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Biomedical subjects

D D Nansel

Publications and source records attributed to D D Nansel.

12 recordsLinked to original sources
PubMed1992

Effectiveness of upper versus lower cervical adjustments with respect to the amelioration of passive rotational versus lateral-flexion end-range asymmetries in otherwise asymptomatic subjects.

The effects of cervical spinal adjustments delivered bilaterally either to the upper cervical region (C2-C3) or to the lower cervical region (C6-C7), were compared in groups of asymptomatic subjects exhibiting goniometrically verified left-right rotational or left-right lateral-flexion passive end-range asymmetries of greater than 10 degrees. Goniometric evaluation both prior to, and again within 30 min following treatments revealed that lower cervical adjustments were far more effective for the amelioration of lateral-flexion asymmetries than were upper cervical ones, whereas upper cervical adjustments were found to be more effective for the amelioration of rotational asymmetries than those delivered to the lower cervical region. These results are consistent with the view that passive movement restriction exhibited along the rotational axis is attributable to factors related primarily to the upper cervical region, whereas restrictions of passive movement along the lateral axis are more attributable to factors related to the lower cervical region. Further support for the regional independence of these axis-specific relationships is provided by similar results obtained in groups of subjects who happened to exhibit both rotational as well as lateral-flexion asymmetries of greater than 10 degrees on the day of the experiment.

Adult↗
PubMed1991

The comparative assessment of paraspinal tissue compliance in asymptomatic female and male subjects in both prone and standing positions.

Segmental bilateral paraspinal tissue compliance measures were obtained from 50 male and 50 female asymptomatic subjects (vertebral segments C7-L5). Interexaminer concordance for the taking of the measure was found to be extremely high (r greater than .90). Additionally, test-retest measures obtained from the same subjects initially, and again 15 min or 2 wk later indicated fairly low short-term as well as long-term temporal variabilities for the measure. The greatest levels of variability were encountered at lumbar segments, particularly with 2 wk intervals between assessments, and when measures were obtained with subjects in the standing, rather than prone, position. Data generated by this study suggest that tissue compliance assessments may provide useful information with respect to the contractile state of the paraspinal musculature at various regions or segmental levels.

Adult↗
PubMed1990

Power spectral and microvector frequency analysis of dynamic standing foot force patterns in a normal male subject.

Power spectral and microvector frequency analyses of dynamic standing foot force patterns in a normal male subject were performed using a multiple-trial experimental protocol. Power spectral analysis of eight eyes-open vs. eyes-closed 50-sec trials revealed significant power increases in the 0.14 to 0.66 Hz range with eye closure, which were repeatable in trials performed on the same subject 2 wk later. Since power spectral differences are difficult to interpret biomechanically, a (micro)vector analysis of 1/20 sec changes in proportional weight transfer was employed. This methodology was able to reveal that foot force weight transfer exhibited a distinct preferred directionality, and that the eyes-closed condition was characterized by significant increases in both the occurrence and average magnitudes of these preferred microvectors.

Biomechanical Phenomena↗
PubMed1990

Analysis of dynamic standing foot force patterns in a normal male subject by characterization of microvector weight transfer sequences.

Previous foot forceplate analyses in our laboratory have shown that postural sway in a normal male subject induces net weight transfers (microvectors) which have preferred directionalities, and that eye closure is characterized by increases in both the occurrence and magnitudes of these preferred microvectors. The same data generated from 8 x 8 blocks of eyes-open and eyes-closed trials were reanalyzed to examine microvector temporal sequences (i.e., macrovectors). Macrovectors were defined by the number of successive microvectors occurring along the same general direction, (anterior, posterior, right or left). Results suggest that with eye-closure, proprioceptive systems are unable to maintain lateral sway deviations within eyes-open limits. This instability increases lateral macrovector durations while only marginally affecting sagittal macrovector durations.

Biomechanical Phenomena↗
PubMed1990

Normal paraspinal tissue compliance: the reliability of a new clinical and experimental instrument.

Test-retest reliability of a hand-held tissue compliance meter was evaluated in 20 normal subjects at four paraspinal locations to determine possible effects of probe response or other sources of variability on measurements taken 10 min later at exactly the same location. If tissue compliance, as measured by this instrument, is to be used in a pre-post context to evaluate treatment effects, caution is urged, since 26% of the sites were significantly (+/- 1.96 SD) different on 10 min retest though subjects remained supine and without intervention. In addition, since 85% of these normal subjects displayed at least one paraspinal compliance asymmetry large enough to qualify as pathological by Fischer's criteria, revision of these criteria may be appropriate, at least for these paraspinal locations.

Chiropractic↗
PubMed1989

Effect of unilateral spinal adjustments on goniometrically-assessed cervical lateral-flexion end-range asymmetries in otherwise asymptomatic subjects.

A triple blinded, multiple-measure, experimental protocol was employed in order to investigate the effectiveness of unilateral cervical adjustments on goniometrically assessed cervical lateral-flexion asymmetries. On pretest, subjects selected for the experiments exhibited mean left-right lateral-flexion differences of approximately 14 degrees. In subjects which either received no intervention, or had been subjected only to preliminary palpatory and set-up procedures but no thrust, asymmetry magnitudes were found to be unchanged on goniometric posttesting done 30-45 min later. However, in subjects which received lower cervical adjustments performed on the side of most restricted end-range, there was a dramatic reduction in asymmetry magnitudes. Furthermore, the adjustment procedure used in this investigation appeared to be relatively side-specific, since adjustments, when delivered to the less restricted side, were only marginally effective in ameliorating the asymmetries. Potential clinical relevance as well as the possible structural or physiological mechanisms responsible for the results obtained in the study are discussed.

