A histochemical and electron-microscopic study of the trigeminal ganglion of the rat

Archs oral BioL

Vol.

14, pp. 1135-1146,

1969.

Pergamon

Press. Printed

in Ct.

Britain.

A HISTOCHEMICAL AND ELECTRON-MICROSCOPIC STUDY OF THE TRIGEMINAL GANGLION OF THE RAT HIDEO MATSUURA,MASAHIKOMORI and KENSAKUKAWAKATSU Department of Oral Surgery, Osaka University Dental School, 32-Joan-cho, Kita-ku, Osaka, Japan Summary-The electron-microscopic and the enzyme histochemical

studies were carried out and the following findings obtained: (1) Light-microscopically, three types of the nerve cells were distinguished, i.e., large cells, small cells and intermediate cells. Electron-microscopically, three types of cells were also discernible, i.e., clear cells, dark cells and transitional cells. The diameter of large cells was about 60 p and that of dark cells, 30 CL. The mitochondrial dehydrogenases were more evident in the nerve cell bodies than in capsular cells. Mitochondria were more numerous in nerve cell bodies than in capsular cells.

In dark cells, the mitochondrial dehydrogenaseswere concentrated in the perinuclear area and AChE was mainly localizedin the peripheral portion of the perikaryon. In large cells, these enzymes were distributed throughout the perikaryon. The intracellular localization of the enzymes were coincident with the intracellular distributions of the mitochondria and the rough surfaced endoplasmic reticulum in the perikaryon of the aforementioned nerve cell types. Therefore, it was suggested that the large cell was identical with the clear cell, the small cell with the dark cell and the intermediate cell with the transitional cell. (2) The capsular and/or the Schwann cell intervened between the neuron and capillary vessels. (3) The capsular cell showed the characteristically prominent stainability to NADPdependent IDH, G6PDH and to ALP. Electron-microscopically, the two types of the capsular cells were discernible, i.e., dark capsular cells and clear capsular cells. At the junction of clear cells and capsular cells there were “labyrinthine structures” and “trophospongium” and these structures may play a role in the transportation of nutrition between the two cells. On the other hand, no such structure was observed in dark cells. (4) It is reasonable to assume that there is transformation of the nerve cell types in various biological states from dark cell to clear cell.

INTRODUCTION THE TRIGEMINAL ganglion corresponds

to a spinal ganglion; that is, it belongs to the somato-sensory nervous system. The histological architecture of the ganglion has been investigated in various vertebrates by a number of authors (CAJAL, 1906; NEMOTO 1957; FERNANDEZ,1967) and there is general agreement that it consists of several types of neuron surrounded by capsular cells. Histochemical studies on the ganglion made by HERMANN(1961) in the cow, by TEWARI(1963) in the rat and by some other authors have revealed the localization of several dehydrogenases and hydrolytic enzymes in the ganglia. Recently, with the development of the electron-microscopic techniques, the submicroscopic structure of the ganglia have been explored (DIXON, 1963; MOSES,1967). 1135 A.O.B. 14/1&-A

1136

HIDEOMATSWRA, MA~AHIKO MORIAND

KENSAKU

KAWAKATW

However, among the above-mentioned reports there are not a few differences of opinion in respect of detail, and problems remain to be solved. In the present study, the electron-microscopic and the enzyme-histochemical studies were carried out on the trigeminal ganglion of the rat, in order to attempt to clarify some of these problems. MATERIALS

