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  • 1
    Electronic Resource
    Electronic Resource
    Dextran sulfate sodium (DSS) induced experimental colitis in immunodeficient mice: Effects in CD4+-cell depleted, athymic and NK-cell depleted SCID mice (1996)
    Springer
    Inflammation research 45 (1996), S. 181-191 
    Details
    ISSN: 1420-908X
    Keywords: Disease models ; Mice ; Immunocompromised ; Ulcerative colitis ; Dextran sulfate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Administration of dextran sulfate to mice, given in the drinking water results in acute or subacute colonic inflammation, depending on the administration protocol. This colonic inflammation exhibits ulceration, healing and repair, and a therapeutic response that makes it valuable for the study of mechanisms that could act in the pathogenesis of human ulcerative colitis, a disease thought to have an immunologically dependent pathogenesis. To investigate if immunological mechanisms were involved in the induction of colonic inflammation in this model, mice with different degrees of immunodeficiency were used. It was shown that dextran sulfate induced colitis could be induced in Balb/c mice depleted of CD4+ helper T cells by treatment with monoclonal antibodies preceded by adult thymectomy. The depletion of CD4+ was verified by flow cytometric analysis. Furthermore, the colonic inflammation could equally be induced in athymic CD-1 nu/nu mice lacking thymusderived T cells, in T and B-cell deficient SCID mice, and also in SCID mice depleted of NK cells by treatment with anti-asialo GM1 antibodies. The NK-cell depletion was verified by measuring spleen NK-cell activity. The resulting colonic inflammation in all these types of deficient mice was qualitatively comparable, as shown by clinical and histological appearance. These results indicate that the presence of functional T, B and NK cells is not crucial for the induction of dextran sulfate colitis in mice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02285159
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  • 2
    Electronic Resource
    Electronic Resource
    Carbon acquisition strategies for marine macroalgae (1988)
    Springer
    Marine biology 97 (1988), S. 295-300 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A model system was developed to analyse differences in carbon acquisition strategies among macroalgae. During photosynthesis in a limited volume of seawater the capability of the algae to assimilate inorganic carbon as well as to change the alkalinity of the seawater was analysed. These properties were then related to the status of the carbonate equilibrium system of the seawater. The experimental system was assumed to simulate the conditions in the boundary layer during periods of low water exchange or high intensity irradiations. Fundamental differences were found between different algal classes, suggesting that capabilities to adapt to specific environmental conditions may be connected with dissimilarities in carbon acquisition strategies. In general, green algae were able to reach the highest pH (10.8 at 5°C), and thus to achieve the highest reduction in the level of inorganic carbon via a simple HCO3 −/OH− ion exchange process. For brown algae, pH increases due to carbon uptake never exceeded pH 9.7 (9.5 in a saltwater scale). In spite of this, members of the Fucaceae (littoral brown algae) were able to extract almost all of the dissolved inorganic carbon (DIC). This was achieved through a gradual decrease in the alkalinity of the enclosed water, so that the carbon assimilation could continue without any concomitant increase in pH. For red algae, the specific response was an increase in the level of inorganic carbon. Thus, for this algal class, no specific strategy for handling a shortage of inorganic carbon was documented. Within each algal class, differences in pH and DIC compensation points could be related to differences in the depths at which the algal species occurred. This paper also introduces a low cost and convenient method of analysing DIC in seawater.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00391315
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  • 3
    Electronic Resource
    Electronic Resource
    Changes in pH as a measure of photosynthesis by marine macroalgae (1988)
    Springer
    Marine biology 97 (1988), S. 287-294 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An automatically operated method for high precision measurements of steady-state photosynthesis by macroalgae was developed. Changes in pH and oxygen content of seawater passing the algae in a flowthrough system, could be measured with extremely high accuracy over very long periods of time. The method is especially suitable for measurements on flowthrough systems with high rates of water exchanges (i.e. short retention time), and can be used to study exchange processes for marine plants, animals and small ecosystems. Since the same measuring unit is used for several flowthrough chambers, the method is very suitable for comparisons between different species, or between differently pretreated specimens of the same species (e.g. in toxicological studies). The method was used to study the ratio: [oxygen production] to [CO2+H+ uptake] at different light intensities for several macroalgae belonging to different systematic groups and from different habitats. At lower photosynthetic rates this ratio was similar for all of the algae studied (1.17±0.02). For brown algae of the fucacean family, the ratio increased by 0.08 units at higher photosynthetic rates. This increase was thought to be related to the crassulacean acid metabolism (CAM)-like strategies connected to these algae. For all other algae studied, the ratio remained constant or decreased slightly (at most by 0.04 units) at higher photosynthetic rates. The relations between the abovementioned ratio and the photosynthetic quotient are discussed on a theoretical basis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00391314
