Mitsuteru Hosoi

Physiological and morphological characteristics of periodontal mesencephalic trigeminal neurons in the cat — intra-axonal staining with HRP

Intra-axonal recording and horseradish peroxidase (HRP) injection techniques were employed to define the response properties of periodontal mechanoreceptive afferents originating from the trigeminal mesencephalic nucleus (Vmes) and their morphological characteristics. The periodontal Vmes neurons were classified into two types: slowly adapting (SA) and fast adapting (FA) types. The central terminals of 7 SA and 4 FA afferents were recovered for detailed analyses. The whole profile of SA and FA neurons were unipolar in shape and their cell bodies were located in the dorsomedial parts of the Vmes. The united (U) fiber traveled caudally from the soma to the dorsolateral aspect of the trigeminal motor nucleus (Vmo), where it split into the peripheral (P) and C fibers with a T- or Y-shaped appearance. The P fiber joined the trigeminal sensory or motor tract. The C fiber descended caudally within Probsts tract. All 3 stem fibers issued main collaterals. The main collaterals of all neurons examined formed terminal arbors in the supratrigeminal nucleus (Vsup) and all but two SA neurons projected to the intertrigeminal region (Vint), while the projections to other nuclei of the trigeminal motor nucleus (Vmo), juxtatrigeminal region (Vjux), main sensory nucleus (Vp) and oral nucleus (Vo.r) differed between SA and FA afferents and between neurons of the same type. The SA and FA neurons were classified into three and two subgroups, respectively. The major differences in central projections between the two types were that all the FA neurons projected to the Vp or Vo.r but none of SA type and this relation was reversed in the projection to the Vjux, and that more than half of SA neurons projected to Vmo but only one FA neuron to the Vmo. The Vmes neurons which sent their collaterals into the Vmo had the P fiber passing through the tract of the trigeminal motor nerve. The average size of somata and mean diameters of U fibers and main collaterals from C fiber were significantly larger in SA neurons than FA neurons. The average size of fiber varicosities became smaller in the following nuclei, Vmo, Vsup, Vp, Vint and Vo.r, but not significant between the two functional types. The functional role of the periodontal Vmes afferents to jaw reflexes was discussed particularly with respect to their central projection sites in the brainstem nuclei.

Laminar-related projection of primary trigeminal fibers in the caudal medulla demonstrated by transganglionic transport of horseradish peroxidase

The mode of termination of primary afferent fibers within the cat trigeminal nucleus caudalis was investigated by means of the transganglionic transport of horseradish peroxidase (HRP). Several types of laminar-related labeling were observed, depending upon the survival time after HRP application. At the earliest survival time (28-34 h) the highest density of labeling was found in laminae I and II. At 2 and 3 days survival laminae III and IV were heavily labeled, in addition to laminae I and II where the amount of labeling was greatly increased in lamina I, but not in lamina II. At 5 days survival time an abrupt drop of labeling occurred in laminae I and II, while this pattern was not predominant in laminae III and IV. In lamina V the pattern of labeling was less intense and not changeable through all survival times observed. These findings indicating a differentiation of the primary afferent terminals have good correspondence with a functional specialization of neuronal locations since the functional properties of neurons vary according to their locations.

Trigeminal nerve endings of lingual mucosa and musculature of the rat

Horseradish peroxidase conjugated with wheat germ agglutinin (HRP-WGA) was injected into the trigeminal ganglion of adult rats to label the peripheral sensory receptors of the tongue. The conjugate was transported anterogradely to all the ipsilateral fungiform papillae and filiform papillae. Some labeled fibers crossed over to the contralateral papillae. In the intrinsic tongue muscle undulating nerve fibers along or across muscle fibers were often observed, and formed simple spiral endings.

Effects of 17β-oestradiol and 5α-dihydrotestosterone on the expression of the muscle and heart types of lactate dehydrogenase isozymes in the masseter muscle of developing mice

17 beta-oestradiol (E2) and/or 5 alpha-dihydrotestosterone (5 alpha-DHT) had no effect on the expression of isozymes of lactate dehydrogenase (LDH) in the masseter muscle of intact male mice. However, treatment with E2 restored the level of the muscle (M) type of LDH isozyme, which had been reduced by testectomy, to that found in intact male mice treated with vehicle only. Moreover, 5 alpha-DHT alone was more effective than E2 in increasing the relative level of this isozyme in testectomized mice. 5 alpha-DHT had a more significant effect on the increase in the relative level of the M-type LDH isozyme when combined with E2. These results suggest that androgens promote, in the presence of oestrogens, the postnatal changes in the characteristics of the masseter muscle of developing male animals.

Improved preservation of Amoeba proteus ultrastructure revealed by quick-freezing followed by freeze-substitution

Summary For better preservation of Amoeba proteus ultrastructure, we have applied the quick-freezing and freeze-substitution method to them which are difficult to fix optimally for conventional electron microscopy. This method provided a greatly improved visualization of A. proteus when compared with the conventional fixation: (1) Most of the membrane components including the cell membrane and intracellular membranes were smoother and showed distinct trilaminar substructures. Only the vacuolar membrane containing a crystal had wrinkles; (2) substructure of the surface coat of the cell membrane was clearly distinguishable; (3) cytoskeletal components were well preserved in the cortical and central cytoplasm; (4) each Golgi component and cistern of the endoplasmic reticulum (ER) were more clearly resolved, and their contents were also well preserved; (5) variously sized Golgi vesicles associated with the trans face of the Golgi network (TGN) were clearly preserved. Only clathrin-coated vesicles were derived from the TGN; (6) perivacuolar vesicles with contractile vacuoles and satellite vesicles around the food vacuoles were clarified, and all of their contents were well preserved; (7) mitochondrial, cytoplasmic, and nuclear matrices were denser and filled with an abundance of fibrillar and granular materials. Consequently, after comparing the above findings with information obtained by the method using conventional chemical fixation, we suggest that all theses observations obtained by the quick-frozen / freeze-substitution method indicate a more faithful representation of A proteus ultrastructure.