 50
    ISSN: 0886-1544
    Keywords: ABP-120 ; myosin ; actin polymerization ; amoeboid chemotaxis ; cAMP ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Triton-insoluble cytoskeletons were isolated from Dictyostelium discoideum AX3 cells prior to and following stimulation with 2′deoxy cyclic adenosine monophos-phate (cAMP). Temporal changes in the content of actin and a 120,000 dalton actin-binding protein (ABP-120) in cytoskeletons following stimulation were monitored. Both actin and ABP-120 were incorporated into the cytoskeleton at 30-40 seconds following stimulation, which is cotemporal with the onset of pseudopod extension during stimulation of amoebae with chemoattraciants. Changes in the content of total cytoskeletal protein and cytoskeletal myosin were determined under the same experimental conditions as controls. These proteins exhibited different kinetics from those of cytoskeletal ABP-120 and actin following the addition of 2′deoxy cAMP. The authors concluded that the association of ABP-120 with the cytoskeleton is regulated during cAMP signalling. Furthermore, these results indicate that ABP-120 is involved in cross-linking newly assembled actin filaments into the cytoskeleton during chemoattractant-stimulated pseudopod extension.
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    Cell Motility and the Cytoskeleton 13 (1989), S. 41-56 
    ISSN: 0886-1544
    Keywords: cytoskeleton ; ultrastructure ; tegument ; syncytium ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A hallmark feature of parasitic platyhelminths is a cytoarchitecturally unusual syncytial epidermis composed of a peripheral layer of continuous cytoplasm (the ectocytoplasm) connected to underlying nucleated cell bodies by small cytoplasmic bridges. The helminth epidermis, or tegument, plays important roles in protection and nutrient acquisition; cestodes, in fact, completely lack a gastrointestinal tract and absorb all nutritive material through the tegument. Perhaps not surprisingly, the cestode tegument bears certain resemblances to the mucosal epithelium of the vertebrate small intestine, including the possession of a microvillous brush border upon the surface of the ectocytoplasm. In contrast to the intestinal epithelial cell, however, very little is known concerning the nature and organization of the cytoskeleton within the helminth epidermis. Therefore, a number of different microscopical preparative techniques were used to examine the tegument of the tapeworm Hymenolepis diminuta for the presence and distribution of microfilaments, intermediate filaments, and microtubules. It was found that both actin-containing microfilaments and intermediate-sized filaments are present but are restricted to specific locations along the plasmalemmae of the ectocytoplasm. In contrast, microtubules are found throughout the tegument, and are concentrated in the supranuclear regions of the perikarya and in the cytoplasmic bridges interconnecting the perikarya and ectocytoplasm. Unlike brush borders of most other epithelia, the cestode epidermal brush border lacks a filamentous terminal web and is instead associated with microtubules. A network of fine filaments, 5-8 nm in diameter but distinct from actin-containing microfilaments, runs throughout the ectocytoplasm and appears to interlink tegumental vesicles. These fine filaments may represent the primary “skeletal” system responsible for maintaining the structure of the tegumental cytoplasm.
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  • 52
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    Cell Motility and the Cytoskeleton 13 (1989), S. 1-8 
    ISSN: 0886-1544
    Keywords: flagella ; membrane ; glycoproteins ; concanavalin A ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: As an alternative to swimming through liquid medium by the coordinated bending activity of its two flagella, Chlamydomonas can exhibit whole cell gliding motility through the interaction of its flagellar surfaces with a solid substrate. The force transduction occurring at the flagellar surface can be visualized as the saltatory movements of polystyrene microspheres. Collectively, gliding motility and polystyrene microsphere movements are referred to as flagellar surface motility. The principal concanavalin A binding, surface-exposed glycoproteins of the Chlamydomonas reinhardtii flagellar surface are a pair of glycoproteins migrating with apparent molecular weight of 350 kDa. It has been hypothesized that these glycoproteins move within the plane of the flagellar membrane during the expression of flagellar surface motility. A novel mutant cell line of Chlamydomonas (designated L-23) that exhibits increased binding of concanavalin A to the flagellar surface has been utilized in order to restrict the mobility of the concanavalin A-binding flagellar glycoproteins. Under all conditions where the lateral mobility of the flagellar concanavalin A binding glycoproteins is restricted, the cells are unable to express whole cell gliding motility or polystyrene microsphere movements. Conversely, whenever cells can redistribute their concanavalin A binding glycoproteins in the plane of the flagellar membrane, they express flagellar surface motility. Since the 350 kDa glycoproteins are the major surface-exposed flagellar proteins, it is likely that most of the signal being followed using fluorescein isothiocyanate (FITC)-concanavalin A is attributable to these high molecular weight glycoproteins. Therefore, it is likely that the 350 kDa glycoproteins are the ones that must move laterally in the plane of the flagellar membrane in order for the cell to express whole cell gliding motility and microsphere movements along the flagellar surface. This study represents one of the first demonstrations, in any cell type, that whole cell locomotion requires glycoprotein movement within the plane of the plasma membrane.
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  • 53
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    Cell Motility and the Cytoskeleton 13 (1989), S. 145-157 
    ISSN: 0886-1544
    Keywords: microtubule ; membrane ; sytoskeleton ; Trypanosomatidae ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The cytoskeleton of Crithidia fasciculata consists of a corset of paralle microtubules enclosing the cell body and closely underlying the plasma membrane. Distinct sets of crosslinks appear to connect tubules to each other and to membrane. Our objective is to determine the composition of these crosslinks and to elucidate the basis of this spectacular example of membrane-microtubule interaction. We purified three proteins (designated COP-33, -41, and -61 by their subunit Mr), which were consistently abundant in highly purified cytoskeletons. All three bound strongly to microtubules in vitro, and the first two induced bundles through periodic crosslinking. Polyclonal antibodies against each have been used to try to localize these proteins in thin sections of cells or whole mounts of cytoskeletons. Antibodies to COP-41 bound sepcifically to glycosomes, organelles that encapsulate many glycolytic enzymes in these protozoa, and COP-41 has been identified as glyceraldehyde 3-P dehydrogenase.
