Showing papers by "University of Bergen published in 1968"

Studies on DNA-dependent RNA polymerase from Escherichia coli. 1. The mechanism of polyamine induced stimulation of enzyme activity.

Abstract: The effect of spermidine and spermine on the synthesis of RNA in vitro by RNA-polymerase from Escherichia coli has been studied. Spermidine did not change the pH optimum of the reaction. With a high ratio of DNA to polymerase in the reaction mixture, maximal stimulation was observed at a spermidine concentration of 0.8 mM and spermine concentration of 0.3 mM. Under these conditions spermidine increased the initial velocity and the extent of the reaction. When the weight ratio of DNA to enzyme was low, the same concentration of spermidine increased the extent, but not the initial velocity of the reaction. If the reaction was primed by denatured DNA, spermidine did not stimulate the synthesis of RNA. A slight inhibition was observed at low concentrations of the template. Spermidine counteracted the inhibitory effect of RNA added to the reaction mixture before the start of the reaction. Models based on these results are proposed to explain the mechanisms of polyamine induced stimulation of RNA polymerase activity.

Horizontal and vertical exchanges and diffusion in the water masses of the oslo fjord

Abstract: 1. Both advective and diffusive processes are agents in the water exchange of the inner Oslo Fjord. The estuarine circulation is the most important form of water exchange. Analysis on a monthly basis has revealed great seasonal variations with peaks in spring and fall, and slack periods in winter and summer. The estuarine circulation is predominantly limited to the upper 20 m, comprising the zone of brackish water. 2. To a lesser extent also the entire body of sea-water in the fjord is involved through vertical eddy diffusion. Seasonally varying density conditions in the outer fjord prevent a continuous replenishment of the deeper sea-water layers. This water is renewed intermittently, and to a varying extent, by heavier water flowing in over the sill. The process takes place about every winter and appears to be controlled by the strength and duration of the seasonal northerly winds. 3. Vertical eddy diffusion coefficients are computed in the sea-water phase on the basis of the salt budget. In the upper layers the vertical diffusion is determined from harmonic analysis of the heat wave resulting from surface heating and cooling. 4. Horizontal exchange in the upper layers also rises from diffusive processes. Tidal currents, however weak, are the main generating agent of turbulence, but also wind drift has significant effects when present. Horizontal eddy diffusion is determined from the budget of orthophosphate in winter. Diffusion coefficients are of the order 106 cm2/sec, but reach 107 cm2/sec in Drobak Sound. 5. Drastic forms of water exchange take place under influence of fresh winds prevailing for more than four days. Both pure wind drift and secondary density currents occur.

Electron microscopic studies of unfertilized and fertilized eggs from marine teleosts

Abstract: Ripe eggs of several species of marine teleostean fishes were studied in the unfertilized state and after insemination. The ultrastructure of the fish egg was investigated and several species-specific differences were discovered in the surface layers of the ripe egg. The electron microscopic changes found upon fertilization of the egg are discussed.

Movement of Amyloplasts in the Root Cap Cells of Geotropically Sensitive Roots

Abstract: The root cap of Lepidium sativum under our culture conditions was found to contain 7 (or occasionally 8) storeys of starch-containing cells. In the youngest one (or two) of these storeys the amyloplasts are small and the cells appear embryonic. In the 6 non-embryonic storeys the amyloplasts are large. Upon inversion of the root, the amyloplasts in the 3 youngest of the 6 non-emhryonic storeys start falling toward the opposite end of the cell at about 72 μ per h (at 21 C), hut they maintain this speed for only 6 to 12 min, after which they virtually come to a stop. As a result, it takes 10 to 12 min before any of the amyloplasts get approximately as close to the ceiling as they were to the floor before the inversion; and this is true only of the 2 youngest of the non-embryonic storeys. When the root is placed horizontal, whether coming from the normal or the inverted position, the amyloplasts reach the lower, longitudinal wall in 15 min or less. The positions of the amyloplasts in the cells of the 3 oldest starch-containing storeys are erratic and show little, if any, dependency on the preceding time of inversion.

Nonbanded fibrils of collagenous nature in human periodontal connective tissue.

Abstract: Human teeth with adhering periodontal tissues were obtained and processed for electron microscopy. Thin sections were cut through cementum and adjacent soft tissue. An increased occurrence of nonbanded fibrils was observed near the root surface adjacent to marginal areas of chronic inflammation. Bundles of fine filaments protruded from the cementum surface as extensions of cross-banded matrix fibrils. Nonbanded filaments were seen between collagen fibrils in the periodontal ligament as well as in direct continuation of such fibrils. In areas were beading of the filaments could be distinctly observed, the periodicity of the beading often corresponded to the periodicity of collagen cross banding. The number of filaments present in various sites appeared to be inversely proportional to the amount of intact collagen fibrils remaining. The location and appearance of the nonbanded structures indicate that they to a large extent represent partially decomposed collagen fibrils.

