Effect of adaptation level on maintained firing and sensitivity in receptive field center of X and Y cells

Summary Maintained firing rates of X cells and Y cells were compared at 6 adaptation levels (AL) between –2.71 log cd/m² and 2.28 log cd/m² (10 mm² pupil size). X cell maintained firing was higher at all ALs and was statistically different at medium and high ones. Changes in AL had nearly identical effects upon X and Y cell suprathreshold sensitivity to a flashing spot in the center of their receptive fields; the Weber function had a slope of 0.744 for Y cells and 0.743 for X cells. These values are not statistically different.This research is supported by Public Health Service grant no. EY 00701.     

Spatial distribution of signal and adaptive sensitivity in the receptive field surrounds of cat retinal ganglion cells

Summary A comparison was made between adaptive and signal sensitivity profiles of the surround response mechanism of cat retinal ganglion cells. The 2 profiles were found to be similar for X cells but the surrounds of Y cells appear to pool adaptation over a smaller retinal region than they pool signals. Acknowledgments. We wish to thank Mr O. Navarro for his valuable technical assistance. This research is supported by Public Health Service grant No. EY 00701.     

Spatial distribution of the adaptation field of the surround response mechanism in type X cat retinal ganglion cells

Summary The surround response mechanism in on-center X-cells in cat retina was found to be bimodally distributed and weak or nonexistent in the receptive field middle. An on-inhibition measure was used to assess surround mechanism gain.Acknowledgments. This research is supported by Public Health Service grant No. EY 00701.     

Spatial distribution of the adaptation field of the surround response mechanisms in type X cat retinal ganglion cells.

The surround response mechanism in on-center X-cells in cat retina was found to be bimodally distributed and weak or nonexistent in the receptive field middle. An on-inhibition measure was used to assess surround mechanism gain.     

Effect of cobaltous chloride on the blood sugar level and the islet cells in rats

Résumé L'effet de l'administration de chlorure de cobalt chez le rat normal est une hyperglycémie prononcée dans l'espace de quelques heures après l'injection. Il n'est pas possible de déceler des changements dans les cellules des îlots de Langerhans. Les noyaux des cellules ne montrent qu'une diminution faible après 24 h de l'injection.     

Effect of ricin,of its subunits and of modeccin on cAMP level in Yoshida ascites cells

Summary The B chain of ricin strongly decreases the PGE₁-enhanced level of cAMP in Yoshida ascites sarcoma cells, whereas the A chain is ineffective. Modeccin does not have any effect.Acknowledgments. We thank E. Lorenzoni for preparing ricin and modeccin. The work was aided by a contract from The Consiglio Nazionale delle Ricerche, Rome, within The Piano Finalizzato Controllo della crescita neoplastica and by Pallotti's legacy for cancer research.     

Effect of sodium butyrate in combination with X0irradiation,chemotherapeutic and cyclic AMP stimulating agents on neuroblastoma cells in culture

Summary Sodium butyrate, X-irradiation, chemotherapeutic agents and cyclic AMP-stimulating agents caused reduction in the cell number (due to cell death and reduction in cell division) when added individually to mouse neuroblastoma cells in culture. However, the combination of sodium butyrate with X-irradiation, chemotherapeutic and cyclic AMP-stimulating agents produced a greater reduction in the cell number than that produced by the individual agents.     

Effect of sodium butyrate on the interferon sensitivity of normal or cells transformed by murine sarcoma virus]

Sodium butyrate enhances the sensitivity of MSV transformed murine cells to interferon, but does not influence the response of normal cells. Sodium butyrate might act in transformed cells by restoring the different elements of the cytoskeletal system.     

Effect of preoperative stress on serum cholesterol level in humans

Summary Effect of preoperative stress on serum cholesterol level in 65 patients of different age groups in a surgical ward, has been studied. In all age groups, statistically significant rise of cholesterol in serum preoperatively was noticed as compared with serum cholesterol level at the time of discharge from hospital. The preoperative rise of cholesterol varied from 39 to 56.9% in this series. These findings support previous reports of the effect of mental tension on serum cholesterol level.Authors acknowledge with pleasure the useful discussions with Dr A. K. Ganguly, Prof. of Physiology, Government Medical College, Surat, Dr T. H. Rindani, Medical Director, Jaslok Hospital, Bombay. Statistical analysis by Shri P. Gopinath and technical assistance of Shri N. T. Pabani.     

