Carotid surgery in northern Tasmania: a retrospective review

A retrospective survey of 138 carotid endarterectomies performed in Northern Tasmania over a 6 year period was conducted to identify risk factors for postoperative neurological complications. A total of 80% of patients were operated on for transient ischaemic attacks (TIA) referable to stenosis of the ipsilateral internal carotid artery (ICA). A total of 77% of patients who were operated on had angiographic evidence of severe (over 80%) stenosis of the affected ICA. A combined postoperative permanent neurological deficit and mortality rate of 5.8% was achieved. Severe stenosis of the contralateral internal carotid artery and pre-operative symptomatic instability were associated with the development of postoperative neurological complications.

Heparin-rebound in the early postoperative phase following cardiopulmonary bypass

The incidence of the 'heparin-rebound' phenomenon after protamine neutralization of systemic heparinization required for cardiopulmonary bypass (CPB) was investigated. Heparin-effect was detected in 43% of patients studied at 2 h, 31% at 4 h, and 37% at 8 h after reversal of circuit heparin on CPB. Heparin-rebound was shown to be associated with a small but significant increase in postoperative bleeding which was not of clinical importance.

The dynamic progression of evolved character states for aromatic amino acid biosynthesis in gram-negative bacteria

A systematic analysis of the evolution of aromatic amino acid biosynthesis in the Proteobacteria, previously focussed mainly upon the gamma subdivision, has now been extended to the beta subdivision. Five lineages were studied, represented by Neisseria gonorrhoeae, Nitrosomonas europaea, Alcaligenes faecalis, rRNA Group-III pseudomonads/Rubrivivax gelatinosus, and rRNA Group-II pseudomonads/Rhodocyclus tenuis. Within the phenylalanine pathway, the bifunctional P-protein (chorismate mutase/prephenate dehydratase) was present in each lineage and must have evolved in a common ancestor of the beta and gamma subdivisions. Each P-protein was found to be subject to activation by L-tyrosine, and to feedback inhibition by L-phenylalanine. Phenylalanine-inhibited (DS-phe) and tyrosine-inhibited (DS-tyr) isoenzymes of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase probably existed in the common beta-subdivision ancestor, with DS-tyr being lost in N. gonorrhoeae and A. faecalis. The participation of DS-phe in a dissociable multienzyme complex with one or more other common-pathway enzymes is known to exist in N. gonorrhoeae. The same complex is indicated by two peaks of DS-phe seen in chromatographic profiles of Group-III pseudomonads and A. faecalis. It is concluded that the contemporary DS-phe species present in subdivision gamma and beta must have had independent origins. Tyrosine biosynthesis was found to be quite diverse within the beta subdivision. Nit. europaea possessed an arogenate dehydrogenase which was specific for NADP+. In all other lineages, a broad-specificity cyclohexadienyl dehydrogenase (CHD) was present. In N. gonorrhoeae the CDH was specific for NAD+ while the remaining CDH species could utilize either NAD+ or NADP+. Only the CDH species within the rRNA Group-II pseudomonad/R. tenuis lineage was feedback-inhibited by L-tyrosine, and this correlated with an allosteric pattern where activation of the prephenate dehydratase component of the P-protein by L-tyrosine was relatively poor. However, the CDH enzyme present in N. gonorrhoeae and A. faecalis was subject to inhibition by 4-hydroxyphenylpyruvate, this being competitive with respect to the cyclohexadienyl substrate. The monofunctional species of chorismate mutase (CM-F) and cyclohexadienyl dehydratase, widely distributed among the gamma-subdivision assemblage and recently shown to be periplasmic enzymes, were demonstrated in Pseudomonas pickettii, a member of rRNA homology Group-II.