Adult↗
PubMed1979

Subcellular localization of dopamine in the anterior pituitary gland of the rat: apparent association of dopamine with prolactin secretory granules.

The subcellular compartmentalization of endogenous dopamine in the anterior pituitary gland of the rat was investigated using continuous sucrose density gradient centrifugation. When anterior pituitary homogenates were layered on continuous sucrose density gradients (1.0--2.0 M) and centrifuged for 60 min at 40,000 X g, dopamine recovered from the gradients was associated with two sets of subcellular particles. The particles in one set were recovered near the top of the gradient, whereas those in the other set were recovered near the bottom of the gradient in the region where particles containing PRL were also found. In fact, these dense dopamine-containing particles could not be separated from those particles which contained PRL. These findings were suggestive that dopamine and PRL were present in the same particle, viz. the PRL secretory granule. This interpretation was further strengthened when it was established that the PRL-containing granules were separable on the gradient from granules which contained GH, LH, FSH, ACTH, and TSH. When [3H]dopamine was added to the solution in which the anterior lobes were homogenized, no radio-activity was found to be associated with the dense dopamine-containing particles. Also, the addition of a large excess of nonradiolabeled dopamine at the time of homogenization did not influence the amount of dopamine associated with the dense particles. Thus, the apparent association of dopamine with PRL secretory granules was not an artifact of the homogenization process per se. Therefore, it is concluded that an association exists between intracellular dopamine and the PRL secretory granule.

Adrenocorticotropic Hormone↗
PubMed1978

Prolonged infusion of rat luteinizing hormone alters its metabolic clearance pattern: indirect evidence for postsecretory mutation of luteinizing hormone.

Constant rate infusion/stop-entry experiments of varied duration were done with rat pituitary LH to test the possibility that the relatively slow disappearance of endogenous circulating LH after hypophysectomy/stop-entry in orchidectomized rats might be due to redistributive distortion consequent to a prolonged "packing" of the extravascular LH spaces in these animals. The findings indicated that prolongation of LH infusion did result in progressive flattening of the decay curve after stop-entry. After 1 h of infusion, constant rate infusion/stop-entry decay of LH was nearly as rapid as decay after simple pulse injection of the same extract. After 24 h of infusion, it was nearly as slow as after hypophysectomy/stop-entry. However, this change could not be explained solely on the basis of redistribution, because a similar difference was seen when disappearance of "infused" and "injected" pituitary LH were examined by pulse injection of sera collected from rats which had been given this LH by injection or prolonged infusion. Although variations in extravascular LH "packing" might have influenced LH disappearance in the donor rats, there was no opportunity for such variations to develop in the recipients. Although the mechanism(s) involved in this progressive change in the metabolic clearance characteristics of exogenous (extracted) circulating LH might simply be selective accumulation of the molecules most capable for surviving in the blood, other possibilities exist (e.g. actual mutation of circulating LH molecules). Whether endogenous (secreted) LH undergone similar changes during its sojourn in the circulation is not yet known but these findings suggest that postsecretory mechanisms could contribute to the apparent qualitative difference(s) between stored and circulating rat LH. Several implications of this new information have been discussed.

Animals↗
PubMed1977

Does androgen influence prolactin secretion?

In both intact and castrated male and female rats, administration of the A-ring reduced androgen, dihydrotestosterone (DHT), consistently failed to stimulate prolactin (PRL) secretion although it inhibited LH release and, in males, stimulated ventral prostate growth. In intact females, but not in the other types of rat, DHT actually suppressed PRL release. These findings do not support generalizations, based entirely on findings with testosterone, that both "androgens" and estrogens exert stimulatory actions on PRL secretion. The distinct stimulatory effects of testosterone and its esters on PRL secretion seem attributable, not to their androgenic actions per se, but to the ability of testosterone to form estrogenic metabolites. This ability does not appear to be shared by the "pure" androgen, DHT.

Animals↗
PubMedDate not supplied

Comparisons between active vs. passive end-range assessments in subjects exhibiting cervical range of motion asymmetries.

OBJECTIVE: To compare cervical range of motion values following active (nonpractitioner-assisted) vs. passive (practitioner-assisted) movement of the head to end range. DESIGN: Randomized, double-blind, within-subject comparisons. SETTING: Cervical Ergonomics Laboratory, Palmer College of Chiropractic-West, Sunnyvale, CA. SUBJECTS: Pain-free chiropractic college students, nearly evenly divided with respect to gender and ranging from 22-38 yr of age, were used in the study. Subjects exhibiting goniometrically determined cervical lateral-flexion or rotational passive end-range asymmetries of 10 degrees or greater were selected for experimentation. INTERVENTION: None. MAIN OUTCOME MEASURE: A goniometric (inclinometric) device was used for active and passive cervical end-range assessments. Active assessments were performed first, followed immediately by passive assessments in each subject. RESULTS: Results demonstrated that the magnitudes of end-range asymmetry detected following active assessment were only about half of those observed following passive assessments. Moreover, whereas active end-range values were about 5 degrees less than passive on the most restricted side of passive movement, active end-range values were about 10 degrees less than passive on the least restricted side of passive end range. CONCLUSIONS: These results are consistent with the notion that cortical influences mediating active movement are rather intolerant of asymmetric states involving end-range capability. This results in compensatory reductions in active movement on the side of greatest potential passive end range, thereby acting to preserve symmetry at the expense of overall range of motion. Results also suggest that measures obtained following active movement may be far more difficult to interpret than those obtained following passive assessments, particularly when information regarding possible asymmetry of end-range capability is considered to be of primary clinical and/or experimental importance.

Adult↗