Aptamer-assisted bioconjugation of tyrosine derivatives with hemin/G-quadruplex (hGQ) DNAzyme nucleoapzyme nanostructures

Hemin/G-quadruplex (hGQ) DNAzymes are horseradish peroxidase-mimicking catalysts capable of the oxidation of a variety of substrates. We now implement aptamer-functionalized hGQ DNAzymes, also known as nucleoapzymes, to achieve increased bioconjugation of N-methyl luminol to tyrosine-containing residues and peptides. We found that the presence of a tyrosinamide-binding aptamer leads to a 12-fold increase in the catalytic rate constant (k(cat)), and the saturation kinetics curves that were obtained provide evidence for the involvement of the substrate binding site in the reaction. The application of the best performing nucleoapzymes for the modification of Tyr-containing peptides reveals that (i) the aptamer also recognizes the ligand structure when this is embedded in a larger peptide structure, and (ii) distant residues in the peptide substrate can influence the conversion. As such, we show that nucleoapzymes display enzyme-like features and provide an additional tool in the toolbox of bioconjugation chemistry.FWN – Publicaties zonder aanstelling Universiteit Leide

Prognosis and Survival of Older Patients With Dizziness in Primary Care:a 10-year prospective cohort study

Purpose: The prognosis of dizzy older patients in primary care is unknown. Our objective was to determine the prognosis and survival of patients with different subtypes and causes of dizziness. Methods: In a primary care prospective cohort study, 417 older adults with dizziness (mean age 75.5 years) received a full diagnostic workup in 2006-2008. A panel of physicians classified their dizziness subtype and primary cause of dizziness. Presyncope was the most common dizziness subtype (69.1%), followed by vertigo (41.0%), disequilibrium (39.8%), and other dizziness (1.7%). The most common primary causes of dizziness were cardiovascular disease (56.8%) and peripheral vestibular disease (14.4%). Main outcome measures were mortality and dizziness-related impairment assessed at 10-year follow-up.Results: At 10-year follow-up 169 patients (40.5%) had died. Multivariable adjusted Cox models showed a lower mortality rate for patients with the subtype vertigo compared to other subtypes (HR 0.62 (95% CI 0.40 to 0.96)), and for peripheral vestibular disease versus cardiovascular disease as primary cause of dizziness (HR 0.46 (95% CI 0.25 to 0.84)). After 10 years, 47.7% of patients who filled out the follow-up measurement experienced substantial dizziness-related impairment. No significant difference in substantial impairment was seen between different subtypes and primary causes of dizziness. Conclusions: The 10-year mortality rate was lower for the dizziness subtype vertigo compared to other subtypes. Patients with dizziness primarily caused by peripheral vestibular disease had a lower mortality rate than patients with cardiovascular disease. Substantial dizziness-related impairment in older dizzy patients 10 years later is high, and indicates that current treatment strategies by FPs may be suboptimal.<br/

Profiling Dizziness in Older Primary Care Patients: An Empirical Study

The diagnostic approach to dizzy, older patients is not straightforward as many organ systems can be involved and evidence for diagnostic strategies is lacking. A first differentiation in diagnostic subtypes or profiles may guide the diagnostic process of dizziness and can serve as a classification system in future research. In the literature this has been done, but based on pathophysiological reasoning only

Predictors of dizziness in older persons: a 10-year prospective cohort study in the community

BACKGROUND: The current diagnosis-oriented approach of dizziness does not suit older patients. Often, it is difficult to identify a single underlying cause, and when a diagnosis is made, therapeutic options may be limited. Identification of predictors of dizziness may provide new leads for the management of dizziness in older patients. The aim of the present study was to investigate long-term predictors of regular dizziness in older persons. METHODS: Population-based cohort study of 1,379 community-dwelling participants, aged ≥60 years, from the Longitudinal Aging Study Amsterdam (LASA). Regular dizziness was ascertained during face-to-face medical interviews during 7- and 10-year follow-up. We investigated 26 predictors at baseline from six domains: socio-demographic, medical history, medication, psychological, sensory, and balance/gait. We performed multivariate logistic regression analyses with presence of regular dizziness at 7- and 10-year follow-up as dependent variables. We assessed the performance of the models by calculating calibration and discrimination. RESULTS: Predictors of regular dizziness at 7-year follow-up were living alone, history of dizziness, history of osteo/rheumatoid arthritis, use of nitrates, presence of anxiety or depression, impaired vision, and impaired function of lower extremities. Predictors of regular dizziness at 10-year follow-up were history of dizziness and impaired function of lower extremities. Both models showed good calibration (Hosmer-Lemeshow P value of 0.36 and 0.31, respectively) and acceptable discrimination (adjusted AUC after bootstrapping of 0.77 and 0.71). CONCLUSIONS: Dizziness in older age was predicted by multiple factors. A multifactorial approach, targeting potentially modifiable predictors (e.g., physical exercise for impaired function of lower extremities), may add to the current diagnosis-oriented approach. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/1471-2318-14-133) contains supplementary material, which is available to authorized users

