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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Polar research 19 (2000), S. 0 
    ISSN: 1751-8369
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geography , Geosciences
    Notes: The industrialized world is expanding its search for energy, minerals, timber and other resources into the Arctic and adjacent higher latitudes. Up to now, large-scale development projects in the Arctic and sub-Arctic have been few. We can, however, profit from experiences gained from several of these, including oil and gas exploration and development in Alaska and on Russia's Yamal Peninsula, the Norilsk metalurgical complex of Siberia, Alaska's Red Dog mine and others. Conclusions drawn from these experiences are that industrial impacts on Arctic grazing systems can be minimized if the following considerations guide their planning: 1) most of the large development projects that have been undertaken in the North have lacked adequate background information on the grazing systems that they might impact; 2) there needs to be recognition by industry and governments for the amount of time required to gather such information and provision made for this; 3) because types of impacts on northern grazing systems that may result from development projects vary depending on whether they involve mining, oil or gas, hydroelectric or other activities, each proposed project must be assessed independently; 4) cumulative effects of multiple projects, often sequentially developed, are seldom addressed by the responsible governments, thus planning for development of an individual project should be within the context of regional and long-range development planning; and 5) types and sources of contaminants entering northern ecosystems, threatening the health of northern residents, must also be a major focus of project assessment.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Polar research 19 (2000), S. 0 
    ISSN: 1751-8369
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geography , Geosciences
    Notes: Reindeer/caribou (Rangifer tarandus) constitute a biological resource of vital importance to the physical and cultural survival of Arctic residents since time immemorial. Recent and possible future economic, social and ecological changes raise concern for sustainability of these resources and the well-being of those who depend on them. In February 1999 eighty scientists, reindeer/caribou users and resource managers gathered in Rovaniemi, Finland, for an interdisciplinary workshop to develop a circumpolar research plan that addressed the sustainability of humanreindeer/caribou systems. Small working groups addressed six themes: hunting systems, herding systems, rengeland/habitat protection, minimizing industrial impacts, maintaining the strength of indigenous cultures, and responding to global change. The resulting Research Plan cells for interdisciplinary comparative studies, advancement of tools for assessing cumulative effects, implementation of regional and a circumpolar monitoring and assessment programmes, and cultural studies on the transmission of knowledge. Cross-cutting directives for future research include:• improving humans’ability to anticipate and respond to change;• understanding better the dynamics of human-reindeer/caribou systems;• developing research methods that are both more instructive and less intrusive;• facilitating open communication among groups with interests in reindeer/caribou resources;• organizing researchers into a strong, coordinated network;• re-framing the conventional research paradigm to be more inclusive of differing cultural perspectives.Three follow-up initiatives are proposed: 1) development of a web-based resource on the human role in reindeer/caribou systems (www.rangifer.net); establishment of a Profile of Herds database to support comparative research; and 3) convening of working groups to address specific problems identified by workshop participants.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 59 (1992), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Denervation and other forms of stimulus deprivation cause an increase in the magnitude of subsequent responses, a phenomenon commonly referred to as denervation supersensitivity. This has been well demonstrated with the cyclic AMP response to norepinephrine in the pineal gland. In the present report, we address the question of whether stimulus deprivation alters α and β subunits of the GTP binding regulatory protein that stimulates adenylyl cyclase activity (Gs). Stimulus deprivation of the pineal gland was produced by denervation (superior cervical ganglionectomy), decentralization of the superior cervical ganglia, or by exposure of the animal to continuous lighting. All increased both the α and β subunits of Gs (Gsα and Gβ) by up to fourfold, as estimated using semiquantitative western blot technology. These effects were detectable after 1 day of stimulus deprivation and were sustained