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Photoionization can initiate structural reorganization of molecular matter and drive formation of new chemical bonds. Here, we used time-resolved extreme ultraviolet (EUV) pump - EUV probe Coulomb explosion imaging of carbon dioxide dimer ion C O 2 2 + dynamics, that combined with ab initio molecular dynamics simulations, revealed unexpected asymmetric structural rearrangement. We show that ionization by the pump pulse induces rearrangement from the slipped-parallel (C 2h ) geometry of the neutral C O 2 dimer towards a T-shaped (C 2v ) structure on the ~100 fs timescale, although the most stable slipped-parallel (C 2h ) structure of the ionic dimer. Moreover, we find that excited states of the ionized C O 2 dimer can exhibit formation of a CO 3 moiety in the C 2 O 4 + complex that can persist even after a suitably time-delayed second photoionization in a metastable C 2 O 4 2 + dication. Our results suggest that charge asymmetry plays an important role in the ionization-induced dynamics in such dimers that are present in C O 2 rich environments., (© 2024. The Author(s).)

Two- and three-body Coulomb explosion dynamics of isolated ethanol dications are studied via single-photon double-ionization with ultrafast extreme-ultraviolet pulses. The measured 3-body momentum correlations obtained via 3D coincidence imaging of the ionic products provide evidence for several concerted and sequential mechanisms: (1) a concerted 3-body breakup mechanism, with dominating channels such as CH 3 + + COH + + H 2 ; (2) sequential dissociation in which the ejection of a low-kinetic-energy neutral OH precedes the Coulomb explosion of C 2 H 5 2+ → CH 3 + + CH 2 + ; and (3) a sequential 3-body breakup mechanism that dominates H 3 + formation from the ethanol dication via a mechanism that is different from the well-studied H 3 + formation in the 2-body Coulomb explosion of the methanol dication. Furthermore, we report surprising branching ratios of the competing C-O bond dissociation channels, resulting in H 3 O + , H 2 O + and OH + formation.

Electron-transfer reactions are ubiquitous in chemistry and biology. The electrons' quantum nature allows their transfer across long distances. For example, in the well-known harpoon mechanism, electron transfer results in Coulombic attraction between initially neutral reactants, leading to a marked increase in the reaction rate. Here, we present a different mechanism in which electron transfer from a neutral reactant to a multiply charged cation results in strong repulsion that encodes the electron-transfer distance in the kinetic energy release. Three-dimensional coincidence imaging allows to identify such "inverse" harpoon products, predicted by nonadiabatic molecular dynamics simulations to occur between H 2 and HCOH 2+ following double ionization of isolated methanol molecules. These dynamics are experimentally initiated by single-photon double ionization with ultrafast extreme ultraviolet pulses, produced by high-order harmonic generation. A detailed comparison of measured and simulated data indicates that while the relative probability of long-range electron-transfer events is correctly predicted, theory overestimates the electron-transfer distance.

We study the competing mechanisms involved in the Coulomb explosion of 2-propanol CH 3 2 CHOH 2+ dication, formed by an ultrafast extreme ultraviolet pulse. Over 20 product channels are identified and characterized using 3D coincidence imaging of the ionic fragments. The momentum correlations in the three-body fragmentation channels provide evidence for a dominant sequential mechanism, starting with the cleavage of a C-C bond, ejecting CH 3 + and CH 3 CHOH + cations, followed by a secondary fragmentation of the hydroxyethyl cation that can be delayed for up to a microsecond after ionization. The C-O bond dissociation channels are less frequent, involving proton transfer and double proton transfer, forming H 2 O + and H 3 O + products, respectively, and exhibiting mixed sequential and concerted character. These results can be explained by the high potential barrier for the C-O bond dissociation seen in our ab initio quantum chemical calculations. We also observe coincident COH + + C 2 H n + ions, suggesting exotic structural rearrangements, starting from the Frank-Condon geometry of the neutral 2-propanol system. Remarkably, the relative yield of the H 3 + product is suppressed compared with methanol and alkene dications. Ab initio potentials and ground state molecular dynamics simulations show that a rapid and direct C-C bond cleavage dominates the Coulomb explosion process, leaving no time for H 2 roaming, which is a necessary precursor to the H 3 + formation.

