Experimentally increased soil temperature causes release of nitrogen at a boreal forest catchment in southern Norway

Boreal forest ecosystems are sensitive to global warming, caused by increasing emissions of CO₂ and other greenhouse gases. Assessment of the biological response to future climate change is based mainly on large-scale models. Whole-ecosystem experiments provide one of the few available tools by which ecosystem response can be measured and with which global models can be evaluated. Boreal ecosystem response to global change may be manifest by alterations in nitrogen (N) dynamics, as N is often the growth limiting nutrient. The CLIMEX (Climate Change Experiment) project entails catchment-scale manipulations of CO₂ (to 560 ppmv) and temperature (by + 3 to + 5 °C) to whole forest ecosystems in southern Norway. Soil temperature is increased at 400-m² EGIL catchment by means of electric cables placed on the soil surface. Soil warming at EGIL catchment caused an increase in nitrate and ammonium concentrations in runoff in the first year of treatment. We hypothesize that higher temperature increased N release by mineralization. Whether these responses are only transient will be shown by additional years' treatment.     

The immature stages of some Phlebotomine sandflies from Brazil (Diptera: Psychodidae)

Immature stages of Lutzomyia anduzei (Rozeboom), L.antunesi (Coutinho), L. flaviscutellata (Mangabeira), Psychodopygus davisi (Root), Ps.paraensis (Costa Lima) and Ps.lainsoni Fraiha & Ward are described from specimens reared in the laboratory. The Lutzomyia species are members of the intermedia group, though L. flaviscutellata larvae more closely resemble those of Psychodopygus species. The larvae of L.anduzei and L. antunesi are separable on minor setal differences and are similar to previously described members of the intermedia group. Ps. paraensis is distinguishable from the other two Psychodopygus species described, by the absence of prothoracic seta 2. Head seta 5 of Ps.davisi is about twice the length of that in Ps. paraensis and larvae of Ps.lainsoni are pale and characterized by colourless body setae 4 and 10. A key to the fourth instar larvae is given which includes all the known larvae of the intermedia group and of the genus Psychodopygus. Morphological differences in the Psychodopygus larvae do not appear to reflect the separation of the adults into series.     

Elevation of Serum Dopamine-β-hydroxylase Activity with Forced Immobilization

THE formation of the neurotransmitter noradrenaline from 3,4-dihydroxyphenylethylamine (dopamine) is catalysed by the enzyme dopamine-β-hydroxylase (DBH)¹. This enzyme is associated both with the catecholamine-containing chromaffin granules in the adrenal medulla^2,3 and with the vesicular structures in sympathetic nerve terminals which contain catecholamines⁴. Furthermore, DBH activity is released with catecholamines into the perfusate after stimulation of either the isolated perfused adrenal gland⁵ or the isolated perfused spleen^6–8. DBH activity has been reported in the serum of both man and the rat^9,10. This activity is similar to adrenal and sympathetic nerve DBH activity with regard to cofactor requirements, oxygen requirement and kinetic characteristics^9,10. It has been suggested that serum DBH activity might be present as a result of release of enzyme with catecholamines from the adrenal glands and sympathetic nerves. If this is the case, serum DBH activity might be a useful and convenient index of sympathetic-adrenal activity. The work described here was undertaken to investigate both the source of the serum DBH and the effect on this activity of forced immobilization, a procedure which has been used as a model of stress and which has been shown to release catecholamines from the adrenal gland and increase catecholamine excretion¹¹.     

A revised ammonite zonation of the Boreal Oxfordian and its application in northeast Greenland

A revised ammonite zonation for use in the Middle–Upper Oxfordian of the Boreal province is put forward. The zonation is used to date late Jurassic sediments in the Wollaston Forland area of northeast Greenland. The sediments broadly comprise basinal mudstones and shallow marine and shoreline sandstones, which were deposited in westerly tilted fault blocks during three transgressive pulses. On the peneplaned surfaces of wide tilted fault blocks a thick sequence of tidally and fluvially influenced marine sandstones of Middle Jurassic age was deposited. In the Upper Jurassic deposition initially took place in the centre of the basin where 80 m of shoreface sandstones accumulated (Jakobsstigen Member). In the second pulse the upthrown margin of the next fault block to the west was transgressed and deposition of basinal mudstones (Bernbjerg Formation) commenced in the basin centre on the main part of the dip-slope of the eastern block. Finally the crestal areas of the block on Kuhn Ø were inundated in Kimmeridgian times, and then subsided rapidly.     

