Shikaigaku

Show abstractHide abstract

In order to understand their functional significance, the response characteristics were studied of dental pulp neurons within the subnucleus reticularis ventralis (SRV) of the caudal medulla oblongata in the cat. Furthermore, we attempted to identify neurons relaying to the SRV and projecting the area of dental pulp neurons of the SRV.
Experiments were carried out on cats anesthetized with urethane and chloralose. Single unit activities were recorded from the SRV using glass capillary microelectrodes filled with 2% pontamine sky blue in 0.5M sodium acetate.
The neurons usually responded to bilateral dental pulp afferents, and were located within the dorsolateral part of the SRV. They were usually excited by mechanical stimulation of the ipsi- or bilateral cornea. In addition, they responded to noxious mechanical stimulation of the ipsi- or bilateral pinna, face and/or tongue. Some of the neurons were also activated by tapping the nose. Units having receptive fields similar to these neurons were found in lamina VII of the first cervical cord and in the intralaminar nuclei. About half of the neurons tested were antidromically activated by electrical stimulation of the nucleus centralis lateralis. It was also found that a significant proportion of the neurons was antidromically activated by electrical stimulation of the mesencephalic reticular formation.
The spinal trigeminal tract was cut at the level of the obex in order to interrupt trigeminal primary afferent input to the trigeminal subnucleus caudalis and its nearby bulbar lateral reticular formation. After a tractotomy, dental pulp neurons were found in the SRV. Neurons antidromically excited by electrical stimulation of the SRV were found within the nucleus reticularis parvocellularis.
These results suggest that dental pulp neurons relay trigeminal nociceptive inputs directly or indirectly via the mesencephalic reticular formation to the intralaminar nuclei and that neurons relaying trigeminal nociceptive input onto the SRV are located within the rostral to the obex.

View full abstract

Download PDF (1337K)

The masseter muscle of anesthetized adult and infant monkeys were electrically stimulated, and occlusion on various sizes of materials simulated by placement of 3, 5, and 7 mm thickness sticks in the molar region on one side.
As the size of the occluding material increased, the occlusal forces were increased, accompanied by increases in the strain arising in the skull. In contrast, when the material was too large, i. e., when the degree of opening was excessive, there was a decrease in strain.
When the size of the occluding material was large, the number of bones where stresses concentrated were greater in adults than in infants. This phenomenon resulted from the fact that the skull in infancy tends to buffer occlusal forces as one unit since the bones are immature, in contrast to the adult skull where each bone can buffer the occlusal forces independently since it is fully developed.
In addition, it was found that the occlusal force buffering effect of the temporal and parietal bones were markedly different in infants and adults.

View full abstract

We studied electrochemically the adsorption of protein to synthetic hydroxyapatite (HAp) treated with sodium fluoride (NaF) and acidulated fluoride phosphate (APF). The fluoride concentrations of NaF and APF were adjusted to 0.01%, 0.1%, and 0.9%. The protein solutions used were human serum albumin (HSA, pI=4.7), chicken egg conalbumin (CA, pI=6.8) and salmon protamine (PR, pI=11.0) in 1/30 M phosphate buffer at pH7.0. The protein concentrations were set at the five levels of 20%, 40%, 60%, 80% and 100% the concentration necessary to achieve saturated adsorption of the protein to the HAp. The fluoride was applied by immersing 50 mg of HAp in 25 ml of each of the fluoride solutions for four minutes. The adsorption of protein to the fluoride-treated HAp was determined by placing the HAp in protein solutions for one hour at room temperature.
The zeta potential of the fluoride-treated HAp in the protein solutions was measured by micro-electrophoresis (Pen-Kem Co., Lazer Zee Model 501), and the value obtained was analyzed by the formula of Miyake, et al. The zeta potentials of NaF-treated HAp were the same as these of untreated HAp in the several proteins. The adsorption coverage and free energy of adsorption of HAp treated with APF was lower than that of the other HAp. The adsorption of protein to HAp was affected to prevent by APF treatment. These results suggest that the adsorption of protein to fluoride-treated HAp was a monolayer model of Langmuir, and was dependent on the interaction between the protein and the surface charge structure on the HAp which had been treated with application of NaF and APF.

View full abstract

We studied electrochemically the effect of stannous fluoride (SnF₂) on the adsorption of protein to synthetic hydroxyapatite (HAp). Fifty milligram samples of HAp were immersed in 25ml of SnF₂ solution adjusted to fluoride concentrations to 100, 1,000 and 9,000ppm. The surface characterization of SnF₂-treated HAp was investigated by measuring the zeta potential in 1mM KNO₃ and 1/30 M phosphate buffer at pH7.0, and by measuring the contact angle using the sessile drop method. The zeta potential of SnF₂-treated HAp decreased significantly compared with that of untreated HAp, although there were no statistically significant differences for different concentrations of fluoride. Dental enamel treated with SnF₂ was found to be more hydrophobic than untreated HAp.
The adsorption of human serum albumin (HSA, pI=4.7), chicken egg conalbumin (CA, pI=6.8) and salmon protamine (PR, pI=11.0) to the SnF₂-treated HAp was determined by placing the HAp in each of the protein solutions for one hour at room temperature. The zeta potentials of the protein solutions were measured by micro-electrophoresis (Pen-Kem, Co., Lazer Zee, Model 501) and the values obtained were analyzed by the formula of Miyake, et al. The zeta potentials decreased dramatically even for the lowest protein concentrations. The correlation between 1/Δζ and 1/C showed good linearity. Thus, the adsorption of protein to SnF₂-treated HAp conformed to the monolayer model of Langmuir. The component of protein in the zeta potential was close to that of untreated HAp for HSA and PR. However, for CA the component of protein in the zeta potential for treated HAp was smaller than for untreated HAp. It is suggested that the adsorption of protein to SnF₂-treated HAp depends on the conformation of protein adsorbed and the interaction of surface net charge and hydrophobicity between the sorbent and protein.

View full abstract

Register with J-STAGE for free!