Homologous recombinational repair vis-à-vis chlorambucil resistance in chronic lymphocytic leukemia

The objective of this study was to further define the role of homologous recombinational repair (HRR) in resistance to the nitrogen mustards in B-cell chronic lymphocytic leukemia (B-CLL). We have demonstrated previously that increased chlorambucil (CLB)-induced HsRad51 nuclear foci formation correlated with a CLB-resistant phenotype in B-CLL lymphocytes. In this report, we measured the protein levels of HsRad51 and Xrcc3 (an HsRad51 paralog) and correlated them with the in vitro CLB cytotoxicity (LD(50)) in lymphocytes from seventeen B-CLL patients. Both HsRad51 (r=0.75, P=0.0005) and Xrcc3 (r=0.52, P=0.03) protein levels correlated with the in vitro CLB LD(50). In addition, multiple linear regression analysis showed a significant correlation between Xrcc3 and Rad51 protein levels versus the CLB LD(50) (r=0.78, P=0.0014), suggesting that both proteins influence CLB cytotoxicity. Moreover, since HsRad51 expression varies in cell lines during the cell cycle, we determined proliferating cell nuclear antigen (PCNA) protein levels to assess possible differences in cell cycle progression. There was no correlation between PCNA protein levels and the CLB LD(50) (r=0.042, P=0.87) or with HsRad51/Xrcc3 protein levels. Our data suggest that HsRad51 and Xrcc3 protein expression may be predictive of the response in B-CLL patients to treatment with nitrogen mustards.     

Effect of the spectral range of a UV lamp on the production of cyclobutane pyrimidine dimers in human skin in situ

BACKGROUND: Ultraviolet (UV) irradiation has a broad spectrum of biological effects and a capacity to initiate skin carcinogenesis through DNA damage. The effect of different wave bands of UV light on the production of DNA damage in human skin in situ was studied with a broadband UV-B lamp TL-12 and a narrowband UV-B lamp TL-01. METHODS: Eight psoriasis patients participated in the study. Their minimal erythema dose was assessed separately for the two UV-B wave band ranges. Test areas of buttock skin were irradiated with the two spectrally differing lamps using erythemally equivalent UV doses of 40 and 80 mJ/cm2 CIE (Commission International de I'Eclairage). Punch biopsies were taken from the irradiated areas, and UV-induced DNA lesions (cyclobutane pyrimidine dimers, CPDs) in the skin were analyzed with a 32P high-performance liquid chromatography postlabelling method. RESULTS: No UV source-dependent differences in the induced levels of CPDs were detected in this study. CONCLUSION: CPD production with broadband TL-12 and narrowband TL-01 UV-B lamps in situ did not differ when erythemally equivalent UV doses were used. The preliminary result needs to be confirmed in a larger study.     

Diminished neuropeptide levels contribute to the impaired cutaneous healing response associated with diabetes mellitus

Background. Patients with diabetic sensory neuropathy have significant risk of chronic ulcers. Insufficient nerve-derived mediators such as substance P (SP) may contribute to the impaired response to injury. Mutant diabetic mice (db/db), which develop neuropathy and have delayed healing, may provide a model to study the role of nerves in cutaneous injury.Methods. Skin from human chronic nonhealing ulcers and age-matched control skin was immunohistochemically evaluated for nerves. Nerve counts were also compared in murine diabetic (C57BL/KsJ-m+/+ Lepr(db); db/db) and nondiabetic (db/-) skin. Excisional wounds on the backs of db/db and db/- mice were grouped as: (a) untreated db/- mice; (b) untreated db/db mice; (c) db/db mice with polyethylene glycol (PEG); (d) db/db mice with PEG and SP 10(-9) M; or (e) db/db mice with PEG and SP 10(-6) M.Results. We demonstrated fewer nerves in the epidermis and papillary dermis of skin from human subjects with diabetes. Likewise, db/db murine skin had significantly fewer epidermal nerves than nondiabetic littermates. We confirmed increased healing times in db/db mice (51.7 days) compared to db/- littermates (19.8 days; P 相似文献   

Fractionated- clamping for thoracoabdominal aortic aneurysm repair: a modified Crawford technique

