Acta Path. Jap. 27(4): 527-531,
1977
A MORPHOLOGICAL STUDY ON T H E PINEAL GLAND OF HUMAN EMBRYO
Katsuniaro KURUMADO and Wataru MORI Department of Pathology, Faculty of Medicine, Univeraity of Tokyo, Tokyo (Received on Aug. 30, 1976)
The pineal glands obtained from two human fetuses were studied morphologically. Light microscopic examinations revealed its structure a s an organ consisting of tall or cuboidal cells with a lumen at the center. The most striking finding was obtained through electron microscopic observation, which was cilia formation by the pinealocyte. The cilium was seen quite often, definitely of 9+0 pattern, associated by satellite bodies and rootlet structure. These features are considerably different from those in the human adult but quite similar to those of some species of lower animals, which would also endorse the sensory nerve origin of the pineal glands in man. ACTA PATH. JAP. 27: 527-531, 1977.
Introduction The pineal gland is one of the organs in which the function still remains niysterious so far to date. To know the real role played by this particular organ in human physiology and pathology, it should be of great help to investigate its nature from a phylogenetical view point, and this is the reason why we are also much interested in the biological, comparative study of the pineal organ. Morphological studies on the pineal organ along this line have been made by a considerable number of researchers, and many results have been reported so far. However, as far as we know, most of these studies were done with lower animals and only a few on mammals. We were fortunate in having had a chance to examine the pineal gland of two human fetuses morphologically, and have obtained some results which, we believe, should provide an interesting information concerning the nature and function of this organ in man.
Materials and Methods One of the materials used for this study was a male fetus, four months of gestation age (CRlength 63 mm), who happened to have been taken out with his mother’s uterus bearing a huge myoma which was too large and too badly influential for the host to leave untreated. The other
Plt %@> & ?a Mailing address: Wataru MORI Department of Pathology, Faculty of Medicine, University of Tokyo. 7-3-1, Hongo, Bunkyo-ku, Tokyo, Japan (113) This work was supported by a Grants in-Aid from the Japanese Ministries of Education, Science and Culture, and of Health and Welfare. 527
528
THE PINEAL IN HUMAN EMBRYO
Aeta Path. Jap.
case was also a male fetus of four months gestation age (CR-length 62 mm) obtained from a remarkably enlarged uterus due to myoma and adenomyosis which had to be surgically operated. These fetuses were immersed in 10% formalin solution as soon as possible after operation, where they were left for two days, the pined gland was removed and then transferred into 2.5% glataraldehyde solution. Sagittal sections were re-fixed by osmic acid, embedded in Luft’s Epon mixture, ultrathin-sectioned with a Porter-Blum’a ultramicrotome, double-stained by uranyl acetate and lead acetate, and then observed with an electron microscope (JEM-6c). Some histological slides were made from a part of the embedded material and examined with a light microscope, partly for the purpose of trimming.
Results
Through light niicroscopic examinations, the pineal gland was observed as an organ sack-formed or of tubular structure, showing a lumen of a considerable size at the center. There were some lobulations in the parenchyma which consisted of tall or cuboidal cells packed densely to each other. The former, tall cells, were found lining with some regularity along the surface of the lumen, while the latter, cuboidal cells, occupied mainly the peripheral area, and a transition between the two was seen. There were numerous projections on the free surface of the cells composing the wall of the lumen. The nuclei were round t o oval, frequently containing small nucleoli. Blood vessels were abundant in the surrounding area, loose connective tissue. The above described is far different from the pineal structure of human adult, but rather similar to that of some fishes or reptiles. The quality of the specimens were not too good for electron microscopic exaniination because of poor fixation, but they were still usable for ultrastructural analysis to some extent. The majority of the cells consisted of rather clear cells with sparse organellae, aniong which rough surfaced endoplasmic reticulum was relatively the most prominent. The most interesting and important finding was cilia formation by the cell which was seen quite often in both cases. The cilium was observed as a straight structure vertically projecting from the cell surface, the root of which occasionally showed a characteristic feature, round-tipped rods, to be called satellite bodies. The so-called rootlet structure was also seen. It was not rare to encounter cross sections of the cilia, which clearly showed the picture of 9+0 pattern, the structure believed to be specific for the sensory cells of the nervous system. (Figs. 1-6) Discussion, There is a possibility that the cilium of 9+2 pattern could change, artificially, in some instances during the procedures for preparing ultrathin sections, and be observed as 9+0 consequently. In our specimens, however, there were some 9+2 cilia remaining as they were seen in the adjacent area, near the ependymal tissue, and this finding could be considered as a good control to avoid the above described case of misinterpretation. On the other hand, the existence of a small number of 9+0 cilia does not always point to the sensory nerve origin of the tissue, so it must be stressed here that there were enough number of 9+0 cilia in our specimens. It has been almost accepted that the pineal organ is of sensory nerve origin,
2T(4): 1977
K . KURUMADO AND W. MORI
529
Fig. 1. A cilium with satellite bodies (basal feet) a t the root (basal body), where microtubules are seen running through. An oblique centriole i R found a t the bottom of the picture. Case. 1. x 20,000. Fig. 2. Basal body and t-~cross-section of a cilium. Striated ciliary rootlet is shown in the former, and 9+0 pattern is demonstrated in the latter. Case 1. x 33,000. Fig. 3. Another cross-section of a cilium showing a typical picture of 9 + 0 pattern. Case 1. x 33,000.
