The eutrophication history of Lake Särkinen,Finland and the effects of lake aeration

Lake Särkinen is a small lake in the parish of Sotkamo, Finland. The lake has been strongly enriched since the middle of the 1960's. The nutrient load was greatly reduced in 1969 and aeration was started in 1980.According to ²¹⁰Pb dating sediment accumulation rates are lowest (ca 9 mg cm^–2 yr^–1) between about 1920 and 1960. Thereafter they rise to the present level (22 mg cm^–2 yr^–1).The diatom flora indicates rising eutrophy from the beginning of the 20th century and again in the 1950–60's period. The surface sample, which represents the 1980's, shows a change in diatom flora indicating lake recovery. Changes in nutrient concentrations and in the solubility of phosphorus in the sediments indicate signs of oxygen depletion.     

Effect of hydrocortisone on catecholamines and the enzymes synthesizing them in the developing sympathetic ganglion

Summary Newborn rats were daily injected with 0.2 mg hydrocortisone acetate for seven days. They were killed 1, 7 or 21 days after the last injection, together with untreated controls. Hydrocortisone caused a great increase in the number of the small, intensely fluorescent (SIF) cells and the appearance of similar small cells with intense immunohistochemical reactions for tyrosine hydroxylase (TH), dopamine--hydroxylase (DBH) and phenylethanolamine (noradrenaline)N-methyltransferase (PNMT) in the superior cervical ganglion. At the same time, the adrenaline content and the PNMT activity of the ganglion greatly increased, while no significant changes were observed in the dopamine or noradrenaline content or TH or DBH activity. All these changes essentially disappeared after a recovery period of seven or 21 days.It is concluded that hydrocortisone causes a temporary increase in the number of SIF cells by causing a synthesis of TH, DBH and PNMT in previously existing small, non-fluorescent cells, which start to synthesize and store adrenaline, thus becoming intensely fluorescent SIF cells. These SIF cells are different from the normal SIF cells of the same ganglion, most of which appear at a later stage of postnatal development when response to hydrocortisone is lost, which contain TH but neither DBH nor PNMT, and which permanently remain in the ganglion.     

Effects of different gibberellins on elongation growth under short day conditions in seedlings of Salix pentandra

Fifteen different gibberellins (GA's) were tested for their ability to induce elongation growth under short day conditions in seedlings of Salix pentandra L. GA's were applied either to the apex or they were injected into a mature leaf. GA₃ was highly active and also GA₄₊₇ and GA₄ showed high activity. GA₁, GA₂, GA₅, GA₉, GA₁₃, GA₂₀, GA₃₆ and GA₄₇ showed moderate activity. GA₁₆, GA₁₇, GA₂₇ and GA₄₁ exhibited low or no activity in doses up to 10 μg per plant. In general, a better growth response was obtained with an application to the apex than with an injection into the leaf.     

Induction of aryl hydrocarbon hydroxylase in human fetal liver cell and fibroblast cultures by polycyclic hydrocarbons

Cells originating from the human fetal liver and grown as a primary monolayer culture for 4 to 11 days contain an enzyme system that metabolizes benzo(α) pyrene. The basal level of the enzyme varied about three-fold. The activity was increased from 1.4- to 5.1-fold by the exposure of cells for 24 hours to benz(α) anthracene, the magnitude of increase depending on the amount of inducer, on the individual cell batch studied and on the stage of cell growth. Also 3-methylcholanthrene, but not benzo(α)pyrene, induced the enzyme activity in fetal liver cell cultures at concentrations used. Fibroblast cultures derived from the human fetal lung or skin exhibited less benzo(α)pyrene metabolism and the inducibility of the enzyme activity was less marked than in hepatic cell cultures.     

Histochemical correlates of cold-induced trans-synaptic induction in the rat superior cervical ganglion

Synopsis The effect of prolonged pre-ganglionic activity induced by exposure to cold (5°C) was studied in intact and decentralized superior cervical ganglia of rats. Intact and decentralized ganglia of rats kept at room temperature served as controls. catecholamines were demonstrated histochemically using the formaldehyde-induced fluorescence method. The intensity of the fluorescence of the nerve cell bodies was estimated both visually and photometrically.Decentralization in itself had no effect on the intensity of the cell bodies for up to 16 days. Exposure to cold had no effect on the decentralized ganglia but caused a marked increase in the fluorescence intensity of some nerve cells of the intact ganglia, indicating that the increased fluorescence was mediated by the pre-ganglionic nerves. The increase lasted for the whole 16-day-length of exposure to cold.It is suggested that the observed change in the fluorescence intensity reflects an increase of the enzymes tyrosine hydroxylase and dopamine--hydroxylase, and thus represents a histochemical correlate of trans-synaptic induction.Sigrid Jusélius Foundation Research Fellow in the Department of Anatomy, University of Helsinki, April–July 1973.     

