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  • Life and Medical Sciences  (252)
  • Genetics  (21)
  • Wiley-Blackwell  (252)
  • 1990-1994  (240)
  • 1980-1984
  • 1940-1944  (9)
  • 1915-1919  (1)
  • 1890-1899  (2)
  • 1994  (126)
  • 1991  (114)
  • 1940  (9)
  • 1916  (1)
  • 1895  (2)
Collection
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Years
  • 1990-1994  (240)
  • 1980-1984
  • 1940-1944  (9)
  • 1915-1919  (1)
  • 1890-1899  (2)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Comparative kinetics of short and long sperm in sperm dimorphic Drosophila species (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 269-274 
    Details
    ISSN: 0886-1544
    Keywords: minor and major waves ; beat frequeney ; wave propagation velocity ; coiling diameter ; storage effect ; differential behaviour ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: All species of the Drosophila obscura group exhibit within-ejaculate sperm length dimorphism. The present work is a contribution to the understanding of sperm competition through a comparative study of sperm kinetic parameters in four of these species. Videomicrographic observations at 200 frames per second of sperm from males and females, out of the storage organ, prior or after storage were made. Drosophila sperm display both major and minor waves. The former is analysed by measuring coiling diameter (μm) and the latter by recording both beat frequency (s-1) and wave propagation velocity (μm·s-1). Results show that the ‘behaviour’ of short and long spermatozoa noticeably differ: short sperm kinetics remains unaltered after storage while both major and minor waves of long spermatozoa are markedly modified. Thus, evidence is provided here of a sort of “differential activation” which is assumed to result in different survival abilities of short and long sperm within the storage organ of females.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970190405
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  • 2
    Electronic Resource
    Electronic Resource
    Nongenomic regulation of extracellular matrix events by vitamin D metabolites (1994)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 56 (1994), S. 331-339 
    Details
    ISSN: 0730-2312
    Keywords: 1,25-(OH)2D3 ; 24,25-(OH)2D3 ; matrix vesicles ; nongenomic regulation ; extracellular matrix ; alkaline phosphatase ; phospholipase A2 ; Protein kinase C ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Vitamin D metabolites appear to regulate chondrocytes and osteoblasts via a combination of genomic and nongenomic mechanisms. Specificity of the nongenomic response to either 1,25-(OH)2D3 or 24, 25-(OH)2D3 may be conferred by the chemical composition of the target membrane and its fluid mosaic structure, by the presence of specific membrane receptors, or by the interaction with classic Vitamin D receptors. Nongenomic effects have been shown to include changes in membrane fluidity, fatty acid acylation and reacylation, arachidonic acid metabolism and prostaglandin production, calcium ion flux, and protein kinaase C activity. Chondrocytes metabolize 25-(OH)D3 to 1,25-(OH)2D3 and 24,25-(OH)2D3; production of these metabolites is regulated by both growth factors and hormones and is dependent on the state of cell maturation. 1,25-(OH)2D3 and 24,25-(OH)2D3 may interact directly with extracellular matix vesicles to regulate their function in the matrix, including protease activity, resulting in matrix modefication and calcification. Isolated matrix vesicles, produced by growth zone chondrocytes, can activate latent transforming growth factor-β when incubated with exogenous 1,25-(OH)2D3. These observations suggest that nongenomic regulation of martix vesicle structure and function may be a mechanism by which mesenchymal cells, like osteoblasts and chndrocytes, may modulate events in the extracellular matrix at sites distant from the cell surace.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240560309
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  • 3
    Electronic Resource
    Electronic Resource
    Preparation of spermatogenic cell populations at specific stages of differentiation in the human (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 30 (1991), S. 275-282 
    Details
    ISSN: 1040-452X
    Keywords: Human testis ; Cell separation ; Elutriation ; Spermatid ; Ultrastructure ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Studying biochemical events in human spermatogenesis requires separated populations of spermatogenic cells. Dissociation of these cells was performed by a Trypsin-DNAse method adapted from the technique used for rodents. Cell separation was performed by centrifugal elutriation. Seven populations were collected, one further purified by Percoll gradient centrifugation, giving nine different cell populations. The efficiency of the cell separation was evaluated by phase contrast microscopy, flow cytometric DNA analysis, and electron microscopy. Five populations were enriched in spermatids: two in round spermatids (87% and 73%), another in round (52%) and elongating (44%) spermatids, another constituted by 80% elongating spermatids, and the last by 90% elongated spermatids. Two of the four remaining populations were enrichied in primary spermatocytes (74% and 54%); another population was the upper part of the Percoll gradient and constituted cytoplasmic lobes and residual bodies (89%); the last population was made up of various cells, with no specific enrichment. Electron microscopic observations revealed good preservation of the separated cells; only the flagella from elongated spermatids were lost. Furthermore, an unusual pattern of nucleoplasm distribution during stages 2-4 of spermatid differentiation was observed and its signification is discussed with regard to the shape of the human spermatozoon.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080300316
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  • 4
    Electronic Resource
    Electronic Resource
