Search

Several letters to the editor are presented in response to articles in previous issues including the possibility of a dedicated polar lunar lander, the importance of mentoring to promote science, and an account of working with Frank Klatt who wrote a letter about the XF-103.

The article comments on several articles and topics discussed in earlier issues. It is opined that the article "What Has 35 Years of Acquisition Reform Accomplished?" by T. Christie deserves commendation. It is accurate and informative. The articles "American Shipbuilding: An Industry in Crisis" by M. Petters and "People, Product, and Performance: The Strengths of Shipbuilding" by M. Toner argue that financial uncertainty hurts the U.S. shipbuilding industry and drives up costs. According to the authors the U.S. is no longer internationally competitive in manufacturing.

Presents letters to the editor referring to articles related to the U.S. Air Force. Facts about the last air attack on U.S. ground forces; Military's need for three variants of the F-35 aircraft; Missions conducted by the EB-66 crew during the Vietnam War.

One of the high affinity binding proteins for ammodytoxin C, a snake venom presynaptically neurotoxic phospholipase A(2), has been purified from porcine cerebral cortex and characterized. After extraction from the membranes, the toxin-binding protein was isolated in a homogenous form using wheat germ lectin-Sepharose, Q-Sepharose, and ammodytoxin-CH-Sepharose chromatography. The specific binding of (125)I-ammodytoxin C to the isolated acceptor was inhibited to different extents by some neurotoxic phospholipases A(2), ammodytoxins, bee venom phospholipase A(2), agkistrodotoxin, and crotoxin; but not by nontoxic phospholipases A(2), ammodytin I(2), porcine pancreatic phospholipase A(2), and human type IIA phospholipase A(2); suggesting the significance of the acceptor in the mechanism of phospholipase A(2) neurotoxicity. The isolated acceptor was identified as calmodulin by tandem mass spectrometry. Since calmodulin is generally considered as an intracellular protein, the identity of this acceptor supports the view that secretory phospholipase A(2) neurotoxins have to be internalized to exert their toxic effect. Moreover, since ammodytoxin is known to block synaptic transmission, its interaction with calmodulin as an acceptor may constitute a valuable probe for further investigation of the role of the latter in this Ca(2+)-regulated process.

Presents the author's experiences upon reading `Leaves of Grass' again as 1992 is the 100th anniversary of Walt Whitman's death and discusses how the poet Emily Dickinson sheds light on our attraction to Whitman, her opposite. Whitman's undercurrents; `Calamus'; Expression of Whitman's humility and doubt; Author's interest in how Dickinson rests on our appreciation of control, sincerity and trustworthiness.

The gamma subunits of heterotrimeric G proteins undergo post-translational prenylation and carboxylmethylation after formation of the betagamma dimer, modifications that are essential for alpha-betagamma, betagamma-receptor, and betagamma-effector interactions. We have determined the specific prenyl group present on the beta1gamma1, beta1gamma2, and beta1gamma3 dimers purified from baculovirus-infected Sf9 cells by specific binding to G protein alpha subunits immobilized on agarose. These recombinant dimers undergo the same post-translational modifications determined for gamma1 and gamma2 isolated from mammalian tissues. Furthermore, infection of Sf9 cells with a recombinant baculovirus encoding an alteration of the gamma1 CaaX sequence (gamma1-S74L) resulted in geranylgeranylation of the resulting gamma1 subunit, and alteration of the gamma2 CaaX sequence to CAIS (gamma2-L71S) resulted in farnesylation. Both of these altered gamma subunits were able to associate stably with beta1, and the resulting betagamma dimer bound tightly to alpha-agarose and eluted specifically with aluminum fluoride. These results indicate that Sf9 insect cells properly process the CaaX motif in G protein gamma subunits and are a useful model system to study the role of prenylation in the protein-protein interactions in which the betagamma subunits participate.

We have examined the effects of extracellular and intracellular Ca2+ concentrations upon basal and insulin-stimulated 2-deoxyglucose uptake in isolated rat adipocytes. In the absence of extracellular Ca2+, both basal and insulin-stimulated glucose uptake were significantly reduced. Insulin-stimulated glucose transport was optimal at 1 and 2 mM Ca2+. Further increases in extracellular Ca2+ concentration (3 mM) significantly diminished insulin-stimulated glucose uptake. When intracellular Ca2+ concentrations were augmented by ionomycin (1 microM), insulin-stimulated glucose uptake was significantly reduced at extracellular Ca2+ concentrations of 2 and 3 mM. The levels of intracellular free Ca2+ concentrations were then measured with Ca2+ indicator fura-2. The correlation between the levels of intracellular free Ca2+ and the magnitude of insulin-stimulated glucose uptake revealed that the optimal effect of insulin is observed at Ca2+ levels between 140 and 370 nM. At both extremes outside of this window, both low and high levels of intracellular Ca2+ result in diminished cellular responsiveness to insulin. These data suggest that intracellular calcium concentrations may exert a dual role in the regulation of cellular sensitivity to insulin. First, there must exist a minimal concentration of intracellular calcium to promote insulin action. Second, increased levels of intracellular calcium may provide a critical signal for diminution of insulin action.

Several letters to the editor are presented in response to articles in previous issues including "Gates Versus the Air Force," Boeing P-26 Peashooter, and "How Man Aircrew?" in the January 2014 issue.

Several letters to the editor are presented in response to articles in previous issues including "Learning to set a limit on health care," by Irving S. Shapiro in the February 14, 1983 issue, "Intergold: Buffing up the Krugerrand's image to restore some of its luster" in the January 17, 1983 issue, and "The nasty union battle at Allis" in the January 31, 1983 issue.