Temperature dependence of metabolic processes in perfused rat liver (author''s transl)

The ruthenium red (RR) stained forelimb musculature of three species of urodeles Triturus (Notophthalmus) viridescens, Amblystoma maculatum, Amblystoma opacum in various stages of growth were examined with the electron microscope for the presence of satellite cells. It was found that RR staining facilitated greatly the identification of satellite cells. In young larvae of all three species satellite cells were detected with a frequency of 29% to 48% per total number of nuclei. In adult Triturus and Amblystoma maculatum satellite cells were no longer detected; instead "pericytes" as described by Hay ('74) were seen with a frequency of 12% and 3% respectively. During metamorphosis of Triturus satellite cells, with part of their myofiber-satellite cell intercellular space filled with basement membrane material, occurred at a peak frequency. The cells presumably are intermediate in the formation of "pericytes." At ten days after metamorphosis satellite cells and intermediate cells were no longer detected and the limb musculature contained only "pericytes" similar to the ones observed in adult newts. The significance of the presence of satellite cells in relation to limb regeneration and muscle regeneration is discussed.     

A model for the oxide growth stress and its effect on the creep of metals

A mathematical model is developed for the effect of the oxide growth stress upon the high temperature deformation of metal. The growth stress is modeled as a volumetric strain calculated from a modified Pilling-Bedworth ratio. The model is three-dimensional and allows the metal and the oxide scale to undergo both elastic and creep deformation during oxidation. The problems of oxidizing a flat plate, a solid rod, and a curved plate are formulated and solved. Experimental results for these geometries in the Ni-NiO system at 1000 °C are well predicted, both with and without an external load. The creep properties and the stress distribution in the NiO scale are calculated.     

Cellular localization of rheumatoid factor idiotypes

the stimulation of lymphocytes from rheumatoid arthritis patients with pokeweed mitogen produces a large number of plasma cells that express the dominant cross-reactive idiotype previously found on monoclonal IgM anti-gamma-globulins from patients with mixed cryoglobulinemia. Similar experiments with the cells of normal individuals show a much lower percentage of these cells with a lower intensity of staining with the fluorescent reagents utilized. Efforts to demonstrate rheumatoid factor in the same cells by fluorescent staining with aggregated gammaglobulin were entirely unsuccessful. This also proved to be the case for pokeweed mitogen-stimulated cells from the mixed cryoglobulinemic patients with large amounts of rheumatoid factor in the serum, despite high percentages of cells expressing the cross-reactive idiotype and also the individual idiotype. On the other hand, native plasma cells from synovial tissue of rheumatoid arthritis patients showed some cells with both the cross-reactive idiotype and aggregate staining. The exact reason for the failure to demonstrate rheumatoid factor by aggregate staining in pokeweed mitogen-stimulated cultures remains to be determined despite considerable effort to resolve the problem. The most likely possibility is that these plasma cells are relatively immature and have not accumulated polymeric IgM in their cytoplasm to the degree seen in synovial tissue plasma cells. The monomeric forms are readily recognized by the antiidiotypic antibodies and these reagents appear to be of particular value for cellular studies of this type.     

The effect of pressure on the electrical breakdown in the membranes of Valonia utricularis

The interpretation of electrical breakdown in terms of electro-mechanical instabilities, predicts that the breakdown potential should decrease with increasing cell turgor pressure. Experiments were conducted to test this hypothesis on cells of Valonia utricularis over a turgor pressure range of 0.5-10(5)-5.0-10(5) N/m2. Electrical breakdown was measured using intracellular electrodes and 500 mus current pulses. The pressure was monitored by an intracellular micropipette pressure transducer. The results obtained show a linear decrease in the critical breakdown potential with pressure. The effective compressive modulus of the cell membrane, gamma, is calculated from the slope of this line to 69+/-10-10(5) N/m2 (average value of seven measurements). This is consistent with the theoretical prediction of the electromechanical model using our previously determined values of the elastic modulus of the membrane. A theoretical analysis is given of the effects of pressure on the breakdown, This includes also considerations of the indirect effect of pressure on the membrane via stretching of the cell wall with a possible coupling of such strains to the cell membrane. The results and analysis presented allow us to conclude on the basis of the experimentally determined breakdown P.K. of 959 mV that the region of membrane where electrical breakdown occurs is a dielectric with one of the following combinations of parameters: (A) a thickness delta=7-9 nm with a dielectric constant epsilon=greater than 10, e.g. a hydrated protein spanning the whole membrane. (B) delta=4-5 nm with epsilon=3-8, e.g. a lipoprotein of lipid bilayer dimensions. (C) delta approximately 2 nm with epsilon=2-3, e.g. a half lipid bilayer. If we assume that the breakdown P.D. of the tonoplast and plasmalemma are identical, that is 480 mV, then there is only one reasonable choice for the membrane thickness and the dielectric constant: delta=2 nm, epsilon=3-8, e.g. a (lipo) proteinaceous module facing a half life lipid bilayer.     

Learned food aversion: A component of anorexia syndromes.

Suggests that several syndromes that have been characterized in terms of anorexia or appetite loss may actually be due, at least in part, to specific food aversion learning. Evidence reviewed by the present authors indicates that a number of experimental treatments, such as tumor implant and subdiaphragmatic vagotomy, that lead to anorexia in laboratory animals also lead to the development of specific aversions to the single available diet. These aversions appear to be responsible for a significant proportion of the ensuing reduction in food intake and body weight. The case for learned food aversions as a contributing factor in clinical problems of appetite loss is more speculative. However, there are certain clinical situations that provide the expected conditions for significant food aversion learning. A careful examination of dietary patterns of patients with these disorders is proposed as a first step toward evaluating the hypothesis that aversion learning is involved in the etiology or maintenance of clinically important anorexia. (104 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Polymer blends containing poly(vinylidene fluoride). Part I: Poly(alkyl acrylates)

The transitional behavior of poly(vinylidene fluoride) (PVF₂) blends with poly(methyl acrylate) and with poly(ethyl acrylate) was examined by differential thermal analysis and dynamic mechanical testing. Both blend systems were judged to be miscible on the bases of the presence of single, composition dependent glass transitions and of the strong melting point depression of the PVF₂ component, Blends of poly(isopropyl acrylate) with poly(vinylidene fluoride) were found to be immiscible. These results suggest that miscibility of the acrylate series depends on a specific attractive interaction between the PVF₂ and oxygen within the acrylate and the effect of this interaction is diminished as the hydrocarbon content of the ester is increased.