AND METHODS

Healthy male 2-30 week-old rats were killed by decapitation and the trigemina ganglia were immediately removed. Specimens for histochemical study were stored in - 70” C dry ice without fixation and those for the electron-microscopic examination were fixed in 5-6 per cent glutaraldehyde solution of 0.2 M cacodylate buffer (4” C, pH 7 *4) for less than 1 hr. The enzyme-histochemical methods The ganglia stored in dry ice were cut in the - 20” C cryostat at the thickness of 12 CL.The sections for the demonstration of the hydrolytic enzymes were briefly fixed in 10 per cent cold formalin and rinsed in distilled water before incubation. Those for oxidative enzymes were not fixed before incubation. The dehydrogenases tested for, by the methods of NACHLASet al. (1957), were succinate (SDH), lactate (LDH), malate (MDH), glutamate (GDH), glucose-6phosphate (G6PDH) and NADP-dependent isocitrate (IDH) dehydrogenases. Monoamine oxidase (MAO) was detected by the tryptamine-tetrazolium method of GLENNERet al. (1957). The hydrolytic enzymes demonstrated were alkaline phosphates (ALP), acid phosphatases (ACP), acetylcholinesterase (AChE) and nonspecific cholinesterases (ChE). In the demonstration of ALP, the cold formalinfixed sections were incubated for 40 min at 20” C in the medium consisting of 5 mg naphthol AS-MX phosphate, 15 ml of 0.2 M of Clark-Lub’s buffer of pH 9 -2, 30 mg of fast red violet LB and 15 ml of distilled water. ACP was stained by incubating the cold formalin-fixed sections over 1 hr in the medium which consisted of 5 mg of naphthol AS-TR phosphate, I5 ml of acetate buffer of pH 5 ‘4, 30 ml of fast red violet LB and 15 ml of distilled water. AChE and ChE were demonstrated with the method of Koelle. The substrate for AChE was acetylthiocholine iodide and that for ChE was butyrylthiocholine iodide. In demonstrating AChE, ChE was inhibited by 10m6 M diisopropylfluorophosphate. Electron-microscopic method The specimens, after glutaraldehyde fixation, were fixed for 1 hr in Millonig fixative (4” C, pH 7*4), dehydrated by immersion in serial concentrations of ethanol, soaked in propylene oxide and embedded in epoxy resin (LUFT, 1961). Ultrathin sections were cut with a LKB Ultrotome and were double-stained by uranyl acetate (WATSON,1958) and by lead acetate (MILLONIG,1961). Sections were examined with a JEM-7 electron microscope.

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RESULTS

Histological jndings

The trigeminal ganglion consisted of the nerve cells surrounded by the capsular cells, nerve fibres covered by the Schwarm cells and capillary vessels. Histologically, three types of nerve cells were distinguishable, i.e., large cells, small cells and intermediate cells. In haematoxylin-stained sections, large cells showed a slight, homogeneous stainability and small cells exhibited an intense stainability especially in the peripheral zones of the perikaria. Some intermediate cells resembled large cells and others resembled small cells as far as stainability to the same dye is concerned. Histochemical &dings

A slight reaction for SDH, MDH and GDH, which was homogeneously distributed in large cells and, in small cells, a moderate or high reaction was confined on the perinuclear area. Intermediate cells varied as to the enzymatic intensity and localization. The capsular cells showed a slight reaction for these dehydrogenases (Figs. l-3). Generally, LDH reaction in the capsular cells was as intense as that in the nerve cell body. The capsular cells were characterized by the presence of the intense stainabilities of NADP-dependent dehydrogenases, i.e., IDH and G6PDH. The nerve cells showed reactions of varying intensity to the NADP-dependent dehydrogenases, while their intracellular distributions were homogeneous. Some nerve cells showed positive MAO reactions of varying intensities and the others were negative. A faint reaction for MAO was also observed in the capsular cells at times (Fig. 4). ALP reaction was limited to the capsular cells and the capillary endothelia (Fig. 5). ACP reaction of moderate or high intensity was exhibited both in nerve cells and capsular cells (Fig. 6). AChE of large cells was slight and was homogeneously distributed. The enzymatic activity of small cells and that in some of intermediate cells was moderately or highly reactive and mainly localized on the peripheral zone of the soma (Fig. 7). The faint or little reaction of ChE was confined to the capsular cells. Electron-microscopic findings

