Cardiac tamponade and central venous catheters.

An analysis of the reports on 16 patients who developed cardiac tamponade, complicating the use of central venous catheters, showed that 14 died. The two survivors were treated by removal of the catheter and needle aspiration of the pericardial fluid. Some patients complained of warning symptoms such as nausea, pain, and dyspnoea, and the combination of tachycardia, hypotension, and raised venous pressure was common. We suggest that awareness of the hazard, radiographic visualization of the catheter tip, and expeditious treatment would reduce the mortality.     

Phospholipase C-gamma mediates the hydrolysis of phosphatidylinositol, but not of phosphatidylinositol 4,5-bisphoshate, in carbamylcholine-stimulated islets of langerhans

In pancreatic islets the activation of phospholipase C (PLC) by the muscarinic receptor agonist carbamyolcholine (carbachol) results in the hydrolysis of both phosphatidylinositol 4,5-bisphosphate (PtdInsP(2)) and phosphatidylinositol (PtdIns). Here we tested the hypothesis that PtdIns hydrolysis is mediated by PLCgamma1, which is known to be regulated by activation of tyrosine kinases and PtdIns 3-kinase. PtdIns breakdown was more sensitive than that of PtdInsP(2) to the tyrosine kinase inhibitor, genistein. Conversely, the tyrosine phosphatase inhibitor, vanadate, alone promoted PtdIns hydrolysis and acted non-additively with carbachol. Vanadate did not stimulate PtdInsP(2) breakdown. Carbachol also stimulated a rapid (maximal at 1-2 min) tyrosine phosphorylation of several islet proteins, although not of PLCgamma1 itself. Two structurally unrelated inhibitors of PtdIns 3-kinase, wortmannin and LY294002, more effectively attenuated the hyrolysis of PtdIns compared with PtdInsP(2). Adenovirally mediated overexpression of PLCgamma1 significantly increased carbachol-stimulated PtdIns hydrolysis without affecting that of PtdInsP(2). Conversely overexpression of PLCbeta1 up-regulated the PtdInsP(2), but not PtdIns, response. These results indicate that the hydrolysis of PtdIns and PtdInsP(2) are independently regulated in pancreatic islets and that PLCgamma1 selectively mediates the breakdown of PtdIns. The activation mechanism of PLCgamma involves tyrosine phosphorylation (but not of PLCgamma directly) and PtdIns 3-kinase. Our findings point to a novel bifurcation of signaling pathways downstream of muscarinic receptors and suggest that hydrolysis of PtdIns and PtdInsP(2) might serve different physiological ends.     

Finite element analysis as a tool for parametric prosthetic foot design and evaluation. Technique development in the solid ankle cushioned heel (SACH) foot

In this study, we developed an approach for prosthetic foot design incorporating motion analysis, mechanical testing and computer analysis. Using computer modeling and finite element analysis, a three-dimensional (3D), numerical foot model of the solid ankle cushioned heel (SACH) foot was constructed and analyzed based upon loading conditions obtained from the gait analysis of an amputee and validated experimentally using mechanical testing. The model was then used to address effects of viscoelastic heel performance numerically. This is just one example of the type of parametric analysis and design enabled by this approach. More importantly, by incorporating the unique gait characteristics of the amputee, these parametric analyses may lead to prosthetic feet more appropriately representing a particular user's needs, comfort and activity level.     

Structurally distinct recognition motifs in lymphotoxin-beta receptor and CD40 for tumor necrosis factor receptor-associated factor (TRAF)-mediated signaling

Lymphotoxin-beta receptor (LTbetaR) and CD40 are members of the tumor necrosis factor family of signaling receptors that regulate cell survival or death through activation of NF-kappaB. These receptors transmit signals through downstream adaptor proteins called tumor necrosis factor receptor-associated factors (TRAFs). In this study, the crystal structure of a region of the cytoplasmic domain of LTbetaR bound to TRAF3 has revealed an unexpected new recognition motif, 388IPEEGD393, for TRAF3 binding. Although this motif is distinct in sequence and structure from the PVQET motif in CD40 and PIQCT in the regulator TRAF-associated NF-kappaB activator (TANK), recognition is mediated in the same binding crevice on the surface of TRAF3. The results reveal structurally adaptive "hot spots" in the TRAF3-binding crevice that promote molecular interactions driving specific signaling after contact with LTbetaR, CD40, or the downstream regulator TANK.     

