Integration and differentiation of human embryonic stem cells transplanted to the chick embryo.

Human embryonic stem (ES) cells are pluripotent cells that can differentiate into a large array of cell types and, thus, hold promise for advancing our understanding of human embryology and for contributing to transplantation medicine. In this study, differentiation of human ES cells was examined in vivo by in ovo transplantation to organogenesis-stage embryos. Colonies of human ES cells were grafted into or in place of epithelial-stage somites of chick embryos of 1.5 to 2 days of development. The grafted human ES cells survived in the chick host and were identified by vital staining with carboxyfluorescein diacetate or use of a green fluorescent protein-expressing cells. Histologic analysis showed that human ES cells are easily distinguished from host cells by their larger, more intensely staining nuclei. Some grafted cells differentiated en masse into epithelia, whereas others migrated and mingled with host tissues, including the dorsal root ganglion. Colonies grafted directly adjacent to the host neural tube produced primarily structures with the morphology and molecular characteristics of neural rosettes. These structures contain differentiated neurons as shown by beta-3-tubulin and neurofilament expression in axons and cell bodies. Axons derived from the grafted cells penetrate the host nervous system, and host axons enter the structures derived from the graft. Our results show that human ES cells transplanted in ovo survive, divide, differentiate, and integrate with host tissues and that the host embryonic environment may modulate their differentiation. The chick embryo, therefore, may serve as an accessible and unique experimental system for the study of in vivo development of human ES cells.     

Evidence that dopamine in the nucleus accumbens is involved in the ability of rats to switch to cue-directed behaviours.

Recently we have reported that injections of d-amphetamine into the nucleus accumbens enhanced the number of switches to cue-directed behaviours without an effect on the number of switches to non-cue-directed behaviours in a swimming test. In the present study we investigated to what extent this effect is mediated via the dopaminergic system in the nucleus accumbens. For that purpose drugs selective for D1- and D2-receptors were studied in this swimming test. It was found that the selective D2-agonist LY 171 555 (50 ng/0.5 microliters) enhanced the number of different cue-directed behaviours. The selective D2-antagonist raclopride (50 ng/0.5 microliters) decreased it. Furthermore an ineffective dose of raclopride attenuated the effect of LY 171 555. Both the selective D1-antagonist SCH 23390 (400 ng/0.5 microliters) and the selective D1-agonist SKF 38393 (50-400 ng/0.5 microliters) decreased the number of different cue-directed behaviours. The effect induced by SCH 23390 could not be blocked by SKF 38393. Similarly the effect induced by SKF could not be attenuated by SCH 23390. These data point to a role for dopamine D2-receptors in the ability to switch to cue-directed behaviours. The present findings do not yet allow the conclusion that D1-receptors are involved.     

Comparison of 180° and 360° acquisition for myocardial perfusion SPECT with compensation for attenuation, detector response, and scatter: Monte Carlo and mathematical observer results

BACKGROUND: The optimal projection data acquisition strategy for myocardial perfusion (MP) single photon emission computed tomography (SPECT) remains controversial. METHODS: We compared MP SPECT using 180 degrees and 360 degrees projection data obtained with the same acquisition time, reconstructed either with filtered back projection (FBP) or the iterative ordered-subsets expectation maximization (OS-EM) algorithm with various combinations of attenuation, detector response, and scatter compensation using mathematical observers and a myocardial defect detection task. We used Monte Carlo-simulated projection data from a population of 3-dimensional nurbs-based cardiac-torso (NCAT) phantoms with ranges of variability in patient anatomy, organ uptake, defect location, defect size, and noise level based on clinical data. Projection data from 180 degrees and 360 degrees acquisitions were generated by assuming the same acquisition time. After iterative or FBP reconstruction, standard postprocessing methods were applied. For each acquisition and reconstruction method, we optimized the number of iterations and cut-off frequency of the Butterworth filter using the Channelized Hotelling Observer methodology. The optimum set of parameters was that which gave the maximum area under the curve. RESULTS: For both acquisition protocols, OS-EM with compensations provided better performance than FBP or OS-EM without compensation. For FBP, the optimized 180 degrees acquisition provided a statistically significant increase in AUC as compared with optimized 360 degrees acquisition. For OS-EM, the AUCs for 180 degrees were slightly larger than for 360 degrees acquisitions when comparing images reconstructed with the same compensations. However, the differences were smaller and not statistically significant. CONCLUSION: With optimized reconstruction and filtering parameters, 180 degrees acquisition provided a statistically significant improvement over 360 degrees acquisition for FBP reconstruction. However, for OS-EM the differences were small and not statistically significant.     

Policy determinants affecting the hunger millennium development goal

The possible effect of Government Consumption (a component of Gross Domestic Product (GDP)) on attainment of the hunger Millennium Development Goal (MDG1) was analyzed by evaluating the effect of macroeconomic, social, demographic and policy variables on average undernourished population. Eighty-four developing countries with data available on undernourished population were included in an ecological study. Regression models were applied to explore possible determinants of Undernourished between 1990 and 2004 and consequent achievement of the projected 2004 MDG1. In 2004, 1.4% of the overall undernourished population in the studied countries [70.16 million people] was in excess of the projected level required to meet MDG1. The multiple linear regression showed significant associations between Undernourished and poverty levels, the Gini Index, rural population and Government Consumption. The multiple logistic regression showed significant associations between achievement of projected 2004 MDG1 levels and Government Consumption and the Gini Index. The significant associations between Undernourished and Government Consumption suggest that the effects of GDP components on social conditions call for more thorough research and that policymakers such as governments and international financial institutions need to ensure that changes in distributive and redistributive policies do not negatively affect the possibility of achieving MDG1.     

Laparoscopic Medial-to-lateral Colon Dissection: How and Why

Laparoscopic colectomy is a difficult procedure with a long learning curve. We describe in this study our technique for right- and left-sided laparoscopic medial-to-lateral colectomy. The medial approach involves division of the vascular pedicle first, followed by mobilization of the mesentery toward the abdominal wall, and finally freeing of the colon along the white line of Toldt. This approach allows immediate identification of the plane between the mesocolon and the retroperitoneum and renders the dissection fast and safe. Our series of 50 consecutive laparoscopic colectomies supports this concept. We believe that surgeons familiar with this technique will have an important tool in their armamentarium to circumvent some of the challenges of laparoscopic colectomy.