Fully automated measurement of plasma Aß42/40 and p-tau181: Analytical robustness and concordance with cerebrospinal fluid profile along the Alzheimer's disease continuum in two independent cohorts.

INTRODUCTION: For routine clinical implementation of Alzheimer's disease (AD) plasma biomarkers, fully automated random-access platforms are crucial to ensure reproducible measurements. We aimed to perform an analytical validation and to establish cutoffs for AD plasma biomarkers measured with Lumipulse. METHODS: Two cohorts were included. UNIPG: n = 450 paired cerebrospinal fluid (CSF)/plasma samples from subjects along the AD-continuum, subjects affected by other neurodegenerative diseases, and controls with known CSF profile; AMS: n = 40 plasma samples from AD and n = 40 controls. Plasma amyloid ß (Aß)42, Aß40, and p-tau181 were measured with Lumipulse. We evaluated analytical and diagnostic performance. RESULTS: Lumipulse assays showed high analytical performance. Plasma p-tau181 levels accurately reflected CSF A+/T+ profile in AD-dementia and mild cognitive impairment (MCI)-AD, but not in asymptomatic-AD. Plasma and CSF Aß42/40 values were concordant across clinical AD stages. Cutoffs and probability-based models performed satisfactorily in both cohorts. DISCUSSION: The identified cutoffs and probability-based models represent a significant step toward plasma AD molecular diagnosis.

1-Methyl-4-thiohistidine and Glutathione in the Developing Embryo of the Sea Urchin, Paracentrotus lividus.: (1-methyl-4-thiohistidine/glutathione/sea urchin embryo).

4-thiohistidines occur as free amino acids in the eggs of several marine organisms, in particulary relevant concentrations in the eggs of echinoderms. Since nothing is known about their biological role or biosynthesis and metabolic fate, we measured the concentration of 1-methyl-4-thiohistidine together with the two most common small molecular weight thiols, glutathione and cysteine, during embryonic development of the sea urchin Paracentrotus lividus until the pluteus stage. The thiols were determined by high performance liquid chromatography as fluorescent derivatives of monobromobimanes. 1-methyl-4-thiohistidine and glutathione are present until the pluteus stage with an approximate ratio of 2: 1. Cysteine was detected at the blastula stage and found to increase thereafter. 1-methyl-4-thiohistidine was absent, or present in traces, in sperm and in somatic tissues of adults. It is concluded that 1-methyl-4-thiohistidine is typical of eggs and embryos and may be metabolized during metamorphosis into an as yet unknown compound.

AMPA/kainate and NMDA-like glutamate receptors at the chromatophore neuromuscular junction of the squid: role in synaptic transmission and skin patterning.

Glutamate receptor types were examined at the chromatophore synapses of the squids Alloteuthis subulata and Loligo vulgaris, where nerve-induced muscle contraction causes chromatophore expansion. Immunoblotting with antibody raised against a squid AMPA receptor (sGluR) demonstrated that AMPA/kainate receptors are present in squid skin. Application of l-glutamate evoked chromatophore muscle contractions in both ventral and dorsal skins, while NMDA was only active on a subpopulation of dorsal chromatophores. In dorsal skin, neurotransmission was partly blocked by either AMPA/kainate receptor antagonists (CNQX and DNQX) or NMDA receptor antagonists (AP-5 and MK-801) or completely blocked by simultaneous application of both classes of antagonists. In isolated muscle fibres, ionophoretic application of l-glutamate evoked fast inward CNQX- and DNQX-sensitive currents with reversal potentials around +14 mV and a high conductance to Na+. In fibres from dorsal skin only, a slower outward glutamate-sensitive current appeared at positive holding potentials. At negative potentials, currents were potentiated by glycine or by removing external Mg2+ and were blocked by AP-5 and MK-801. Glutamate caused a fast, followed by a slow, transient increase in cytoplasmic Ca2+. The slow component was increased in amplitude and duration by glycine or by lowering external Mg2+ and decreased by AP-5 and MK-801. In cells from ventral skin, no 'NMDA-like responses' were detected. Thus, while AMPA/kainate receptors mediated fast excitatory synaptic transmission and rapid colour change over the whole skin, activation of both AMPA/kainate and NMDA-like receptors in a subpopulation of dorsal chromatophores prolonged the postsynaptically evoked Ca2+ elevation causing temporally extended colour displays with behavioural significance.