The nerve cell bodies were completely covered by the flattened, attenuated cytoplasm of the capsular cell. The remaining parts of the ganglion were tilled with nerve fibres, myelinated or unmyelinated, and capillary vessels. There were a number of collagen fibres between the outer surfaces of the neighbouring capsular cells and/or the Schwann cells. Two distinct types of nerve cell were discernible, i.e., clear cells and dark cells (Figs. 8 and 9). Besides these, the cells of the transitional type were also present. In clear cells, the discrete clumps of rough-surfaced endoplasmic reticulum and numerous mitochondria were scattered throughout a neuroplasm of low electron density, and a number of free RNP particles were also observed (Fig. 8). In dark cells, the welldeveloped rough-surfaced endoplasmic reticulum was packed in a somewhat peripheral zone of the perikaryon, and free RNP particles were scarce. The mitochondria of

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MATSWRA, MA.C+AHIKO MORI AND KENSAKUKAWAKATSU

dark cells were assembled in the perinuclear area (Fig. 9). In transitional cells, there was a tendency for fusion between the clumps of the rough-surfaced endoplasmic reticulum, especially in the peripheral zones of the perikaryon. Mitochondria tended to be gathered in the neighbourhood of the nucleus. The mitochondria in the nerve cell body were far more numerous than in the capsular cells. There were spherical mitochondria and round or swollen ones (Fig. 10). In the former, the cristae were densely arranged in a direction tangential to the long axis of the mitochondria and, in the latter, it was poorly developed (Fig. 10). However, in the trigeminal ganglion of the 2 week-old rat, the mitochondria of the latter type were scarce. No relationship seemed to be present between the types of the nerve cells and the shape of the mitochondria. The Golgi apparatus of the nerve cells consisted of long flattened cisternae and large and small vesicles. This organelle seemed to be more developed in clear cells than in dark cells (Fig. 8). Lysome-like bodies were present in all types of the nerve cells (Fig. ll), and their localization in the neuroplasm was at random. Some of these bodies contained vacuoles (Fig. 11). The nuclei of the nerve cells had double envelopes and nucleoplasm of low electron-density in which fine chromatin particles were homogeneously dispersed. No characteristic findings in nuclei of the three types of the nerve cells were observed. In the most peripheral zone of the perikarya i.e., just beneath the nerve-cell membrane, large flattened cisternae of low electron-density were at times observed which were irregularly outlined by single membrane and could be interpreted as the “trophospongium” (Fig. 12). At times, smaller cisternae of similar character were also present in deeper portions of the nerve-cell body. These cisternae were usually accompanied by the accumulation of the mitochondria in the neighbourhood (Fig. 12). The capsular cells in the vicinity were characterized by the presence of the well-developed rough-surfaced endoplasmic reticulum and high electron-density. This type of the capsular cell could be called “dark capsular cell”. The cytoplasm of the capsular cells was flattened, or attenuated, with the width of 0 ~2-2 p, and occupied the surface of the nerve-cell body. Two types of the capsular cells were distinguishable, i.e., clear capsular cells and dark capsular cells. The capsular cells enclosing one nerve cell body usually consisted of the cells of both types. Clear capsular cells were characterized by the existence of poorly developed rough-surfaced endoplasmic reticulum, few mitochondria, the absence of the Golgi apparatus and the presence of cytoplasm of low electron-density (Fig. 13). In contrast, the characteristic findings of dark capsular cells were a cytoplasm of high electron-density with a well-developed rough-surfaced endoplasmic reticulum and round-shaped enlargement of the cistern. The Golgi apparatus and a number of the mitochondria were accumulated in the perinuclear zone (Fig. 14). The mitochondria of both capsular cells were different from those of nerve cells in that they had well-developed cristae, were small and of high electron-density. Lysosome-like dense bodies were also present in both types of capsular cells. However, the dense bodies in capsular cells did not contain the vacuoles observed in the nerve cells. The nucleoplasm of the capsular cells was enclosed by a double membrane and had a number of the clumps of chromatin particles concentrated on the peripheral zones of the nucleus. Dark capsular cells were in simple juxtaposition with the nerve-cell surface, while clear capsular cells

