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A 28 keV beam of Mg ions was extracted from a uranium carbide, proton-beam-irradiated target coupled to a laser ion source. The ion beam was nuclear-spin polarized by collinear optical pumping on the $^{2}\textit {S}_{1/2}$ - $^{2}\textit {P}_{1/2}$ transition at 280 nm. The polarization was preserved by an extended 1 mT guide field as the beam was transported via electrostatic bends into a 2.5 T longitudinal magnetic field. There the beam was implanted into a single crystal MgO target and the beta decay asymmetry was measured. Both hyperfine ground states were optically pumped with a single frequency light source, using segmentation of the beam energy, which boosted the polarization by approximately 50 % compared to pumping a single ground state. The total decay asymmetry of 0.06 and beam intensity were sufficient to provide a useful spin-1/2 beam for future BNMR experiments. A variant of the method was used previously to optically pump the full Doppler-broadened absorption profile of a beam of Be with a single-frequency light source. [ABSTRACT FROM AUTHOR]

We previously documented both the spontaneous acceleration of growth hormone (GH) and prolactin (PRL) production by GH cells during periffusion and the suppression of their production during plate culture. We here present the role played by medium flow itself in this differential behavior. Increasing rates of perifusion flow (pump rates of 1 to 5 ml/h, equivalent to chamber flow rates of 0.19 to 1.3 μl·min·mm of cross-sectional area) were associated with enhanced GH and PRL secretion. Flow rate-dependent basal hromone secretion rates were established quickly and were stable for the first 10 to 14 h of perifusion. The previously documented independent, spontaneous, and continuously accelerating production of both hormones that followed during the subsequent 40 (PRL) to 60 (GH) h of perifusion was also shown to be flow-rate related. Any time the rate of medium flow was changed within an experiment, the rate of hormone secretion was modulated. However, that modulation did not interrupt ongoing flow-associated acceleration of hormone production once the latter had begun. In addition, GH cell product(s) from one cell column reversibly inhibited secretion from cells in a downstream column. The inhibition did not occur when cells in the downstream column had been exposed to trypsin. Other work had suggested that neither GH, PRL, insulinlike growth factor-I, leucine, nor nutrient exhaustion were responsible for the effect. These data are consistent with autocrine-paracrine feedback regulation of GH cells by a secretory product(s). Feedback would thus provide a mechanism to effect flow-rate-dependent modulation of GH and PRL release, and to explain accelerating hormone production during perifusion. [ABSTRACT FROM AUTHOR]

In previous work we have shown that perifused GH cells exhibit spontaneously accelerating growth hormone (GH) and prolactin (PRL) secretory rates. This behavior contrasts with GH and PRL secretion rates that are decreasing or stable over the same 3-d period in static cell culture. We now report that GH cells maintained in serum-supplemented medium produce an autocrine-paracrine factor(s) which inhibits GH secretion in plate culture; PRL release is frequently reduced as well. The inhibitory effect of conditioned medium on GH secretion was concentration dependent, whereas PRL release was stimulated at low and inhibited at high concentrations over the same range. Extensive dialysis of conditioned medium using membranes with a molecular weight cut-off of 12 000-14 000 did not remove GH inhibition but produced a retentate that stimulated PRL secretion. Heat-inactivation of conditioned medium did not abolish inhibition of GH release but did remove the PRL-stimulatory effect. IGF-I added to fresh culture medium did not reproduce the GH-inhibitory effects of conditioned medium. We conclude that GH cell secretory behavior in perifusion and plate culture systems may be partially explained by the production of an autocrine-paracrine factor: its accumulation in plate culture inhibits GH and PRL secretion whereas its removal, by perifusing medium, allows GH and PRL secretion to accelerate. [ABSTRACT FROM AUTHOR]

The rates at which growth hormone (GH) and prolactin (PRL) are spontaneously secreted from a rat pituitary tumor cell line (GH) were significantly reduced when these cells were maintained in medium containing 2.5 μg/ml Fungizone (Fz). The reduction in hormone secretion was not immediately reversed by removal of Fz during perifusion, but after 3 wk in control medium, secretory rates approached the pre-Fz treatment levels. In plated cells, secretion of GH was reduced by Fz in a dose-dependent manner, whereas PRL secretion was significantly reduced only by the highest concentration (2.5 μg/ml) of Fz. We concluded that Fz is not an acceptable medium constituent for the long-term culture of GH cells. However, because its effects are reversible, its short-term use as a decontaminating agent might eliminate the necessity for reinitiating the culture of cells whose secretory behavior must be followed in long-term protocols. [ABSTRACT FROM AUTHOR]

GH cell secretory activity was studied in long-term perifusion to define previously reported spontaneous increases in growth hormone (GH) and prolactin production (PRL). Mechanically harvested cells (1×10/column) were perifused at 4 ml/h for 72 h. A basal period of variable duration (8 to 12 h), during which hormone secretion was stable, was followed by steadily increasing secretion rates. Changes in cell number were not sufficient to acount for increased jormone secretion rates: a) there was no significant change in cell count after 72 h (0.97±0.03×10; n=18); b) mean cell column DNA content increased 25.5% above the base value, whereas GH secretion rose 385% and PRL rose 178% ( n=5). Observed differences in the duration of the basal secretion period, the basal secretory rate, and the magnitude of secretory rate increase were associated with several variables: a) variablility within a subline was a function of passage number: GH secretion decreased and PRL secretion increased with subculture number; b) cells with identical lot and freeze numbers, but received at different times, behaved differently; c) the presence of an antifungal agent (nystatin) altered hormone secretion reproducibly. Conclusions: a) rates of GH and PRL secretion rise spontaneously in perifusion without a proportional increase in GH cell number; b) fluctuations in the rate of GH cell secretion of GH and PRL are not entirely random but are determined by several definable variables. [ABSTRACT FROM AUTHOR]

An analysis of cardiac arrhythmias in relation to left ventricular morphology and function was performed in 68 hypertensive patients 60 to 83 years of age. The study comprised Holter monitoring and echocardiography. Our results suggest that in elderly patients with primary arterial hypertension a correlation exists between left ventricular mass and the incidence of ventricular arrhythmias but not between left ventricular mass and supraventricular arrhythmias. [ABSTRACT FROM AUTHOR]