Objective To apply fractionated- clamping for repair of thoracoabdominal aortic aneurysm (TAA), and evaluate its effects in decreasing surgical mortality and severe complications, such as renal failure and paraplegia, a modified crawford procedure were prospectively evaluated.Methods Using modified shunting and cross- clamping techniques, modified Crawford repair in 13 thoracoabdominal aorta patients were performed in the Vascular Division at Peking Union Medical College Hospital. TAA Crawford classification: 1 type Ⅰ, 2 type Ⅱ, 2 type Ⅲ and 3 type Ⅳ TAA. Debakey classification: 1 type Ⅰ, 4 type Ⅲ (including 2 ruptured aneurysms), and 1 aortic coarctation. Results Thirteen procedures were performed successfully. One died of ventricular fibrillation just before completing the operation. Surgical mortality rate was 7.7% (1/13). Postoperative complications included 1 acute necrotic pancreatitis, 1 ARDS, 1 paraplegia, 1 acute renal failure, and 2 thoracic cavity bleeding. Total complication rate was 53.8% （7/13）. Conclusions Fractionated- clamping in thoracoabdominal aortic aneurysm repair is our modified Crawford procedure and aortic bypass. Clinical results demonstrate that our procedure decreased surgical mortality and major complication rate, and also alleviated viscera ischemic injury. Fractionated- clamping in aorta replacement is a practical procedure for TAA repair under general anesthesia at normal temperature.     

Role of vascular endothelial growth factor in neuronal DNA damage and repair in rat brain following a transient cerebral ischemia

The antisense knockdown technique and confocal laser scanning microscopic analysis were used to elucidate vascular endothelial growth factor (VEGF) induction and its effect on DNA damage and repair in rat brain following a transient middle cerebral artery occlusion. Immunohistochemical study and in situ hybridization showed that the expression of VEGF and its mRNA was enhanced in the ischemic core and penumbra of ischemic brain. Western blot analysis further illustrated that VEGF induction was time-dependently changed in these areas. Double-staining analysis indicated that VEGF-positive staining existed in the neuron, but not in the glia, and it colocalized with excision repair cross-complementing group 6 (ERCC6) mRNA, a DNA repair factor. VEGF antisense oligodeoxynucleotide infusion reduced VEGF induction and resulted in an enlargement of infarct volume of the brain caused by ischemia. Moreover, it also increased the number of DNA damaged cells and lessened the induction of ERCC6 mRNA in ischemic brains. These results suggest that the induction of endogenous VEGF in ischemic neurons plays a neuroprotective role probably associated with the expression of ERCC6 mRNA.     

Photodynamic therapy of DNA mismatch repair-deficient and -proficient tumour cells

Loss of DNA mismatch repair is a common finding in hereditary nonpolyposis colon cancer as well as in many types of sporadic human tumours. DNA mismatch repair-deficient cells have been reported to be resistant to many chemotherapeutic agents and to radiotherapy, and to have the potential of rapidly acquiring additional mutations leading to tumour progression. Photodynamic therapy is a new treatment modality using light to activate a photosensitiser that preferentially localises in tumour cells. An oxygen dependent photochemical reaction ensues, resulting in selective tumour necrosis. The effect of loss of DNA mismatch repair activity on the sensitivity to photodynamic therapy was tested using pairs of cell lines proficient or deficient in mismatch repair due to loss of either MLH1 or MSH2 protein function. Cells were incubated with the photosensitiser 5,10,15,20-meta-tetra(hydroxyphenyl)chlorin and exposed to laser light at 652 nm with various optical doses ranging from 0-1 J cm(-2). Cell survival was assessed using the clonogenic assay. Loss of MLH1 or MSH2 function was not associated with resistance to photodynamic therapy. MCF-7 cells repeatedly treated with photodynamic therapy expressed parental levels of MLH1, MSH2, MSH6, and PMS2. DNA mismatch repair-deficient and -proficient cells showed similar subcellular distributions of meta-tetra(hydroxyphenyl)chlorin as analysed by laser scanning and fluorescence microscopy. Therefore, repeated exposure of tumour cells to photodynamic therapy does not seem to result in loss of DNA mismatch repair, and loss of mismatch repair, in turn, does not seem to contribute to resistance to photodynamic therapy. Our results suggest recommending photodynamic therapy as a strategy for circumventing resistance due to loss of DNA mismatch repair.     

Dose-effect relationship for cataract induction after single-dose total body irradiation and bone marrow transplantation for acute leukemia

