Effect of exercise, heat stress and dehydration on myocardial performance.

BACKGROUND: Myocardial dysfunction is a well-documented outcome of extended periods of high cardiac output. Whether similar effects occur during firefighting, an occupation characterized by repeated periods of work compounded by dehydration and heat stress, is uncertain. AIMS: To investigate the independent and combined effects of moderate heat stress and dehydration on indicators of myocardial performance following intermittent, submaximal treadmill exercise while wearing personal protective equipment (PPE). METHODS: Twelve aerobically fit young men (age 21.5±2.6 years; maximal oxygen uptake [VO2max] 60.3±4.4ml kg(-1) min(-1)) performed intermittent treadmill walking exercise consisting of three 20min bouts at an intensity of ~40% VO2max separated by two periods of rest in four different conditions in random order: (i) no heat stress-euhydrated, (ii) heat stress-euhydrated (heat stress created by wearing PPE, (iii) no heat stress-dehydrated and (iv) heat stress-dehydrated. We measured core temperature by a telemetric gastrointestinal pill. We determined cardiac variables by standard echocardiographic techniques immediately before and ~30min after exercise. RESULTS: We recorded no significant changes in markers of systolic (ejection fraction, shortening fraction, tissue Doppler-S) or diastolic (mitral peak E velocity, tissue Doppler-E' and E/E') function following exercise in any of the four conditions. CONCLUSIONS: In this model of exercise designed to mimic the work, heat stress and dehydration associated with firefighting activities, we observed no negative effects on myocardial inotropic or lusitropic function.

Arthrofibrosis of the knee following a fracture of the tibial plateau.

The aim of this study was to report the incidence of arthrofibrosis of the knee and identify risk factors for its development following a fracture of the tibial plateau. We carried out a retrospective review of 186 patients (114 male, 72 female) with a fracture of the tibial plateau who underwent open reduction and internal fixation. Their mean age was 46.4 years (19 to 83) and the mean follow-up was16.0 months (6 to 80). A total of 27 patients (14.5%) developed arthrofibrosis requiring a further intervention. Using multivariate regression analysis, the use of a provisional external fixator (odds ratio (OR) 4.63, 95% confidence interval (CI) 1.26 to 17.7, p = 0.021) was significantly associated with the development of arthrofibrosis. Similarly, the use of a continuous passive movement (CPM) machine was associated with significantly less development of arthrofibrosis (OR = 0.32, 95% CI 0.11 to 0.83, p = 0.024). The effect of time in an external fixator was found to be significant, with each extra day of external fixation increasing the odds of requiring manipulation under anaesthesia (MUA) or quadricepsplasty by 10% (OR = 1.10, p = 0.030). High-energy fracture, surgical approach, infection and use of tobacco were not associated with the development of arthrofibrosis. Patients with a successful MUA had significantly less time to MUA (mean 2.9 months; sd 1.25) than those with an unsuccessful MUA (mean 4.86 months; sd 2.61, p = 0.014). For those with limited movement, therefore, performing an MUA within three months of the injury may result in a better range of movement. Based our results, CPM following operative fixation for a fracture of the tibial plateau may reduce the risk of the development of arthrofibrosis, particularly in patients who also undergo prolonged provisional external fixation.

An oral disease prevention program for patients receiving radiation and chemotherapy.

Thirteen years of treating more than 2,950 patients at the National Institute of Dental Research clinic have shown that a variety of potential oral sequelae associated with cancer therapy can be prevented, reduced in severity, or palliatively alleviated when the dental team has an opportunity to participate in the patient's care. The keystone of this success is based on early referral of the patient for dental consultation, treatment before the initiation of cancer therapy, and a well-defined orientation program to inform patients and their families about the difficulties they may experience. Meticulous attention to oral microbial control, prophylactic use of fluoride gels, and palliative treatment of soft tissue lesions may significantly reduce the oral morbidity associated with radiation and cytotoxic chemotherapy. Diligent personal oral health care and frequent dental recall appointments are recommended for the remainder of the patient's life. It has been our experience that patients who are not followed closely after irradiation therapy have an increased incidence of caries as a result of noncompliance with preventive regimens. The ethical and medicolegal responsibility to fully inform the patient of these recommendations lies with both the medical and dental personnel at the facility providing the radiation-chemotherapy service. The general dentist shares the responsibility for continuity of long-term oral health care.

Normal liver chromatin contains a firmly bound and larger protein related to the principal cytosolic target polypeptide of a hepatic carcinogen.

A 14,000-dalton polypeptide was previously reported to be the principal protein target of the carcinogen N-2-fluorenylacetamide (2-acetylaminofluorene) in liver cytosol at the start of hepatocarcinogenesis in rats. The 14,000-dalton polypeptide was purified to homogeneity according to gel electrophoreses in both NaDodSO4-containing medium and acetic acid/urea and also by immunogenicity. An immunologically related form of the cytosolic target polypeptide has now been found to be present in the nuclei of normal rat liver as a 17,500-dalton polypeptide that is firmly and ionically bound to chromatin. Serial salt extractions of isolated liver nuclei or chromatin at 0.15 and 0.35 ionic strengths fail to dissolve the bound polypeptide, according to electrophoretic transfer immunoblot analyses. Most of the 17,500-dalton polypeptide is extracted at 0.65 ionic strength, the remainder at 1.2, and none at 2.0, nor thereafter in 8 M urea. In addition, short-term digestion of purified liver nuclei with micrococcal nuclease solubilizes the 17,500-dalton polypeptide. All three protocols also solubilize low levels of intermediate 17,500- to 14,000-dalton species, the latter size being the same as that of the cytosolic protein target of the carcinogen. The presence of protease inhibitors during the isolations and extractions of the nuclei and chromatin reduces the amounts of these smaller polypeptides. In normal rat liver only nuclei and cytoplasm of hepatocytes contain reactive antigen according to peroxidase-antiperoxidase immunohistochemistry, staining most intensely perilobularly, less in the lobular midzone, and least centrilobularly. The nuclei of the perilobular hepatocytes constitute the strongest staining compartment within all of normal liver. Of 22 nonhepatic tissues of normal rats, 16 contain relatively few cells with immunoreactive cytoplasm. Nonhepatic nuclear antigen is present only in villar crest cells of duodenum (which are normally exposed to liver bile), also having cytoplasmic antigen as well. Five kinds of evidence appear to connect the chromatin-bound 17,500-dalton polypeptide of normal liver nuclei to the cytosolic 14,000-dalton polypeptide that is the principal target of the carcinogen early during hepatocarcinogenesis in rats. The present findings indicate a direct connection between a chromosomal protein and the immediate principal cytosolic protein target of a carcinogen.