Elastohydrodynamic separation of pleural surfaces during breathing

To examine effects of lung motion on the separation of pleural surfaces during breathing, we modeled the pleural space in two dimensions as a thin layer of fluid separating a stationary elastic solid and a sliding flat solid surface. The undeformed elastic solid contained a series of bumps, to represent tissue surface features, introducing unevenness in fluid layer thickness. We computed the extent of deformation of the solid as a function of sliding velocity, solid elastic modulus, and bump geometry (wavelength and amplitude). For physiological values of the parameters, significant deformation occurs (i.e. bumps are 'flattened') promoting less variation in fluid thickness and decreased fluid shear stress. In addition, deformation is persistent; bumps of sufficient wavelength, once deformed, require a recovery time longer than a typical breath-to-breath interval to return near their undeformed configuration. These results suggest that in the pleural space during normal breathing, separation of pleural surfaces is promoted by the reciprocating sliding of lung and chest wall.     

Electrophoretic fractionation of murine lymphoid cells. I. Enrichment of peripheral T lymphocyte subsets with distinct surface phenotypes

The purpose of this work was to evaluate the efficiency of free-flow electrophoresis as a method for separating mouse lymphocyte subsets. The surface phenotype of the cells contained in the various fractions collected after electrophoresis of CBA/J lymph node cells was investigated by means of single- and 2-color flow cytofluorometry (FCF) analysis. In agreement with previous works, B cells (sIg+, Thy-1-) were found to segregate in the low mobility (LM) fractions and T cells (sIg-, Thy-1+) in the high-mobility (HM) fractions. While the mean fluorescence intensity of sIg staining did not significantly vary as a function of electrophoretic mobility (EPM) that of Thy-1 staining tended to decrease with increasing EPM. The distribution of Lyt-1+ cells was roughly parallel to that of Thy-1+ cells. However, 2-color FCF analysis suggested the existence, in addition to a major Thy-1+ Lyt-1+ subpopulation, of a minor subset of Thy-1- Lyt-1+ cells. Lyt-2+ cells made up a peak in the cathodic HM region where they were enriched by up to 3-fold, and a trail in the more anodic HM fractions. Two-color FCF analysis showed that all Lyt-2+ cells recovered in these various electrophoretic fractions expressed the Lyt-1 antigen. Taken together, these data demonstrate that free-flow electrophoresis provides a powerful tool for the delineation and substantial enrichment of phenotypically distinct mouse peripheral T cell subsets.     

Vaccination of the Leishmania major susceptible BALB/c mouse. I. The precise selection of peptide determinant influences CD4+ T cell subset expression

BALB/c mice are susceptible to cutaneous lelshmanlasls uponinfection with Leishmania major while C57BL/6 are not. Thereis a major promastigote surface protease (PSP or gp63) whichis available in both native and recomblnant forms, and for whichthe primary amlno acid sequence is known. Immunization withPSP has been shown to offer some protection against challengewith the live organism. Therefore, we attempted to develop apeptide vaccine with PSP peptldes. In the first experiments,recall prollferatlve responses to PSP were measured using aset of 15mer peptldes spanning the entire PSP molecule whichallowed designation of major determinant regions in BALB/c,C57BL/6, and CBA mice. Several of these determinants were promiscuousand shared almost the identical core amlno acid residues inthe different strains. Immunization with major determinant peptldeswas recalled vigorously with L. major soluble antigen as wellas with PSP. The response to peptide was almost entirely T_h1as measured by a localized ELISA assay for single-cell productionof IFN-. A similar assay for IL-5, which overcomes problemsof sensitivity and inhibition by lymphoklnes produced by T_h1cells, Indicates very little production of T_h1 cells even byBALB/c. It was found that if a major responsive peak was examinedby recall with overlapping peptldes, the highest, central peptidegave a mainly Th1 response while the boundary, less efficientpeptldes gave more of a T_h2 response. Possible reasons for thiswere discussed. These results point to the importance of selectingthe exactly appropriate peptide in considering a vacclnogenthat might protect susceptible individuals. Even the choiceof a somewhat immunogenlc peptide within the determinant envelopemight actually exacerbate infection by steering the responsein a T_h2 direction.     

Preparing monolayers of non-adherent mammalian cells

A simple method is described for preparing monolayers of non-adherent cells, using concanavalin A to bind the cells to wells of plastic microtest plates. The method was used successfully with all 202 human cell types tested, which included 23 tissue culture lines, 165 fresh specimens of all major histological types of leukemia and lymphoma, 20 fresh myelomas, 2 fresh thymomas, normal spleen and lymph node cells, fractionated T lymphocytes and B lymphocytes from peripheral blood, and cultured fetal amniotic cells. All cell types attached firmly, and were not detached by subsequent vigorous washing. In contrast, attempted attachment of cells in serum free medium, or with poly-L-lysine or glutaraldehyde, was ineffective with many cell types. We used the monolayers as target cells for antibodies to cell surface antigens, utilizing immune rosetting or complement-mediated cytotoxicity. This procedure should simplify most assays involving non-adherent target cells.     

