Posttranslational control of membrane-skeleton (ankyrin and alpha beta- spectrin) assembly in early myogenesis

Adult chicken skeletal muscle cells express polypeptides that are antigenically related to alpha-spectrin (Mr 240,000) and beta-spectrin (Mr 220,000-225,000), the major components of the erythrocyte membrane- skeleton, and to ankyrin (Mr 237,000; also termed goblin in chicken erythrocytes), which binds spectrin to the transmembrane anion transporter in erythrocytes. Comparative immunoblotting of SDS- solubilized extracts of presumptive myoblasts and fully differentiated myotubes cultured in vitro demonstrated that there is a dramatic accumulation of ankyrin and alpha- and beta-spectrin during myogenesis and a concomitant switch in the subunit composition of spectrin from alpha gamma to alpha beta. Analysis of early time points in myogenesis (12-96 h) revealed that these changes occur shortly after the main burst of cell fusion. To determine the temporal relationship between cell fusion and the accumulation of ankyrin and alpha- and beta- spectrin, we treated presumptive myoblasts with 2 mM EGTA, which resulted in the complete inhibition of cell fusion. The incorporation of [35S]methionine into total protein and, specifically, into alpha-, gamma-, and beta-spectrin remained the same in EGTA-treated and control cells. Analysis by immunoblotting of the amounts of ankyrin and alpha- and beta-spectrin in fusion-blocked cells revealed that there was no effect on accumulation for the first 19 h. However, there was then a dramatic cessation in their accumulation, and thereafter, the amount of each protein at steady state remained constant. Upon release from the EGTA block, the cells fused rapidly (less than 11 h), and the accumulation of ankyrin and alpha- and beta-spectrin was reinitiated after a lag period of 3-5 h at a rate similar to that in control cells. The inhibition in the accumulation of newly synthesized ankyrin, alpha- spectrin, and beta-spectrin in EGTA-treated myoblasts was not characteristic of all structural proteins, since the accumulation of the muscle-specific intermediate filament protein desmin was the same in control and fusion-blocked cells. These results show that in myogenesis, the synthesis of ankyrin and alpha- and beta-spectrin and their accumulation as a complex, although concurrent, are not coupled events. We hypothesize that the extent of assembly of these components of the membrane-skeleton in muscle cells is determined by a control mechanism(s) operative at the posttranslational level that is triggered near the time of cell fusion and the onset of terminal differentiation

Avian lens spectrin: subunit composition compared with erythrocyte and brain spectrin

Chicken lens spectrin is composed predominantly of equimolar amounts of two polypeptides with solubility properties similar, but not identical, to erythrocyte spectrin. The larger polypeptide, Mr 240,000 (lens alpha- spectrin), co-migrates with erythrocyte and brain alpha-spectrin on one- and two-dimensional SDS polyacrylamide gels and cross-reacts with antibodies specific for chicken erythrocyte alpha-spectrin; the smaller polypeptide, Mr 235,000 (lens gamma-spectrin), co-migrates with brain gamma-spectrin and does not cross-react with either the alpha-spectrin antibodies specific for chicken erythrocyte beta-spectrin. Minor amounts of polypeptides antigenically related to erythrocyte beta- spectrin with a greater electrophoretic mobility than lens gamma- spectrin are also detected in lens. The equimolar ratio of lens alpha- and gamma-spectrin is invariantly maintained during the extraction of lens plasma membranes under different conditions, or after immunoprecipitation of whole extracts of lens with erythrocyte alpha- spectrin antibodies. Two-dimensional peptide mapping reveals that whereas alpha-spectrins from chicken erythrocytes, brain, and lens are highly homologous, the gamma-spectrins, although related, have some cell-type-specific peptides and are substantially different from erythrocyte beta-spectrin. Thus, the expression of cell-type-specific gamma- and beta-spectrins may be the basis for the assembly of a spectrin-plasma membrane complex whose molecular composition is tailored to the functional requirements of the particular cell-type

Potential of Pompano Mariculture in Florida

Pompano mariculture is not an attempt to bridge the protein gap, but it has been initiated to provide a constant source of this highly desired marine fish. The current market for pompano is small, however, this has been attributed basically to its supply. It appears from the literature that T. carolinus has the most dominant market position since it has an excellent flavor and sports fishermen prefer it due to its fighting ability when hooked on light tackle. It appears from the published history of attempts to raise pompano, by Berry and Iversen, that one of the major problems in a successful operation was proper construction

