The effects of gamma radiation on chondrogenic development in vitro

Gamma radiation (0.9-8.0 Gy) was used as a perturbing agent to study factors influencing in vitro chondrogenesis of embryonic chick limb bud cell culture. Chondrogenesis was measured using a number of criteria, including (1) cartilage nodule production, (2) spectrophotometric determination of the amount of bound Alcian blue dye, and (3) computer-assisted analysis of the spatial distribution (area) and density of Alcian blue present in individual micromass colonies. Gamma radiation inhibited both cell proliferation and chondrogenesis in a dose- and time-dependent fashion. Administration of benzamide caused a significant increase in cell proliferation at 0.9 and 2.7 Gy, and in chondrogenesis at all doses. Cartilage nodule production was affected during the first 2 days (prior to 48 h) of culture only, suggesting that chondrocytic commitment occurs during this period. Cultures irradiated at 48 and 72 h produced the same number of nodules as controls, but bound significantly less dye, presumably because of decreased cell numbers and/or cell synthesis products. Computer analysis of micromass colonies provided data similar to those collected spectrophotometrically, but displayed the advantages of (1) increased sensitivity to individual variations, (2) the ability to collect data sets without having to pool three or more colonies, and (3) long-term storage of raw images for later analysis.     

A novel assembly pipeline and functional annotations for targeted sequencing: A case study on the globally threatened Margaritiferidae (Bivalvia: Unionida)

The proliferation of genomic sequencing approaches has significantly impacted the field of phylogenetics. Target capture approaches provide a cost-effective, fast and easily applied strategy for phylogenetic inference of non-model organisms. However, several existing target capture processing pipelines are incapable of incorporating whole genome sequencing (WGS). Here, we develop a new pipeline for capture and de novo assembly of the targeted regions using whole genome re-sequencing reads. This new pipeline captured targeted loci accurately, and given its unbiased nature, can be used with any target capture probe set. Moreover, due to its low computational demand, this new pipeline may be ideal for users with limited resources and when high-coverage sequencing outputs are required. We demonstrate the utility of our approach by incorporating WGS data into the first comprehensive phylogenomic reconstruction of the freshwater mussel family Margaritiferidae. We also provide a catalogue of well-curated functional annotations of these previously uncharacterized freshwater mussel-specific target regions, representing a complementary tool for scrutinizing phylogenetic inferences while expanding future applications of the probe set.     

Notochordal development as influenced by the insecticide dicrotophos (Bidrin)

White Leghorn chicken embryos were treated at different ages with the insecticide dicrotophos to determine the time period of maximum effect upon notochordal development. Doses of insecticide ranging from 250 micrograms to 2.0 mg were injected into eggs at 8, 16, 24, 32, 40, 48, 72, or 96 hr of incubation and the eggs allowed to incubate for an additional 48 hr. Dicrotophos treatment caused dorsoventral and lateral folding of the notochord, with the cervical region being most severely affected. Although there was no apparent difference in dose responsiveness at any one age, there was an obvious age relationship. Notochordal responsiveness, expressed as both the number and severity of folds, was low among the 8- and 16-hr treated embryos, increased to a maximum in the 48-hr treatment group, and then declined among the older embryos. The time of maximum effect correlates closely with the time of sheath deposition and vacuolization of the notochord, but not to initial formation of the notochord from the mesoblast or later extracellular matrix production by sclerotome cells. It is proposed that dicrotophos interferes with some aspect of sheath formation. The pressure exerted by the vacuolization upon a structurally weakened sheath is thought to cause the observed folding.