PMC:2493521 / 20667-24583 JSONTXT

{"project":"2_test","denotations":[{"id":"18347928-1480765-20694283","span":{"begin":770,"end":774},"obj":"1480765"},{"id":"18347928-12694381-20694284","span":{"begin":851,"end":855},"obj":"12694381"},{"id":"18347928-2905309-20694285","span":{"begin":871,"end":875},"obj":"2905309"},{"id":"18347928-671036-20694286","span":{"begin":893,"end":897},"obj":"671036"},{"id":"18347928-455043-20694287","span":{"begin":906,"end":910},"obj":"455043"},{"id":"18347928-8515219-20694288","span":{"begin":1002,"end":1006},"obj":"8515219"},{"id":"18347928-8515212-20694289","span":{"begin":1160,"end":1164},"obj":"8515212"},{"id":"18347928-11706078-20694290","span":{"begin":1262,"end":1266},"obj":"11706078"},{"id":"18347928-17204935-20694291","span":{"begin":1282,"end":1286},"obj":"17204935"},{"id":"18347928-12694381-20694292","span":{"begin":1300,"end":1304},"obj":"12694381"},{"id":"18347928-2427740-20694293","span":{"begin":1321,"end":1325},"obj":"2427740"},{"id":"18347928-3629-20694294","span":{"begin":1345,"end":1349},"obj":"3629"},{"id":"18347928-14559355-20694295","span":{"begin":1369,"end":1373},"obj":"14559355"},{"id":"18347928-17045977-20694296","span":{"begin":1387,"end":1391},"obj":"17045977"},{"id":"18347928-14960286-20694297","span":{"begin":1407,"end":1411},"obj":"14960286"},{"id":"18347928-7815079-20694298","span":{"begin":1430,"end":1434},"obj":"7815079"},{"id":"18347928-15921819-20694299","span":{"begin":1791,"end":1795},"obj":"15921819"},{"id":"18347928-17204935-20694300","span":{"begin":1811,"end":1815},"obj":"17204935"},{"id":"18347928-12694381-20694301","span":{"begin":1829,"end":1833},"obj":"12694381"},{"id":"18347928-7788642-20694302","span":{"begin":1849,"end":1853},"obj":"7788642"},{"id":"18347928-12694381-20694303","span":{"begin":2137,"end":2141},"obj":"12694381"},{"id":"18347928-17204935-20694304","span":{"begin":2295,"end":2299},"obj":"17204935"},{"id":"18347928-10192212-20694305","span":{"begin":2501,"end":2505},"obj":"10192212"},{"id":"18347928-7815079-20694306","span":{"begin":3597,"end":3601},"obj":"7815079"}],"text":"Dedication to short postmortem interval\nSince the inception of the Brain Donation Program, the overriding organizing principle has been that the brain must be removed and processed as rapidly as possible. The median postmortem interval (PMI), defined as the time elapsing between death and brain removal, for all 1042 of our necropsied subjects, is 2.75 h (mean 3.92; standard deviation 5.11; range 1–70). There is a moderately extensive literature on the relationship between PMI and brain tissue quality, which will not be exhaustively summarized here, but it is apparent that deterioration of molecular entities after death varies widely depending on what is being measured. Highly volatile energy storage molecules such as ATP disappear within minutes (Ravid et al. 1992), catecholamines drop precipitously within the first few hours (Hynd et al. 2003; Palmer et al. 1988; Spokes and Koch 1978; Spokes 1979) while high-molecular-weight DNA may be stable for up to 20 days after death (Ludes et al. 1993). Some enzyme activities actually increase after death, for example, creatine kinase activity is increased more than ten-fold at 2 h postmortem (Karkela 1993). Most protein and RNA species are surprisingly stable up to 40–50 h postmortem (Cummings et al. 2001; Ferrer et al. 2007; Hynd et al. 2003; Johnson et al. 1986; McGeer and McGeer 1976; Preece and Cairns 2003; Stan et al. 2006; Tomita et al. 2004; Vonsattel et al. 1995). As the majority of biomedical research is done on proteins and RNA, this might suggest that postmortem intervals up to 36 or even 48 h might be sufficient for authoritative studies, but there is also evidence that appreciable numbers of specific proteins and RNA transcripts show large PMI-dependent reductions, even within the first 4–8 h (Catts et al. 2005; Ferrer et al. 2007; Hynd et al. 2003; Pardue et al. 1994). Variability in postmortem preservation of different mRNA transcripts may be due to differing tertiary structures or normal physiological half-lives, which range from minutes to days. For example, c-fos mRNA has a half-life of 15 min while that for globin mRNA is 50 h (Hynd et al. 2003). Some intensely-studied proteins are markedly degraded within the first 4–8 h of death, including α-synuclein and sarkosyl-insoluble tau (Ferrer et al. 2007a). The postmortem integrity of post-translational protein modifications is largely unknown, although it has been reported that tau protein is dephosphorylated within 30 min after death (Gartner et al. 1998).\nWe have evaluated RNA integrity in 157 cases (mean PMI 3.1 h) from our brain bank using qualitative RNA agarose gel electrophoresis. The presence of two clearly distinct and dominant bands, corresponding to the ribosomal 28S and 18S RNA species, as recorded by a single observer blinded to all case data, was used to define acceptable RNA. Loss or smearing of these bands was used to indicate degradation levels making the sample unsuitable for study. Using these criteria, 133/157, or 82% of our samples were suitable for RNA studies and were used successfully. Comparison of PMI’s from cases giving suitable and unsuitable RNA showed a significantly shorter mean PMI in the suitable samples (2.75 vs 3.5 h, two-tailed unpaired t-test; P = 0.04). These results suggest that even small differences in PMI within a rapid autopsy program can have a significant effect on RNA integrity. As a further comparison, programs with average PMI’s of 16 h or more have reported one-third to one-half of cases have RNA suitable for molecular research methods (Vanderburg et al. 2005; Vonsattel et al. 1995) whereas we have found 82% of cases suitable. These results and the brief literature review presented here indicate that a short PMI clearly allows optimal use of the resource but that all postmortem studies must evaluate the influence of PMI as it is dependent on the specific molecular forms under investigation."}