ALBERT

Notes: Abstract The crystal structure of 2,4-dinitronaphthyl-2′,6′-dimethylphenyl ether, C18H14N2O5, has been determined by three-dimensional x-ray methods, as part of a study of hindered aryl ethers. The crystals are monoclinic, space groupP21/c witha = 13.416(1),b = 8.479(1),c = 14.808(2) Å, β = 111.65(1) ° andZ = 4. The structure was solved by direct methods using program REL and was refined by full-matrix least squares to anR value of 0.050. The torsion angles that describe the diphenyl ether conformation are 60/22 ° for C2′-C1′-O1-C1/C1′-O1-C1-C2, respectively. The average torsion angles for other naphthalene phenyl ethers are 65/25 °. There are no hydrogen bonds in this structure.

Notes: Abstract The infrared spectra of the isostructuralMVO3 compounds (M=K, Rb, Cs, Tl, NH4), consisting in an array of infinite tetrahedral chains, are reported and discussed with the aid of a simplified factor group analysis. In the case of NH4VO3 also the laser-Raman spectrum was recorded and analyzed. Force constants, mean amplitudes of vibration and other bond properties for the terminal VO2 groups, as well as for the VOV chain units are estimated.

Notes: Summary In this paper we describe a method for the estimation of global errors. An heuristic condition of validity of the method is given and several applications are described in detail for problems of ordinary differential equations with either initial or two point boundary conditions solved by finite difference formulas. The main idea of the method can be extended to other type of problems and applications to a problem solved by spline functions and to some partial differential equations solved by finite differences methods are outlined.

Notes: Summary Field studies of dispersal by first instar gypsy moth larvae indicate that almost all larvae undergo an initial dispersal episode. However, in laboratory studies large larvae (from large eggs) disperse more frequently than small larvae (from small eggs) in the presence of favored food. Large larvae may be better adapted for dispersal. When larvae encounter unacceptable food or are denied food, larvae disperse more frequently and dispersal by small larvae is nearly as frequent as dispersal by large larvae. Factors affecting egg size may contribute to shifts in dispersal patterns of gypsy moth larvae and distribution of populations.

Notes: Summary The possibility that sodium from the serosal bathing medium “back-diffuses” into the active sodium transport pool within the mucosal epithelial cell of the isolated toad bladder was examined by determining the effect on the metabolism of the tissue of removing sodium from the serosal medium. It was expected that if recycling of serosal sodium did occur through the active transepithelial transport pathway of the isolated toad bladder, removal of sodium from the serosal medium would reduce the rate of CO2 production by the tissue and enhance the stoichiometric ratio of sodium ions transported across the bladder per molecule of sodium transport dependent CO2 produced simultaneously by the bladder (J Na/J CO 2). The data revealed no significant change in this ratio (17.19 with serosal sodium and 16.13 after replacing serosal sodium with choline). Further, when transepithelial sodium transport was inhibited (a) by adding amiloride to the mucosal medium, or (b) by removing sodium from the mucosal medium, subsequent removal of sodium from the serosal medium, or (c) addition of ouabain failed to depress the basal rate of CO2 production by the bladder [(a) rate of basal, nontransport related, CO2 production (J CO2 b ) equals 1.54±0.52 with serosal sodium and 1.54±0.37 without serosal sodium; (b)J CO2 b equals 2.18±0.21 with serosal sodium and 2.09±0.21 without serosal sodium; (c) 1.14±0.26 without ouabain and 1.13±0.25 with ouabain; unite ofJ CO2 b are nmoles mg d.w.−1 min−1]. The results support the hypothesis that little, if any, recycling of serosal sodium occurs in the toad bladder.

Notes: Summary The irreversible activation of adenylate cyclase by 5′ guanylylimidodiphosphate, a phosphoramidate analog of 5′GTP, has been examined in toad (Bufus marinus) plasma membranes using the technique of preincubating the membranes with the nucleotide under various controlled conditions followed by washing and subsequent assay of enzyme activity. Activation of adenylate cyclase by Gpp(NH)p, but not GTP, is essentially permanent and persists following extensive washing, prolonged incubation at 30°C in the absence of the nucleotide, and after dissolution of the membranes with Lubrol PX. (−)-Isoproterenol increases the activation observed with maximal concentrations of Gpp(NH)p from eight- to 10-fold (in the absence of hormone) to 50- to 100-fold; final activities as high as 10–15 nmoles of cyclic AMP per min per mg protein are achieved. The activated state obtained with isoproterenol and Gpp(NH)p is also permanent and is not inhibited by propranolol. The synergism between Gpp(NH)p and hormone requires the simultaneous presence of these compounds, and the time-dependent enhancement of activation with (−)-isoproterenol may be interrupted by addition of propranolol. The stimulation is slow, and may proceed for as long as 45 min at 30°C in the presence of maximal concentrations of Gpp(NH)p and (−)-isoproterenol. Very little activation occurs at 0°C. The time course of activation at 30°C exhibits an accelerating phase lasting from 5 to 30 min when Gpp(NH)p is added directly during assay of cyclase activity or when the membranes are preincubated for various times and washed prior to assay for a fixed time. The lag period occurs in the presence and absence of (−)-isoproterenol, although the rate of increase in velocity is greater with hormone. The length of the accelerating phase decreases with increasing concentrations of Gpp(NH)p, although it is still evident with maximal levels of Gpp(NH)p and hormone. However, prewarming the membranes at 30°C for 10 min in the absence of Gpp(NH)p or (−)-isoproterenol results in an immediate onset of linear activation at a rate which is achieved in untreated membranes only after about 10 min. The events occurring during prewarming at 30°C are readily reversible since chilling the warmed membranes to 0°C results in a time course of activation identical to that of membranes maintained at 0°C until addition of Gpp(NH)p. Activation is proportional to the concentration of Gpp(NH)p within the range of 10−8 to 10−4 mm. The apparent affinity for Gpp(NH)p increases with increasing time of incubation. The primary effect of increasing the concentration of Gpp(NH)p is to decrease the time required to obtain a maximal rate of activation. The possible relevance of these findings to the mechanism of action of Gpp(NH)p, adenylate cyclase and hormones is discussed within the context of current views of biological membranes which recognize the lateral mobility of membrane molecules.

Notes: Summary The permeability of red cell ghosts to K is determined by the amount of membrane-bound Mg which, in turn, depends on internal Mg. Contrasting with such effect, an increase in cellular Ca raises K permeability. To test whether this, action is due to a competitive displacement of membrane Mg, the free Ca content of human red cell ghosts was altered by means of Ca-EGTA buffers. Net Na and K movements as well as Ca and Mg bindings, were assessed after incubation in a Na-medium at 37°C. Raising Ca from 3×10−7 to 1×10−2M caused a large K efflux with very little Na gain. Under similar conditions, Ca binding was increased without affecting membranebound Mg. Both Ca binding and K loss were markedly diminished by either adding ATP to the hemolytic medium or increasing internal Mg at a fixed Ca concentration. A Scatchard analysis showed three Ca binding sites, two of them having high affinity. It is concluded that Ca action does not arise from a displacement of membrane-bound Mg but from binding to different sites in the membrane. Presumably, high affinity sites are involved in the control of K permeability.