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Biomedical subjects

C J Hardy

Publications and source records attributed to C J Hardy.

At least 55 records · Page 3Linked to original sources
PubMed1989

Neuroendocrine responses of type A individuals to exercise.

Ten Type A and 10 Type B individuals exercised for 20 minutes on a bicycle ergometer at 40%, 60%, and 80% of maximal capacity to determine if differences in neuroendocrine reactivity exist. Pre-exercise plasma concentrations of beta-endorphin and epinephrine were similar for Type As and Type Bs. Pre-exercise plasma levels of norepinephrine tended to be higher for the Type As (p less than 0.07). Post-exercise plasma epinephrine concentrations were similar for As and Bs for all trials. The 40% and 60% trials resulted in no differences in post-exercise norepinephrine and beta-endorphin levels for the Type As and Bs. Conversely, the 80% trials resulted in significantly greater norepinephrine and beta-endorphin concentrations for the Type As (p less than 0.05). Plasma serotonin levels at rest and during exercise were always lower for the Type As (p less than 0.05). These results suggest that our Type As had a greater neuroendocrine response to high-intensity exercise than our Type Bs. The greater reactivity and analgesia may allow the Type A person to suppress feelings of fatigue, thus enduring higher levels of exertion for longer periods of time.

Adult↗
PubMed1989

Comparative inhalation toxicity of technical chlordane in rats and monkeys.

Technical chlordane (1,2,4,5,6,7,8,8-octachloro-3a,4,7,7-tetrahydro-4,7-methanoinda ne) is used extensively for control of certain wood-boring insects. The present study was conducted to evaluate the inhalation toxicity of technical chlordane in rats and monkeys. Range-finding (28-d) and subchronic (90-d) inhalation studies with Wistar rats, and subchronic (90-d) inhalation studies with cynomolgus monkeys were conducted. In the range-finding study in rats, the threshold of toxicity for technical chlordane was approximately 5.8 micrograms/l. Among the observations made during the course of the 90-d study, in which technical chlordane was administered by inhalation to rats and monkeys at concentrations close to 0.1, 1.0, and 10 micrograms/l, the most significant were associated with alterations in the liver and were confined to rats only. However, in the rat, the effects on the liver were largely reversible during 90 d following cessation of administration of technical chlordane. The no-effect level of chlordane inhalation in rats appears to be between 0.1 and 1.0 microgram/l, while in monkeys the no-effect level is in excess of 10 micrograms/l. This study demonstrated that the monkey, a species closely related to humans, can tolerate relatively high chlordane concentrations without any adverse effects.

Administration, Inhalation↗
PubMed1989

Rapid, reliable in vivo assays of human phosphate metabolites by nuclear magnetic resonance.

This accurate, reliable, and fast method of assaying absolute concentrations of phosphate metabolites noninvasively in living tissue, including that of humans, combines 31P nuclear magnetic resonance (NMR) spectroscopy and 1H NMR imaging. The images are used to measure the areas of metabolite-bearing tissue in selected sections through the subject, and 31P spectra are acquired from the same section, together with a concentration reference located on the periphery. Metabolite concentrations are calculated from the ratios of areas and integrated signal intensities. Apparatus and protocol are designed to eliminate corrections due to magnetic field nonuniformities and NMR relaxation times. Mean (and SD) concentrations of adenosine triphosphate (ATP), phosphocreatine, and inorganic phosphate (Pi) measured in the brains of 15 normal adult human volunteers with a 1.5-T NMR system were 3.03 (0.49), 5.18 (0.89), and 1.5 (0.7) mmol per liter of wet tissue, respectively. Acquisition times of only a few minutes should facilitate metabolic studies of patients with disorders in limbs and brain, particularly those affecting entire organs.

Adenosine Triphosphate↗
PubMed1988

Rapid 31P spectroscopy on a 4-T whole-body system.

Initial 31P spectroscopy results from a 4-T whole-body system are reported. Localized spectra from the human head, liver, and calf were obtained using DRESS, slice-interleaved DRESS, and volume 3DFT spectroscopic imaging techniques. Substantial reductions in data acquisition times to 10 s-4 min were achieved relative to previous similar experiments at 1.5 T. Some gain in spectral resolution (as measured in ppm) was also realized in the head.

Head↗
PubMed1988

An examination of the life stress-injury relationship among noncontact sport participants.

This study was designed to determine if life stress is predictive of athletic injury among male and female participants in intercollegiate noncontact sports. The Athletic Life Experiences Survey (ALES) was administered to 86 athletes from the sports of baseball, softball, tennis, and track before the start of the season. After the administration of the ALES, injury frequency and severity were recorded for all practices and contests. The results indicated that total life change (TLC) and negative life change (NLC) were significant (p less than .05) predictors of athletic injury frequency. When partitioned by sex and sport, females and track athletes showed significant (p less than .05) predictive relationships, with TLC the significant predictor for females and object loss (OL) for track athletes. No significant predictive models were found for severity of injury. These results suggest that life stress is predictive of the frequency of injury among noncontact sport participants, particularly for track and female athletes.

