Radioimmunoassay for determination of indole-3-acetic acid in fungi and plants

A radioimmunoassay technique for indole-3-acetic acid is described. The method has successfully been used to measure extractable indole-3-acetic acid in fungal and plant materials and is able to detect as little as 0.3 pmol. As non-radioactive antigen the methyl ester of indole-3-acetic acid is used and the radioactive antigen is tritiated. An acid-catalyzed esterification of indole-3-acetic acid is used for conversion into methyl ester. The measuring range of the assay is 0.3–10 pmol. In the assay, separation of free and bound fractions is achieved by dextran-coated charcoal, leaving the bound fraction in the supernatant.     

A transient inward current elicited by hyperpolarization during serotonin activation in Xenopus oocytes

Activation of serotonin, glutamate or muscarinic receptors, incorporated into the membrane of Xenopus oocytes following injection of messenger RNA from rat brain, caused the development of a transient inward (Tin) current when the membrane was hyperpolarized. A detailed study was made of the Tin current induced during serotonin activation. The current is due principally to efflux of chloride ions, and is presumably activated by an influx of calcium ions, because it was blocked by removal of calcium from the bathing medium, by addition of manganese, cobalt or lanthanum, or by intracellular injection of EGTA. During application of serotonin, the amplitude of the Tin current increased slowly, and after washing it persisted for longer than the direct serotonin-induced current. The amplitude of the Tin current was sensitive to temperature and pH, and was abolished at pH 6.5 or by cooling to 12 degrees C. The Tin current may be of importance in regulating the excitability of neurons in the central nervous system.     

Electrophysiological and neurochemical investigations of the action of presynaptic neurotoxins

Previous experiments have suggested that hemicholinium-3 might directly antagonize certain actions of beta-bungarotoxin at the neuromuscular junction. Data presented here show that, on the contrary, hemicholinium-3 neither inhibits the phospholipase activity of beta-bungarotoxin nor does it affect the characteristic pattern of transmitter release observed at end plates exposed to the toxin. Lanthanum ions were found to promote the release of acetylcholine from sartorius nerve-muscle preparations that had been paralyzed by botulinum toxin. However, the acceleration of transmitter release by lanthanum was not nearly as great as in control preparations as monitored either electrophysiologically or by chemical measurement of ACh.     

Animal community structure as a function of stream size

The species-area relationship of the island biogeography theory was calculated for macroinvertebrates in 22 coastal, adjacent streams. A z-value of 0.19 was obtained. The low z-value was probably a consequence of the short distances between streams as well as high dispersal rates. In addition, a cluster analysis based on the dissimilarity of species assemblages showed that stream size was of prime importance in categorizing the streams. To a smaller extent water quality affected the community structure in the streams.     

Regional Distribution of Homocysteine in the Mammalian Brain

The regional distribution of L-homocysteine (Hcy) was determined in brains from mouse, rat, guinea pig, and rabbit, using a sensitive radioenzymatic assay. Large interspecies variations in the Hcy content in various parts of the brain were observed, but cerebellum contained the highest amount in all species investigated. In the rat the amount of Hcy in cerebellum (6.4 nmol/g) was about sixfold higher than in most other parts of the brain, whereas in the mouse and guinea pig the amount in cerebellum (about 1 nmol/g) was only twofold higher than in the other brain regions. There was a remarkably high level of Hcy in all regions of the rabbit brain (4-10 nmol/g); the highest concentration was found in the cerebellar white matter. In this species the amount of Hcy in all brain regions examined exceeded that in the liver.     

Metabolism and transport of amino acids studied by immunocytochemistry

The immunocytochemical method for demonstrating amino acids makes it possible to study accumulation and depletion of amino acids in individual tissue compartments resulting from experimental manipulations. We have incubated hippocampal slices in oxygenated Krebs solution, containing various additives, under basal conditions and during synaptic release of transmitters evoked by elevated K+ concentrations or by veratrine. Immunoreactivities for glutamate (Glu-LI), aspartate (Asp-LI), glutamine (Gln-LI), gamma-amino-butyrate (GABA-LI) and taurine (Tau-LI) have been demonstrated by specific antibodies after fixation of the slices in glutaraldehyde. Prolonged depolarisation depleted Glu-LI, Asp-LI and Gln-LI from nerve-ending-like structures. GABA-LI was less affected and Tau-LI not affected at all. The depletion of immunoreactivities could be prevented by metabolic precursors of transmitter amino acids, notably glutamine. This effect of glutamine was abolished by inhibiting glutaminase with diazooxonorleucine. Glu-LI, Asp-LI, GABA-LI and Gln-LI accumulated in astroglial cells during conditions of prolonged depolarization-induced release. The accumulation of GABA-LI in glia was strongly increased by inhibition of aminotransferases by aminooxyacetic acid. The described changes in Glu-LI were prevented by low Ca2+/high Mg2+, and promoted when the glial enzyme glutamine synthetase was inhibited by methionine sulfoximine. D-Aspartate, a metabolically inert competitive inhibitor/substrate for high affinity uptake of glutamate, inhibited the accumulation of Glu-LI in glia. The results confirm the biochemically derived theories on metabolic compartmentation in nervous tissue, and add knowledge on the dynamics of the cellular distribution of amino acids. They also indicate the possibilities offered by the present approach for studying metabolism and pharmacology at the cellular level.     

Ecological effects of lime treatment of acidified lakes and rivers in Sweden

Effects on the aquatic biota of lime (CaCO₃) application in acidified lakes and streams were studied in a number of waters. After treatment, lime-sensitive species of mosses (Sphagnum spp.) decreased, but species such as Potamogeton natans and Myriophyllum alterniflorum seemed to be favoured. A few years after liming species composition and diversity of phytoplankton, zooplankton and benthic insect larvae were almost identical to that found in oligotrophic and non-acid lakes. Molluscs and benthic crustaceans may have difficulties recolonizing. Reproduction of remaining species of fish was successful as soon as pH increased. High survival of larvae and fry can result in some extremely rich year classes with slow individual growth. In most cases restocking of depleted fish stocks was successful.     

Differential Inhibition of Cell Division in Euglena gracilis by Cysteamine and Cystamine

Cysteamine (2-aminoethanethiol) inhibited cell division in synchronously dividing cultures of Euglena gracilis at relatively low concentrations (0.005 M), Cystamine (2,2′-dithiobis(ethylamine). however, was only partially inhibitory at high concentrations (0.1 M). This differential inhibition may reflect certain unique features of nuclear division in euglenoid flagellates.