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  • 1
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 20 (1991), S. 228-241 
    ISSN: 0886-1544
    Schlagwort(e): fine filaments ; intracellular pH ; motility ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: The cytoskeleton of the amoeboid spermatozoa of Ascaris suum consists of major sperm protein (MSP) filaments arranged into long, branched fiber complexes that span the length of the pseudopod and treadmill rearward continuously due to assembly and disassembly at opposite ends of the complexes (Sepsenwol et al., Journal of Cell Biology 108:55-66, (1989)). Examination by video-enhanced microscopy showed that this cytoskeletal flow is tightly coupled to sperm locomotion. The fiber complexes treadmilled reaward at the same rate (10-50 μm/ min) as the cell crawled forward. Only fiber complexes with their plasmalemmal ends within a limited sector along the leading edge of the pseudopod underwent continuous assembly. Thus, the location of this sector, which occupies about 50% of the pseudopod perimeter, determined the direction of sperm locomotion. Treatment of sperm with agents that lower intracellular pH, such as, weak acids and protonophores, caused the fiber complexes to disassemble completely in 4-5 sec. Removal of these compounds resulted in reassembly of the cytoskeleton in a pattern that mimicked treadmilling in intact sperm. The fiber complexes were reconstructed by assembly at their plasmalemmal ends so that within 30-60 sec the entire filament system reformed and the cell resumed locomotion. Both cytoskeletal reassembly and treadmilling required exogenous HCO3-. These results suggest that variation in intracellular pH may help regulate cytoskeletal treadmilling and thereby play a significant role in sperm locomotion.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 193-205 
    ISSN: 0886-1544
    Schlagwort(e): amoeboid motility ; fluorescence ratio imaging ; BCECF ; nematodes ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: The development and locomotion of the amoeboid sperm of the nematode, Ascaris suum, depend on precise control of the assembly of their unique major sperm protein (MSP) filament system. We used fluorescence ratio imaging of cells loaded with BCECF to show that intracellular pH (pHi) is involved in controlling MSP polymerization in vivo. Spermatogenesis is marked by a cycle of MSP assembly-disassembly-reassembly that coincides with changes in pHi. In spermatocytes, which contain MSP in paracrystalline fibrous bodies, pHi was 6.8, 0.6 units higher than in spermatids, which disassemble the fibrous bodies and contain no assemblies of MSP filaments. Activation of spermatids to complete development resulted in rapid increase in pHi to 6.4 and reappearance of filaments. Treatment of spermatocytes with weak acids caused the fibrous bodies to disassemble whereas incubation of spermatids in weak bases induced MSP assembly. The MSP filaments in spermatozoa are organized into fiber complexes that flow continuously rearward from the leading edge of the pseudopod. These cells established a pseudopodial pH gradient with pHi 0.15 units higher at the leading edge, where fiber complexes assemble, than at the base of the pseudopod, where disassembly occurs. Acidification of these cells caused the MSP cytoskeleton to disassemble and abolished the pH gradient. Acid removal resulted in reassembly of the cytoskeleton, re-establishment of the pH gradient, and re-initiation of motility. MSP assembly in sperm undergoing normal development and motility and in cells responding to chemical manipulation of pHi occurs preferentially at membranes. Thus, we propose that filament assembly in sperm is controlled by pH-sensitive MSP-membrane interaction. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 16 (1990), S. 266-278 
    ISSN: 0886-1544
    Schlagwort(e): ATPase ; flagella ; intermediate chains ; vanadate-mediated photolysis ; vertebrate ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Outer-arm dynein purified from trout spermatozoa was disrupted by low-ionicstrength dialysis, and the resulting subunits were separated by sucrose density-gradient centrifugation. The intact 19 S dynein, containing the α- an β-heavy chains, intermediate chains (ICs) 1-5 and light chains (LCs) 1-6, yielded several discrete particles: a 17.5 S adenosine triphosphatase (ATPase) composed of the γ-and β-chains ICs 3-5 and LC 1; a 9.5 S complex containing ICs 1 and 2 together with LCs 2, 3, 4, and 6; and a single light chain (LC 5), which sedimented at ∼4 S. In some experiments, ICs 3-5 also separated from the heavy chain complex and were obtained as a distinct subunit. Further dissociation of the 17.5 S particle yielded a 13.1 S ATPase that contained the β-heavy chain and ICs 3-5. The polypeptide compositions of the complexes provide new information on the intermolecular associations that occur within dynein.Substructural features of the trout dynein polypeptides also were examined. The heavy chains were subjected to vanadate-mediated photolysis at the V1 sites by irradiation at 365 nm in the presence of Mg2+, ATP, and vanadate. Fragment pairs of relative molecular mass (Mr) 245,000/185,000 and 245,000/170,000 were obtained from the α- and β-heavy chains, respectively. Photolysis of these molecules at their V2 sites, by irradiation in the presence of vanadate and Mn2+, yielded fragments of Mr 160,000/270,000 and 165,000/250,000, respectively. These values confirm that the α- and β-heavy chains have masses of 430,000 and 415,000 daltons, respectively.Immunological analysis using monoclonal antibodies revealed that one intermediate chain from trout dynein (IC 2) contains epitopes present in two different intermediate chains from Chlamydomonas dynein. This indicates that specific sequences within the dynein intermediate chains have been highly conserved throughout evolution.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 31 (1995), S. 66-81 
