A beta, aging, and Alzheimer's disease: a tale, models, and hypotheses

In this paper we explore the potential functional role of the A beta peptides in the context of Alzheimer's disease (AD). We begin by defining the morphology of the amyloid deposits in relation to surrounding glial cells and, more importantly, in relation to the brain vasculature. Amyloid accumulation in the brain's microvasculature causes disturbances in the blood-brain barrier (BBB), and in larger arteries, impairment in control of regional cerebral blood flow due to myocyte degeneration. We postulate that the deposition of vascular amyloid may represent a hydrophobic protein plaster to seal leaks in the BBB, occasionally observed in aging and catastrophically common in AD. The vasoconstrictive activity of A beta may also be related to leaky vessels whereby decreasing the arterial diameter may also help to control breaches in the BBB. The admission of plasma neurotoxic proteins into the brain may be controlled by activation of microglia elicited by soluble A beta peptides creating a subtle, but permanent brain inflammatory reaction. We also delve into the influence that cholesterol metabolism may have in membrane topology and A beta production, and the close correlations that exist between cardiovascular disease and AD. Finally, we speculate about the possibility of a peripheral source of A beta that may, by crossing the BBB, contribute to the vascular and parenchymal deposits of A beta in the AD brain.     

Perinatal stimulation and adaptation of the neonate

The present report describes psychobiological studies of behavior around the time of birth. An adaptive, ecological perspective is presented in which stimulation of the fetus and newborn is purported to instigate adaptive postpartum behavior. Studies describing the perinatal sensory environment are reviewed, with a consideration of emergent sensory function of the fetus. It is asserted that afferent input associated with parturition perturbs the fetus and neonate, producing a general arousal state that facilitates breathing, suckling, and early learning. The view developed herein is that perinatal sensory input induces and canalizes the newborn's behavior, thereby regulating adaptive postpartum function. Deviations in afferent input may alter ontogenetic trajectories and compromise developmental outcome by reducing availability of conditions necessary for adequate postpartum adaptation.     

Prekallikrein-Kallikrein conversion rate as a predictor of contrast material catastrophies

An in vitro is described that attempts to detect patients with a potential for adverse systemic reactions to contrast material. This test involves measuring the rate of conversion of prekallikrein to kallikrein under certain standard conditions. In a preliminary retrospective study, the test could be used to identify such patients with a sensitivity of 88%, a specificity of 82%, and a predictive value of 79%.