A simple in vitro method to detect singlet oxygen and to compare photodynamic activity using alkaline phosphatase.

A simple, sensitive and reliable in vitro method based on photodynamic inactivation of alkaline phosphatase to detect singlet oxygen and for evaluating relative photosensitizing efficiencies of photosensitizers such as hematoporphyrin (Hp) and phthalocyanines has been developed and compared with photobleaching of p-nitroso dimethyl aniline (RNO) and photooxidation of L-tryptophan. Inactivation of alkaline phosphatase is dependent both on light fluence and sensitizer concentration. Scavengers like mannitol and azide anion indicated the involvement of singlet oxygen in the deactivation of alkaline phosphatase, since azide anion provided concentration dependent protection whereas mannitol had no effect and that compared to ordinary water, photoinactivation of alkaline phosphatase was three times higher in 65% D2O. Alkaline phosphatase appears to be resistant to free radical attack (particularly to OH radicals) since hydrogen peroxide alone or in presence of ferrous ions did not reduce the enzyme activity and mannitol or azide anion gave no significant protection when alkaline phosphatase was irradiated with Co-60 gamma rays up to 2 K Gy. With the present method using red light, the chloroaluminium phthalocyanine sulphonates prepared by sulphonation showed higher and the corresponding condensation product lower photodynamic activity; Hp being intermediate and Mn- and Gd-phthalocyanines had no photodynamic activity.

Serum and rectal mucosal zinc levels in acute and chronic diarrhea.

Serum and rectal mucosal zinc content was estimated in children (6-18 months old) with acute diarrhea (Group I: n = 50), chronic diarrhea (Group II: n = 25), extraintestinal infections (Group III: n = 15) and apparently healthy controls (Group IV: n = 20). The sex and nutritional status of various groups was comparable. The mean serum and tissue zinc levels in acute (p less than 0.001) and chronic (p less than 0.05 for serum; p less than 0.001 for tissue) diarrhea groups were significantly lower than healthy and infected controls. Group II had significantly lower (p less than 0.001) serum and rectal zinc content in comparison to Group I. There was a significant negative correlation between serum zinc and diarrheal duration (r = 0.5676; p less than 0.001). Repeat estimation at discharge in 38 patients (25 in Group I, 13 in Group II) revealed a significant reduction in both tissue and serum zinc and only tissue zinc in acute and chronic diarrhea, respectively. A total of 23 patients (16 in Group I, and 7 in Group II) were evaluated 2 weeks after discharge. After discharge, at recovery there was no alteration in serum zinc, but tissue zinc was marginally higher (p greater than 0.05). It is concluded that zinc depletion occurs in diarrhea, more so in the chronic state; with the continuation of diarrhea, depletion progresses; and there is a tendency for repletion during convalescence.