ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

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Influence of soil moisture on the nodulation of post fire seedlings of Ceanothus spp. growing in the Santa Monica Mountains of Southern California (1997)

Pratt, S. D. ; Konopka, A. S. ; Murry, M. A. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 99 (1997), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: During the dry season (early May through September of 1994), following a fall 1993 wildfire, a survey of seedling nodulation was conducted at several sites in the Santa Monica Mountains of Southern California. Seedlings of Ceanothus spinosus, C. megacarpus, C. oliganthus, and C. cuneatus were manually excavated. During this period, only 12 of the 182 seedlings excavated were nodulated, and all of the nodulated seedlings were found in the relatively moist clay soils of a stream bank. No nodules were observed on the 170 seedlings excavated from the drier sites. An irrigation experiment was established in midsummer to assess whether water stress inhibits nodulation of post-fire Ceanothus seedlings. Four plots with numerous seedlings of C. cuneatus and C. spinosus were irrigated with distilled water and monitored over a 9-week period. There was a significant increase in nodulation frequency, water potential, stomatal conductance, transpiration, shoot elongation, and photosynthetic rate of irrigated seedlings compared with adjacent controls. Although these data support the hypothesis that water stress inhibits nodulation. it is unclear whether this is because of an effect of soil moisture on the nodulation capacity of the soils (i.e. on the size and physiological state of the soil Frankia population) or to a host plant response to drought which might prevent actinorhizal root infection and/or nodule development.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1399-3054.1997.tb05371.x

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2

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Xylem dysfunction caused by water stress and freezing in two species of co-occurring chaparral shrubs (1997)

LANGAN, S. J. ; EWERS, F. W. ; DAVIS, S. D.

Oxford, UK : Blackwell Publishing Ltd

Plant, cell & environment 20 (1997), S. 0

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ISSN: 1365-3040

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Water transport from the roots to leaves in chaparral shrubs of California occurs through xylem vessels and tracheids. The formation of gas bubbles in xylem can block water transport (gas embolism), leading to shoot dieback. Two environmental factors that cause gas embolism formation in xylem conduits are drought and freezing air temperatures. We compared the differential vulnerabilities of Rhus laurina and Ceanothus megacarpus, co-dominant shrub species in the coastal regions of the Santa Monica Mountains of southern California, to both water stress-induced and freezing-induced embolism of their xylem. Rhus laurina has relatively large xylem vessel diameters, a deep root system, and a large basal burl from which it vigorously resprouts after wildfire or freezing injury. In contrast, Ceanothus megacarpus has small-diameter vessels, a shallow root system, no basal burl and is a non-sprouter after shoot removal by wildfire. We found that R. laurina became 50% embolized at a water stress of –3 MPa and 100% embolized by a freeze–thaw cycle at all hydration levels. In contrast, C. megacarpus became 50% embolized at a water stress of –9 MPa and 100% embolized by freeze–thaw events only at water potentials lower than –3 MPa. Reducing thaw rates from 0·8 °C min−1 to 0·08 °C min−1 (the normal thaw rate measured in situ) had no effect on embolism formation in R. laurina but significantly reduced embolism occurrence in well-hydrated C. megacarpus (embolism reduced from 74 to 35%). These results were consistent with the theory of gas bubble formation and dissolution in xylem sap. They also agree with field observations of differential shoot dieback in these two species after a natural freeze–thaw event in the Santa Monica Mountains.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-3040.1997.d01-94.x

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3

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Long-term potentiation in awake mutant mice (1997)

Errington, M. L. ; Bliss, T. V. P. ; Morris, R. J. ; [et al.]

[s.l.] : Macmillan Magazines Ltd.

Nature 387 (1997), S. 666-667

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ISSN: 1476-4687

Source: Nature Archives 1869 - 2009

Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics

Notes: [Auszug] The relationship between long-term potentiation (LTP) and spatial learning has been explored in a variety of genetically engineered mice with deletions of specific genes. With few exceptions, LTP in these animals has been studied in the hippocampal slice preparation. The conditions required to ...

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1038/387666a0

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4

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Characterisation of the low affinity interaction between rat cell adhesion molecules CD2 and CD48 by analytical ultracentrifugation (1997)

Silkowski, H. ; Davis, S. J. ; Barclay, A. Neil ; [et al.]

Springer

European biophysics journal 25 (1997), S. 455-462

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ISSN: 1432-1017

Keywords: Key words T-lymphocytes ; Dissociation constant

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Physics

Notes: Abstract CD2 is a cell adhesion molecule found on the plasma membrane of T-lymphocytes. Its counter-receptor in rat is the structurally related CD48. This interaction is believed to contribute to the adhesion of T-cells to other cells such as cytotoxic targets and antigen presenting cells. Cell-cell adhesion involves the formation of multiple cell adhesion molecule complexes at the cell surface and if cell-cell de-adhesion is to occur, these complexes need to be disrupted. The affinities of cell adhesion molecule interactions are suggested to be relatively weak to allow this de-adhesion of cell-cell interactions. The CD2/CD48 interaction has been studied using recombinant extracellular proteins and the affinity of the interaction of soluble recombinant rat CD2–CD48 has been determined (at 37°C) using surface plasmon resonance (and shown to be weak), with the dissociation constant Kd=60–90 µm. The values determined by surface plasmon resonance results could be affected by the immobilisation of the ligand on the chip and any self-association on the chip. We used three different analytical ultracentrifuge procedures which each allowed the interaction to be studied in free solution without the need for an immobilisation medium. Both sedimentation equilibrium (using direct analysis of the concentration distribution and also modelling of molecular weight versus concentration data) and sedimentation velocity at 5°C yielded dissociation constants in the range of 20– 110 µm, supporting the surface plasmon resonance findings showing that binding between these cell adhesion molecules is relatively weak. These studies also ruled out the presence of any significant self-association of the reactants which could lead to systematic error in the surface plasmon resonance results.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002490050060

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5

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Spreading and Retention of Vaginal Formulations in Post-Menopausal Women as Assessed by Gamma Scintigraphy (1997)

Brown, J. ; Hooper, G. ; Kenyon, C. J. ; [et al.]