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  • 54
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    Cell Motility and the Cytoskeleton 13 (1989), S. 104-111 
    ISSN: 0886-1544
    Keywords: embryo ; hamster ; detergent extraction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Mammalian eggs and embryos contain an extensive detergent-resistant cytoskeletal network, including many elements which have been referred to as sheets in hamster eggs. In this study we examined the structure of the sheet-like components by using embedment-free sections and freeze-fracture electron microscopy and found that the sheets are composed of both filamentous and particulate components. In addition, exposure to a high salt extraction medium resulted in the disappearance of the sheets at the ultrastructural level. SDS-polyacrylamide gel electrophoresis of the cell fractions revealed four stainable proteins solubilized by the high salt extraction with one of the proteins being greatly enriched. Because these cytoskeletal sheets undergo an extensive reorganization coincident with key events during early development they serve as internal markers for the establishment of polarity and subsequent differentiation of the first embryonic epithelium, the trophectoderm.
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  • 55
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    Cell Motility and the Cytoskeleton 13 (1989) 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 56
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    Cell Motility and the Cytoskeleton 13 (1989), S. 112-122 
    ISSN: 0886-1544
    Keywords: cytoskeleton ; cell adhesion ; light chain phosphorylation ; immunofluorescence microscopy ; fluorescent indicators ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Following our study in Balb/c 3T3 cells and other cultured fibroblasts of the changes in myosin light chain phosphorylation associated with alterations in cell shape, attachment, and receptor patching, we have now determined the corresponding changes in cytoskeletal myosin distribution, and in the cellular calcium concentration, since this might, in part, mediate such responses.Immunofluorescence microscopy showed that myosin assembly into ordered forms such as actomyosin bundles and myosin sheath almost always correlated with previously shown high phosphorylation levels of myosin regulatory light chain, whereas diffuse distributions usually correlated with low or undetectable levels. An exception was observed in treatment to alter cellular cAMP levels when, in a biphasic response, assembly was correlated inversely with the phosphorylation states shown previously.Fluorescent indicators for intracellular calcium concentration, [Ca++]i, showed that myosin disassembly by trypsin or EGTA acting externally on the cells was preceded by a transient increase in [Ca++]i. For EGTA this was associated with transient recruitment of myosin into dorsal sheath structure as well as the transient enhancement of phosphorylation shown earlier. Blockage of EGTA-induced disassembly could be achieved by azide, which also caused an immediate increase in [Ca++]i and inhibited its subsequent decline. Trypsin-induced dephosphorylation did not appear to involve an eventual reduction of [Ca++]i. Therefore, in many but not all of the systems studied, correlated changes were observed in myosin assembly, [Ca++]i, and the myosin phosphorylation levels shown earlier.
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    Cell Motility and the Cytoskeleton 13 (1989), S. 170-180 
    ISSN: 0886-1544
    Keywords: Avena ; cytoskeleton ; Gramineae ; guard cell ; microtubule ; stomatal complex ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Changes in microtubule organization were monitored in the stomatal complexes of Avena sativa using tubulin immunocytochemistry. Radial arrays of cortical microtubules, previously thought to be characteristic of guard cells, also appear in adjacent subsidiary cells early in development. The subsidiary cell arrays are evident even before guard cells form via division of precursor guard mother cells. Thus, before the stomatal pore opens between sister guard cells, each complex contains four similar microtubule arrays. As the pore opens, however, the subsidiary cell system is reorganized into a network of microtubules distributed along the length of the cell. A similar change is effected in the guard cells after the pore opens. Subsidiary cells and guard cells elongate during later stages of differentiation, and a thickened wall is deposited int he narrow midzone of the latter. At the same time, microtubules in both cells assume a more axial orientation. The results are discussed in terms of developmental symmetry and the control of microtubule organization and cell wall deposition.
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  • 58
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    Cell Motility and the Cytoskeleton 14 (1989), S. 3-11 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 59
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    Cell Motility and the Cytoskeleton 14 (1989), S. 527-543 
    ISSN: 0886-1544
    Keywords: immunofluorescence ; video-enhanced contrast microscopy ; protrusions ; lamellipodia ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The formation of lamellipodia in migrating cells involves dynamic processes that occur in a cyclic manner as the leading edge of a cell slowly advances. We used video-enhanced contrast microscopy (VEC) to monitor the motile behavior of cells to classify protrusions into the temporal stages of initial and established protrusions (Fisher et al.: Cell Motility and the Cytoskeleton 11:235-247, 1988), and to monitor the fixation of cells. Multiple parameter fluorescence imaging methods (DeBiasio et al.: Journal of Cell Biology 105:1613-1622, 1987; Waggoner et al.: Methods in Cell Biology, Vol. 30, Part B, pp. 449-478, 1989) were then used to determine and to map accurately the distributions of actin, myosin and microtubules in specific types of protrusions. Initial protrustions exhibited no substructure as evidenced by VEC and actin was diffusely arranged, while myosin and microtubules were absent. Newly established protrusions contained diffuse actin as well as actin in microspikes. There was a delay in the appearance of myosin into established protrusions relative to the presence of actin. Microtubules were found in established protrusions after myosin was detected, and they were oriented parallel to the direction of migration. Actin and myosin were also localized in fibers transverse to the direction of migration at the base of initial and established protrusions. Image analysis was used to quantify the orientation of actin fibers relative to the leading edge of motile cells. The combined use of VEC, multiple parameter immunofluorescence, and image analysis should have a major impact on defining complex relationships within cells.