phylogenetically, and many morphological evidences supporting this hypothesis have been clearly shown with lower animals. Among these a study made by DENDY(1910)3 on Sphenodon punctatus is especially well-known, which was later followed by observations with higher animals up to the mammals. Studies made on the rat'V and
530
THE PINEAL IN RUMAN EMBRYO
Acta Path. Jap.
Fig. 4. A group of pinealocytes, some of which contain prominent microtubules. A cilium and its root (basal body) are shown a t the left, another basal body is seen a t the right. Case 2. x 20,000. Fig. 5. A cross-section of a cilium found in an area near Fig. 4. Case 2. x 33,000. Fig. 6. Another cross-section of a cilium, of 9+0 pattern, on the saddle-formed cell surface. Case 2. x 33,000.
27(4): 1977
K. KURUMADO AND W. MORI
531
cattle1 are the only ones which clearly demonstrated the existence of sensory cilia in the pineal gland of mammals in normal condition, and no such reports have been made so far with the human material. In the present study we have succeeded in revealing an interesting picture, 9+0 cilia formation, in the pineal cell of human fetus, which should be an appreciable evidence showing its sensory nerve origin even in man. Before reaching any final conclusion, it seems to be necessary to obtain a picture which would consist of such cilia together with synaptic vesicles, or synaptic ribbons surrounded by synaptic vesicles, at the opposite pole of the cell. Unfortunately, we were unable to see this sort of typical pattern in our specimens, since synaptic vesicles are so fragile and easily destroyed that they usually disappear in a poorly fixed condition. Instead, we4 have confirmed the existence of synaptic ribbon surrounded by synaptic vesicles in a pineal gland of a girl of 3 years of age which was obtained a t autopsy performed 2 hours after death, but where we could see no 9+0 cilia at all. We have not found this type of cilium in the pineal gland of the adult either, and further study is needed to confirm the period of disappearance of such a feature during development. It should also be pointed out that the satellite body observed in this study was quite similar to that appearing in the retinal tissue which was described by TOKUYASUet al.,5 admitting on the other hand that this is not an absolutely specific feature for the eye. The above described findings seem to afford good information in supporting the sensory nerve origin of the pineal gland also in man, and would endorse the theory ontogeny is a recapitulation of phylogeny” in the pineal organ. This would unquestionably give some influence to the future study of the physiology and pathology of the pineal gland in man. (6
Acknozuledgement: We are grateful to Dr. I. KINO for providing us a part of the material for this study, and to Mr. S. IWASAKA for technical assistance.
References The anatomy of bovine and ovine pineals (Light and electron microscopic studies). J. Ultrastruct. Res. Suppl. 8: 1-80, 1965. CLABOUQH,J.W.: Cytological aspects of pineal development in rats and hamsters. Amer. J. Anat. 33: 215-229, 1973. DENDY,A.: 0s the structure, development and morphological interpretation of the pineal organs and adjacent part of the brain in the tuatara (Sphenodon punctatus). Philos. Trans. R. SOC.Lond. (Ser. B) 201: 227-331, 1910. KURUMADO, K., and MORI, W.: Synaptic ribbon in the human pinealocyte, Acta Path. Jap. 26: 381-384, 1976. E.: The fine structure of the retina studied with the electron TOKUYASU, K., and YAMADA, microscope. J. Biophys Biochem. Cytol. 6 : 22g-230, 1959. ZIMMERMAN, B.L., and TSO, M.O.M. : Morphologic evidence of photoreceptor differentiation of pinealocytes in the neonatal rat. J. Cell Biol. 66: 60-75, 1975.
1. ANDERSON,E.:
2. 3.