Springer

Pharmaceutical research 14 (1997), S. 1073-1078

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ISSN: 1573-904X

Keywords: vaginal delivery ; gamma scintigraphy ; bioadhesion ; pessary ; post-menopausal women

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract Purpose. In this paper we report on the first scintigraphic evaluation of vaginal dosage forms in post-menopausal women. To date, almost nothing is known about the in vivo performance of pharmaceutical formulations in the human vagina, which is a major deficiency in the rational design of drug delivery systems for both existing and new indications. Methods. The vaginal spreading and clearance of a radiolabelled pessary formulation and Replens® (polycarbophil) gel, was assessed in six healthy, post-menopausal female volunteers over a six hour period using the technique of gamma scintigraphy. Results. In five out of the six subjects studied, clearance of the two formulations exhibited very little intra-subject variation. However, there was considerable inter-subject variability in clearance; in Subject 5 circa 80% of the products were retained whilst in Subject 2 less than 2% was present at the end of the six hour imaging period. Importantly, there was no evidence to suggest that either of the formulations dispersed material beyond the cervix, into the uterus, in any of the subjects studied. Conclusions. The lack of significant retention of these products in most of the volunteers has obvious implications for the delivery of therapeutic agents. This study shows that gamma scintigraphy is an invaluable technique with which to assess novel formulations aimed at optimising retention in the vagina for topical or systemic drug delivery.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1012113714552

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6

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CCD Observations of Comet Hale-Bopp at Shajn Telescope I. Coude spectra (1997)

Korsun, P. P. ; Davis, S. P. ; Shavrina, A. V. ; [et al.]

Springer

Earth, moon and planets 78 (1997), S. 119-125

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ISSN: 1573-0794

Keywords: Comet Hale-Bopp ; Coude spectrum ; identified emissions

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Physics

Notes: Abstract Spectroscopic observations of Comet Hale-Bopp were made at the 2.6 m Shajn Telescope of the Crimean Astrophysical Observatory. Some spectra were obtained with high spectral resolution, FWHM = 0.18–0.4Å, in the coude focus on February 22 and 26, 1997. The observations were made in selected spectral windows (4805–4872 Å,6528–6595 Å, 7186–7253 Å, 8276–8408 Å).The spectrograph slit was centered on the nucleus and had dimensions of 25.2 × 0.6 arcsec2 on the plane of the sky. The continuum spatial profiles were extremely asymmetrical toward the Sun. However, the continuum-subtracted spatial profiles of the molecular emissions were symmetrical relative to the nucleus, except for C2. The shape of the spatial profiles of the C2 emissions is similar to that one of continuum but is more flattened. So, there are evidences that dust can be an additional source of the C2 radicals in the cometary coma. The main aim of our research was identification of the cometary emissions. Using recent laboratory spectroscopic data we identified newlines of C2 associated with the transitions from high rotational levels in the 4805–4872 Å spectral region. We detected cometary Hα emission as well. Emissions of NH2, H2O+,and C2 (Phillips system) were found in the red spectral windows. Some emission features are still unassigned.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1006212520669

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7

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Activation of the Mononuclear Phagocyte System by Poloxamine 908: Its Implications for Targeted Drug Delivery (1997)

Armstrong, T. I. ; Moghimi, S. M. ; Davis, S. S. ; [et al.]

Springer

Pharmaceutical research 14 (1997), S. 1629-1633

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ISSN: 1573-904X

Keywords: mononuclear phagocyte system ; targeted drug delivery ; nanoparticles ; poloxamine 908

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract Purpose. To investigate the effect of poloxamine 908 on the MPS activity and the importance of its mode of presentation to the immune system. Methods. Solutions of endotoxin free poloxamine 908 were injected daily intravenously to rats, and the effect on the degree of sequestration by the liver of I125 labelled, poloxamine 908-coated 60 nm polystyrene particles was investigated by studying effect of dosing regimen(s) and assessment of opsonic activity. Results. After 3 or 4 days repeated dosing with poloxamine 908 (0.7 mg) in solution, the poloxamine 908-coated polystyrene particles (60 nm) were rapidly cleared from the circulation. The increased sequestration of the particles by the liver lasted for more than 7 days after last dosing with the poloxamine 908 solution. In subsequent studies, it was found that a single dose of poloxamine 908 (0.7 mg) in solution was sufficient to activate the MPS 4 days after the injection. The increased uptake was found not be mediated by a serum component, nor was it due to proliferation of the Kupffer cells in the liver. Conclusions. The results provide evidence that a solution of endotoxin-free poloxamine 908 activates the MPS so that 4 days after injection otherwise long-term circulating poloxamine 908-coated particles are sequestered by the liver. This finding has implications for use of such coated systems in therapeutic situations.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1012194721763

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