The plant sterol brassicasterol as additional CSF biomarker in Alzheimer's disease

OBJECTIVE

Plant sterols (sitosterol, campesterol, stigmasterol and brassicasterol) are solely dietary-derivable sterols that are structurally very similar to cholesterol. In contrast to peripheral cholesterol, plant sterols can cross the blood-brain barrier and accumulate within mammalian brain. As an impaired function of the cerebrospinal fluid (CSF)-blood barrier is linked to neurodegenerative disorders, i.e. Alzheimer's disease (AD), we investigated whether this results in altered plant sterol concentrations in CSF.

METHOD

Applying gas chromatography/mass spectrometry analysis, plant sterol concentrations were measured in plasma and CSF of patients with AD (n = 67) and controls (n = 29). Age, gender, plasma-to-CSF albumin ratio, CSF Aβ(42) , CSF pTau, APOE4 genotype, and serum creatinine were applied as covariates in the statistical analysis for individual plant sterols in order to compare plasma and CSF plant sterol concentrations between patients with AD and controls.

RESULTS

Albumin quotient was a consistent predictor in CSF for cholesterol and methyl plant sterols campesterol and brassicasterol. Comparison of lipid parameters per diagnosis based on relevant predictors revealed significantly lower concentrations of brassicasterol (P < 0.001) in CSF of patients with AD. Binary logistic regression analysis revealed that brassicasterol improved the predictive value when added to pTau and Aβ42 in a biomarker model.

CONCLUSION

Brassicasterol might be a relevant additional biomarker in AD.

Interaction effects of subjective memory impairment and ApoE4 genotype on episodic memory and hippocampal volume

BACKGROUND

The apolipoprotein E4 allele (ApoE4) is an established genetic risk factor for Alzheimer's disease (AD). However, its effects on cognitive performance and brain structure in healthy individuals are complex. We investigated the effect of ApoE4 on cognitive performance and medial temporal lobe volumetric measures in cognitively unimpaired young elderly with and without subjective memory impairment (SMI), which is an at-risk condition for dementia.MethodAltogether, 40 individuals with SMI and 62 without were tested on episodic memory and on tasks of speed and executive function. All participants were ApoE genotyped. 21 subjects with SMI and 47 without received additional structural magnetic resonance imaging. Volumetric measures of the hippocampus, the entorhinal cortex and the amygdala were obtained manually.

RESULTS

In the SMI group, ApoE4 carriers performed worse on the episodic memory (p=0.049) and showed smaller left hippocampal volumes (p=0.030). In the individuals without SMI, the ApoE4 carriers performed better on episodic memory (p=0.018) and had larger right hippocampal volumes (p=0.039). The interaction of group (SMI/no SMI) and ApoE genotype was significant for episodic memory (p=0.005) and right and left hippocampal volumes (p=0.042; p=0.035). There were no within-group differences or interaction effects on speed and executive function composite measures or other volumetric measures.

CONCLUSIONS

The negative effect of ApoE4 on episodic memory and hippocampal volume in SMI supports SMI as a prodromal condition of AD. The positive effects of ApoE4 in subjects without SMI adds to a number of reports on positive ApoE4 effects in young and very old individuals.

A claims-based Markov model for Crohn's disease

BACKGROUND

Crohn's disease is a chronic condition that often presents in early adulthood.

AIM

To evaluate health care costs and costs per quality-adjusted life year (QALY) for Crohn's disease.

METHODS

A Markov model was developed using administrative claims data for patients aged > or = 18 years with > or = 3 years of continuous enrolment from 2000 to 2008 and > or =2 Crohn's disease claims. Disease states (remission, mild-moderate, moderate-severe, and severe-fulminant) were defined using the American College of Gastroenterology treatment guidelines criteria. Transition probabilities were calculated from consecutive 6-month periods. Costs were determined from paid claims and QALY utilities were obtained from the literature. The model assumed a 30-year-old patient at the time of entry into the model.