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and nerve cells sometimes adjoined with deep interdigitations and invaginations forming a “labyrinthine structure”. Usually a number of the mitochondria of the nerve cells were seen to be accumulated in the neighbourhood of those labyrinthine structures (Fig. 13). The nerve fibres in the ganglion were axonic in structure; i.e., neurofilaments, neurotubules, mitochondria and vacuoles were present but Nissl substance and other cell organelles were absent. The myelinated nerve fibres seemed to exceed the unmyelinated ones in number. The electron-microscopic appearance of Schwann cells was similar to that of the capsular cells, especially that of clear capsular cells. Capillary vessels were not particuarly well-developed in the ganglia. They always adjoined the capsular cells and/or the Schwann cells and never were in direct contact with the neurons (Fig. 15). DISCUSSION

With the light microscope, three types of nerve cell were distinguishable within the ganglion, i.e., large, small and intermediate cells. Similar observations have been made by several workers with regard to various ganglia (HERMANN,1955; TEWARI, 1962; MATSUURA,1967). These three types of the nerve cell were discernible in the ganglion, i.e., clear, dark and transitional cells, by electron microscope. DIXON(1963) has reported “dark type” and “pale type” in the trigeminal ganglion of the rat. In the present study, dark cells are thought to correspond with the neuron of “dark type” and clear cells to correspond with the “pale type”. However, the findings in both dark and clear cells were a little different from those of the neuron of “dark type” and “pale type”. According to Dixon, the number of the mitochondria was larger in “dark type” than in “pale type” and, in the neuron of both types, the mitochondria were seen around the nucleus and the rough surfaced-endoplasmic reticulum was mainly localized in the periphery of the perikaryon. In the present study, no marked differences were observed between dark and clear cells as to the number of the mitochondria. The description of DIXON (1963) was true in the case of dark cells, namely mitochondria were numerous in the perinuclear area and the rough-surfaced endoplasmic reticulum was developed in the peripheral zone of the perikarya. In clear cells, both the mitochondria and clumps of rough-surfaced endoplasmic reticulum were evenly disseminated throughout the perikaryon. The mitochondrial enzymes, especially SDH, MDH and GDH, were somewhat concentrated in the perinuclear area of small cells and diffusely distributed throughout the cytoplasm of large cells. AChE, which has been demonstrated by electron microscopy on the rough-surfaced endoplasmic reticulum or on the ribosomes (KASA, 1967; SHIMIZU,1965), was concentrated in the peripheral area of small cells and was homogeneously distributed in the cytoplasm of large cells. Comparing these histochemical and electron-microscopic findings, it could be concluded that small cells correspond with dark cells, large cells correspond with clear cells and intermediate cells with transitional cells. There is no convincing evidence that nerve cells of these three types ever exist in the living state. MOSES(1963) insisted that the differences are the artifacts. FUJIMOTO

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Hrmo MATSWRA, MA~AHIKO MOIUAND