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  • 60
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    Keywords: Spermatozopsis ; flagellar roots ; rhizosyndesmos ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The cytoskeleton of the naked, biflagellate green alga Spermatozopsis similis Preisig & Melkonian was isolated by treatment of cells with Nonidet P-40 (0.1%) in lysis buffer (30 mM HEPES, 5 mM EGTA, 15 mM KCl, pH 7) and studied in detail by whole-mount electron microscopy. Isolated cytoskeletons retain the twisted shape of live cells and consist of the two axonemes, the basal apparatus with 4 microtubular and two fibrous roots, and 8-10 secondary cytoskeletal microtubules (SCMT's). The four microtubular flagellar roots differ in number of microtubules (two types with 2 or 5 microtubules, respectively), in their association with fibrous roots of the system I-type (two-stranded roots), in total length (two roots with an average of 4.5 μm and two roots with and average of 7.5 μm), and in length of individual root microtubules. Certain of the root microtubules and most of the SCMT's extend to the posterior end of the cell where they converge, terminate and are interconnected by a fibrous cap-like structure, the rhizosyndesmos. This novel structure consists of a network of 2 nm filaments that presumably lacks centrin as indicated by double immunofluorescence (anti-α-tubulin and anti-centrin) of isolated cytoskeletons. Two-dimensional gel electrophoresis of isolated, purified basal apparatuses of S. similis identifies among other proteins two isoforms of centrin and α- and β-tubulin as intrinsic components.
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  • 61
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    Cell Motility and the Cytoskeleton 12 (1989) 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 62
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    Cell Motility and the Cytoskeleton 14 (1989), S. 26-34 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    Cell Motility and the Cytoskeleton 14 (1989), S. 35-39 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    Cell Motility and the Cytoskeleton 14 (1989), S. 58-61 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 65
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    Cell Motility and the Cytoskeleton 14 (1989), S. 50-57 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 66
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    Cell Motility and the Cytoskeleton 14 (1989), S. 455-457 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 67
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    Cell Motility and the Cytoskeleton 14 (1989), S. 469-484 
    ISSN: 0886-1544
    Keywords: “fixed cortex” model ; neural crest ; mesenchyme ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We present a model of cell motility based on emigration of neural crest cells into the neural tube lumen under in vitro conditions (10% fetal calf serum or YIGSR) that inhibit their normal emigration from the base of the neuroepithelium into surrounding extracellular matrix (ECM). Ultrastructural observations reveal that cells lining the lumen are joined by zonulae adherentes (ZA), which are points of strong intercellular attachment, and thereby serve as markers for fixed regions of plasmalemma and cortical actin. Three major observations of the relationship of cells to the ZA support the “fixed cortex” model of mesenchymal cell migration. First, cells extend apical cel processes past the ZA into the lumen. To do this, they must make new apical plasmalemma and actin corrtex that the endoplasm slides into. Second, elongated cells are observed in the lumen that are still attached via ZA to the neuroepithelium. This indicates that all of the endoplasm finally slides past the ZA. Third, numerous cytoplasmic pieces, often attached to each other and to the neuroepithelium via ZA, are found at the site where cells appear to have detached from the epithelium after entering the lumen. Since the ZA is fixed in location, the endoplasm must have slid past it into newly manufactured anterior cortex and plasmalemma, with the trailing end of the cell finally snapping off. The “fixed cortex” theory of cell migration agrees with existing data in that it predicts the polarized insertion of new plasmalemma and actin at the leading end of the cell, but it differs significantly from existing theories of mesenchymal cell migration in that it states that the cell surface remains firmly attached to the substratum while the myosin-rich endoplasm slides past it.
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  • 68
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    Cell Motility and the Cytoskeleton 14 (1989), S. 491-500 
    ISSN: 0886-1544
    Keywords: intracellular motility ; endocytosis ; cytoskeleton ; ATPase ; retrograde transport ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A microtubule associated protein from brain tissue (MAP 1C), has been found to possess many properties in common with ciliary and flagellar dyneins (Paschal et al.: J. Cell Biol. 105:1273-1282, 1987). However, this protein, now designated as cytoplasmic dynein, exhibited several properties which distinguish it from axonemal forms of the enzyme. We have investigated these characteristics further in a study of cytoplasmic dyneins from non-neuronal tissues. Rat liver and testis in particular were found to contain high levels of cytoplasmic dynein. The yield of dynein from testis was over 70 μg/g of tissue, making this the best source of cytoplasmic dynein of all tissues so far examined. The characterization of dynein from these sources has confirmed and extended our previous observations concerning the unique properties of cytoplasmic dynein. Activation of liver and testis dynein occured at low (〈1 mg/ml) tubulin concentration. Polypeptides identified as subunits of brain cytoplasmic dynein (74, 59, 57, 55, and 53 kDa) were present in liver and testis preparations. In addition, polypeptides at 150 and 45 kDa were found to copurify with the non-neuronal dyneins. The liver and testis enzyme hydrolyzed pyrimidine nucleotides at rates up to 12.5 times faster than ATP, though the relative affinity of cytoplasmic dynein for CTP was much lower (Km = 1.0 mM) than that for ATP. The properties of the testis enzyme were consistent with its identification as a cytoplasmic dynein rather than a sperm axonemal precursor. These data indicate that cytoplasmic dyneins may be widespread in distribution and that they share certain biochemical properties unique from those of axonemal dyneins. These characteristics are consistent with the proposal that cytoplasmic dynein plays a universal role in retrograde organelle motility.
