Basal forebrain cholinergic cell attachment and neurite outgrowth on organotypic slice cultures of hippocampal formation.

Distributions of somata and neurites of cholinergic neurons were studied after seeding dissociated cells onto organotypic slice cultures. Slice cultures were made from hippocampal formation and adjacent cortical regions from rats or mice. Dissociated cell suspensions of basal forebrain tissue from rat or mouse fetuses were seeded onto the slice cultures. Combined cultures were maintained for 1-21 days in vitro. Cultures processed for acetylcholinesterase (AChE) histochemistry demonstrated non-random patterns of cholinergic cells and their neurites. Labeled cells appeared most frequently in the molecular layer of the dentate gyrus, and in the deeper layers of cortical regions adjacent to the hippocampus. Neurites extending from these labeled cells appeared to target the dentate molecular layer and the cortical subplate layer. By 4 days in vitro, AChE-positive basal forebrain cells display several short and thick neurites that appear to be dendrites, and one long process that appears to be an axon. By 5 days in vitro, dendrites are well developed; by 7 days the presumed axon has extended widely over the cortical target zone. These neurites are maintained through 3 weeks in culture. Distributions of cells varied with the age of the slice. AChE-labeled cells were not seen overlying hippocampal tissue when dissociated cells were seeded on slice cultures made from day 0 rats, but a few labeled cells were seen when seeded on slices from day 2 rats. Clear non-random patterns of labeled cells and neurite outgrowth were seen on slice cultures from day 5 or older pups. The non-random distribution seen with AChE-positive neurons was not seen using other techniques that labeled all cells (non-selective fluorescent labels) or all neurons; these techniques resulted in labeled cells scattered apparently homogenously across the slice culture.These studies demonstrate a non-random pattern of attachment or differentiation of basal forebrain cholinergic neurons when these cells are seeded onto cultured cortical slices; this pattern mimics the normal patterns of basal forebrain cholinergic projections to these cortical regions. These data suggest that the factors that normally guide basal forebrain-derived cholinergic axons to their target cells in vivo are present and detectable in this model system.

A five-year evaluation of implants placed in extraction sockets.

The aim of this study is to examine extraction socket implant longevity and peri-implant conditions longitudinally and to compare the outcome with implants placed in intact alveolar bone sites (nonextraction sites) after a time period in function of five years or more. We hypothesize that implants placed into fresh extraction sockets have a long-term rate of success similar to that of conventionally placed implants. Eleven extraction socket implants in eight patients with a follow-up of at least five years were included in this report. The implants were loaded with either single-tooth replacements or three-to-four-unit fixed partial dentures after healing times of four to six months. Intraoral radiographs of the 11 implants were obtained immediately after surgery and upon recall five to seven years after surgery. In addition, the following clinical parameters were evaluated at each implant site five to seven years postsurgery: plaque indices (PT), bleeding indices (BI), probing depths, attachment level (AL), and distance from implant shoulder to mucosal margin (DIM). As a control, 11 implants from a previous long-term study of nonsubmerged implants placed into intact alveolar bone sites by the same clinician were matched by implant location, sex, and age. Initial and long-term follow-up radiographs of the experimental and control groups were scanned into a computer. A computer program designed for radiographic implant analysis was utilized to examine the changes in radiographic bone levels over time in the two groups. After a period of five to seven years, the mean bone loss for the immediate implant group was 0.167 mm, while that of the control group was 0.460 mm. An unpaired t-test resulted in a P value = 0.0563, indicating that the mean change in bone levels between the two groups is not statistically significant. In addition, clinical evaluation parameters (PI, BI, AL, DIM) revealed no significant difference between the two groups. Therefore, it can be stated that in this study the long-term success rate for extraction socket implants is similar to that of conventionally placed implants.