Studies on the mechanism of phagocytosis. I. Requirements for circumferential attachment of particle-bound ligands to specific receptors on the macrophage plasma membrane

These experiments were designed to evaluate the role of macrophage plasma membrane receptors for the third component of complement (C) and for the Fc portion of IgG in the ingestion phase of phagocytosis. Sheep erythrocyte (E) were coated with anti-E IgG [E(IgG)]; these E(IgG) were then attached to cultivated monolayers of mouse peritoneal macrophages under conditions which reversibly inhibit ingestion of E(IgG). The E(IgG)-macrophage complexes were further incubated under similar conditions with an antimacrophage IgG fraction which blocks Fc receptor-mediated ingestion but has no effect upon ingestion mediated by other phagocytic receptors. When these cultures were subsequently incubated under conditions optimal for particle ingestion, phagocytosis of the IgG-coated erythrocytes did not occur; the erythrocytes remained bound to the Fc receptors of the macrophage plasma membrane. To determine whether ligands must cover the entire surface of an attached particle to permit ingestion of that particle, C-coated E [E(IgM)C] were bound to the C receptors of thioglycollate-induced (activated) macrophages at 4 degrees C. E(IgM)C-macrophage complexes were then trypsinized at 4 degrees C, a procedure which resulted in cleavage of erythrocyte-bound C3b molecules to a form of C3 not recognized by the macrophage receptors for C3b. Under the conditions used, trypsin did not affect the attachment of E(IgM)C to the macrophage surface or the macrophage receptors for C3b. When these trypsin treated E(IgM)C-macrophage complexes were incubated at 37 degrees C, the bound E(IgM)C were not ingested; the erythrocytes remained attached to the macrophage plasma membrane via the macrophage's C receptors. These results indicate that attachment of a particle to specific receptors on the macrophage plasma membrane is not sufficient to trigger ingestion of that particle. Rather, ingestion requires the sequential, circumferential interaction of particle-bound ligands with specific plasma membrane receptors not involved in the initial attachment process

Turnover, COVID-19, and Reasons for Leaving and Staying Within Governmental Public Health

Background and Objectives: Public health workforce recruitment and retention continue to challenge public health agencies. This study aims to describe the trends in intention to leave and retire and analyze factors associated with intentions to leave and intentions to stay. Design: Using national-level data from the 2017 and 2021 Public Health Workforce Interests and Needs Surveys, bivariate analyses of intent to leave were conducted using a Rao-Scott adjusted chi-square and multivariate analysis using logistic regression models. Results: In 2021, 20% of employees planned to retire and 30% were considering leaving. In contrast, 23% of employees planned to retire and 28% considered leaving in 2017. The factors associated with intentions to leave included job dissatisfaction, with adjusted odds ratio (AOR) of 3.8 (95% CI, 3.52-4.22) for individuals who were very dissatisfied or dissatisfied. Odds of intending to leave were significantly high for employees with pay dissatisfaction (AOR = 1.83; 95% CI, 1.59-2.11), those younger than 36 years (AOR = 1.58; 95% CI, 1.44-1.73) or 65+ years of age (AOR = 2.80; 95% CI, 2.36-3.33), those with a graduate degree (AOR = 1.14; 95% CI, 1.03-1.26), those hired for COVID-19 response (AOR = 1.74; 95% CI, 1.49-2.03), and for the BIPOC (Black, Indigenous, and people of color) (vs White) staff (AOR = 1.07; 95% CI, 1.01-1.15). The leading reasons for employees\u27 intention to stay included benefits such as retirement, job stability, flexibility (eg, flex hours/telework), and satisfaction with one\u27s supervisor. Conclusions: Given the cost of employee recruitment, training, and retention of competent employees, government public health agencies need to address factors such as job satisfaction, job skill development, and other predictors of employee retention and turnover. Implications: Public health agencies may consider activities for improving retention by prioritizing improvements in the work environment, job and pay satisfaction, and understanding the needs of subgroups of employees such as those in younger and older age groups, those with cultural differences, and those with skills that are highly sought-after by other industries