    ISSN: 0886-1544
    Schlagwort(e): microtubule motor proteins ; immunolocalization ; RT-PCR ; Northern/Southern blots ; microinjection ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: To examine the possible role of kinesin in pigment granule migration in the retinal pigment epithelium (RPE) of teleosts, we investigated the expression and distribution of kinesin heavy chain (KHC) in RPE. Blots of fish RPE lysates probed with two well-characterized antibodies to KHC (H2 and HD) displayed a prominent band at 120 kD. A third KHC antibody (SUK4) recognized a band at 118 suggesting the presence of two KHC isoforms in teleost RPE. Reverse transcriptase-polymerase chain reaction (RT-PCR) of mRNA from RPE using primers homologous to conserved regions of the KHC motor domain resulted in the homologous to conserved regions of the KHC motor domain resulted in the identification of two putative KHC genes (FKIF1 and FKIF5) based on partial amino acid sequences. Previous studies had demonstrated a requirement for microtubules in pigment granule aggregation in RPE. In addition, the reported microtubule polarity orientation in RPE apical projections is consistent with a role for kinesin in pigment granule aggregation. Immunofluorescent localization of KHC in isolated RPE cells using H2 revealed a mottled distribution over the entire cell body, with no detectable selective association with pigment granules, even in cells fixed while aggregating pigment granules. Microinjected KHC antibodies had no effect on pigment granule aggregation or dispersion, although each of the three antibodies has been shown to block kinesin function in other systems. Thus we found no evidence for KHC function in RPE pigment granule aggregation. However, the two KHC isoforms may participate in other microtubule-dependent processes in RPE.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 31 (1992), S. 249-252 
    ISSN: 1040-452X
    Schlagwort(e): Sexual dimorphism ; In vitro ; Early development ; Cattle ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: The classical concept of sex determination in mammals is that a Y chromosomal gene controls the development of the indifferent gonad into a testis. Subsequent divergence of sexual phenotypes is secondary to this gonadal determination. The most likely candidate gene is SRY (sex-determining region Y) in humans, and Sry in mouse. However, several lines of evidence indicate that sexual dimorphism occurs even before the indifferent gonad appears. Here we present evidence that bovine male embryos generally develop to more advanced stages than do females during the first 8 days after insemination in vitro. Corresponding relationships between both cell numbers and mitotic indices and sex were also seen. Although it is not clear whether this phenomenon involves factors originating before or after fertilization, these findings suggest that sex-related gene expression affects the development of embryos soon after activation of the embryonic genome and well before gonadal differentiation.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 39 (1994), S. 375-383 
    ISSN: 1040-452X
    Schlagwort(e): In vitro fertilization ; Bovine ; Embryo ; Genome Activation ; Transcription ; 3H-Uridine ; α-Amanitin ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: The timing of genome activation in bovine embryos is still not well defined. The objective of this study was therefore to investigate transcription in bovine embryos with a high potential to develop in culture after in vitro fertilization, by examining, autoradiographically, their incorporation of 3H-uridine. Initial experiments determined that developmental potential in vitro could be related to the time of first division of the zygote. Embryos that completed their first cleavage within 30 hours of exposure to sperm were more likely to develop into blastocysts (65.7%) and to hatch (50.9%). Using such embryos, it was found that 10 of 12 8-cell and all 11 4-cell stage embryos were labeled after a 2-4-hr exposure to 3H-Uridine. Among 2-cell stage embryos, 0 of 23, 3 of 17, 8 of 15, and 3 of 4 were labeled after exposure to 3H-uridine of 2, 4, 7, and 10 hr, respectively. Treatment with α-amanatin (10-100 m̈g/ml) blocked 3H-uridine incorporation but did not inhibit cleavage during the first 4 cell cycles. It was concluded that transcription occurs as early as the 2-cell stage in bovine embryos in vitro but is not critical to the first four cell cycles. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 27 (1990), S. 295-304 
    ISSN: 1040-452X
    Schlagwort(e): Chimaera ; Stem cells ; Cell marker ; Interspecies ; Transfer ; Freemartin ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Bovine inner cell masses (ICMs) were isolated by immunosurgery at day 8 or 10, or by dissection at day 14, and combined with day-5.5 morulae. Aggregation was obtained between 89%, 62%, and 0% of the day-5:day-8, day-5:day-10, day-5:day-14 composites, respectively. Chromosome analysis of composites potentially carrying the 1/29 translocation as a chromosome marker and temporarily transferred to the bovine uterus for 8 days showed that chimaeric day-14 embryos can be obtained from day-5:day-8 aggregation. The definitive transfer of eight day-5:day-8 and 11 day-5:day-10 composites resulted in the birth of six and four calves, respectively; five of the six, but none of the four, were chimaeric. The five chimaeras showed mostly the ICM phenotype. The morphological differences between ICMs at different stages of development were examined by electron microscopy and related to the success of the aggregation technique. It is concluded that bovine embryonic cells can regulate for at least 3 days difference in development but not 5 days even though aggregation is still possible.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 33 (1992), S. 141-148 
