Biomedical subjects

J E Tracy

Publications and source records attributed to J E Tracy.

5 recordsLinked to original sources

PubMed2002

Storage of platelets in additive solutions: a pilot in vitro study of the effects of potassium and magnesium.

BACKGROUND AND OBJECTIVES: Platelet additive solutions (PAS) have been shown to be suitable for extended platelet storage but have required the carryover of substantial (30%) amounts of plasma for success. Improving platelet quality by optimizing the composition of PAS may allow a reduction to be made in the amount of plasma carried over. Reducing the proportion of plasma carried over would facilitate some methods of viral inactivation and make available greater amounts of plasma for other needs. MATERIALS AND METHODS: Platelets from six pools of 25 buffy coat platelet units and five apheresis platelet units were aliquoted for storage in plasma, or converted to PAS units in either a specific additive solution (PAS-III), with 30% or 20% plasma, or a modification of PAS-III containing 5.0 mm potassium and 1.5 mm magnesium (PAS-IIIM), with 30% or 20% plasma. Units were stored at room temperature with agitation for 7 days with in vitro testing for biochemical, haematological and functional parameters. RESULTS: Storage of platelets in PAS-IIIM resulted in a reduced rate of glycolysis and better retention of pH, morphology score and ATP levels. Platelets initially showed less evidence of activation when stored in PAS-IIIM, with reduced P-selectin expression. Storage in PAS-IIIM with 20% (rather than the standard 30%) plasma appeared to result in the retention of in vitro properties, similarly to storage in standard PAS-III with 30% plasma. CONCLUSIONS: Storing platelets in an additive solution containing magnesium and potassium improves the functionality of the platelets, as measured by in vitro testing, and may allow a reduction of the amount of plasma required to be carried over to the final unit.

Adenosine Triphosphate↗

PubMed1996

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Journal Article↗

PubMed1996

Effect of closed chain exercise on quadriceps femoris peak torque and functional performance.

OBJECTIVE: To determine the effect of a 6-week leg press training program on quadriceps femoris peak torque and lower extremity functional performance. DESIGN AND SETTING: A 2 x 3 factorial design. A private university-based outpatient physical therapy clinic was used for testing. The university strength and conditioning center was used for training sessions. SUBJECTS: A volunteer sample of thirty nonathletic, collegeage females participated. All thirty subjects completed the study. MEASUREMENTS: Subjects were randomly assigned to either a control group (G(con)) or an exercise group that performed isotonic unilateral leg presses through either 0 to 60 degrees (G(60)) or 0 to 90 degrees (G(90)) of knee flexion. Subjects trained 3 days/wk for 6 weeks using the DAPRE technique. Pre and post isokinetic testing of the quadriceps femoris at 60 degrees /sec and hop tests for distance and time were measured. RESULTS: Both training groups showed significant pre-post increases (p < .05) for: concentric peak torque, eccentric peak torque, and hop test for distance. G\(60) showed a significant decrease in hop test for time values. Significant increases (p < .05) in eccentric peak torque was seen between training groups and the control group, concentric peak torque was significantly greater only in G(90) as compared to G(con), on. No significant differences were observed between G(60) and G(90) for any of the measured variables. There were no differences between the three groups for any of the functional hop test measurements. CONCLUSIONS: Unilateral leg press exercise performed through 0 to 90 degrees of knee flexion increases concentric and eccentric peak torque while training from 0 to 60 degrees improves eccentric torque. No changes in functional performance as measured by hop tests were seen in any groups. Transference between closed kinetic chain (CKC) exercise and open kinetic chain testing was supported, but not between CKC and functional performance testing.

Journal Article↗

PubMed1995

Kinematic and electromyographic analysis of elbow flexion during inertial exercise.

Inertial exercise protocols are currently used clinically to improve and restore normal muscle function even though research to substantiate their effectiveness cannot be cited in the literature. The purpose of this study was to compare simultaneous kinematic and electromyographic (EMG) data obtained from 12 subjects during elbow flexion on the Impulse Inertial Exercise System. Testing sessions consisted of inertial exercise performed using phasic and tonic techniques with loads of: a) 0 kg, b) 2.27 kg, c) 4.54 kg, d) 6.80 kg, e) 9.07 kg. Greater peak angular velocities, peak platform accelerations (change in velocity of platform during elbow flexion), mean and peak triceps brachii muscle EMG activity, and less range of motion were observed during phasic exercise. There was also a general trend for peak angular velocities and peak platform acceleration to increase as the load decreased. No significant difference in mean or peak EMG activity of the biceps brachii muscle was seen between techniques. Clinicians and athletic trainers using inertial exercise should consider both the exercise technique and load characteristics when designing protocols to meet the specific needs of patients.

Journal Article↗

PubMed1988

Comparison of selected pulse frequencies from two different electrical stimulators on blood flow in healthy subjects.

The purpose of this study was to measure the effects of selected frequencies from two different pulsed electrical stimulators on blood flow, blood pressure, and heart rate. Each of 30 healthy subjects attended 10 study sessions: 1 torque-testing session, 1 control session consisting of no electrical stimulation (ES), and 8 sessions of ES. All subjects received ES at an intensity sufficient to produce torque equal to 15% of the predetermined maximal voluntary contraction of their right quadriceps femoris muscle. The results of a multivariate analysis of variance showed that changes in blood flow during and after ES were dependent on pulse frequency but independent of stimulator type. Further analysis showed significant increases in blood flow with ES using 10, 20, and 50 pulses per second compared with 1 pulse per second. Inconsistent changes in blood pressure and heart rate were produced by ES. Based on the results of this study, effective clinical use of ES for promoting arterial blood flow to muscle would involve pulsed frequencies of 10 to 50 pulses per second.

Adult↗