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During meiosis, crossover recombination connects homologous chromosomes to direct their accurate segregation 1 . Defective crossing over causes infertility, miscarriage and congenital disease. Each pair of chromosomes attains at least one crossover via the formation and biased resolution of recombination intermediates known as double Holliday junctions 2,3 . A central principle of crossover resolution is that the two Holliday junctions are resolved in opposite planes by targeting nuclease incisions to specific DNA strands 4 . The endonuclease activity of the MutLγ complex has been implicated in the resolution of crossovers 5-10 , but the mechanisms that activate and direct strand-specific cleavage remain unknown. Here we show that the sliding clamp PCNA is important for crossover-biased resolution. In vitro assays with human enzymes show that PCNA and its loader RFC are sufficient to activate the MutLγ endonuclease. MutLγ is further stimulated by a co-dependent activity of the pro-crossover factors EXO1 and MutSγ, the latter of which binds Holliday junctions 11 . MutLγ also binds various branched DNAs, including Holliday junctions, but does not show canonical resolvase activity, implying that the endonuclease incises adjacent to junction branch points to achieve resolution. In vivo, RFC facilitates MutLγ-dependent crossing over in budding yeast. Furthermore, PCNA localizes to prospective crossover sites along synapsed chromosomes. These data highlight similarities between crossover resolution and the initiation steps of DNA mismatch repair 12,13 and evoke a novel model for crossover-specific resolution of double Holliday junctions during meiosis.

Objectives: To analyze whether prostate size affects biochemical relapse-free survival (bRFS)., Methods: The bRFS outcomes for 390 patients with a minimum of 2 years of follow-up were determined from a review of a prospectively maintained database. All patients were treated with iodine-125 alone as the radiotherapeutic modality and had a minimum of four posttreatment prostate-specific antigen values. None were treated with androgen deprivation. The factors examined in the univariate and multivariate analyses predicting for bRFS included gland volume, patient age, initial prostate-specific antigen value, biopsy Gleason score, clinical stage, and postimplant dosimetric variables., Results: Most patients had low-risk disease, and the median follow-up was 45 months (range 24 to 102). Using the American Society for Therapeutic Radiology Oncology definition of biochemical failure, the overall 5-year bRFS rate was 89.3%. On separate multivariate analyses, only the pretreatment prostate width and volume significantly influenced bRFS favorably (P = 0.0069 and P = 0.0255, respectively). No association was found between gland size/width and postimplant dosimetry., Conclusions: The results of our study have shown that implantation of large/wide prostates independently confers better bRFS.

Purpose: There have been conflicting reports in the literature regarding the prognostic significance of epidermal growth factor receptor (EGFR) amplification in patients with glioblastoma multiforme (GBM). The purpose of this study is to determine the prognostic significance of EGFR amplification in patients with GBM treated at the Cleveland Clinic Foundation., Methods and Materials: A retrospective review of GBM patients treated with surgery at the Cleveland Clinic Foundation was performed. Amplification of EGFR was evaluated with fluorescence in situ hybridization in a total of 107 patients diagnosed between December 1995 and May 2003. In addition to EGFR status, various prognostic factors were evaluated to determine the factors that influenced survival and radiographic response rate. The median follow-up was 9 months., Results: The overall median survival was 9.8 months, with a 1-year survival of 40%. Of the 107 patients in whom EGFR status was evaluated, 36 (33.6%) were found to have EGFR amplification. On multivariate analysis, median survival was found to be significantly improved for patients with age < 60 (12.6 months vs. 8 months, p = 0.0061), patients with Karnofsky Performance Status > or = 70 (12.1 months vs. 4.4 months, p < 0.0001), patients who had undergone subtotal resection or gross total resection (11.1 months vs. 4.1 months, p = 0.002), and patients who received a radiation dose > or = 60 Gy compared with no radiation (12.7 months vs. 3 months, p < 0.0001). There was no association of EGFR amplification with survival. When stratified by age (< 60 vs. > or = 60), EGFR status still did not reach statistical significance in predicting for survival. For the 81 patients who had radiographic follow-up, the 1-year overall local control was 14%. On univariate analysis, only treatment with radiation (< 60 Gy vs. > or = 60 Gy vs. no radiation, p = 0.03) was found to predict for improved local control. Treatment with radiation did not remain statistically significant on multivariate analysis., Conclusion: Epidermal growth factor receptor amplification was not found to be a significant prognostic indicator of overall survival or radiographic local control in patients with GBM treated with surgery at the Cleveland Clinic Foundation. Further studies are needed to fully delineate the significance of this molecular marker in patients with GBM.

