Stage-specific expression of c-kit protein by murine hematopoietic progenitors

We have analyzed c-kit expression by hematopoietic progenitors from normal and 5-fluorouracil (5-FU)-treated mice by staining with monoclonal anti-c-kit antibody ACK-4. Marrow cells that were enriched for progenitors by a combination of metrizamide density separation and negative immunomagnetic selection with lineage-specific monoclonal antibodies (MoAbs) were separated into three populations based on the level of c-kit expression, c-kit(high), c-kit(low), and c-kit-. The majority of colony-forming cells from normal mice were in c-kit(high) population, whereas most of the progenitors from 5-FU-treated mice were in the c-kit(low) population. Optimal colony formation from c-kit(low) cells from 5-FU-treated mice required the interactions of at least two factors among interleukin-3 (IL-3), IL-11 and steel factor (SF) whereas colony formation from c-kit(high) cells of normal mice was supported well by IL-3 alone. Blast cells that were derived from 5-day culture of c-kit(low) post 5-FU cells were c-kit(high). These observations suggest that the primitive hematopoietic progenitors in cell cycle dormancy are c-kit(low) whereas actively cell cycling maturer progenitors are c- kit(high). Mature cells, with the exception of mast cells, derived from secondary culture of the c-kit(high) blast cells expressed little, if any, c-kit. These results are consistent with a model in which c-kit expression progresses from low levels on primitive, dormant multipotent progenitors to high levels on later, actively cycling progenitors, and finally, decreases to very low or undetectable levels on most mature blood cells, with the exception of mast cells.     

Integration of local inputs in visual cortex

In mammalian visual cortex, local connections are ubiquitous, extensively linking adjacent neurons of all types. In this study, optical maps of intrinsic signals and responses from single neurons were obtained from the same region of cat visual cortex while the effectiveness of the local cortical circuitry was altered by focally disinhibiting neurons within a column of known orientation preference. Maps of intrinsic signals indicated that local connections provide strong and functional subthreshold inputs to neighboring columns of other orientation preferences, altering the observed orientation preference to that of the disinhibited column. However, measuring the suprathreshold response using single-cell recordings revealed only mild changes of preferred orientation over the affected region. Because strongly tuned subthreshold inputs from cortex only marginally affect the tuning of a cortical cell's output, it is concluded that local cortical inputs are integrated weakly compared to geniculate inputs. Such circuitry potentially allows for the normalization of responses across a wide range of input activity through local averaging.      

Visibility of gallstone fragments at US and fluoroscopy: implications for monitoring gallstone lithotripsy

To assess the value of ultrasound (US), fluoroscopy, and spot radiography in the detection, counting, and measurement of gallstone fragments during lithotripsy, in vitro visibility studies were conducted on fragments from 20 stones. Fluoroscopic visibility was evaluated during and after lithotripsy on 185 fragments placed in an anthropomorphic phantom. Three US experiments were performed on the fragments to study the visibility of fragments as a function of size, the accuracy of the count with large numbers of fragments, and the ability of observers to detect and count fragments larger than both 4 mm and 5 mm. With fluoroscopy, fragment detection rates ranged from 20% (fragments larger than 2.5 mm) to 80% (fragments larger than 4.5 mm). With US, all fragments larger than 1.5 mm were detected, and US was significantly better than fluoroscopy and spot radiography for detection of fragments 2.5 mm or smaller. US was also more accurate than fluoroscopy (11% vs 59% error) in the assessment of the number of fragments. When fragments larger than 4 mm or 5 mm were being counted with US, 92% of the fragments were visualized. The results suggest that US is more accurate for monitoring gallstone lithotripsy than fluoroscopy or spot radiography.     

Treatment of stiff thoracic scoliosis by thoracoscopic anterior release combined with posterior instrumentation and fusion

Background  

Thoracoscopic anterior release has been shown that it can effectively improve spinal flexibility in animal and human cadaveric studies, and has been advocated for use in patients with scoliosis. This prospective case series aims to investigate the improvement of the spinal flexibility and the effectiveness in deformity correction by anterior thoracoscopic release and posterior spinal fusion.