Rat Serum Contains a Developmentally Regulated Cholinergic Inducing Activity

Sympathetic neurons cultured in defined medium do not develop the ability to produce acetylcholine, as do neurons grown with serum supplementation (lacovitti, L., M. I. Johnson, T. H. Joh, and R. P. Bunge (1982) Neuroscience 7:2225–2239; Wolinsky, E. J., S. C. Landis, and P. H. Patterson (1985) J. Neurosci. 5: 1497–1508). The implication that rat serum contains cholinergic inducing activity is further explored here. Dependence of cholinergic induction on serum concentration is demonstrated, and the activity is shown to reside in a macromolecular fraction. Very little cholinergic inducing activity is present in serum obtained from animals younger than 9 postnatal days. This age dependence correlates with the time of transition from noradrenergic to cholinergic transmitter status by the sympathetic innervation of the rat sweat gland in vivo (Landis, S. C., and D. Keefe (1983) Dev. Biol. 98: 349–372)

Insulin Promotes Electrical Coupling between Cultured Sympathetic Neurons

Placing neurons in tissue culture is one way to study how environmental factors affect their differentiation. Replacement of serum- supplementation of the culture medium with defined ingredients extends the experimenter's control of the culture environment; however it also introduces additional potential influences. In this report, we confirm the observation of Higgins and Burton (Higgins, D., and H. Burton (1982) Neuroscience 7:2241–2253) of increased frequency of electrical coupling in serum-free compared to serum-supplemented cultures of rat sympathetic neurons. In addition, experiments were performed to determine whether this effect results from the removal of serum or from the addition of the defined medium components to the culture environment. The results of testing individual ingredients of the defined medium recipe adapted for use on sympathetic neurons (Bottenstein, J.E., and G. H. Sato (1979) Proc. Natl. Acad. Sci. U. S. A. 76:514–517) show that insulin is capable of inducing electrical coupling in serum-free cultures. Thus, the formation of electrical synapses by sympathetic neurons can be hormonally regulated

Expression of Noradrenergic and Cholinergic Traits by Sympathetic Neurons Cultured without Serum

The ability to vary systematically the neuronal environment is one advantage afforded by the use of cell culture. Replacement of serum, a variable and undefined medium supplement, with known ingredients allows even greater control of culture conditions. We have studied biochemical and morphological properties related to neurotransmitter metabolism of rat sympathetic neurons cultured in a modified defined medium. Neuronal survival, ultrastructure, and expression of noradrenergic properties appear similar in serum-free and serum-supplemented cultures: small granular vesicles characteristic of norepinephrine storage were observed in both types of culture, and tyrosine hydroxylase activity, conversion of dopamine to norepinephrine, catecholamine production, and storage capacity are equivalent in serum-free and serum-containing cultures. Several of these properties were not exhibited at high levels in previous formulations of this defined medium. Acetylcholine production, however, was about 10-fold lower in serum-free compared to serum-supplemented cultures, consistent with the findings of lacovitti et al. (lacovitti, L., M. I. Johnson, T. H. Joh, and R. P. Bunge (1982) Neuroscience 7:2225–2239). Acetylcholine production can be induced under serum-free conditions by a previously characterized cholinergic inducing factor from heart cell conditioned medium. This responsiveness to serum-free heart cell conditioned medium indicates that serum-free cultures retain plasticity with respect to transmitter status, despite expression of noradrenergic characteristics, unlike cultured neurons of which the noradrenergic transmitter status is maintained by chronic depolarization. Thus, sympathetic neurons survive, express numerous differentiated properties, and display a novel transmitter status under serum-free conditions

Progress Towards the Development of a Traveling Wave Direct Energy Converter for Aneutronic Fusion Propulsion Applications

A coordinated experimental and theory/simulation effort has been carried out to investigate the physics of the Traveling Wave Direct Energy Converter (TWDEC), a scheme that has been proposed in the past for the direct conversion into electricity of the kinetic energy of an ion beam generated from fusion reactions. This effort has been focused in particular on the TWDEC process in the high density beam regime, thus accounting for the ion beam expansion due to its space charge

On the informational content of wage offers

This article investigates signaling and screening roles of wage offers in a single-play matching model with two-sided unobservable characteristics. It generates the following predictions as matching equilibrium outcomes: (i) “good” jobs offer premia if “high-quality” worker population is large; (ii) “bad” jobs pay compensating differentials if the proportion of “good” jobs to “low-quality” workers is large; (iii) all firms may offer a pooling wage in markets dominated by “high-quality” workers and firms; or (iv) Gresham’s Law prevails: “good” types withdraw if “bad” types dominate the population. The screening/signaling motive thus has the potential of explaining a variety of wage patterns

3D MPRAGE improves classification of cortical lesions in multiple sclerosis.

