A Size‐Selective Intracellular Delivery Platform

Identifying and separating a subpopulation of cells from a heterogeneous mixture are essential elements of biological research. Current approaches require detailed knowledge of unique cell surface properties of the target cell population. A method is described that exploits size differences of cells to facilitate selective intracellular delivery using a high throughput microfluidic device. Cells traversing a constriction within this device undergo a transient disruption of the cell membrane that allows for cytoplasmic delivery of cargo. Unique constriction widths allow for optimization of delivery to cells of different sizes. For example, a 4 μm wide constriction is effective for delivery of cargo to primary human T‐cells that have an average diameter of 6.7 μm. In contrast, a 6 or 7 μm wide constriction is best for large pancreatic cancer cell lines BxPc3 (10.8 μm) and PANC‐1 (12.3 μm). These small differences in cell diameter are sufficient to allow for selective delivery of cargo to pancreatic cancer cells within a heterogeneous mixture containing T‐cells. The application of this approach is demonstrated by selectively delivering dextran‐conjugated fluorophores to circulating tumor cells in patient blood allowing for their subsequent isolation and genomic characterization.     

Investigation of the influence of swirl on a confined coannular swirl jet

Large Eddy Simulations are used to model a turbulent confined coannular combustor and examine the effects of swirl on the flow field and mixing. Three separate simulations with relatively high mesh resolutions and different swirl numbers have been carried out using a finite volume method on a Cartesian non-uniform structured grid. A localised dynamic Smagorinsky model is used to parameterize the sub-grid scale turbulence. The snapshots of the axial and swirl velocities and velocity vector fields show the complex flow patterns developing with increased swirl number and the rapid decay of axial momentum. Precessing vortex cores (PVC) were identified for all three cases and the mean axial velocity plots indicate that the upstream extremity of the vortex breakdown bubble shifts towards the inlet as the swirl number increases. The calculated power spectra indicate the distinct precession frequency for high swirl number. Probability density functions of axial velocity showed the changes of their distributions from approximately Gaussian to non-Gaussian with increased swirl number. The swirl has a large effect on the rate of decay of the axial velocity throughout the domain, whereas only has a significant effect on the decay of swirl velocity in the near field close to the jet inlet. The relation between swirl number and the axial extent of the recirculation zone is approximately linear. Radial plots of mean passive scalar and its variance also demonstrate an increase in the rate of mixing with increasing swirl number.     

Poly(hydroxyaminoethers): A New Family of Epoxy‐Based Thermoplastics

New epoxy‐based thermoplastics for barrier packaging are discussed here (see Figure). The polymers, poly (hydroxyaminoethers), are typically generated through reactions of various dinucleophiles with epoxy monomers. The effects of functionalization, branching, and copolymerization on the mechanical, adhesive, and barrier properties of these resins are reviewed.     

Comparing the characteristics of front and back domestic gardens in Hobart, Tasmania, Australia

In Australia, suburban front gardens have been said to be for show, while back gardens have been thought to be used more productively. This pattern may have changed as a result of a change in the ways that western suburbanites use and value their gardens. In 107 gardens in 10 suburbs of Hobart, Tasmania, Australia, data on the floristic composition, structural characteristics and some use attributes were collected from front and back yards. The floristic data were used to classify the yards into types, many of which preferentially occurred in either front or back. Back yards preferentially containing food plant taxa, and had a larger proportion of lawn, dogs and chicken coops, while front yards preferentially contained showy and screening plant taxa, and had relatively high small shrub cover. However, in a large proportion of properties, the garden type in the front yard was the same as the type in the back yard. In another large proportion of properties the front yard was gardened more intensively than the back, indicating a desire to impress, but the back yard was not used for productive purposes. These gardens preferentially occurred in the older suburbs, while gardens that were showier in the back than the front were negatively correlated with the unemployment rate. In a relatively small proportion of properties showy gardens were located in the front yard, while productive gardens were located in the back yard. The prevalence of these gardens had no relationships with suburb characteristics. The wide variety of garden types, and of their combinations in back and front yards, both within and between suburbs, indicate a complexity not reducible to simple aphorisms.     

Egg-sharing in assisted conception: ethical and practical considerations

The present acute shortage of eggs for donation cannot be overcome unless adequate guidelines are set to alleviate the anxieties regarding payments, in cash or kind, to donors. The current Human Fertilisation and Embryology Authority (HFEA) guidelines do not allow direct payment to donors but accept the provision of lower cost or free in vitro fertilization (IVF) treatment to women in recognition of oocyte donation to anonymous recipients. Egg-sharing achieved in this way enables two infertile couples to benefit from a single surgical procedure. However, the practical guidelines related to this approach are ill-defined at the present time leading to some justifiable uncertainty. A pilot study was therefore undertaken in order to establish the place of egg-sharing in an assisted conception programme. The current HFEA guidelines on medical screening of patients, counselling, age and rigid anonymity between the donor and recipient were followed. The study involved 55 women (25 donors and 30 recipients) in 73 treatment cycles involving fresh and frozen-thawed embryos. Donors were previous IVF patients who, regardless of their ability to pay, shared their eggs equally with matched anonymous recipients. They paid only for their consultations and tests right up to the point of being matched with a recipient. The sole recipient paid the cost applicable in egg donation of a single egg collection, although both received embryo transfers. The results indicate that although the recipients were older than the donors (41.4 +/- 0.9 versus 31.6 +/- 0.5 years), and there was no difference in the mean number of eggs allocated, the percentage fertilization rates, or the mean number of embryos transferred, there were more births per patient amongst recipients than amongst donors (30 versus 20%). We conclude that providing the donors are selected carefully, this scheme whereby a sub-fertile donor helps a sub-fertile recipient is a very constructive way of solving the problem of the shortage of eggs for donation. There are also the advantages of including a group of women who would otherwise be denied treatment. Problems related to 'patient coercion' can, in our view, be fully overcome by the application of strict common-sense safeguards. The ideal of pure altruism is not without its medical and moral risk. The success of egg-sharing depends on shared interests and a degree of altruism between the donor, the recipient and the centre. The current HFEA guidelines should be applauded for enabling a highly effective concept of mutual help to develop.     

