High resolution footprinting of a type I methyltransferase reveals a large structural distortion within the DNA recognition site

The type I DNA methyltransferase M.EcoR124I is a multi-subunit enzyme that binds to the sequence GAAN6RTCG, transferring a methyl group from S-adenosyl methionine to a specific adenine on each DNA strand. We have investigated the protein-DNA interactions in the complex by DNase I and hydroxyl radical footprinting. The DNase I footprint is unusually large: the protein protects the DNA on both strands for at least two complete turns of the helix, indicating that the enzyme completely encloses the DNA in the complex. The higher resolution hydroxyl radical probe shows a smaller, but still extensive, 18 bp footprint encompassing the recognition site. Within this region, however, there is a remarkably hyper-reactive site on each strand. The two sites of enhanced cleavage are co-incident with the two adenines that are the target bases for methylation, showing that the DNA is both accessible and highly distorted at these sites. The hydroxyl radical footprint is unaffected by the presence of the cofactor S-adenosyl methionine, showing that the distorted DNA structure induced by M.EcoR124I is formed during the initial DNA binding reaction and not as a transient intermediate in the reaction pathway.     

Interleukin 8 (IL-8) induces the expression of kinin B1 receptor in human lung fibroblasts

Near-haploidy is a rare cytogenetic finding in childhood acute lymphoblastic leukaemia (ALL) and is associated with a poor prognosis. A second hyperdiploid line, occurring presumably by endoreduplication of the near-haploid stemline, is often observed. We present a case of common ALL in relapse characterized morphologically by a dual population of small and large lymphoblasts. Cytogenetic analysis supplemented with fluorescence in-situ hybridization (FISH) studies localized near-haploidy and hyperdiploidy to the small and large blast population respectively. DNA ploidy determination confirmed two abnormal clones with near-haploidy as the predominant one. A novel t(9;12)(q11;q13) was present in the near-haploid clone and was duplicated in the hyperdiploid clone. This finding identified cells bearing near-haploidy to be the clonogenic population following malignant transformation and confirmed endoreduplication as the mechanism for the presence of associated hyperdiploidy.     

Can adrenal incidentalomas be safely observed?

We currently recommend excision of adrenal incidentalomas > or = 4 cm in size and all hormonally active tumors. The optimal management and follow-up of smaller nonfunctioning tumors are controversial. The aim of this study was to determine the clinical outcome of a well defined population of patients with incidentalomas followed without operative intervention. The study group comprised 231 patients, identified from the records of abdominal or thoracic computed tomographic (CT) scans performed between 1985 and 1989. The primary outcome variable analyzed was survival. Follow-up was obtained by office records, telephone contact, or letter. There were 101 male and 130 female patients with a mean age at diagnosis of 64 years (range 5-86 years). Most adrenal tumors were unilateral (right 113; left 98); 20 were bilateral. Mean tumor size was 2 cm (range 1-6 cm). In nine (4%) patients the tumor was > or = 4 cm. Follow-up [mean 7 years; range 1 month (patient died) to 11.7 years] was complete in 224 (97%) patients. Ninety-one (39%) patients had one or more additional CT scans performed during the follow-up period, with only four patients demonstrating a > 1 cm increase in the size of the adrenal mass. Surgical excision of these four lesions identified benign pathology. Eighty-one (35%) patients died of conditions unrelated to adrenal pathology. No patient developed subsequent adrenal hyperfunction or adrenal malignancy. Within the context of our guidelines, conservative management of adrenal incidentalomas considered benign or nonfunctioning at diagnosis is appropriate. Additional information provided by repeat CT scanning appears to confer limited benefit. This study does not support laparoscopic removal of small, nonfunctional adrenal tumors, as has been suggested.     

