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Notes: Abstract Arachidonic acid is metabolized via two pathways in leukocytes: cyclo-oxygenase, leading to the stable prostaglandins, and lipoxygenase, leading to hydroxyacids. Indomethacin inhibits the cyclo-oxygenase selectively, whereas compound BW755C (3-amino-1-(m-(trifluoromethyl)phenyl)-2-pyrazoline) inhibits both pathways equally. This offers a possible explanation for the differing activities of these two compounds in inflammatory models in vivo. The patterns of product inhibition by the two compounds support the suggestion that 11-HETE (hydroxy-eicosatetraenoic acid) and 15-HETE can arise by incomplete operation of the cyclo-oxygenase pathway.

Notes: Production of electronic ground state NO2 (2A1) from 248 nm photolysis of HNO3 was detected by laser induced fluorescence (LIF). A growth in the LIF signal was observed following the photolysis and has been interpreted as the relaxation of NO2 through the higher vibrational levels of the X(2A1) state; an energy region where the probe laser photodissociates the NO2 instead of inducing fluorescence. The rate coefficients for NO2 relaxation through these high vibrational levels were determined by fits of time resolved LIF signal to a stepladder kinetic model. The results of the kinetic analysis suggest that the observed relaxation begins at the 2B2 threshold near 9500 cm−1 and extends downward through approximately 5 vibrational levels of the ground electronic surface. The derived quenching rate coefficients (in units of 10−12 cm3 molecule−1 s−1) are 0.51±0.05, 1.0±0.1, 1.4±0.2, 2.6±0.6, and 8.7±1.1 for Ar, He, N2, O2, and CO2 collision partners, respectively. The discrepancies between these coefficients and previous literature values are rationalized in terms of a dependence of the vibrational relaxation rate on total internal energy.

Notes: It is a commonly accepted notion that cells which make projections between the multiple cortical areas found in the mammalian visual system are excitatory, but there is little direct evidence that this is the case. Here we demonstrate using retrograde tracing with D-[3H]aspartate that connections in the rat which project from lower to higher visual areas (i.e. forward) and those which project from higher to lower areas (i.e. feedback) may use excitatory amino acid neurotransmitters. Following injection into the primary visual cortex, clusters of retrogradely labelled cells were found in several extrastriate areas within the cytoarchitectonic subdivisions 18a (‘areas’ LM, AL, PX, FLX, RL, AX) and 18b (‘area’ MX), and in the retrosplenial cortex. In all of these areas D-[3H]aspartate-labelled cells were surrounded by diffuse label which may represent anterograde labelling of axon terminals. This suggests that both legs of reciprocal intracortical circuits have similar chemospecificity. To directly demonstrate excitatory amino acid localization in forward projections, D-[3H]aspartate was injected into extrastriate area LM. As expected, the results revealed retrogradely labelled neurons within area 17. Outside area 17, LM injections labelled neurons in AL, PX, FLX, RL, AX and MX. Taken in the context of the hierarchy of areas in rat cerebral cortex (Coogan and Burkhalter, J. Neurosci., 13, 3749–3772, 1993), these results show that D-[3H]aspartate labels: (1) forward connections from area 17 to LM, AL, PX, RL, AX and MX, (2) feedback connections from LM, AL, FLX, PX, RL, AX and MX to area 17, (3) feedback connections from AL, PX, RL, AX and MX to LM, and (4) lateral connections between FLX and LM. These findings strongly indicate that both forward and feedback connections as well as lateral connections at several different levels of the cortical hierarchy use excitatory amino acid neurotransmitters.

Notes: Calciam/calmodulin-dependent processes are altered by manipulations of the hypothalamic-pituitary-adrenal axis, and are associated with changes in synaptic efficacy in the hippocampus, such as long-term potentiation. Recent evidence indicates that there are diurnal variations in the threshold for long-term potentiation, as well as diverse effects of the adrenals and of adrenal steroids on electrical activity related to long-term potentiation. In order to probe possible mechanisms underlying these observations, we investigated the effects of the diurnal cycle, as well as adrenalectomy (ADX) and adrenal demedullation on adenylate cyclase activity. In hippocampal, but not cortical, membranes the adenylate cyclase response to calmodulin was higher during the beginning of the dark phase of the cycle, when endogenous corticosterone levels are high. Basal and forskolin-stimulated adenylate cyclase activity did not exhibit diurnal variation in either brain region. ADX (6 and 14 days) depressed the adenylate cyclase response to calmodulin in hippocampal membranes, and abolished the diurnal difference. ADX had smaller effects on this response in cortical membranes. ADX also attenuated basal and forskolin-stimulated adenylate cyclase activity, but these changes were less striking than effects on calmodulin-stimulated activity. Demedullation (14 days), generating corticosterone levels in the low physiological range, mirrored the effects of ADX on hippocampal adenylate cyclase activity. Corticosterone (20 to 25 μg/ml in the drinking water) did not consistently prevent ADX effects on adenylate cyclase activity. These results demonstrate that adrenal effects on adenylate case activity are regionally specific within the brain, and they suggest that other adrenal secretions besides glucocorticoids may be involved in the feedback of the diurnal rhythm on the hippocampus. Taken together with our recent finding that chronic stress or corticosterone injection selectively attenuated the adenylate cyclase response to calmodulin in cortical, but not hippocampal membranes our findings provide further support for a role of the pituitary-adrenal axis in modulating neural calmodulin-dependent adenylate cyclase activity.

