Reliability in the Identification of Midbrain Dopamine Neurons

Brain regions typically contain intermixed subpopulations of neurons with different connectivity and neurotransmitters. This complicates identification of neuronal phenotypes in electrophysiological experiments without using direct detection of unique molecular markers. A prime example of this difficulty is the identification of dopamine (DA) neurons in the midbrain ventral tegmental area (VTA). Although immunocytochemistry (ICC) against tyrosine hydroxylase (TH) is widely used to identify DA neurons, a high false negative rate for TH ICC following ex vivo electrophysiology experiments was recently reported, calling into question the validity of comparing DA and non-DA VTA neurons based on post-hoc ICC. However, in whole cell recordings from randomly selected rat VTA neurons we have found that TH labeling is consistently detected in ∼55% of neurons even after long recording durations (range: 2.5–150 min). This is consistent with our prior anatomical finding that 55% of VTA neurons are TH(+). To directly estimate a false negative rate for our ICC method we recorded VTA neurons from mice in which EGFP production is driven by the TH promoter. All 12 EGFP(+) neurons recorded with a K-gluconate internal solution (as used in our rat recordings) were strongly labeled by TH ICC (recording duration 16.6±1.8 min). However, using recording electrodes with an internal solution with high Cl− concentration reduced the intensity of TH co-labeling, in some cases to background (recording duration 16.7±0.9 min; n = 10). Thus TH is a highly reliable molecular marker for DA neurons in VTA patch clamp recordings provided compatible microelectrode solutions are used

Monte Carlo studies of Mott scattering asymmetries from gold foils

We present the results of a series of model Monte Carlo calculations of the scattering of spin-polarized electrons from gold foil targets. Our calculations examine the behavior of the left-right scattering asymmetry A as a function of various parameters conventionally used in extrapolation of the left-right asymmetry to single atom and/or elastic scattering conditions. These parameters include target thickness, scattered count rate, and the maximum energy that an electron can have lost in the target and still be detected. Data are obtained at incident electron energies of 10–120 keV, with detector-subtended half-cone angles of 5°, 10°, and 20°, and gold foils of average thickness varying from 3 to 1000Å. Both elastic and inelastic electron scattering effects have been considered. Comparisons of our results are made with existing measurements and theoretical models. We make recommendations concerning extrapolation algorithms and for future experiments to test the present Mott scattering Monte Carlo model

Photoionization Broadening of the 1S-2S Transition in a Beam of Atomic Hydrogen

We consider the excitation dynamics of the two-photon \sts transition in a beam of atomic hydrogen by 243 nm laser radiation. Specifically, we study the impact of ionization damping on the transition line shape, caused by the possibility of ionization of the 2S level by the same laser field. Using a Monte-Carlo simulation, we calculate the line shape of the \sts transition for the experimental geometry used in the two latest absolute frequency measurements (M. Niering {\it et al.}, PRL 84, 5496 (2000) and M. Fischer {\it et al.}, PRL 92, 230802 (2004)). The calculated line shift and line width are in excellent agreement with the experimentally observed values. From this comparison we can verify the values of the dynamic Stark shift coefficient for the \sts transition for the first time on a level of 15%. We show that the ionization modifies the velocity distribution of the metastable atoms, the line shape of the \sts transition, and has an influence on the derivation of its absolute frequency.Comment: 10 pages, 5 figure

Rhythmic coma in children.

We describe a syndrome of rhythmic coma in children that consists of an invariant, nonreactive, diffuse cortical activity of a specific frequency, such as alpha, beta, spindle, or theta, recorded from a comatose child. We report 11 cases of children who were found to be in rhythmic coma during their acute illnesses. Their ages ranged from 2 to 15 years, and their diagnoses included encephalitis, head trauma, seizures, near drowning, brain tumors, stroke, and metabolic derangements. The specific frequency of the electroencephalographic pattern, ie, alpha, beta, spindle, or theta, did not influence the outcome. The clinical outcome appeared to depend on the primary disease process rather than the electroencephalographic finding. The prognosis of alpha-frequency rhythmic coma as well as of rhythmic coma in general was better in children than in adults. The pathophysiology in children may be similar, ie, the interruption of reticulothalamocortical pathways by metabolic or structural abnormalities, but the expression of this deafferentation may be more varied in the developing brain. Thus, we propose the term rhythmic coma as a unified concept for alpha, beta, spindle, and theta coma in children

Control and Simulation of a Deployable Entry Vehicle with Aerodynamic Control Surfaces

In this paper, we investigate the static stability of a deployable entry vehicle called the Lifting Nano-ADEPT and design a control system to follow bank angle, angle-of-attack, and sideslip guidance commands. The control design, based on linear quadratic regulator optimal techniques, utilizes aerodynamic control surfaces to track angle-of-attack, sideslip angle, and bank angle commands. We demonstrate, using a nonlinear simulation environment, that the controller is able to accurately track step commands that may come from a guidance algorithm

Prospects for Treatment of Latent HIV

Recent advances in antiretroviral therapy (ART) have drastically improved the quality of life for people with HIV infection. However, owing to the persistence of latent HIV in the presence of therapy, patients must remain on therapy indefinitely. Currently, the solution to the HIV pandemic rests on the prevention of new infections and many decades of ART for the steadily expanding number of people infected worldwide. ART is costly, requires ongoing medical care, and can have side effects, thereby preventing its universal availability. Therefore, to escape the ironic burdens of therapy, efforts have begun to develop treatments for latent HIV infection. Current approaches propose either complete eradication of infection or induction of a state of stringent control over viral replication without ART. This review will discuss these strategies in detail and their potential for clinical development

Contemplative Science: An Insider's Prospectus

This chapter describes the potential far‐reaching consequences of contemplative higher education for the fields of science and medicine