Biomedical subjects
David J Smith
Publications and source records attributed to David J Smith.
Performance evaluation of swimmers: scientific tools.
The purpose of this article is to provide a critical commentary of the physiological and psychological tools used in the evaluation of swimmers. The first-level evaluation should be the competitive performance itself, since it is at this juncture that all elements interplay and provide the 'highest form' of assessment. Competition video analysis of major swimming events has progressed to the point where it has become an indispensable tool for coaches, athletes, sport scientists, equipment manufacturers, and even the media. The breakdown of each swimming performance at the individual level to its constituent parts allows for comparison with the predicted or sought after execution, as well as allowing for comparison with identified world competition levels. The use of other 'on-going' monitoring protocols to evaluate training efficacy typically involves criterion 'effort' swims and specific training sets where certain aspects are scrutinised in depth. Physiological parameters that are often examined alongside swimming speed and technical aspects include oxygen uptake, heart rate, blood lactate concentration, blood lactate accumulation and clearance rates. Simple and more complex procedures are available for in-training examination of technical issues. Strength and power may be quantified via several modalities although, typically, tethered swimming and dry-land isokinetic devices are used. The availability of a 'swimming flume' does afford coaches and sport scientists a higher degree of flexibility in the type of monitoring and evaluation that can be undertaken. There is convincing evidence that athletes can be distinguished on the basis of their psychological skills and emotional competencies and that these differences become further accentuated as the athlete improves. No matter what test format is used (physiological, biomechanical or psychological), similar criteria of validity must be ensured so that the test provides useful and associative information concerning current or future performance. The practical worth of any proposed testing or monitoring protocol should be carefully evaluated. In addition, the developmental stage of the athlete(s) in question should be reflected in the testing/monitoring programme. Finally, increasing technological innovations will bring to the pool deck or dry-land training area simple, fast and advanced diagnostic tools, particularly in the areas of blood-borne markers of training response and neuromuscular excitability.
Ketamine analgesia is not related to an opiate action in the periaqueductal gray region of the rat brain.
Ketamine is an injectable anesthetic agent that has been shown to interact as an agonist at opiate receptors. In addition, its antinociceptive action in rats is antagonized by the narcotic receptor antagonist naloxone. Thus it was assumed that the anesthetic may activate the pain inhibitory pathway, originating in the periaqueductal gray (PAG) and descending into the spinal cord, in a manner similar to that of narcotics like morphine. In the present study, it was verified that the systemic administration of naloxone (3 mg/kg i.p.) antagonized the elevation in tail-flick latency produced by an anesthetic dose of ketamine (160 mg/kg i.p.), but did not alter the duration of anesthesia (defined as duration of the loss of the righting reflex). However, when naloxone (3 micrograms/0.5 microliter/30 sec) was given by microinjection into the PAG it was found to be ineffective against the ketamine-induced elevation of the tail-flick latency. In contrast, the microinjection of the antagonist significantly attenuated (halved) the elevated latency in response to systemically administered morphine (4 mg/kg s.c.). It was also shown that ketamine was unable to elicit an increase in the latency of the tail-flick reflex when administered directly into the PAG over a wide range (0.10-100 micrograms) of doses. On the other hand, a local anesthetic-like effect of ketamine, known to occur when the drug is used in high concentration, was observed when doses exceeding 0.1 microgram were injected into the PAG. This action interfered with opiate actions in the PAG and made data from the microinjection studies difficult to interpret. The descending, pain inhibitory neuronal system originating in the PAG does not appear to participate in the antinociceptive action of ketamine measured by the tail-flick reflex. Perhaps the drug's effects are associated with alternative opiate mechanisms and/or opiate receptor subtypes not present on the cells of origin of the descending nerves within the PAG.
The involvement of opiate and monoaminergic neuronal systems in the analgesic effects of ketamine.
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Tissue transglutaminase interacts with protein kinase A anchor protein 13 in prostate cancer.
We have previously described that tissue transglutaminase (tTG) is a high level phenotypic biomarker in prostate cancer, which is down regulated in prostate cancer and surrounding premalignant field compared to benign prostate glands. To understand the function of tTG in prostate cancer, we sought to identify proteins that interact with the transglutaminase moiety of tTG using a human prostate cancer complementary deoxyribonucleic acid library in a Yeast 2-Hybrid system. The Yeast 2-Hybrid experiments identified a strong and novel interaction between the transglutaminase moiety and protein kinase A anchor protein 13 (AKAP13), which was quantified by beta-galactosidase assay, confirmed in vitro by immunoprecipitation experiments using PC3 prostate cancer cell lysates, and in vivo colocalization was confirmed by immunofluorescence studies in PC3 cells. Because AKAP plays a major role in protein kinase A and Rho protein mediated signaling, functional studies are underway to elucidate the significance of tTG-AKAP13 interaction in prostate cancer.
Semiconductor dopant profiling by off-axis electron holography.
