Investigation of immunoadsorbent efficiency and capacity for the isolation of tRNAs containing N6-(delta 2-isopentenyl)adenosine derivatives

Antibodies directed to modified nucleosides recognize the nucleoside (antigen) when it is present in an intact tRNA molecule. The general application of anti-nucleoside immunoadsorbent chromatography, however, has been greatly impeded by the apparent inefficiency and low capacity of conventional immunoadsorbents for transfer RNA. Antibodies specific for isopentenyladenosine (i6A) were employed to investigate the efficacy of various immunoadsorbents with respect to immobilization of antibody protein and with respect to their ability to bind i6A-containing tRNAs. Biologically active anti-i6A was recovered in high yield (80-88%) by affinity chromatography on i6A-adipate-Sepharose 4B or i6A-butane diglycidyl ether-Sepharose 4B using either 15% pyridine in phosphate-buffered saline or 0.2 M acetic acid as eluents. The binding capacity of various anti-i6A antibody immunoadsorbents was evaluated. While both anti-i6A antibody-protein A-agarose-iminothiolane (ITL) and anti-i6A antibody-protein A-agarose-dimethyl suberimidate showed a high capacity for i6A-tRNA, the latter column is much less efficient with respect to antibody immobilization. Under optimal conditions, the ITL immunoadsorbent binds 5-6 nmol of i6A/mg of antibody protein. With respect to bulk tRNA, 1 mg of antibody protein (ITL immunoadsorbent) binds all of the i6A-tRNA in a 1-mg sample.     

Myocardial deletion of Smad4 using a novel α skeletal muscle actin Cre recombinase transgenic mouse causes misalignment of the cardiac outflow tract

SMAD4 acts as the converging point for TGFβ and BMP signaling in heart development. Here, we investigated the role of SMAD4 in heart development using a novel α skeletal muscle actin Cre recombinase (MuCre) transgenic mouse strain. Lineage tracing using MuCre/ROSA26^LacZ reporter mice indicated strong Cre-recombinase expression in developing and adult heart and skeletal muscles. In heart development, significant MuCre expression was noted at E11.5 in the atrial, ventricular, outflow tract and atrioventricular canal myocardium, but not in the endocardial cushions. MuCre-driven conditional deletion of Smad4 in mice caused double outlet right ventricle (DORV), ventricular septal defect (VSD), impaired trabeculation and thinning of ventricular myocardium, and mid-gestational embryonic lethality. In conclusion, MuCre mice effectively delete genes in both heart and skeletal muscles, thus enabling the discovery that myocardial Smad4 deletion causes misalignment of the outflow tract and DORV.     

A baboon (Papio hamadryas) model of insulin-dependent diabetes

Over a period of four years, streptozocin has been used to induce diabetes in 10 baboons, all of whom are insulin dependent. We describe our experience with their husbandry, induction of diabetes, insulin therapy, metabolic control and growth rate. Streptozocin dosage of 60 mg/kg readily induces hyperglycemia with minimal hepatic or renal toxicity. Using a once daily injection of mixed short and intermediate acting insulins at a dosage of 2–4 U/kg, it is possible to maintain a degree of metabolic control similar to that attained in patients.     

How to Read a Phylogenetic Tree

It has been over 50 years since Willi Hennig proposed a new method for determining genealogical relationships among species, which he called phylogenetic systematics. Many people, however, still approach the method warily, worried that they will have to grapple with an overwhelming number of new terms and concepts. In fact, reading and understanding phylogenetic trees is really not difficult at all. You only need to learn three new words, autapomorphy, synapomorphy, and plesiomorphy. All of the other concepts (e.g., ancestors, monophyletic groups, paraphyletic groups) are familiar ones that were already part of Darwinian evolution before Hennig arrived on the scene.