Processing by ribonuclease II of the tRNATyr precursor of Escherichia coli synthesized in vitro

The tRNATyr precursor molecule, synthesized from phi 80 psu3+ DNA (containing a single tRNA gene) by DNA-dependent RNA polymerase and q factor, was about 205 nucleotides long. The main product of its digestion with a ribonuclease tii preparation from Escherichia coli showed the same electrophoretic mobility as tRNAtyr precursor isolated in vivo and was found to be identical to it when analysed using fingerprint techniques. This intermediate precursor synthesized in vitro was converted further by processing with ribonuclease P into an RNA identical size to mature tRNATyr. It was concluded that the initiation of transcription of the tRNATyr gene in vitro occurs at the same site as that of transcription in vivo and a termination occurs at about 80 nucleotides beyond the CCA end of tRNATyr.

Surgical treatment of annulo-aortic ectasia

Replacement of the aortic valve and the entire ascending aorta (modified Bentall's technique) was performed in 11 patients with annulo-aortic ectasia. Nine patients are alive and well postoperatively. In comparison with our previous surgical technique, by which the aortic root was left remaining without removal, the new technique required less bypass time, including less coronary perfusion time and less amount of intraoperative bleeding than the cases handled by the previous technique, whereas amount of postoperative bleeding in both groups was not significantly different. Details of the new technique were described and the advantages of this technique are security of intraoperative hemostasis as well as shortened operation time. The Björk-Shiley tilting disc prosthesis was really convenient for this surgical technique because of its low profil architecture, and also this prosthesis gives excellent postoperative results in combination with the new surgical technique.

A comparative study between glutaraldehyde-preserved aortic and pulmonary heterograft valves in the tricuspid position in dogs

Morphological observations have been presented on 10 metaperiodate-glutaraldehyde-preserved aortic heterograft valves and 5 pulmonary heterograft valves implanted into the tricuspid position for periods ranging from 7 to 183 days. It is recognized that there was a relatively minimal histological change in pulmonary valves. However, calcification of implanted aortic cusps was observed in 20% (2 out of 10) of cases and high incidence of thrombus formation on aortic cusps was recognized, although there were none on pulmonary cusps. It seems reasonable to presume that the high incidence of thrombus formation on the aortic valves is primarily due to the decreased pliability and stiffness of the cusps. It is concluded that the pulmonary valves rather than the aortic valves are recommended for tricuspid valve replacement.

Taussig-Bing heart with mitral valve straddling: case reports and postmortem study

Seven autopsied cases of the Taussig-Bing Heart diagnosed at the Heart Institute of Japan were reexamined for this report. Three cases had been correctly classified according to the original description of the Taussig-Bing Heart. The remaining four cases provided examples of a rare variation of this malformation. Characteristic features included the following: the mitral valve straddled the ventricular septum in all cases; the chordae of the anterior leaflet crossed over the septum into the right ventricle through a large subpulmonary ventricular septal defect; and an abnormal muscle ridge, extending from the caudal part of the parietal band, covered the right ventricular side of the ventricular septal defect. Although these four cases differ anatomically from the original Taussig-Bing Heart, their hemodynamics are similar. We have called this anomaly the Taussig-Bing Heart with mitral valve straddling.

Cleavage of the glycosidic linkage of pyrimidine ribonucleosides by the bisulfite-oxygen system

When a solution containing 2 mM uridine, 20 mM sodium bisulfite, 0.1 mM MnCl(2), and 100 mM sodium phosphate buffer of pH 7.0 was incubated aerobically at 37 degrees or 0 degrees , partial cleavage of the glycosidic linkage of uridine took place. About 20% of the uridine was converted to uracil by the incubation for 4 hrs. Cytosine was produced from cytidine by similar treatment with bisulfite. These reactions were caused by free radicals generated by Mn(2+)-catalyzed autoxidation of bisulfite. Glycosidic bond cleavage by the bisulfite-oxygen system was not detected for adenosine, AMP, guanosine, GMP, thymidine, TMP, deoxyuridine, dCMP, dAMP, and dGMP. When poly(U) and poly(C) were treated with 20 mM sodium bisulfite in the same manner, chain fission of the polymer occurred as judged by the elution-pattern change in gel filtration through Sephadex columns. No change in the elution pattern was observed for bisulfite-treated poly(A), poly(U). poly(A) or tRNA.