KENSAKU

KAWAKATSU

(1967), from electron physiological experiments on the sympathetic ganglion of toad, concluded that clear cells are B neurons and dark cells C neurons. Should this theory be applied to the trigeminal ganglion of the rats, two problems will arise, i.e., whether the morphology of the somato-sensory neuron could be explained in the same way as in the sympathetic neuron or not and what is the function of transitional cells ? DEITCH (1956) reported the two types of the nerve cells in the cultured tissue of the spinal ganglion of the chick embryo, i.e., one is the nerve cell of the smaller size which is numerous in the early stage and has Nissl substance concentrated in the peripheral zone of the perikaryon and the other is that of the larger size with the Nissl substance evenly dispersed throughout the perikaryon which increases in number with maturity. He also noted that these structures were well-preserved after fixation. It is quite possible that the small cells in the present study correspond with the nerve cells of smaller size found by Deitch and the large cells with those of larger size. TEWARI(1962) suggested the existence of the metabolic cycle in the rat’s spinal ganglion cell. Therefore, the types of the nerve cell found in the present study are thought to be changeable from one to the other. The number of the mitochondria in the nerve cell body of the trigeminal ganglion of the rat was much greater than in the capsular cells. This difference was confirmed by the histochemical stainability of the mitochondrial dehydrogenases in both cells, i.e., the nerve cell body contained more stainable dehydrogenases than the capsular cell. These findings of the enzymatic reaction were clearly defined in the case of SDH, MDH and GDH reactions. A similar finding was previously reported on the bovine spinal ganglia (MATSUURA,1967). No reaction of SDH was detected in the capsular cell of the rat’s spinal ganglion (T~WARI, 1962) nor in that of the bovine trigeminal ganglion (HERMANN,1952). In contrast to these histochemical findings, HYDEN(1959, 1961, 1962) recorded biological data about the respiration of rabbit’s spinal ganglia suggesting that the SDH activity in the capsular cell was seven times higher than that of the nerve cells of the same volume. Whether these differences may be attributed to the species differences or to the methods used, cannot be affirmed at present. The LDH activity in the capsular cells was as stainable, or more so, than in the nerve cell body. It could be concluded, in the case of trigeminal ganglion of rat, that aerobic oxidation is more active in the nerve cell than in the capsular cell and anaerobic oxidation may be prominent in the capsular cell or oligodendroglia as in the case of the central nervous system. The dense body either in the perikaryon or in the capsular cell should be identified as the lysosome because of its electron-microscopic characteristics and the positive reaction of both cells to ACP. To NADPdependent dehydrogenases, IDH and G6PDH, the capsular cells were intensely stainable in contrast to the cases of the NADdependent mitochondrial dehydrogenases. This finding agrees with LOWRY’S conclusion (1955, 1957) that the hexose monophosphate shunt is more active in the white matter with a large number of oligodendroglia than in the gray matter containing a small number of oligodendroglia. In the capsular cells that are said to be “peripheral oligodendroglia”, the hydrogen from reduced NADP is probably utilized as the reducing power in the synthetic reaction. As there was the intervention of the capsular

