A system for assaying homologous recombination at the endogenous human thymidine kinase gene.

A system for assaying human interchromosomal recombination in vitro was developed, using a cell line containing two different mutant thymidine kinase genes (TK) on chromosomes 17. Heteroalleles were generated in the TK+/+ parent B-lymphoblast cell line WIL-2 by repeated exposure to the alkylating nitrogen mustard ICR-191, which preferentially causes +1 or -1 frameshifts. Resulting TK-/- mutants were selected in medium containing the toxic thymidine analog trifluorothymidine. Mutations were characterized by exon-specific polymerase chain reaction amplification and direct sequencing. In two lines, heterozygous frameshifts were located in exons 4 and 7 of the TK gene separated by approximately 8 kilobases. These lines undergo spontaneous reversion to TK+ at a frequency of less than 10(-7), and revertants can be selected in cytidine/hypoxanthine/aminopterin/thymidine medium. The nature and location of these heteroallelic mutations make large deletions, rearrangements, nondisjunction, and reduplication unlikely mechanisms for reversion to TK+. The mode of reversion to TK+ was specifically assessed by DNA sequencing, use of single-strand conformation polymorphisms, and analysis of various restriction fragment length polymorphisms (RFLPs) linked to the TK gene on chromosome 17. Our data suggest that a proportion of revertants has undergone recombination and gene conversion at the TK locus, with concomitant loss of frameshifts and allele loss at linked RFLPs. Models are presented for the origin of two recombinants.     

Cardiac Surgery in Nonagenarians

A bstract Objectives and Background : The purpose of this study was to document our initial experience with patients 90 years of age and older and to determine whether cardiac surgery is justified in this age group. Cardiac surgery in octogenarians has proven to be a successful and worthwhile procedure. A small group of nonagenarians with severe coronary artery disease (CAD) and aortic valve disease refractory to medical therapy have been considered for surgery. Methods : Fourteen patients aged 90 or more underwent cardiac surgery for symptomatic CAD or aortic valvular disease refractory to medical therapy. Eight patients underwent isolated coronary artery bypass grafting (CABG) and six patients underwent aortic valve replacement (AVR). All patients were in NYHA Class IV preoperatively. Results : Hospital mortality occurred in one patient (7%). Hospital morbidity occurred in 10 patients (71%) and included 7 cardiac, 5 neurological, 1 gastrointestinal, 1 infectious, and 1 pulmonary event. All survivors left the hospital symptomatically improved. The mean length of stay was 26 days. Four CABG patients went on to die at a mean of 2 years and 2 months, and 3 remain alive at a mean of 2 years and 4 months. Three AVR patients expired at a mean of 3 years and 4 months, and 3 remain alive at 4 years and 1 month. Conclusions : Cardiac surgery in carefully selected nonagenarians is justified and can be performed with acceptable results.     

Avoiding complications in arthroscopic subacromial space and instability surgery

Arthroscopic shoulder surgery has become a safe tool for evaluation and treatment of a wide range of shoulder problems with few complications. With ever-improving technology (and commitment to motor skill development among arthroscopists), we can expect to maintain this low rate despite increasing procedure complexity. Avoiding complications in arthroscopic shoulder surgery requires careful preoperative planning, judicious patient selection, a thorough understanding of arthroscopic anatomy, and facility with arthroscopic techniques.     

Efficacy and safety of xaliproden in amyotrophic lateral sclerosis: results of two phase III trials.