RESULTS

There were 40 063 patients identified, with a total of 420 773 cycles [remission (197 111; 46.8%), mild-moderate (44 024; 10.5%), moderate-severe (132 695; 31.5%), severe-fulminant (46 925; 11.2%)]. The costs/QALY for remission, mild-moderate, moderate-severe, and severe-fulminant disease states respectively were $2896, $8428, $11 518 and $69 277 for males and $2896, $8426, $22 633 and $69 412 for females.

CONCLUSIONS

Overall, health care costs for patients with Crohn's disease increased with disease severity. Although the probabilities of transitioning from other health states to the severe-fulminant disease state were low, the cost/QALY was high.

Doubly resonant optical nanoantenna arrays for polarization resolved measurements of surface-enhanced Raman scattering

We report that rhomb-shaped metal nanoantenna arrays support multiple plasmonic resonances, making them favorable bio-sensing substrates. Besides the two localized plasmonic dipole modes associated with the two principle axes of the rhombi, the sample supports an additional grating-induced surface plasmon polariton resonance. The plasmonic properties of all modes are carefully studied by far-field measurements together with numerical and analytical calculations. The sample is then applied to surface-enhanced Raman scattering measurements. It is shown to be highly efficient since two plasmonic resonances of the structure were simultaneously tuned to coincide with the excitation and the emission wavelength in the SERS experiment. The analysis is completed by measuring the impact of the polarization angle on the SERS signal.

Temperature-dependent Raman study of the smectic to nematic phase transition and vibrational analysis using density functional theory of the liquid crystalline system 4-decyloxy benzoic acid

Room-temperature Raman spectra of the thermotropic liquid crystalline system, 4-decyloxy benzoic acid (4DBA) have been recorded and the experimentally observed bands are assigned by density functional theory (DFT) for the first time. The C-O and C-C stretching and C-H in-plane bending modes of the phenyl ring and C=O stretching modes of the -COOH group are the marker bands for the smectic (S) --> nematic (N) and nematic (N) --> isotropic (I) transitions for this system. The temperature-dependent Raman spectra for these bands in the heating cycle clearly characterize the S-->N and the N-->I transition over a range <1 degree C, which is much better than the earlier range of 23 degrees C for S-->N and 26 degrees C for the N-->I transition. The approximately 773, approximately 807, approximately 881, and approximately 1146 cm(-1) bands disappear, whereas a band at approximately 830 cm(-1) appears at the S-->N transition. The relative intensity of the approximately 1257 and approximately 1280 cm(-1) bands distinguishes the three phases, namely smectic, nematic, and isotropic, in 4DBA. The variation of line width and peak wavenumber of the approximately 1128 and approximately 1168 cm(-1) bands also clearly shows the two transitions. The molecular reorientation at the transition and the effect of local fields present in the liquid crystalline mesophases are also briefly discussed on the basis of changes in intensity, linewidth and peak wavenumber with temperature.

Soluble amyloid precursor proteins in the cerebrospinal fluid as novel potential biomarkers of Alzheimer's disease: a multicenter study

In this report, we present the results of a multicenter study to test analytic and diagnostic performance of soluble forms of amyloid precursor proteins alpha and beta (sAPP alpha and sAPP beta) in the cerebrospinal fluid (CSF) of patients with different forms of dementing conditions. CSF samples were collected from 188 patients with early dementia (mini-mental state examination >or=20 in majority of cases) and mild cognitive impairment (MCI) in 12 gerontopsychiatric centers, and the clinical diagnoses were supported by neurochemical dementia diagnostic (NDD) tools: CSF amyloid beta peptides, Tau and phospho-Tau. sAPP alpha and sAPP beta were measured with multiplexing method based on electrochemiluminescence. sAPP alpha and sAPP beta CSF concentrations correlated with each other with very high correlation ratio (R=0.96, P<0.001). We observed highly significantly increased sAPP alpha and sAPP beta CSF concentrations in patients with NDD characteristic for Alzheimer's disease (AD) compared to those with NDD negative results. sAPP alpha and sAPP beta highly significantly separated patients with AD, whose diagnosis was supported by NDD findings (sAPP alpha: cutoff, 117.4 ng ml(-1), sensitivity, 68%, specificity, 85%, P<0.001; sAPP beta: cutoff, 181.8 ng ml(-1), sensitivity, 75%, specificity, 85%, P<0.001), from the patients clinically assessed as having other dementias and supported by NDD untypical for AD. We conclude sAPP alpha and sAPP beta might be regarded as novel promising biomarkers supporting the clinical diagnosis of AD.