CO 2 single-photon double photoionization, Coulomb explosion, and dissociative ionization are studied with ultrafast extreme-ultraviolet pump and time-delayed near-infrared probe pulses. Kinetic energy release and momentum correlations for the two-body CO + + O + and three-body O + + C + + O fragmentation products are determined by 3D coincidence fragment imaging. The transient enhancement of the ratio of two-body vs three-body Coulomb explosion events and the time dependence of low and high kinetic energy release dissociation events are discussed in terms of dissociative ionization and Coulomb explosion dynamics.

Despite the abundance of data concerning single-photon double ionization of methanol, the spin state of the emitted electron pair has never been determined. Here we present the first evidence that identifies the emitted electron pair spin as overwhelmingly singlet when the dication forms in low-energy configurations. The experimental data show that while the yield of the CH 2 O + + H 3 + Coulomb explosion channel is abundant, the metastable methanol dication is largely absent. According to high-level ab initio simulations, these facts indicate that photoionization promptly forms singlet dication states, where they quickly decompose through various channels, with significant H 3 + yields on the low-lying states. In contrast, if we assume that the initial dication is formed in one of the low-lying triplet states, the ab initio simulations exhibit a metastable dication, contradicting the experimental findings. Comparing the average simulated branching ratios with the experimental data suggests a >3 order of magnitude enhancement of the singlet:triplet ratio compared with their respective 1:3 multiplicities.

High-resolution infrared spectra of the symmetric top isobutane CH(CH 3 ) 3 were assigned with the help of ab initio calculations. The strong parallel band ν 5 (a 1 ) with an origin at 1396.54741(76) cm -1 and the ν 4 (a 1 ) mode, the CH 2 scissors, at 1478.20363(41) cm -1 were rotationally analyzed. The bands in the C-H stretching region were assigned with the help of an anharmonic calculation and a local mode analysis.

The rotational spectra of H 3 N⋯AgI and H 2 O⋯AgI have been recorded between 6.5 and 18.5 GHz by chirped-pulse Fourier-transform microwave spectroscopy. The complexes were generated through laser vaporisation of a solid target of silver or silver iodide in the presence of an argon gas pulse containing a low concentration of the Lewis base. The gaseous sample subsequently undergoes supersonic expansion which results in cooling of rotational and vibrational motions such that weakly bound complexes can form within the expanding gas jet. Spectroscopic parameters have been determined for eight isotopologues of H 3 N⋯AgI and six isotopologues of H 2 O⋯AgI. Rotational constants, B 0 ; centrifugal distortion constants, D J , D JK or Δ J , Δ JK ; and the nuclear quadrupole coupling constants, χ aa (I) and χ bb (I) - χ cc (I) are reported. H 3 N⋯AgI is shown to adopt a geometry that has C 3v symmetry. The geometry of H 2 O⋯AgI is C s at equilibrium but with a low barrier to inversion such that the vibrational wavefunction for the v = 0 state has C 2v symmetry. Trends in the nuclear quadrupole coupling constant of the iodine nucleus, χ aa (I), of L⋯AgI complexes are examined, where L is varied across the series (L = Ar, H 3 N, H 2 O, H 2 S, H 3 P, or CO). The results of experiments are reported alongside those of ab initio calculations at the CCSD(T)(F12*)/AVXZ level (X = T, Q).

The current knowledge about neuroprotective mechanisms in humans after status epilepticus is scarce. One reason is the difficulty to measure possible mediators of these neuroprotective mechanisms. The dawn of microRNA detection in the cerebrospinal fluid (CSF) and the recent advancements in measuring proteins in the CSF such as progranulin, which is, e.g., responsible for neurite outgrowth and limiting exceeding neuroinflammatory responses, have given us new insights into putative neuroprotective mechanisms following status epilepticus. This should complement the animal data. In this review, we cover what is known about the role of progranulin as well as the links between microRNA changes and the progranulin pathway following status epilepticus in humans and animals hypothesizing neuroprotective and neurorehabilitative effects. Progranulin has also been found to feature prominently in the neuroprotective processes under hypoxic conditions and initiating neurorehabilitative processes. These properties may be used therapeutically, e.g., through drugs that raise the progranulin levels and therefore the cerebral progranulin levels as well with the goal of improving the outcome after status epilepticus.

