Modulation of [3H]Diazepam Binding in Rat Cortical Membranes by GABAA Agonists

GABAA receptor agonists modulate [3H]diazepam binding in rat cortical membranes with different efficacies. At 23 degrees C, the relative potencies for enhancement of [3H]diazepam binding by agonists parallel their potencies in inhibiting [3H]gamma-aminobutyric acid [( 3H]GABA) binding. The agonist concentrations needed for enhancement of [3H]diazepam binding are up to 35 times higher than for [3H]GABA binding and correspond closely to the concentrations required for displacement of [3H]bicuculline methochloride (BMC) binding. The maximum enhancement of [3H]diazepam varied among agonists: muscimol = GABA greater than isoguvacine greater than 3-aminopropane sulphonic acid (3APS) = imidazoleacetic acid (IAA) greater than 4,5,6,7-tetrahydroisoxazolo (4,5,6)-pyridin-3-ol (THIP) = taurine greater than piperidine 4-sulphonic acid (P4S). At 37 degrees C, the potencies of agonists remained unchanged, but isoguvacine, 3 APS, and THIP acquired efficacies similar to GABA, whereas IAA, taurine, and P4S maintained their partial agonist profiles. At both temperatures the agonist-induced enhancement of [3H]diazepam binding was reversible by bicuculline methobromide and by the steroid GABA antagonist RU 5135. These results stress the importance of studying receptor-receptor interaction under near-physiological conditions and offer an in vitro assay that may predict the agonist status of putative GABA receptor ligands.     

Identification and characterization of DNA clones encoding group-II glycinin subunits

Summary DNA clones that encode the group-II subunits of soybean glycinin were identified and compared with clones for group-I subunits. The group-I clones hybridize weakly to those from group-II at low stringency, but fail to hybridize with them at moderate or high stringency. The genes for the group-II subunits are contained in 13 and 9 kb EcoRI fragments of genomic DNA in cultivar CX635-1-1-1. These fragments contain genes for subunits A₅A₄B₃ and A₃B₄, respectively. The larger size of mature group-II subunits compared with group-I subunits is correlated with a larger sized mRNA. However, the gross arrangement of introns and exons within the group-II coding regions appears to be the same as for the genes which encode group-I subunits. Messenger RNA for both groups of glycinin subunits appear in the seed at the same developmental interval, and their appearance lags slightly behind that of mRNAs for the a/a subunits of -conglycinin. These data indicate that the glycinin gene family is more complex than previously thought.Abbreviations bp base pairs - kb kilobase pairs - SDS sodium dodecyl sulfate Cooperative research between USDA/ARS and the Indiana Agric. Expt. Station. This work was supported in part by grants from the USDA Competitive Grants Program and the American Soybean Association Research Foundation. This is Journal Paper No. 10,078 from the Purdue Agricultural Experiment Station     

Segregational instability of pUB110-derived recombinant plasmids in Bacillus subtilis

To study plasmid instability in Bacillus subtilis the pUB110-derived hybrid plasmid pLB2 (3.6 kb) and the bifunctional replicon pLB5 (5.9 kb), able to replicate in B. subtilis and Escherichia coli, were constructed. In both vectors homologous B. subtilis, or heterologous E. coli DNA fragments of various lengths were inserted. Irrespective of the source of the cloned DNA, the segregational stability of the recombinant plasmids in B. subtilis was severely affected by the DNA inserts. In contrast, no instability was observed in E. coli. In B. subtilis a steep inverse relationship existed between the size of the inserts and the level of stability. Increased size of the pLB plasmids resulted in strongly reduced copy numbers. This seems to be the primary cause of the size-dependent segregational instability.     

Effects in chicks of arsenic,arginine, and zinc and their interaction on body weight,plasma uric acid,plasma urea,and kidney arginase activity

The interaction among arsenic, zinc, and arginine was studied in chicks using two fully crossed, three-way, two-by-two-by-two experiments. Arsenic at levels of 0 and 2 μg/g zinc at levels of 2.5 (zinc-deficient) and 25 (zinc-adequate) μg/g, and arginine at levels of 0 and 16 mg/g were supplemented to the diet. After 28 d in both experiments, growth was depressed in chicks fed diets either supplemented with arginine or deficient in zinc. Arsenic deprivation depressed growth of chicks fed diets containing the basal level of arginine and 25 μg supplemental Zn/g. Arsenic deprivation had little or no effect on growth of zinc-deprived chicks fed diets containing the basal level of arginine, or in zinc-deprived or zinc-adequate chicks fed supplemental arginine. Zinc-deficiency elevated urea in plasma and arginase activity in kidney. Those elevations, however, were more marked in arsenic-supplemented than in arsenic-deprived chicks. Also, plasma urea and kidney arginase activity were markedly elevated in chicks fed supplemental arginine; the elevations were more marked in zinc-deficient chicks. These findings support the concept that arsenic has a physiological role, associated with zinc, that can influence arginine metabolism in the chick.     

