Discrimination of DNA hybridization using chemical force microscopy.

Atomic force microscopy (AFM) can be used to probe the mechanics of molecular recognition between surfaces. In the application known as "chemical force" microscopy (CFM), a chemically modified AFM tip probes a surface through chemical recognition. When modified with a biological ligand or receptor, the AFM tip can discriminate between its biological binding partner and other molecules on a heterogeneous substrate.

Contact-dependent regulation of N-type calcium channel subunits during synaptogenesis.

The developmental regulation of the N-type calcium channel during synaptogenesis was studied using cultured rat hippocampal neurons to elucidate the roles of extrinsic versus intrinsic cues in the expression and distribution of this channel. Prior to synapse formation, alpha1B and beta3 subunits of the N-type calcium channel were distributed diffusely throughout neurites, growth cones, and somata. As synaptogenesis proceeded, the subunit distributions became punctate and colocalized with the synaptic vesicle protein synaptotagmin.

Membrane deformation of living glial cells using atomic force microscopy.

Using atomic force microscopy (AFM) it has been possible to detect actin filaments that are beneath the cell membrane of living cells despite the fact that the AFM tip is applied to the surface of the cell. To determine whether the AFM tip actually penetrates or deforms the cell membrane we determined whether an intracellularly trapped fluorescent indicator was lost from cells during AFM. Using epifluorescence illumination to monitor the presence of fluo-3 in the cell, we found that AFM did not cause dye leakage from the cell.

Aluminum induces neurite elongation and sprouting in cultured hippocampal neurons.

It has been reported that the aluminum content in the human brain increases with age, and it is particularly high in those with Alzheimer's disease. In this study, we found that a low aluminum concentration (100 mumol/L) in the culture media of opossum hippocampal neurons can induce extensive neurite outgrowth (ie, elongation and branching of neurites) and sprouting (ie, outgrowth of filiform processes from neurite varicosities) within 48 hours. Such changes in neurite morphology were remarkably similar to those described in the aged or Alzheimer's disease brain.

Enhanced neurite growth in cultured neuroblastoma cells exposed to aluminum.

Patients with aluminum-induced encephalopathy syndromes have been shown to have a high level of aluminum concentration in the brain. In the present study, the effects of aluminum were studied in mouse neuroblastoma cells (N-2A) grown in medium supplemented with aluminum (100 microM). It was found that aluminum enhanced neurite growth within 2 days of exposure.

Dietary aluminum selectively decreases MAP-2 in brains of developing and adult rats.

Administration of 0.3% aluminum in drinking water elevated serum aluminum concentrations 8-fold in rats. Further, chronic treatment with aluminum for 2-3 mon, in both developing and adult rats, significantly decreased the levels of MAP-2 in brain, as determined by quantitative immunoblot analysis.