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Formaldehyde-induced appearance of septate junctions between digestive vacuoles
TISSUE
& CELL
1978 10 (4) 735740
Published by Longman Group Ltd. Printed in Great Britain
MANUEL
NISTAL,
FORMALDEHYDE-INDUCED SEPTATE JUNCTIONS VACUOLES
EDUARDO
L. RODRiGUEZ-ECHANDi-A and RICARDO PANIAGUA
APPEARANCE OF BETWEEN DIGESTIVE
ABSTRACT. Tissue biopsies from (1) some chronic inflammatory diseases, (2) a necrotic tumoral process, (3) normal human lymphatic ganglia, and (4) two congenital diseases of the adrenal cortex were selected for study. A block from each biopsy was fixed in glutaraldehyde-paraformaldehyde; a second block was fixed in 10% formaldehyde. In all cases septate junctions between digestive vacuoles did occur in phagocytic cells and some adrenal cortex cells fixed in formaldehyde. These junctions were similar to those reported recently for malakoplakia phagocytes. Consistently, they were not found to attach organelles other than lysosomes derivatives. Both phagocytes and adrenal cortex cells in the material fixed in glutaraldehyde-paraformaldehyde did not display adhesive specializations between digestive vacuoles. This suggests that the septate junctions described herein are artifactuous structures induced by formaldehyde. There is, however, a certain degree of specificity of cells having the capability of developing these septate junctions. It is assumed that the coating material of digestive organelles in phagocytes and some other cells would be responsible for both cell specificity and organelle specificity of the formaldehyde-induced septate junctions.
tion of cytoplasmic organelles and may be induced by anoxia and other harmful condiSEPTATEjunctions between digestive vacuoles tions (Bulger and Trump, 1968; Saito ef al., have been described recently for phagocytic 1974). Such might also be the case for the ceils in a chronic inflammatory disease septate junctions between digestive vacuoles. referred to as malakoplakia (Nistal et al., These were found in tissue biopsies fixed by 1978). They resemble the septate desmosomes immersion in formaldehyde, and occur often found between cells of invertebrates. together with a variety of fixation artifacts These particular junctions would be involved (Nistal et al., 1978). However, phagocytic in cell-to-cell attachment (Friend and Gilula, cells were the only ones showing digestive 1972), but the evidence connecting them to vacuoles joined by septate junctions. Tissue low-resistance coupling is largely circumfixation may not be the sole reason involved stantial (Hudspeth and Revel, 1971). Intrain the appearance of these peculiar structures mitochondrial and intermitochondrial septate (Nistal et al., 1978). junctions have been reported for certain cells With the aim of determining whether such in mammals (Pearse and Welsch, 1968). junctions (a) are artifactuous or real comHowever, there is some evidence suggesting ponents and (b) if they are peculiar to that they are artifactuous structures. They malakoplakia phagocytes, tissue biopsies coexist, in general, with swelling and distorwere obtained from several tissues containing cells with abundant digestive organelles. It Departamento de Morfologia, Facultad de was found that septate junctions between Medicina, Universidad Autbnoma, C/Arzobispo digestive organelles occur in phagocytes from Morcillo, 4, Madrid-34, Spain. normal and pathological biopsies, as well as Received 22 May 1978. in some other formaldehyde-fixed cells. These Revised 25 June 1978. 735 Introduction
136
NISTAL.
RODRfGUEZ-ECHANDfA
peculiar attachment devices are not apparent in the cells fixed in glutaraldehyde-paraformaldehyde. Materials and Methods Human tissues containing abundant macrophages or other cell types bearing a large complement of digestive organelles were selected for study. Each biopsy or tissue sample was cut into three blocks which were processed as follows : (a) Light microscopy. One block was fixed by immersion in a solution of 10% formaldehyde with 1% ClNa (24 hr), embedded in paraffin and stained with haematoxylin and eosin for routine disease diagnosis. The material was identified with (1) Chronic granulomatous disease (two biopsies from both liver and lymphatic ganglia). (2) Lymphoma (one biopsy from a lymphatic ganglion). (3) Leiomyosarcoma (one biopsy from the small intestine). (4) Normal lymphatic ganglia (three biopsies). (5) Congenital lipoid hyperplasia of the adrenal gland and adrenal cytomegalia (tissue samples obtained from necropsies).