Accuracy of single-photon emission computed tomography myocardial perfusion imaging in patients with stents in native coronary arteries

Strategies to noninvasively evaluate patients after coronary stenting have not been evaluated. To determine the accuracy of single-photon emission computed tomography (SPECT) myocardial perfusion imaging in patients after coronary stenting, 209 patients who had undergone stenting followed by late stress SPECT myocardial perfusion imaging were evaluated. Quantitative coronary angiography was performed in 33 patients following SPECT imaging. SPECT restenosis was defined as a reversible or fixed defect within the stented vascular territory. Angiographic restenosis was examined using 2 definitions: total area narrowing > or =50% or > or =70% of the stent site or stented artery. The SPECT and angiographic findings were concordant in 22 of 33 stented vascular territories using the 50% definition of restenosis and in 29 of 33 stented territories using the 70% definition. Use of the 70% definition of restenosis resulted in improved accuracy of SPECT to detect a significant stenosis in the stented artery. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of SPECT were 95%, 73%, 88%, 89%, and 88% respectively. In patients with positive SPECT scans, the most significant stenosis in the stented artery was outside the stent site in 50% of cases. SPECT imaging appears to be accurate to predict significant stenosis in the stented artery, although the most severe stenosis is frequently distant from the stent site.     

Management of chylothorax

BACKGROUND: Chylothorax is a rare primary or secondary condition the optimum management of which remains uncertain. METHODS: Twenty cases of chylothorax, including ten of primary chylothorax and ten secondary to either malignancy, subclavian vein thrombosis or lymphangioma treated between 1956 and 1986 have been reviewed. RESULTS: Open pleurectomy was the most successful treatment in preventing reaccumulation of the effusion. Three patients had thoracic duct-azygous vein anastomoses, but all anastomoses were probably occluded within a year of surgery. Three patients have been lost to follow-up and five died within 2 years of their treatment, but 12 patients were alive and free from an effusion 3-22 years after treatment. CONCLUSION: Patients with chylothorax should undergo lymphangiography to identify the cause and site of the lymphatic abnormality. Conservative treatment is successful in some patients but should be abandoned if the fluid loss exceeds 1.5 l/day for more than 5-7 days in an adult or more than 100 ml/day in a child. Parietal pleurectomy is the most successful treatment when no distinct chylous leak can be identified. Less commonly, an isolated chylous leak either in the chest or in the abdomen may be identified and this should be treated by direct ligation.     

Role of diameter differences among follicles in selection of a future dominant follicle in mares

Follicles > or = 5 mm were ablated in pony mares by a transvaginal ultrasound-guided technique on Day 10 (ovulation = Day 0). Follicle emergence (at 15 mm, experiment 1; at 6 mm, experiment 2) and development of the new wave was monitored by transrectal ultrasound. Deviation was defined as the beginning of a marked difference in growth rates between the two largest follicles. In experiment 1, mares were grouped (n = 4 per group) into controls, ablation-controls (ablations at Day 10 only), and a two-follicle model (periodic ablation sessions so that only the two largest follicles developed). There were no significant indications that the two-follicle model altered follicle diameters, growth rates, or time intervals of the two retained follicles at or between events (follicle emergence, deviation, and ovulation). In experiment 2, the two-follicle model (n = 14) was used for follicle and hormonal characterization and hypothesis testing, without the tedious and error-prone necessity for tracking many (e.g., 20) individual follicles. The future dominant follicle emerged a mean of 1 day earlier (p < 0.008) than the future subordinate follicle, the growth rates for the two follicles between emergence and deviation (6 days later) did not differ, and the dominant follicle was larger at the beginning of deviation (23.1 +/- 0.8 mm versus 19.6 +/- 0.9 mm; p < 0.0001). Mean FSH and LH concentrations increased (p < 0.05) concomitantly from emergence of the future dominant follicle and peaked 3 days later when the follicle was a mean of 13 mm. Thereafter, the two hormones disassociated until ovulation: FSH decreased and LH increased. Results supported the hypothesis that the future dominant follicle has an early size advantage over future subordinate follicles and indicated that the advantage was present as early as 6 days before deviation.