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  • 1
    Electronic Resource
    Electronic Resource
    Effects of Cell Density on Lipids of Human Glioma and Fetal Neural Cells (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 36 (1981), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Gangliosides, phospholipids, and cholesterol of human glioma (12-18) and fetal neural cells (CH) were analyzed at specified cell densities, from sparse to confluent. Total ganglioside sialic acid, phospholipid phosphorus, and cholesterol increased in the glioma cells on a per cell, mg protein, or mg total lipid basis two- to threefold as cell density increased 25-fold. These same three constituents in the fetal cells increased with cell density on a per cell and mg protein basis but not on a per mg total lipid basis. In glioma cells, the di- and trisialogangliosides (GD2+ GDlb+ GT1) increased from 1–2% of total ganglioside sialic acid at sparse densities to 7–8% at intermediate (logarithmic phase) densities to 10–13% at confluent densities. The set of simpler gangliosides (GM4+ GM3+ GM2) decreased from 50% of total ganglioside sialic acid at sparse glioma cell densities, to 36% at intermediate and 30% at confluent densities. In the fetal neural cells, the set of gangliosides (GM4+ GM3+ GM2) had about 48% of total ganglioside sialic acid in both sparse and confluent preparations. The fetal cells were twofold higher in GM3 (32.4 ± 2.1%) than the glioma cells (16.8 ± 1.6%), but lower in GMt (9.1 ± 0.9% versus 18.2 ± 1.8%), cell densities notwithstanding. Confluent cell preparations of both cell lines were consistently higher in ethanolamine plasmalogen than sparse cells. We conclude that in these two neural cell lines quantitative changes in ganglioside and phospholipid species occurred correlatively as cell densities increased. Higher glioma cell densities were associated with greater proportions of complex ganglioside species. These changes in cell membrane constituents during growth may result from cell contact and may indicate a role for them in cell growth regulation and/or differentiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1981.tb10821.x
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  • 2
    Electronic Resource
    Electronic Resource
    Population dynamics and production of the tropical freshwater shrimp Caridina nilotica (Decapoda: Atyidae) in the littoral of Lake Sibaya (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 11 (1981), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. Seasonal changes in population structure, standing stock levels and production of Caridina nilotica were studied at three sites in the littoral margins of subtropical Lake Sibaya between January 1975 and March 1976. Average population density at these sites declined from a maximum of c. 1400 to a minimum of c. 350 individuals per m2 (3.4–0.4 g m−2 dry wt) during the study, possibly as a result of emigration into peripheral vegetation inundated by rising lake levels.Shrimps bred perennially and, although egg stocks and instantaneous birth rates (b) were highest during summer, no corresponding increases in populaton density were observed, suggesting that the seasonally higher birth rates were offset by higher mortality rates. Population size structure and size-specific sex ratios did not change seasonally to any marked extent. Relative abundance declined with size and females grew larger than males. Clutch size increased linearly as a function of female carapace length.Estimates of overall mean annual somatic production (g m−2 year−1 dry wt) for the three sites between January 1975 and January 1976 ranged between c. 132 (egg-ratio method), 37.5 (summation of growth increments) and 24 (Hynes-Hamilton method) at an annual mean standing stock level of 2.7 g m−2 dry wt (calorific value, 20.34 kJ g−1 dry wt). Production at sites 1, 2 and 3 decreased in line with declining annual mean standing stocks (5.32, 3.67 and 0.23 g m−2, respectively). The growth increment method gave an overall mean annual P/B value of 13.9. Egg production amounted to a further 5.6, 3.6 and 0.1 g m−2 year−1 dry wt (calorific value, 28.01 kJ g−1) at sites 1, 2 and 3, or 2.7 g m−2 year−1 on average.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1981.tb01284.x
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  • 3
    Electronic Resource
    Electronic Resource
