Determination of transmitter function by neuronal activity

The role of neuronal activity in the determination of transmitter function was studied in cultures of dissociated sympathetic neurons from newborn rat superior cervical ganglia. Cholinergic and adrenergic differentiation were assayed by incubating the cultures with radioactive choline and tyrosine and determining the rate of synthesis and accumulation of labelled acetylcholine and catecholamines. As in previous studies, pure neuronal cultures grown in control medium displayed much lower ratios of acetylcholine synthesis to catecholamine synthesis than did sister cultures grown in medium previously conditioned by incubation on appropriate nonneuronal cells (conditioned medium). However, here we report that neurons treated with the depolarizing agents elevated K+ or veratridine, or stimulated directly with electrical current, either before or during application of conditioned medium, displayed up to 300-fold lower acetylcholine/catecholamine ratios than they would have without depolarization, and thus remained primarily adrenergic. Elevated K+ and veratridine produced this effect on cholinergic differentiation without significantly altering neuronal survival. Because depolarization causes Ca2+ entry in a number of cell types, the effects of several Ca2+ agonists and antagonists were investigated. In the presence of the Ca2+ antagonists D600 or Mg2+, K+ did not prevent the induction of cholinergic properties by conditioned medium. Thus depolarization, either steady or accompanying activity, is one of the factors determining whether cultured sympathetic neurons become adrenergic or cholinergic, and this effect may be mediated by Ca2+

Feminist Empowerment Through the Internet

The University of Richmond\u27s upper division Political Science course, Women and Power in American Politics, has several ambitions. Among these is an exploration of the power of information technology to foster political research by and about women and to advance feminist political aims

Women\u27s Studies Student Questionnaire

The University of Richmond Women\u27s Studies program developed a student questionnaire in 1996 as part of larger program assessment project from 1993-1996

On the role of cyclic nucleotides in the transmitter choice made by cultured sympathetic neurons

Previous investigations have established that electrical activity or chronic depolarization influences the development of neonatal rat sympathetic neurons in dissociated cell culture. Depolarization reduces their ability to respond to a cholinergic inducing factor produced by non-neuronal cells, allowing normal adrenergic differentiation to proceed (Walicke, P., R. Campenot, and P. Patterson (1977) Proc. Natl. Acad. Sci. U. S. A. 74: 5767–5771). The present study examines whether the developmental effects of depolarization are mediated through cyclic nucleotides. Addition of dibutyryl cAMP, dibutyryl cGMP, adenosine, prostaglandin E1, and cholera toxin all raise neuronal cyclic nucleotide levels and qualitatively mimic the developmental effects of depolarization. However, the quantitative decrease in acetylcholine production caused by these cyclic nucleotide agents is much smaller than that caused by depolarization. Short (48-hr) exposures to the cyclic nucleotide derivatives do not alter transmitter synthesis, indicating that long term developmental changes are involved. Chronic depolarization with elevated K+ increases neuronal cAMP 2-fold but has little effect on cGMP. The increase in cAMP is maintained during several weeks of depolarization and is present as early as the 3rd day in vitro, preceding the significant alterations in adrenergic and cholinergic differentiation. Exposure to 2 mM theophylline also increases neuronal cAMP, but in contrast to the other agents, it enhances cholinergic differentiation. In combination with elevated Ktheophylline further increases neuronal cAMP but still favors cholinergic differentiation. Thus, although cAMP satisfies some criteria for being the second messenger in the developmental effects of depolarization, several findings are consistent with the nucleotide playing a central role: (i) Depolarization has much larger effects on transmitter choice than the cyclic nucleotide agents and (ii) theophylline can uncouple cyclic nucleotide levels from the developmental events

Effects of Sulfates in Water on Performance of Steers Grazing Rangeland

Surface and subsurface water in South Dakota often contains high concentrations of total dissolved solids (TDS) and sulfates, which, in severe cases, can cause livestock deaths. Data from our laboratory have demonstrated that sulfate concentrations of 3,000 ppm in water consumed by steers in dry-lot decreased ADG, feed intake, and water consumption. Little information is available on the effects of water sulfate concentrations on grazing livestock. This study evaluated the effects of water quality and two vegetation communities on the performance of steers grazing rangeland. Eight native pastures at the SDSU Cottonwood Research Station were used. Four pastures were dominated by warm-season shortgrasses (SG) and four by cool-season midgrasses (MG). Yearling steers (105/year) were allotted to pastures in 2001 and in 2002 to attain a moderate stocking rate of 0.50 AUM/acre during a 4-month grazing season. In 2002, cattle were removed after two months due to drought, resulting in a stocking rate of 0.25 AUM/acre. Number of cattle per pasture varied from 7 to 30, depending on pasture size. Cattle in two of the SG and two of the MG pastures received high sulfate water (HS, 2001: average = 3,947 ppm sulfates; 2002: average = 4,654 ppm sulfates) with low sulfate water (LS, 2001: average = 404 ppm sulfates; 2002: average = 441 ppm sulfates) provided in the remaining pastures. Average daily gain was greater for the LS steers than HS steers in 2001 (P = 0.003; 1.85 and 1.65 lb/d, respectively) and in 2002 (P = 0.001; 2.43 and 1.79 lb/d, respectively). An interaction between sulfate concentration in water and vegetation community in 2002 (P = 0.078) resulted from similar ADG for steers on SG (1.83 lb/d) and MG (1.74 lb/d) pastures for HS water, but greater ADG for steers on MG (2.54 lb/d) than SG (2.32 lb/d) pastures for LS water. During the two-year study, only one steer had health problems related to sulfur, with no deaths. Our study showed water with sulfate concentrations of 3,947 ppm and greater reduced ADG of grazing steers, and that the response was influenced by vegetation