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We have studied DNA synthesis in vitro using as template phi X174 DNA containing varying numbers of adducts formed by reaction with cis and trans benzo[a]pyrene (BP) diol-epoxides. The extent of DNA synthesis decreases with increasing numbers of adducts and there is a concomitant decrease in the size of the DNA products. Both decreases can be accounted for quantitatively by the assumption that synthesis terminates at every BP adduct. Since the majority of the adducts are located at the 2-amino group of guanine, we deduce that these adducts cause termination. The role of adducts at other sites is uncertain. The cis and trans BP diol-epoxides are indistinguishable with regard to chain termination, yet in vivo these isomers behave differently. These results suggest that chain determination alone is insufficient to account for the mutagenic effects of BP diol-epoxides.

Immunohistochemical localization of types I, II, and III collagen in the ossified posterior longitudinal ligament of the cervical spine was studied using type-specific anticollagen antibodies. In contrast to the normal ligament which contains both types I and III collagens, the ossified matrix, composed of lamellar bone, contains only type I collagen, except for Haversian canals where type III is located in the inner wall. In the transitional region of preossifying ligaments, types III and I are both present. Type II collagen is present in the hyperplastic matrix of the ligament, and cartilage-like cells surrounded by type II collagen are aligned along nonossified ligaments adjacent to the preossifying region. A possible mechanism of matrix transition during the ossification process is given attention.

Monitoring of the spinal cord function by evoked spinal cord potentials (ESP) has come to be used widely with the establishment of a safe technique using an epidural electrode and the great improvement in medical electronic devices. According to other investigations ESP has been recorded through an electrode placed in the posterior epidural space, it is well known that residual ESP can be actually recorded after transection of the posterior half of the spinal cord and that ESP shows no change after a small transection of the anterior column. If ESP originating from the anterior half of the spinal cord is recorded, it is very useful for monitoring during anterior decompression surgery for myelopathy such as ossification of the posterior longitudinal ligament and cervical spondylosis. The purpose of this report is to analyse ESP originating from the anterior half of the spinal cord experimentally and further investigate the ESP monitoring clinically. Sixty cats were used in this study. ESP recording principally consisted of stimulation to the spinal cord at the level of thoracic or lumbar region and recording of ESP with a monopolar electrode placed in the cervical epidural space. Changes in the ESP after transection and compression of the spinal cord were analysed. Anterior vertebrectomy and laminectomy at C2 and C6 were performed for the purpose of placing an electrode correctly and facilitating transection or compression of the spinal cord. Recording electrodes were placed on both the anterior and posterior surfaces of the dura mater at C2. As the result of this study, it is apparent that there exists the ESP originating from the anterior half of the spinal cord. Such ESPs are more accurately recorded through an anterior placed electrode rather than through that placed posteriorly.

Reverse transcription of 70S AMV RNA by AMV reverse transcriptase has been studied in the presence of E. coli tRNAs. We have shown that inhibition of DNA synthesis occurs and that the tRNAs bind to the enzyme and not to the 70S RNA. The results have implications for the control of reverse transcription in vivo.

Two diol epoxides of benzo(a)pyrene (BP), and benzo(a)pyrene 4,5-oxide, have been used to make adducts in the homopolymers polyribocytidylic acid, (rC); polyriboadenylic acid (rA), polydeoxycytidylic acid (dC) and polydeoxyadenylic acid (dA). With appropriate oligomers as primers these modified and unmodified polynucleotides were used as templates for DNA synthesis with avian myeloblastosis virus DNA polymerase (AMV) or E. coli Pol I DNA polymerase. We have found that: (1) the size of the DNA product is not markedly decreased by the presence of these these polycyclic aromatic hydrocarbon adducts in the templates; (2) the presence of adducts does not lead to increased incorporation of erroneous bases. These results, supported by kinetic data, suggest that these polymerases can bypass a site containing an adduct on the template without leaving a gap or causing misincorporation of a base and they imply that mutagenesis by BP may not be attributable to either of these mechanisms.

Two cases of tapered occlusion of the unilateral internal carotid artery after head and facial injury are reported. The first was a 42-year-old male admitted because of left hemiparesis 3 hours after receiving blows to the face. Computed tomography (CT) scan obtained 10 hours after injury showed an area of slight low density in the right frontotemporal region. Carotid angiography demonstrated tapered occlusion of the right cervical internal carotid artery. A large cerebral infarction had developed in the right hemisphere and the patient died 10 days after the traumatic incident. The second case involved a 45-year-old male hospitalized with aphasia and right hemiparesis about 1 month after incurring a depressed fracture of the left temporal bone. CT revealed two small low-density areas in the left corona radiata, and carotid angiography disclosed tapered occlusion of the left cervical internal carotid artery. The neurological signs gradually improved after anticoagulant therapy. Early diagnosis of traumatic cervical carotid artery occlusion may be difficult in the absence of apparent cervical trauma with focal cerebral symptoms appearing after a lucid interval. No definitive management has been established and the prognosis is poor. It is emphasized that unusual neurological symptoms following head or cervical trauma should provoke suspicion of carotid artery injury, which, on diagnosis, should be promptly treated.