Accelerated Nitrate Uptake in Wheat Seedlings: Effects of Ammonium and Nitrite Pretreatments and of 6-Methylpurine and Puromycin

The experiments reported herein had two objectives. One was to determine if the slow rate of nitrate uptake which occurs upon initial exposure of nitrogen-depleted wheat (Triticum vulgare cv. Knox) plants to nitrate was the result of insufficient reduced nitrogen. The second was to determine the impact of restrictions in ribonucleic acid or protein synthesis on both nitrate uptake and nitrate reduction. Pretreatments of 14-day-old seedlings for a few hours in ammonium or nitrite did not result in an enhancement of the initial slow rate of nitrate uptake. Growth for two additional weeks in ammonium also failed to eliminate the induction period. The evidence indicates that the presence of nitrate, rather than a product of its reduction, was required to initiate development of the accelerated rate of nitrate uptake. Puromycin (400 μg ml^?1) and 6-methylpurine (0.5 mM) prevented development of the accelerated phase of nitrate uptake. With both compounds, the relative restriction of nitrate uptake was greater than that of nitrate reduction as revealed by incorporation of ¹⁵N from labeled nitrate into reduced forms. The proportion of reduction which occurred in the root system under the imposed treatments could not be delineated precisely, preventing an unequivocal determination of the extent to which the two processes are coupled in the root system. The data nevertheless indicate nitrate reduction was closely associated with nitrate uptake. Accumulation of nitrate in the shoots was markedly restricted in presence of 6 methylpurine. This effect most likely was a result of a severe restriction in the translocation of nitrate into the xylem, rather than an increase in the reduction rate in the shoots.     

Trans‐equatorial migration,staging sites and wintering area of Sabine’s Gulls Larus sabini in the Atlantic Ocean

The migrations and winter distributions of most seabirds, particularly small pelagic species, remain poorly understood despite their potential as indicators of marine ecosystem health. Here we report the use of miniature archival light loggers (geolocators) to track the annual migration of Sabine’s Gull Larus sabini, a small (c. 200 g) Arctic‐breeding larid. We describe their migratory routes and identify previously unknown staging sites in the Atlantic Ocean, as well as their main Atlantic wintering area in the southern hemisphere. Sabine’s Gulls breeding in northeast Greenland displayed an average annual migration of almost 32 000 km (n = 6), with the longest return journey spanning close to 39 000 km (not including local movements at staging sites or within the wintering area). On their southern migration, they spent an average of 45 days in the Bay of Biscay and Iberian Sea, off the coasts of France, Spain and Portugal. They all wintered in close association with the cold waters of the Benguela Upwelling, spending an average of 152 days in that area. On their return north, Sabine’s Gulls staged off the west African coast (Morocco, Mauritania, Senegal), spending on average 19 days at this site. This leg of migration was particularly rapid, birds travelling an average of 813 km/day, assisted by the prevailing winds. Sabine’s Gulls generally followed a similar path on their outbound and return migrations, and did not exhibit the broad figure‐of‐eight pattern (anti clockwise in the southern hemisphere and clockwise in the northern hemisphere) seen in other trans‐equatorial seabirds in the Atlantic and Pacific oceans.     

The Active and the Inactive Form of the hAT1 Receptor Have an Identical Ligand-Binding Environment: An MPA Study on a Constitutively Active Angiotensin II Receptor Mutant

Several models of activation mechanisms were proposed for G protein-coupled receptors (GPCRs), yet no direct methods exist for their elucidation. The availability of constitutively active mutants has given an opportunity to study active receptor conformations within acceptable limits using models such as the angiotensin II type 1 (AT₁)¹ receptor mutant N111G-hAT₁ which displays an important constitutive activity. Recently, by using methionine proximity assay, we showed for the hAT₁ receptor that TMD III, VI, and VII form the ligand-binding pocket of the C-terminal amino acid of an antagonistic AngII analogue. In the present contribution, we investigated whether the same residues would also constitute the ligand-binding contacts in constitutively activated mutant (CAM) receptors. For this purpose, the same Met mutagenesis strategy was carried out on the N111G double mutants. Analysis of 43 receptors mutants in the N111G-hAT₁ series, photolabeled and CNBr digested, showed that there were only subtle structural changes between the wt-receptor and its constitutively active form.