Complexes formed between H 2 S and each of CuI, AgI, and AuI have been isolated and structurally characterised in the gas phase. The H 2 S⋯MI complexes (where M is the metal atom) are generated through laser vaporisation of a metal rod in the presence of a low concentration of H 2 S and CF 3 I in a buffer gas of argon undergoing supersonic expansion. The microwave spectra of six isotopologues of each of H 2 S⋯CuI, H 2 S⋯AgI and three isotopologues of H 2 S⋯AuI have been measured by chirped-pulse Fourier transform microwave spectroscopy. The spectra are interpreted to determine geometries for the complexes and to establish the values of structural parameters. The complexes have C s symmetry at equilibrium and have a pyramidal configuration about the sulfur atom. The local C 2 axis of the hydrogen sulfide molecule intersects the linear axis defined by the three heavy atoms at an angle, ϕ = 75.00(47)° for M = Cu, ϕ = 78.43(76)° for M = Ag, and ϕ = 71.587(13)° for M = Au. The trend in the molecular geometries is consistent with significant relativistic effects in the gold-containing complex. The force constant describing the interaction between the H 2 S and MI sub-units is determined from the measured centrifugal distortion constant, Δ J , of each complex. Nuclear quadrupole coupling constants, χ aa (M) and χ aa (I) (where M denotes the metal atom), are determined for H 2 S⋯CuI and H 2 S⋯AuI for the first time.

Complexes of H3NCuF and H3NCuI have been synthesised in the gas phase and characterized by microwave spectroscopy. The rotational spectra of 4 isotopologues of H3NCuF and 5 isotopologues of H3NCuI have been measured in the 6.5-18.5 GHz frequency range using a chirped-pulse Fourier transform microwave spectrometer. Each complex is generated from a gas sample containing NH3 and a halogen-containing precursor diluted in Ar. Copper is introduced by laser ablation of a solid target prior to supersonic expansion of the sample into the vacuum chamber of the microwave spectrometer. The spectrum of each complex is characteristic of a symmetric rotor and a C3v geometry in which the N, Cu and X atoms (where X is F or I) lie on the C axis. The rotational constant (B0), centrifugal distortion constants (DJ and DJK), nuclear spin-rotation (Cbb(Cu) = Ccc(Cu)) constant (for H3NCuF only) and nuclear quadrupole coupling constants (χaa(X) where (X = N, Cu, I)) are fitted to the observed transition frequencies. Structural parameters are determined from the measured rotational constants and also calculated ab initio at the CCSD(T)(F12*)/AVQZ level of theory. Force constants describing the interaction between ammonia and each metal halide are determined from DJ for each complex. Trends in the interaction strengths and geometries of BCuX (B = NH3, CO) (X = F, Cl, Br, I) are discussed.

Carbenes of platinum and palladium, PtC3 and PdC3 , were generated in the gas phase through laser vaporization of a metal target in the presence of a low concentration of a hydrocarbon precursor undergoing supersonic expansion. Rotational spectroscopy and ab initio calculations confirm that both molecules are linear. The geometry of PtC3 was accurately determined by fitting to the experimental moments of inertia of twenty-six isotopologues. The results are consistent with the proposal of an autogenic isolobal relationship between O, Au(+) , and Pt atoms., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Carbenes of platinum and palladium, PtC 3 and PdC 3 , were generated in the gas phase through laser vaporization of a metal target in the presence of a low concentration of a hydrocarbon precursor undergoing supersonic expansion. Rotational spectroscopy and ab initio calculations confirm that both molecules are linear. The geometry of PtC 3 was accurately determined by fitting to the experimental moments of inertia of twenty-six isotopologues. The results are consistent with the proposal of an autogenic isolobal relationship between O, Au + , and Pt atoms.

