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The derived amino-acid sequences of the proteins encoded by E. coli genes sbcC and sbcD have been compared with other protein sequences using computer assisted methods. This work has shown that SbcC and D, which inhibit the propagation of replicons containing long palindromic DNA sequences, are distantly related to two putative bacteriophage nucleases. These nucleases both comprise two polypeptide chains which are the products of genes 46 and 47 of bacteriophage T4 (gp 46 and gp 47) and genes D13 and D12 of bacteriophage T5 (gp D13 and gp D12). The comparisons reveal that SbcC, gp 46 and gp D13 are more closely related to each other than are SbcD, gp 47 and gp D12. SbcC appears to have undergone a partial duplication of an ancestral sequence. These proteins all contain motifs common to the superfamily of nucleotide-binding proteins that includes UvrA and the cystic fibrosis transmembrane regulator CFTR.

Review of cerebral arteriograms of all our patients [19] with epidural hematoma over a 2 year period revealed evidence of localized extrinsic compression of the cerebral cortex in all cases. This finding, although not as specific as those previously described for epidural hematoma, was strongly suggestive. A 2 year prospective study was then initiated employing internal, rather than common carotid arteriography, because opacification of the external carotid artery is not necessary for evaluation of cortical compression. In this study, which consisted of 21 patients, epidural hematoma was correctly diagnosed in all, relying primarily on signs of localized extrinsic cerebral cortical compression. No epidural hematoma was misinterpreted as being a subdural hematoma or an intracerebral injury, and all epidural hematomas that were present were diagnosed correctly. We conclude that internal carotid arteriography is a sensitive method for diagnosing epidural hematoma. The signs of extrinsic cortical compression should be emphasized in the interpretation of arteriograms of patients with head injuries whether the internal or the common carotid artery is injected.

WE have previously described1 the synthesis and use of bromohydroxyacetone phosphate (BHAP) as an active site directed inhibitor of triose phosphate isomerase (EC 5.3.1.1) from rabbit and chicken muscle (TIM). We report here the isolation and characterization of a uniquely labelled hexapeptide sequence probably forming part of the active site of the chicken enzyme.