Athletic Injuries↗
PubMed1988

Switched surface coil system for bilateral MR imaging.

A method is presented for acquiring magnetic resonance (MR) images in parallel from both members of a pair of organs, such as the temporomandibular joint (TMJ), with use of two surface coil receivers. Interleaved sagittal sections are broken into two groups, one on each side of the head, and the MR receiver is toggled between the two coils. The surface coil that is not receiving at a given time is decoupled from the other surface coil by the active gating of a diode blocking network located across the coil input. This method produces effective decoupling independent of coil loading and positioning and makes it possible to use the same surface coils already employed for single-coil MR reception. Clinical application in 95 patients (190 joints) with symptoms of internal derangement of the TMJ demonstrated a 24% average decrease in total patient examination time, even after the addition of coronal imaging to the procedure. In no case was there a sacrifice in diagnostic quality.

Humans↗
PubMed1987

Lipid and water suppression by selective 1H homonuclear polarization transfer.

A pulse sequence is presented which uses Polarization Transfer by a Selective Homonuclear Technique (POTSHOT) to retain all resonances, in phase, from a selected coupled spin system while suppressing all other peaks, from both coupled and noncoupled spins. This technique, which is a selective form of Homonuclear Polarization Transfer (HPT), has been used in a 1.5-T whole-body system to generate edited 1H lactate spectra from lactate/oil phantoms and from excised dog hearts.

Animals↗
PubMed1987

Exercise intensity-related responses of beta-endorphin and catecholamines.

Ten men and 10 women exercised on a bicycle ergometer for 20 min at 40, 60, and 80% maximal oxygen uptake (VO2max) to determine the relationship between plasma beta-endorphin, catecholamines, and exercise intensity. Compared to rest, plasma beta-endorphins were not significantly elevated during the 40 and 60% workloads (4.8 +/- 1.0 pmol.l-1 vs 3.8 +/- 0.7 and 6.3 +/- 0.9, respectively). In contrast, the 80% exercise significantly elevated endorphins to 16.1 +/- 4.0 pmol.l-1. Plasma norepinephrine concentrations were 0.30 +/- 0.04 ng.ml-1 at rest and increased with exercise intensity (40% = 0.60 +/- 0.05, 60% = 0.93 +/- 0.07, 80% = 2.00 +/- 0.14, VO2max = 2.55 +/- 0.14 ng.ml-1). Plasma epinephrine followed the same trend (rest = 0.07 +/- 0.01, 40% = 0.33 +/- 0.03, 60% = 0.49 +/- 0.02, 80% = 0.88 +/- 0.07, VO2max = 0.95 +/- 0.06 ng.ml-1). Norepinephrine was found to significantly correlate to endorphins (r = 0.499; P less than 0.02). Conversely, epinephrine was not correlated with beta-endorphin (r = 0.309; P greater than 0.05). The low correlation suggests a weak relationship between beta-endorphin and catecholamine responses during exercise. The results of this investigation suggest that the relationship between beta-endorphin and exercise intensity is curvilinear, with anaerobic activity producing the most significant endorphin response. It was also noted that the beta-endorphin response was not related to gender, but the amine response to exercise was gender-related, being greater for the men.

Adult↗
PubMed1986

The intrinsic signal-to-noise ratio in NMR imaging.

The fundamental limit for NMR imaging is set by an intrinsic signal-to-noise ratio (SNR) for a particular combination of rf antenna and imaging subjects. The intrinsic SNR is the signal from a small volume of material in the sample competing with electrical noise from thermally generated, random noise currents in the sample. The intrinsic SNR has been measured for a number of antenna-body section combinations at several different values of the static magnetic field and is proportional to B0. We have applied the intrinsic and system SNR to predict image SNR and have found satisfactory agreement with measurements on images. The relationship between SNR and pixel size is quite different in NMR than it is with imaging modalities using ionizing radiation, and indicates that the initial choice of pixel size is crucial in NMR. The analog of "contrast-detail-dose" plots for ionizing radiation imaging modalities is the "contrast-detail-time" plot in NMR, which should prove useful in choosing a suitable pixel array to visualize a particular anatomical detail for a given NMR receiving antenna.

Abdomen↗
PubMed1986

Surface-coil T1 images.

A method for producing calculated T1 images with high signal-to-noise ratio and good spatial resolution using surface coils is presented. Separate transmit and receive rf coils with electronic decoupling are employed to insure uniform B1 excitation. The sensitivity profile of the receiver coil is normalized out of the image by the T1 calculation. T1 values determined by this method show close agreement with previously reported values.

Extremities↗
PubMed1986

The relationship between selected psychological traits and fear of success in senior elite level wrestlers.

