Partial degeneration of autonomic nerves of the heart of methotrexate-treated guinea pigs

Kinetics of the inhibition of acetylcholinesterase in camel retina by cisplatin

The inhibitory effect of cisplatin (CDDP) on camel retina acetylcholinesterase (AChE) was characterized. The CDDP effect was independent of the time of incubation with AChE before the addition of substrate, indicative of reversible inhibition. Moreover, dilution data prove that CDDP is a reversible inhibitor of camel retina AChE. Cisplatin inhibited AChE activity of camel retina in a concentration- and time-dependent manner, the IC50 values being 5.32 and 0.196 mM at 5 min and 24 h incubation times, respectively. The IC50 has dual components, i.e. directly proportional and inversely proportional to 0-1.5 h and 1.5-24 h incubation periods, respectively. The Michaelis-Menten constant (Km) for the hydrolysis of acetylthiocholine iodide (ASCh) was found to be 0.0796 mM and Vmax was 0.668 micromol/min/mg protein. Kmapp and Vmaxapp both decreased as the CDDP concentration increased. Dixon as well as Lineweaver-Burk plots and their secondary replots indicated that the nature of the inhibition was of the pure uncompetitive type. The value of Ki was estimated as 0.811 mM by the primary and secondary replots of the Lineweaver-Burk and Dixon plots. Kiapp decreased while Vmaxiapp increased after increasing the ASCh concentration.

Light and electron microscopic observations on the cerebellum of guinea pigs following low-dose methotrexate

The neurotoxicity of single and divided low-dose methotrexate (MTX) and the rescue effect of leucovorin (folic acid) were investigated by light and electron microscopic examination of the cerebellum of Guinea pigs. One group of animals received a single weekly intraperitoneal MTX in a dose of 10 mg/kg, a second received a similar dose divided into three equal fractions, and the third group received MTX rescued with an equal dose of leucovorin. The results showed degeneration of Purkinje cells indicated by shrinkage and distortion of perikarya, dissolution of mitochondrial cristae, and nuclear and nucleolar changes in all groups which received MTX. There was also astrocytic proliferation and perivascular edema. Lesser changes were found in the group which was rescued with leucovorin. The degenerative changes in the cerebellum particularly those of the Purkinje cells explain the neurological signs reported in cancer patients treated with MTX.