Non-neuronal acetylcholine, a locally acting molecule, widely distributed in biological systems: expression and function in humans

Acetylcholine acts as a neurotransmitter in the central and peripheral nervous systems in humans. However, recent experiments demonstrate a widespread expression of the cholinergic system in non-neuronal cells in humans. The synthesizing enzyme choline acetyltransferase, the signalling molecule acetylcholine, and the respective receptors (nicotinic or muscarinic) are expressed in epithelial cells (human airways, alimentary tract, epidermis). Acetylcholine is also found in mesothelial, endothelial, glial, and circulating blood cells (platelets, mononuclear cells), as well as in alveolar macrophages. The existence of non-neuronal acetylcholine explains the widespread expression of muscarinic and nicotinic receptors in cells not innervated by cholinergic neurons. Non-neuronal acetylcholine appears to be involved in the regulation of important cell functions, such as mitosis, trophic functions, automaticity, locomotion, ciliary activity, cell-cell contact, cytoskeleton, as well as barrier and immune functions. The most important tasks for the future will be to clarify the multiple biological roles of non-neuronal acetylcholine in detail and to identify pathological conditions in which this system is up- or down-regulated. This could provide the basis for the development of new therapeutic strategies to target the non-neuronal cholinergic system.     

Alteration of vascular endothelium and endothelium smooth muscle interaction after carbogen gas perfusion of isolated rat and guinea pig heart

The aim of the study was to alter the vascular endothelium of the mammalian myocardium with respect to coronary flow regulation and vascular permeability. For this purpose, carbogen gas perfusion (GP) of Langendorff-type isolated rat and guinea pig heart was chosen. Perfusion of the hearts with carbogen gas was possible, as well as replacement of the GP by fluid perfusion. The energetic and mechanical state, the creatine kinase release, and the electron microscopic examination of the rat heart indicated only a moderate to minimal alteration of the cardiomyocytes after GP. As a result of GP a massive alteration of the vascular endothelium could be demonstrated in the rat heart, based on the release of the cytosolic endothelial marker enzyme, purine nucleoside phosphorylase, the partly altered vascular permeability and the morphologically detected endothelial damage to arterioles, capillaries and venules. Moreover, the reduced coronary flow response to short periods of anoxia (rat, guinea pig) and the inverted flow response to serotonin administration with maintained response to sodium nitroprusside (rat) in the post-gas perfusion period reflected an alteration of endothelial smooth muscular interaction in the rat and guinea pig heart. Furthermore, the distensibility of the coronary vasculature was increased in the rat and guinea pig heart in the post-gas perfusion period, where a relative autoregulatory behavior was maintained (rat) or partly maintained (guinea pig) in passively predilated vessels. In conclusion, carbogen gas perfusion of isolated hearts allows to induce preferred alteration of endothelium and endothelium-smooth muscle interaction.     

Influence of Sn Grain Size and Orientation on the Thermomechanical Response and Reliability of Pb-free Solder Joints

The size and crystal orientation of Sn grains in Pb-free, near eutectic Sn-Ag-Cu solder joints were examined. A clear dependence of the thermomechanical fatigue response of these solder joints on Sn grain orientation was observed (Sn has a body centered tetragonal crystal structure). Fabricated joints tend to have three orientations in a cyclic twin relationship, but among the population of solder balls, this orientation triplet appears to be randomly oriented. In thermally cycled joints, solder balls with dominant Sn grains having the particular orientation with the c-axis nearly parallel to the plane of the substrate were observed to fail before neighboring balls with different orientations. This results from the fact that the coefficient of thermal expansion of Sn in the basal plane (along the alpha-axis) is half the value along the c-axis; joints observed to be damaged had the maximum coefficient of thermal expansion mismatch between solder and substrate at the joint interface, as well as a tensile stress modes during the hot part of the thermal cycle. Localized recrystallization was observed in regions of maximum strain caused by differential expansion conditions, and its connection with crack nucleation is discussed.     

Experimental approaches to study vascularization in tissue engineering and biomaterial applications

The success of tissue engineering and biomaterial applications is not only dependent on the growth and functioning of the organ- or tissue-specific cells on the biomaterial but is entirely dependent in most cases on a successful vascularization after implantation. The process of vascularization involves angiogenesis; the formation of new blood vessels which spread into the implant material and supply the existing cells with the nutrients to survive. We have established in vitro methods using human microvascular endothelial cells to evaluate novel biomaterials for endothelial cell attachment, cytotoxicity, growth, angiogenesis and the effects on gene regulation. These in vitro studies can be used to rapidly evaluate the potential success of a new biomaterial and for the development of matrix scaffolds which will promote a physiological vascularization response.