for 2 weeks. The stimulatory effects of constant light-induced stimulus deprivation were also apparent by measuring cholera toxin-dependent ADP-ribosylation of Gsα, which revealed a fourfold increase in the amount of labeled substrate. The results of in vivo studies were confirmed with in vitro studies, which demonstrated a spontaneous increase in both Gsα and Gβ during 72 h of organ culture. The constant light-induced increases in both Gsα and Gβ were prevented by continuous administration of isoproterenol (0.3 mg/kg/day), supporting the suggestion that adrenergic stimulation controls the levels of Gsα and Gβ. These studies indicate that stimulus deprivation increases both Gsα and Gβ. It appears that such increases play a central role in generating supersensitivity in the pineal gland and may play a role in supersensitivity in other systems.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 44 (1985), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: l.-5-Hydroxytryptophan (l-5-HTP) (20 or 200 mg/kg i.p.) but not l-tryptophan (500 mg/kg i.p.) loading substantially increases serum melatonin in sheep. In the present study we examined the effects of these compounds on pineal serotonin and six serotonin metabolites. l-Tryptophan failed to increase 5-hydroxytryptamine (5-HT; serotonin) or any of its metabolites despite a fivefold increase in pineal tryptophan. In contrast, l-5-HTP loading produced a marked increase in pineal 5-HT and its metabolites, including N-acetylserotonin (NAS) and melatonin, indicating that an increased synthesis of melatonin is responsible for the increased serum melatonin concentration after loading with this precursor. No change in pineal indoleamine N-acetyltransferase (NAT) activity was seen. These results are consistent with the suggestion that, during daytime in the sheep, 5-HT availability may limit the production of melatonin.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 44 (1985), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Some aspects of the physiological regulation of the pineal α1-adrenoceptor have been studied using the selective, high-affinity ligand [125I] iodo-2-[β-(4-hydroxyphenyl)ethylaminomethyl]tetralone ([125I]HEAT). Pineal glands taken from rats housed in a diurnal lighting cycle showed no circadian rhythm in the number of specific [125I]HEAT binding sites, although a characteristic rhythm in pineal melatonin was seen. It was established that the pineal α1-adrenoceptor is under neural control because interruption of neural stimulation of the pineal by bilateral superior cervical ganglionectomy (SCGX) or by exposing rats to constant light for 3 weeks doubled receptor density but did not change affinity for [125I]HEAT. Administration of various α1-adrenoceptor agonists either acutely (i.p. injection) or chronically (s.c. infusion) did not alter the number of specific [125I]HEAT binding sites. Together these results indicate that the pineal α1-adrenoceptor, like the pineal β-adrenoceptor, is regulated by sympathetic nerve activity, probably through the physiological release of the neurotransmitter norepinephrine. However the absence of a circadian rhythm in α1-adrenoceptor number and lack of down-regulation by adrenergic agonists imply different mechanisms of regulation.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 50 (1988), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Activation of α1-adrenoceptors appears to amplify β-adrenergic stimulation of cyclic AMP (CAMP) accumulation in rat pinealocytes severalfold by a mechanism involving activation of a Ca2+-, phospholipid-dependent protein kinase (protein kinase C). The mechanism of action of protein kinase C was investigated in this report using intact cells. Activation of protein kinase C with 4β-phorbol 12-myristate 13-acetate (PMA; 10−7M) or the α1-adrenergic agonist phenylephrine (PE; 10−6M) did not inhibit cAMP efflux in β-adrenergically stimulated cells. The amplification of the β-adrenergic cAMP response by these agents also occurred in the presence of isobutylmethylxanthine (10−3M) and Ro 20–1724 (104-M), an observation suggesting that inhibition of cAMP phosphodiesterase activity is not the mechanism of action. Furthermore, although PMA (107- M) caused a sixfold increase in the magnitude of the cAMP response to isoproterenol, it did not alter the EC50 of the response (1.7 × 10−8M), a result indicating that protein kinase C activation does not alter β-adrenoceptor sensitivity. The cAMP response following cholera toxin pretreatment (60–120 min) was rapidly and markedly enhanced by a,-adrenergic agonists (cirazoline 〉 PE 〉 methoxamine), by phorbol esters (PMA 〉 4β-phorbol 12,13,-dibutyrate 〉〉 4α-phorbol 12,13-didecanoate), and by synthetic diacylglycerols (1,2-dioctanoylglycerol 〉 1-oleoyl 2-acetylglycerol 〉〉 diolein). The cAMP response to forskolin (10−5M) was also increased by PE (3 × 10−6M) and PMA (10−7M). Together, these observations indicate that protein kinase C activation amplifies β-adrenergic stimulation of pinealocyte cAMP production at a site beyond the receptor, perhaps on a regulatory guanine nucleotide binding protein or adenylyl cyclase itself.