Occurrence and Metabolism of Indoleacetaldehyde in Certain Higher Plant Tissues Under Aseptic Conditions

Abstract: Qualitative and quantitative evidence based on thin-layer chromatography and the Avena curvature test respectively, are presented for the normal and natural occurrence of indoleacetic acid (IAA), indoleacetaldehyde (IAAld) and tryptophol in the etiolated shoots of Pisum sativum, grown, harvested and extracted under aseptic conditions. Non-aseptic pea shoots contain much more IAA and IAAld than aseptic ones. Extraneous contribution to the indole pool of pea plants grown under non-sterile atmosphere, other than by the inherent agency of the plant itself, is therefore not excluded. Indoleacetaldehyde metabolizing activity of the tissues and cell-free preparations of etiolated Avena seedlings, leading to the production of IAA and tryplophol, is unaffected by the antibiotics actinomycin and streptomycin over a wide range of concentrations. Formation of IAA from IAAld is suppressed by a small degree (10 to 15 %) by chloramphenicol. But this antibiotic does not influence the concurrent production of tryptophol. It is deduced that epiphytic bacteria play little role in the transformation of IAAld to IAA and tryptophol by Avena tissues.

The “Point of no Return” Concept in Cell Division. The Effects of Some Metabolic Inhibitors on Synchronized Chlorella pyrenoidosa

Abstract: The coarse of growth and cell division in synchronized cultures of Chlorella pyrenoidosa was studied after the addition of metabolic inhibitors at differing times during the cell cycle (14 h light - 10 h darkness with nitrate as nitrogen source. 12 h light: 12 h darkness with urea as nitrogen source). Dinitrophenol (DNP) added to a final concentration of 0.3 mM at any time in the synchronization cycle, the compound remaining in the suspension from the time of addition to the end of the dark period, inhibited spore formation completely. Growth measured as increase in cell volume was less sensitive to the action of the inhibitor. Chloramphenicol (CAP) added dining the 0–5 h interval to a final concentration of 0.1 mM resulted in 80 per cent inhibition of cell division. Similar treatment started at successive times thereafter resulted in a gradual decrease of the inhibition. Treatment at the 14th hour and during the dark period did not affect the sporulation. Similar experiments with 0.9 mM puromycin added at various times during the illumination period gave almost complete inhibition of cell division, while the growth was reduced by only 25 per cent. para-Fluorophenylalanine (p-FPhe) at 3.3 × 10−2 mM stopped cell division nearly completely irrespective of addition time in the light period. Addition during the dark period also prevented an increase in the number of tree cells. In this case about half of the cells produced spores which were not released. It is concluded that DNP inhibits all stages of preparation for cell division, as well as the division process itself. With CAP a genuine transition point of preparation for cell division was observed, although its interpretation as related to protein synthesis is somewhat uncertain. With puromycin and p-FPhe no transitions were observed.

Cardiovascular investigations on hedgehogs during arousal from the hibernating state.

Abstract: Haemodynamical changes were followed in hedgehogs during arousal from the hibernating state. The temperature in the anterior part of the body increased prior to the temperature in the posterior part. Cardiac output—measured with implanted electromagnetic probes—rose faster than the heart rate in early arousal, but slower in the later phases. Arterial pressures reached maxima at a temperature of 20—30° C in the neck. The decrease in peripheral resistance was greatest in the first part of arousal and was largely due to the fall in blood viscosity with temperature. There is usually no further decrease in hindrance above 15—20° C. The dilation of posterior vessels were compensated by constrictions in regions already warmed. Due to the fall in viscosity of blood with temperature, warmer organs are more easily circulated than colder portions. This and other autoregulatory effects of a physical nature are discussed.

Temperature effects on the viscosity of blood and the aorta distension from a hibernator, Erinaceus europaeus L.

Abstract: Hedgehog blood at all temperatures showed higher apparent viscosity than most other mammals and exhibited pseudoplastic characters at low rates of shear. In contrast, serum never showed shear rate dependence. Red cells in serum or Ringer's solution had less shear rate dependence than did blood corpuscles suspended in plasma. The apparent viscosity of a sample doubled when the temperature fell from 34° to 6° C. The change in viscosity found in different blood samples withdrawn at 6°, 20° and 34° C during arousal from hibernation, was greater than the reduction found in one sample over the same temperature range. The cross-section of the aorta increased with falling temperatures from 34° to 6° C, but the elastic properties of the vessel remained relatively unchanged. A deviation from Hooke's law is evident, but it was not great within the normal homeostatic pressure range. Distension with increasing pressure was a little larger for vessels from non-hibernating than for hibernating animals. The hindrance of the aorta in the hibernating state was increased by a factor of 1.9 compared to the value of the non-hibernating state. If there hypothetically was no distension with falling temperature, the increase in hindrance would be about 2.5.