In Vivo Studies on the Extracellular, and Veratrine-Releasable, Pools of Endogenous Amino Acids in the Rat Striatum: Effects of Corticostriatal Deafferentation and Kainic Acid Lesion

The effects of corticostriatal deafferentation (decortication) and destruction of intrinsic neurons (intrastriatal kainate injection) on the extracellular concentration, and veratrine-releasable pools, of endogenous amino acids in the rat striatum were examined using the in vivo brain dialysis technique. Intracellular amino acid content was also determined. Decortication reduced selectively intra- and extracellular levels of glutamate (Glu) and aspartate (Asp). Extracellular changes were more pronounced than those in tissue content. gamma-Aminobutyric acid (GABA), taurine (Tau), and phosphoethanolamine (PEA) levels were not affected, whereas nonneuroactive amino acids were increased at 1 week but not at 1 month post-lesion. The intracellular pool of Glu and Asp was also reduced in kainate-lesioned striata. However, extracellular levels of these compounds were not affected significantly by this treatment. The tissue content of all other amino acids was decreased, the most prominent change being in the concentration of GABA. Extracellular GABA concentration was also reduced dramatically, whereas the concentrations of noneuroactive amino acids were increased to varying degrees. These data suggest that transmitter pools of neuroactive amino acids are an important supply for their extracellular pools. Lesion-induced alterations in nonneuroactive amino acids are discussed with regard to the loss of metabolic pools, glial reactivity, and changes in blood-brain barrier transport. Veratrine induced a massive release of neuroactive amino acids such as Glu, Asp, GABA, and Tau into the extracellular fluid, and a delayed increase in PEA. Extracellular levels of neuroactive amino acids were raised slightly. Decortication reduced, selectively, the amounts of Glu and Asp released by veratrine.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cellular Origins of Endogenous Amino Acids Released into the Extracellular Fluid of the Rat Striatum During Severe Insulin-Induced Hypoglycemia

The effect of severe insulin-induced hypoglycemia on the extracellular levels of endogenous amino acids in the rat striatum was examined using the brain microdialysis technique. A characteristic pattern of alterations consisting of a 9-12-fold increase in aspartate (Asp), and more moderate increases in glutamate (Glu), taurine (Tau), and gamma-aminobutyric acid (GABA), was noted following cessation of electroencephalographic activity (isoelectricity). Glutamine (Gln) levels were reduced both during and after the isoelectric period and there was a delayed increase in extracellular phosphoethanolamine (PEA) content. The effects of decortication and excitotoxin lesions on the severe hypoglycemia-evoked efflux of endogenous amino acids in the striatum were also examined. Decortication reduced the release of Glu and Asp both 1 week and 1 month post-lesion. The efflux of other neuroactive amino acids was not affected significantly. In contrast, GABA, Tau, and PEA efflux was attenuated in kainate-lesioned striata. Glu and Asp release was also reduced under these conditions, and a smaller decrease in extracellular Gln was noted. These data suggest that GABA, Glu, and Asp are released primarily from their transmitter pools during severe hypoglycemia. The releasable pools of Tau and PEA appear to be located in kainate-sensitive striatal neurons. The significance of these results is discussed with regard to the excitotoxic theory of hypoglycemic cell death.     

Transport of Mg2+ and Ca2+, and Mg2+-stimulated adenosine triphosphatase activity in oat roots as affected by mineral nutrition

Mg²⁺- and Ca²⁺-uptake was measured in dark-grown oat seedlings ( Avena sativa L. cv. Brighton) cultivated at two levels of mineral nutrition. In addition the stimulation of the ATPase activity of the microsomal fraction of the roots by Mg²⁺ was measured. Ca²⁺-uptake by the roots was mainly passive. Mg²⁺-uptake mainly active; the passive component of Mg²⁺-uptake was accompanied by Ca²⁺-efflux up to 60% of the Ca²⁺ present in the roots.
In general Mg²⁺ -uptake of oat roots was biphasic. The affinity of the second phase correspond well with that of the Mg²⁺-stimulation of the ATPase activity, in low-salt roots as well as in high-salt roots and in roots of plants switched to the other nutritional condition. Linear relationships were observed when [phase 2] Mg²⁺-uptake was plotted against Mg²⁺-stimulation of the ATPase activity of the microsomal fraction of the roots. In 5 days old high-salt plants 1 ATP (hydrolysed in the presence of Mg²⁺ J corresponded with active uptake of a single Mg²⁺ ion, but in older high-salt roots and in low-salt roots more ATP was hydrolysed per net uptake of a Mg²⁺ ion. The results are discussed against the background of regulation of the Mg²⁺-level of the cytoplasm of root cells by transport of Mg²⁺ by a Mg²⁺-ATPase to the vacuole, to the xylem vessels, and possibly outwards.     

