Pekka Lähdesmäki

High nitrogen deposition causes changes in amino acid concentrations and protein spectra in needles of the scots pine (Pinus sylvestris).

Growth of the Scots pine (Pinus sylvestris) suffered considerably in forests close to fur farms in western Finland, with the occurrence of winter time dieback in the youngest shoots and leading to a bush-like, flat crown canopy. One reason for this growth disturbance may be a serious imbalance in nitrogen metabolism caused by the extra N supply, emitted as NH3 from the dung of the animals. Total N and NH4+ concentrations in the needles and soluble nitrogen concentration in the soil increased considerably in the vicinity of the fur farms. The extra N in the needles was bound in the first place in arginine, the concentration of which increased 10(2)-10(3) fold compared with control trees, and to a lesser extent in glutamine and other amino acids. Alterations in the quantitative and qualitative protein patterns of the needles were obtained. The extra N increased the concentration of total soluble proteins, although it inhibited the formation of certain polypeptides (particularly in the areas of 30, 38, 50 and 65-90 kDa) which were possibly essential for the normal wintering processes. One reason for the winter time dieback in the high N area could thus be found in the altered protein profiles.

Soil enzymology: Role of protective colloid systems in the preservation of exoenzyme activities in soil

Abstract The effects of repeated freezing and thawing, heating and drying, changes in pH and the presence of various concentrations of ZnSO 4 and CuSO 4 (1–50gl −1 ) on the activities of selected soil enzymes (protease, cellulase and amylase) were studied in humus samples and their alkaline extracts from the humus layer of a grass-herb forest in Kiiminki, northern Finland. In order to elucidate the anticipated protective effect of the clay and humus colloids present in the soil in preserving the enzyme activities against changes in physical and chemical conditions, the enzyme activities were measured in untreated humus samples, their extracts and the protein fraction formed in Sephadex G-200 gel filtration using 0.5 mol 1 −1 Na 2 CO 3 -NaOH for elution. The fractions identified in gel filtration were: clay colloids (~200kDa mol. wt), proteins (~150kDa mol. wt), mucins (50–160kDa mol. wt) and humus colloids (5–50 kDa mol. wt). The enzyme activities were inhibited in the fractionated samples by freezing and thawing, heating and drying, changes in pH and the presence of zinc and copper sulphates, while they remained relatively constant in the original (untreated) humus samples. Dilution of the soil extract reduced K m from about 3.0 to 0.1 and V max from 5.0 to 1.5. The effects of the various treatments were relatively weak in the original humus samples, which suggests that the fractionation and dilution dismantle or weaken a protective mechanism probably built up by the clay and humus colloids present in the untreated and unfractionated samples and which enable soil to preserve its enzyme activities against certain environmental and other physico-chemical changes.

In vivo Chlorophyll fluorescence is not always a good indicator of cold hardiness

Summary This paper demonstrates that Chlorophyll fluorescence in vivo is not always a true indicator of plant cold hardiness. In this experiment, frost resistance and chlorophyll fluorescence of needles of Scots pine seedlings were followed under natural and controlled phytotron conditions during the most active cold hardening period.

Glutamyl‐Taurine Is the Predominant Synaptic Taurine Peptide

Abstract: Several taurine‐containing peptides have been identified from trichloracetic acid extracts of synaptosomes and their subcellular vesicles prepared from calf brain. These peptides contain aspartic and glutamic acids, serine and taurine, and are often present in an N‐acetylated form. The peptides were isolated as single spots by TLC. Glutamyl‐taurine was found to be the predominant structure when analyzed by fast atom bombardment (FAB) mass spectrometry.

Interaction of taurine, GABA and glutamic acid with synaptic membranes.

Abstract— Sodium‐independent but calcium‐dependent binding of taurine, GABA and glutamate to synaptic membranes from calf brain cortex is demonstrated. Binding constants of 1.5 μm for taurine, 46 μm for GABA and 45 μm for glutamate were obtained, being largely mixed with transport constants derived from the influx to empty membrane‐pouches (particularly in the case of GABA and glutamate), and in the case of GABA also with the non‐specific binding. Certain structural analogues of amino acids inhibited the binding, aspartate being the most potent inhibitor for glutamate, and β‐alanine for GABA and taurine, but KCN and 2,4‐dinitrophenol had no effect. The membrane‐attached [35S]taurine was divided by differential elution into easily extractable and firmly bound components.