    Increase in copy number of an integrated vector during continuous culture of Hansenula polymorpha expressing functional human haemoglobin (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 10 (1994), S. 1569-1580 
    Details
    ISSN: 0749-503X
    Keywords: Hansenula ; haemoglobin ; integration ; continuous culture ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Recombinant human haemoglobin A (rHbA) was produced by a leucine-requiring strain of Hansenula polymorpha which had been transformed with an integration vector containing the Saccharomyces cerevisiae LEU2 gene and cDNAs for the expression of α and β globin each driven by the H. polymorpha MOX promoter. After 40 generations in a chemostat it was found that the integrated vector had become amplified in the host strain. In some cases this led to an increase in LEU2 gene dosage, but a loss of globin expression cassettes. In other cases the globin gene dosage also increased. These changes coincided with an increase in rHbA production in the culture, which was reversed when the dilution rate was increased. Isolates from a chemostat culture producing elevated levels of rHbA were grown in fed-batch fermentations, resulting in higher productivities than when inoculated with the parent strain. The rHbA produced was purified and characterized. Oxygen binding studies and electrospray mass spectrometry showed that the rHbA had been processed and assembled correctly, and behaved as a fully functional co-operative tetramer.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320101206
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  • 5
    Electronic Resource
    Electronic Resource
    Developmental protein synthesis is required for the transcription of Dictyostelium prespore genes (1991)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 12 (1991), S. 113-122 
    Details
    ISSN: 0192-253X
    Keywords: Dictyostelium discoideum ; cyclo heximide ; emetine ; protein synthesis ; mRNA accu mulation ; transcription ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: It has been established previ- ously that the maintenance of expression of pre-spore-specific genes of Dictyostelium discoideum is prevented by the translational inhibitor cyclohex- imide. The drug had no effect upon the level of transcripts of the other genes examined, prestalk-specific or cell type-nonspecific. However, the interpretation of this result is open to question, because of possible nonspecific effects of cyclo-heximide. We have now characterized the cellular specificity and temporal profiles of mRNA accumu- lation of additional Dictyostelium cDNA clones, and have examined other inhibitors of in vivo protein synthesis. Four structurally and mechanistically distinct translational inhibitors each prevented the reaccumulation of prespore transcripts in cyclic AMP-primed, disaggregated amoebae. These results establish the importance of developmental protein synthesis in the accumulation of prespore gene transcripts. Nuclear run-on transcription assays were used to learn whether protein synthesis is required primarily for mRNA synthesis or transcript stability. A transcriptional time course first demonstrated that the abundance of these cell-specific transcripts during development mirrors their rates of synthesis. Significantly, the protein synthesis requirement of the prespore genes examined also occurs at the level of mRNA transcription, implying the existence of one or more developmentally regulated transcriptional activators.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020120119
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  • 6
    Electronic Resource
    Electronic Resource
    Association of vanadate-sensitive Mg2+-ATPase and shape change in intact red blood cells (1991)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 46 (1991), S. 284-290 
    Details
    ISSN: 0730-2312
    Keywords: erythrocytes ; magnesium ; echinocyte ; calcium ; plasma membrane ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Intact human erythrocytes, initially depleted of Mg2+ by EDTA incubation in the presence of A23187, exhibit Mg2+-dependent phosphate production of around 1.5 mmol per liter cells · h, half-maximally activated at around 0.4 mM added free Mg2+. This appears to correspond to Mg2+-stimulated adenosine triphosphatase (Mg2+-ATPase) activity found in isolated membranes, which is known to have a similar activity and affinity for Mg2+. Vanadate (up to 100 μM) inhibited Mg2+-dependent phosphate production and ATP breakdown in intact cells. Over a similar concentration range vanadate (3-100 μM) transformed intact cells from normal discocytes to echinocytes within 4-8 h at 37°C, and more rapidly in Mg2+-depleted cells. The rate of Ca2+-induced echinocytosis was also enhanced in Mg2+-depleted cells. These results support previous studies in erythrocyte ghosts suggesting that vanadate-induced shape change is associated with inhibition of Mg2+-ATPase activity localized in the plasma membrane of the red blood cell.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240460403
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  • 7
    Electronic Resource
    Electronic Resource
    Interactions between brain mitochondria and cytoskeleton: Evidence for specialized outer membrane domains involved in the association of cytoskeleton-associated proteins to mitochondria in situ and in vitro (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 233-261 
    Details
    ISSN: 1059-910X