The present study sought to examine the relationship between selected psychological traits as measured by the Institute for Personality and Ability Testing (IPAT) 16 PF inventory and fear of success as measured by the Fear of Success Scale (FOSS). The subjects were 36 Senior elite wrestlers (age 20-25) who were invited to the Colorado Springs Olympic Training Center to prepare for an up-coming inter-national competition. A stepwise multiple regression analysis revealed that the following 16 PF factors predicted fear of success (p less than .05): IPAT-Q4, IPAT-L, IPAT-E, and IPAT-O. The multiple R was .75 and the R2 was 57.78%. Interpretation of the results suggest that while this sample of Senior elite wrestlers generally exhibit extremely low fear of success scores, athletes who are tense, frustrated, apprehensive, submissive, humble, and trusting tend to be more fearful of the consequences of success than those who are relaxed, unfrustrated, self-assured, assertive, competitive, and suspecting.

Achievement↗
PubMed1985

Orbital magnetic resonance imaging.

Magnetic resonance images of the eye and orbit performed with surface coils at 1.5 tesla showed anatomic details superior to those of conventional third- and fourth-generation computed tomography.

Anterior Chamber↗
PubMed1985

The medical case for an Australian national cyclotron facility.

Both a national cyclotron and a reactor are necessary to provide Australia with the complete range of radioisotopes. For the last 17 years, Australia has been well supplied with reactor radioisotopes by the Australian Atomic Energy Commission which provides a daily nationwide distribution service, but, to be self-sufficient, Australia also needs a national cyclotron. Many cyclotron radioisotopes are too short-lived for importation, and the demand can be met only by domestic production. Despite the availability of the necessary expertise and instrumentation, Australian patients are being denied a wide range of important clinical investigations because of the lack of suitable radioisotopes, for example, krypton-81m and iodine-123. An Australian medical cyclotron is overdue. Australia and New Zealand are the only developed countries that do not possess at least one medical cyclotron. The historical events in Australia's quest for a medical cyclotron are summarized, and the medical reasons why the writers believe that Australia should now acquire its own medical cyclotron are reviewed.

Australia↗
PubMed1985

Calculated T1 images derived from a partial saturation-inversion recovery pulse sequence with adiabatic fast passage.

Calculated T1 images of the head and abdomen have been obtained using an alternating partial saturation-inversion recovery pulse sequence. Timing parameters were adjusted to yield optimum T1 contrast-to-noise ratio for this sequence for the range of T1 studied. Adiabatic fast passage (AFP) was implemented for the nonselective inverting pulse, to reduce the sensitivity of the measurement to RF and static field inhomogeneity. A nonlinear frequency sweep was used to improve the efficiency of the AFP pulse. The effect on the T1 calculation of slice selection during the pi/2 pulses was also determined and corrected for in the image reconstruction algorithm. The T1's determined by this method show a standard deviation of less than 10%, and good agreement with the literature.

Abdomen↗
PubMed1985

Improved MR imaging of the orbit at 1.5 T with surface coils.

A method for obtaining localized high-resolution magnetic resonance (MR) images of the eye and orbit is demonstrated. The method uses modified surface receiver coils placed immediately adjacent to the anatomy to detect the MR signal. Surface coils provide enhanced sensitivity for imaging voxels close to the surface of the body while limiting the received patient-generated noise. The resulting improvement in signal-to-noise ratio allows for a reduction in the imaging voxel size to about 0.5 X 0.5 X 5 mm in scan times of 3.4-5 min. At this level of resolution, anatomic detail in the orbital region previously unobservable in MR images is seen.

Eye↗
PubMed1984

Uterine stimulant action of some 16-phenoxy analogues of (+)-11-deoxyprostaglandin E1.

Some (+)-11-deoxy-16-phenoxyprostaglandin E1 analogues have been evaluated as uterine stimulants in the anaesthetised pregnant rat. Gastrointestinal side effects, assessed by the antagonism of morphine-induced constipation in the mouse, were relatively low with some of these compounds, six of which had a much more favourable relative selectivity than 16,16-dimethyl-PGE2 methyl ester.

Alprostadil↗
PubMed1984

Thermodynamic properties of purple membrane.

We measured the density, expansivity, specific heat at constant pressure, and sound velocity of suspensions of purple membrane from Halobacterium halobium and their constituent buffers. From these quantities we calculated the apparent values for the density, expansivity, adiabatic compressibility, isothermal compressibility, specific heat at constant pressure, and specific heat at constant volume for the purple membrane. These results are discussed with respect to previously reported measurements on globular proteins and lipids. Our data suggest a simple additive model in which the protein and lipid molecules expand and compress independently of each other. However, this simple model seems to fail to describe the specific heat data. Our compressibility data suggest that bacteriorhodopsin in native purple membrane binds less water than many globular proteins in neutral aqueous solution, a finding consistent with the lipid surround of bacteriorhodopsin in purple membrane.

Bacteriorhodopsins↗