Vibrational spectroscopy--a powerful tool for the rapid identification of microbial cells at the single-cell level

Rapid microbial detection and identification with a high grade of sensitivity and selectivity is a great and challenging issue in many fields, primarily in clinical diagnosis, pharmaceutical, or food processing technology. The tedious and time-consuming processes of current microbiological approaches call for faster ideally on-line identification techniques. The vibrational spectroscopic techniques IR absorption and Raman spectroscopy are noninvasive methods yielding molecular fingerprint information; thus, allowing for a fast and reliable analysis of complex biological systems such as bacterial or yeast cells. In this short review, we discuss recent vibrational spectroscopic advances in microbial identification of yeast and bacterial cells for bulk environment and single-cell analysis. IR absorption spectroscopy enables a bulk analysis whereas micro-Raman-spectroscopy with excitation in the near infrared or visible range has the potential for the analysis of single bacterial and yeast cells. The inherently weak Raman signal can be increased up to several orders of magnitude by applying Raman signal enhancement methods such as UV-resonance Raman spectroscopy with excitation in the deep UV region, surface enhanced Raman scattering, or tip-enhanced Raman scattering.

Association of CETP polymorphisms with the risk of vascular dementia and white matter lesions

Cholesteryl ester transfer protein (CETP), a component of the high density lipoprotein (HDL), plays a central role in reverse cholesterol transport. We investigated the association of two putative functional CETP polymorphisms (C-629A and I405V) with the risk of vascular dementia (VD) and tested if this association is influenced by the presence of APOE4 allele. Our study included 163 VD patients (mean age: 74.25 +/- 7.9 years) and 452 cognitively healthy probands (mean age: 70.81 +/- 7.9 years). As a biological correlate, the association of CETP gene variants with white matter lesion (WML) load was investigated. Neither the C-629A (P = 0.169) nor the I405V (P = 0.840) polymorphism was associated with VD risk in the whole sample. However, in non-carriers of the APOE4 allele, homozygote carriers of the CETP C-629A A allele presented with an increased risk of VD (P = 0.01). Whereas in APOE4 carriers, no association of CETP polymorphisms with VD risk was detected. In addition, carriers of the CETP C-629A AA genotype presented with decreased WML load in the frontal brain (P = 0.009). Our results suggest that CETP gene polymorphisms might influence WML load and the risk of VD, the latter in non-carriers of the APOE4 allele.

KIBRA gene variants are associated with episodic memory in healthy elderly

The first hypothesis free genome wide association study on cognition recently revealed the thus far unknown association of a single nucleotide polymorphism (SNP) of the KIBRA gene with episodic memory in healthy young and middle aged volunteers. Here, we report the first independent replication of this finding in an in-depth characterized sample of healthy elderly subjects. The effectsizes of the respective KIBRA SNP on memory even exceed those of the initial report. In parallel to the first study, the effect is restricted to hippocampus-related episodic memory without effects on frontal lobe function. The impact of KIBRA on memory is most likely of high relevance in elderly subjects as it is in young.

