3xTg-AD mice exhibit an activated central stress axis during early-stage pathology.

Activation of the hypothalamic-pituitary-adrenal (HPA) axis occurs in response to the organism's innate need for homeostasis. The glucocorticoids (GCs) that are released into the circulation upon acute activation of the HPA axis perform stress-adaptive functions and provide negative feedback to turn off the HPA axis, but can be detrimental when in excess. Long-term activation of the HPA axis (such as with chronic stress) enhances susceptibility to neuronal dysfunction and death, and increases vulnerability to Alzheimer's disease (AD). However, little is known how components of the HPA axis, upstream of GCs, impact vulnerability to AD. This study examined basal gene expression of stress-related molecules in brains of 3xTg-AD mice during early-stage pathology. Basal GC levels and mRNA expression of the glucocorticoid receptor (GR), mineralocorticoid receptor (MR), and corticotropic releasing hormone (CRH) in several stress- and emotionality-related brain regions were measured in 3-4-month-old 3xTg-AD mice. Despite normal GC levels, young 3xTg-AD mice exhibit an activated central HPA axis, with altered mRNA levels of MR and GR in the hippocampus, GR and CRH in the paraventricular nucleus of the hypothalamus, GR and CRH in the central nucleus of the amygdala, and CRH in the bed nucleus of the stria terminalis. This HPA axis activation is present during early-stage neuropathology when 3xTg-AD mice show mild behavioral changes, suggesting an ongoing neuroendocrine regulation that precedes the onset of severe AD-like pathology and behavioral deficits.

Noise suppression and optical sectioning by non-phase-recording interferometry.

It has long been known that image plane holography with low-coherence illumination achieves optical sectioning of a volume object. A method is analyzed that is similar to image plane holography, but the interferometric arrangement utilizes the interference between two object-bearing beams instead of the basic object and reference beams.

Interaction of poly(amidoamine) dendrimers with supported lipid bilayers and cells: hole formation and the relation to transport.

We have investigated poly(amidoamine) (PAMAM) dendrimer interactions with supported 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid bilayers and KB and Rat2 cell membranes using atomic force microscopy (AFM), enzyme assays, flow cell cytometry, and fluorescence microscopy. Amine-terminated generation 7 (G7) PAMAM dendrimers (10-100 nM) were observed to form holes of 15-40 nm in diameter in aqueous, supported lipid bilayers. G5 amine-terminated dendrimers did not initiate hole formation but expanded holes at existing defects. Acetamide-terminated G5 PAMAM dendrimers did not cause hole formation in this concentration range. The interactions between PAMAM dendrimers and cell membranes were studied in vitro using KB and Rat 2 cell lines. Neither G5 amine- nor acetamide-terminated PAMAM dendrimers were cytotoxic up to a 500 nM concentration. However, the dose dependent release of the cytoplasmic proteins lactate dehydrogenase (LDH) and luciferase (Luc) indicated that the presence of the amine-terminated G5 PAMAM dendrimer decreased the integrity of the cell membrane. In contrast, the presence of acetamide-terminated G5 PAMAM dendrimer had little effect on membrane integrity up to a 500 nM concentration. The induction of permeability caused by the amine-terminated dendrimers was not permanent, and leaking of cytosolic enzymes returned to normal levels upon removal of the dendrimers. The mechanism of how PAMAM dendrimers altered cells was investigated using fluorescence microscopy, LDH and Luc assays, and flow cytometry. This study revealed that (1) a hole formation mechanism is consistent with the observations of dendrimer internalization, (2) cytosolic proteins can diffuse out of the cell via these holes, and (3) dye molecules can be detected diffusing into the cell or out of the cell through the same membrane holes. Diffusion of dendrimers through holes is sufficient to explain the uptake of G5 amine-terminated PAMAM dendrimers into cells and is consistent with the lack of uptake of G5 acetamide-terminated PAMAM dendrimers.