A two force-constant model is proposed for complexes of the type B⋯MX, in which B is a simple Lewis base of at least C2v symmetry and MX is any diatomic molecule lying along a Cn axis (n ≥ 2) of B. The model assumes a rigid subunit B and that force constants beyond quadratic are negligible. It leads to expressions that allow, in principle, the determination of three quadratic force constants F11, F12, and F22 associated with the r(B⋯M) = r2 and r(M-X) = r1 internal coordinates from the equilibrium centrifugal distortion constants DJ (e) or ΔJ (e), the equilibrium principal axis coordinates a1 and a2, and equilibrium principal moments of inertia. The model can be applied generally to complexes containing different types of intermolecular bond. For example, the intermolecular bond of B⋯MX can be a hydrogen bond if MX is a hydrogen halide, a halogen-bond if MX is a dihalogen molecule, or a stronger, coinage-metal bond if MX is a coinage metal halide. The equations were tested for BrCN, for which accurate equilibrium spectroscopic constants and a complete force field are available. In practice, equilibrium values of DJ (e) or ΔJ (e) for B⋯MX are not available and zero-point quantities must be used instead. The effect of doing so has been tested for BrCN. The zero-point centrifugal distortion constants DJ (0) or ΔJ (0) for all B⋯MX investigated so far are of insufficient accuracy to allow F11 and F22 to be determined simultaneously, even under the assumption F12 = 0 which is shown to be reasonable for BrCN. The calculation of F22 at a series of fixed values of F11 reveals, however, that in cases for which F11 is sufficiently larger than F22, a good approximation to F22 is obtained. Plots of F22 versus F11 have been provided for Kr⋯CuCl, Xe⋯CuCl, OC⋯CuCl, and C2H2⋯AgCl as examples. Even in cases where F22 ∼ F11 (e.g., OC⋯CuCl), such plots will yield either F22 or F11 if the other becomes available.

Strongly bound complexes (CH2)3⋯MCl (M = Cu or Ag), formed by non-covalent interaction of cyclopropane and either cuprous chloride or argentous chloride, have been generated in the gas phase by means of the laser ablation of either copper or silver metal in the presence of supersonically expanded pulses of a gas mixture containing small amounts of cyclopropane and carbon tetrachloride in a large excess of argon. The rotational spectra of the complexes so formed were detected with a chirped-pulse, Fourier transform microwave spectrometer and analysed to give rotational constants and Cu and Cl nuclear quadrupole coupling constants for eight isotopologues of each of (CH2)3⋯CuCl and (CH2)3⋯AgCl. The geometry of each of these complexes was established unambiguously to have C(2v) symmetry, with the three C atoms coplanar, and with the MCl molecule lying along a median of the cyclopropane C3 triangle. This median coincides with the principal inertia axis a in each of the two complexes (CH2)3⋯MCl. The M atom interacts with the pseudo-π bond linking the pair of equivalent carbon atoms (F)C (F = front) nearest to it, so that M forms a non-covalent bond to one C-C edge of the cyclopropane molecule. The (CH2)3⋯MCl complexes have similar angular geometries to those of the hydrogen- and halogen-bonded analogues (CH2)3⋯HCl and (CH2)3⋯ClF, respectively. Quantitative details of the geometries were determined by interpretation of the observed rotational constants and gave results in good agreement with those from ab initio calculations carried out at the CCSD(T)(F12*)/aug-cc-pVTZ-F12 level of theory. Interesting geometrical features are the lengthening of the (F)C-(F)C bond and the shrinkage of the two equivalent (B)C-(F)C (B = back) bonds relative to the C-C bond in cyclopropane itself. The expansions of the (F)C-(F)C bond are 0.1024(9) Å and 0.0727(17) Å in (CH2)3⋯CuCl and (CH2)3⋯AgCl, respectively, according to the determined r0 geometries. The C-C bond lengthening is in each case about four times that observed by similar methods in the corresponding complexes of MCl with ethyne and ethene, even though the cyclopropane complexes are more weakly bound than their ethyne and ethene analogues. Reasons for the larger increase in r(CC) in the pseudo-π complexes are discussed.