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  • 4
    Electronic Resource
    Electronic Resource
    Immune complex induced experimental colitis: beneficial effect of sulphasalazine in rabbits (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Alimentary pharmacology & therapeutics 4 (1990), S. 0 
    Details
    ISSN: 1365-2036
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Experimental colitis was induced in rabbits by exposing the colon mucosa to 1% formalin followed by i.v. injections of soluble immune complexes made with antigen in excess. The animals were preimmunized with Esherichia coli 014:K7:H — inducing antibodies cross-reactive to intestinal epithelium.Animals with this colitis were divided in two groups. One group was treated with sulphasalazine and the other was given vehicle only. Sulphasalazine was administered daily at 125.5 μmol (50 mg) per kg body weight. The administration was started at the same day as the colitis was initiated. At Day 6, 13 and 30 following induction of colitis, biopsies were sampled and histologically evaluated. Inflammation was assessed by scores for inflammatory cells, crypt distortion, decreased crypt number and presence of crypt abscesses, thus corresponding to the picture seen in humans. A statistically significant lower score of inflammation was seen on Day 6 and 13 (P 〈 0.01) and on Day 30 (P 〈 0.05) following induction of colitis in animals treated with sulphasalazine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2036.1990.tb00470.x
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  • 5
    Electronic Resource
    Electronic Resource
    Experimental colitis induced by dextran sulphate sodium in mice: beneficial effects of sulphasalazine and olsalazine (1998)
    Oxford UK : Blackwell Science Ltd
    Alimentary pharmacology & therapeutics 12 (1998), S. 0 
    Details
    ISSN: 1365-2036
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Animal models of inflammatory bowel disease are artificial and more or less representative of human disease. However, the dextran sulphate sodium (DSS) induced intestinal inflammation model has recently been shown to fulfil some pathological criteria for an adequate experimental model.〈section xml:id="abs1-2"〉〈title type="main"〉Aim:To determine whether this form of experimental intestinal inflammation responds to established therapy used for human inflammatory bowel disease.〈section xml:id="abs1-3"〉〈title type="main"〉Methods:DSS was used to induce intestinal inflammation in conventional Balb/c mice and athymic nu/nu CD-1(BR) mice, and the well-documented 5-aminosalicylic acid (5-ASA) based anticolitis drugs sulphasalazine (SASP) and olsalazine (OLZ) were used to study therapeutic effects. Parameters which have been shown to reflect DSS-induced intestinal inflammation (body weight, colon length, spleen weight, diarrhoea, and rectal bleeding) were measured in the Balb/c mice.〈section xml:id="abs1-4"〉〈title type="main"〉Results:Significant amelioration was seen on these parameters after different treatment protocols. Survival in nu/nu CD-1 mice was studied, and after 16 days a death rate of 50% was noted in the DSS group. SASP (100 mg/kg/day) and OLZ (50 mg/kg/day) significantly prolonged the survival to 29 and 38 days, respectively. SASP and OLZ showed a dose-dependent effect in the range between 10 and 100 mg/kg/day, doses closely corresponding to those used in humans.〈section xml:id="abs1-5"〉〈title type="main"〉Conclusions:SASP and OLZ are able to ameliorate the DSS-induced intestinal inflammation. The dose-response patterns suggested that the active therapeutic moiety for the two drugs appears to be mainly the liberated 5-ASA molecule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2036.1998.00357.x
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  • 6
    Electronic Resource
    Electronic Resource
    Affinity, capacity and oxygen sensitivity of two different mechanisms for bicarbonate utilization in Ulva lactuca L. (Chlorophyta) (1999)
    Oxford, UK : Blackwell Science Ltd.
    Plant, cell & environment 22 (1999), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Ulva lactuca, collected on the west coast of Sweden at the end of May, was able to utilize the HCO3− pool of seawater only through extracellular dehydration via carbonic anhydrase, followed by uptake of the CO2 formed. A decrease in the CO2 supply via this mechanism resulted in the gradual development of an additional method of HCO3− utilization, namely a direct uptake of HCO3−. Photosynthesis could then be supported by either a ‘HCO3− dehydration mechanism’ or a ‘HCO3− uptake mechanism’. Through selective inhibition of either of these mechanisms, the physiological properties of the other could be assessed. These properties suggest that the HCO3− uptake mechanism of U. lactuca is important under conditions when low concentrations of inorganic C, high pH and high external O2 concentrations would limit photosynthesis supported by the HCO3− dehydration mechanism. Such conditions may occur during intense irradiation of the alga in rockpools or in shallow bays with low rates of water exchange. The results are discussed in relation to a possible coupling between mechanisms for inorganic C acquisition and cell structure (or even morphology) of green macroalgae. They also illustrate some necessary precautions when using Michaelis–Menten kinetics for estimations of Vmax and K1/2 values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1999.00470.x
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  • 7
    Electronic Resource
    Electronic Resource