Development of a diagnostic protocol for dizziness in elderly patients in general practice: a Delphi procedure

<p>Abstract</p> <p>Background</p> <p>Dizziness in general practice is very common, especially in elderly patients. The empirical evidence for diagnostic tests in the evaluation of dizziness is scarce. Aim of our study was to determine which set of diagnostic tests should be part of a diagnostic protocol for evaluating dizziness in elderly patients in general practice.</p> <p>Methods</p> <p>We conducted a Delphi procedure with a panel of 16 national and international experts of all relevant medical specialities in the field of dizziness. A selection of 36 diagnostic tests, based on a systematic review and practice guidelines, was presented to the panel. Each test was described extensively, and data on test characteristics and methodological quality (assessed with the Quality Assessment of Diagnostic Accuracy Studies, QUADAS) were presented. The threshold for in- or exclusion of a diagnostic test was set at an agreement of 70%.</p> <p>Results</p> <p>During three rounds 21 diagnostic tests were selected, concerning patient history (4 items), physical examination (11 items), and additional tests (6 items). Five tests were excluded, although they are recommended by existing practice guidelines on dizziness. Two tests were included, although several practice guidelines question their diagnostic value. Two more tests were included that have never been recommended by practice guidelines on dizziness.</p> <p>Conclusion</p> <p>In this study we successfully combined empirical evidence with expert opinion for the development of a set of diagnostic tests for evaluating dizziness in elderly patients. This comprehensive set of tests will be evaluated in a cross-sectional diagnostic study.</p

Replication and Analysis of Ebbinghaus' Forgetting Curve.

We present a successful replication of Ebbinghaus' classic forgetting curve from 1880 based on the method of savings. One subject spent 70 hours learning lists and relearning them after 20 min, 1 hour, 9 hours, 1 day, 2 days, or 31 days. The results are similar to Ebbinghaus' original data. We analyze the effects of serial position on forgetting and investigate what mathematical equations present a good fit to the Ebbinghaus forgetting curve and its replications. We conclude that the Ebbinghaus forgetting curve has indeed been replicated and that it is not completely smooth but most probably shows a jump upwards starting at the 24 hour data point

Learning schedule during 2011–2012 for all lists, where labels in bold indicate when each of the lists 1 to 10 was first learned for each retention interval.

<p>Relearning times are not shown but can be derived by adding the retention interval (e.g., 6 days).</p

Synthesis, Complexation Chemistry and a Case of Self-Recognition of Chiral Phosphite Ligands

Reaction of (R)-(-)-1-phenyl-2,2,3-trimethylbutane-1,3-diol with PCl3 affords trans-(S)-2-chloro-4,4,5,5-tetramethyl-6-(R)-phenyl-1,3,2-dioxaphosphorinane, which couples smoothly with catechol, resorcinol, 2,2-dimethyl-1,3-propanediol and fluorenedimethanol to form the corresponding diphosphites. By three different methods (oxidation to phosphates, electrospray mass spectrometry with deuterium labelled samples, and NMR spectroscopic analysis of borane adducts) it was shown that on use of racemic materials a degree, less than absolute, of self-recognition is involved in the formation of the diphosphite obtained with catechol. No self-recognition is involved in the assembly of the product with resorcinol. Determination of the degree of self-recognition was made difficult by the identity of the NMR spectra of the meso and racemic forms of the diphosphites obtained from catechol.