4. 5.
6.
1977
A MORPHOLOGICAL STUDY ON T H E PINEAL GLAND OF HUMAN EMBRYO
Katsuniaro KURUMADO and Wataru MORI Department of Pathology, Faculty of Medicine, Univeraity of Tokyo, Tokyo (Received on Aug. 30, 1976)
The pineal glands obtained from two human fetuses were studied morphologically. Light microscopic examinations revealed its structure a s an organ consisting of tall or cuboidal cells with a lumen at the center. The most striking finding was obtained through electron microscopic observation, which was cilia formation by the pinealocyte. The cilium was seen quite often, definitely of 9+0 pattern, associated by satellite bodies and rootlet structure. These features are considerably different from those in the human adult but quite similar to those of some species of lower animals, which would also endorse the sensory nerve origin of the pineal glands in man. ACTA PATH. JAP. 27: 527-531, 1977.
Introduction The pineal gland is one of the organs in which the function still remains niysterious so far to date. To know the real role played by this particular organ in human physiology and pathology, it should be of great help to investigate its nature from a phylogenetical view point, and this is the reason why we are also much interested in the biological, comparative study of the pineal organ. Morphological studies on the pineal organ along this line have been made by a considerable number of researchers, and many results have been reported so far. However, as far as we know, most of these studies were done with lower animals and only a few on mammals. We were fortunate in having had a chance to examine the pineal gland of two human fetuses morphologically, and have obtained some results which, we believe, should provide an interesting information concerning the nature and function of this organ in man.
Materials and Methods One of the materials used for this study was a male fetus, four months of gestation age (CRlength 63 mm), who happened to have been taken out with his mother’s uterus bearing a huge myoma which was too large and too badly influential for the host to leave untreated. The other
Plt %@> & ?a Mailing address: Wataru MORI Department of Pathology, Faculty of Medicine, University of Tokyo. 7-3-1, Hongo, Bunkyo-ku, Tokyo, Japan (113) This work was supported by a Grants in-Aid from the Japanese Ministries of Education, Science and Culture, and of Health and Welfare. 527
528
THE PINEAL IN HUMAN EMBRYO
Aeta Path. Jap.
case was also a male fetus of four months gestation age (CR-length 62 mm) obtained from a remarkably enlarged uterus due to myoma and adenomyosis which had to be surgically operated. These fetuses were immersed in 10% formalin solution as soon as possible after operation, where they were left for two days, the pined gland was removed and then transferred into 2.5% glataraldehyde solution. Sagittal sections were re-fixed by osmic acid, embedded in Luft’s Epon mixture, ultrathin-sectioned with a Porter-Blum’a ultramicrotome, double-stained by uranyl acetate and lead acetate, and then observed with an electron microscope (JEM-6c). Some histological slides were made from a part of the embedded material and examined with a light microscope, partly for the purpose of trimming.
Results
Through light niicroscopic examinations, the pineal gland was observed as an organ sack-formed or of tubular structure, showing a lumen of a considerable size at the center. There were some lobulations in the parenchyma which consisted of tall or cuboidal cells packed densely to each other. The former, tall cells, were found lining with some regularity along the surface of the lumen, while the latter, cuboidal cells, occupied mainly the peripheral area, and a transition between the two was seen. There were numerous projections on the free surface of the cells composing the wall of the lumen. The nuclei were round t o oval, frequently containing small nucleoli. Blood vessels were abundant in the surrounding area, loose connective tissue. The above described is far different from the pineal structure of human adult, but rather similar to that of some fishes or reptiles. The quality of the specimens were not too good for electron microscopic exaniination because of poor fixation, but they were still usable for ultrastructural analysis to some extent. The majority of the cells consisted of rather clear cells with sparse organellae, aniong which rough surfaced endoplasmic reticulum was relatively the most prominent. The most interesting and important finding was cilia formation by the cell which was seen quite often in both cases. The cilium was observed as a straight structure vertically projecting from the cell surface, the root of which occasionally showed a characteristic feature, round-tipped rods, to be called satellite bodies. The so-called rootlet structure was also seen. It was not rare to encounter cross sections of the cilia, which clearly showed the picture of 9+0 pattern, the structure believed to be specific for the sensory cells of the nervous system. (Figs. 1-6) Discussion, There is a possibility that the cilium of 9+2 pattern could change, artificially, in some instances during the procedures for preparing ultrathin sections, and be observed as 9+0 consequently. In our specimens, however, there were some 9+2 cilia remaining as they were seen in the adjacent area, near the ependymal tissue, and this finding could be considered as a good control to avoid the above described case of misinterpretation. On the other hand, the existence of a small number of 9+0 cilia does not always point to the sensory nerve origin of the tissue, so it must be stressed here that there were enough number of 9+0 cilia in our specimens. It has been almost accepted that the pineal organ is of sensory nerve origin,
2T(4): 1977
K . KURUMADO AND W. MORI
529
Fig. 1. A cilium with satellite bodies (basal feet) a t the root (basal body), where microtubules are seen running through. An oblique centriole i R found a t the bottom of the picture. Case. 1. x 20,000. Fig. 2. Basal body and t-~cross-section of a cilium. Striated ciliary rootlet is shown in the former, and 9+0 pattern is demonstrated in the latter. Case 1. x 33,000. Fig. 3. Another cross-section of a cilium showing a typical picture of 9 + 0 pattern. Case 1. x 33,000.