Amyotrophic lateral sclerosis (ALS) is a relentlessly progressive and fatal motor neuron disease. We carried out two randomized, double-blind, placebo-controlled, multi-centre, multi-national studies with xaliproden (a drug with neurotrophic effect) to assess drug efficacy and safety at two doses. Patients with clinically probable or definite ALS of more than 6 months and less than 5 years duration were randomly assigned to placebo, 1 mg or 2 mg xaliproden orally once daily as monotherapy in Study 1 (n=867); or to the same regimen with addition of riluzole 50 mg bid background therapy in Study 2 (n=1210 patients). The two primary endpoints were defined as: 1. Time to death, tracheostomy, or permanent assisted ventilation (DTP), and 2. Time to vital capacity (VC)<50% or DTP before (log-rank test) and after adjustment using a Cox proportional hazard model for prespecified prognostic factors. Secondary endpoints were rates of change of various functional measures. In Study 1, primary outcome measures did not reach statistical significance. For the 2 mg group, for time to VC<50% analysis (without DTP) a significant 30% RRR was obtained (95% confidence interval [CI]: 8.46, P=0.009). In Study 2, no significant results were obtained. However, there was a trend in favour of add-on 1 mg dose xaliproden vs. placebo (RRR 15% [-6.31, ns] for time to VC<50%; RRR 12% [CI: -6.27, ns] for time to VC<50% or DTP). Adjusted RR ratios were consistently more favourable for the xaliproden groups. Tolerability was good, and dose-dependent side effects were largely associated with the serotonergic properties of xaliproden. An effect of xaliproden on functional parameters, especially VC, was noted. Although this effect did not reach statistical significance, xaliproden had a small effect on clinically noteworthy aspects of disease progression in ALS.     

Long-term retrospective studies on the CT-scan, CAD/CAM, one-stage surgery hydroxyapatite-coated subperiosteal implants, including human functional retrievals.

The subperiosteal implant has long been regarded as the most successful, predictable, and versatile of all implant systems. In some cases, however, anatomic morphology and surgical technique present certain limitations for the subperiosteal procedure. Through CAD/CAM multiplanar diagnostic imaging, not only have we been able to eliminate the first stage of the surgical procedure, but we have expanded the capabilities and versatility of the subperiosteal procedure. In addition, coating the subperiosteal implant frame with hydroxyapatite has allowed the achievement of bony union, thus increasing the long-range prognosis of the individual case.     

Pain intensity measurement in chronic low back pain.

This study investigated the psychometric properties of eight pain intensity measures used with chronic low back pain patients. All measures were similar in terms of scale distribution and rates of incorrect responses, with all scales apart from the Pain Rating Index significantly correlated. Principal axis factoring of data from 92 patients indicated the presence of one general factor on which all pain intensity measures except the Pain Rating Index loaded. The 101-point Numeric Rating Scale and the Box Scale had the strongest relationship, with loadings of 0.90. The Numeric Rating Scale and the Box Scale appear to be the scales of choice for the measurement of pain intensity in the low back pain patient.     

Proliferative activity of colonic mucosa at different distances from primary adenocarcinoma as determined by the presence of statin: A nonproliferation-specific nuclear protein

The field change is one hypothesis concerning the development of colorectal carcinoma. Removal of a carcinoma without its entire surrounding altered mucosa may result in the development of a recurrence. S44, a monoclonal antibody directed against statin, a nuclear protein expressed in nonproliferating cells in either a quiescent or senescent state, was used to determine the rate of cell growth in colorectal mucosa at different distances from carcinomas. The specimens of 18 patients undergoing resection of a colorectal carcinoma were immediately opened after operation, and strips of mucosa were taken at distances of 1 cm, 5 cm, and 10 cm from the carcinoma. For each location, 10 longitudinally oriented crypts were evaluated for statin-positive cells identified by the presence of a dark brown peroxidase-conjugated antibody reaction product. The average percentage of statin-positive cells per crypt was significantly lower at a 1-cm distance from the carcinoma compared with the mucosa located 5 and 10 cm from the carcinoma (20.89±4.33 at 1 cm, 32.41±5.27 at 5 cm, and 34.23±6.45 at 10 cm). None of the calculated parameters showed any significant difference between the 5-cm and 10-cm locations. The fact that the proliferation rate of the mucosal cells returns to the normal level at 5 cm from the margin of the carcinoma suggests that cells located within this distance still retain proliferative potential even though they are morphologically indistinguishable from their normal counterparts. We conclude that failure to remove this transitional, potentially proliferative mucosa may result in subsequent development of anastomotic or perianastomotic recurrences.This study was conducted with support from the Sir Mortimer B. Davis-Jewish General Hospital Foundation and the American Physician Fellowship and with grants to Eugenia Wang from the Medical Research Council of Canada and from the National Institute on Aging of the National Institutes of Health of the U.S.A.