The MMS22L–TONSL heterodimer directly promotes RAD51‐dependent recombination upon replication stress

Homologous recombination (HR) is a key pathway that repairs DNA double‐strand breaks (DSBs) and helps to restart stalled or collapsed replication forks. How HR supports replication upon genotoxic stress is not understood. Using in vivo and in vitro approaches, we show that the MMS22L–TONSL heterodimer localizes to replication forks under unperturbed conditions and its recruitment is increased during replication stress in human cells. MMS22L–TONSL associates with replication protein A (RPA)‐coated ssDNA, and the MMS22L subunit directly interacts with the strand exchange protein RAD51. MMS22L is required for proper RAD51 assembly at DNA damage sites in vivo, and HR‐mediated repair of stalled forks is abrogated in cells expressing a MMS22L mutant deficient in RAD51 interaction. Similar to the recombination mediator BRCA2, recombinant MMS22L–TONSL limits the assembly of RAD51 on dsDNA, which stimulates RAD51‐ssDNA nucleoprotein filament formation and RAD51‐dependent strand exchange activity in vitro. Thus, by specifically regulating RAD51 activity at uncoupled replication forks, MMS22L–TONSL stabilizes perturbed replication forks by promoting replication fork reversal and stimulating their HR‐mediated restart in vivo.     

How breast cancer presents.

A study of 501 new breast cancers in patients seen in a consulting surgical practice revealed that 87% were in patients 45 years of age or older. The patients had found 83% of the cancers. The distributions of size and stage were the same for the tumours found by the patients and those found by the referring physicians. Two thirds of the cancers had an associated visible clinical sign, demonstrating the importance of inspection in the examination of the breast. Dimpling, sometimes apparent only on manipulation of the tumour, was present with 264 of the cancers and was often associated with "minimal" lesions. Mammography was done for 63 of the breast cancers but it missed 27. Of the physician-found cancers 15 were in patients who had already had breast cancer, 4 were in patients presenting with symptomatic metastases and 14 were in women presenting with other disorders. Of the 52 cancers found by periodic examination 3 were locally advanced and 21 had axillary metastases, while among the 28 "early" cancers 12 were in women who were senile, mentally defective or psychotic. Only four of the cancers found by the physicians were in women under age 45; two were rapidly fatal, one had an axillary metastasis, and the fourth was in a woman who had had cancer of the opposite breast. The remaining 284 lesions found by periodic or routine examination in women under age 45 were benign. Thus, periodic or routine examination for unsuspected breast cancer in women under age 45 seems unjustified except in those who have already had breast cancer.     

Value of the history in the office diagnosis of breast cancer.

A review of the histories of 1059 patients with breast problems seen consecutively in office consultation revealed an incidence of breast cancer of 13%. Patients over 50 years of age or whose mother or sister had had breast cancer had a substantially greater likelihood of having breast cancer. The finding of the problem on routine examination, a family history of breast cancer in a relative other than the mother or a sister, or prominent breast pain or nipple discharge made the diagnosis of cancer less likely. Menstrual status, a history of previous benign disease, nulliparity, current hormone therapy and duration of symptoms did not help identify the patient likely to have breast cancer. Much time could be saved for both doctor and patient in taking the history from patients with breast disorders. Only the patient''s age and the history of the mother and sisters with regard to breast cancer will help identify the "high-risk" patient. Other historical findings are either valueless or should be used to reassure these usually anxious women.     

Cultured endothelial cells produce heparinlike inhibitor of smooth muscle cell growth

Using cultured cells from bovine and rat aortas, we have examined the possibility that endothelial cells might regulate the growth of vascular smooth muscle cells. Conditioned medium from confluent bovine aortic endothelial cells inhibited the proliferation of growth-arrested smooth muscle cells. Conditioned medium from exponential endothelial cells, and from exponential or confluent smooth muscle cells and fibroblasts, did not inhibit smooth muscle cell growth. Conditioned medium from confluent endothelial cells did not inhibit the growth of endothelial cells or fibroblasts. In addition to the apparent specificity of both the producer and target cell, the inhibitory activity was heat stable and not affected by proteases. It was sensitive flavobacterium heparinase but not to hyaluronidase or chondroitin sulfate ABC lyase. It thus appears to be a heparinlike substance. Two other lines of evidence support this conclusion. First, a crude isolate of glycosaminoglycans (TCA-soluble, ethanol-precipitable material) from endothelial cell-conditioned medium reconstituted in 20 percent serum inhibited smooth muscle cell growth; glycosaminoglycans isolated from unconditioned medium (i.e., 0.4 percent serum) had no effect on smooth muscle cell growth. No inhibition was seen if the glycosaminoglycan preparation was treated with heparinase. Second, exogenous heparin, heparin sulfate, chondroitin sulfate B (dermatan sulfate), chondroitin sulfate ABC, and hyaluronic acid were added to 20 percent serum and tested for their ability to inhibit smooth muscle cell growth. Heparin inhibited growth at concentrations as low as 10 ng/ml. Other glycosaminoglycans had no effect at doses up to 10 μg/ml. Anticoagulant and non- anticoagulant heparin were equally effective at inhibiting smooth muscle cell growth, as they were in vivo following endothelial injury (Clowes and Karnovsk. Nature (Lond.). 265:625-626, 1977; Guyton et al. Circ. Res. 46:625-634, 1980), and in vitro following exposure of smooth muscle cells to platelet extract (Hoover et al. Circ. Res. 47:578-583, 1980). We suggest that vascular endothelial cells may secrete a heparinlike substance in vivo which may regulate the growth of underlying smooth muscle cells.     