AND
PANIAGUA
(b) Electron microscopy. A second block from each biopsy or necropsy was fixed by immersion in the Karnovsky (1965) mixture of glutaraldehydeparaformaldehyde (4 hr at 3°C). The third block was fixed in a 10% formaldehyde solution (24 hr) with 1% ClNa added, rinsed in cacodylate buffer and immersed in the Karnovsky solution (4 hr) for additional fixation. The material from both groups was postfixed in 1% 0~04, dehydrated in ethanol and embedded in Epon-812. The ultrathin sections were stained with uranyl acetate and lead citrate and studied in a Philips EM 300. Results 1. Glutaraldehyde-paraformaldehyde-fixed material. Good preservation of cell fine structure was observed in the lymphatic ganglia and the intestinal wall biopsies that were processed with the Karnovsky fixative. The same applies to the adrenal tissue samples, though these were obtained several hours after death and showed some distortion due to postmortem phenomena. Abundant digestive bodies were observed in phagocytic cells from normal lymphatic
Fig. 1. Glutaraldehyde-paraformaldehyde-fixed phagocytic cell in a ganglion biopsy from a chronic granulomatous disease showing cluster of digestive vacuoles (D). They are close to one another (arrows) but are not joined by septate junctions. m, mitochondria. x 14,000. Fig. 2. Glutaraldehyde-paraformaldehyde-fixed from lymphoma showing different steps of vacuole are not apparent. x 70,000.
phagocyte in a ganglion biopsy fusion (1, 2, 3). Septate junctions
Fig. 3. Formaldehyde-fixed phagocyte in a lymphatic ganglion chronic granulomatous disease. The digestive organelles appear junctions (arrows). x 35,000.
from a patient with attached by septate
Fig. 4. Formaldehyde-fixed phagocyte in a lymphatic ganglion from a patient with chronic granulomatous disease showing the microfilamentous coat of the digestive organelles (small arrows). It is apparently involved in septate junctions formation (large arrows). x 80,000. Fig. 5. A septate junction between two digestive vacuoles (1, 2) in a formaldehydefixed phagocyte of a lymphatic ganglion biopsy from a chronic granulomatous disease. Periodical septa are seen at the cleft (arrows). x 80,000. Fig. 6. Formaldehyde-fixed phagocyte in a ganglion biopsy from a chronic granulomatous disease showing a cluster of mitochondria. Septate junctions are not apparent between these organelles (arrows). The area enclosed in the rectangle is illustrated at higher magnification by the inset. x 48,000; inset x 85,000.
738
NISTAL,
RODRfGUEZ-ECHANDiA
ganglia, chronic granulomatous disease, lymphoma and leiomyosarcoma. Such organelles are heterogeneous in shape and are comprised of lysosomes, phagolysosomes and cytolysosomes. Though most of these components appeared in close topographical relation to one another, adhesive specializations were not apparent between them (Fig. 1). Instead, direct contracts of the outer aspect of their membrane boundaries or even intermediate images of vacuole fusion were often seen (Fig. 2). Abundant lysosome derivatives were also found in the adrenal cortex cells of zona fasciculata and zona reticularis in tissue samples from congenital lipoid hyperplasia and cytomegalia. As phagocytic cells, the adrenal cells did not display adhesive specializations between the digestive vacuoles.
2. Formaldehyde-fixed material. The electron microscopy analysis of the formaldehydefixed phagocytic cells from the normal lymphatic ganglia as well as from the chronic inflammatory diseases and from the periphery of the leiomyosarcoma reported above, showed clamping of digestive vacuoles, mitochondria and other cytoplasmic organelles. Most digestive vacuoles appeared attached to one another by typical septate junctions (Fig. 3), similar to those reported for malakoplakia phagocytes (Nistal et al., 1978). In addition, nearly all phagocytes displayed lysosomes invested by radial strands of considerable electron density (Fig. 4). Such coating material is apparently involved in the attachment of these organelles to one another (Figs. 3, 5). A cluster of swollen mitochondria in a phagocytic cell fixed in formaldehyde is illustrated in Fig. 6. The cleft between these mitochondria may be as narrow as 100 A. However, septate junctions never occurred between the apposing membranes. These junctions are peculiar to digestive vacuoles. Interestingly, specialized junctions between dense bodies were found neither in the neutrophilic and eosinophilic leucocytes nor in the plasma cells interspersed with the macrophages. As to the formaldehyde-fixed adrenal tissue samples, septate junctions between digestive vacuoles were also found in the adrenal cells of zona fasciculata and zona reticularis. These adhesive devices were
similar to those phagocytes.
AND
reported
PANIAGUA
above
for the
Discussion The occurrence of septate junctions between digestive vacuoles was reported previously for phagocytic cells in human malakoplakia (Nistal et al., 1978). Present findings extend such observations not only to phagocytes in other chronic inflammatory diseases or in the vicinity of a necrotic tumoral tissue (leiomyosarcoma) but also to macrophages in normal lymphatic ganglia. On the other hand, the occurrence of septate junctions between dense bodies in adrenal cortex cells supports the view that such devices are not unique for phagocytes. These septate junctions are similar to the septate desmosomes involved in cell-to-cell attachment (Hudspeth and Revel, 1971; Friend and Gilula, 1972). However, the septate junctions between digestive organelles were peculiar to the preparations fixed in formaldehyde; they did not appear in equivalent cells when they were fixed in glutaraldehyde-paraformaldehyde. Therefore, tissue fixation is undoubtedly involved in the appearance of such structures. When interpreting these results, two possibilities come to mind: (1) The septate junctions may be artifactuous structures induced by formaldehyde or (2) they artifactuously disappear in the cells fixed with glutaraldehyde-paraformaldehyde. The first alternative seems more likely to us. In general, great distortions having no basis in the living cells are not produced by the Karnovsky mixture of glutaraldehyde-paraformaldehyde. The formaldehyde-fixed tissue blocks, but not those fixed in the Karnovsky solution, showed organelle clamping and swelling of mitochondria. These features in other cell types are currently regarded as fixation artifacts. In addition, it has been reported that intramitochondrial and intermitochondrial septate junctions may be induced by several conditions causing tissue damage (Bulger and Trump, 1968; Saito et al., 1974). In the biopsies from the formaldehydefixed lymphatic ganglia and leiomyosarcoma, only phagocytic cells exhibited the septate junctions in question. The oesinophilic and neutrophilic leucocytes, as well as the plasma cells interspersed among them, did not show septate structures between dense bodies.
