An aneuploid mouse strain carrying human chromosome 21 with Down syndrome phenotypes

Aneuploidies are common chromosomal defects that result in growth and developmental deficits and high levels of lethality in humans. To gain insight into the biology of aneuploidies, we manipulated mouse embryonic stem cells and generated a trans-species aneuploid mouse line that stably transmits a freely segregating, almost complete human chromosome 21 (Hsa21). This "transchromosomic" mouse line, Tc1, is a model of trisomy 21, which manifests as Down syndrome (DS) in humans, and has phenotypic alterations in behavior, synaptic plasticity, cerebellar neuronal number, heart development, and mandible size that relate to human DS. Transchromosomic mouse lines such as Tc1 may represent useful genetic tools for dissecting other human aneuploidies.     

Use of Standard or Modified Plant-Derived Lipids as Alternatives to Fish Oil in Feeds for Juvenile Nile Tilapia

In support of developing sustainable aquafeeds, production performance and fillet fatty acid profile were assessed in juvenile Nile tilapia (0.61 ± 0.0 g/fish mean ± SE) raised for 16 weeks on diets containing fish oil or 50:50 blends of fish and plant-derived lipids. Standard, low 18:3n-3, or saturated fatty acid (SFA)-enriched soybean oils, palm oil, or low 18:3n-3 canola oil may be used to partially spare fish oil in feeds for Nile tilapia without impairing production performance, though use of hydrogenated soybean oil appears to impair growth and conversion efficiency. Of the plant lipids evaluated, palm and SFA-enriched soybean oil appear to be the best alternatives in terms of maintaining fillet long-chain polyunsaturated fatty acid content and the nutritional value of tilapia fillets.     

The Effect of Temperature on Production of Gonads by the Sea Urchin Strongylocentrotus franciscanus Fed Natural and Prepared Diets

Strongylocentrotus franciscanus (248 ± 76 g wet body weight, mean and standard deviation) were maintained in the laboratory at 12.9 and 16.1 C and fed either Nereocystis luetkeana or a prepared feed for 4 mo (July through October). The size and histological condition of the gonads of an initial sample, the experimental animals, and a sample from the commercial fishery were evaluated. The gonad index of experimental S. franciscanus increased from an initial 3.4%± 1.4 to 19.2%± 3.3 (mean and standard deviation) for the four treatments. The feeding rate was greater for individuals fed N. luetkeana and for both foods at the higher temperature. Gonad production was not significantly different among the experimental treatments, indicating the prepared feed was nutritionally superior to the algal diet and an increase in catabolism at the higher temperature balanced the increase in food intake. Histological preparations determined the urchin gonads developed from an initial spent condition to the premature stage for both experimental and fishery samples, indicating neither food or temperature affected gametogenesis.     

Tissue-specific and ectopic expression of genes introduced into transgenic mice by retroviruses

Recombinant retroviruses containing the complete genomic human beta globin gene (under the control of its own promoter) and the bacterial neomycin phosphotransferase gene (under the control of the normal or enhancerless viral promoter) were used to derive transgenic mouse strains by infection of preimplantation embryos. Expression of the beta globin gene in hematopoietic tissues was observed in all transgenic strains. In addition, one strain showed ectopic expression of beta globin in the same tissues that also expressed high levels of RNA from the viral promoter. It is likely that expression from the long terminal repeat (LTR), in contrast to expression from the internal promoter, is dependent on the site of integration. Thus, retroviral vectors can be used for tissue-specific expression of foreign genes in transgenic mice, as well as for the identification of loci that allow developmental activation of a provirus.     

Implantation of vascular grafts lined with genetically modified endothelial cells

The possibility of using the vascular endothelial cell as a target for gene replacement therapy was explored. Recombinant retroviruses were used to transduce the lacZ gene into endothelial cells harvested from mongrel dogs. Prosthetic vascular grafts seeded with the genetically modified cells were implanted as carotid interposition grafts into the dogs from which the original cells were harvested. Analysis of the graft 5 weeks after implantation revealed genetically modified endothelial cells lining the luminal surface of the graft. This technology could be used in the treatment of atherosclerosis disease and the design of new drug delivery systems.