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  • 69
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    Keywords: centriole ; centrosome ; centrin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the unicellular biflagellate green alga Chlamydomonas reinhardtii each basal body is linked to the nucleus by a fibrous nucleus-basal body connector (NBBC) that contains the calcium-binding protein centrin. (Wright et al.: Journal of Cell Biology 101:1903-1912.; Salisbury et al.: Journal of Cell Biology 107:635-642; Huang et al.: Journal of Cell Biology 107:121-131). In order to explore the cellular function of the NBBC we used antiserum directed against centrin to examine a number of mutants known to be defective for basal body assembly and/or localization. Of three variable flagella-number mutants examined, one, vfl-2, is dramatically defective with respect to the NBBC in that (1) the union between basal bodies and nucleus is very labile, (2) there is no detectible centrin in the NBBC region, and (3) total cellular centrin levels are reduced 75-80% relative to wild type. The existence of these defects in a mutant incapable of maintaining normal flagellar number supports the view that the NBBC plays an important role in determining proper basal body localization and/or segregation. In contrast to vfl-2, the mutants vfl-1, vfl-3, uni-1, and bald-2 contain approximately normal levels of centrin and possess stable NBBCs. The observation of NBBCs in the mutant bald-2, which lacks all but very rudimentary basal bodies, indicates that the assembly of the NBBC does not require fully formed basal bodies and that such assembly may not require basal bodies at all. Finally, the possibility that the NBBC is required for induction of gene expression following deflagellation was tested by examining vfl-2 for such induction. Results indicate that the connector does not play a necessary role in the induction process.
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    Cell Motility and the Cytoskeleton 14 (1989), S. 544-551 
    ISSN: 0886-1544
    Keywords: ingestion ; cell; encapsulation ; cell; size of granulocytes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Micromanipulation of yeast particles and blood granulocytes has been used to study the kinetics of single phagocytosis events. The ingestion process was quantitated by observation of sequential adhesion and encapsulation times. Both adherence and encapsulation times were found to increase greatly as the temperature was reduced below 37°C calcium in solution facilitated adhesion of the particle to the phagocyte but not encapsulation; both adhesion and encapsulation processes required a minimum level of plasma components (presumably complement). The general nature of these observations were confirmatiory of previous studies, but this study is unique in that the specific time course of single particle ingestion was quantitated. It was immediately apparent that the phagocytosis process was 100% efficient above the threshold concentrations required for plasma and temperature, but variations in times from cell to cell indicated heterogeneity in the population. The total time for ingestion varied from as low as 2 sec/particle at 37°C to above several min/particle below 15°C. Encapsulation times for particles were normalized by estimates of particle surface areas to establish a specific time/unit area of particle surface: from 0.5 sec/10-8 cm2 at 37°C to greater than 8 sec/10-8 cm2 at 15°C. The temperature dependence of the encapsulation time correlated well with the temperature dependence of the “apparent” viscosity for granulocytes measured by micropipet aspiration. As such, the kinetic properties observed in these phagocytosis tests are consistent with a model that both assembly of the contractile system and the displacement of the surface by active contraction in phagocytosis are limited by viscous dissipation in the cell. Based on temperature dependence of the adhesion time, the activation energy associated with “turning on” the contractile system is quite large, with a value of about 31 kcal/mole. Finally, it was found that serial “feeding” of yeast to a single granulocyte satiated the phagocyte only after six to eleven particles had been encapsulated. The number limit to ingestion was directly proportional to inital size of the granulocyte.
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    Cell Motility and the Cytoskeleton 14 (1989), S. 562-571 
    ISSN: 0886-1544
    Keywords: cell motility ; video-enhanced microscopy ; ATPase ; sodium fluoride ; motor proteins ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Kinesin from porcine brain was prepared by a procedure based on the strong binding of the protein to microtubules in the presence of sodium fluoride and ATP. The protocol reduces the requirement for taxol and AMP-PNP. The kinesin is active in terms of its ability to move microtubules on glass slides and its ATPase. The ATPase of this kinesin is about 8 nmol/min/mg; it is activated to 19 nmol/min/mg in the presence of microtubules. The relationship between gliding velocity and ATP concentration follows Michaelis-Menten kinetics. Using the motility assay, the maximal velocity is 0.78 μm/sec, and the Km values is 150 μM for ATP. For GTP the corresponding values are 0.38 μm/sec and 1.7 mM. ADP is a competitive inhibitor (Ki = 0.29 mM).Crude preparations of kinesin do not support motility on glass slides, whereas gel-filtered kinesin does. A search for potential inhibitory factors showed that one of them is MAP2; however, its inhibitory effect becomes visible only in certain conditions. MAP2 bound to microtubules does not inhibit kinesin-induced motility. However, when MAP2 and kinesin are preadsorbed to the glass surface independently of microtubules, MAP2 prevents the interaction of kinesin with microtubules, as if it formed a “lawn” that acted as a spacer and thus repelled the MAP-free microtubules or crosslinked the MAP-containing ones. The repelling effect of MAP2 domains (projection or assembly fragments obtained by chymotryptic cleavage) added separately is less pronounced and be overcome by kinesin. These results reinforce the view of MAP2 as a spacer molecule.