A weakly-bound complex of SF6 and NH3 is generated within an expanding gas jet and characterised by broadband rotational spectroscopy. The spectra of isotopologues (32) SF6 ⋅⋅⋅(14) NH3 , (32) SF6 ⋅⋅⋅(14) ND3 , (32) SF6 ⋅⋅⋅(15) NH3 and (34) SF6 ⋅⋅⋅(15) NH3 are observed and assigned to determine the spectroscopic parameters. These parameters are consistent with the complex having a C3v symmetric rotor geometry, in which the nitrogen atom of NH3 coordinates to SF6 such that the C3v axis of the NH3 sub-unit is aligned with a local C3 axis on the SF6 sub-unit. The geometry of the complex is rationalized in terms of a σ-hole interaction. The observed spectra and ab initio calculations also reveal evidence of internal dynamics involving internal rotation of one monomer sub-unit with respect to the other about the symmetry axis of the complex., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A new molecule C 2 H 2 ···CuF has been synthesized in the gas phase by means of the reaction of laser-ablated metallic copper with a pulse of gas consisting of a dilute mixture of ethyne and sulfur hexafluoride in argon. The ground-state rotational spectrum was detected by two types of Fourier-transform microwave spectroscopy, namely that conducted in a microwave Fabry-Perot cavity and the chirped-pulse broadband technique. The spectroscopic constants of the six isotopologues 12 C 2 H 2 ··· 63 Cu 19 F, 12 C 2 H 2 ··· 65 Cu 19 F, 13 C 2 H 2 ··· 63 Cu 19 F, 13 C 2 H 2 ··· 65 Cu 19 F, 12 C 2 D 2 ··· 63 Cu 19 F and 12 C 2 D 2 ··· 65 Cu 19 F were determined and interpreted to show that the molecule has a planar, T-shaped geometry belonging to the molecular point group C 2v , with CuF forming the stem of the T. Quantitative interpretation reveals that the ethyne molecule is distorted when subsumed into the complex in such manner that the C[triple bond, length as m-dash]C bond lengthens (by δr ) and the two H atoms cease to be collinear with the C[triple bond, length as m-dash]C internuclear line. The H atoms move symmetrically away from the approaching Cu atom of CuF, to increase each *[triple bond, length as m-dash]C-H angle by δA = 14.65(2)°, from 180° to 194.65(2)°. Ab initio calculations at the explicitly-correlated level of theory CCSD(T)(F12*)/aug-cc-pVTZ lead to good agreement with the experimental geometry. It is shown that similar distortions δr and δA , similarly determined, for four complexes C 2 H 2 ···MX (M = Cu or Ag; X = F, Cl or CCH) are approximately linearly related to the energies D e for the dissociation process C 2 H 2 ···MX = C 2 H 2 + MX., (This journal is © The Royal Society of Chemistry 2015.)

The H3N⋯CuCl monomer has been generated and isolated in the gas phase through laser vaporisation of a copper sample in the presence of low concentrations of NH3 and CCl4 in argon. The resulting complex cools to a rotational temperature approaching 2 K during supersonic expansion of the gas sample and is characterised by broadband rotational spectroscopy between 7 and 18.5 GHz. The spectra of six isotopologues are measured and analysed to determine rotational, B0; centrifugal distortion, DJ, DJK; and nuclear quadrupole coupling constants of Cu, Cl, and (14)N nuclei, χaa (X). The geometry of the complex is C3v with the N, Cu, and Cl atoms located on the a inertial axis. Bond distances and the ∠(H -N⋯Cu) bond angle within the complex are precisely evaluated through fitting of geometrical parameters to the experimentally determined moments of inertia and through ab initio calculations at the CCSD(T)(F12*)/AVQZ level. The r(Cu -Cl), r(Cu -N), and ∠(H -N⋯Cu) parameters are, respectively, evaluated to be 2.0614(7) Å, 1.9182(13) Å, and 111.40(6)° in the r0 geometry, in good agreement with the ab initio calculations. Geometrical parameters evaluated for the isolated complex are compared with those established crystallographically for a solid-state sample of [Cu(NH3)Cl].

Background: Analysis of cerebrospinal fluid (CSF) has improved over the last few years; thus specific markers for different diseases have emerged, e.g., amyloid-β (Aβ) for Alzheimer's disease (AD) and progranulin for frontotemporal dementia (FTD)., Objective: Evaluation of correlation between biomarkers in CSF and cognitive performance in populations with AD and FTD., Methods: 27 patients with AD and 16 with FTD were included. CSF tau, P-tau(181P), Aβ₄₂, and progranulin (PGRN) were measured and a standardized neuropsychological test battery applied. Olfactory testing was additionally included where available., Results: For all patients across both groups, an association between PGRN and categoric (p = 0.016) and letter fluency (p = 0.029), naming (p = 0.003), and overall cognition (Mini-Mental State Examination: p = 0.04) was observed. Aβ42 was strongly associated with memory function (learning: p = 0.001; recall: p = 0.002). A correlation between Aβ₄₂ and memory performance was moreover found for each group separately, while PGRN also showed a correlation with recognition memory (p = 0.04) in AD. Furthermore, an association between reduced PGRN and olfactory dysfunction was revealed (p = 0.01)., Conclusions: CSF-levels of PGRN and Aβ₄₂ levels express deficits in cognition differentially, with PGRN being predominantly associated with frontal and Aβ₄₂ with temporal dysfunction. This mirrors the cerebral occurrence of these proteins. These associations appear to be consistent across both disease groups. The relationship between PGRN and olfaction further underpins the association between PRGN and frontal dysfunction.