An immunocytochemical study of the optic ganglia of the crayfish Astacus leptodactylus (Nordmann 1842) with antisera against biologically active peptides of vertebrates and invertebrates

Summary The peptidergic system in the optic ganglia of Astacus leptodactylus is characterized by the immunocytochemical application of 15 antisera raised against biologically active peptides of vertebrates and invertebrates. Positive reactions were found with anti-FMRFamide, antiMSH, anti-vasotocin, anti-gastrin, anti-CCK, anti-oxytocin, anti-secretin, anti-glucagon and anti-GIP. Based on immunochemical reaction and localization it is possible to distinguish 30 cell groups. Only part of these cell groups is found in the known classical neurosecretory cell regions. This observation demonstrates a more extensive peptidergic system than formerly recognized. The morphology of this peptidergic system suggests that one part is neurohormonal and the other part neurotransmitter-like or neuromodulatory.     

Simplified purification and testing of colloidal gold probes

A novel efficient method for purifying and testing colloidal gold probes has been developed. The method consists of concentrating colloidal gold particles conjugated to IgG or protein A in dialysis bags over silica gel and purifying them by gel chromatography on small columns of Sephacryl S-400. Fractions collected are tested by paper immunocytochemical models. Comparisons to gold probes purified by conventional ultracentrifugation documents that ultrastructural staining intensities and total yield of gold probes is the same, but that the chromatographically purified gold probes are less prone to aggregation or clumping. The method has been extensively used for preparing conjugates of 5, 10 or 15 nm gold particles with antirabbit immunoglobulins but has also been exploited for preparing streptavidin-gold conjugates, protein A-gold conjugates and antirabbit immunoglobulin-silver conjugates.     

Effect of cholera toxin on rat intestinal permeability assessed with fluorescent dextran 3000

Abstract The effect of culture filtrate containing cholera toxin (CT) on rat intestinal permeability was studied using fluorescein isothiocyanate-labelled dextran 3000 (FITC-D3, M _r, 3000) as probe molecule. CT was given either perorally, via a gastric tube 90 min before, or locally in conjunction with the permeability measurement in the distal ileum. Compaired to the control animals, either mode of administration resulted in increased permeation of FITC-D3 from the intestine to portal blood. The effect of the local treatment was apparent after 5–10 min and prevailed during the 60-min measurement period. The results indicate that CT not only affects net water transport at the intestinal mucosa but also the passage of larger molecules across the intestinal wall.     

Some synchorological aspects of basiphilous pine forests in Fennoscandia

Basiphilous pine forests and related birch forests are herb-and grass-rich forests on calcareous substrate. These forests are complex communities with floristic/ecological elements from different vegetation types occurring in a subtle micromosaic. These elements are e.g. species from acidophilous conifer forests, thermophilous forest-rim communities, calcareous shallow-soil and steppe communities, eutrophic wet meadows and fens, and in northern Fennoscandia also species from alpine Dryas heaths. Four associations are recognized in Fennoscandia: Convallario-Pinetum, Melico-Piceetum pinetosum, Peucedano-Pinetum and Epipacto atrorubentis-Betuletum. The main association is the Convallario-Pinetum, a widespread community in Fennoscandia and Estonia with a considerable floristic variation between the different regions. Examples of the floristic variation along west-east profiles and south-north profiles in Fennoscandia are presented. The basiphilous pine forest complex can be divided into a number of ecological types along the moisture and nutritional gradients. A further subdivision into geographical types (races) is presented.Nomenclature follows Lid (1974) for vascular plants, Nyholm (1954–1969) for musci and Dahl & Krog (1973) for lichens.     

Topoisomerase I has a strong binding preference for a conserved hexadecameric sequence in the promoter region of the rRNA gene from Tetrahymena pyriformis.

Topoisomerase I is in situ associated with DNaseI hypersensitive sites located in the promotor and terminator regions of the extrachromosomal rDNA in Tetrahymena thermophila at sites with sequences fitting the motif (sequence in text) Reconstitution experiments with purified topoisomerase I and cloned fragments of rDNA demonstrate that the enzyme exhibits the same binding and cleavage properties on naked DNA. These observations are striking as topoisomerase I previously has been found to exhibit low sequence specificity. The specific binding of the enzyme has an absolute requirement for divalent cations with a preference for Ca2+. The strong binding to the hexadecamer has been characterized by competition experiments, and it has been used to determine the molecular weight of the enzyme.