Joining of thirty three percent by weight random glass fibre reinforced polystyrene using variable frequency microwave

[Abstract]: This paper extends the range of applications for Variable Frequency Microwave (VFM) (2 – 18 GHz) facilities to joining thirty three percent by weight glass fibre reinforced polystyrene composite [PS/GF (33%)]. With a given power level, the composite was exposed to various exposure times to microwave irradiation. The primer or coupling agent used was 5-minute two-part adhesive containing 100% liquid epoxy and 8% amine, i.e. Araldite, which was more readily microwave reactive than the composite itself. Bond strengths of the joints were lap shear tested and results were compared with those obtained using fixed frequency (2.45 GHz) microwave processing. The VFMF was operated under software control, which provided automatic data logging facilities. The maximum lap shear bond strength of joint was 430 N/cm2 using variable frequency microwave facility while that obtained by fixed frequency microwave configuration was only 331 N/cm2. The former is nearly 30% stronger than the latter

Permittivity measurement of thermoplastic composites at elevated temperature

[Abstract]: The material properties of greatest importance in microwave processing of a dielectric are the complex relative permittivity Epsilon = Epsilon' - jEpsilon'', and the loss tangent, tan Delta = Epsilon'/Epsilon''. This paper describes two convenient laboratory based methods to obtain Epsilon', Epsilon'' and hence tan Delta of fibre-reinforced thermoplastic (FRTP) composites. One method employs a microwave network analyser in conjunction with a waveguide transmission technique, chosen because it provides the widest possible frequency range with high accuracy. The values of the dielectric constant and dielectric loss of glass fibre reinforced (33%) low density polyethylene, LDPE/GF (33%), polystyrene, PS/GF (33%), and Nylon 66/GF (33%), were obtained. Results are compared with those obtained by another method using a high-temperature dielectric probe

Thermo-mechanical performance of poly(lactic acid)/flax fibre-reinforced biocomposites.

In this study, the thermo-mechanical performance of flax fibre reinforced poly lactic acid (PLA) biocomposites was investigated for the potential use in load bearing application such as body-in-white and body structures in the automotive sector. Focus was given into the relationships between the thermal and mechanical properties, and the material response under different loading and environmental conditions. The strength (72. MPa) and stiffness (13. GPa) of flax/PLA composites investigated indicate a very promising material to replace traditional choices in load bearing application. The PLA's crystallinity was measured to approximately 27%. Annealing above 100. °C for an hour decreased that value to 30%, but analysis of tensile results of annealed specimens reveals a significant reduction of both the tensile strength and modulus. This reduction is associated with micro-cracking that occurred on the surface of PLA during the heating as well as deterioration of the flax properties due to drying. The study results show that strength and modulus increased with increasing strain rates, while elongation at break reduces respectively. A modulus of 22. GPa was recorded in 4.2. m/s crosshead velocity. Further, flax/PLA showed significantly higher modulus than flax/epoxy for the composites studied. Improvement of the interfacial bonding and the temperature characteristics, combined the thermoplastic nature of PLA, demonstrates that flax/PLA composites is ideal for use in structural automotive applications

Inverse problems from biomedicine: Inference of putative disease mechanisms and robust therapeutic strategies

Many complex diseases that are difficult to treat cannot be mapped onto a single cause, but arise from the interplay of multiple contributing factors. In the study of such diseases, it is becoming apparent that therapeutic strategies targeting a single protein or metabolite are often not efficacious. Rather, a systems perspective describing the interaction of physiological components is needed. In this paper, we demonstrate via examples of disease models the kind of inverse problems that arise from the need to infer disease mechanisms and/or therapeutic strategies. We identify the challenges that arise, in particular the need to devise strategies that are robust against variable physiological states and parametric uncertaintie

In-Plane Loading of Brick Veneer over Wood Shear Walls

In the design of wood stud walls with brick veneer, current design building codes specify that the wood stud wall should resist all in-plane and out-of-plane loads (IBC 2009). For out-of-plane loads, this assumption is entirely justified as the brittle brick veneer will crack and lose its capacity to resist bending. For in-plane loads, the brick veneer is significantly stiffer than the wood shear wall, and the veneer is unlikely to crack before the wood shear wall reaches its allowable capacity. The assumption that the wood shear wall resists the entire load is based on the further assumption that the ties which connect the stud wall to the veneer will be sufficiently flexible to not transfer significant loads. Research has shown that this is not the case for typical US residential construction practices. The brick veneer can, in fact, resist significant in-plane loads