Small cell lung cancer (SCLC) accounts for approximately 20% of all cases of lung cancer. It tends to disseminate earlier in the course of its natural history than non-small cell lung cancer and is clinically more aggressive. Approximately 10% of patients present with brain metastases at the time of initial diagnosis, and an additional 40% to 50% will develop brain metastases some time during the course of their disease. The prognosis of patients with brain metastases from SCLC is poor despite years of research. The standard of care remains appropriate medical management followed by whole brain radiation therapy. Current research is evaluating novel agents in an attempt to improve the survival and quality of life in these patients. However, the most effective treatment for brain metastases from SCLC is the prevention of the development of clinically detectable disease. For patients with a complete response to initial treatment, prophylactic cranial irradiation is an effective method of prevention.

Seventeen of 22 group A meningococcal strains were separated into four serotypes by a microbactericidal assay using group A antisera. In addition, 6 of 19 of these strains were killed by a group B antiserum and similar cidal patterns were obtained with a group C antiserum. There was little correlation between type and case or carrier isolates, or between types and geographical location.

Neisseria gonorrhoeae was cultivated in mammalian cell cultures in an effort to determine if this environment will elicit a T4 --> T1 transition. Of four avirulent (T4) isolates tested, only one, H4, yielded T1 colonies. This change was consistently obtained in HeLa, WI-38, and MK2 cells, even when the multiplicity of the gonococcal infection was less than 1 per culture. Growth of the gonococci took place primarily on the surface of the cells, as demonstrated by light and electron microscopy, but occasional bacteria were undoubtedly intracellular. T1 colonies were seen at 24 h and were the major population at 48 h. This shift was favored by the presence of viable cells, since smaller yields of T1 were obtained when the cells were irradiated or heat inactivated. It was also favored by low pH, since T1 recovery was reduced when the buffering capacity of the medium was increased. Although the results suggest that T1 gonococci derived from H4 have a selective advantage over T4 in cell cultures, this is not true of all T1 and T4 colony types. F62 T4, which does not undergo a T4 --> T1 shift, propagated as well as T1 in HeLa cell cultures. The change in colony type of strain H4 to T1 was accompanied by formation of pili and by gain in capacity for deoxyribonucleic acid-mediated transformation. It is concluded that gonococci can undergo T4 --> T1 phase transition in mammalian cell cultures, but this property is not retained by all strains.

The effect of graded doses of irradiation (cobalt-60) on the morphology of McCoy cells was analyzed, and 4,000 to 5,000 r was selected as a satisfactory dose for production of giant cells. The susceptibility of radiation-induced giant cells to chlamydial infection was compared with that of nonirradiated cells by using three strains of Chlamydia trachomatis and one of C. psittaci. Monolayers of giant cells were more susceptible than normal McCoy cells as indicated by (i) greater numbers of inclusions (four- to eightfold) per unit area of monolayer, (ii) larger inclusions (fourfold greater in area), (iii) higher infective titers (1 log or more greater) of harvested cells, and (iv) greater ease of promoting a second cycle of growth. Graded doses of irradiation were applied also to mouse fibroblast (L) cells, and a similar increase in susceptibility to chlamydial infection was noted. It is concluded that giant cells produced by irradiation possess advantages over nonirradiated cells in culture for growth of Chlamydia.

Concentrations of 20 mug of sulfadiazine or 30 mug of d-cycloserine/ml were found to be suitable for testing the differential susceptibility of Chlamydia trachomatis and C. psittaci to these drugs in cell cultures.

When cultures of cells derived from the entoderm of the chick embryo were infected with trachoma virus, cytoplasmic inclusion bodies composed of viral particles were easily demonstrated. The inclusions are similar to those found in stained smears from trachomatous eyes and they developed in a sequence characteristic for this group of viruses. This method of culture appears to offer a valuable additional tool for study of the trachoma agent.