A scanning electron microscopic study of hypercementosis

The purpose of this study was to evaluate morphological characteristics of teeth with hypercementosis that are relevant to endodontic practice. Twenty-eight extracted teeth with hypercementosis had their root apexes analyzed by scanning electron microscopy (SEM). The teeth were divided according to tooth groups and type of hypercementosis. The following aspects were examined under SEM: the contour and regularity of the root surface; presence of resorption; presence and number of apical foramina, and the diameter of the main foramen. The progression of club shape hypercementosis was directly associated with the presence of foramina and apical foramen obstruction. Cases of focal hypercementosis presented foramina on the surface, even when sidelong located in the root. Circular cementum hyperplasia form was present in 2 out of 3 residual roots, which was the highest proportion among the tooth types. The detection of a large number of foramina in the apical third of teeth with hypercementosis or even the possible existence of apical foramen obliteration contributes to understand the difficulties faced during endodontic treatment of these cases

F.J. Turner’s ‘frontier thesis’: the ruse of American ‘character'

American society was transformed by the expansion of capital Westward and the explosion in opportunities that ensued for land grabbing and agricultural and industrial investment. In Turner’s (1961) frontier thesis this was portrayed as resulting in the emergence of ‘the new man’ i.e. the fulfilment of American character. The frontier thesis is a neo-Darwinian contribution. It posits exceptionalism and transcendence as the keys to American character. The gene pool of the Americans, thriving in a new geographical and social environment, is depicted as achieving a higher level of development than the stratified societies of Old Europe. What the thesis ignores is the importance of orthodox Eurocentric strategies of colonization and land appropriation. Turner portrays pioneer/settler society as a heroic departure, but in many ways, it is a continuation of European precedents. Analogously, the proposition that the push West crystallized American character obscures the role of personality, especially in urban-industrial settings, in establishing the parameters of American life. Turner conceived of character as emerging from a struggle with the spatial frontier. But the struggles of personality with the social frontier of repression and establishment values is no less significant. The paper examines the tensions between character and personality by using some ideas developed by Carl Schmitt on the significance of ‘the opportunity’ in competitive advantage. The importance of the opportunity and personality in developing the American way of life are examined by the vaudeville and celebrity traditions. The exploitation of contingency for personal advantage, the use of melodrama to engineer social impact, the social validation of forthright behaviour are examined in the context of the careers of the film actress Mae West and the comedian Bob Hope

Human Nail Plate Modifications Induced by Onychomycosis : Implications for Topical Therapy

Open Access - This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are creditedConclusions: Onchomycotic nails presented a thicker but more porous barrier, and its eroded intracellular matrix rendered the tissue more permeable to topically applied chemicals when an aqueous vehicle was used.Purpose: Through the characterisation of the human onchomycotic nail plate this study aimed to inform the design of new topical ungual formulations.Methods: The mechanical properties of the human nail were characterised using a Lloyd tensile strength tester. The nail’s density was determined via pycnometry and the nail’s ultrastructure by electron microscopy. Raman spectroscopy analysed the keratin disulphide bonds within the nail and its permeability properties were assessed by quantifying water and rhodamine uptake.Results: Chronic in vivo nail plate infection increased human nailplate thickness (healthy 0.49 ± 0.15 mm; diseased 1.20 ± 0.67 mm), but reduced its tensile strength (healthy 63.7 ± 13.4 MPa; diseased 41.7 ± 5.0 MPa) and density (healthy 1.34 ± 0.01 g/cm3; diseased 1.29 ± 0.00 g/cm3). Onchomycosis caused cell-cell separation, without disrupting the nail disulfide bonds or desmosomes. The diseased and healthy nails showed equivalent water uptake profiles, but the rhodamine penetration was 4-fold higher in the diseased nails using a PBS vehicle and 3 -fold higher in an ethanol/PBS vehicle.Peer reviewe