ROFESSIONAL MEDICAL ASSOCIAtions (PMAs), bringing together physicians in the same specialty or subspecialty, make many distinctive contributions to advancing the quality of medical care. In the first instance, PMAs play a vital role in medical education. Their meetings, publications, journals, and continuing medical education (CME) courses inform members of new and established diagnostic and treatment procedures. The PMAs also issue detailed practice guidelines that set the standards for efficient and effective patient care. Moreover, PMAs define ethical norms for their members, promulgating codes of conduct for professional behavior. At the same time, PMAs pursue a public agenda. They advocate for the particular interests of their members, for patients, and for what they believe to be the best interests of society. [1][2][3]
The role of macrophages in protecting mice from murine cytomegalovirus (MCMV) was studied in Swiss, CBA/J, and C57BL/6J mice. CBA/J mice were more resistant to virus than were C57BL/6J mice at all ages tested. Prior treatment of adult Swiss mice with 60 mg of silica, a dose selectively toxic to macrophages, increased mortality due to MCMV infection. Transfer of syngeneic adult macrophages to suckling mice significantly increased their resistance to subsequent MCMV infection. Transfer of syngeneic, nonimmune adult lymphocytes to suckling mice also had a lesser but significant protective effect against subsequent MCMV challenge. In vitro infection of adult CBA/J and C57BL/6J macrophages with virulent and attenuated MCMV resulted in productive infection in only a small percentage of cells and recovery of very little virus from the extracellular fluid. Infection of CBA macrophages was no less productive than C57BL/6J nor was infection with virulent virus more productive than with attenuated virus. Histological examination of the livers of MCMVinfected CBA/J and C57BL/6J mice suggested that divergent cellular immune responses to infection might account for differences in susceptibility. It is postulated that the macrophage may facilitate the inductive phase of cellular immunity, one possible explanation for its demonstrated importance in host defenses against MCMV.
JC virus was found to have a buoyant density of 1.20 g/cm3 in linear sucrose-D2O and 1.35 g/cm3 in cesium chloride isopycnic gradients. DNA extracted either from JC-infected cultures or from gradient-purified virions occupied a dense position relative to linear DNA in cesium chloride/ethidium bromide gradients, and the circular configuration of the extracted DNA was confirmed by electron microscopy, with a measured molecular weight of 2.93 x 106. DNA from BK virus was similarly prepared and compared to JC and to an SV40 DNA standard by digestion with restriction endonuclease preparations from Haemophilus influenzae, Haemophilus parainfluenzae, and Escherichia coli. Digests were electrophoretically analyzed on gradient polyacrylamide slab gels or agarose gels, and the three viruses were found to have distinctly different cleavage patterns by this form of analysis: JC and BK viruses were almost entirely different from SV40 and significantly different from each other. Thus, JC and BK human papovaviruses appear to be discrete new members of the papovavirus group, rather than SV40 variants.
Centrifugation of murine cytomegalovirus inocula from a variety of sources onto secondary mouse embryo cell monolayers at 1,900 × g for 30 min regularly revealed 10- to 100-fold more infectious virus than could be found in the same materials using standard inoculation methods. Virus demonstrable only by centrifugation was present throughout the entire growth cycle in a constant proportion to virus measured without centrifugation. Extracellular growth curves of both populations revealed an 18- to 21-hr latent period, followed by a long-linear increase over the next 12 hr; final yield was 30 plaque-forming units (PFU) per cell. Centrifugation of cells prior to inoculation or after standard adsorption and removal of inoculum failed to result in any significant change in measured virus titer. However, even after 4-hr adsorption, the supernatant inoculum could be transferred and centrifuged onto a fresh monolayer resulting in the same increment of measurable virus. Neutralizing antibody and interferon were equally efficacious against 100 PFU of virus as defined by either method. Thus, this newly identified population of cytomegalo-virus represents the vast majority of potentially infectious units and appears to differ solely in ease of adsorption onto cell monolayers.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.