Generation of a strong mutator phenotype in yeast by imbalanced base excision repair.

Increased spontaneous mutation is associated with increased cancer risk. Here, by using a model system, we show that spontaneous mutation can be increased several hundred-fold by a simple imbalance between the first two enzymes involved in DNA base excision repair. The Saccharomyces cerevisiae MAG1 3-methyladenine (3MeA) DNA glycosylase, when expressed at high levels relative to the apurinic/apyrimidinic endonuclease, increases spontaneous mutation by up to approximately 600-fold in S. cerevisiae and approximately 200-fold in Escherichia coli. Genetic evidence suggests that, in yeast, the increased spontaneous mutation requires the generation of abasic sites and the processing of these sites by the REV1/REV3/REV7 lesion bypass pathway. Comparison of the mutator activity produced by Mag1, which has a broad substrate range, with that produced by the E. coli Tag 3MeA DNA glycosylase, which has a narrow substrate range, indicates that the removal of endogenously produced 3MeA is unlikely to be responsible for the mutator effect of Mag1. Finally, the human AAG 3-MeA DNA glycosylase also can produce a small (approximately 2-fold) but statistically significant increase in spontaneous mutation, a result which could have important implications for carcinogenesis.

Heme from Alzheimer's brain inhibits muscarinic receptor binding via thiyl radical generation.

An endogenous inhibitor (< 3500 Da) of antagonist binding to the muscarinic acetylcholine receptor (mAChR) has been reported to be elevated 3-fold in Alzheimer's disease (AD) brain. This endogenous inhibitor was found to require the presence of reducing agents such as reduced glutathione (GSH) for optimal activity. In the presence of GSH, the inhibitor was shown to generate thiyl radicals which irreversibly inhibited the mAChR. We now report that the inhibitor contains free heme, a well-established source of oxidative stress capable of generating free radicals and causing neurotoxicity. While FeSO4, microperoxidase and hemin all inhibited antagonist binding to the mAChR, only hemin shared the inhibitor's requirement for GSH. Both the free radical scavengers Trolox and Mn2+, and the metal chelator, EDTA, blocked the activity of the endogenous AD inhibitor and of hemin. Heme oxygenase-1 (HO-1) markedly reduced the activity of both the endogenous AD inhibitor and hemin, indicating that the endogenous inhibitor contains heme. Mass spectrometric analysis confirmed the presence of free heme and heme fragments in fractions of the endogenous AD inhibitor. The antioxidants estrogen, vitamin E and vitamin C all protected the mAChR from irreversible inhibition by the endogenous inhibitor or hemin. These antioxidants may function to protect the integrity of the mAChR in vivo and may have therapeutic potential in AD where free heme could be a source of oxidative stress.

The role of preoperative factor V Leiden screening in different geographic populations.

Patients harboring a specific mutation in the coagulation factor V gene have been identified as being at significantly increased risk for venous thrombosis. A simple genetic test that identifies carriers of this mutation (the factor V Leiden allele) is available and may have utility in various clinical settings, including preoperative risk assessment for thromboembolic complications. In this regard, it is generally agreed that prospective studies addressing the role of preoperative factor V Leiden mutational analysis are needed to clearly define the clinical prognostic/diagnostic significance of the presence of this mutation in surgical patients. This report questions the role that population dynamics (genetic and environmental backgrounds of individual populations) plays in the analysis of factor V genotypic data in relation to postsurgical thromboembolic complications. We have determined that the frequency of individuals carrying the factor V Leiden allele is 7.9 per cent for our South Central Pennsylvania population (395 wild type, 32 heterozygotes, 2 homozygotes) using a polymerase chain reaction-restriction fragment length polymorphism technique that specifically detects the factor V Leiden mutation. This baseline population information is useful from both a clinical and a basic science viewpoint. However, considering the various unknown genetic and environmental differences between geographically distinct populations, the significance of this result, in terms of clinical management of our surgical patients, is yet to be determined.

Endogenous Alzheimer's brain factor and oxidized glutathione inhibit antagonist binding to the muscarinic receptor.

An endogenous inhibitor (< 3,500 Da) of antagonist binding to the muscarinic acetylcholine receptor has been extracted from Alzheimer's disease (AD) brain with trifluoracetic acid. Oxidized glutathione, (GSSG) has also been found to inhibit antagonist binding to the receptor. However, in its reduced form, glutathione (GSH) like other reducing agents, markedly enhances the inhibitory effect of both GSSG and the endogenous AD inhibitor. EDTA and the free radical scavengers Mn(2+) and Trolox, a vitamin E analog, block the action of the endogenous AD inhibitor but not of GSSG in the presence of GSH. Further, while GSSG inhibition is reversible, the action of the endogenous AD inhibitor is irreversible, consistent with a free radical mechanism. The enhancement of endogenous AD inhibitor activity by GSH suggested that GSH may be involved in formation of the free radical generated by the inhibitor. The glutathione thiyl radical is shown to inhibit antagonist binding to the receptor and is, therefore, a good candidate for the free radical formed by the endogenous AD inhibitor. The ability of Trolox to block the reduction in muscarinic receptor binding caused by the endogenous AD inhibitor is encouraging and suggests that free radical scavengers, such as vitamin E, may have a potential therapeutic role in AD by protecting the integrity of the muscarinic receptor.

Medical coverage for multievent sports competition: a comprehensive analysis of injuries in the 1994 Star of the North Summer Games.