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  • 72
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    Cell Motility and the Cytoskeleton 12 (1989), S. 1-11 
    ISSN: 0886-1544
    Keywords: ciliary motility ; cAMP ; Ca2+ ; phosphoproteins ; signal transduction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This study seeks to identity phosphoproteins in axonemes from Paramecium letraurelia whose phosphorylation responses to adenosine 3′,5′-cyclic monophosphate (cAMP) and Ca2+ parallel responses induced by these agents in ciliary behavior in this cell. In purified rxonemes, over 15 bands ranging from Mr 〉300 kDa to 19 kDa on SDS-PAGE incorporate 32P from adenosine 5′-γ-[32P]tri-phosphate (γ-32P-ATP) at pCa 7 in the absence of cAMP. A major band whose label turns over rapidly was identified at Mr 43 kDa. In the presence of 5 μM cAMP, more than eight bands, but not the Mr 43 kDa band, were labeled additionally or enhanced their labeling. These phosphoproteins and their kinases are structural components of the axoneme. Overall, some of the same major bands are labeled in the presence of cAMP in Triton X-100-permeabilized paramecia that retain their behavioral responses and in axonemes mechanically isolated from these cells. In particular, two major bands have been identified whose phosphorylation is greatly enhanced by cAMP at low concentrations: (1) a 29 kDa polypeptide whose cAMP-dependent phosphorylation is diminished at pCa 4 compared with pCa 7 and (2) a 65 kDa polypeptide whose phosphorylation is pCa insensitive. These polypeptides meet minimal criteria for signal-sensitive regulators of motility parameters in the Paramecium axoneme.
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    Cell Motility and the Cytoskeleton 12 (1989), S. 23-32 
    ISSN: 0886-1544
    Keywords: surface immunoglobulin ; concanavalin A ; fodrin ; DNase inhibition ; FACS ; pyrene actin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: CH12 is a murine B-cell lymphoma whose surface immunoglobulin (sIg) and concanavalin A (Con A) receptors patch and cap readily. Actin may be involved in CH12 patching and capping, since fodrin and F-actin collect under the cap, and cytochalasin D inhibits sIg capping. We have examined the state of the actin cytoskeleton during patching and capping. A wide range of concentrations of rabbit anti-mouse antibody (RAM) and Con A were used to patch or cap CH12 cells. G-actin was quantitated by DNase I inhibition, F-actin was quantitated by fluorescence-activated cell sorter analysis of fluorescent phalloidin staining, and actin nucleation sites were measured by pyrene actin polymerization. None of these methods detected any significant changes in actin when compared to control cells or untreated cells, leading us to conclude that increased actin polymerization is not necessary for capping to occur. The significance of these data to the membrane flow and cytoskeletal models of capping is discussed.
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    Cell Motility and the Cytoskeleton 12 (1989), S. 12-22 
    ISSN: 0886-1544
    Keywords: actin ; CDPK ; cytoskeleton ; cytochalasin D (CD) ; rhodamine-phalloidin (RP) ; pollen ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We recently purified a calcium-dependent but calmodulin- and phospholipid-independent protein kinase (CDPK) from cultured plant cells (Harmon et al.: Plant Physiology 83:830-837, 1987). A monoclonal antibody (mAb 3B9) directed against CDPK was used to localize this protein in Allium root cells and Tradescantia pollen tubes using immunofluorescence techniques. The mAb 3B9 staining pattern showed that CDPK is localized within a fibrous network in the cytoplasm resembling the normal interphase network of F-actin. Treatment of tissue with 10 μM cytochalasin D (CD) prior to fixation abolished the staining pattern. Double-localization experiments in which pollen tubes were first stained with mAb 3B9 and then with rhodamine-phalloidin (RP) demonstrated that CDPK and F-actin were colocalized. Monoclonal antibody 3B9 did not react with purified actin from rabbit muscle or Dictyostelium and did not bind to proteins corresponding to the Mr of actin in crude extracts of Allium root tips and Tradescantia pollen tubes.CDPK did not phosphorylate purified rabbit muscle or Dictyostelium actin in vitro. Binding studies showed that CDPK (1) does not cosediment with actin filaments and (2) does not form a complex with G-actin. The data indicate that although CDPK does not interact directly with actin, it may be associated with an actin-binding protein and therefore could play a role in the regulation of the plant cytoskeleton.
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  • 75
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    Cell Motility and the Cytoskeleton 12 (1989), S. 127-138 
    ISSN: 0886-1544
    Keywords: cytokinesis ; cytoskeleton ; microinjection ; mitosis ; myotubes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Fluorescently labeled desmin was incorporated into intermediate filaments when microinjected into living tissue culture cells. The desmin, purified from chicken gizzard smooth muscle and labeled with the fluorescent dye iodoacetamido rhodamine, was capable of forming a network of 10-nm filaments in solution. The labeled protein associated specifically with the native vimentin filaments in permeabilized, unfixed interphase and mitotic PtK2 cells. The labeled desmin was microinjected into living, cultured embryonic skeletal myotubes, where it became incorporated in straight fibers aligned along the long axis of the myotubes. Upon exposure to nocodazole, microinjected myotubes exhibited wavy, fluorescent filament bundles around the muscle nuclei. In PtK2 cells, an epithelial cell line, injected desmin formed a filamentous network, which colocalized with the native vimentin intermediate filaments but not with the cytokeratin networks and microtubular arrays. Exposure of the injected cells to nocadazole or acrylamide caused the desmin network to collapse and form a perinuclear cap that was indistinguishable from vimentin caps in the same cells. During mitosis, labeled desmin filaments were excluded from the spindle area, forming a cage around it. The filaments were partitioned into two groups either during anaphase or at the completion of cytokinesis. In the former case, the perispindle desmin filaments appeared to be stretched into two parts by the elongating spindle. In the latter case, a continuous bundle of filaments extended along the length of the spindle and appeared to be pinched in two by the contracting cleavage furrow. In these cells, desmin filaments were present in the midbody where they gradually were removed as the desmin filament network became redistributed throughout the cytoplasm of the spreading daughter cells.
