Vinculin is an essential component for normal myofibrillar arrangement in fetal mouse cardiac myocytes

Vinculin is a cytoskeletal protein that is believed to be an essential component in the linkage of cytoskeletal actin filaments to the plasma membrane. To investigate the precise function of vinculin in the development of cardiac myofibrils, antisense oligodeoxynucleotides complementary to vinculin mRNA were used to perturb the expression of the protein during myofibril assembly and arrangement in mouse cardiac myocytes. Fetal (day 18-20 post-conception) mouse cardiac myocytes were isolated by collagenase digestion, separated by Percoll density gradient centrifugation, and plated on aligned collagen gels. By 72 h of culture, mouse myocytes displayed an elongated in vivo-like phenotype in parallel with the aligned fibrils of the collagen gels with polarized arrays of myofibrils. Two different antisense oligonucleotides (20-mer) altered the formation of the tissue-like phenotype of myocytes. These antisense oligonucleotides suppressed vinculin protein expression at 43.5+/-26.8% and 48.7+/-20.9% when compared to myocytes that were not treated. Examination of these myocytes by confocal scanning laser and transmission electron microscopy revealed a disruption of the aligned in vivo-like phenotype, assembly of thick and thin filaments, and formulation of Z-bands. Random sequence 20-mer oligonucleotides used as controls had little detectable effect on vinculin protein expression (94.2+/-14.8%), cell shape, normal alignment or assembly of myofibrils. These results indicate that vinculin is a critical cytoskeletal component, that functions in the determination of cell shape and the arrangement and organization of developing myofibrils.     

Computing the Percentage Points of the Run-Length Distributions of Multivariate CUSUM Control Charts

Multivariate CUSUM control charts are often used instead of the standard Hotelling's control charts in many practical problems when detection of small shifts in the process mean is important. However, design of multivariate CUSUM control charts are usually based on the average run length (ARL). In this work, we will compute the percentage points of the run-length distributions of two multivariate CUSUM control charts. It will be shown that interpretations based on ARL can be misleading since the in-control run-length distribution of a multivariate CUSUM is highly skewed. On the other hand, the percentage points of the run-length distribution provide additional information such as the median run length, early false out-of-control signals, and the skewness of the run-length distribution for a particular scheme. These extra information might provide quality control engineers further knowledge of a particular multivariate CUSUM control chart scheme.     

Acquisition of a problem-solving skill: Levels of organization and use of working memory.

We examined the acquisition of a problem-solving skill at three levels of organization—strategy, subgoal, and operator—and investigated changes in temporary storage, manipulation of information, and coordination of multiple representations. 6 college students practiced minimizing the simulated cost of solving diagnostic problems with digital electronic circuits for approximately 50 hr (347 problems). Ss were tested on declarative knowledge, inferential skills at the subgoal level, and ability to solve problems during working memory tasks. The working memory tasks required retention of a preload, concurrent processing, or integration of displayed information with the contents of working memory. The data support the view that restructuring is goal sensitive and strategic. The results suggest a multiple-level analysis of skill acquisition in which practice allows strategic restructuring of cognitive processes at 3 levels of organization. Implications for models of skill acquisition and working memory are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Deformation and osmotic swelling of an elastic membrane capsule in Stokes flows by the immersed interface method

Although permeable and deformable capsules are found in many applications in biological and industrial systems, studies on computational modeling of these capsules are still rather lacking. In this work, the osmotic swelling of a deforming capsule immersed in a diluted binary solution of a non-electrolyte solute under Stokes flows is simulated using the immersed interface method (IIM). The approximate jump conditions for solute concentration are calculated with the use of the Kedem–Katchalsky relations. The capsule membrane is considered to be either semi-permeable or fully permeable, and the material of capsule membrane is assumed to be Neo-Hookean. The employed properties of fluid and membrane lie in the range of a typical biological system. The numerical validation tests indicate that the present calculation procedure has achieved good accuracy in modeling the swelling and deformation of permeable capsules. The capsule swelling (with mass transfer across the membrane) and deformation are tested for different solute concentration fields and membrane permeability properties. Our numerical investigations show that the initial solute concentration field and the membrane permeability properties have much influence on the swelling/deformation of a permeable capsule under Stokes flows.     

Geranoyl-CoA carboxylase: a novel biotin-containing enzyme in plants

Geranoyl-CoA carboxylase (EC 6.4.1.4) is a biotin-containing enzyme previously described in two genera of bacteria. Here we report the presence of geranoyl-CoA carboxylase in kingdom Plantae. Geranoyl-CoA carboxylase was purified 180-fold from maize leaves. The enzyme has a biotin-containing subunit of 122 kDa. The pH optimum for activity is 8.3. The apparent Km values for the substrates geranoyl-CoA, bicarbonate, and ATP are 64 +/- 5 microM, 0. 58 +/- 0.04 mM, and 8.4 +/- 0.4 microM, respectively. Subcellular fractionations indicate that geranoyl-CoA carboxylase is located in plastids. Geranoyl-CoA carboxylase activity is ubiquitous in organs of monocots and dicots and varies with development. We postulate that geranoyl-CoA carboxylase plays an important role in isoprenoid catabolism in plants, in a pathway analogous to that shown in Psuedomonas sp. In plants, this catabolic pathway would require the interaction of at least three subcellular compartments (plastids, microbodies, and mitochondria) and two biotin-containing enzymes, geranoyl-CoA carboxylase and 3-methylcrotonyl-CoA carboxylase.