Initial Inhibitory Effects Research Articles

Prevention of the inhibitory effects of aspirin on sodium transport in canine gastric mucosa by prostaglandin: Correlation with mucosal morphology

Using an in vitro canine gastric mucosal preparation, this study evaluated the effects of 1 m M aspirin in a buffered Ringer solution (pH = 7.4), with and without concomitant prostaglandin (PG) treatment, on net sodium transport (mucosa to serosa) across gastric epithelium. Administration of aspirin to the mucosal bathing solution for 2 hr significantly decreased the potential difference (PD), short circuit current (I sc), and net sodium transport (net J-Na +) when compared with untreated control mucosa. In mucosa treated with 16,16-dimethyl PGE 2 (8 × 10 −6 M) in the serosal bathing solution 40 min after aspirin exposure and for 80 min thereafter, the initial inhibitory effects on PD, I sc, and net J-Na + induced by aspirin were completely reversed within 40 min of PG treatment, having returned to control values. Histologically, mucosa exposed to aspirin alone showed evidence of diffuse cellular injury involving 50–60% of the surface epithelium. In contrast, mucosa treated with prostaglandin in conjunction with aspirin exposure demonstrated damage involving only 20–30% of the epithelium. These findings suggest that stimulation of sodium transport by PG may play a role in mediating the cytoprotective effects of PGs against aspirin-induced gastric mucosal injury.

INITIATION AND DEVELOPMENT OF ROOT NODULES OF CASUARINA (CASUARINACEAE)

Roots of seedlings of the “beefwood” tree, Casuarina cunninghamiana Miq. grown in nitrogen‐free nutrient solution were inoculated with a suspension prepared from crashed root nodules taken from mature plants. Marked deformation of root hairs was evident but no infection threads were observed in root hairs. The mode of infection remains undetermined. Root nodules were initiated within three weeks and thereafter numerous upward‐growing nodule roots developed from each nodule. Nodules in this symbiotic nitrogen‐fixing plant resulted from an infection caused by an unidentified actinomycete‐like soil microorganism. Anatomical analysis of nodule formation showed that nodules are the result of repeated endogenous lateral root initiations, one placed upon another in a complexly branched and truncated root system. The endophyte‐infected cortical tissues derived from successive root primordia form the swollen nodular mass. Nodule roots develop from nodule lobes after escaping from the initial inhibitory effects of the endophyte. Included is a discussion of the anatomical similarities between nodules of Casuarina which produce nodule roots and those of Alnus which form coralloid nodules usually lacking nodule roots.