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cells and/or the Schwann cell between the capillary vessels and the neuron, these supporting cells are thought to take the role of the transportation of nutrition. Based upon Hokin’s reports (1960), it could be suggested that the ALP in the capsular cells and the AChE demonstrated in the portion corresponding to the cell membrane have something to do with permeability. The “labyrinthine structure” and the “trophospongium” (HONJIN, 1957) seen in clear cells might participate in transportation of substances between clear cells and clear or dark capsular cells. With the electron microscope these structures were not observed in dark cells. Here again, the possibility arises that dark cells transform themselves to transitional or clear cells when necessity requires. In accord with the fact that the sensory nerve is cholinergic in function, AChE activity has been reported in various sensory neurons as well as in the present work. The MAO activity demonstrated in rat’s trigeminal ganglion would suggest the presence of cathecol amines. It would be interesting to know what sort of amines are being oxidized by MAO and what sort of function the enzyme performs. R&nn&Une etude par histochimie enzymatique et par microscopic Blectronique est efle:tt& au niveau du ganglion trigeminal du rat. (1) Trois types de cellules nerveuses peuvent &tre distingues, en microscopic optique, a savoir des cellules grandes, petites et moyermes. Au microscope&ctronique, on note des cellules claims, sombres et des cellules de transition. Le diametre des grandes cellules est d’environ 60 p et celui des cellules sombres est de 30 + Les dtshydrog&tases mitochondriales sont plus nettement visibles dans les corps cellulaires des nerfs que dans les cellules capsulaires. 11en est de meme des mitochondries. Au niveau des cellules sombres, les dbhydrogrlnases mitochondriales sont concentrees dans l&pace p&inucltaire et 1’AchE est principalement localise darts la partie p&ipherique du pericaryon. Dam les grandes cellules, ces enzymes sont diss&nines dans le p&icaryon. La localisation intra-cellulaire des enzymes coincide avec la repartition intra-cellulaire des mitochondries et de l’ergastoplasme rugueux dam le p&icaryon des grandes cellules. Ces cellules semblent identiques aux cellules claims; les petites cellules et les cellules intermediaires correspondent respectivement aux cellules sombres et aux cellules de transition. (21 Les cellules causulaires et celles de Schwann s’etendent entre le neurone et les capillaires. (3) La cellule capsulaire pmsente une forte coloration caracteristique intense aux NADP-IDH. G6PDH et ALP. Deux tvnes de cellules cansulaires claims et sombres, sont visibles au microscope blectronique. A la jonction des d&x types ce cellules caps&&es, on observe des “structures labyrinthiques” et un “trophospongium”, qui peuvent jouer un role de transport nut&if entre les dew cellules. De telles structures ne s’observent pas dam les cellules sombres. (4) 11parait logique d’admettre la possibilite de transformation des divers types de cellules nerveuses du stade de cellule sombre vets celui de cellule claim ZusPmmenfassrmg-Elektronenmikroskopische und enzym-histochemische Untersuchungen fiihrten zu folgenden Ergebnissen : (1) Lichtmikroskopisch lieBen sich 3 Arten von Nervenzellen unterscheiden: GroBe, kleine und mittlere Zellen. Auch elektronenmikroskopisch waren drei Zelltypen differenzierbar: Helle, dunkle und Ubergangszellen. Der Durchmesser der groBen Zellen betrug etwa 60 p, der der dunklen Z%llen etwa 30 p. Die Mitochondrien-Dehvdroaenasen traten in den Nervenxellkbmem mehr als in den kapsuliiren Zellen he&r. Die Mitochondrien waren in den Ner&ellk&pem such xahlreicher. In den dunklen Zellen waren die Mitochondrien-Dehydrogenasen im perinukleiiren Abschnitt konzentriert und AChE fand sich vorwiegend im peripheren Anteil

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H~EO MATSUUIU, MA~AHIKOMom

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KENSAKUKAWAKAT~U

des Perikaryon. Bei den grol3en Zellen waren diese Fermente im gesamten Perikaryon verteilt. Die intrazelluliire Lokalisation der Enzyme stimmte mit der intrazelluliiren Verteilung der Mitochondrien und des rauhfliichigen endoplasmatischen Retikulum im Perikaryon der vorgenannten Nervzelltypen iiberein. Deshalb wird angenommen, da5 die gro5e Zelle mit der hellen, die kleine Zelle mit der dunklen und die mittlere Zelle mit der obergangszelle identisch ist. (2) Die Kapselzelle und/oder die Schwann’sche Zelle lag zwischen Neuronen und Kapillaren. (3) Die Kapselzelle zeigte die charakteristisch hervortretende Farbbarkeit mit NADP-abhangigem IDH, G6PDH und mit ALP. Elektronenmikroskopisch lie5en sich 2 Kapselzelltypen unterscheiden: dunkle und helle Kapselzellen. An der Grenze von hellen Zellen und Kapselzellen fanden sich “labyrinthische Strukturen” und “Trophospongium”; diese Strukturen dtirften fur den Nahrstofftransport zwischen beiden Zellen von Bedeutungsein. Bei den dunklen Zellen wurden solchestrukturen nicht beobachtet. (4) Es gibt Griinde fur die Annahme, da5 in verschiedenen biologischen Stadien eine Transformation der Nervzelltypen von der dunklen zur hellen Zelle stattfindet.

