Dynamic body acceleration as a proxy for human energy expenditure.

RATIONALE: The use of dynamic body acceleration (DBA) has previously been used as a proxy for energy expenditure (EE) in humans with promising results. Two forms of dynamic body acceleration have been used; overall dynamic body acceleration (ODBA) which comprises of the sum of acceleration data from three orthogonal axes and vectorial dynamic body acceleration (VeDBA) which constitutes of the vector of the acceleration data from three orthogonal axes. VeDBA is the mathematically correct calculation of body acceleration however there is strong biological rationale for the use of OBDA. This study sought to ascertain which DBA metric is the most accurate predictor of EE and in addition, how accelerometer orientation and placement, body anthropometries, body composition and aerobic capacity might influence these relationships. METHODS: Twenty-one voluntary participants [seventeen males, four females; age = 22.44 +/- 3.28 years, height = 1.75 +/- 0.07 m; weight = 70.66 +/- 9.78 kg] performed an incremental maximal exercise test on a motor driven treadmill [0% grade]. Volume of oxygen utilised per minute (VO2) was measured using an online gas analyser and body acceleration (g) measured simultaneously, via three tri-axial accelerometers; two attached to the upper back (one in a straight orientation and the other skewed 30°in each axis) and one attached to the right hip (in a straight orientation). Body composition data was collected using the skinfold method. RESULTS: Both ODBA and VeDBA were good proxies for VO2 with values exceeding 0.78, although ODBA accounted for slightly but significantly more of the variation in VO2 than did VeDBA (p = 0.002). There were no significant differences between ODBA and VeDBA in terms of the change in VO2 estimated by the acceleration data in a simulated situation of the accelerometer being mounted straight but becoming skewed. In terms of placement. ODBA and VeDBA values were significantly greater at the waist than the upper back (straight orientated device only) (p = 0.000) however when plotted against VO2 the differences between the hip and upper back became insignificant for both metrics. Fat-free mass, fat mass and age added significantly to the VO2 versus ODBA and VO2 versus VeDBA relationship in terms of r2. CONCLUSIONS: ODBA was found to be a marginally better proxy for VO2 than VeDBA although should only be used where researchers can guarantee a reasonably consistent device orientation. The upper back and hip are equally appropriate placements and should be chosen depending on the practicality. The ability of DBA to predict VO2 can be improved by adding additional variables to the regression equation, hi this case fat-free mass was the most significant covariate in terms of the improvement in r2

Specificity of triple helix formation

Triplex-forming oligonucleotides (TFOs) have been the subject of extensiveresearch in recent years. They have potential applications in many areas; such asgene-based therapies, site-directed mutation and as biochemical tools. However,triplex technology has been hampered by several problems, including low stabilitydue to electrostatic repulsion between strands. This thesis has investigatedcombinations of four methods for stabilising triplex DNA; these includeincorporation of the positively charged thymine analogues bis-amino-U andpropargylamino-dU in TFOs. Also modified TFO’s containing anthraquinonederivatives have been tested. Further, the free-intercalating agentnaphthylquinoline has been used to modulate TFO binding.A TFO containing six consecutive BAU molecules has previously beenshown to interact with non-target sites. The pH dependence of this TFO wasinvestigated. These experiments showed that considerably higher TFOconcentrations were needed to generate a footprint as the pH was increased. TheTFO had a high affinity for the exact template (tyrT) at pH 5.0 and 6.0 and showedsome evidence of binding even at 30 ?M at pH 7.0. These gels also showedevidence of the secondary binding seen in previous studies; this was considerablymore evident at pH 5.0, however, suggesting that the secondary binding may bemore sensitive to pH than the primary binding.Secondary binding sites for TFOs were examined by ‘RestrictionEndonuclease Protection, Selection and Amplification’ or REPSA. REPSA hasbeen used to select for DNA templates that are bound by the 9mer TFO containingsix bis-amino-U residues. Fourteen of the sequences which emerged fromREPSA were chosen for footprinting with TFOs containing BAU, propargylaminodUor T. The BAU-TFO produced clear footprints on all but one of the REPSAtemplates tested, indicating that the REPSA process was successful in selectingfor sequences which are bound by the TFO. Significantly higher concentrations ofthe P-TFO were required, and magnesium chloride and / or the triplex bindingligand naphthylquinoline were needed to promote binding. Despite the differencesin template sequence there does not appear to be a strong pattern in the bindingintensities of the TFOs on the different templates. However, all templates docontain a run of four to eight A’s. Surprisingly it appears from these data that theBAU TFO discriminates better than the P-TFO against non-exact binding sitesThe selectivity of TFOs containing anthraquinone modifications was alsoinvestigated. Anthraquinone intercalates between DNA bases in duplex DNA andcan be tethered to the end of a TFO to increase stability. The specificity of fiveTFOs with different anthraquinone modifications was examined by footprintingagainst fragments containing mismatches. A doubly modified TFO bound with thehighest affinity and was most tolerant of mismatches. Mismatches at the centre ofthe template had a lesser effect on binding affinity than mismatches at the 3’ end.The effect of a 3’ mismatch was also greater if the anthraquinone was at this end.The presence of an S-base at the 3’ end allowing intercalation of theanthraquinone at a YpR step increased the binding affinity on the exact template incomparison to TFO 3 which did not contain the S-base. The TFO containing the Sbase did not bind quite as well as the doubly modified TFO however