    Embryonic duration and post-embryonic growth rates of the tropical freshwater shrimp Caridina nilotica (Decapoda:Atyidae) under laboratory and experimental field conditions (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 10 (1980), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. Embryonic durations and post embryonic growth rates of Caridina nilotica were determined under laboratory conditions at constant temperatures near 18, 24 and 30°C. Embryonic durations and intermoult intervals were negative curvilinear functions of temperature. At a given temperature moulting frequency varied inversely with shrimp size and slight sexual differences were apparent. Moulting frequency of berried females was governed by the temperature-specific embryonic durations.Growth rates were determined from changes in carapace length (CL) of individual shrimps (laboratory) or batches of shrimps (field enclosures) over 1 month and these data were used to calculate temperature-specific life-long growth curves for males and females. Growth in body mass was estimated indirectly from the carapace length-mass relationship of C. nilotica. On average, males grew marginally faster than females during the first 2 months of life, but growth of males larger than CL= 4 mm was considerably depressed relative to that of females. Inflexions in growth rate, apparently related to the onset of sexual maturity, were apparent in both sexes.Under laboratory conditions, the growth rate of males increased with temperature, but temperature-related differences were not as marked in females. Notwithstanding the more rapid moulting rate at 30°C the growth rate of females was slightly slower at 30 than at 24°C as a result of marginally but significantly smaller per moult growth increments observed at 30°C in animals up to CL= 5.5 mm. Possible reasons for this depressed growth are discussed.Growth rates of animals in field enclosures in Lake Sibaya over 1 month in winter (20 ± 3°C) were generally comparable to those estimated for the 18°C laboratory experiments. Growth rates in enclosures containing tripled standing stocks were almost identical to those containing the naturally occurring biomass of animals, suggesting a non-limited environment at least during the time of the experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1980.tb01205.x
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  • 4
    Electronic Resource
    Electronic Resource
    Oxygen consumption in Caridina nilotica (Decapoda: Atyidae) in relation to temperature and size (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 10 (1980), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. The oxygen consumption of shrimps ranging from 1 to 30 mg dry mass was determined at 18, 24 and 30°C using a continuous flow recording respirometer based upon a Clark-type oxygen electrode. Respiration (ascribed to routine metabolism) is described by the power curve: R = a Mb, (R=μg O2 h−1, M= mg dry mass), which gives values of a= 1.632, 2.564 and 4.181, and b= 0.800, 0.898, and 0.793, at 18, 24 and 30°C respectively. The single expression, R= 0.008 T1.829M0.830 provides a reasonable prediction of respiration as a combined function of shrimp size (M) and temperature (T, °C). Using an energy equivalent of 14.14 J mg O2−1 estimates of the energy requirements (E, J h−1 10−3) of routine metabolism are given by the expression: E= 0.115 T1.829M0.830.Variability in oxygen consumption values between individuals is discussed and the observations on C. nilotica are compared with other crustacean studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1980.tb01196.x
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  • 5
    Electronic Resource
    Electronic Resource
    UNEMPLOYMENT INSURANCE AND THE FIRM'S EMPLOYMENT STRATEGY: A EUROPEAN AND UNITED STATES COMPARISON (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Kyklos 35 (1982), S. 0 
    Details
    ISSN: 1467-6435
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Sociology , Economics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1467-6435.1982.tb00177.x
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  • 6
    Electronic Resource
    Electronic Resource
    Mathematical modeling and numerical solutions for functionally dependent bone remodeling (1984)
    Springer
    Calcified tissue international 36 (1984), S. S104 
    Details
    ISSN: 1432-0827
    Keywords: Functional adaptation ; Strain-induced bone remodeling ; Computational model ; Theoretical model ; Predictive model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The phenomenon of bone remodeling is a complex biological process which is dependent on genetic, hormonal, metabolic, and age-related factors as well as functional requirements. The possibility of successfully developing a mathematical model to describe and predict the adaptive response of bone to load will be significantly increased after identification of the nature of the transducer(s) which senses functional requirements and provides signals for the cellular processes responsible for bone synthesis and bone removal. In spite of the present limitations in knowledge about the functional dependence of bone remodeling, a phenomenological model has been developed that assumes that the output signal from the (as yet unspecified) transducer is a remodeling potential that can be modulated by genetic, hormonal, and metabolic factors. An attempt has been made to cast the mathematical model in such a form that the constants and variables appearing in the equations are not mere abstractions, but can be related to biological parameters. In order to use the adaptive hypothesis with specific structural model examples, a numerical procedure has been developed to determine the strain distribution, predict the remodeling (assuming that the remodeling rate is related to the strain history), and update the model by changing the geometry and material properties in response to the remodeling. This numerical procedure is repeatedly iterated to determine the structural architecture at subsequent times. The numerical approach allows use of the remodeling concepts with models of irregular geometry, inhomogeneous material distribution, and anisotropic material properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02406142
