The cell cycle program of polypeptide labeling in Chlamydomonas reinhardtii

The cell cycle program of polypeptide labeling in syndhronous cultures of wild-type Chlamydomonas reinhardtii was analyzed by pulse-labeling cells with 35SO4 = or [3H]arginine at different cell cycle stages. Nearly 100 labeled membrane and soluble polypeptides were resolved and studied using one-dimensional sodium dodecyl sulfate (SDS)- polyacrylamide gel electrophoresis. The labeling experiments produced the following results. (a) Total 35SO4 = and [3H]arginine incorporation rates varied independently throughout the cell cycle. 35SO4 = incorporation was highest in the mid-light phase, while [3H]arginine incorporation peaked in the dark phase just before cell division. (b) The relative labeling rate for 20 of 100 polypeptides showed significant fluctuations (3-12 fold) during the cell cycle. The remaining polypeptides were labeled at a rate commensurate with total 35SO4 = or [3H]arginine incorporation. The polypeptides that showed significant fluctuations in relative labeling rates served as markers to identify cell cycle stages. (c) The effects of illumination conditions on the apparent cell cycle stage-specific labeling of polypeptides were tested. Shifting light-grown asynchronous cells to the dark had an immediate and pronounced effect on the pattern of polypeptide labeling, but shifting dark-phase syndhronous cells to the light had little effect. The apparent cell cycle variations in the labeling of ribulose 1,5-biphosphate (RUBP)-carboxylase were strongly influenced by illumination effects. (d) Pulse-chase experiments with light-grown asynchronous cells revealed little turnover or inter- conversion of labeled polypeptides within one cell generation, meaning that major polypeptides, whether labeled in a stage-specific manner or not, do not appear transiently in the cell cycle of actively dividing, light-grown cells. The cell cycle program of labeling was used to analyze effects of a temperature-sensitive cycle blocked (cb) mutant. A synchronous culture of ts10001 was shifted to restrictive temperature before its block point to prevent it from dividing. The mutant continued its cell cycle program of polypeptide labeling for over a cell generation, despite its inability to divide

An Experimental Syntactic Study of Binding: A Case Study of Korean Long-Distance Anaphor caki

PACLIC 23 / City University of Hong Kong / 3-5 December 200

The Challenges and Potential of Nuclear Energy for Addressing Climate Change

The response to climate change and the stabilization of atmospheric greenhouse gas concentrations has major implications for the global energy system. Stabilization of atmospheric carbon dioxide (CO2) concentrations requires a peak and an indefinite decline of global CO2 emissions. Nuclear energy, along with other technologies, has the potential to contribute to the growing demand for energy without emitting CO2. Nuclear energy is of particular interest because of its global prevalence and its current significant contribution, nearly 20%, to the world’s electricity supply. We have investigated the value of nuclear energy in addressing climate change, and have explored the potential challenges for the rapid and large-scale expansion of nuclear energy as a response to climate change. The scope of this study is long-term and the modeling time frame extends out a century because the nature of nuclear energy and climate change dictate that perspective. Our results indicate that the value of the nuclear technology option for addressing climate change is denominated in trillions of dollars. Several-fold increases to the value of the nuclear option can be expected if there is limited availability of competing carbon-free technologies, particularly fossil-fuel based technologies that can capture and sequester carbon. Challenges for the expanded global use of nuclear energy include the global capacity for nuclear construction, proliferation, uranium availability, and waste disposal. While the economic costs of nuclear fuel and power are important, non-economic issues transcend the issues of costs. In this regard, advanced nuclear technologies and new vision for the global use of nuclear energy are important considerations for the future of nuclear power and climate change

The Growth of Fetal Human Sensory Ganglion Neurons in Culture: A Scanning Electron Microscopic Study

Sensory neurons of 8-week human fetal dorsal root ganglia were dissociated into single cells by trypsinization and cultured on coverslips for 4 months, in either serum-containing or serum-free chemically defined media. At different times the cultures were fixed and prepared for scanning electron microscopy. Fetal sensory neurons in culture regenerated axons within 24 hours which were characterized by axonal growth cones at their tips and the neuronal perikarya assumed spherical or a bonnet-like morphology

Nonlinear coupling of continuous variables at the single quantum level

We experimentally investigate nonlinear couplings between vibrational modes of strings of cold ions stored in linear ion traps. The nonlinearity is caused by the ions' Coulomb interaction and gives rise to a Kerr-type interaction Hamiltonian H = n_r*n_s, where n_r,n_s are phonon number operators of two interacting vibrational modes. We precisely measure the resulting oscillation frequency shift and observe a collapse and revival of the contrast in a Ramsey experiment. Implications for ion trap experiments aiming at high-fidelity quantum gate operations are discussed

Alterations in carotid baroreflex control of arterial blood pressure during the menstrual cycle in young women [abstract]

Limited studies have suggested that menstrual cycle variations in sex hormones may influence arterial baroreflex control of heart rate (HR) and sympathetic nerve activity, however, results are equivocal. In addition, the baroreflex control of blood pressure (BP) has not been directly examined as pharmacological perturbations were mainly used to assess baroreflex function

Solid-state metathesis reactions under pressure: A rapid route to crystalline gallium nitride

High pressure chemistry has traditionally involved applying pressure and increasing temperature until conditions become thermodynamically favorable for phase transitions or reactions to occur. Here, high pressure alone is used as a starting point for carrying out rapid, self-propagating metathesis reactions. By initiating chemical reactions under pressure, crystalline phases, such as gallium nitride, can be synthesized which are inaccessible when initiated from ambient conditions. The single-phase gallium nitride made by metathesis reactions under pressure displays significant photoluminescence intensity in the blue/ultraviolet region. The absence of size or surface-state effects in the photoluminescence spectra show that the crystallites are of micron dimensions. The narrow lines of the x-ray diffraction patterns and scanning electron microscopy confirm this conclusion. Brightly luminescent thin films can be readily grown using pulsed laser deposition