REFERENCES CAJAL, S. R. 1906. Die Struktur der sensiblien Ganglien des Menschen und der Tiere. Ergebn. Anut. Entwgesch. 16, 177-214. DEITCH, A. D. and MURRAY, M. R. 1956. The Nissl substance of living and fixed spinal ganglion cells. 1. A phase contrast study. J. biophys. biochem. Cytol. 2,4334I4. DIXON, A. D. 1963. Fine structure of nerve cell bodies and satellite cells in the trigeminal ganglion. J. dent. Res. 42,990-999. FERNANDEZ,J. 1967. Etude histologique du Gasser Types de neutous et leur frequence. Acra Neuroveg. 29,297-322. FUJIMOTO,S. 1967. Some observations on the fine structure of the sympathetic ganglion of the toad, Bufo vuIgaris japonicus. Archvm histol. jap. 28,313-335. GLENNER,G. R., BURTNER,H. J. and BROWN, G. W. 1957. The histochemical demonstration of monomine oxidase activity by tetrazolium salts. J. Histochem. Cytochem. 5, 591-600. HOKIN, L. E and HOKIN, M. R. 1960. The role of phosphatidic acid and phosphoinositide in transmembrane transport elicited by acetylcholine and other humoral agents. Znt. Rev. Neurobiol. 2, 100-133. HOKIN, L. E. and SHELP, W. D. 1960. The effect of acetylcholineon the turnover of phospatidic acid and phosphoinositide in sympathetic ganglia and in various parts of the central nervous system in vitro. J. gen. Physiol. 44, 217-226. HONJIN, R. 1957 The electron microscopic study on the nervous system. Sogo Zgaku 14, 53-64 (in Japanese). HYDEN, H. 1959. In: Biochemistry ofthe Central Nervous System. Proc. 4th Intern. Congr. Biochem., Vol. III (edited by BR~CKE), Pergamon Press, Oxford. HYDEN, H. and LANGE, P. 1961. In: Regional Neurochemistry (edited by Ksrv, S. S. and ELKE~J.) Pergamon Press, Oxford. HYDEN,H. 1962. The neuron and its glia-a biochemical and functional unit. Endeavour 21,144-155. JOACHIM-HERMANN, S. and CLYDE,P. R. 1958. Zur Verteilung der Kohlenhydrate und einiger Fermente im Ganglion Semilunare des Rindes. Acta histochem. $129-145. KASA, P. and ~SERNOVSZKY,E. 1967. Electron microscopic localization of acetylcholinesterase in the superior cervical ganglion of the rat. Acta histochem. 28,274-285. LoWRY, 0. H. 1955. In: Biochemistry of the Developing Nervous System (edited by WAELSH,M.), Academic Press, New York. LOWRY, 0. H. 1957. In: Metabolism of the Nervous System (edited by RICHTERD.) Pergamon Press, Oxford. LUFT, J. H. 1961. Improvements in epoxy resin embedding methods. J. biophys. biochem. Cytol. 9, 409-414. MATSUURA,H. 1967. Histochemical observation of bovine spinal ganglia. Histochemie 11, 152-160. MICHAEL, L. and WATSON,PH. D. 1958. Staining of tissue sections for electron microscopy with heavy metals. J. biophys. biochem. Cytol. 4,475-478.

TRIGEMINAL GANGLION MILLONIG,G. 1961. A modified procedure Cytol. 11, 736-739. MILU)NIG, G. 1962.