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  • 7
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    The Obverse Side of Aristophanes (1897)
    London : Periodicals Archive Online (PAO)
    The Contemporary Review. 71 (1897:Jan./June) 662 
    Details
    ISSN: 0010-7565
    Topics: General, Interdisciplinary
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:0274-1897-071-00-000053
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  • 8
    Electronic Resource
    Electronic Resource
    Evolution and longevity-assurance processes (1981)
    Springer
    Naturwissenschaften 68 (1981), S. 552-557 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Notes: Abstract The role of the development of information fidelity systems in evolution is explored, with evidence that the loss in the ability to maintain the integrity of homeostasis in organisms over time, aging, is correlated with the loss in the ability to maintain integrity at the molecular biological level. Evolutionary-comparative analysis places an upper limit on the number of these systems important to the evolution of longevity in the primates, and suggests the importance of insuring the stability of information bearing macromolecules in evolution and the role of modulators of damage to these moieties in the expression of the senescent state
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00401663
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  • 9
    Electronic Resource
    Electronic Resource
    Fluxes of gases and particles above a deciduous forest in wintertime (1983)
    Springer
    Boundary layer meteorology 27 (1983), S. 237-255 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Eddy-correlation measurements of the vertical fluxes of ozone, carbon dioxide, fine particles with diameter near 0.1 Μm, and particulate sulfur, as well as of momentum, heat and water vapor, have been taken above a tall leafless deciduous forest in wintertime. During the experimental period of one week, ozone deposition velocities varied from about 0.1 cm s−1 at night to more than 0.4 cm s-1 during the daytime, with the largest variations associated primarily with changes in solar irradiation. Most of the ozone removal took place in the upper canopy. Carbon dioxide fluxes were directed upward due to respiration and exhibited a strong dependence on air temperature and solar heating. The fluxes were approximately zero at air temperatures less than 5 °C and approached 0.8 mg m−2 s−1 when temperatures exceeded 15 °C during the daytime. Fine-particle deposition rates were large at times, with deposition velocities near 0.8 cm s−1 when turbulence levels were high, but fluxes directed upward were found above the canopy when the surface beneath was covered with snow. Diffusional processes seemed to dominate fine-particle transfer across quasilaminar layers and subsequent deposition to the upper canopy. Deposition velocities for particulate sulfur were highly variable and averaged to a value small in magnitude as compared to similar measurements taken previously over a pine forest in summer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00125000
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  • 10
    Electronic Resource
    Electronic Resource
    The ultrastructure of somatic neuromuscular junctions in the tick Amblyomma variegatum (Fabr.) (1980)
    Springer
    Cell & tissue research 206 (1980), S. 505-508 
    Details
    ISSN: 1432-0878
    Keywords: Ticks ; Ultrastructure ; Synapses ; Muscles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Peripheral nerve axons synapse with somatic muscle fibres in the tropical bont tick Amblyomma variegatum. Each fibre is innervated by numerous terminals; some of the axons synapse more than once. The nerve terminals on coxal muscle fibres contain agranular electron lucent vesicles 50 to 58 nm in size and have the specialised synaptic membranes characteristic of chemically transmitting nerve-muscle junctions. Some of the terminals on trochanteral muscle fibres additionally contain larger vesicles (90 nm) with electron dense cores, suggesting that these junctions operate with a different kind of neurotransmitter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237979
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