Degradation products and the hydrolytic enzyme activities in the soil humification processes

Abstract Humification of spruce ( Picea abies ) needles, aspen ( Populus tremula ) leaves and pine-bog peat was studied with emphasis on the determination of the amounts of proteins, lipids, sugars, starch, amino acids, cellulose and lignin in fresh and decomposed litter materials. The concentrations of starch, proteins and free sugars decreased rapidly, that of total lipids more slowly and that of cellulose and lignin very slowly during the decomposition of spruce needles and aspen leaves. The proteins in the peat remained undecomposed for relatively long periods since most of the original N in 2 m deep peat was still largely preserved in the form of polymerized N. Celluiase and polyphenoloxidasc activities increased while proteolytic and lipase activities decreased during the decomposition of all the materials studied. Additionally caloric values of the litter and peat were also measured, and the results confirm the increase of caloric values during the humification.

MODELLING FROST RESISTANCE OF SCOTS PINE SEEDLINGS USING TEMPERATURE, DAYLENGTH AND PH OF CELL EFFUSATE

The annual course of frost resistance (LT50) and the pH of the cell effusate in needles of two-year-old Scots pine seedlings were monitored in a field experiment in Oulu, Northern Finland (65° N, 25° E) during 1995. The aim of the work was to to develop model to predict the annual variation in frost resistance by pH of the cell effusate and meteorological data. The seedlings were covered with a fibre cloth shelter which transmitted sufficient light for them to experience the photoperiod, but prevented the accumulation of snow over them. The shelter above the seedlings was removed at the beginning of May and erected again at the end of September. The seedlings were watered only for the time when the shelter was removed, and received fertilizer only during the previous summer (1994).Frost resistance was only -5° C during the growing season but more than -100° C during the winter rest period. It was about -10° C at the end of August, increased to -55° C in the next three weeks, and reached -100° C at the beginning of October. The pH of the cell effusate was lowest during the growing season and highest in winter, the difference being about one and half pH unit. Needles exposed to -196° C showed pH from 4.0 in summer to 5.5 in winter, while pH of the non-frozen needles varied from 5.0 to 6.5, respectively. Seasonal variation in frost resistance was explained by a regression model well (R2 = 0.9) when day length, minimum air temperature and pH were entered as variables.

Effects of High Nitrogen Deposition on Forests: Case Studies Close to Fur Animal Farms

Amount and effects of nitrogen depositions near fur animal farms in the major mink and fox growing area of Finland were investigated in Scots pine (Pinus sylvestris) forests along gradients. Distance from the farm and presence of forest canopy had a strong effect on ammonium depositions measured as bulk deposition from May to October. The highest deposition values were recorded in the stand near a large mink farm, where 50 m from the farm the ammonium deposition was 33 kg N ha−1 yr−1 under the canopy and 7 kg N ha−1 yr−1 in the open field. The macroscopic symptoms of forest damages resembled growth disturbances of nutritional origin. The observed tree damage and growth disturbances were in correlation with the high foliar total N and ammonium N contents and high contents of soluble nitrogen in the humus. High amounts of ammonia led to a decrease in the K, Ca and particularly Mg and B contents in the needles and to an increase in total nitrogen, amides and amino acids. Excessive nitrogen was stored mainly in the form of arginine.

Age-dependent modifications of mitochondrial proteins in cerebral cortex and striatum of rat brain

The protein composition of free mitochondria purified from cerebral cortex and striatum during aging was analyzed by gel electrophoresis. Mitochondria were isolated from cerebral cortex and striatum of 4-, 12-, and 24-month-old rat brain. The percent amount of mitochondrial proteins after gel-electrophoretic separation was determined densitometrically. A significant decrease in the amount of two polypeptides (with molecular weights of 20 and 16 kDa, respectively) in both brain regions during aging was found. The decrease was higher in the striatum indicating a greater vulnerability of this brain area to the aging process. The age-dependent modifications of mitochondrial proteins observed may play an important role in several mitochondrial functions, such as energy transduction and transport processes as well as in structural changes occurring with age, causing altered membrane permeability and fluidity.

Non-Coded Biosynthesis of N-acetylaspartyl Peptides in Mouse Brain Homogenates

Abstract N-acetylaspartate and labelled glutamate, aspartate, γ-aminobutyrate and taurine were incorporated into a number of low-molecular weight peptides in mouse brain homogenates, as detected by autoradiography on thin-layer chromatography plates. Peptide biosynthesis was dependent on N-acetylaspartate, cAMP, ATP and an ATP regenerating system. The number of peptides varied from 5 to 12 after incubation for 40 min. The original labelled amino acids were determined by re-chromatography of the acid hydrolysates of the peptides, and the probable structures (N-acetylaspartyl-glutamyl-taurine, [N-acetyl] aspartyltaurine and N-acetylaspartyl [aspartyl, glutamyl]-taurine) were assumed to be present.