A 21-year record of vertically migrating subepilimnetic populations of Cryptomonas spp.

The vertical distribution and diel migration of Cryptomonas spp. were monitored continuously for 21 years in mesotrophic Cross Reservoir, northeast Kansas, USA. The movements of these motile algae were tracked on multiple dates during July–October of each year using in situ fluorometry and optical microscopy of Lugol’s iodine-preserved samples. Episodes of subepilimnetic diel vertical migration by Cryptomonas were detected and recorded on 221 different days between 1994 and 2014, with just 2 of these years (1998 and 2013) lacking any sampling events with deep peaks sufficiently large enough to track. Whenever a subepilimnetic layer of Cryptomonas was detectable, it was generally observed to ascend toward the bottom of the epilimnion beginning approximately at sunrise; to descend toward the lake bottom during the late afternoon and evening; and to remain as a deep-dwelling population until dawn of the following day. Moreover, there was high day-to-day consistency in the absolute water column depths at which the migrating algal cells would cease their ascending or descending movement. We believe this unique and remarkable dataset comprises the most detailed record of diel migratory behavior for any planktonic freshwater alga reported for a single freshwater lake

Examining Levels of Alignment Between School and Afterschool and Associations with Student Academic Achievement

In recent years, attention has been given to the academic impact of afterschool programs. Some schools collaborate with afterschool programs in an attempt to align the learning that occurs during the school day with the learning that occurs during afterschool hours, and thus maximize the potential to positively impact student academic achievement. However, very little research has sought to estimate the associations of alignment practices with academic achievement. This dissertation proposes a conceptual framework of alignment between school and afterschool programs that incorporates measuring academic resources, communication and a sense of partnership. It reviews the research on such practices, and synthesizes the work within the proposed framework. In the statistical study, survey data were collected from principals and afterschool staff at 78 schools across eleven school districts in Southern California. Respondents reported their perceptions of alignment between the school administrators and the afterschool program on three scales: academic resources, communication, and partnership. Highly aligned schools were defined as those in which both the principal and the afterschool staff reported high levels of alignment on all three scales. Misaligned schools were defined by an absolute difference in scores between principals and afterschool staff. Both measures were associated with relative changes in the average academic achievement of over 8,000 students who were included in the analysis sample. Results indicate a positive association between high alignment between principals and afterschool staff on academic achievement of students in both English Language Arts and Math, when compared with lower aligned sites. Significant negative associations were detected in Math when sites were misaligned. Findings document the need for more research in this under-studied area.  Advisor   Vandell, Deborah Lowe;  Committee members: Duncan, Greg; Farkas, George; University/institution - University of California, Irvine; Department:  Education - Ph.D

Intramuscular delivery of neural crest stem cell spheroids enhances neuromuscular regeneration after denervation injury.

BackgroundMuscle denervation from trauma and motor neuron disease causes disabling morbidities. A limiting step in functional recovery is the regeneration of neuromuscular junctions (NMJs) for reinnervation. Stem cells have the potential to promote these regenerative processes, but current approaches have limited success, and the optimal types of stem cells remain to be determined. Neural crest stem cells (NCSCs), as the developmental precursors of the peripheral nervous system, are uniquely advantageous, but the role of NCSCs in neuromuscular regeneration is not clear. Furthermore, a cell delivery approach that can maintain NCSC survival upon transplantation is critical.MethodsWe established a streamlined protocol to derive, isolate, and characterize functional p75+ NCSCs from human iPSCs without genome integration of reprogramming factors. To enhance survival rate upon delivery in vivo, NCSCs were centrifuged in microwell plates to form spheroids of desirable size by controlling suspension cell density. Human bone marrow mesenchymal stem cells (MSCs) were also studied for comparison. NCSC or MSC spheroids were injected into the gastrocnemius muscle with denervation injury, and the effects on NMJ formation and functional recovery were investigated. The spheroids were also co-cultured with engineered neuromuscular tissue to assess effects on NMJ formation in vitro.ResultsNCSCs cultured in spheroids displayed enhanced secretion of soluble factors involved in neuromuscular regeneration. Intramuscular transplantation of spheroids enabled long-term survival and retention of NCSCs, in contrast to the transplantation of single-cell suspensions. Furthermore, NCSC spheroids significantly improved functional recovery after four weeks as shown by gait analysis, electrophysiology, and the rate of NMJ innervation. MSC spheroids, on the other hand, had insignificant effect. In vitro co-culture of NCSC or MSC spheroids with engineered myotubes and motor neurons further evidenced improved innervated NMJ formation with NCSC spheroids.ConclusionsWe demonstrate that stem cell type is critical for neuromuscular regeneration and that NCSCs have a distinct advantage and therapeutic potential to promote reinnervation following peripheral nerve injury. Biophysical effects of spheroidal culture, in particular, enable long-term NCSC survival following in vivo delivery. Furthermore, synthetic neuromuscular tissue, or "tissues-on-a-chip," may offer a platform to evaluate stem cells for neuromuscular regeneration