    ISSN: 1040-452X
    Schlagwort(e): Embryos ; Autoradiography ; Radiolabeled nucleic acids ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Two methods for preparing embryos for autoradiographic study of newly synthesized nucleic acids are described and compared. The first method consists of rapidly fixing radiolabeled embryos with acetic acid:methanol, spreading them on glass slides and exposing them for 8 days with a photographic emulsion. The second method consists of fixing, embedding in resin, and sectioning the embryos before their exposure with the emulsion for 3 weeks. Both techniques have many applications in studies of early embryonic activity, but the spread technique is very sensitive, simpler, and faster. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 1 (1988), S. 57-62 
    ISSN: 1040-452X
    Schlagwort(e): Embryo ; Polymerase chain reaction ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Endogenous and foreign DNA sequences can be detected in an extremely small number of cells via sequence amplification in vitro. The polymerase chain reaction (PCR) technique applied in multiple cycles allows the amplification of specific short regions of the genome to levels that can be detected by DNA blotting techniques. Cow and mouse blastocysts were analyzed by PCR for the presence of an endogenous single copy gene or an integrated foreign gene. The endogenous single-copy gene encoding the β chain of bovine luteinizing hormone was detectable in cow blastocysts and in purified bovine genomic DNA representing as few as 25 cells. To determine whether exogenous genes (transgenes) can be detected in preimplantation embryos, transgenic male mice hemizygous for the prokaryotic gene encoding neomycin resistance where bred to nontransgenic females, and the resulting blastocysts were analyzed. The neo gene was detected in approximately half of the embryos. The capability to identify specific gene sequences in a limited number of embryonic cells affords investigators the opportunify to study genetics in early development.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    ISSN: 1040-452X
    Schlagwort(e): Cell cycle ; DNA synthesis ; NEBD ; Nuclear transplantation ; Bovine ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Nuclear transplantations into metaphase II (MII) and S phase oocyte cytoplasm were performed to investigate the influence of recipient cell cycle stage on nuclear function and development of bovine nuclear transplant (NT) embryos. Rate of inactivation of histone H1 kinase and duration of DNA synthesis in activated oocytes were determined. The proportion of S phase blastomeres in in vivo produced day 5.5 bovine embryos was measured. DNA synthesis was also assessed in NT embryos after transfer into MII and S phase cytoplasm. MII NT embryos were produced by fusing a blastomere into a MII oocyte; the fusion pulse served to activate the oocyte. S NT embryos were produced by fusing a blastomere into an early S phase oocyte electrically activated 4 h prior to fusion. Nuclear envelope structure, chromosome constitution, and extent of development were examined in MII and S NT embryos. Histone H1 kinase activity dropped to baseline within 2 h of electrical activation. A second electrical pulse did not alter H1 kinase activity when delivered 4 h after the first pulse. The frequency of S phase blastomeres in day 5.5 bovine embryos ranged from. 79% to 100%, depending on the duration of culture in 3H-thymidine. Nuclear transplantation into MII cytoplasm resulted in a transient drop in DNA synthesis over 3.5 h. DNA synthesis resumed at 4.5 h post activation (hpa), concomittantly with initiation of DNA replication in activated oocytes. In contrast, DNA synthesis was not interrupted after transfer into S phase cytoplasm. DNA synthesis persisted until 13.5 hpa, as in activated oocytes. Partial or complete nuclear envelope breakdown (NEBD) occurred after transfer into MII cytoplasm, whereas the nuclear envelope remained intact in 50% of the embryos or underwent partial breakdown in S phase cytoplasm. A greater proportion of S NT embryos was diploid (50% vs. 23% MII NT embryos, P 〈 0.001), and a higher frequency of S NT embryos developed to the morula or blastocyst stage (22% vs. 5%, P 〈 0.001). The data indicate that DNA synthesis is regulated differently if the recipient oocyte is in MII or in S phase at the time of fusion. Extended DNA synthesis after transfer into MII cytoplasm suggests a re-replication of the donor chromatin. Re-replication, presumably, does not occur after transfer into S phase cytoplasm. Re-replication is likely to be a consequence of permeabilization of the nuclear envelope upon NEBD in MII cytoplasm. Improved regulation of DNA synthesis after transfer into S phase cytoplasm and reduced incidence of chromosome damage in the first cell cycle may have been responsible for increased frequency of development of S NT embryos to the morula/blastocyst stage. © 1993 Wiley-Liss, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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