The nature of the ESR signal in lyophilized tissue and its relevance to malignancy

Abstract

Comparison of 9 and 35 GHz spectra, obtained from frozen and lyophilized tissues, with those from model systems containing ascorbic acid, confirm that the major component of the "lyophilization signal" of tissue is the ascorbyl radical, stabilized by adsorption on an inert matrix. The magnitude of the signal under anoxic conditions is shown to be a measure of cellular damage, which allows intracellular ascorbic acid to be oxidized. On exposure of lyophilized samples to air, the signal increases due to autoxidation of the available tissue ascorbic acid. Under moist atmospheric conditions the ascorbyl radicals readily decay, leaving other radicals, which appear to be formed by interaction of ascorbic acid or ascorbyl radicals with some tissue component. The results show that, although widely studied, the free radical ESR signal of lyophilized tissue is not unique to tumour and has no relevance to malignancy.

Anticancer effects of 6-o-palmitoyl-ascorbate combined with a capacitive-resistive electric transfer hyperthermic apparatus as compared with ascorbate in relation to ascorbyl radical generation

“…And by ESR spectroscopy upon treatment with hyperthermia, sodium ascorbate produced a higher AscR value and more potent cytotoxicity against human leukemic and glioblastoma cell lines than Asc (Satoh et al 1996). The ESR signal intensity of the AscR is taken as an indicator of oxidative stress due to oxidation of intracellular ascorbic acid leading to cellular damage (Dodd and Swartz 1984). AscR signal, although not detected in normal muscle, is readily observed in implanted tumors in vivo (Silcock and Dodd 1976).…”

The significance of electron spin resonance of the ascorbic acid radical in freeze dried human brain tumours and oedematous or normal periphery

“…The three data columns, T, E, N, (Table I) (Dodd & Swartz, 1984). Rather, it had become obvious that a strong signal resulted from high blood content.…”

“…Obviously, the time it takes to prepare fresh samples for ESR spectroscopy precludes the observation of in vivo reactions. In addition, fresh tissue slices seem to be very susceptible to non-physiological oxidation and, in spite of this, to low sensitivity (Dodd & Swartz, 1984). Frozen slices cannot be excepted from this either.…”

“…Attempts to exclude air during and after freeze drying in order to prevent artifactual radical formation (Blumenfeld, 1981) are not convincing. The air exposed lyophilisates have, however, allowed intriguing correlations between ESR signal strength and pathological states (Dodd & Swartz, 1984;Lohmann, 1984) (Brau et al, 1984). As a correlation does not constitute proof, verification of our findings was sought through model experiments using normal and oedematized rat brain, human blood and its components, and aqueous suspensions of silica gel or Sephadex.…”

“…Problems with indirect techniques, commonly employed in such studies, have been pointed out (Halliwell, 1984). Information about the potentially most direct approach, electron spin resonance (ESR) of radicals in tissue stems primarily from non-nervous material, usually related to neoplasia (Dodd & Swartz, 1984;Lohmann, 1984). In practice, however, difficulties are encountered in linking ESR of fresh, frozen, or freeze dried tissue to in vivo radical content (Dodd & Swartz, 1984;Heckly, 1976).…”