| 1. |
- Nilsson, Kjell, et al.
(författare)
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A General Method for the Immobilization of Cells with Preserved Viability
- 1983
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Ingår i: Applied Microbiology and Biotechnology. ; 17, s. 319-326
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Tidskriftsartikel (refereegranskat)abstract
- Microbial, algal, plant and animal cells have been immobilized, with preserved viability, by entrapment in various matrices according to a new bead polymerization technique. The cell polymer/monomer mixture is kept suspended in a hydrophobic phase such as soy, paraffin, or silicon oil, tri-n-butylphosphate, or dibutyphtalate, which is compatible with the cells. The various monomers or polymers tested include agarose, agar, carrageenan, alginate, fibrin, and polyacrylamide. Furthermore, by adjustment of the stirring speed of the suspension, beads of desired diameter can easily be obtained. The entrapped cells are fully viable and biosynthetically active.
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| 2. |
- Ohlson, Sten, et al.
(författare)
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Steroid Hydroxylation Using Immobilized Spores of Curvularia lunata Germinated in situ
- 1980
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Ingår i: European Journal of Applied Microbiology and Biotechnology. - 0171-1741. ; 10, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Spores of Curvularia lunata were immobilized in polyacrylamide granules and in calcium alginate beads (2–3 mm in diam.). Germination of the spores, initiated by the addition of nutrients, resulted in an even distribution of mycelium throughout the beads after 48 h. Such beads were used for the conversion of cortexolone to cortisol by steroid-11-hydroxylation. In order to improve the steroid transforming ability several parameters were studied. It was found that preparations based on calcium alginate gave the best results. The possible merits of immobilizing spores rather than vegetative cells, followed by in situ germination are discussed also for other microorganisms and immobilization processes.
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| 3. |
- Lexell, Jan, et al.
(författare)
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Distribution of different fibre types in human skeletal muscles. A statistical and computational model for the study of fibre type grouping and early diagnosis of skeletal muscle fibre denervation and reinnervation
- 1983
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Ingår i: Journal of the Neurological Sciences. - 1878-5883 .- 0022-510X. ; 61:3, s. 301-314
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Tidskriftsartikel (refereegranskat)abstract
- To define fibre type grouping in terms of random and non-random arrangements of the two fibre types, type 1 (ST) and type 2 (FT), we adopted the measure of counting the number of "enclosed fibres". The statistical properties of the number of enclosed fibres, and the number and size of groups of enclosed fibres were studied in computer-simulated muscle cross-sections, using a model based upon hexagonal-shaped fibres. The effects on the results of differences in the sizes of the muscle fibres were considered. The applicability of the model, and the derived results and methods of analysis were tested on 10 samples from a cross-section of a whole human muscle. The results show that the model can be applied to various shapes and sizes of muscle samples and various sizes of muscle fibres. The number of enclosed fibres within a muscle sample is the best of the three measures of non-randomness considered. A test is also described for assessing whether or not the observed number of enclosed fibres is random at a given significance level.
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| 4. |
- Abdul-Rahman, A, et al.
(författare)
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Local cerebral blood flow in the rat during severe hypoglycemia, and in the recovery period following glucose injection
- 1980
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772. ; 109:3, s. 307-314
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Tidskriftsartikel (refereegranskat)abstract
- In order to assess the influence of severe hypoglycemia on local cerebral blood flow (1-CBF) artificially ventilated rats, maintained on 70% N2O, were injected with insulin to provide either an EEG pattern of slow-wave polyspikes, or cessation of spontaneous EEG activity for 5, 15 or 30 min ("coma"). In other animals, glucose was injected at the end of a 30 min period of "coma" and 1-CBF was measured after recovery periods of 5, 30, 90, or 180 min. Local CBF was measured autoradiographically with 14C-iodoantipyrine as the diffusible tracer. In the slow-wave polyspike period 1-CBF was increased in most of the structures studied, and reached values that were 1.4 to 3.2 times greater than control. In many structures, cessation of EEG activity was accompanied by a further increase in 1-CBF, with some structures (thalamus, hypothalamus, pontine gray, and cerebellar cortex) showing flow rates of 400--500% of control. The increase in 1-CBF was unrelated to arterial hypertension, hypercapnia, or hypoxia. 5 min after glucose injection the hyperemia persisted in only some of the structures studied; in others, the 1-CBF were close to, or below, control values. During the subsequent recovery period 1-CBF was markedly reduced with some structures (cerebral cortical areas, hippocampus, and caudate-putamen) showing flow rates of only 20--35% of control. In others, notably pontine gray and cerebellar cortex, secondary hypoperfusion was never observed. The hypoperfusion was unrelated to arterial hypertension, hypocapnia, or increase in intracranial pressure. It is concluded that, like hypoxia and ischemia, substrate deficiency due to hypoglycemia is accompanied by vasodilatation in the brain. Furthermore, like long-lasting ischemia, severe hypoglycemia is followed by a delayed hypoperfusion syndrome that, by restricting oxygen supply, may well contribute to the final cell damage incurred.
