PMC:2493521 / 41740-45527 JSONTXT

{"project":"2_test","denotations":[{"id":"18347928-9064599-20694326","span":{"begin":168,"end":172},"obj":"9064599"},{"id":"18347928-12694381-20694327","span":{"begin":186,"end":190},"obj":"12694381"},{"id":"18347928-9402561-20694328","span":{"begin":208,"end":212},"obj":"9402561"},{"id":"18347928-14734628-20694329","span":{"begin":224,"end":228},"obj":"14734628"},{"id":"18347928-7798918-20694330","span":{"begin":254,"end":258},"obj":"7798918"},{"id":"18347928-6212778-20694331","span":{"begin":273,"end":277},"obj":"6212778"},{"id":"18347928-455043-20694332","span":{"begin":286,"end":290},"obj":"455043"},{"id":"18347928-1480765-20694333","span":{"begin":534,"end":538},"obj":"1480765"},{"id":"18347928-3989524-20694334","span":{"begin":848,"end":852},"obj":"3989524"},{"id":"18347928-6212778-20694335","span":{"begin":867,"end":871},"obj":"6212778"},{"id":"18347928-7723629-20694336","span":{"begin":1043,"end":1047},"obj":"7723629"},{"id":"18347928-14734628-20694337","span":{"begin":1059,"end":1063},"obj":"14734628"},{"id":"18347928-455043-20694338","span":{"begin":1072,"end":1076},"obj":"455043"},{"id":"18347928-17045977-20694339","span":{"begin":1090,"end":1094},"obj":"17045977"},{"id":"18347928-2213015-20694340","span":{"begin":1109,"end":1113},"obj":"2213015"},{"id":"18347928-14734628-20694341","span":{"begin":1313,"end":1317},"obj":"14734628"},{"id":"18347928-17045977-20694342","span":{"begin":1331,"end":1335},"obj":"17045977"},{"id":"18347928-15921819-20694343","span":{"begin":2401,"end":2405},"obj":"15921819"},{"id":"18347928-8515212-20694344","span":{"begin":2463,"end":2467},"obj":"8515212"},{"id":"18347928-7723629-20694345","span":{"begin":2486,"end":2490},"obj":"7723629"},{"id":"18347928-17045977-20694346","span":{"begin":2504,"end":2508},"obj":"17045977"}],"text":"Assessment of agonal state\nAgonal status impacts tissue quality, as fever, ischemia-hypoxia and acidosis are deleterious to many molecules of interest (Harrison et al. 1995; Hynd et al. 2003; Johnston et al. 1997; Li et al. 2004; Morrison-Bogorad et al. 1995; Perry et al. 1982; Spokes 1979). However, agonal status is difficult to determine in elderly subjects, who usually die in a nursing home without close medical supervision. The pH of CSF and/or brain tissue has been used as a surrogate marker for agonal status (Ravid et al. 1992). Some studies have reported that when the agonal state, as inferred from clinical data, is expected to have been detrimental, for example in cases of prolonged mechanical ventilation, the pH is low (e.g. pH 5.5–6.0), while in cases of sudden death it is higher, closer to normal (e.g. 7.0–7.4) (Hardy et al. 1985; Perry et al. 1982). Some enzyme activities and measures of RNA integrity have correlated with postmortem pH, but not in all studies or for all subtypes of these molecules (Kingsbury et al. 1995; Li et al. 2004; Spokes 1979; Stan et al. 2006; Yates et al. 1990). Two recent comprehensive studies may have resolved the variability in prior reports, as it was found that only pH values under about 6.5–6.8 were associated with decreased RNA integrity (Li et al. 2004; Stan et al. 2006).\nWe conducted our own study of postmortem CSF pH as a marker of tissue viability by correlation with viable cell yield in postmortem glial cultures, reasoning that physiologically damaging agonal conditions would result in a decreased yield of viable cells taken from that tissue.\nThe viable cell yield from 46 consecutive cell culture cases was compared with their respective CSF pH and PMI. Brain tissue for culture was obtained from the cerebral white matter of the centrum ovale. Viable cell yield ranged from 0.74 to 6.47 × 106 cells/g brain tissue. The CSF pH ranged from 6.36 to 7.19 (mean 6.73). Post-mortem interval ranged from 1.5 to 4.5 h. Multiple linear regression analysis indicated that CSF pH was not a significant independent predictor of viable cell yield (R = 0.12, P = 0.45). Postmortem interval, however, was significantly related (inversely) to viable cell yield, (R = 0.28, P = 0.06). A surprising result was that PMI was significantly correlated (inversely) with CSF pH (R = 0.37, P = 0.01), in agreement with one other group (Catts et al. 2005) but in disagreement with several other reports (Karkela 1993; Kingsbury et al. 1995; Stan et al. 2006). The difference between our results and those of other groups may be due to our uniformly short PMI, as other studies have included many cases with much longer PMIs. It is likely that brain cells surviving after death are generating lactic acid via anaerobic metabolism. As the PMI increases, fewer and fewer cells are alive and eventually all cells will be dead. At some point in this process, it is probable that pH would eventually stabilize. Therefore studies that have primarily involved cases with longer PMI’s may not find any relationship between PMI and pH. We have not performed both RNA integrity assessments and CSF pH measurement on enough cases to allow a meaningful correlation of these factors as yet.\nOur results suggest, therefore, that CSF progressively acidifies with increasing postmortem interval but that it is not a useful predictor of tissue viability, at least for cases with PMIs in the 1–5 h range. We have decided that direct assessment of tissue preservation is preferable to indirect markers such as CSF pH or agonal medical history collection. As RNA is one of the most important molecular species for research uses, we have been using RNA quality, assessed qualitatively in RNA gels as described above, as a general indicator of tissue quality."}