The molecular geometries of isolated complexes in which a single molecule of C2H4 or C2H2 is bound to CuCl have been determined through pure rotational spectroscopy and ab-initio calculations. The C2H2···CuCl and C2H4···CuCl complexes are generated through laser vaporization of a copper rod in the presence of a gas sample undergoing supersonic expansion and containing C2H2 (or C2H4), CCl4, and Ar. Results are presented for five isotopologues of C2H2···CuCl and six isotopologues of C2H4···CuCl. Both of these complexes adopt C(2v), T-shaped geometries in which the hydrocarbon binds to the copper atom through its π electrons such that the metal is equidistant from all H atoms. The linear and planar geometries of free C2H2 and C2H4, respectively, are observed to distort significantly on attachment to the CuCl unit, and the various changes are quantified. The ∠(*-C-H) parameter in C2H2 (where * indicates the midpoint of the C≡C bond) is measured to be 192.4(7)° in the r0 geometry of the complex representing a significant change from the linear geometry of the free molecule. This distortion of the linear geometry of C2H2 involves the hydrogen atoms moving away from the copper atom within the complex. Ab-initio calculations at the CCSD(T)(F12*)/AVTZ level predict a dihedral ∠(HCCCu) angle of 96.05° in C2H4···CuCl, and the experimental results are consistent with such a distortion from planarity. The bonds connecting the carbon atoms within each of C2H2 and C2H4, respectively, extend by 0.027 and 0.029 Å relative to the bond lengths in the isolated molecules. Force constants, k(σ), and nuclear quadrupole coupling constants, χ(aa)(Cu), [χ(bb)(Cu) - χ(cc)(Cu)], χ(aa)(Cl), and [χ(bb)(Cl) - χ(cc)(Cl)], are independently determined for all isotopologues of C2H2···CuCl studied and for four isotopologues of C2H4···CuCl.

Background: Recent work suggests that ALS and frontotemporal dementia can occur together and share at least in part the same underlying pathophysiology. However, it is unclear at present whether memory deficits in ALS stem from a temporal lobe dysfunction, or are rather driven by frontal executive dysfunction. In this study we sought to investigate the nature of memory deficits by analyzing the neuropsychological performance of 40 ALS patients in comparison to 39 amnestic mild cognitive impairment (aMCI) patients and 40 healthy controls (HC). The neuropsychological battery tested for impairment in executive functions, as well as memory and visuo-spatial skills, the results of which were compared across study groups. In addition, we calculated composite scores for memory (learning, recall, recognition) and executive functions (verbal fluency, cognitive flexibility, working memory). We hypothesized that the nature of memory impairment in ALS will be different from those exhibited by aMCI patients., Results: Patient groups exhibited significant differences in their type of memory deficit, with the ALS group showing impairment only in recognition, whereas aMCI patients showed short and delayed recall performance deficits as well as reduced short-term capacity. Regression analysis revealed a significant impact of executive function on memory performance exclusively for the ALS group, accounting for one fifth of their memory performance. Interestingly, merging all sub scores into a single memory and an executive function score obscured these differences., Conclusion: The presented results indicate that the interpretation of neuropsychological scores needs to take the distinct cognitive profiles in ALS and aMCI into consideration. Importantly, the observed memory deficits in ALS were distinctly different from those observed in aMCI and can be explained only to some extent in the context of comorbid (coexisting) executive dysfunction. These findings highlight the qualitative differences in temporal lobe dysfunction between ALS and aMCI patients, and support temporal lobe dysfunction as a mechanism underlying the distinct cognitive impairments observed in ALS.