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    Cell Motility and the Cytoskeleton 12 (1989), S. 181-181 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 77
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    Cell Motility and the Cytoskeleton 12 (1989), S. 216-224 
    ISSN: 0886-1544
    Keywords: actin microfilaments ; cytochalasin ; immunofluorescence ; phalloidin ; cytoplasmic streaming ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A comparison of actin localization in pollen tubes of Nicotiana has been made using a monoclonal actin antibody and rhodamine-phalloidin (RP). The monoclonal antiactin, based on Western blotting of pollen tube extract, labels a polypeptide at 45 kD that comigrates with muscle actin. A 51-kD unknown protein and three bands less than 45 kD, presumed to be proteolytic fragments of actin, are also observed. Structural observaations using this antibody reveal a network of axially oriented strands of microfilaments (MFs). The MFs are distributed throughout the length of the pollen tube except at the very tip, where diffuse staining is usually observed. A similar pattern of MFs is evident after RP staining. When pollen tubes are treated with cytochalasins (CB or CD) cytoplasmic streaming is inhibited, as is tube elongation. Microscopic analysis reveals that the microfilament (MF) pattern is markedly altered; however, the antibody and RP produce different staining patterns. The antibody reveals many MF strands that distribute throughout the tube length and extend into the very tip. In contrast, RP shows mostly a diffuse staining pattern with only a few short clumps of filamentous material. Immunogold labelling of sections of pollen tubes prepared by rapid-freeze fixation and freeze substitution reveals that actin MF bundles are indeed present after cytochalasin treatment. Our results thus question reports in the literature, based on phalloidin staining, asserting that cytochalasin fragments or destroys actin MFs.
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    Cell Motility and the Cytoskeleton 14 (1989), S. 263-270 
    ISSN: 0886-1544
    Keywords: compartmentalization ; muscle cells ; actins ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The functional significance of multiple isoactins in the same cell is still not understood. To address this question, we examined the response of smooth muscle and cardiac muscle α-isoactins to a serial extraction procedure applied to both muscle and nonmuscle cell types. We compared these extraction results with results obtained with the β- and γ-nonmuscle actin isoforms from the same cells. In differentiated BC3H1 nonfusing muscle cells (smooth muscle α-isoactin), in human rhabdomyosarcoma cells (cardiac α-isoactin), and in chick skeletal muscle cells (cardiac α-isoactin), different fractions were found selectively enriched in either the nonmuscle or the muscle-specific actin isoforms compared with their relative abundance in whole cell extracts. Conversely, when these same isoactins were examined either in undifferentiated BC3H1 cells or in mouse nonmuscle cells stably transfected with a cardiac α-isoactin gene, no enrichment of these isoforms above their relative abundance in whole cell extracts was observed. These results indicate that within the muscle or muscle-like cells examined, the different actin isoforms were either selectively utilized or localized. These results further show that isoactin-specific responses observed were apparently related to the cell type in which they were found and not to differences in inherent physical properties such as solubility of the different isoactins examined.
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    Cell Motility and the Cytoskeleton 14 (1989), S. 251-262 
    ISSN: 0886-1544
    Keywords: Acanthamoeba ; affinity chromatography ; Dictyostelium ; NMR spectroscopy ; platelets ; myosin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We present evidence that native profilin can be purified from cellular extracts of Acanthamoeba, Dictyostelium, and human platelets by affinity chromatography on poly-L-proline agarose. After applying cell extracts and washing the column with 3 M urea, homogeneous profilin is eluted by increasing the urea concentration to 6-8 M. Acanthamoeba profilin-I and profilin-II can subsequently be separated by cation exchange chromatography. The yield of Acanthamoeba profilin is twice that obtained by conventional methods. Several lines of evidence show that the profilins fully renature after removal of the urea by dialysis: (1) dialyzed Acanthamoeba and human profilins rebind quantitatively to poly-L-proline and bind to actin in the same way as native, conventionally purified profilin without urea treatment; (2) dialyzed profilins form 3-D crystals under the same conditions as native profilins; (3) dialyzed Acanthamoeba profilin-I has an NMR spectrum identical with that of native profilin-I; and (4) dialyzed human and Acanthamoeba profilins inhibit actin polymerization. We report the discovery of profilin in Dictyostelium cell extracts using the same method. Based on these observations we conclude that urea elution from poly-L-proline agarose followed by renaturation will be generally useful for preparing profilins from a wide variety of cells. Perhaps also of general use is the finding that either myosin-II or alpha-actinin in crude cell extracts, can be bound selectively to the poly-L-proline agarose column depending on the ionic conditions used to equilibrate the column. We have purified myosin-II from both Acanthamoeba and Dictyostelium cell extracts and alpha-actinin from Acanthamoeba cell extracts in the appropriate buffers. These proteins are retained as complexes with actin by the agarose and not by a specific interaction with poly-L-proline. They can be eluted by dissociating the complexes with ATP and separated from actin by gel filtration if necessary.