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for lead staining of thin sections. J. biophys. biochem.

l&267-28I. A. G. E. 1960 In: Histochemistry, TheoreticaI and Applied. Churchill, London. SHIMIZIJ, N. and ISHII, S. 1966. Electron microscopic histochemistry of acetylcholinesterase of rat brain by Kamovsky’s method. Histochemie 6,24-33. TEWARI,H. B. and BOURNE,G. H. 1962. Histochemical studies on the distribution of &glycuronidase and succinate dehydrogenase in young and old spinal ganglion cells of rat. 2. Zellforsch. mikrosk. Anat. S&70-75. TEWARI, H. B. and BOURNE,G. H. 1962. Histochemical evidence of metabolic cycles in the spinal ganglion cells of rat. J. Histochem. Cytochem. 10, 42-64. TEWARI,H. B. and BGURNE, G. H. 1963. Histochemical studies on the distribution of simple esterase, specific and non-specific cholinesterase in trigeminal ganglion cells of rat. Actu unut. 53,319-332. F%ARSE,

PLATF.~l-5 OVERLEAF

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Hroao MATSWRA, MASAHIKOMORI AND KENSAKUKAWAKATSU

FIG. 1. Large cells with homogeneous stainability. Little reaction is seen on the capsular cells. Succinate dehydrogenase.

x 400

FIG. 2. Small cells showing high enzymic reaction in the perinuclear

Succinate dehydrogenase.

area. SC: small cell.

x 400

FIG. 3. Large cells and small cells. The stainability

of both cells are similar to those in Figs. 1 and 2. LC: large cell. Malate dehydrogenase. x 400

FIG. 4. The enzymic reaction

is present on the nerve fibre and in some of the nerve cells. MF: Nerve fibre. P: Nerve cell with positive reaction. Monoamine oxidase. x 200

FIG. 5. Capsular cell with positive reaction. The nerve cell bodies are devoid of enzymic reaction. Alkaline phosphatase. x 400 FIG. 6. Enzymic reaction of moderate

intensity is seen both in nerve cells and capsular cells. Acid phosphatase. x 400

FIG. 7. In large cells, the enzyme is homogeneously stained and in small cells it is concentrated in the peripheral zone of the soma.

LC: large. cell, SC: Small cell. Acetylcholinesterase.

x 200

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HIDEO MATSUURA, MA~AHIKO MORI AND KENSAKU KAWAKATSU

PLATE 2

TRIGI?MlNAL

GANGifON

OF RAT

RATE 2 FIG.8. Part of a clear cell. The clumps of the rough-surfaced endoplasmic reticulum and the mitochondria am randomly distributed in neuroplasm of low electron density. RER: Rough-surfaced endoplasmic reticulum. M: Mitochondria, G: Golgi apparatus, D: Dense body, CC: Capsular cell, NC: Nucleus of capsular cell. x 10,000

FIG. 9. Part of azdark cell. Well developed rough-surfaced endoplasmic reticulum is seen on the peripheral area of the soma and mitochondria are present in the perinuclear zone. Nn: Nucleus of nerve cell. x 6200

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HIDEO MATSUURA, MA~AHIKOMORI AND KENSAKU KAWAKAWJ

PLATE 3 FIG. 10. Two nerve cells and the capsular cells. The mitochondria in the nerve cell on the left are spherical with well-developed cristae whereas those on the right are swollen or round and have poorly developed cristae. Both neurons are clear cells, NC: Nerve cell, K: Collagen

fibre. x 8300 FIG. 11. Higher magnification FIG. 12. Trophospongium.

of lysosome-like

dense body.

x 20,000

Numerous mitochondria in the neighbourhood T: Trophospongium. x 16.000

of the structure.

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FIG. 13. Labyrinthine structure on the junction between clear cell and clear L: Labyrinthine structure CCC: Clear capsular cell. x 17,000

PLATE 4

capsular

cell.

TRIGEMINAL GANGLION OF RAT

endoplasmic reticulum and FIG. 14. Dark capsular cell. Well-developed rough-surfaced Golgi apparatus are seen in cytoplasm of high electron-density. DCC: Dark capsular cell x ll,ooo FIG. 15. Capillary vessel and nerve cell. A capsular cell intervenes between the soma and the endothelium. E: Endothelium, BM: Basement membrane, B: Blood cell. x 12,000 PLATE 5