Notes: The dehydrogenase form of 11 β-hydroxysteroid dehydrogenase (11-DH) which catalyzes the oxidation of the biologically active steroid, corticosterone, to its inactive metabolite, 11-dehydrocorticosterone, is found in rat brain. The distribution and localization of 11-DH-like labeling in the rat brain was examined by immunocytochemistry. 11-DH-like immunostaining was found in all subfields of the hippocampus and in many other parts of the brain, including the preoptic area (POA), central nucleus of the amygdala, bed nucleus of the stria terminalis (NIST) and the cerebral cortex. Percentages of 11-DH-positive cells ranged from 10% in the POA and NIST to 50% to 60% in the hippocampus. When combined with neuronal or glial markers, 11-DH-like immunostaining was found to be predominantly localized within neurons, ranging from 10% or less glial labeling in hippocampus, amgydala and cortex to 22% glial labeling in the POA and NIST. Immunostaining was present in both the cytoplasmic and nuclear components of some cells in addition to their projections. In the kidney, 11-DH has been postulated to be a key component in a mechanism by which aldosterone gains access to renal Type I receptors despite the presence of much higher concentrations of glucocorticoids. The present data is consistent with a similar mechanism occurring in at least some parts of the brain, although the hippocampus appears to be an important exception because it does not appear to be differentially responsive to aldosterone in spite of its high 11-DH activity and immunoreactivity. However, the hippocampus is not implicated in neural control of salt appetite and fluid balance, whereas some of the other brain regions like the POA, NIST and amygdala are believed to be involved. Other aspects of 11-DH localization must therefore be examined in future studies, including the co-presence of mineraiocorticoid receptors and 11-DH in the same or adjacent cells and the possible significance of the relatively high glial localization of 11-DH immunoreactivity in the POA and NIST.

Notes: As part of a study of nuclear power development in Japan and the United States, surveys of perceptions of risk toward 30 activities, substances, and technologies have been carried out in the Pacific Northwest and Tokyo, Japan. The results show that people in both countries have the highest level of dread toward nuclear waste disposal, nuclear accidents, and nuclear war, greater even than their dread of crime and AIDS. In addition to comparisons of dread, the paper also discusses similarities and differences between Japanese and American responses for other dimensions of risk perception.

Notes: Herbicides were applied annually for 3 years to a pasture population of Emex australis Steinh. Herbicide performance was highly variable, with significant effects on weed survival only in single seasons. In most cases, seed bank densities declined monotonically from an initial level of 1900 m−2. Seed banks decreased after seasons when E. australis contributed less than 25% to pasture dry matter. The annual decay rate of the seed bank was estimated to be 70%. Owing to the unreliability of the herbicides when applied at rates low enough to protect pasture legumes, the potential for tactical chemical control of E. australis is limited. Furthermore, it is argued that the potential for strategic chemical control is low, since the species can tolerate periods of population decline. E. australis could be managed more effectively by maintaining high densities of annual grasses and legumes, against which it is a poor competitor. Efficacité herbicide et lutte contre Emex australis dans une pâture annuelleDes herbicides ont été appliqués chaque année pendant trois ans sur une population d' Emex australis Steinh. dans une pâture. L'efficacité herbi- cide était très variable, et les effets significatifs sur la survie des mauvaises herbes ne furent que des évènements uniques, observés lors de saisons isolées. Dans la plupart des cas, les stocks semenciers ont décru de façon monotone à partir d'un niveau initial 1900 m−2. Us décrurent après les saisons oùE. australis contribuait pour moins de 25%à la matière sèche de la pâture. Le taux de décroissance annuel du stock semencier était estiméâ 70%. En raison du manque de fiabilité des herbicides lorsqu'ils sont appliqués â des doses suffisamment basses pour respecter les légumineuses de la pâture, leur intérêt pour la lutte chimique à court terme contre E. australis est limité. Leur intérêt à moyen terme est égale-ment faible car cette espece peut supporter des périodes de déclin démographique. On pourrait lutter plus efficacement contre E. australis en maintenant de fortes densités de graminées annuelles et de légumineuses, à l'égard desquelles cette mauvaise herbe est un com-pétiteur médiocre. Herbizidwirkung und die Bekämpfung von Emex australis auf einjährigem WeidelandBei jährlicher Anwendung von Herbiziden über 3 Jahre hin zur Bekämpfung von Emex australis Steinh. war die Wirkung sehr variabel; eine sig-nifikante Wirkung auf das Überleben des Unkrauts gab es nur in einzelnen Vegetations-perioden. Die Bodensamenbank nahm meistens gleichförmig von einem Ausgangsbestand von 1900 m−2 ab. Die Samendichte sank in den Jahren, wo Emex australis weniger als 25% der Trockenmasse der Weidepflanzen ausmachte. Der jährliche Rückgang der Lebensfähigkeit der Samen im Boden wurde auf 70% geschätzt. Wegen der Unzuverlässigkeit von Herbiziden, wenn sie zum Schutz der Weide-pflanzen niedrig dosiert werden, sind die Aussichten für eine chemische Bekämpfung dieser Art begrenzt. Außerdem sind langfristige Erfolge auf diese Weise kaum zu erreichen, da die Art zeitweiligen Populationsrückgang übersteht. Die Verbreitung von Emex australis sollte durch hohe Dichten einjähriger Gräser und Leguminosen wirkungsvoller zurückgedrängt werden können, weil sie gegenüber diesen Arten ein schlechter Konkurrent ist.