Methods in Cell Science

Adipose tissue offers an abundant source for isolation of microvascular endothelial cells (MVECs). Several cell types result from the enzymatic digestion of adipose tissue, including MVECs, mesothelial cells and fibroblasts. Pure populations of MVECs must be isolated from the mixed cultures or fibroblasts overgrow the population. Canine subcutaneous or mesenteric fat is obtained during elective surgical procedures and digested with collagenase. Microvascular endothelial cells are separated from capillary fragments by Percoll gradient centrifugation and plated in culture. At confluence, microscopic identification of most cultured cells indicate the typical cobblestone morphology of ECs, while other spindle shaped cells resemble fibroblasts. Micro- vascular endothelial cells are identified by their uptake of acetylated-low density lipoprotein (Ac-LDL). Mesothelial cells, which closely resemble MVECs in morphology, and fibroblasts are removed from cultures of MVECs using a fluorescent activated cell sorter (FACS). Acetylated-low density lipoprotein tagged with a fluorescent probe, 1,1′-dioctadecyl-3,3,3′,3′-tetramethyl- indocarbocyanine perchlorate (DiI), is incubated with the mixed cultures and the cells are sorted using a FACS. The pure populations of MVECs that result are tested immunocytochemically and are identified by their positive staining with antibodies against factor VIII related antigen. Mesothelial cells are identified by positive staining for cytokeratin 18 antibody. Contaminating fibroblasts show negative staining for smooth muscle alpha actin, cytokeratin 18 and factor VIII related antigen antibodies. This study examines the efficiency of the fluorescent activated cell sorter to obtain pure populations of MVECs harvested from adipose tissue.

A method is described that facilitates performing a large number of protoplast fusions to mammalian cells simultaneously and successfully. This method makes it possible to circumvent typical hurdles to the use of transient expression in mammalian cells, facilitating expression cloning of DNA enoding the newly detected gene product of interest. The original in vitro assay used to define the new activity is of interest, adapted to microtiter plates, combined with protoplast fusion, extends the reach of expression cloning to such cases as products of a rare message, or activities involving a multisubunit or unstable protein or both.

The rat model of endocarditis is a well established experimental protocol which closely approximates human native valve endocarditis. The rat model of endocarditis has been used to examine the role of particular streptococcal virulence factors, to assess immunoprotective strategies, and to evaluate the efficacy of selected antibiotic treatment regimens for streptococcal endocarditis. Like humans, rats are generally susceptible to endocarditis only if the cardiac valves have been damaged. In the rat model of endocarditis, damage to the aortic valve and sterile vegetation formation is accomplished by insertion of a polyethylene catheter through the carotid artery into the left ventricle. Following catheter insertion, an inoculum of streptococci are injected intravenously. Vegetations removed from the heart valves during thoracotomy of euthanized animals are qualitatively cultured for streptococcal infection. The method, including investigator safety considerations, is described in detail.

Methods were developed to measure albumin permeability and electrical resistance of bovine aortic endothelial cell (BAEC) monolayers cultured on porous polycarbonate filters. Permeability to 1% bovine serum albumin (Pe) was quantified by measuring the flux of fluorescent-labeled albumin with an apparatus in which there were no transmural oncotic or hydrostatic pressure gradients. The effect of passage of BAEC monolayers in culture on permeability was studied using 60 BAEC monolayers of Passage 6 to 10. There was no significant difference in Pe between passages, and the mean Pe of all monolayers was 4.5 ± 0.5 (SEM) × 10−6 cm/s. Using these same BAEC monolayers, a fluorescent technique was developed to examine en face permeability patterns. Most BAEC monolayers demonstrated diffuse permeability across the monolayer, whereas others had focal regions of enhanced permeability despite similar Pe values. In those monolayers with punctate permeability, there were 5.4 ± 0.6 (SEM) focal regions of enhanced permeability per 1000 cells. To study the effect of culture time on monolayer integrity, electrical conductivities of nine BAEC monolayers were measured daily using a Millipore electrical resistance system. Electrical resistance increased from 4.5 ohm·cm2 at Day 2 to a peak level of 11.4 ohm·cm2 at Day 7 and then decreased daily to 4.0 ohm·cm2 by Day 12. The in vitro BAEC monolayer has many of the transport characteristics of intact vessels, making these techniques useful in physiologic studies of the endothelial transport barrier. These methods provide relatively simple means of assessing the integrity of endothelial cell monolayers grown on porous substrates.

A method is described wherebyP. berghei sprorozoites may be obtained from the salivary glands of infected femaleA. stephensi mosquitoes. The method is relatively easy to master, requires minimal handling of biological material, and is done with ordinary laboratory equipment. In addition, the sporozoites are rendered relatively free of contaminating micro-organisms and the entire operation may be performed aseptically.

Convenient and reproducible culture systems for murine megakaryocyte progenitor cells (colony-forming unit-megakaryocytes, CFU-Meg) are described. Mouse bone marrow cells are cultured in fibrin clots supplemented with Iscove's modified Dulbecco's medium and fetal bovine serum or in fibrin clots supplemented with serum-free IMDM, bovine serum albumin, transferrin, cholesterol, and L-α-phosphatidylcholine. In the presence of murine interleukin-3 or pokeweed mitogen-stimulated murine spleen cell-conditioned medium, these cultures support CFU-Meg colony formation effectively. The cultivation and counting of colonies in these culture systems is considerably easier when compared with previously reported culture systems.