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    Cell Motility and the Cytoskeleton 14 (1989), S. 271-287 
    ISSN: 0886-1544
    Keywords: actin-membrane interaction ; adhesion plaque ; vinculin ; integrin ; fibroblasts ; epithelial cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: To investigate the role of talin in the anchoring of actin-containing stress fibers to the cell membrane of nonmuscle cells, a fluorescent analog of the adhesion plaque protein talin was developed, characterized, and microinjected into living cells. Purified chicken gizzard talin was covalently labeled with the fluorescent dye lissamine rhodamine B sulfonyl chloride. The fluorescently labeled protein was then chromatographed on Sephadex G-25 and DEAE-cellulose in order to remove free dye and denatured protein. The fluorescent talin was able to bind purified vinculin and was localized in adhesion plaques, membrane ruffles, microspikes, and polygonal networks in acetone-permeabilized nonmuscle cells. In cells that were double-stained with fluorescent talin and an affinity-purified anti-talin an-tibody, a one-to-one correspondence of adhesion plaque staining was seen. Living epithelial cells (PtK2) were microinjected during interphase with fluorescent talin. Computer-enhanced video microscopy was used to document adhesion plaque dynamics such as (1) changes in plaque shape, (2) alterations in plaque positions, and (3) the appearance, growth, and dissolution of plaques. In cells that were followed during mitosis, the adhesion plaques disappeared during cell rounding and then subsequently reappeared upon spreading of the two daughter cells. Treatment of microinjected cells with DMSO in order to disassemble stress fibers resulted in an altered localization of the fluorescent talin. Upon recovery of the cell from the drug, the talin was visualized in its characteristic submembraneous position. These results are the first to document the role and distribution of talin in dynamic processes occurring in living microinjected nonmuscle cells.
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    Cell Motility and the Cytoskeleton 14 (1989), S. 302-303 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Cell Motility and the Cytoskeleton 14 (1989), S. 288-301 
    ISSN: 0886-1544
    Keywords: axopodium ; microtubules ; X-body ; receptor site ; contraction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the heliozoan Echinosphaerium, rapid axopodial contraction often occurs during food capturing. In morphological studies, it has been considered that rapid contraction is caused by conformation is change of the X-body. We determined that reaction sites or receptors for anion exchange resin, which can induce rapid contraction, were located in every region of the axopodium. However, the probability of locating sites where contraction was induced was lower in the middle region than in the distal region of the axopodium. In cases in which contraction was not induced by resin placed in the middle region of the axopodium, so-called bead formation was induced instead. At the fine structural level, only granulated forms of the X-body were observed in this beading region. These results suggest that rapid contraction results from disassembly of axonemal microtubules and the simultaneous contraction of the X-body and that bead formation represents a stage when only the X-body contracts. Furthermore, effects of metabolic inhibitors and Ca2+ channel blockers revealed that contraction of the X-body did not depend on the supply of adenosine triphosphate, but on Ca2+ influx. Ultrastructural observations revealed that the mass of the granulated X-body was aggregated into the proximal region of the axopodium, suggesting that the X-body might be associated with the undercoat of axopodial membrane or the axonemal microtubules themselves.
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    Cell Motility and the Cytoskeleton 14 (1989) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Cell Motility and the Cytoskeleton 14 (1989), S. 309-331 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Cell Motility and the Cytoskeleton 14 (1989), S. 332-339 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Cell Motility and the Cytoskeleton 14 (1989), S. 340-344 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Cell Motility and the Cytoskeleton 14 (1989), S. 449-454 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 88
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    Cell Motility and the Cytoskeleton 14 (1989), S. 485-490 
    ISSN: 0886-1544
    Keywords: pigment organelle dispersion ; secretion ; liver ; yeast ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We reported previously that the dispersion of carotenoid droplets in permeabilized xanthophores requires cAMP, ATP, and a cytosolic factor present in several secretory tissues as well as in xanthophores. We have now purified this factor from beef liver to apparent/near homogeneity. It appears to be a heterodimer with Mr ∼125,000. The purified factor has little or no ATPase activity, with or without the presence of actin. Nor does it stimulate the ATPase activity of carotenoid droplets. Its exact function in carotenoid droplet dispersion is thus unclear. Since dispersion of carotenoid droplets is an anterograde translocation, we propose the name anterogin for this protein. We also report that yeast cytosol has anterogin activity.
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    Cell Motility and the Cytoskeleton 14 (1989), S. 458-468 
    ISSN: 0886-1544
    Keywords: F-actin ; intermediate filament ; microtubules ; pterinosomes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Immunofluorescence and phase-contrast microscopic studies of goldfish xanthophores with aggregated or dispersed pigment show two unusual features. First, immunofluorescence studies with anti-actin show punctate structures instead of filaments. These punctate structures are unique for the xanthophores and are absent from both goldfish dermal no-pigment cells and a dedifferentiated cell line (GEM-81) derived from a goldfish xanthophore tumor. Comparison of immunofluorescence and phase-contrast microscopic images with electron microscopic images of thin sections and of Triton-insoluble cytoskeletons show that these punctate structures represent pterinosomes with radiating F-actin. The high local concentration of actin around the pterinosomes results in strong localized fluorescence such that, when the images have proper brightness for these structures, individual actin filaments elsewhere in the cell are too weak in their fluorescence to be visible in the micrographs. Second, whereas immunofluorescence images with anti-tubulin show typical patterns in xanthophores with either aggregated or dispersed pigment, namely, filaments radiating out from the microtubule organizing center, immunofluorescence images with anti-actin or with anti-intermediate filament proteins show different patterns in xanthophores with aggregated versus dispersed pigment. In cells with dispersed pigment, the punctate structrues seen with anti-actin are relatively evenly distributed in the cytoplasm, and intermediate filaments appear usually as a dense perinuclear band and long filaments elsewhere in the cytoplasm. In cells with aggregated pigment, both intermediate filaments and pterinosomes with associated actin are largely excluded from the space occupied by the pigment aggregate, and the band of intermediate filaments surrounds not only the nucleus but also the pigment aggregate. The patterns of distribution of the different cytoskeleton components, together with previous results from this laboratory, indicate that formation of the pigment aggregate depends at least in part on the interaction between pigment organelles and microtubules. The possibility that intermediate filaments may play a role in the formation/stabilization of the pigment aggregate is discussed.
