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Publications and source records attributed to D D Nansel.
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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.
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.
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.
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.