BACKGROUND: Gray matter lesions are known to be common in multiple sclerosis (MS) and are suspected to play an important role in disease progression and clinical disability. A combination of magnetic resonance imaging (MRI) techniques, double-inversion recovery (DIR), and phase-sensitive inversion recovery (PSIR), has been used for detection and classification of cortical lesions. This study shows that high-resolution three-dimensional (3D) magnetization-prepared rapid acquisition with gradient echo (MPRAGE) improves the classification of cortical lesions by allowing more accurate anatomic localization of lesion morphology. METHODS: 11 patients with MS with previously identified cortical lesions were scanned using DIR, PSIR, and 3D MPRAGE. Lesions were identified on DIR and PSIR and classified as purely intracortical or mixed. MPRAGE images were then examined, and lesions were re-classified based on the new information. RESULTS: The high signal-to-noise ratio, fine anatomic detail, and clear gray-white matter tissue contrast seen in the MPRAGE images provided superior delineation of lesion borders and surrounding gray-white matter junction, improving classification accuracy. 119 lesions were identified as either intracortical or mixed on DIR/PSIR. In 89 cases, MPRAGE confirmed the classification by DIR/PSIR. In 30 cases, MPRAGE overturned the original classification. CONCLUSION: Improved classification of cortical lesions was realized by inclusion of high-spatial resolution 3D MPRAGE. This sequence provides unique detail on lesion morphology that is necessary for accurate classification

Adverse outcomes and correlates of change in the Short Physical Performance Battery over 36 months in the African American health project

BACKGROUND: The Short Physical Performance Battery (SPPB) is a well-established measure of lower body physical functioning in older persons but has not been adequately examined in African Americans or younger persons. Moreover, factors associated with changes in SPPB over time have not been reported. METHODS: A representative sample of 998 African Americans (49-65 years old at baseline) living in St. Louis, Missouri were followed for 36 months to examine the predictive validity of SPPB in this population and identify factors associated with changes in SPPB. SPPB was calibrated to this population, ranged from 0 (worst) to 12 (best), and required imputation for about 50% of scores. Adverse outcomes of baseline SPPB included death, nursing home placement, hospitalization, physician visits, incident basic and instrumental activity of daily living disabilities, and functional limitations. Changes in SPPB over 36 months were modeled. RESULTS: Adjusted for appropriate covariates, weighted appropriately, and using propensity scores to address potential selection bias, baseline SPPB scores were associated with all adverse outcomes except physician visits, and were marginally associated with hospitalization. Declines in SPPB scores were associated with low falls efficacy (b = -1.311), perceived income adequacy (-0.121), older age (-0.073 per year), poor vision (-0.754), diabetes mellitus (-0.565), refusal to report household income (1.48), ever had Medicaid insurance (-0.610), obesity (-0.437), hospitalization in the prior year (-0.521), and kidney disease (-.956). CONCLUSIONS: The effect of baseline SPPB on adverse outcomes in this late middle-age African American population confirms reports involving older, primarily white participants. Alleviating deterioration in lower body physical functioning guided by the associated covariates may avoid or delay multiple age-associated adverse outcomes

Rat Serum Contains a Developmentally Regulated Cholinergic Inducing Activity

Sympathetic neurons cultured in defined medium do not develop the ability to produce acetylcholine, as do neurons grown with serum supplementation (lacovitti, L., M. I. Johnson, T. H. Joh, and R. P. Bunge (1982) Neuroscience 7:2225–2239; Wolinsky, E. J., S. C. Landis, and P. H. Patterson (1985) J. Neurosci. 5: 1497–1508). The implication that rat serum contains cholinergic inducing activity is further explored here. Dependence of cholinergic induction on serum concentration is demonstrated, and the activity is shown to reside in a macromolecular fraction. Very little cholinergic inducing activity is present in serum obtained from animals younger than 9 postnatal days. This age dependence correlates with the time of transition from noradrenergic to cholinergic transmitter status by the sympathetic innervation of the rat sweat gland in vivo (Landis, S. C., and D. Keefe (1983) Dev. Biol. 98: 349–372)

Mars Sample Return and Flight Test of a Small Bimodal Nuclear Rocket and ISRU Plant

A combined Nuclear Thermal Rocket (NTR) flight test and Mars Sample Return mission (MSR) is explored as a means of "jump-starting" NTR development. Development of a small-scale engine with relevant fuel and performance could more affordably and quickly "pathfind" the way to larger scale engines. A flight test with subsequent inflight postirradiation evaluation may also be more affordable and expedient compared to ground testing and associated facilities and approvals. Mission trades and a reference scenario based upon a single expendable launch vehicle (ELV) are discussed. A novel "single stack" spacecraft/lander/ascent vehicle concept is described configured around a "top-mounted" downward firing NTR, reusable common tank, and "bottom-mount" bus, payload and landing gear. Requirements for a hypothetical NTR engine are described that would be capable of direct thermal propulsion with either hydrogen or methane propellant, and modest electrical power generation during cruise and Mars surface insitu resource utilization (ISRU) propellant production