Mutually Independent Cyclic AMP and Sodium Responses to Nerve Growth Factor in Embryonic Chick Dorsal Root Ganglia

Abstract: Chick embryo dorsal root ganglia display a rapid and transient rise in their cyclic AMP content when presented with nerve growth factor. These ganglia also depend on nerve growth factor for control of their intracellular Na⁺ and K⁺ levels. A sequential relationship between the cyclic AMP and Na⁺ responses is not readily apparent. Incubation of chick sensory ganglia in a sodium-free medium does not prevent the cyclic AMP response to nerve growth factor from occurring. When ganglia are first incubated with ouabain for 6 h, presentation of nerve growth factor elicits a cyclic AMP response, but no Na⁺ response. The cyclic AMP response therefore does not depend on the Na⁺ environment. An initial presentation of nerve growth factor to the ganglia for 30 min, followed by its withdrawal and subsequent re-administration at different intervals over several hours failed to result in a second cyclic AMP response. Nevertheless, the expected Na⁺ behaviors were still observed. Dibutyryl cyclic AMP is capable of eliciting a cyclic AMP response in chick sensory ganglia after 6 h of nerve growth factor deprivation. When both agents were presented simultaneously to the ganglia, only a single cyclic AMP response was obtained, corresponding in time to the response elicited by dibutyryl cyclic AMP alone-indicating that this drug acts on the NGF-sensitive cells. At the same time dibutyryl cyclic AMP alone failed to result in a Na⁺ response, leading one to conclude that the cyclic AMP response to nerve growth factor is truly not mediating the Na⁺ response. Additional support for the mutual independence of these two short-latency responses is provided by the apparent inability of nerve growth factor to cause a cyclic AMP response in chick embryo sympathetic ganglia, another traditional target for the factor, which is capable of displaying a Na⁺ response.     

Quinuclidinyl Benzilate Binding in House Fly Heads and Rat Brain

Abstract: House fly heads contain a binding site for 3-quinuclidinyl benzilate (QNB) that is quite similar in pharmacology to the muscarinic acetylcholine receptor of vertebrate tissues. The house fly site binds [³H]QNB reversibly with a K _d of 260 PM and B_max of 1 pmol/g of heads from direct binding measurements. The K_d calculated from the ratio of the dissociation rate constant (2 × 10⁻⁴ sec⁻¹) to the association rate constant (2.5 × 10⁶ M⁻¹ Sec⁻¹) was 80 pM. The house fly site binds (-)quinuclidinyl benzilate preferentially, as do classic muscarinic receptors. The binding is also sensitive to other muscarinic antagonists and agonists. Nicotinic and other drugs are no more effective on the house fly site than they are on the rat brain muscarinic receptor itself. These binding studies suggest that the house fly QNB binding site is a muscarinic receptor.     

Effect of P and Mn on growth response and uptake of Fe,Mn and P by sorghum

Summary The effects of P and Mn on growth response and uptake of Fe, Mn and P by grain sorghum were investigated using nutrient culture. High P and Mn concentrations in solution (greater than 40 and 1 mg/l for P and Mn, respectively) markedly reduced plant height and shoot and root dry weight of 4-week-old sorghum plants. High Mn concentrations in solution increased the concentrations of Mn and P in shoot tissue and uptake of Mn, but depressed the uptake of P. High levels of P enhanced Mn uptake by sorghum and accentuated Mn toxicity at low Mn levels. The tissue Fe and total uptake of Fe were both reduced markedly by the high levels of P and Mn concentrations in solution. The increases of P, Mn and Fe concentrations in root tissue with a concomitant decrease of Fe in shoots suggested that the translocation of Fe from roots to shoots was hindered under high P and Mn conditions. Since coating occurred on root surfaces and intensified with increasing Mn concentrations in the substrate, part of the reduction of Fe in shoots could be attributed to the formation of high valent manganese oxides on the root surfaces which may retain Fe and reduce its absorption by sorghum.Contribution from the Department of Agronomy and Range Sci., University of California, Davis, CA.     

Effect of supraoptimal temperatures on the function of the subcortical fibrils and an endoplasmic factor inNitella internodes

Summary The effect of supraoptimal temperatures onNitella cells was studied with special reference to the function of subcortical fibrils and an endoplasmic factor. Local heat-treatment (50 °C for 1 minute) of an internodal cell ofNitella disclosed that 1. the subcortical fibrils in the treated area remain normal, not affected by the treatment, 2. the subcortical fibrils alone produce no cytoplasmic streaming, 3. the endoplasm contains an extremely heat-labile factor which is indispensable for streaming, and 4. the stagnant endoplasm in the heat-treated area is neither coagulated nor gelated by heat.Preliminary reports appeared in Proc. 37th Annu. Meet. Bot. Soc. Jpn. P. 160 (1972, in Japanese) and in Abst. Annu. Meet. Jpn. Soc. Cell Biol. p. 57 (1975, in Japanese).     