P2X4 and P2X6 receptors associate with VE-cadherin in human endothelial cells

We investigated the expression of P2X₄ and P2X₆ receptors on human umbilical vein endothelial cells (HUVECs) and found that both P2X receptor subtypes on plasma membranes are largely restricted to areas of cell-cell contact. Co-labelling experiments at the confocal and electron microscopy levels revealed that P2X₄ and P2X₆ receptors are strongly co-localised with the cell adhesion molecule VE-cadherin. The P2X₄ and P2X₆ receptors on plasma membranes at cellular junctions are rapidly (within 5 min) internalised specifically after decreasing extracellular [Ca²⁺]. Disruption of microfilaments, microtubules and integrin-mediated adhesion or stimulation of P2 receptors with ATP did not alter P2X₄ and P2X₆ receptor expression on HUVEC plasma membranes. Membraneous P2X₄ and P2X₆ receptors resisted extraction with Triton-X 100, whereas cytoplasmic P2X receptors were Triton-X 100 soluble. P2X₄ receptors, but not P2X₆ receptors, could be co-immunoprecipitated with VE-cadherin and vice versa. We conclude that P2X₄ and P2X₆ receptors are associated with VE-cadherin at HUVEC adherens junctions. Received 15 March 2002; revised 15 March 2002; accepted 19 March 2002     

Interaction and interrelation of P2X7 and P2X4 receptor complexes in mouse lung epithelial cells

P2X4 and P2X7 receptors are ATP-gated ion channels that are co-expressed in alveolar epithelial type I cells. Both receptors are localized to the plasma membrane and partly associated with lipid rafts. Here we report on our study in an alveolar epithelial cell line of the molecular organization of P2X7R and P2X4R receptors and the effect of their knockdown. Native gel electrophoresis reveals three P2X7R complexes of ~430, ~580 and ~760 kDa. The latter two correspond exactly in size to signals of Cav-1, the structural protein of caveolae. Interestingly knockdown of P2rx7 affects protein levels, the intracellular distribution and the supramolecular organization of Cav-1 as well as of P2X4R, which is mainly detected in a complex of ~430 kDa. Our data suggest upregulation of P2X4R as a compensatory mechanism of P2X7R depletion.     

Effect of adrenal function on level of hepatic and extrahepatic arginase

Résumé On a constaté que l'arginase des reins est plus sensible que l'arginase du foie a l'hydrocortisone injecté. Au contraire, l'adrénalectomie provoque la réduction de l'activité arginasique du foie mais ne modifie pas le niveau de l'arginase rénale.     

Implication of GABA in the spatial organization of the receptive fields of retinal ganglia cells of frogs]

An histoautoradiographic study of the Chicken and Frog retinae was made following an intravitreal injection if tritiated GABA. This amino acid was especially fixed at the amacrine and horizontal cell level. It has been suggested (Werblin, 1974) that horizontal cells might be responsible for the spatial organization of the receptive fields of retinal ganglion cells. GABA could thus be involved in bringing about of the centre-surround arrangement of the latter receptive fields. We have shown that picrotoxin, a specific GABA-antagonist, does indeed provoke marked changes in the activity of retinal ganglion cells. It provokes a decrease in the response threshold, a facilitation of spontaneous activities, and a marked increase in the receptive field area of the ON-OFF ganglion cells: from 12 at the start, it reaches 24 under the effect of picrotoxin.     

Effect of growth factor deficiency on nystatin sensitivity inSaccharomyces cerevisiae

Summary The nystatin sensitivity, as well as the levels of total sterols and individual phospholipids ofSaccharomyces cerevisiae are influenced by variations in the supply of growth factors.