phylogenetically, and many morphological evidences supporting this hypothesis have been clearly shown with lower animals. Among these a study made by DENDY(1910)3 on Sphenodon punctatus is especially well-known, which was later followed by observations with higher animals up to the mammals. Studies made on the rat'V and
530
THE PINEAL IN RUMAN EMBRYO
Acta Path. Jap.
Fig. 4. A group of pinealocytes, some of which contain prominent microtubules. A cilium and its root (basal body) are shown a t the left, another basal body is seen a t the right. Case 2. x 20,000. Fig. 5. A cross-section of a cilium found in an area near Fig. 4. Case 2. x 33,000. Fig. 6. Another cross-section of a cilium, of 9+0 pattern, on the saddle-formed cell surface. Case 2. x 33,000.
27(4): 1977
K. KURUMADO AND W. MORI
531
cattle1 are the only ones which clearly demonstrated the existence of sensory cilia in the pineal gland of mammals in normal condition, and no such reports have been made so far with the human material. In the present study we have succeeded in revealing an interesting picture, 9+0 cilia formation, in the pineal cell of human fetus, which should be an appreciable evidence showing its sensory nerve origin even in man. Before reaching any final conclusion, it seems to be necessary to obtain a picture which would consist of such cilia together with synaptic vesicles, or synaptic ribbons surrounded by synaptic vesicles, at the opposite pole of the cell. Unfortunately, we were unable to see this sort of typical pattern in our specimens, since synaptic vesicles are so fragile and easily destroyed that they usually disappear in a poorly fixed condition. Instead, we4 have confirmed the existence of synaptic ribbon surrounded by synaptic vesicles in a pineal gland of a girl of 3 years of age which was obtained a t autopsy performed 2 hours after death, but where we could see no 9+0 cilia at all. We have not found this type of cilium in the pineal gland of the adult either, and further study is needed to confirm the period of disappearance of such a feature during development. It should also be pointed out that the satellite body observed in this study was quite similar to that appearing in the retinal tissue which was described by TOKUYASUet al.,5 admitting on the other hand that this is not an absolutely specific feature for the eye. The above described findings seem to afford good information in supporting the sensory nerve origin of the pineal gland also in man, and would endorse the theory ontogeny is a recapitulation of phylogeny” in the pineal organ. This would unquestionably give some influence to the future study of the physiology and pathology of the pineal gland in man. (6
Acknozuledgement: We are grateful to Dr. I. KINO for providing us a part of the material for this study, and to Mr. S. IWASAKA for technical assistance.
References The anatomy of bovine and ovine pineals (Light and electron microscopic studies). J. Ultrastruct. Res. Suppl. 8: 1-80, 1965. CLABOUQH,J.W.: Cytological aspects of pineal development in rats and hamsters. Amer. J. Anat. 33: 215-229, 1973. DENDY,A.: 0s the structure, development and morphological interpretation of the pineal organs and adjacent part of the brain in the tuatara (Sphenodon punctatus). Philos. Trans. R. SOC.Lond. (Ser. B) 201: 227-331, 1910. KURUMADO, K., and MORI, W.: Synaptic ribbon in the human pinealocyte, Acta Path. Jap. 26: 381-384, 1976. E.: The fine structure of the retina studied with the electron TOKUYASU, K., and YAMADA, microscope. J. Biophys Biochem. Cytol. 6 : 22g-230, 1959. ZIMMERMAN, B.L., and TSO, M.O.M. : Morphologic evidence of photoreceptor differentiation of pinealocytes in the neonatal rat. J. Cell Biol. 66: 60-75, 1975.
1. ANDERSON,E.:
2. 3.
4. 5.
6.
