Physiological and Pharmacological Studies on Cervical Motor Neurons in Slices Prepared from Neonatal and Aged Mice

The effects of age on the physiological properties of cervical motor neurons were examined in slices made from an excised spinal cord graft of ICR mice from the second day after birth to age 350 days. The membrane potential of post-natal day 2 (PD2) to PD350 was about -65 mV and did not change greatly with age, although it was slightly higher at PD2. However, there were significant changes in membrane resistance, which increased with age from about 15 to 30 MΩ. The depolarization induced by the excitatory amino acid agonists, kainic acid, NMDA and AMPA, decreased with aging in spite of the increase in membrane resistance. The motor neurons of the aged mice showed delayed recovery from excitation caused by excitatory amino acid agonists. By injecting Lucifer yellow CH into motor neurons, it was observed that the dendrite trees become thin, and some of the dendrite branches were missing in older animals.

Ganglionic and non-ganglionic neurons in frog heart: do they differ?

This study was designed to compare the morphology of neurons in relation to their distance from the major nerve trunks in the heart of the frog Rana temporaria. Seventy-nine intracardiac neurons were labelled intracellularly with fluorescent markers Lucifer Yellow CH and Alexa Fluor 568. The neurons located on the extensions of the vagus nerve were considered as ganglionic, while neurons spread loosely at further distance from these extensions were considered as non-ganglionic. The mean area of the soma in ganglionic neurons was about 25% larger than in non-ganglionic neurons. Ganglionic neurons had a higher soma area/nucleus area ratio than non-ganglionic neurons. Although both the total number and the total length of dendrite-like processes was similar between the two groups, ganglionic neurons had significantly fewer dendrite-like processes from the soma (1.5±0.3 vs. 3.9±1.0; P<0.05) and shorter total length of these processes from the soma (63±18 μm vs. 178±51 μm; P<0.05). In conclusion, ganglionic and non-ganglionic frog intracardiac neurons exhibit substantial morphological differences. We hypothesize that these differences may indicate different projections or variations in the number of their preganglionic inputs.

Anatomy of the Legume Nodule Cortex: Species Survey of Suberisation and Intercellular Glycoprotein

Nodules of 29 species from 23 legume genera were examined for suberisation and glycoprotein deposits. Extensive suberisation of the nodule outer cortex to form a peridem was considered a primitive feature, common to non-legume and caesalpinioid nodules. The periderm was less extensive in nodules of Mimosoideae and Papilionoideae. Vascular bundles within the nodule were always surrounded by a vascular endodermis, defined by the presence of suberin on radial walls. Suberisation of the tangential walls of this endodermis was considered to be a primitive feature (present in all species examined of Caesalpinioideae and Mimosoideae, and in 10 out of 21 Papilionoideae) which may limit solute import to and export from the nodule. Glycoprotein was observed in the apoplast of the cortex in the three papilionoid species examined, but was absent in the caesalpinioid species examined. The common endodermis was recognised as an advanced feature, present only in certain species of the subfamily Papilionoideae (5 of 7, and 11 of 15 species of indeterminate and determinate nodule growth respectively). A membrane impermeant dye (lucifer yellow-CH), supplied in the rhizosphere under a mild vacuum, was observed to infiltrate through the cortex and into the infected zone in caesalpinioid nodules, and as far as the inner cortex in mimosoid and papilionoid nodules. Thus the common endodermis does not serve as an apoplastic barrier, and is unlikely to serve as a significant oxygen 'diffusion barrier'.