Heave (continuous line), sway (dotted line) and surge (dashed line) acceleration axes displayed graphically over one stride (from each leg) during walking (i) and running (ii).

<p>Heave (continuous line), sway (dotted line) and surge (dashed line) acceleration axes displayed graphically over one stride (from each leg) during walking (i) and running (ii).</p

An example plot of uptake against <i>ODBA</i> (black circles) and <i>VeDBA</i> (grey triangles) over the duration of the trial following removal of the points above the participant's anaerobic threshold.

<p>An example plot of uptake against <i>ODBA</i> (black circles) and <i>VeDBA</i> (grey triangles) over the duration of the trial following removal of the points above the participant's anaerobic threshold.</p

Relationship between mean <i>ODBA</i> and mean <i>VeDBA</i> (means taken for each running speed) for a test participant during a max test.

<p>Only data during the period when the participant did not exceed the ventilatory threshold (for definition see text) are included. as with all other participants, the relationship between <i>ODBA</i> and <i>VeDBA</i> was highly significant (<i>VeDBA</i> = 0.014+0.6418 <i>ODBA</i>, r² = 0.987, P<0.001).</p

Predicted difference between straight- and skew-mounted <i>ODBA</i> derived from recordings on a tri-axial accelerometer subjected to equal acceleration in the heave, surge and sway axes as a function of pitch, roll and yaw differences between straight and skew.

<p>Contour lines show 2.5% intervals.</p

Instantaneous <i>ODBA</i> plotted against <i>VeDBA</i> using all data from a participant recorded during a full max test.

<p>In this example, as with all other participants, the relationship between <i>ODBA</i> and <i>VeDBA</i> was highly significant (<i>VeDBA</i> = 0.014+0.6418 <i>ODBA</i>, r² = 0.987, P<0.001).</p

Overall relationships between and <i>ODBA</i> or <i>VeDBA</i> recorded for humans locomoting on a treadmill using an acceleration logger in a straight orientation or a skewed orientation.

<p>Overall relationships between and <i>ODBA</i> or <i>VeDBA</i> recorded for humans locomoting on a treadmill using an acceleration logger in a straight orientation or a skewed orientation.</p

Dynamic body accelerations (<i>ODBA</i> – circles, and <i>VeDBA</i> –crosses) from straight- versus skew-mounted accelerometers (for details see text).

<p>Each point denotes a mean value derived from a three-minute trial of a participant moving at one particular speed below the lactate threshold. Data from all participants are included.</p