Secondary chemistry and ribosomal DNA data congruencies in Arnica (Asteraceae)

To investigate possible congruencies between DNA sequence data and secondary chemistry, we compared nuclear ribosomal DNA (nrDNA) sequence data, sesquiterpene lactone (STL) contents, and cytometric data from 35 accessions of 16 Arnica (Asteraceae) species and two outgroup taxa ( Layia hieracioides and Madia sativa ), using phylogenetic inference and principal component analysis (PCA). Several groups supporting multiple accessions of the same species (of A. montana , A. longifolia , A. gracilis , and A. chamissonis ) are congruent between the phylogenetic trees based on nrDNA and STL data. Sesquiterpene lactone profiles were found to be highly consistent within multiple samples of A. montana and A. longifolia respectively . Moreover, sesquiterpene lactone data support subspecies classifications of A. chamissonis and A. parryi , with additional support from DNA sequence data and cytometric data. Morphology, STL data (PCA), cytometric data and DNA sequence data suggest a hybrid origin of one accession ( A. gracilis  ×  longifolia ). In A. gracilis , A. latifolia , and Layia hieracioides , previously not investigated for STLs, we found large amounts of xanthalongin derivatives. This is the first time STLs have been reported from subtribe Madiinae.
© The Willi Hennig Society 2009.     

The brain 5-HT4 receptor binding is down-regulated in the Flinders Sensitive Line depression model and in response to paroxetine administration

The 5-hydroxytryptamine (5-HT₄) receptor may be implicated in depression and is a new potential target for antidepressant treatment. We have investigated the brain 5-HT₄ receptor [³H]SB207145 binding in the Flinders Sensitive Line rat depression model by quantitative receptor autoradiography, and related this to 5-HT transporter ( S )-[ N -methyl-³H]citalopram binding. We also determined the regulation of 5-HT₄ receptor binding by 1, 14, and 21 days of paroxetine administration and subchronic 5-HT depletion, and compared this with changes in 5-HT_2A receptor [³H]MDL100907 binding. In the Flinders Sensitive Line, the 5-HT₄ receptor and 5-HT transporter binding were decreased in the dorsal and ventral hippocampus, and the changes in binding were directly correlated within the dorsal hippocampus. Chronic but not acute paroxetine administration caused a 16–47% down-regulation of 5-HT₄ receptor binding in all regions evaluated including the basal ganglia and hippocampus, while 5-HT depletion increased the 5-HT₄ receptor binding in the dorsal hippocampus, hypothalamus, and lateral globus pallidus. In comparison, the 5-HT_2A receptor binding was decreased in the frontal and cingulate cortices after chronic paroxetine administration, and markedly reduced in several regions after 5-HT depletion. Thus, the 5-HT₄ receptor binding was decreased in the Flinders Sensitive Line depression model and in response to chronic paroxetine administration.     

Gravitropic responses of the Avena coleoptile in space and on clinostats. IV. The clinostat as a substitute for space experiments

Gravitropic responses of dark grown oat coleoptiles were measured in weightlessness and under clinorotation on earth. The tests in microgravity were conducted in Spacelab during the IML-1 mission and those on clinostats were conducted in laboratories on earth. The same apparatus was used for both kinds of tests. In both cases autotropism and gravitropic responsiveness were determined. This allowed a quantitative comparison between the plants' responses after receiving the same tropistic stimulations either in weightlessness or on clinostats.
Autotropism was observed with oat coleoptiles responding in weightlessness but it did not occur on clinostats. Gravitropic responsiveness was measured as the ratio between the incremental bending response (degrees curvature) and the corresponding incremental g-dose (stimulus intensity times duration for which it was applied). Plants were tested at either of two stages of coleoptile development (i.e. different coleoptile lengths). From a total of six different kinds of critical comparisons that could be made from our tests that provided data for clinorotated vs weightless plants, three showed no significant difference between responses in simulated vs authentic weightlessness. Three other comparisons showed highly significant differences. Therefore, the validity of clinorotation as a general substitute for space flight was not supported by these results.     

Identification of 27-oxo-octacosanoic acid and heptacosane-1,27-dioic acid in Legionella pneumophila

A strain of Escherichia coli having elevated levels of cytochrome bo and lacking the cytochrome bd quinol oxidase was grown in chemostat culture at low copper levels. Such cells had lowered levels of copper and of total cytochrome b. Cytochrome o concentration was unchanged when assayed by conventional CO difference spectroscopy, but apparently diminished by 80% in copper-deficient cells as determined by photodissociation of bound CO at 193 K. This is attributed to depletion of copper in the oxidase of copper-deficient cells, causing rapid recombination of photodissociated CO to haem O. CO recombination was also more sensitive to low intensities of actinic light in copper-depleted oxidase. The results illustrate a further similarity between the active sites of o- and aa3-type terminal oxidases.