It was investigated whether alterations of the pupil's light reflex might reflect Alzheimer's disease (AD) pathology. Changes in the pupil's system might be expected due to AD pathology present in the oculomotor system of the Edinger-Westphal nucleus, and a cholinergic deficit caused by degeneration of the nucleus basalis Meynert. A rather new method of repetitive light stimulation was applied assessing variations in pupil size, latency, and amplitude over time. We analyzed 44 healthy controls, 42 subjects with mild cognitive impairment (MCI), and 66 AD patients. AD and MCI showed a less pronounced pupil size decrease and amplitude increase over time than controls. A higher MMSE was associated with a higher increase of relative amplitude and greater decrease of latency in AD and MCI, and absolute amplitude increase in AD alone. Pupil size increase correlated with cerebrospinal fluid markers in AD. Summarized pupil light reflex is not stable under repetitive stimulation, but changes systematically and less pronounced in AD and MCI. Thus repetitive stimulation of the pupil's response potentially indicates AD pathology.

Background: In Alzheimer's disease (AD), levels of N-acetylaspartate (NAA) is diminished and choline (Cho) and myo-inositol (mI) are increased. In cerebrospinal fluid (CSF), tau and phosphoylated tau (p-tau181P) is increased and amyloid-β(1-42) (Aβ42) decreased., Objectives: 1) To compare metabolites of different 1H-MRS voxels and assess its utility to differentiate AD from controls and to examine the relationship to cognition and to CSF markers., Methods: 17 healthy controls and 19 AD subjects were studied using 1H-MRS. In the AD cases, additional CSF analysis was obtained., Results: Relative to controls, AD subjects had reduced NAA/Creatine (Cr) levels in hippocampus (42.3% to 26.0%, p < 0.001), posterior cingulate gyrus (10.4% to 0.2%, p = 0.04), and parietal lobe (14.9% to 3.8%, p = 0.002). Further differences of Cho/Cr and mI/Cr in the hippocampus (Cho/Cr: p = 0.04; mI/Cr: p = 0.015) and posterior cingulate (Cho/Cr: p = 0.001; mI/Cr: p = 0.001) were observed. NAA/Cr of the hippocampus yielded the highest sensitivity (94.1%) and specificity (92.3%) to differentiate AD from controls. NAA/Cr was associated with general cognition (hippocampus: R = 0.68, p < 0.001; parietal lobe: R = 0.57, p = 0.001; posterior cingulate: R = 0.50, p = 0.003). Higher hippocampal NAA/Cr was related to higher CSF Aβ42, while lower parietal NAA/Cr was associated with a higher CSF total tau (t-tau) and p-tau181P. Posterior cingulate mI/Cr was related to CSF t-tau and NAA/mI., Conclusion: 1H-MRS is an appropriate measure in AD. Measurement at different regions presumably reflects different pathological changes.

Clinically, Alzheimer's disease (AD) is by far the most common cause of dementia. Criteria for the diagnosis of dementia with Lewy bodies (DLB) are highly specific but not at all sensitive, which is reflected by the higher number of DLB cases detected histopathologically at autopsy. Imaging of dopamine transporter with FP-CIT SPECT is one possibility to increase sensitivity. Pathological confirmation was also included in the revised consensus criteria for the diagnosis of DLB. However, in the absence of parkinsonism, one of the core features, a clinical diagnosis of AD is more likely. The role of FP-CIT SPECT in DLB diagnosis remains to be clarified. Based on our 3 case reports and a review of the literature, the utility of this imaging method in the differential diagnosis of AD and DLB is highlighted.

In the continuum of patients with Alzheimer's disease (AD), mild cognitive impairment (MCI), and normal controls, a possible association of verbal memory and endogenous estradiol (E(2)) levels was investigated. Verbal episodic memory was measured with a german version of the California verbal memory test (CVLT). Results were controlled for apolipoprotein E (ApoE) phenotype. We studied 37 controls, 32 MCIs and 117 ADs. Groups differed in all trials of the CVLT (P < 0.001) and in E(2) levels (P < 0.001). E2 levels differed significantly between groups only among females (P < 0.001). In females correcting for age and ApoE, there was an overall correlation between CVLT delayed recall and level of E(2) (P = 0.025). Stepwise regression analyses found E(2) level to be a significant predictor for CVLT delayed recall (P < 0.001). It may be concluded that lower E(2) levels occur more in the course of the disease than may be considered as a risk factor per se.