Characteristics of mammary mitochondria in lines of mice genetically divergent for milk production

The purpose of this study was to determine the relationship of mitochondrial proliferation and ATP production to milk production in two lines of mice that were genetically divergent for milk production. Milk production differed between high production and low production lines by .8 phenotypic standard deviations as determined by cross-fostered litter weight gain from 1 to 12 d postpartum. Mammary weight, mammary total DNA, and RNA:DNA ratio were greater in glands of high line mice. Mammary DNA and protein, expressed per gram mammary tissue, were similar between lines. Mammary mitochondrial mass per gland differed after six generations of divergent selection. Rates of succinate-supported ATP production and ADP:O of isolated mitochondria differed, but the rate of pyruvate-supported ATP production did not differ between lines. Differences between selection lines in mitochondrial mass and in the efficiency of succinate use for support of ATP production were probable consequences of selection for divergent milk production.     

Understanding the relationship between relative and absolute risk

BACKGROUND: Relative risks are the most common statistics used to quantify the risk of mortal or morbid outcomes associated with different patient groups and therapeutic interventions. However, absolute risks are of greater value of both patient and physician in making clinical decisions. METHODS: The relationship between relative and absolute risks is explained using graphical aids. A program to estimate absolute risks from relative risks is available on the internet (see ftp://ftp.vanderbilt.edu/pub/biostat/absrisk+ ++.txt). This program uses a competing hazards model of morbidity and mortality to derive these estimates. RESULTS: When a patient's absolute risk is low, it can be approximated by multiplying her relative risk by the absolute risk in the reference population. This approximation fails for higher absolute risks. The relationship between relative and absolute risk can vary dramatically for different diseases. This is illustrated by breast cancer morbidity and cardiovascular mortality in American women. The accuracy of absolute risk estimates will be affected by the accuracy of relative risk estimates, by the appropriateness of the reference groups used to calculate relative risks, by the stability of cross-sectional, age-specific morbidity and mortality rates over time, by the influence of individual risk factors on multiple causes of mortality, and by the extent to which relative risks may vary over time. CONCLUSIONS: Valid absolute risk estimates are valuable when making treatment decisions. They can often be obtained over time intervals of 10 to 20 years when the corresponding relative risk estimates have been accurately determined.     

Cerebral protection by intermittent reperfusion during temporary focal ischemia in the rat

Temporary arterial occlusion has been routinely used as an adjunct in intracranial aneurysm surgery. This has commonly been performed using a protocol of multiple short periods of occlusion alternating with periods of restoration of normal circulation. Recently, the logical basis of this method has come under scrutiny. There is extensive experimental evidence to suggest that repetitive, brief periods of global ischemia may cause more severe cerebral injury than an equivalent single period of global ischemia. Only recently has this issue begun to be addressed with regard to focal ischemia. Hence, despite the common use of temporary clipping, little experimental data are available regarding the ischemic consequences of temporary arterial occlusion with periods of reperfusion versus uninterrupted temporary occlusion. To investigate this issue, a protocol of occlusion/reperfusion that simulates the temporal profile that occurs during surgery was performed in a rat model of focal ischemia. Sixteen anesthetized Sprague-Dawley rats were divided into two groups. The animals in Group I underwent 60 minutes of uninterrupted middle cerebral artery occlusion and the animals in Group II were subjected to six separate 10-minute occlusion periods with 5 minutes of reperfusion between occlusions. Histopathological analysis was performed 72 hours postischemia. Group I had significantly increased mean infarction volumes (50.0 +/- 12.1 mm3) compared to Group II (8.7 +/- 3.1 mm3) (p = 0.008). Injuries in Group I occurred in both the cortex and striatum, whereas Group II showed only striatal injuries. Furthermore, the extent of the injuries in Group II was less severe, characterized by ischemic neuronal injury rather than frank infarction. The results indicate that intermittent reperfusion is neuroprotective during temporary focal ischemia and support the hypothesis that intermittent reperfusion is beneficial if temporary clipping is required during aneurysm repair.     

The North Carolina High School Athletic Injury Study: design and methodology

PURPOSE: Organized interscholastic athletics are an integral part of the educational program at almost every school level. With this growing popularity of sports and their inclusion in more public school programs, it becomes increasingly apparent that additional consideration must be given to the injury problem associated with sport. The North Carolina High School Athletic Injury Study (NCHSAIS) was undertaken to identify patterns of injury among male and female athletes in North Carolina high schools participating in any of 12 sports. Specific aims are to measure the incidence, severity and etiology of injuries; to determine the relationship of demographic factors and protective equipment, exposure to play, and school characteristics to injuries; to study the relationship of coaches' training and experience to injury occurrence; and to compare the incidence and severity of injury among female and male athletes in the same or comparable sports. METHODS: A two-stage cluster sample of 100 high schools in North Carolina was selected for this 4-yr prospective study. RESULTS: Participation by the initial sample or a random replacement was achieved for 91 of the 100 schools. Nonresponse occurred at multiple levels of the sample for this study, and the weekly participation form posed the greatest respondent burden. CONCLUSIONS: The NCHSIAS offers a successful methodology for addressing sports injuries. In this paper we describe the design, methodology, and implementation issues that emerge in conducting a large scale epidemiological study in a population of high school athletes.     

Can duplex scan arterial mapping replace contrast arteriography as the test of choice before infrainguinal revascularization?

PURPOSE: Arteriography is the diagnostic test of choice before lower extremity revascularization, because it is a means of pinpointing stenotic or occluded arteries and defining optimal sites for the origin and termination of bypass grafts. We evaluated whether a duplex ultrasound scan, used as an alternative to arteriography, could be used as a means of accurately predicting the proximal and distal anastomotic sites in patients requiring peripheral bypass grafts and, therefore, replace standard preoperative arteriography. METHODS: Forty-one patients who required infrainguinal bypass grafts underwent preoperative duplex arterial mapping (DAM). Based on these studies, an observer blinded to the operation performed predicted what operation the patient required and the best site for the proximal and distal anastomoses. These predictions were compared with the actual anastomotic sites chosen by the surgeon. RESULTS: Whether a femoropopliteal or an infrapopliteal bypass graft was required was predicted correctly by means of DAM in 37 patients (90%). In addition, both anastomotic sites in 18 of 20 patients (90%) who had femoropopliteal bypass grafts and 5 of 21 patients (24%) who had infrapopliteal procedures were correctly predicted by means of DAM. CONCLUSION: DAM is a reliable means of predicting whether patients will require femoropopliteal or infrapopliteal bypass grafts, and, when a patient requires a femoropopliteal bypass graft, the actual location of both anastomoses can also be accurately predicted. Therefore, DAM appears able to replace conventional preoperative arteriography in most patients found to require femoropopliteal reconstruction. Patients who are predicted by means of DAM to require crural or pedal bypass grafts should still undergo preoperative contrast studies to confirm these results and to more precisely locate the anastomotic sites.