Biomedical subjects

Chris McDonald

Publications and source records attributed to Chris McDonald.

4 recordsLinked to original sources

PubMed2006

Acetylenic carbon-13 chemical shift tensors for diphenylacetylene and (eta2-Diphenylacetylene)Pt(PPh3)2: a solid-state NMR and theoretical study.

The structure of (eta2-diphenylacetylene)Pt(PPh3) (2), as well as those of its dichloromethane and benzene solvates, is determined via X-ray crystallography. An investigation of the chemical shift (CS) tensors of the 13C-labeled carbons in Ph13C13CPh and (eta2-Ph13C13CPh)Pt(PPh3)2.(C6H6) is carried out via analysis of 13C NMR spectra from stationary solid samples. The principal components of the CS tensors as well as their orientations with respect to the 13C,13C internuclear vector are determined. DFT calculations of these CS tensors are in close agreement with the experimental values. For diphenylacetylene (tolane), the orientations and principal-component magnitudes of the alkynyl carbon CS tensors are comparable to those for other alkynyl carbons, although the CS tensor is not axially symmetric in this case. Coordination to platinum causes a change in the CS tensor orientation and a net increase in the isotropic chemical shift, resulting from a significant increase in two principal components (delta11 and delta33) while the third (delta22) decreases only slightly. The measured carbon CS tensors in the platinum complex bear a striking similarity to those of the alkenyl carbons in trans-Ph(H)C=C(H)Ph, and a short theoretical discussion of these observations is presented.

Journal Article↗

PubMed2005

CANSURV: A Windows program for population-based cancer survival analysis.

Patient survival is one of the most important measures of cancer patient care (the diagnosis and treatment of cancer). The optimal method for monitoring the progress of patient care across the full spectrum of provider settings is through the population-based study of cancer patient survival, which is only possible using data collected by population-based cancer registries. The probability of cure, "statistical cure", is defined for a cohort of cancer patients as the percent of patients whose annual death rate equals the death rate of general cancer-free population. Mixture cure models have been widely used to model failure time data. The models provide simultaneous estimates of the proportion of the patients cured from cancer and the distribution of the failure times for the uncured patients (latency distribution). CANSURV (CAN-cer SURVival) is a Windows software fitting both the standard survival models and the cure models to population-based cancer survival data. CANSURV can analyze both cause-specific survival data and, especially, relative survival data, which is the standard measure of net survival in population-based cancer studies. It can also fit parametric (cure) survival models to the individual data. The program is available at . The colorectal cancer survival data from the Surveillance, Epidemiology and End Results (SEER) program [Surveillance, Epidemiology and End Results Program, The Portable Survival System/Mainframe Survival System, National Cancer Institute, Bethesda, 1999.] of the National Cancer Institute, NIH is used to demonstrate the use of CANSURV program.

Computer Simulation↗

PubMed2004

Combining liquid chromatography with MALDI mass spectrometry using a heated droplet interface.

A novel interfacing technology is described to combine solution-based separation techniques such as liquid chromatography (LC) with matrix-assisted laser desorption ionization (MALDI) mass spectrometry. The interface includes a transfer tube having an inlet and an outlet, the inlet being adapted to accept the LC effluents and the outlet being adapted to form continuously replaced, hanging droplets of the liquid stream, and a MALDI sample plate mounted below the outlet of the transfer tube for collecting the droplets. The liquid stream in the transfer tube is heated to a temperature sufficient to cause partial evaporation of the carrier solvent from the hanging droplets. The droplets are dislodged to the MALDI plate, which is heated to above the boiling point of the carrier solvent to cause further evaporation of the carrier solvent from the collected droplets. It is found that analytes can be fractionated and deposited to a sample spot of 0.8 mm in diameter when a liquid flow rate of up to 50 microL/min and a fractionation interval of 1 min/spot are used. Flow rate of up to 200 microL/min can be used with a deposition sample spot of 2.4 mm in diameter on a commercial MALDI target. This heated droplet interface does not introduce sample loss, and the detection sensitivity of LC/MALDI is similar to that of standard MALDI, i.e., low femtomoles for peptide analysis with a microliter sample deposition. It is compatible with microbore and narrow-bore column separation, thus allowing the injection of a larger amount of sample for separation and analysis, compared to a capillary column LC/MALDI system. The detection dynamic range is shown to be in the order of 10(6) for peptide mixture analysis, which is 4 orders of magnitude greater than standard MALDI. The application of this interface for combining LC with MALDI MS/MS is demonstrated in the proteome analysis of water-soluable protein components of E. coli K12 extracts.

Chromatography, Liquid↗

PubMed2002

A comparison of once-daily tramadol with normal release tramadol in the treatment of pain in osteoarthritis.

OBJECTIVE: To compare the efficacy and tolerability of once daily (OD) tramadol tablets with normal release tramadol capsules (50 mg) taken 3 or 4 times daily in a multicenter, double blind, double dummy parallel study. METHODS: Patients with moderate to severe pain due to osteoarthritis (OA) were recruited from general practice. Following a titration period of a week, patients were assessed over one month for the analgesic efficacy and tolerability of the test medications. RESULTS: Both treatments were shown to be effective. There was no difference between treatments and both produced good pain control as shown by clinically relevant decreases from baseline pain scores, low escape medication use, and sleep disturbance. The efficacy of the OD tramadol over the 24 h dosing interval was confirmed by the low sleep disturbance, absence of "end of dose" effects in morning pain scores, and low escape medication use. Of the 279 patients recruited, 140 withdrew, mostly because of adverse events. The adverse event profiles were typical of opioids and were similar for both treatments. CONCLUSION: Tramadol OD was at least as effective and well tolerated as normal release tramadol in the management of OA pain. However, OD tramadol offers the advantage of a reduced dosing regimen, which is especially valuable in the elderly population.

Analgesics, Opioid↗