Experimental control of flowering and vivipary in timothy (Phleum pratense)

Environmental and hormonal control of flowering and vivipary in four Norwegian timothy ( Phleum pratense L.) cultivars has been studied in phytotron and by aseptic culture of inflorescence explants. The critical photoperiod for flowering increased with increasing temperature (12–18°C) and it was 13 to 15 h for the southern and 14 to 16.5 h for the northern cultivars. Diurnal temperature fluctuation significantly stimulated flower formation compared to the corresponding constant temperature treatment. Plants grown in 16-h photoperiod contained normal sexual flowers, but a high percentage of spikes developed in 12- or 14-h photoperiod contained viviparous plantlets. One- to four-weeks in continuous light before treatment with 12-h photoperiod increased the number of spikes per plant, but did not enhance the frequency of vivipary. Experiments with aseptic cultures showed that generative versus vegetative development of timothy inflorescence was affected by plant hormones. Kinetin stimulated the vegetative development and induced proliferation both in inflorescence initials and in spikelets isolated at heading time.     

The DNA binding of benzo[alpha]pyrene metabolites catalysed by rat lung microsomes in vitro and in isolated perfused rat lung.

When [³H]benzo[a]pyrene is incubated in vitro together with DNA, NADPH and rat lung microsomes, covalent binding of benzo[a]pyrene (BP) metabolites to DNA occurs. These metabolite-nucleoside complexes can be resolved into several distinct peaks by elution of a Sephadex LH-20 column with a water-methanol gradient. 3-Methylcholanthrene (MC) pretreatment of animals induces the total covalent binding in vitro several-fold and increases the amounts of at least five metabolite-nucleoside complexes associated with the 7,8-diol-9,10-epoxidcs, the 7,8-oxide or quinones oxygenated further, the 4,5-oxide and phenols oxygenated further. These increases correspond well with the increases in the production of both non-K-region and K-region metabolites of BP by lung microsomes, as determined by highpressure liquid chromatography (HPLC). On the other hand, when [³H]BP is metabolized in isolated perfused rat lung, only the peak representing the 7,8-diol-9,10-epoxide bound to nucleoside(s) is readily detectable and then only in lungs from MC-treated animals. The extent of binding of BP metabolites to lung DNA is very low, about 0.0004% of the total dose applied to the perfusion medium; more than 60% of this can be accounted for by the binding of the 7,8-diol-9,10-epoxides to nucleoside(s). It is suggested that the further metabolism leading to metabolites not available to covalent binding, (e.g. conjugation) of primary BP metabolites in the intact tissue is responsible for the differences in the metabolite-nucleoside patterns observed in vivo, as compared with microsomal metabolism in vitro.     

Population fluctuations of the wood lemming<Emphasis Type="Italic">Myopus schisticolor</Emphasis> in eastern and western Finland

Olavi Eskelinen, Pertti Sulkava and Risto Sulkava From 1982 to 2003 we studied fluctuations in populations of the wood lemmingMyopus schisticolor (Liljeborg, 1844) in the Heinävesi (eastern Finland) and Keuruu regions (western Finland) by counting field signs and dead animals in standardized field surveys. We compared the population fluctuations of lemmings to those of other voles, owls and small mustelids in these regions. The lemming population in Heinävesi fluctuated regularly in 3-year cycles and in synchrony with the field vole population. Populations of owls also fluctuated in synchrony with wood lemming and field vole populations. In the Keuruu region, oscillations in the wood lemming population were irregular, and neither lemming and vole populations nor lemming and owl populations were correlated. Although direct mechanistic evidence is lacking, specialist predators such as weasels and owls probably cause the cyclicity in the field vole and wood lemming populations in the Heinävesi area. On the other hand, scarcity of high-quality habitats, unfavourable winter weather conditions and generalist predators may prevent the development of cyclicity in the wood lemming population of Keuruu.