OBJECTIVE: To determine the incidence and type of requests for medical assistance and the treatment required in 21 sports at the 1994 Star of the North Summer Games and to develop a plan, based on these findings, for efficient allocation of medical supplies and staff. DESIGN: We reviewed our experience with a large multisport amateur athletic event and analyzed the pattern of injuries for participants in the various sports. MATERIAL AND METHODS: Injury evaluation forms and medical supply kits were given to the health-care volunteers, who received preliminary instructions on classifications and definitions of injuries and on appropriate completion of the forms. When a medical contact occurred, an evaluation form was completed. The data from these forms were subsequently compiled and analyzed. RESULTS: Of 6,243 athletes who participated in the 1994 Star of the North Summer Games, 55 (0.88%) received medical attention (2 officials also required medical assistance). The sports with the greatest number of medical contacts were soccer and track and field--31 and 16 contacts for medical assistance, respectively. The lower extremities were the anatomic site most frequently involved in injury (62% of the medical contacts). The most common types of injury were contusions, strains, and sprains. CONCLUSION: Because few injuries were sustained and most were of minor severity, basic medical supplies (such as ice bags and compression wraps) were sufficient. For locations with a scarcity of medical personnel, a triage system can be established in which athletic trainers or registered nurses manage the initial assessments and refer cases, as needed, to physicians for specialized care. An effective communication system can also considerably reduce volunteer hours.

TRISS unexpected survivors--a statistical phenomenon or a clinical reality?

Data from patients treated in Pennsylvania-accredited trauma centers during 1989 were analyzed. TRISS expected and unexpected survivors (1.6% of all survivors) differed in many ways. Unexpected survivors were more than twice as likely to have been transferred from a nondesignated trauma center (45.8% vs. 22.8%, p < 0.001). Unexpected survivors had significantly higher frequencies of motor vehicle injuries (56.2% vs. 38.3%, p < 0.001), pedestrian injuries (9.6% vs. 5.4%, p < 0.01), and gunshot wounds (7.3% vs. 4.7%, p < 0.01). Expected survivors were injured more frequently in falls (26.1% vs. 10.8%, p < 0.001) and were less frequently male (64.5% vs. 75%, p < 0.001). Unexpected survivors had significantly longer average hospital stay (29.6 s vs. 9.3 days, p < 0.001) and more frequent (98.8% vs. 36.8%, p < 0.001) and longer average stays in the ICU (13.3 s vs. 4.1 days, p < 0.001). The percentage of unexpected survivors discharged to rehabilitation centers (61.9%) was significantly greater than that for expected survivors (8.7%), (p < 0.001). Unexpected survivors were more frequently judged "completely dependent" in five measures of functional disability than expected survivors. We conclude that unexpected survivors are a seriously injured and clinically relevant patient set, not just a statistical phenomenon.

Comparison of a hydrocolloid dressing and silver sulfadiazine cream in the outpatient management of second-degree burns.

The purpose of this prospective randomized study was to evaluate the use of an occlusive hydrocolloid dressing (Duoderm hydroactive, Squibb) and silver sulfadiazine (Silvadene, Marion) cream in the outpatient management of second-degree burns. The inclusion criteria consisted of burns less than 15% total body surface area that were evaluated within 24 hours of injury and did not require hospital admission. Fifty patients were randomly assigned after having been screened through a list of seven exclusion criteria. On initial evaluation the burns were photographed and screened for causative agent, location, size, depth, tetanus status, and presence of associated burns and injuries. Patients were seen in followup at least biweekly and evaluated for wound bed healing, wound margin healing, pain, number of dressing changes between visits, and ease of dressing application and removal. On final evaluation the burns were photographed and inspected for appearance of the healed burn, repigmentation, wound contraction, approximate time for dressing change, patient compliance, limitation of activity, overall impression of the treatment, and number of days for complete healing. Results were compared using a two-tailed t-test with p less than 0.01. Both groups were statistically similar in age, sex, and size. Duoderm-treated burns had statistically significantly better wound healing, repigmentation, less pain, fewer dressing changes, less time for dressing changes, and less cost. Duoderm-treated patients had statistically significantly less limitation of activity, better patient compliance, greater patient comfort, better overall acceptance, and felt the treatment was more aesthetically pleasing. The results reveal that the Duoderm Hydroactive dressings are superior to Silvadene cream in the outpatient management of second-degree burns.

Measured energy expenditure in severe head trauma.

Metabolic profiles of 20 patients admitted to the Conemaugh Valley Memorial Hospital Trauma Unit from July 1987 through June 1988 with Glasgow Coma Scale Scores of 7 or less were retrospectively reviewed. Analysis of Injury Severity Scale (ISS) determinations indicated that all patients had major closed head injury, and associated injuries were minor in nature. No significant co-morbid disease states were present in this patient population. All patients required mechanical ventilatory support, and within 48 hours of admission measurements of oxygen consumption (VO2), carbon dioxide production (VCO2) and respiratory quotient (VCO2/VO2) were made using a Beckman Metabolic Measurement Cart which employs indirect closed calorimetry to assess resting energy expenditure (REE). When predicted values of REE and VO2 (derived from the Harris-Benedict equation) were compared to actual measured data, the percentage increase over predicted was 160 +/- 37 (p less than 0.005) and 166 +/- 43 (p less than 0.005), respectively. Based on these observations it is evident that patients with severe head trauma are physiologically in an early hypermetabolic state, and that values of REE derived from standard formula are grossly inaccurate, leading to inadequate nutritional support.