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    Cell Motility and the Cytoskeleton 14 (1989), S. 501-515 
    ISSN: 0886-1544
    Keywords: phototaxis ; motion analysis system ; photoreception ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In darkness Chlamydomonas cells swim forward with a helical motion of low amplitude. When cells are exposed to light conditions they are not adapted to, they perform direction changes or stop responses depending on how far the stimulant irradiance is shifted from the former adaptation level. Here we present the utility of a commercially available motion analysis system for the analysis of the Chlamydomonas stop response.Chlamydomonas cells stop in darkness only occasionally with a random temporal distribution but with a highly increased frequency after a flash or a step-up light stimulation. The delay time, tD, defined as the minimal time difference between flash and a light-induced stop, was below 50 ms. The reaction time, tR, defined as the time difference between flash and the maximal probability for a cell to stop was found to be 140 ms. During a stop the cells swim revers for some 300 ms with 20% of the forward swimming speed.To a given stimulation program cells adapt with a first-order kinetic. In the case of a single step-up or step-down stimulation this adaptation consists of a single stop response followed by direction changes which decrease in frequency to a certain steady-state level. To repetitive light pulses the cells respond with a gradual disappearance of step-up stop responses and a concurrent appearance of step-down responses.External calcium influences the stop response in a multifunctional way. For stop responses to occur 300 nM calcium are required. At increasing calcium concentrations the duration of a stop response is extended. Besides light, calcium regulates the time course of light-adaption and the absolute adaptation level.A kinetic model for the description of adaptation is presented.
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    Cell Motility and the Cytoskeleton 14 (1989), S. 75-79 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Cell Motility and the Cytoskeleton 14 (1989), S. 118-127 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Cell Motility and the Cytoskeleton 14 (1989), S. 146-146 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Cell Motility and the Cytoskeleton 14 (1989), S. 128-135 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Cell Motility and the Cytoskeleton 14 (1989), S. 136-145 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Cell Motility and the Cytoskeleton 14 (1989), S. 147-155 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 97
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    Cell Motility and the Cytoskeleton 14 (1989), S. 401-415 
    ISSN: 0886-1544
    Keywords: microtubule ; microtubule-associated protein (MAP) ; RNA ; RNP ; mitotic spindle ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Microtubules were purified from unfertilized eggs of the sea urchins Arbacia punctulata, Lytechinus pictus, Lytechinus variegatus, and Strongylocentrotus purpuratus. Numerous densely stained particles (24 × 26 nm) are associated with microtubules isolated from each of these sea urchins. The most striking aspect of this structure is an extended, slightly curved arm that appears to attach the particles to the microtubule. Morphologically similar particles are associated with microtubules of the isolated first cleavage mitotic apparatus. The particles are attached to the microtubules by ionic interactions and contain large amounts of extractable RNA. Based upon their size and density, RNA and protein composition, and sedimentation in sucrose gradients, the microtubule-associated particles are identified as ribosomes.
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    Cell Motility and the Cytoskeleton 14 (1989), S. 393-400 
    ISSN: 0886-1544
    Keywords: bundles ; microtubule associated protein ; tubulin binding protein ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The cell body of Trypanosomatidae is enclosed in densely packed, crosslinked, subpellicular microtubules closely underlying the plasma membrane. We isolated the subpellicular microtubules from bloodstream Trypanosoma brucei parasites by use of a zwitterion detergent. These cold stable structures were solubilized by a high ionic strength salt solution, and the soluble proteins that contained tubulin along with several other proteins were further fractionated by Mono S cation exchange column chromatography. Two distinct peaks were eluted containing one protein each, which had an apparent molecular weight of 52 kDa and 53 kDa. (Mr was determined by SDS-gel electrophoresis.) Only the 52 kDa protein showed specific tubulin binding properties, which were demonstrated by exposure of nitrocellulose-bound trypanosome proteins to brain tubulin. When this protein was added to brain tubulin in the presence of taxol and GTP, microtubule bundles were formed with regular crosslinks between the parallel closely packed microtubules. The crosslinks were about 7.2 nm apart (center to center). Under the same conditions, but with the 53 kDA protein or without trypanosome derived proteins, brain tubulin polymerized to single microtubles. It is thus suggested that the unique structural organization of the subpellicular microtubules is dictated by specific parasite proteins and is not an inherent property of the polymerizing tubulin. The in vitro reconstituted microtubule bundles are strikingly similar to the subpellicular microtubule network of the parasite.
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    Cell Motility and the Cytoskeleton 14 (1989), S. 416-423 
    ISSN: 0886-1544
    Keywords: wave parameters ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The movement parameters of a sea urchin sperm flagellum can be manipulated mechanically by applying various modes of periodic vibrations to the sperm head held by suction in the tip of a micropipette. The beat frequency of the flagellum readily synchronizes with the frequency of the externally imposed lateral vibration, and the plane of flagellar bending waves adapts itself to the plane of the pipette vibration (Gibbons et al., J. Cell Biol. 101:270a, 1985; Nature 325: 351-352, 1987). In this study, we observed the particular effects of external asymmetric forces on flagellar beating parameters by vibrating the micropipette holding the sperm head in a transverse sawtooth-like motion composed of a rapid effective stroke and a slower recovery stroke, while keeping the vibration frequency constant. The results demonstrate that the timing of bend initiation within the flagellar beat cycle can be controlled mechanically by changing the time point within the vibration cycle at which the micropipette changes its direction of motion. A switch in the sidedness of the asymmetric movement of the micropipette produces dramatic changes in the profiles of bend growth in the basal 5 μm of the flagellum but has almost no effect on the asymmetry or other parameters of bending in the mid- and distal regions of the flagellum. Our results suggest that elastic strain within the basal region of the flagellar structure may play a more significant role in the process of bend initiation than has been realized heretofore.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 100
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 14 (1989) 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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