The flexor function of the m. pronator teres in man: a quantitative electromyographic study

Summary The muscle pronator teres was studied by surface electromyography during elbow flexion in a horizontal plane. The forearm was in semi-pronation and movement was performed at various velocities. A quantitative comparison was made between pronator teres activity and two main elbow flexors, biceps brachii and brachioradialis.The mean timing of the onset of activity was constant: biceps brachii was activated first followed by pronator teres and brachioradialis, and the lower the velocity of flexion, the earlier was the onset of biceps brachii activity.There was a linear relationship between the integrated EMG from each muscle and the work done. However, this relationship was less exact for pronator teres and brachioradialis at low values of work, a finding which opens questions about the generality of this relationship and about the muscle equivalent concept.Pronator teres appears to participate in elbow flexion besides its role in pronation.Despite similar anatomical peculiarities, pronator teres does not behave in the same way as anconaeus or popliteus and, above all, it is not the sole muscle active in slow movement. Thus, all the stocky mucles lying close to an articulation do not behave in the same way.     

Effects of spontaneously chosen crank rate variations on electromyographic responses in sub-maximal arm exercise in inexperienced subjects

The aim of the present study was to compare electromyographic responses during arm exercises with a crank rate chosen spontaneously (T_S) or set at 20% below or above (T_–20, T₊₂₀) the spontaneously chosen crank rate (SCCR). Ten male physical education students performed arm exercises with intensities ranging from 20% to 80% of maximal power. Muscular activity levels were analysed for the biceps brachii and the triceps brachii muscles using integrated rectified surface electromyography (iEMG). All values were presented as the mean and standard deviation. During T_S, the sum of iEMG for the two muscles studied was significantly (P<0.05) lower than during T₊₂₀ for each power output. No significant differences were observed in iEMG values between T_S and T_–20. The hypothesis that SCCR relates to a minimisation of muscle activation during an upper body exercise was not confirmed. Variations superior or inferior to a 20% increase of the iEMG responses do not influence it. Moreover, the selection of crank rates depends on the power output and the SCCR increased significantly (P<0.05) with increasing power output.     

Morphologic evaluation of the liver in hereditary angioedema patients on long-term treatment with androgen derivatives

17 alpha-Alkylated androgens are highly effective in preventing attacks in HAE patients. These drugs, however, seem to be implicated in the development of cholestatic jaundice, peliosis hepatis, and liver tumors. In order to assess the risk-benefit balance of the long-term therapy with androgen derivatives, a follow-up investigation was performed in 13 HAE patients. The results of this study indicate that long-term treatment (15 to 47 mo) with low doses of danazol or stanozolol does not induce significant hepatic damage detectable by laboratory tests or liver biopsy. However, the limited number of patients, although in a rather long period of observation, still suggests a careful control and the use of minimal effective doses.     

Methods of detecting mature human Ia-like antigen and their metabolic precursors

Ia antigens were shown to be present in the cell almost exclusively as mature alpha beta dimers which split into separate alpha and beta chains after boiling in SDS. In contrast metabolically labelling the cells with [35S]methionine resulted in only free alpha and beta chains being labelled. It is concluded that this widely used type of labelling, although useful for studying intermediate synthesis, should not be used for labelling mature cell surface molecules.     

Ly49 gene expression in different inbred mouse strains

Mouse natural killer cells express receptors for class IMHC in the form of the Ly49 family of proteins. The Ly49 family contains at least 13 expressed members (A, B, C, D, E, F, G, H, I, J, L, O, and P) and is further subdivided into activating and inhibitory subfamilies based on intracellular and transmembrane characteristics. The level of sequence identity between different members varies dramatically. However, comparison of the extracellular domain has revealed that several of the Ly49 molecules also form “pairs,” where one member is activating and the other is inhibitory. Until recently, most Ly49 molecules described have come from the C57B1/6 strain of inbred mice. Using molecular cloning and immunochemical analysis we have found that different mouse strains express novel Ly49 molecules. Comparison of the allelic forms of some Ly49 molecules has shown that the dividing line between different genes and different alleles is blurred. This project has been funded in whole or in part with federal funds from the National Cancer Institute, National Institutes of Health, under Contract No. NO1-CO-56000. Animal care was provided in accordance with the procedures outlined in A Guide for the Care and Use of Laboratory Animals (National Institutes of Health Publication No. 86-23, 1985). The content of this publication does not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. government.     

Lateral Mobility of the Cell Adhesion Molecule L1 Within the Surface Membrane of Morphologically Undifferentiated and Differentiated Neuroblastoma Cells

Lateral mobility and localization in the surface membrane of the adhesion molecule L1 was studied in morphologically undifferentiated and differentiated neuroblastoma cells to gain insight into its possible association with the different molecular forms of N-CAM. In undifferentiated cells, the fraction of mobile L1 molecules is high and similar to that of N-CAM 140. Upon long-term morphological differentiation, the fraction of mobile L1 molecules is reduced by a factor of three and is similar to that of N-CAM 180, the predominant molecular form of N-CAM in differentiated neuroblastoma cells. Comparable to N-CAM 180, L1 is also preferentially accumulated at contact sites between these cells as seen by indirect immunofluorescence. These observations raise the question of whether at least part of the L1 molecules may be directly or indirectly (e.g. via N-CAM 180) linked to the cytoskeleton, thus stabilizing cell contacts between differentiated cells.