Hip joint replacement surgery for idiopathic osteoarthritis aggregates in families

In order to determine whether there is a genetic component to hip or knee joint failure due to idiopathic osteoarthritis (OA), we invited patients (probands) undergoing hip or knee arthroplasty for management of idiopathic OA to provide detailed family histories regarding the prevalence of idiopathic OA requiring joint replacement in their siblings. We also invited their spouses to provide detailed family histories about their siblings to serve as a control group. In the probands, we confirmed the diagnosis of idiopathic OA using American College of Rheumatology criteria. The cohorts included the siblings of 635 probands undergoing total hip replacement, the siblings of 486 probands undergoing total knee replacement, and the siblings of 787 spouses. We compared the prevalence of arthroplasty for idiopathic OA among the siblings of the probands with that among the siblings of the spouses, and we used logistic regression to identify independent risk factors for hip and knee arthroplasty in the siblings. Familial aggregation for hip arthroplasty, but not for knee arthroplasty, was observed after controlling for age and sex, suggesting a genetic contribution to end-stage hip OA but not to end-stage knee OA. We conclude that attempts to identify genes that predispose to idiopathic OA resulting in joint failure are more likely to be successful in patients with hip OA than in those with knee OA.     

The N-Terminus of CD14 Acts to Bind Apoptotic Cells and Confers Rapid-Tethering Capabilities on Non-Myeloid Cells

Cell death and removal of cell corpses in a timely manner is a key event in both physiological and pathological situations including tissue homeostasis and the resolution of inflammation. Phagocytic clearance of cells dying by apoptosis is a complex sequential process comprising attraction, recognition, tethering, signalling and ultimately phagocytosis and degradation of cell corpses. A wide range of molecules acting as apoptotic cell-associated ligands, phagocyte-associated receptors or soluble bridging molecules have been implicated within this process. The role of myeloid cell CD14 in mediating apoptotic cell interactions with macrophages has long been known though key molecules and residues involved have not been defined. Here we sought to further dissect the function of CD14 in apoptotic cell clearance. A novel panel of THP-1 cell-derived phagocytes was employed to demonstrate that CD14 mediates effective apoptotic cell interactions with macrophages in the absence of detectable TLR4 whilst binding and responsiveness to LPS requires TLR4. Using a targeted series of CD14 point mutants expressed in non-myeloid cells we reveal CD14 residue 11 as key in the binding of apoptotic cells whilst other residues are reported as key for LPS binding. Importantly we note that expression of CD14 in non-myeloid cells confers the ability to bind rapidly to apoptotic cells. Analysis of a panel of epithelial cells reveals that a number naturally express CD14 and that this is competent to mediate apoptotic cell clearance. Taken together these data suggest that CD14 relies on residue 11 for apoptotic cell tethering and it may be an important tethering molecule on so called ‘non-professional’ phagocytes thus contributing to apoptotic cell clearance in a non-myeloid setting. Furthermore these data establish CD14 as a rapid-acting tethering molecule, expressed in monocytes, which may thus confer responsiveness of circulating monocytes to apoptotic cell derived material.     

Emergency geriatric surgical admissions

The emergency surgical work load created by patients aged 80 and over in a district hospital was assessed and the results of treatment examined. Over one year 248 patients aged 80 or over were admitted as emergencies, and the overall mortality rate was 21·8%. When terminal disease was excluded mortality rate was 12·5%. These elderly patients had an average length of stay in the acute surgical ward of 14·7 days compared with a mean of 8·4 days for all patients, and all but seven patients were discharged to their original place of referral.Elderly patients do exacerbate the bed shortage in acute surgical wards because they tend to stay longer than younger patients, but these elderly surgical patients imposed only a small load on the inpatient geriatric services, as 78% were discharged straight to their own homes and a further 17% went home after a period on the surgical convalescent wards.     

Does continuing medical education by peer review really work?

A peer review of breast operation statistics was conducted. Standards for the proportion of biopsies positive for cancer, and for length of postoperative stay following operation for benign and malignant conditions were developed and each surgeon was informed of his performance and how it compared with that of his colleagues. The same parameters of care were reviewed one year later to study changes in performance. Low volume of clinical material, failure of two surgeons to change, and a steady general improvement in all parameters in the years prior to the presentation of the peer review, confused the demonstration of improvement in the year after the educational effort. There was a statistically significant improvement in the proportion of biopsies positive for cancer, reflecting reduction in unnecessary biopsies, but the pre-existing annual improvement in reducing postoperative stays was not accelerated. Does continuing medical education by peer review really work? Probably.