Comparison among DNA polymerases 1, 2 and 3 from maize embryo axes. A DNA primase activity copurifies with DNA polymerase 2.

Three DNA polymerase activities, named 1, 2 and 3 were purified from maize embryo axes and were compared in terms of ion requirements, optimal pH, temperature and KCl for activity, response to specific inhibitors and use of templates. All three enzymes require a divalent cation for activity, but main differences were observed in sensitivity to inhibitors and template usage: while DNA polymerases 1 and 2 were inhibited by N-ethyl maleimide and aphidicolin, inhibitors of replicative-type enzymes, DNA polymerase 3 was only marginally or not affected at all. In contrast, DNA polymerase 3 was highly inhibited by very low concentrations of ddTTP, an inhibitor of repair-type enzymes, and a 100-fold higher concentration of the drug was needed to inhibit DNA polymerases 1 and 2. Additionally, DNA polymerases 1 and 2 used equally or more efficiently the synthetic template polydA-oligodT, as compared to activated DNA, while polymerase 3 used it very poorly. Whereas DNA polymerases 1 and 2 shared properties of replicative-type enzymes, DNA polymerase 3 could be a repair-type enzyme. Moreover, a DNA primase activity copurified with the 8000-fold purified DNA polymerase 2, strengthening the suggestion that polymerase 2 is a replicative enzyme, of the alpha-type. This DNA primase activity was also partially characterized. The results are discussed in terms of relevant data about other plant DNA polymerases and primases reported in the literature.

Clinical course and prognosis of Brucella spondylitis.

A multicentre prospective study of 593 patients with brucellosis, of whom 58 (9.7%) had spondylitis, was performed in order to evaluate the possible clinical, radiological and evolutionary differences in the different segments of the spinal column. Five of the patients with cervical spondylitis (71%) had compression of the medulla or roots, versus just two (11%) in the dorsal group and nine (21%) in the lumbar group (p less than 0.05). There were no other clinical, haematological or biochemical differences between the three spinal segments, and both the serological response and the percentage of positive blood cultures were also similar in the three groups. The patients with cervical and dorsal spondylitis had a significantly higher number of paravertebral and/or epidural masses than those with lumbar spondylitis (p less than 0.05). Seventy-one percent of the patients with cervical spondylitis made unsatisfactory progress, versus 11% and 5% of those in the dorsal and lumbar groups, respectively (p less than 0.05 and p less than 0.001). In conclusion, given the high incidence of paravertebral and/or epidural masses, the neurological involvement, and the high rate of important functional disabilities, cervical spondylitis should be considered to be a very severe complication of brucellosis, and its treatment and follow-up must therefore be energetic and rigorous in order to detect and correct as early as possible compressions of the neural axis and its roots.

Serology, clinical manifestations and treatment of brucellosis in different age groups.

We prospectively studied 339 patients diagnosed of brucellosis over a six year period in order to evaluate the clinical and serological characteristics of brucellosis in the elderly. 319 patients (94.1%) were under 65 years of age (group A), and 20 patients (5.9%) were older than 65 (group B). No patient in group B developed splenomegaly as opposed to 69 (21.6%) in group A (p less than 0.05). The percentage of positive blood cultures (Brucella melitensis isolated in all cases) was 72.1% in group A and 60% in group B. The mean titer of IgM antibodies measured by indirect immunofluorescence test was significantly lower in the elderly patients, with no other differences in serologic response between the two groups. 103 patients (32.2%) in group A and seven patients (35%) in group B developed some complications; spondylitis was more common and severe among group B patients. There was no therapeutic failure or relapse among patients over 65. We conclude that clinical, bacteriological and serological characteristics and the outcome of brucellosis in the elderly are similar to those seen in younger patients.