Identification of Arabidopsis rat mutants

Limited knowledge currently exists regarding the roles of plant genes and proteins in the Agrobacterium tumefaciens-mediated transformation process. To understand the host contribution to transformation, we carried out root-based transformation assays to identify Arabidopsis mutants that are resistant to Agrobacterium transformation (rat mutants). To date, we have identified 126 rat mutants by screening libraries of T-DNA insertion mutants and by using various “reverse genetic” approaches. These mutants disrupt expression of genes of numerous categories, including chromatin structural and remodeling genes, and genes encoding proteins implicated in nuclear targeting, cell wall structure and metabolism, cytoskeleton structure and function, and signal transduction. Here, we present an update on the identification and characterization of these rat mutants.     

The parapineal mediates left-right asymmetry in the zebrafish diencephalon

The dorsal diencephalon (or epithalamus) of larval zebrafish displays distinct left-right asymmetries. The pineal complex consists of the pineal organ anlage and an unpaired, left-sided accessory organ - the parapineal. The neighboring brain nuclei, the left and right dorsal habenulae, show consistent differences in their size, density of neuropil and gene expression. Mutational analyses demonstrate a correlation between the left-right position of the parapineal and the laterality of the habenular nuclei. We show that selective ablation of the parapineal organ results in the loss of habenular asymmetry. The left-sided parapineal therefore influences the left-right identity of adjacent brain nuclei, indicating that laterality of the dorsal diencephalon arises in a step-wise fashion.     

Biomimetic bone mechanotransduction modeling in neonatal rat femur organ cultures: structural verification of proof of concept

The goal of this work was to develop and validate a whole bone organ culture model to be utilized in biomimetic mechanotransduction research. Femurs harvested from 2-day-old neonatal rat pups were maintained in culture for 1 week post-harvest and assessed for growth and viability. For stimulation studies, femurs were physiologically stimulated for 350 cycles 24 h post-harvest then maintained in culture for 1 week at which time structural tests were conducted. Comparing 1 and 8 days in culture, bones grew significantly in size over the 7-day culture period. In addition, histology supported adequate diffusion and organ viability at 2 weeks in culture. For stimulation studies, 350 cycles of physiologic loading 24 h post-harvest resulted in increased bone strength over the 7-day culture period. In this work, structural proof of concept was established for the use of whole bone organ cultures as mechanotransduction models. Specifically, this work established that these cultures grow and remain viable in culture, are adequately nourished via diffusion and are capable of responding to a brief bout of mechanical stimulation with an increase in strength.     

Transcriptome analysis of germinating maize kernels exposed to smoke-water and the active compound KAR<Subscript>1</Subscript>

Background  

Smoke released from burning vegetation functions as an important environmental signal promoting the germination of many plant species following a fire. It not only promotes the germination of species from fire-prone habitats, but several species from non-fire-prone areas also respond, including some crops. The germination stimulatory activity can largely be attributed to the presence of a highly active butenolide compound, 3-methyl-2H-furo[2,3-c]pyran-2-one (referred to as karrikin 1 or KAR₁), that has previously been isolated from plant-derived smoke. Several hypotheses have arisen regarding the molecular background of smoke and KAR₁ action.     

Ion channels in smooth muscle: regulation by the sarcoplasmic reticulum and mitochondria

In smooth muscle, Ca(2+) regulates cell division, growth and cell death as well as providing the main trigger for contraction. Ion channels provide the major access route to elevate the cytoplasmic Ca(2+) concentration ([Ca(2+)](c)) in smooth muscle by permitting Ca(2+) entry across the plasma membrane and release of the ion from intracellular Ca(2+) stores. The control of [Ca(2+)](c) relies on feedback modulation of the entry and release channels by Ca(2+) itself. Local rises in [Ca(2+)](c) may promote or inhibit channel activity directly or indirectly. The latter may arise from Ca(2+) regulation of ionic conductances in the plasma membrane to provide control of cell excitability and so [Ca(2+)](c) entry. Organelles such as mitochondria may also contribute significantly to the feedback regulation of ion channel activity by the control of Ca(2+) or redox status of the cell. This brief review describes the feedback regulation of Ca(2+) release from the internal Ca(2+) store and of plasma membrane excitability in smooth muscle.