Silicon wafers with a complex but known dopant profile were used to explore possible methods for improving the reliability of off-axis electron holography for quantitative determination of electrostatic potential profiles in doped semiconductor devices. The variability of results from nominally identical structures was attributed to local charging and associated external fields, forcing the development of a more robust approach to hologram analysis that incorporated an additional phase correction factor rather than rely on vacuum for phase flattening. Consistent results in close agreement with simulated profiles based on measured dopant distributions could then be obtained. Carbon coating was shown to be effective in reducing accumulation of charge caused by emission of secondary electrons. Overall, this work demonstrates that reliable potential profiles from unbiased samples should be obtainable on a routine basis provided that regions suitable for flattening of the phase profile can be identified.
Microarray analysis of differential gene expression in androgen independent prostate cancer using a metastatic human prostate cancer cell line model.
Progression to androgen independence (AI) leading to uncontrolled cell growth is the main cause of death in prostate cancer. While almost all patients with metastatic prostate cancer will initially respond to anti-androgen treatments, the majority will fail hormonal treatments in less than 2 yrs. Both genetic and epigenetic alterations in gene expression contribute significantly to the development of AI. To investigate this we have used an in vitro cell line model of AI prostate cancer from which we have identified a number of differentially expressed genes associated with progression to AI in prostate cancer. We used an in vitro cell line model of AI prostate cancer, to study differential gene expression using cDNA microarray analysis and corroborated the microarray results with Ribonuclease Protection Assay (RPA). Approximately 4480 out of 7075 (63.3%) cDNA cloned genes were differentially expressed, of which, 6 genes were differentially expressed by at least fivefold. RPA was used to corroborate the microarray results for the five most highly differentially expressed genes. Using an in vitro cell line model and microarray analysis we have identified a number of candidate genes for further investigation in AI prostate cancer.
Ergovaline movement across Caco-2 cells.
Ergovaline's role in the direct causation of fescue toxicosis first requires establishment of its dietary absorption. Therefore, ergovaline movement across human intestinal cells was assessed using Caco-2 cells derived from human colon carcinoma. A pre-equilibrated mixture of ergovaline/ergovalinine (60:40 ratio of isomers) was added to the apical compartment, and isomer movements were assessed by high-performance liquid chromatography (HPLC) of extracted media (initial pre-isomerized ergovaline concentrations of 6 and 22 microM, two doses). Mathematical models for ergot alkaloid movement were developed. Rates of movement were not different for the isomers. In the absence of cells, basal accumulation of isomers was essentially linear for 3 h regardless of loading concentration, after which basal accumulation of ergovaline/ergovalinine plateaued. Rates of ergovaline/ergovalinine movement in the presence of cells slowed to about 25% the rate of movement in the absence of cells (22 microM, kt = 0.0133 no cells, 0.0036 with cells, P < 0.05). Mass transfer rate was 7.5 ng x cm(-2) x min(-1) and was similar to that reported for ergovaline using a parabiotic chamber with sheep omasum. After 6 h in the presence of cells, approximately 25 and 40% of the total ergovaline/ergovalinine administered had accumulated in the basal compartment for 6.6 and 22 microM treatments, respectively. Ergovaline and its naturally occurring isomer, ergovalinine, readily crossed intestinal cells intact and at similar rates. Either isomer, or a combination of both, could be involved in the pathogenesis of fescue toxicosis at sites distal to the intestine.
Immunoaffinity column as sample cleanup method for determination of the beta-adrenergic agonist ractopamine and its metabolites.
A monoclonal antibody-based immunoaffinity column (RAC-IAC) was developed as a cleanup method for the determination of ractopamine and ractopamine glucuronides. [14C]Ractopamine (5 microg) and [14C]ractopamine glucuronides (5 microg) were fortified into 10 mL cattle urine, and loaded onto an RAC-IAC (5 mg IgG/mL) column. The column was washed and the bound analytes were eluted. In the initial loading and washing, 22% of the radioactivity was washed off and the subsequent elution step recovered 78%. A blank column prepared from nonspecific IgG retained <10% of the radioactivity. The RAC-IACs were damaged by high methanol concentrations, preventing reuse. Elution of the analytes with 50mM glycine buffer, pH 2.8, prevented damage, and the columns could be reused at least 20 times with no change in performance. They were stored >3 months in phosphate-buffered saline with 0.02% sodium azide at 4 degrees C. The method was used with fortified cattle muscle, liver, and kidney samples with recoveries of 82.1+/-7.6, 87.8+/-1.9, and 92.5+/-0.4%, respectively (n = 3). Similar studies with sheep muscle, liver, and kidney samples gave recoveries of 91.8+/-0.2, 91.7+/-0.3, and 92.3+/-0.3, respectively (n = 3). Liver and kidney samples were diluted to prevent column plugging, but all of the eluants were suitable for liquid chromatography analysis. This IAC is a selective, efficient, and economical cleanup method in a variety of matrixes for ractopamine determination.