Optically controlled thermal management on the nanometer length scale

The manipulation of polymers and biological molecules or the control of chemical reactions on a nanometer scale by means of laser pulses shows great promise for applications in modern nanotechnology, biotechnology, molecular medicine or chemistry. A controllable, parallel, highly efficient and very local heat conversion of the incident laser light into metal nanoparticles without ablation or fragmentation provides the means for a tool like a 'nanoreactor', a 'nanowelder', a 'nanocrystallizer' or a 'nanodesorber'. In this paper we explain theoretically and show experimentally the interaction of laser radiation with gold nanoparticles on a polymethylmethacrylate (PMMA) layer (one-photon excitation) by means of different laser pulse lengths, wavelengths and pulse repetition rates. To the best of our knowledge this is the first report showing the possibility of highly local (in a 40 nm range) regulated heat insertion into the nanoparticle and its surroundings without ablation of the gold nanoparticles. In an earlier paper we showed that near-infrared femtosecond irradiation can cut labeled DNA sequences in metaphase chromosomes below the diffraction-limited spot size. Now, we use gold as well as silver-enhanced gold nanoparticles on DNA (also within chromosomes) as energy coupling objects for femtosecond laser irradiation with single-and two-photon excitation. We show the results of highly localized destruction effects on DNA that occur only nearby the nanoparticles.

[Diagnostic lumbar puncture performed in the outpatient setting of a memory clinic. Frequency and risk factors of post-lumbar puncture headache]

Lumbar puncture (LP) is growing in relevance for the diagnosis of cognitive impairment in the elderly. Due to the expected risk of post-lumbar puncture syndrome or other complications LPs have rarely been performed in the outpatient setting. Using a questionnaire, the post-lumbar puncture symptoms of 100 patients (54-84 years old; mean: 68.87 years; SD: 7.9) have been prospectively gathered after consecutively performed LPs in the Memory Clinic of the Department of Psychiatry, University of Bonn. Some of these patients were included in the early diagnosis program of the German Dementia Competence Network. Of the patients 9% developed a post-lumbar puncture syndrome of mild or middle intensity. The influence of gender, age, cognitive status, as well as a supplementary diagnosis of depression and needle size (G20 or G22 atraumatic Sprotte needle) on the incidence of the post-LP syndrome was evaluated by means of logistic regression. Only the patients' age was identified as a significant risk factor as with increasing age a diminishing risk of developing a post-lumbar puncture syndrome was found (OR=0.83; CI=0.71-0.97 per year). None of the other factors evaluated proved to be of significant influence. The post-LP symptoms did not necessitate supplementary consultations in any of the cases.

Gene variations in GSTM3 are a risk factor for Alzheimer's disease

Oxidative stress is a relevant pathomechanism in Alzheimer's disease (AD) and gene variations in the glutathione S-transferase M3 gene (GSTM3), involved in the detoxification of oxygen radicals, might influence the risk of AD. We investigated the effect of three polymorphisms in GSTM3: rs1332018 (C/A); rs1799735 (del/AGG); rs7483 (G/A), on the risk of AD in 363 AD patients and 358 healthy controls. Single marker association analyses revealed that the AGG/AGG genotype of the GSTM3 rs1799735 (del/AGG) polymorphism was associated with an increased risk of AD (p=0.05), especially in the group of APOE4-allele non-carriers (p=0.004; OR=2.07). Examination of the haplotypes identified a two-marker haplotype (C/AGG) consisting of rs1332018 (C/A) and rs1799735 (del/AGG) to increase the risk of AD (p=0.029), this effect was also most prevalent in APOE4-allele non-carriers (p=0.009; OR=1.95). The population attributable risk of this haplotype in APOE4-allele non-carriers was 32.2%. Our results suggest that there is a group of AD patients in which variations in metabolism of oxidative stress play an important role.

