The effect of collisions on the rotational angular momentum of diatomic molecules studied using polarized light.

We report results of an experimental study of the changes in the alignment of the rotational angular momentum of diatomic molecules during elastic collisions. The experiment involved collisions of diatomic lithium molecules in the A1Σu + excited electronic state with noble gas atoms (helium and argon) in a thermal gas phase sample. Polarized light for excitation was combined with the detection of polarization-specific fluorescence in order to achieve magnetic sublevel state selectivity. We also report results for rotationally inelastic collisions of Li2 in the lowest lying rotational levels of the A1Σu +v=5 vibrational state with noble gas atoms.

Decreased alpha-secretase-cleaved amyloid precursor protein as a diagnostic marker for Alzheimer's disease.

The neuropathologic hallmarks of Alzheimer's disease (AD) are extracellular plaques and intracellular neurofibrillary tangles. A constituent of senile plaques in AD is beta-amyloid, a hydrophobic peptide of 39-43 amino acids and a fragment of the amyloid precursor protein (APP). APP can be metabolized by at least two pathways, one of which involves generation of soluble APP by an unidentified enzyme named alpha-secretase. This cleavage generates alpha-secretase-cleaved, soluble APP (alpha-sAPP), which in this investigation was measured by a new assay in cerebrospinal fluid (CSF) from members of a Swedish AD family with a pathogenic mutation at APP670/671 (ref. 2). Family members who carry the mutation and are diagnosed with AD had low levels of alpha-sAPP (160 +/- 48 ng ml-1), with no overlap compared with non-carriers (257 +/- 48 ng ml-1). Carriers of the presymptomatic mutation showed intermediate alpha-sAPP levels. Today there exists no antemortem marker in AD with sufficient sensitivity and specificity, but measurement of alpha-sAPP represents a new and promising diagnostic marker.

Cerebrospinal fluid levels of alpha-secretase-cleaved soluble amyloid precursor protein mirror cognition in a Swedish family with Alzheimer disease and a gene mutation.

OBJECTIVE: To explore the relationship between possible biological markers of Alzheimer disease that are related to amyloid metabolism and mental functions. PARTICIPANTS: Twelve individuals from a Swedish family with Alzheimer disease and a double mutation at codons 670/671 of the amyloid precursor protein gene participated in the study. DESIGN: Cerebrospinal fluid levels of alpha-secretase cleaved soluble amyloid precursor protein (alpha-sAPP), total sAPP, and amyloid beta-peptide were correlated with data on multiple cognitive functions that covered the whole range of human performance. SETTING: The Alzheimer's Disease Research Centre, Department of Clinical Neuroscience, Section of Geriatric Medicine, Karolinska Institute, Huddinge University Hospital, Huddinge, Sweden. RESULTS: There were highly significant linear correlations between low levels of alpha-sAPP and poor performance on neuropsychological tests that assessed intelligence, verbal and visuospatial functions, memory, and attention. Within the group of nonmutation carriers, significant correlations were also obtained between the levels of alpha-sAPP and cognitive functions. A less striking association was seen between the levels of total sAPP and cognition. No association was found between the levels of amyloid beta-peptide and cognition. CONCLUSIONS: The strong relationship between alpha-sAPP levels and cognition in both patients with Alzheimer disease and normal-aging persons may imply that alpha-sAPP is involved in basic protective brain processes. Alternatively, less amyloid beta-peptide amounts are produced, leading to diminished plaque formation, when alpha-sAPP is generated.