Biomedical subjects
Publications and source records attributed to R Peters.
As the population ages dementia is affecting an increasingly large proportion of society. The distinction between Alzheimer's disease and vascular dementia is becoming increasingly blurred and it has been suggested that cardiovascular risk factors such as hypertension may have an impact upon both diseases.
Illicit anabolic-androgenic steroid (AAS) use, for body building and body image purposes, is increasing internationally. This study describes the prevalence and symptoms of AAS use disorders obtained using a semi-structured interview among a mixed-gender sample of 100 current Australian users, that were recruited from a variety of sources. The median age of the sample was 27 years and 94% were male. The full range of DSM IV symptoms of AAS abuse and dependence were reported and over three quarters (78%) of the sample exhibited at least one symptom of abuse or dependence on AAS. A total of 23% of the participants qualified for a diagnosis of AAS dependence using DSM IV criteria and a further 25% met criteria for AAS abuse. There were no gender differences in AAS abuse or dependence diagnoses. The only variable related to an AAS substance use disorder was reporting the experience of AAS-related aggression, which may be a useful clinical indicator of the disorder.
By separating the first six linear and cyclic oligomers of polyamide-6 on a reversed-phase high-performance liquid chromatographic system after sandwich injection, quantitative determination of these oligomers becomes feasible. Low-wavelength UV detection of the different oligomers and selective post-column reaction detection of the linear oligomers with o-phthalic dicarboxaldehyde (OPA) and 3-mercaptopropionic acid (3-MPA) are discussed. A general methodology for quantification of oligomers in polymers was developed. It is demonstrated that the empirically determined group-equivalent absorption coefficients and quench factors are a convenient way of quantifying linear and cyclic oligomers of nylon-6. The overall long-term performance of the method was studied by monitoring a reference sample and the calibration factors of the linear and cyclic oligomers.
We report a method for reliable routine polymer sample introduction with minimal bias, a separation method of the first six linear and cyclic oligomers by liquid chromatography, quantification using group equivalents and long term method performance. Injecting a polymer sample in a mobile phase containing an aqueous non-solvent often results in blocked systems as the polymer precipitates in the connecting capillaries. In this first part we focus on a new injection technique, in which the dissolved polyamide is placed between two zones of formic acid, preventing the polymer to precipitate before it reaches the column. Development of this sandwich injection method makes direct injection of the polymer into an aqueous acetonitrile gradient feasible. The oligomeric polyamide recovery of this technique, extraction, dissolution/precipitation and direct injection on a hexafluoro-isopropanol (HFIP) gradient were compared. With the sandwich injection method the polymer remains on the column, slowly changing the stationary phase. The influence of this on resolution and retention was studied. Column stability allows sixty injections before cleaning or replacing the column is necessary.
Neurocutaneous melanosis (NCM) is a rare nonfamilial syndrome, characterised by large or numerous congenital pigmented nevi and excessive proliferation of melanin-containing cells in the leptomeninges. We report the MR findings in the brain and spine of a child with NCM who underwent neurosurgical treatment and was followed up for 8 years. The findings in this child (small hyperintense collections of melanocytes in both temporal lobes, mild meningeal enhancement along the spine and the development of an extensive subarachnoid CSF accumulation with cord compression and syringomyelia) are believed to be exceptionally rare.
Visualization and tracking of single fluorescent molecules is a recent development in optical microscopy holding great promise for the study of cell biological processes. However, all experimental strategies realized so far confined the observation to extremely thin interfacial layers. The detection and characterization of single molecules in three-dimensionally extended systems such as living cells has yet to be accomplished. We show, here, for the first time that single protein molecules can be visualized and tracked in three-dimensional (3D) samples at room temperature. Using a wide-field fluorescence microscope equipped with an Ar(+)-laser and a low-light-level CCD camera, single molecules of the green fluorescent protein (GFP) were detected in gels and viscous solutions at depths of up to approximately 10 microm from the interface. A time resolution of 5 ms was achieved by a high-speed framing mode. The two-dimensional localization accuracy was determined to be approximately 30 nm. The number of photons emitted by single GFP molecules before photodestruction was found to be < or = 4 * 10(5). Freely diffusing GFP molecules could be tracked over up to nine images acquired at a frame rate of approximately 80 Hz. From the trajectories, the diffusion coefficients of single GFP molecules were derived and found to agree well with expectation and microphotolysis measurements. Our results imply that the visualization and tracking of single molecules in living cells is possible.
Deprotonation of enantiomerically pure hydrazones and subsequent trapping with suitable electrophiles generates new stereogenic centers with excellent stereoselectivity. To liberate the original carbonyl functionality in the final products, it is necessary to cleave the hydrazone moiety. In recent years, many reagents have been developed to regenerate carbonyl compounds from the corresponding dialkylhydrazones which are compatible with a wide range of functionalities. This has allowed the use of hydrazones in the total synthesis of complex natural products. This Account is meant to be an overview of methods which are classified as oxidative, hydrolytic, and reductive cleavage procedures.
A new system--called SYBAR--is introduced, that employs digital video for registration of the movements of a patient while simultaneously recording electromyogram signals of relevant muscles and ground reaction forces (for the lower extremities in gait studies). All information is stored in a multimedia record, which can be viewed by the clinician with a simple user interface. This setup allows an integrated and more detailed view of the movement of the patient and related information (i.e., muscle physiology). It is used by clinicians to assess the causes of movement disorders in their patients. This paper describes the SYBAR system and focuses on the employed methods of data synchronization for both the time and the spatial domains. It is concluded that, although SYBAR was developed for clinical gait studies, the technology can be applied in all situations in which the relation between physiological signals and human or animal behavior is studied.
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Optical single-transporter recording, a recently established fluorescence microscopic method, was used to study the selective transport of proteins through single nuclear pore complexes (NPCs) of Xenopus oocytes. Recombinant proteins containing either a nuclear localization signal (import protein) or a nuclear export signal (export protein) were generated as transport substrates. To approximate in vivo conditions as closely as possible, a Xenopus egg extract was applied to the cytosolic side and a Xenopus oocyte nuclear extract to the nuclear side of the NPCs. It was found that protein transport through functionally isolated, "patched" NPCs depended on signal sequences, extracts, and metabolic energy, as in vivo. All NPCs were competent for both import and export. The transport direction was strictly determined by the transport signal, and at none of the conditions explored was the import protein exported or the export protein imported, even when the application sides of the extracts were reversed. The mean transport rates of the single NPC were approximately 2 dimers/s for the import protein and approximately 4 dimers/s for the export protein ( approximately 15 microM substrate concentration, 22-24 degrees C), in good agreement with in vivo rates estimated for mammalian cells by microinjection experiments. The study shows that optical single-transporter recording permits the analysis of membrane transport processes not previously accessible to single-transporter recording and thus provides additional possibilities for the elucidation of nucleocytoplasmic transport mechanisms.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.