Acetylcholinesterase activity in anAedes aegypti cell line

Summary Considerable acetylcholinesterase (AChE) activity was detected in anAedes aegypti established cell line. The enzyme is blocked by 10^–6 M eserine sulfate, displays excess substrate inhibition and slowly hydrolyzes butyrylthiocholine. A 2-fold stimulation of AChE activity was shown after 2 days exposure to 3×10^–7 M -ecdysone. AChE activity found in the fresh medium is the contribution of the fetal calf serum portion. A direct relationship between levels of serum and the AChE activity in the cultured cells was demonstrated.Acknowledgment. I wish to thank Dr J. Peleg of the Israel Institute for Biological Research for providing the starting culture ofAedes aegypti cells.     

Distal-less encodes a homoeodomain protein required for limb development in Drosophila

The spatial organization of the Drosophila embryo depends on the activity of three axial pattern-forming systems. In addition to the anterior-posterior and dorsal-ventral systems that organize the segmented body plan, a proximal-distal pattern-forming system is required to provide positional information for the developing limbs. The development of both the larval and adult limbs depends directly on the activity of the Distal-less gene. Genetic analysis has shown that Distal-less functions as a developmental switch that is required to promote the development of limb structures above the evolutionary ground-state of body wall. Here we provide genetic evidence that indicates a graded requirement for Distal-less activity during limb development. Reduction of this activity has a global effect on pattern formation in the limb. The molecular structure of the Distal-less locus indicates that the gene encodes a homoeodomain-containing protein which is therefore likely to specify limb development through differential regulation of subordinate genes.     

Low LDL cholesterol in individuals of African descent resulting from frequent nonsense mutations in PCSK9

The low-density lipoprotein receptor (LDLR) prevents hypercholesterolemia and atherosclerosis by removing low-density lipoprotein (LDL) from circulation. Mutations in the genes encoding either LDLR or its ligand (APOB) cause severe hypercholesterolemia. Missense mutations in PCSK9, encoding a serine protease in the secretory pathway, also cause hypercholesterolemia. These mutations are probably gain-of-function mutations, as overexpression of PCSK9 in the liver of mice produces hypercholesterolemia by reducing LDLR number. To test whether loss-of-function mutations in PCSK9 have the opposite effect, we sequenced the coding region of PCSK9 in 128 subjects (50% African American) with low plasma levels of LDL and found two nonsense mutations (Y142X and C679X). These mutations were common in African Americans (combined frequency, 2%) but rare in European Americans (<0.1%) and were associated with a 40% reduction in plasma levels of LDL cholesterol. These data indicate that common sequence variations have large effects on plasma cholesterol levels in selected populations.     

Observation of random-phase lattice solitons

The coherence of waves in periodic systems (lattices) is crucial to their dynamics, as interference effects, such as Bragg reflections, largely determine their propagation. Whereas linear systems allow superposition, nonlinearity introduces a non-trivial interplay between localization effects, coupling between lattice sites, and incoherence. Until recently, all research on solitary waves (solitons) in nonlinear lattices has involved only coherent waves. In such cases, linear dispersion or diffraction of wave packets can be balanced by nonlinear effects, resulting in coherent lattice (or 'discrete') solitons; these have been studied in many branches of science. However, in most natural systems, waves with only partial coherence are more common, because fluctuations (thermal, quantum or some other) can reduce the correlation length to a distance comparable to the lattice spacing. Such systems should support random-phase lattice solitons displaying distinct features. Here we report the experimental observation of random-phase lattice solitons, demonstrating their self-trapping and local periodicity in real space, in addition to their multi-peaked power spectrum in momentum space. We discuss the relevance of such solitons to other nonlinear periodic systems in which fluctuating waves propagate, such as atomic systems, plasmas and molecular chains.