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Notes: Summary Intra-axonal recordings were made from trigeminal primary afferent fibers in the trigeminal spinal nuclei oralis and caudalis of cats. Primary afferent depolarization (PAD) was evoked in these afferents by stimulation of the trigeminal peripheral sensory branches (the frontal, infraorbital and lingual nerves), the cerebral cortex and the trigeminal spinal nucleus caudalis. The properties of the PAD, including the threshold, latency, receptive field (sensory branches effective for PAD induction) and frequency-following capacity, were studied with the following results: 1. Stimulation of all the peripheral branches tested as well as the cerebral cortex could evoke PAD in the same single fiber. The latency of the PAD evoked by stimulation of the nerve in which the fiber being recorded from was included was generally shorter than that evoked by other branches. The PAD evoked by peripheral nerve stimulation was assumed to be disynaptic in some cases. 2. The peripherally evoked PAD was chiefly attributable to low threshold afferents in the stimulated sensory branches of the trigeminal nerve. 3. The peripherally evoked PAD could follow stimulation at up to 30/sec, though the amplitude was reduced. 4. Stimulation of the nucleus caudalis could evoke PAD with disynaptic latency in the majority of the fibers terminating in the same nucleus, whereas it evoked PAD with mainly polysynaptic latency in the fibers terminating in the nucleus oralis. The results are discussed in relation to the neuronal circuitry responsible for induction of the trigeminal PAD.

Notes: Summary Depth analysis was performed on the field potential evoked by stimulation of the infraorbital nerve in the trigeminal spinal nucleus caudalis and the subjacent lateral reticular formation of cats. It was shown by dye marking of the recording positions that each subnucleus of the nucleus caudalis (subnucleus marginalis, gelatinosus and magnocellularis) and the reticular formation could be differentiated from one another by the characteristics of the peripherally evoked field potentials. Responses of neurons were extracellularly recorded in the subnuclei gelatinosus and magnocellularis of the nucleus caudalis and in the reticular formation to stimulation of the trigeminal sensory branches (the frontal, infraorbital and lingual nerves), the nucleus ventralis posteromedialis of the thalamus and the cerebral cortex. The properties of the neurons were studied in relation to their thresholds, latencies, receptive fields (sensory branches effective for spike generation) and frequency-following capacities. These responses were then compared with properties of the PAD induced in the fibers terminating in the nucleus caudalis by similar peripheral and central stimulation. It was found that the neurons in the subnucleus magnocellularis were the most likely candidates for the interneurons mediating the peripherally evoked disynaptic PAD in the trigeminal nerve fibers terminating in the nucleus caudalis.

Notes: The effect of polymer dilution on the acid-catalyzed gelation of partially N-methylolcarbamoylethylated polyvinyl alcohol has been studied viscometrically and chemically. The result that the higher the degree of dilution the greater the extent of reaction at gelation, especially in the polymer concentration below 15% by weight, indicates that a certain increase of intramolecular crosslinking with dilution occurs. However, sufficient agreement with Kilb's theory could not be found. Also, even when the extent of reaction at gelation was extrapolated to infinite concentration of polymer, it was far greater than that obtained from Flory's theory. The discrepancy may presumably be attributed to the fact that in addition to the intramolecular crosslinking, all the methylol groups on the polymer chains which are coiled, entangled, and strongly solvated prior to crosslinking are not equally reactive sterically.

Notes: Gelation velocity and reaction rate for the acid-catalyzed condensation reaction in the aqueous solution (10-22%) of partially N-methylolcarbamoylethylated polyvinyl alcohol (about 20 mole-% degree of methylolcarbamoylethylation) have been investigated by the falling ball viscosity method and the chemical analysis of methylol groups including the effects of kinds of acid, concentrations of acid and polymer, and temperatures of reaction. For the reciprocal gel point, 1/tg, and the hydrogen ion concentration, [H+], the following equation holds: \documentclass{article}\pagestyle{empty}\begin{document}$ 1/t_g = c[{\rm H}^ +]^\alpha $\end{document} where α and c are constants independent of the kind of acid; also α is independent of temperature and polymer concentration, while c increases with increasing temperature or polymer concentration. The 1/tg is approximately proportional to the concentration of polymer in the range of a concentrated polymer solution above about 15% by weight. From this fact, it is suggested that, in a concentrated polymer solution, the intermolecular crosslinking proceeds predominantly as a bimolecular reaction with respect to methylol groups. Assuming that the increase of the apparent viscosity of the reacting system is mainly due to that of the structural viscosity which should be increased by a bimolecular crosslinking reaction, the following expression was derived for the gelation velocity: \documentclass{article}\pagestyle{empty}\begin{document}$ \eta _0 /(\eta _t - \eta _0) = A(1/i - 1/t_g) $\end{document} in which, \documentclass{article}\pagestyle{empty}\begin{document}$ \begin{array}{*{20}c} {A/t_g = 1 - x_g /a} & {{\rm and}} & {k = x_g /(a^2 A)} \\ \end{array} $\end{document} where η0 and ηt are the apparent viscosities at time 0 and t, respectively, A is a measure of gelation velocity, a is the initial number of methylol groups, xg is the number of crosslinked methylol groups at the gel point, and k is the bimolecular rate constant. The experimental results of viscosity changes have shown a fairly good agreement with the above expression except in the early stage of condensation. The extent of reaction at the gel point (xg) has been estimated to be about 0.03-0.05 regardless of concentration of polymer and acid, kinds of acid, and temperature. Also, it has been observed that the rate constant of reaction is independent of the concentration of polymer and is proportional to the concentration of hydrogen ions. The above expression and estimation have been verified by the chemical analysis of methylol groups in the condensation processes. However, the extent of reaction at the gel point is about ten times that predicted by Flory's theory. This discrepancy may presumably be attributed to the fact that all of the methylol groups on the polymer chains which are coiled, entangled, and strongly solvated prior to the crosslinking are not equally reactive sterically and a certain extent of intramolecular crosslinking occurs. The activation energy of reaction has been estimated to be about 21 kcal./mole.