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 48 (1987), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Phosphatidylinositol phosphodiesterase (PL-C) appears to be a key element in the adrenergic regulation of pineal cyclic AMP levels. In the present study, the rat pineal enzyme was characterized using exogenous [3H]phosphati-dylinositol (0.5 mM) as substrate. Half the enzyme activity was found in the cytosolic fraction, but the highest specific concentration was associated with the membrane fraction. Two pH optima (5.5 and 7.5) of enzyme activity were observed for the membrane fraction but only one in the cyto-sol fraction (pH 5.5). Enzyme activity in both fractions was Ca2+ dependent. In the case of the membrane protein in pH 7.5, the enzyme activity was sensitive to changes in Ca2+ in the 10–100 nAf range. Addition of an equimolar concentration of phosphatidylinositol 4-phosphate nearly completely inhibited the hydrolysis of [3H]phosphatidylinositol; other phospholipids (1.0 mM) were less potent. This may reflect our present finding that [3H]phosphatidylinositol 4-phosphate is a better substrate than [3H]phosphatidylinositol for the enzyme. Stimulus deprivation (2 weeks of constant light or superior cervical ganglionectomy) reduced the cytosolic activity by 30% and had no effect on the membrane-associated enzyme.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 48 (1987), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: A two-step chromatographic procedure has been developed for the purification of ovine pineal arylalkylamine N-acetyltransferase (EC 2.3.1.87), based on the principles of disulfide exchange and anion exchange. The enzyme from 20 ovine pineal glands can be purified about 500-fold in a day; recovery is about 5%. Polyacrylamide gel electrophoretic analysis of the final preparation shows four major bands; one appears to be arylalkylamine N-acetyl-transferase.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 46 (1986), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Rhodopsin kinase, once thought to be a retinal enzyme, was recently found at high levels in the pineal gland. In the present study the developmental pattern and the regulation by environmental lighting of this enzyme in both tissues was studied in the rat. Enzyme activity was present in the neonatal pineal gland several days earlier than in the retina, and increased gradually up to 20 days of age and remained at that level thereafter; the retinal enzyme appeared to increase until day 60. Pineal and retinal rhodopsin kinase activities showed a 25% increase in in the middle of the dark and the beginning of the light period, respectively. Exposure to constant light caused a 50% decrease in rhodopsin kinase levels in both tissues. However, only pineal rhodopsin kinase activity declined followed bilateral superior cervical ganglionectomy. This indicates pineal rhodopsin kinase activity is similar to other pineal enzymes in that it is controlled by light acting through the sympathetic nervous system. In contrast, the light-induced decrease in retinal rhodopsin kinase may be due to the direct destructive effect of light on the retina. The finding of neural control of pineal rhodopsin kinase in the pineal gland of adult rats is consistent with a function of the enzyme in the neural regulation of pineal function.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 40 (1983), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The relative importance of neural, and some nonneural, mechanisms in the control of pineal hydroxyindole-O-methyltransferase (HIOMT) activity during development and in the adult rat was studied. In neonatal rats, guanethidine-treatment, bilateral superior cervical ganglionectomy (SCGX), or exposure to constant light did not prevent the initial appearance of HIOMT activity, indicating that neural stimulation of the gland is not essential for the development of HIOMT activity. In adult rats, decentralization or removal of the SCG led to a slow fall in HIOMT activity, to about 30% of control activity, indicating that the enzyme is largely under neural control. Additionally, adrenalectomy or hypophysectomy had no effect on HIOMT activity, refuting the suggestion that adrenal and/or gonadal steroids are of major importance in the regulation of this enzyme. The fall in activity of the enzyme after SCGX or exposure to constant light probably does not represent a shift in the Km of the enzyme nor the selective disappearance of a distinct molecular species. Similar changes in HIOMT activity and cyclic GMP responsiveness occur in response to alterations in the length of the daily dark period, adding further evidence to our earlier speculation that there may be a functional relationship between these two.
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