    Keywords: Brain mitochondria ; Microtubules ; Neurofilaments ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The surface distribution of several proteins (porin, hexokinase, and two proteins associated with microtubules or actin filaments) on the outer membrane of brain mitochondria was analyzed by immunogold labelling of purified mitochondria in vitro. The results suggest the existence of specialized domains for the distribution of porin in the outer mitochondrial membrane. Similarities between the distribution of porin and the distribution of microtubule-associated proteins bound in vitro to mitochondria suggested that mitochondria and microtubules interact by binding microtubule-associated proteins to porin-containing domains of the outer membrane. This hypothesis was supported by biochemical studies on outer mitochondrial proteins involved in in vitro binding of cytoskeleton elements. In vitro interactions between mitochondria and microtubules or neurofilaments were analyzed by electron microscopy. These studies revealed cross-bridging between the outer membrane of mitochondria and the two cytoskeleton elements. Cross-bridging was influenced by ATP hydrolysis and by several proteins associated with the surface of mitochondria or with microtubules. In addition, unidentified proteins which were recognized by antibodies to all intermediate filaments subunits were associated either with the mitochondrial surface or with microtubules. This data suggest the participation of additional cytoplasmic proteins in the interactions between cytoskeleton elements and mitochondria. © 1994 Wiley-Liss, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070270305
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of gonadotropins upon the incidence and kinetics of meiotic maturation of macaque oocytes in vitro (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 37 (1994), S. 467-472 
    Details
    ISSN: 1040-452X
    Keywords: Oocyte maturation ; Germinal vesicle breakdown ; Polar body ; LH/FSH ; Macaque ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The specific aim of this study was to determine the effects of gonadotropins in vitro upon the incidence of and precise time interval to germinal vesicle breakdown (GVB) and extrusion of the first polar body (PB1) in oocytes from nonstimulated rhesus monkeys. Cumulus-enclod germinal vesicle (GV) stage oocytes from 10 normal, cycling rhesus monkeys in the follicular phase of the menstrual cycle were cultured with either: (1) 1.0 μg/ml human follicle-stimulating hormone (hFSH), (2) 10 μg/ml human luteinizing hormone (hLH), (3) 1.0 μg/ml hFSH and 10 μg/ml hLH, or (4) no gonadotropins (controls). Oocytes (n = 234) were examined at 3-hr intervals from 0 to 21 hr and at 4-hr intervals from 24 to 52 hr for GVB and PB1. Neither the incidence of GVB (hFSH: 63.5%; hLH: 56.1%; both gonadotropins: 63.1%; no gonadotropins: 53.6%) nor extrusion of PB1 (hFSH: 41.3%; hLH: 36.4%; both gonadotropins: 36.9%; no gonadotropins; 31.9%) differed (P 〉 0.05) among treatments. The time to GVB was accelerated (P 〈 0.05) by gonadotropins (hFSH: 10.8 ± 1.7 hr; hLH: 10.1 ± 1.8 hr; both gonadotropins: 8.8 ± 1.1 hr) when compared to controls (17.4 ± 2.0 hr). However, the time interval to extrusion of PB1 did not differ (P 〉 0.05) among treatments (hFSH: 32.3 ± 1.2 hr; hLH: 35.1 ± 1.4 hr; both gonadotropins: 35.2 ± 1.3 hr; no gonadotropins: 34.1 ± 1.2 hr). The mean interval to extrusion of PB1 was 34.1 ± 0.6 hr. In conclusion, GVB and PB1 extrusions appear to be, in part, independently regulated events in macaque oocytes matured in vitro since the timing of PB1 extrusion is not tightly coupled with the onset of GVB. Although the developmental potential of oocytes may be enhanced by gonadotropins, alternative approaches must be developed to improve the poor competence of oocytes from nonstimulated monkeys to mature in vitro. © 1994 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080370415
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  • 9
    Electronic Resource
    Electronic Resource
    Three-dimensional structure of lung elastin demonstrated by scanning electron microscopy/stereo-pair images (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 29 (1994), S. 254-261 
    Details
    ISSN: 1059-910X
    Keywords: TEM ; Formic acid ; Alkali ; Freeze-drying ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The aim of this study was to expose the inflated 3-D structure of lung elastin. Formic acid digestion followed by freeze-drying unveiled the lamellar framework. The 3-D structure of elastin was well preserved within the alveolar septa and ducts, as demonstrated by scanning electron microscopy/stereo-pair photography. Elastin fibers are seen in the alveolar septa, which are continuous with the lamellae. The removal of collagen fibers and cells by formic acid was visualised as a function of time: The optimum was 48 hours. Transverse sections still retained some collagen fibrils and partially digested cells in addition to elastin as shown by transmission electron microscopy (TEM). Forme acid digestion followed by critical point drying caused damage to the lamellar structures and they appeared to collapse. Sodium hydroxide digestion combined with freeze-drying did not preserve the 3-D lamellar structure of elastin, but converted it into flat ribbonlike bands. The main structures remaining following alkali treatment were identified by TEM as collagen fibrils well preserved in their original locations. © 1994 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070290312
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  • 10
    Electronic Resource
    Electronic Resource
    A model for characterizing residential ground current and magnetic field fluctuations (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 15 (1994), S. 53-65 
    Details
    ISSN: 0197-8462
    Keywords: intermittents ; transients ; EMF ; electric power ; ground currents ; exposure assessment ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The current through the residential grounding circuit is an important source for magnetic fields; field variations near the grounding circuit accurately track fluctuations in this ground current. In this paper, a model is presented which permits calculation of the range of these fluctuations. A discrete network model is used to simulate a local distribution system for a single street, and a statistical model to simulate unbalanced currents in the system. Simulations of three-house and ten-house networks show that random appliance operation leads to ground current fluctuations which can be quite large, on the order of 600%. This is consistent with measured fluctuations in an actual house. © 1994 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250150109
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