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| 5. |
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| 6. |
- Adlercreutz, Patrick, et al.
(författare)
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Oxygen supply to immobilized cells : 1. Oxygen production by immobilized Chlorella pyrenoidosa
- 1982
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Ingår i: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229. ; 4:5, s. 332-336
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen supply at high cell densities of aerobic organisms is a great problem in immobilized cell preparations. To investigate the possibility of in situ oxygen generation the alga Chlorella pyrenoidosa was immobilized on alginate beads. The conditions for optimal oxygen production were investigated and in long term experiments the preparations were successful for at least 30 days.
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| 7. |
- Adlercreutz, Patrick, et al.
(författare)
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Oxygen supply to immobilized cells : 2. Studies on a coimmobilized algae-bacteria preparation with in situ oxygen generation
- 1982
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Ingår i: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229. ; 4:6, s. 395-400
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Tidskriftsartikel (refereegranskat)abstract
- A coimmobilized mixed culture of algae, Chlorella pyrenoidosa, and bacteria, Gluconobacter oxydans, has been studied. The conversion of glycerol to dihydroxyacetone(1,3-dihydroxy-2-propanone), catalysed by the bacteria, was used to indicate the oxygen supply in the immobilized preparation. The oxygen produced by the algae in the coimmobilized preparation was used by the bacteria more effectively than when the cells were immobilized separately and mixed within the reactor. A preparation consisting of only bacteria and no algae was much less effective. The coimmobilized preparation was used in the continuous production of dihydroxyacetone for six days without any significant loss of activity.
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| 8. |
- Adlercreutz, Patrick, et al.
(författare)
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Oxygen supply to immobilized cells - 3. Oxygen supply by hemoglobin or emulsions of perfluorochemicals
- 1982
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Ingår i: European Journal of Applied Microbiology and Biotechnology. - 0171-1741. ; 16:4, s. 165-170
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen supply is a critical point in technical processes when aerobic cells are used in immobilized preparations. This report concerns the use of hemoglobin or emulsions of perfluorochemicals (completely fluorinated organic compounds) to carry oxygen to immobilized cells. Both methods work well and do not seem to harm the cells. The perfluorochemical method of improving oxygen supply showed a higher operational stability than the hemoglobin method.
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| 9. |
- Adlercreutz, Patrick, et al.
(författare)
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Oxygen supply to immobilized cells - 4. Use of p-benzoquinone as an oxygen substitute
- 1984
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Ingår i: Applied Microbiology and Biotechnology. - 0175-7598. ; 20:5, s. 296-302
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen supply is a critical point in technical processes when aerobic cells are used in immobilized preparations. In this study p-benzoquinone is used as a substitute for oxygen in the oxidation of glycerol to dihydroxyacetone by immobilized Gluconobacter oxydans cells. The reaction rate was much higher when p-benzoquinone was used compared to when oxygen was used. In an experiment with free cells p-benzoquinone gave a rate more than four times that of oxygen, and with immobilized cells the difference was even greater. p-benzoquinone is more effective than oxygen because it gives a higher maximal reaction rate (the reason for this fact is discussed) and because it is more soluble in water than oxygen. The operational stability of the process is comparatively good. In one experiment the productivity decreased from 60 to 10 mmol/h·g over an 8-day period when p-benzoquinone was used. When oxygen was used in a similar experiment the productivity decreased from 14 to 6 mmol/h·g. The byproduct formed from p-benzoquinone, hydroquinone, can be oxidized to p-benzoquinone which can be re-used. Seven succesive regenerations of p-benzoquinone were performed without any loss of efficiency.
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| 10. |
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