The Influence of Fluoroquinolone Drugs on the Bacterial Growth of S. epidermidis Utilizing the Unique Potential of Vibrational Spectroscopy

Increasing resistance of many antibiotics has made the design of new drugs necessary. To assist a target-oriented search for new structures and for the elucidation of the mode of action of existing drugs, powerful analytical techniques are required. In this work, vibrational spectroscopy is used to shed more light on the as-yet elusive interaction of gyrase inhibitors of the fluoroquinolone type with their biological target inside the Gram-positive bacterium Staphylococcus epidermidis by investigating whole-cell changes that occur as a result of the presence of the drug moxifloxacin. IR absorption and Raman spectra with excitation off resonance (lambda exc = 532 nm) and in resonance with the biological targets DNA and the aromatic amino acids of gyrase (lambda exc = 244 nm) were recorded for unperturbed bacteria and bacteria in varying drug concentrations (0.08, 0.16, 0.27, and 0.62 microg moxifloxacin/mL bacterial culture). The spectral changes caused by the action of the drug were analyzed with the help of statistical methods, such as hierarchical cluster analysis (HCA), principal component analysis (PCA), and Fisher's linear discriminant analysis (LDA) combined with variable selection. The wavenumbers mostly affected by the action of the drug could be assigned to protein and DNA moieties, supporting the proposed mechanisms of a tertiary complex of the fluoroquinolone, the enzyme gyrase, and DNA.

Gold Films Deposited over Regular Arrays of Polystyrene Nanospheres as Highly Effective SERS Substrates from Visible to NIR

Gold nanostructured films of various thicknesses (15, 30, and 60 nm) are deposited over regular arrays of polystyrene nanospheres in an attempt to evaluate their potential as SERS-active substrates. Atomic force microscopy is used to topographically characterize the substrates as well as to ensure the thickness of the deposited gold films. The optical response of the prepared substrates recommends their use in SERS experiments with multiple laser lines from visible and NIR spectral domains. The assessment of the substrates' SERS activity is performed by using the 532, 633, and 830 nm excitation lines and different average enhancement factor (EF) values are obtained depending on the film thickness and employed laser line. The 60 nm gold nanostructured film generates the greatest local electromagnetic field confinement under NIR excitation and consequently gives rise to maximum SERS enhancement. The large tunability of surface plasmon excitation combined with the advantage of relatively high exhibited average EF values obtained under NIR excitation recommends these substrates as outstanding candidates for upcoming investigations of biological relevant molecules.

Symmetry Properties of Vibrational Modes in Mesoporphyrin IX Dimethyl Ester Investigated by Polarization-Sensitive Resonance Raman and CARS Spectroscopy

The symmetry properties of selected vibrational modes of mesoporphyrin IX dimethyl ester (MP-IX-DME) in solution are investigated under different electronic resonance conditions. The Raman band parameters of the macrocycle modes nu(2), nu(10), nu(11), and nu(19) are determined from a quantitative analysis of polarized spontaneous resonance Raman (RR) and polarization-sensitive (PS) multiplex coherent anti-Stokes Raman scattering (CARS) spectra obtained with pre-resonant B band and resonant Qx band excitation, respectively. Additionally, the molecular geometry and the vibrational modes of MP-IX-DME are calculated by employing density functional theory (DFT) on the B3LYP/6-31G(d) level. Both the DFT-derived structure and the Raman spectroscopic parameters of MP-IX-DME indicate minor deviations from an ideal D2h macrocycle symmetry. To assess the influence of the beta substitution pattern on the in-plane symmetry, calculated normal-mode vectors and several experimentally detected parameters, such as peak positions, depolarization ratios, and coherent phases, are analyzed. The effects of the macrocycle substitution pattern are different for the selected vibrational modes: nu(2) in particular is very sensitive to subtle perturbations of the in-plane symmetry. The considerable activity of totally symmetric vibrations observed in the PS CARS spectra of MP-IX-DME and the correlation of mode symmetries with coherent phases confirm earlier PS CARS results on octaethylporphine (OEP) acquired under the same electronic resonance conditions.