Ras controls melanocyte expansion during zebrafish fin stripe regeneration.

Regenerative medicine for complex tissues like limbs will require the provision or activation of precursors for different cell types, in the correct number, and with the appropriate instructions. These strategies can be guided by what is learned from spectacular events of natural limb or fin regeneration in urodele amphibians and teleost fish. Following zebrafish fin amputation, melanocyte stripes faithfully regenerate in tandem with complex fin structures. Distinct populations of melanocyte precursors emerge and differentiate to pigment regenerating fins, yet the regulation of their proliferation and patterning is incompletely understood. Here, we found that transgenic increases in active Ras dose-dependently hyperpigmented regenerating zebrafish fins. Lineage tracing and marker analysis indicated that increases in active Ras stimulated the in situ amplification of undifferentiated melanocyte precursors expressing mitfa and kita. Active Ras also hyperpigmented early fin regenerates of kita mutants, which are normally devoid of primary regeneration melanocytes, suppressing defects in precursor function and survival. By contrast, this protocol had no noticeable impact on pigmentation by secondary regulatory melanocyte precursors in late-stage kita regenerates. Our results provide evidence that Ras activity levels control the repopulation and expansion of adult melanocyte precursors after tissue loss, enabling the recovery of patterned melanocyte stripes during zebrafish appendage regeneration.

Phase II Archaeological Excavations at 99 Main Street, 18AP21 (Sign of the Whale), Annapolis, Maryland

Historical Annapolis Foundation (HAF) conducted terrestrial archaeological investigations at site 18AP21 in the city of Annapolis, Maryland. Excavations were carried out at this National Register site ostensibly as a Phase II project to evaluate the site and assess the need for further work. The site is at 99 Main Street in the center of downtown Annapolis, near the Annapolis waterfront. The project was carried out as part of the advanced work for the Annapolis History Center project, to be built in the adjoining buildings of 99 Main and 196 Green Streets. The buildings are the property of the Historic Annapolis Foundation and located in Maryland Research Unit 7. The excavations were undertaken by HAF, and funded by HAFF. The work was conducted for HAF and MHT, who holds an archaeological easement on the property. This preliminary phase of work included stratigraphic excavation of two testpit units. These two units revealed that the site of the existing 99 Main Street building was the location of three previous constructions. The current building at 99 Main Street, built in 1791, was preceded by an earlier brick dwelling, evidenced by a stout pier of bricks, which was attached to a wooden-sided structure that stood on a foundation of brick and stone. Ceramics indicate that these buildings date to the early-middle of the 18th century. A third structure of post-in-ground construction, evidenced by recovery of burned posts and wood fragments, likely existed prior to these, but evidence was scant. These excavations reveal that the site of 18AP21 holds potential for understanding Annapolis's early cultural developments, especially in the area of initial settlement and the origins of waterfront commerce. The assemblage of artifacts recovered includes a broad sample of common 18th century pottery such as creamware and Chinese export porcelain, and also includes some early colonial types such as tin-glazed earthenware and various red-bodied slipwares. The excavations do not provide conclusive evidence of the construction sequence. Consultation with MHT representatives indicates that further work at the site will likely be needed before modifications to the floor of the building can progress.

Oldest known cranium of a juvenile New World monkey (Early Miocene, Patagonia, Argentina): implications for the taxonomy and the molar eruption pattern of early platyrrhines.

A juvenile cranium of Homunculus patagonicus Ameghino, 1891a from the late Early Miocene of Santa Cruz Province (Argentina) provides the first evidence of developing cranial anatomy for any fossil platyrrhine. The specimen preserves the rostral part of the cranium with deciduous and permanent alveoli and teeth. The dental eruption sequence in the new specimen and a reassessment of eruption patterns in living and fossil platyrrhines suggest that the ancestral platyrrhine pattern of tooth replacement was for the permanent incisors to erupt before M(1), not an accelerated molar eruption (before the incisors) as recently proposed. Two genera and species of Santacrucian monkeys are now generally recognized: H. patagonicus Ameghino, 1891a and Killikaike blakei Tejedor et al., 2006. Taxonomic allocation of Santacrucian monkeys to these species encounters two obstacles: 1) the (now lost) holotype and a recently proposed neotype of H. patagonicus are mandibles from different localities and different geologic members of the Santa Cruz Formation, separated by approximately 0.7 million years, whereas the holotype of K. blakei is a rostral part of a cranium without a mandible; 2) no Santacrucian monkey with associated cranium and mandible has ever been found. Bearing in mind these uncertainties, our examination of the new specimen as well as other cranial specimens of Santacrucian monkeys establishes the overall dental and cranial similarity between the holotype of Killikaike blakei, adult cranial material previously referred to H. patagonicus, and the new juvenile specimen. This leads us to conclude that Killikaike blakei is a junior subjective synonym of H. patagonicus.

Characterization of immunoregulatory T lymphocytes in juvenile diabetes by monoclonal antibodies

info:eu-repo/semantics/nonPublished

A synthesis of large-scale patterns in the planktonic prey of larval and juvenile cod (Gadus morhua)

Data from 40 published studies of the diet composition of larval and juvenile cod (Gadus morhua) from around the northern North Atlantic were summarized to assess generic patterns in ontogenetic and regional variability in the key prey. The results showed that larvae at the northern edge of the latitudinal range of cod depend primarily on development stages of the copepod Calanus finmarchicus, whilst those at the southern edge depend on Para- and Pseudocalanus species. Juvenile cod preyed on a wider range of taxa than larvae, but euphausiids were the main target prey. Analysis of regional variations in the relative abundances of C. finmarchicus and Para/Pseudocalanus spp. in the plankton, as estimated by the continuous plankton recorder (CPR) surveys, showed a similar geographical pattern to the larval cod stomach contents. Comparison of CPR data from the 1960s and 70s with data from the 1990s showed that the boundary between C. finmarchicus and Para/Pseudocalanus spp. dominance has shifted northwards on both sides of the Atlantic, whilst the abundance of euphausiids in the southern cod stock regions has declined. The results are discussed in relation to regional differences in the response of cod stocks to climate variability.