Up-regulation of prostaglandin E2 binding and of prostanoid release in rabbits producing antibodies against prostaglandin E2

German Giant rabbits successfully immunized against prostaglandin (PG) E2 as shown by a rise in antibody titers developed gastric mucosal lesions. Enzymatically dispersed gastric mucosal cells of these animals had a significantly enhanced production of PG E2 and PG I2 as measured by specific radioimmunoassays. This may be explained by an increased supply with endogenous arachidonic acid (as indicated by an enhanced phospholipase A2/LAT ratio) and by a higher activity of the subsequent PG forming enzymes (as indicated by a more effective stimulation of PG production by exogenous arachidonic acid). Gastric mucosal plasma membranes of immunized rabbits had significantly higher PG E2 binding capacity (108 +/- 9 fmol/mg protein) than those of nonimmunized rabbits (72 +/- 5 fmol/mg protein). The ligand affinity was not affected by immunization. Neither histamine-stimulated 14C-amino-pyrine uptake of isolated parietal cells as a marker for acid production nor its inhibition by PG E2 were influenced by receptor up-regulation. The increased eicosanoid release can be regarded as an endogenous defense mechanism against increased mucosal vulnerability caused by PG E2 scavenging. The potential role of PG E2 receptor up-regulation in support of this process remains to be established.     

Orthogonal arrays are absent from the membranes of human glioblastomatous tissues

Human astrocytic gliomas were studied with the freeze fracture technique. Orthogonal arrays of particles were noted in the plasma membranes of low-grade astrocytoma tissues. However, no such arrays were found in the plasma membranes of anaplastic glioma or glioblastoma tissues. Gap junctions were rarely seen in the membranes of these higher-grade gliomas; when seen, they consisted of relatively few particles in poorly organized plaques. These plasma membranes were dominated by randomly distributed single particles. These findings constitute aspects of the loss of differentiation in these malignant tumors.     

Diel plasma melatonin profile in a cyclostome, the river lamprey

Plasma melatonin levels in adult river lampreys Lampetra fluviatilis , sampled during their upstream migration showed a pronounced diel profile, with high levels during the night and lower levels during the day, showing that a cyclostome, in common with other vertebrates, exhibits such a diel plasma profile.     

Perfusion rate dependent prostaglandin release from isolated rabbit kidneys

Isolated rabbit kidneys were perfused with 37 degrees C Krebs-Henseleit solution aerated with 95% O2 + 5% CO2. Perfusion rate was varied from 1 to 10 ml/min. This was accompanied by parallel changes of perfusion pressure, prostaglandin excretion and release of radioactivity from kidneys with 14C-arachidonic acid incorporated into the tissue lipid pool. It is suggested that enhancement of perfusion rate raises the intrarenal pressure which increases renal prostaglandin release due to increased substrate availability.