    Adaptations by macroalgae to low carbon availability. II. Ultrastructural specializations, related to the function of a photosynthetic buffer system in the Fucaceae (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 12 (1989), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Among the brown algae, species of the Fucaceae (Pelvetia, Fucus and Ascophyllum) were found to have a ‘photosynthetic buffering’ system, allowing the algae to carry out oxygen production without a concomitant uptake of inorganic carbon. This system was not found in other brown algae examined (e.g. Halidrys, Laminaria and Desmarestia) nor in 16 examined species of red and green algae. Pelvetia, Fucus and Ascophyllum belong to the littoral algae which are periodically emersed. In the Fucaceae, the meristodermal cells were found to have a special organization of organelles. Towards the outer cell wall there was a prominent layer of mitochondria while the chloroplasts were concentrated towards the inner and side walls. Between the mitochondria and the chloroplasts there was a large number of physodes. This arrangement of organelles was not found in the other brown algae examined nor in red or green algae. The significance of this organization of the mitochondria is discussed in connection with the function of the ‘photosynthetic buffering’ system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1989.tb01638.x
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  • 8
    Electronic Resource
    Electronic Resource
    Adaptations by macroalgae to low carbon availability. I. A buffer system in Ascophyllum nodosum, associated with photosynthesis (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 12 (1989), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The exchange of CO2, H+ and O2 between seawater and the intertidal brown macroalga Ascophyllum nodosum (L.) Le Jolis were measured in a flowthrough system. While the algae were kept in darkness, seawater with artificially increased alkalinity and pH at 9.85, was alternated with ‘normal’ seawater at pH 8.0. A proton buffering system, with capacity to release and reabsorb about 20 μmol protons per gram alga (fresh weight) was revealed. As the algae were returned to the ‘normal’ seawater, the kinetics of proton reabsorbtion indicated that a proton uptake was gradually induced. This proton uptake, which was not connected to ion exchange in the cell wall, reached its maximum after 12 h. If subjected to high alkalinity seawater in the light, A. Nodosum for a certain period of time was capable of carrying out O, evolution in excess of the import of inorganic carbon. This ‘photosynthetic buffering capacity’ amounted to about 17 μmol O; per gram alga. Besides depending on a buffer of photorcducible substances, this ‘photosynthetic buffering capacity’ appeared to be functionally connected with the proton buffer. The time course for the discharge of the ‘photosynthetic buffer system’ and for the reabsorbtion of protons into the proton buffer (about 6h for 90× of the capacity at a temperature of 6°C) suggests that the ‘photosynthetic buffer system’ has a functional importance in the adaptation of A. nodosum to intertidal regions. The function of the buffer system is discussed in relation to the crassulacean acid metabolism (CAM)-like characteristics recently shown for the intertidal brown algal family Fucaceae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1989.tb01637.x
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  • 9
    Electronic Resource
    Electronic Resource
    Two modes of bicarbonate utilization in the marine green macroalga Ulva lactuca (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 18 (1995), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The green marine macroalga Ulva lactuca L. was found to be able to utilize HCO3− from sea water in two ways. When grown in flowing natural sea water at 16°C under constant dim irradiance, photosynthesis at pH8.4 was suppressed by acetazolamide but unaffected by 4,4′-diisothiocyanostilbene-2,2′-disulphonate. These responses indicate that photosynthetic HCO3− utilization was via extracellular carbonic anhydrase (CA) -mediated dehydration followed by CO2 uptake. The algae were therefore described as being in a ‘CA state’. If treated for more than 10 h in a sea water flow-through system at pH9.8, these thalli became insensitive to acetazolamide but sensitive to 4,4′-diisothiocyanostilbene-2,2′-disulphonate. This suggests the involvement of an anion exchanger (AE) in the direct uptake of HCO3−, and these plants were accordingly described as being in an ‘AE state’. Such thalli showed an approximately 10-fold higher apparent affinity for HCO3− (at pH9.4) than those in the ‘CA state’, while thalli of both states showed a very high apparent affinity for CO2. These results suggest that the two modes of HCO3− utilization constitute two ways in which inorganic carbon may enter the Ulva lactuca cells, with the direct entry of HCO3−, characterizing the ‘AE state’, being inducible and possibly functioning as a complementary uptake system at high external pH values (e.g. under conditions conducive to high photosynthetic rates). Both mechanisms of entry appear to be connected to concentrating CO2 inside the cell, probably via a separate mechanism operating intracellularly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1995.tb00378.x
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  • 10
    Electronic Resource
    Electronic Resource
    Photosynthesis and respiration in the alga Ahnfeltia plicata in a flow-through system (1987)
    Springer
    Marine biology 96 (1987), S. 409-412 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthesis and respiration in Ahnfeltia plicata (Huds.) Fries (Gigartinales) was measured in a seawater flowthrough system at different temperatures, salinities and photon flux densities (PFD). The exchanges of dissolved oxygen and inorganic carbon were continuously recorded with an oxygen probe and a pH electrode measuring variation in CO2−HCO 3 - equilibrium as pH changes. Highest apparent photosynthesis at moderate photon flux density (PFD 50 μE m-2 s-1) was found at 15°C and 33‰ S. Photosynthesis was measured up to PFD 500 μE m-2 s-1 and no light saturation was documented. In the present experimental set-up, with continuous supply of fresh seawater, the number of limiting factors during photosynthesis measurements is reduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00412525
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