Characterization of the DNA-binding properties of the receptor for 2,3,7,8-tetrachlorodibenzo-p-dioxin

The DNA-binding properties of the receptor for 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) were investigated using chromatography on DNA-cellulose columns. A maximal binding of about 40% of the total receptor complex to DNA-cellulose was observed. In order to interact with DNA, the receptor must first bind TCDD. A heat-activation step followed by gel permeation chromatography using Sephadex G-25 increased the binding of the cytosolic receptor to DNA. The DNA-binding ability of the receptor was almost lost following mild proteolysis using trypsin or alpha-chymotrypsin, although these treatments did not reduce its ligand binding capacity and had no apparent effect on its size. Furthermore, pre-treatment of the DNA-cellulose column with an intercalating drug, ethidium bromide, resulted in inhibition of the binding of the TCDD-receptor complex to DNA, indicating that not only electrostatic interactions but also the configuration of DNA are of importance in receptor-DNA interactions.     

Uptake and tissue distribution of manganese in the white sucker (Catostomus commersoni) under conditions of low pH

Concentrations of manganese were determined in the liver, kidney, muscle and bone of white suckers (Catostomus commersoni) from five acid (pH < 5.8), and two circumneutral lakes in south-central Ontario. Manganese tissue concentrations were greater in fish captured from the most acidified lakes with the greatest concentrations of dissolved manganese. These fish had increased concentrations of manganese in the liver, as indicated by a comparison of liver:kidney manganese concentration ratios among the seven fish populations. Tissue concentrations of manganese from all populations either were negatively correlated (P < 0.05) or remained constant with fish size indicating homeostatic regulation of this metal. Manganese concentrations of the benthic fauna were positively correlated to sediment concentrations (R=0.30). Lake sediment manganese concentrations were significantly correlated to maximum lake depth (R=0.80, P < 0.03), with the concentrations in the top 0–1 cm dependent on the redox conditions in the seven lakes. Based on the seven lakes studied, manganese concentrations in the benthic-feeding white sucker correlated better with dissolved manganese, than with either the concentrations in food or surficial sediments.     

Sugar utilization by developing wild type and shrunken-2 maize kernels

To characterize the movement of sugars during kernel development in maize, a newly devised in vitro kernel development scheme was utilized. Viable seeds of wild type maize (Zea mays L.) as well as the mutant shrunken-2 (sh2) were found to mature when grown in culture with reducing sugars or sucrose as the carbon source. However, wild type and sh2 kernels had greater germination, starch content, and seed weight when sucrose, rather than reducing sugars, was the carbon source. By the use of labeled sucrose it was shown that sucrose can move into endosperm tissue without intervening degradation and resynthesis. These results show that when grown in vitro the maize seed can utilize reducing sugars for development, but it prefers sucrose.     

A mathematical theory of size distributions in tissue culture

A model for growth of a tissue culture consisting of cell clumps is given. A set of equations for following the size distribution of clumps is used to determine total biomass accumulation. Existence and uniqueness of a solution to the equations is proved, and estimates of the biomass growth is given in a number of situations.     

Activation of m1 Muscarinic Acetylcholine Receptor Regulates τ Phosphorylation in Transfected PC12 Cells

Abstract: Hyperphosphorylated τ proteins are the principal fibrous component of the neurofibrillary tangle pathology in Alzheimer's disease. The possibility that τ phosphorylation is controlled by cell surface neurotransmitter receptors was examined in PC12 cells transfected with the gene for the rat m₁ muscarinic acetylcholine receptor. Stimulation of m₁ receptor in these cells with two acetylcholine agonists, carbachol and AF102B, decreased τ phosphorylation, as indicated by specific τ monoclonal antibodies that recognize phosphorylation-dependent epitopes and by alkaline phosphatase treatment. The muscarinic effect was both time and dose dependent. In addition, a synergistic effect on τ phosphorylation was found between treatments with muscarinic agonists and nerve growth factor. These studies provide the first evidence for a link between the cholinergic signal transduction system and the neuronal cytoskeleton that can be mediated by regulated phosphorylation of τ microtubule-associated protein.     

Proximity to seacoast: G. W. Field and the marine laboratory at Point Judith Pond,Rhode Island, 1896–1900

Conclusions By the time George Wilton Field concluded his work at the marine laboratory his initial scientific concerns had forced him directly into local politics. He pleaded with little success with the community of South Kingstown, and with no success with the town of Narragansett, to create and maintain a permanent breach:Is it not possible for the acute business sense and the broad philanthropy of the community to sweep aside petty, local, and personal jealousies which are now blocking practical progress for the establishment of a permanent breach at Point Judith Pond? It is truly criminal neglect which permits fifteen hundred acres of valuable water-farming area to lie practically idle and rapidly deteriorate with each passing year.... In the opinion of the writer the Point Judith Pond and those of similar type could be made the seat of oyster, clam, crab, herring, white perch, and striped bass fisheries.³⁰ In the summer of 1899 Field was invited to teach a summer course on echinoderms at the MBL in Woods Hole, and to conduct summer research in a laboratory of the U.S. Fish Commission, also located at Woods Hole. When the summer was over, he remained there. Whether he had intentions of returning to resume his position in Rhode Island is unclear. At this point all correspondence with the Agricultural Experiment Station ceases, and Field's last report is a brief statement in the annual report of the experiment station for 1900 wherein he laments the variety of experiments he has not been able to carry to conclusion, such as a study of the artificial fertilization of water analogous to the method of chemically fertilizing the land for crops.The correspondence reveals that the enthusiasm Field brought to Point Judith Pond in 1896 was gradually sapped by his own fragile health, by three years' exposure to the local politics surrounding the southern Rhode Island fishing industry, and by a college administration determined to remove the stench of his invertebrates. He sought a refuge in the sheltered world of pure research at the U.S. Fish Commission Laboratory, where he set out to investigate the Origin of Sex using, as his animal models, squid and toadfish.On November 14, 1899, the Board of Managers of the college ordered the director of the experiment station to dispose of the marine laboratory at Point Judith Pond.³¹ How long the laboratory at Buttonwood Point survived in the institutional memory of the University of Rhode Island is open to question. The current Graduate School of Oceanography, in the event, traces its history back to 1937, not 1896.Nevertheless, Field and his one-room marine station established a precedent of land-grant marine research that other state colleges would follow, including Rhode Island itself, which reestablished its marine station, this time permanently, at South Ferry in 1937. In his brief research career in Rhode Island, George Wilton Field had discovered the same coastal attributes that would lead later to the creation of one of the world's major marine research centers at the University of Rhode Island's Graduate School of Oceanography.And, in a measure of triumph for his work, little more than a year after Field left for Woods Hole and his laboratory was dismantled, the town of South Kingstown voted the funds necessary to begin the construction of a permanent breachway.³² Whether Field's scientific reasoning and the conclusions of his marine research played any part in finally deciding the thirty-year-old debate in the affirmative will probably never be known. What is evident is that Field had no patience for those who could not see the results of his research as clearly as he could himself.