Regulation of Muscarinic Receptor-Mediated Cyclic GMP Synthesis by Cultured Mouse Neuroblastoma Cells

Mouse neuroblastoma clone N1E-115 has muscarinic acetylcholine receptors that mediate cyclic GMP synthesis. This receptor-mediated response is not significantly higher than background until the cells have been maintained in the stationary phase for at least 1 week. The basis of the influence of time in culture on the cyclic GMP response was investigated. The relative amount of cyclic GMP synthesized by intact cells was measured by radioactively labeling the GTP pool with [³H]guanine, incubating cells with agonists, and then chromatographically isolating [³H]cyclic GMP. Carbamylcholine-, ionophore X-537A-, and sodium azide-induced cyclic GMP formation increased with time in culture to a maximum of 13-, 9-, and 2.5-fold above basal, respectively. There was no change in the number or the apparent affinity of the muscarinic receptors as measured by [³H]quinuclidinyl benzylate ([³H]QNB) binding. In addition, there was no change in the apparent affinity of the receptors for agonist as measured by the ability of carbamylcholine to displace the specific binding of [³H]QNB. Guanylate cyclase activity per milligram protein and per cell in-creased six- and sevenfold, respectively, from day 0 to day 22. However, this increase in guanylate cyclase appeared to precede the marked increase in sensitivity of the cells to agonists. These data suggest that, in addition to guanylate cyclase and muscarinic receptors, there is another factor which is responsible for the development of this muscarinic receptor-mediated response.     

Nerve Growth Factor: Biological Significance, Measurement and Distribution

NGF proteins probably act as informational molecules transferred from end organs to the neurons of the sympathetic nervous system. The direct demonstration of the NGF content of most end organs requires assays more sensitive than those currently available. The high levels of NGF produced by some organs are probably of some other physiological significance.     

Effect of growth temperature upon heat sensitivity in Saccharomyces cerevisiae

The resistance of exponentially growing yeast cells to killing by exposure to 52°C increased markedly as the growth temperature was increased. Identical killing curves were obtained for cells suspended in growth medium or in 0.9% saline. Cells resistant to killing at 52°C were quite sensitive to killing at slightly higher temperatures. These results suggest a primary role for membrane damage in the mechanism of heat killing.     

Energy requirements for growth and maintenance of Scenedesmus protuberans Fritsch in light-limited continuous cultures

Scenedesmus protuberans Fritsch was grown in light-limited continuous cultures with a light-dark cycle, at temperatures of 20° and 28° C. At 20° irradiances of 12 and 38 W m^–2 were used, at 28° 38 W m^–2.The relationships between growth rate and light uptake rate were of diphasic linear character. With the lower growth rates the relationships were defined with the parameters _e , i.e. the specific maintenance rate constant, and c, the true efficiency of light energy conversion into biomass. The _e -value was dependent on temperature, the c on irradiance.In cultures, incubated in prolonged darkness, decrease rates of biomass were comparable to the derived _e -values.Both diphasic linear relationships between growth rate and light uptake rate and the same order of magnitude of _e -values could be derived from literature data on other green algae.     

Ultrastructural immunocytochemical localization of prolactin and growth hormone in the porcine pituitary

Summary The immunocytochemical peroxidase-antiperoxidase technique was used to identify prolactin- and growth hormone-producing cells in the porcine pituitary at the ultrastructural level. The growth hormone-producing cells contain round secretory granules (300 nm to 500 nm in diameter). The prolactin-producing cells can be identified by their distinct round and ovoid secretory granules which vary in size. Most of these cells contain large granules (450 nm to 750 nm in diameter), but some prolactin-producing cells display smaller secretory granules (250 nm to 500 nm). The two hormones were localized exclusively in the secretory granules. Staining for prolactin was observed in round and ovoid granules, as well as in small and polymorphic granules within the Golgi complex. This study confirmed (i) that the two hormones are located in different cells, and (ii) that under normal physiological conditions no one cell can synthesize and store both hormones simultaneously.     

Immuno-electron microscopic identification of somatostatin in cells and axons of sympathetic ganglia in the guinea pig

Summary The superior cervical ganglia (SCG), celiac superior mesenteric ganglia (CMG), and splanchnic nerve of unoperated guinea pigs, as well as both proximal and distal stumps of a previously transected branch of the postganglionic plexus of the CMG, were immunostained for somatostatin (SS). In addition, the PAP technique was adapted for fine-structural visualization of SS. A greater proportion of cells were labeled for SS in the CMG than in the SCG. PAP molecules were present in one type of intraganglionic axons. Only two labeled axons were found in the splanchnic nerve. Neither proximal nor the distal stump of the transected CMG postganglionic nerve contained labeled axons. The present results support the hypothesis that the intraganglionic axons labeled for SS arise from SS-containing intraganglionic neurons.