PURPOSE: To determine a dose-effect relationship for cataract induction, the tissue-specific parameter, alpha/beta, and the rate of repair of sublethal damage, mu value, in the linear-quadratic formula have to be known. To obtain these parameters for the human eye lens, a large series of patients treated with different doses and dose rates is required. The data of patients with acute leukemia treated with single-dose total body irradiation (STBI) and bone marrow transplantation (BMT) collected by the European Group for Blood and Marrow Transplantation were analyzed. METHODS AND MATERIALS: The data of 495 patients who underwent BMT for acute leukemia, who had STBI as part of their conditioning regimen, were analyzed using the linear-quadratic concept. The end point was the incidence of cataract formation after BMT. Of the analyzed patients, 175 were registered as having cataracts. Biologic effective doses (BEDs) for different sets of values for alpha/beta and mu were calculated for each patient. With Cox regression analysis, using the overall chi-square test as the parameter evaluating the goodness of fit, alpha/beta and mu values were found. Risk factors for cataract induction were the BED of the applied TBI regimen, allogeneic BMT, steroid therapy for >14 weeks, and heparin administration. To avoid the influence of steroid therapy and heparin on cataract induction, patients who received steroid or heparin treatment were excluded, leaving only the BED as a risk factor. Next, the most likely set of alpha/beta and mu values was obtained. With this set, the cataract-free survival rates were calculated for specific BED intervals, according to the Kaplan-Meier method. From these calculations, cataract incidences were obtained as function of the BED at 120 months after STBI. RESULTS: The use of BED instead of the TBI dose enabled the incidence of cataract formation to be predicted in a reasonably consistent way. With Cox regression analysis for all STBI data, a maximal chi-square value was obtained for alpha/beta = 1.75 Gy and mu = 0.75 h(-1). When Cox regression analysis was applied for patients who had no steroid treatment after BMT, a maximal chi-square value was obtained for alpha/beta = 1 Gy and mu = 0.6 h(-1). Cox regression analysis was repeated using the data of patients who had not received posttransplant steroid treatment and also no heparin administration; we found alpha/beta = 0.75 Gy and mu= 0.65 h(-1). An increased cataract incidence was observed after steroid treatment of >14 weeks and heparin administration. CONCLUSION: The alpha/beta value of 0.75 Gy and mu value of 0.65 h(-1) found for the eye lens are characteristic for late-responding tissues. The incidence of cataract formation can now be quantified, taking into account the values calculated for alpha/beta and mu, TBI dose, and dose rate. Also, the reduction in cataract incidence as a result of lens dose reduction by eye shielding can be estimated.     

Application of the yeast two-hybrid system in molecular gerontology

Most – if not all – proteins are bound to interact with other proteins to exert their function, and thus the identification of the interaction partners of a protein is vital in proteomics. The yeast two-hybrid system is a popular and effective tool for studyingprotein–protein interactions. Although the advantages of the system are manifold, it also has certain drawbacks and limitations. The two-hybrid system has been shown to be extremely useful for placing a protein of unknown function within a functional context, thereby providing information about a putative role of the uncharacterised protein. This concept has also been successfully applied in molecular gerontology. This revised version was published online in July 2006 with corrections to the Cover Date.     

Ten-year outcome of patients with very small abdominal aortic aneurysm

BACKGROUND: The long-term fate of very small abdominal aortic aneurysms (AAA) is not well known. METHODS: Forty-one patients with asymptomatic small AAA (range 25 to 40 mm) underwent ultrasonographic surveillance. RESULTS: The median follow-up period was 7.3 years. The median linear aneurysm expansion rate was 2.0 mm/year (range 0 to 8.4). Three patients experienced aneurysm rupture (7.3%) which resulted in 1 patient'death. Thirteen patients underwent aneurysm repair (31.7%) and 1 patient died postoperatively (7.7%). The survival rate at 10-year follow-up was 59.0%. The survival rate free from aneurysm rupture and repair at 10-year follow-up was 69.9%. The median time for occurrence of aneurysm rupture was 4.9 years (range 1.8 to 10.5) and the need for aneurysm repair was 4.5 years (range 1.4 to 10.4). CONCLUSIONS: The fate of very small AAA is to slowly enlarge in size, sometimes threatening the patient's life. These observations underline the importance of continuous surveillance and the potential benefits of any medical treatment in this patient population.     

Gold standard for sternectomies and plastic reconstructions after resections for primary or secondary sternal neoplasms

Background Between January 1980 and December 1999, 88 patients underwent thesurgical resection of sternal tumors: 30 primary malignant tumors, 28 local relapses or metastases from breast carcinomas, 16 other types of tumor, and 14 radionecroses. Methods The sternectomies were total in 8 cases, subtotal in 32, and partial in 48. Prosthetic materials covered by flaps of myocutaneous or muscle tissue were used in 55 patients, prosthetic material alone in 13, myocutaneous or muscle flaps alone in 5, and other techniques in the remaining 15. The resection was radical in 78 cases and palliative in the other 10 Results Forty-eight of the subjects who underwent radical surgery were alive and disease free at the end of the follow-up period. The expected 10-year survival of the patients treated for primary tumors is approximately 85% (Kaplan-Meier), and that of the patients with relapsing breast carcinomas is the same as after 5 years (41.8%). Conclusions In our experience, the treatment of neoplasms by means of a broad sternal resection followed by a reconstruction based on the use of prosthetic materials is an effective and safe solution that considerably improves the quality of life and makes it possible to perform curative broad radical resections in the case of primary sternal resections. Presented at the 54th Annual Cancer Symposium of the Society of Surgical Oncology, Washington, DC, March 15–18, 2001.