Isolation of fusobacteria from the oral cavities of malnourished Nigerian children living in agricultural and herding villages.

A previous study demonstrated the presence and possible involvement of Fusobacterium necrophorum in the pathogenesis of noma lesions of children living in agricultural and herding villages in northwestern Nigeria. In order to determine if F. necrophorum was part of the oral flora of malnourished children with no noma lesions, a study of the fusobacteria present in the oral cavities of 30 children, 2-6 years of age in Sokoto State, was undertaken. Swabs taken of the oral cavity were cultured on selective fusobacteria medium using conventional anaerobic microbiological techniques. F. nucleatum was recovered from each child and F. necrophorum was isolated from the oral cavity of only one child. The presence of F. nucleatum and the lack of F. necrophorum, except in one case, suggests that the latter is not normal flora in the children at risk for noma. F. necrophorum, a putative trigger organism for noma may gain a foothold only when certain staging conditions (i.e., lowered host resistance and/or oral lesion) are present.

The separation of harvested cells from microcarriers: a comparison of methods.

Two techniques are described which have been designed to separate harvested cells from microcarriers. The requirements of efficient recovery and high viability of the cells are met by both procedures. Differences both in size and density between cells and microcarriers allow separations which are based on differential centrifugation or filtration. After trypsinizing the cells from the microcarriers, separation was performed by either ; a) low-speed centrifugation on Ficoll-Paque or, b) filtration through nylon meshes. The methodologies for both techniques are presented. Up to 78% of the total cells were recovered by discontinuous gradient centrifugation using Ficoll-Paque. similar results were obtained when separating Vero, BS-C-1 and MRC-5 cells from Cytodex 1, Cytodex 2 and Cytodex 3 microcarriers. Equally high recoveries were obtained by filtration through an 88 micron pore size nylon mesh. Data are presented for the separation of both Vero and HeLa cells from all 3 types of microcarriers after filtration through 53 and/or 88 micron meshes. Greater than 92% viability of the recovered cells was consistently obtained and their growth properties upon subsequent reculturing were unaffected by either separation procedure. Differential sedimentation by unit gravity provides adequate cell recovery for many applications, but yields are significantly increased by using one or other of the methods described here. Both techniques are rapid and efficient. In addition, differential centrifugation provides a concentrated suspension of the recovered cells, while the nylon meshes for filtration are reusable and can be autoclaved at least 5 times.(ABSTRACT TRUNCATED AT 250 WORDS)

Retention of susceptibility to mitogens after direct dansylation of viable human lymphocytes.

The covalently binding fluorescent probe 5-dimethylamino-1-naphthalenesulfonyl (dansyl) chloride was affixed directly to the plasma membrane of viable human peripheral blood lymphocytes via a solid phase transfer method utilizing Sephadex G-10 as the transfer vehicle. After dansylation, lymphocytes retain maximal short-term viability. Dansyl, as the protein conjugate or as the free acid, does not appear to penetrate the cells to any significant extent. Dansylated mixed lymphocyte cultures respond to lectin mitogen stimulation for at least 72 hr. Furthermore, differential response of dansylated lymphocytes in culture to three plant lectin mitogens provides a clue to the binding loci of concanavalin A with respect to phytohemagglutinin and pokeweed mitogen on the lymphocyte surface receptors for these lectins. The ability to sustain functionally responsive dansylated lymphocytes for several days in culture suggest that such probe-tagged cells may be useful in elucidating aspects of the plasma membrane in the regulation of cell behavior.