GROWTH FACTOR INTERACTIONS IN THE TISSUE CULTURE OF TUMOROUS AND NONTUMOROUS NICOTIANA GLAUCA-LANGSDORFFII

Schaeffer , Gideon W., Harold H. Smith and Marion P. Perkus . (Brookhaven Natl. Lab., Upton, N. Y.) Growth factor interactions in the tissue culture of tumorous and nontumorous Nicotiana glauca-langsdorffii. Amer. Jour. Bot. 50(8): 766–771. Illus. 1963.—Tissues representing tumorous and nontumorous Nicotiana glauca-langsdorffii were cultured on high (5 ×) and low (1 ×) concentrations of a modified White's basal medium containing 2.9 × 10^–6m indoleacetic acid. The growth responses of tissues of both the tumorous and nontumorous genotypes to supplements of kinetin, glutamine, inositol and nucleic acid constituents added singly and in all combinations were noted on high-salt media. The nucleic acid components inhibited growth and were omitted from low-salt media. The best growth response was observed with glutamine and inositol for tissues from the tumorous hybrid and with glutamine, inositol and kinetin in the nontumorous type. Kinetin was a distinct and consistent requirement for rapid growth of nontumorous tissues, but no appreciable kinetin effect could be observed with tissues from the tumorous genotype.     

Scopoletin and Polyphenol-Induced Lag in Peroxidase Catalyzed Oxidation of Indole-3-acetic Acid

The rate of initial indole-3-acetic acid (IAA) oxidation with horseradish peroxidase is modified with scopoletin, scopolin and other phenolic derivatives. In the presence of phenolics there is an initial lag phase in the oxidation. The early lag is dissipated enzymatically after which the rale of IAA oxidation again returns to normal. Chlorogenic and sinapic acids produce the longest lag periods of the compounds reported here, whereas the glucoside, scopolin, produced the least inhibition. Scopoletin is more than 10× as inhibitory as scopolin.     

Interaction of staphylococcal enterotoxin B with cell cultures of human embryonic intestine

Schaeffer, W. I. (Massachusetts Institute of Technology, Cambridge), J. Gabliks, and R. Calitis. Interaction of staphylococcal enterotoxin B with cell cultures of human embryonic intestine. J. Bacteriol. 91:21-26. 1966.-The cytotoxic effect of staphylococcal enterotoxin B upon human embryonic intestine cell cultures is characterized by retraction of cells from the monolayer. This is followed by clumping of the retracted cells to form clear areas in the monolayer and finally by sloughing of the clumps from the glass surface. The 50% effective dose of the toxin, determined by protein analysis of the cultures used in titration studies, was found to be between 40 and 60 mug/ml. The cytotoxic property of the enterotoxin was completely neutralized by 3.9 x 10(-5) ml of specific antitoxin per mug of toxin. The cytotoxicity was found to be slightly enhanced by 2.2 g of bicarbonate per liter of Eagle's basal medium (Earle's salt solution level), the absence of serum, the absence of penicillin and streptomycin, and the presence of 2.8 mmoles of calcium in the medium. The cytotoxicity was profoundly influenced by the age of the culture. No cytotoxicity was evident until after 2 days of growth had taken place, when the cell number was approximately 4.0 x 10(5) cells per culture.     

Platelet free calcium concentrations measured with fura-2 are influenced by the transmembrane sodium gradient

The influence of the transmembrane Na+ gradient on the intracellular free calcium concentration, [Ca2+]i, was studied in Sepharose gel-filtered platelets from healthy human subjects, using the Ca-sensitive fluorescent dye, fura-2. Raising the internal Na+ concentration, [Na+]i, by Na+ pump inhibition with 0.05 mM ouabain, without changing external Na+ did not cause a significant increase in [Ca2+]i. Substitution of extracellular Na+ by iso-osmolar sucrose induced a rapid (half-time about 2 min) and significant rise in [Ca2+]i; this effect was amplified in Na-loaded platelets. Partial restitution of external Na+ in these cells with increased [Ca2+]i promoted a significant and rapid Na+ concentration-dependent fall in [Ca2+]i; little decline in [Ca2+]i was observed if K+ was used instead of Na+. These observations represent in vitro evidence for the existence of a Na/Ca exchange mechanism in human platelets that may, in vivo, participate in the control of [Ca2+]i.     

MK-801 is a potent nematocidal agent. Characterization of MK-801 binding sites in Caenorhabditis elegans.

MK-801, an N-methyl-D-aspartate antagonist in mammalian brain tissue, is a potent nematocidal agent. Specific MK-801 binding sites have been identified and characterized in a membrane fraction prepared from the free-living nematode Caenorhabditis elegans. The high-affinity MK-801 binding site has an apparent dissociation constant, Kd, of 225 nM. Unlike the MK-801 binding site in mammalian tissues, the C. elegans binding site is not effected by glutamate or glycine, and polyamines are potent inhibitors of specific MK-801 binding.     

A chemiluminescent assay for measuring avermectin binding sites

Avermectins are potent, broad spectrum anthelmintics. We describe the synthesis of a biologically active chemiluminescent compound, 22,23-dihydroavermectin B1a, 4"-[4-[[4-[ethyl(1,2,3,4-tetrahydro-1,4-dioxo-6- phthalazinyl)amino]butyl]amino]-4-oxobutanoate] (ivermectin-luminol). This compound retains its anthelmintic properties and provides an extremely sensitive nonradioactive probe to study avermectin binding sites.