FORMALDEHYDE-INDUCED
SEPTATE
Their organelles, however, appeared just as clamped and distorted as in the phagocytic cells. This suggests the existence of some degree of especificity of cells having the capability of developing septate junctions when fixed under certain conditions. Certainly, the artifactuous clamping of cytoplasmic components by formaldehyde contributes to formation of septate junctions between digestive organelles but it is not the sole condition involved. Such would also be the case for the septate junctions between mitochondria, described by Watanabe et al. (1976). Another point which deserves to be discussed is the selectivity of these septate junctions for digestive organelles. The fact that these structures were never found between adjacent mitochondria or between mitochondria and digestive vacuoles in the formaldehyde-fixed cells. A reasonable explanation is that such organelles are invested by a material which, when reacting with formaldehyde, may produce septate junc-
JUNCTIONS
739
tions. A coating material having a honeycomb pattern was reported for lysosome derivatives in malakoplakia phagocytes fixed with formaldehyde (Nistal et al., 1978). In the present work, coating microfilaments were detected on the lysosomes. These were found to articulate with similar components investing adjacent lysosomes in a way suggesting intermediate stages in the formation of septate junctions. One tends to speculate, therefore, that in the absence of a peculiar coating material, formaldehyde fails to induce the formation of septate junctions between cytoplasmic organelles. Digestive organelles in phagocytes and other cells (adrenal cortex cells) would be invested by this matter, whereas this would not occur in adjacent cells of different types (leucocytes, plasma cells). The septate junctions described herein might be artifactuous in nature but may well be an expression of important differences between digestive vacuoles in different cell types.
740
NISTAL,
RODRIGUEZ-ECHANDfA
AND
PANIAGUA
BULGER, R. E. and TRUMP, B. F. 1968. Structure of coupled and uncoupled cell junctions. J. Cell Bid., 37, 621-632. FRIEND, D. S. and GILULA, N. B. 1972. Variations in tight and gap junctions in mammalian tissues. J. CeN Bid., 53, 758-776. HUDSPETH, A. J. and REVEL, J. P. 1971. Coexistence of gap and septate junctions in an invertebrate epithelium. J. Cd Bid., 50, 92-101. KARNOVSKY, M. J. 1965. A formaldehyde-glutaraldehyde fixative of high osmolality for use in electron microscopy. J. Cell Bid., 27, 137 A. NISTAL, M., RODRIGUEZ ECHANDIA, E. L. and PANIAGUA, R. 1978. Septate junctions between digestive vacuoles in human malakoplakia. Tissue & Cell, 10, 137-142. PEARSE, A. G. E. and WELSCH, V. 1968. Ultrastructural characteristic of the thyroid C cells in the summer, autumn and winter states of the hedgehog (Erinaceus europaeus), with some references to other mammalian species. Z. Zdforsch. mikrosk. Anat., 92, 596-609. SAITO, A., SMIGEL, M. and FLEISCHER, S. 1974. Membrane junctions in the inner-membrane space of mitochondria from mammalian tissues. J. Ceff Biol., 60, 653-663. WATANABE, H., BURNSTOCK, G., JARROT, B. and LOUIS, W. T. 1976. Mitochondrial abnormalities in human phaeochromocytoma. CeN Tiss. Res., 172, 281-288.
& CELL
1978 10 (4) 735740
Published by Longman Group Ltd. Printed in Great Britain
MANUEL
NISTAL,
FORMALDEHYDE-INDUCED SEPTATE JUNCTIONS VACUOLES
EDUARDO
L. RODRiGUEZ-ECHANDi-A and RICARDO PANIAGUA
APPEARANCE OF BETWEEN DIGESTIVE
ABSTRACT. Tissue biopsies from (1) some chronic inflammatory diseases, (2) a necrotic tumoral process, (3) normal human lymphatic ganglia, and (4) two congenital diseases of the adrenal cortex were selected for study. A block from each biopsy was fixed in glutaraldehyde-paraformaldehyde; a second block was fixed in 10% formaldehyde. In all cases septate junctions between digestive vacuoles did occur in phagocytic cells and some adrenal cortex cells fixed in formaldehyde. These junctions were similar to those reported recently for malakoplakia phagocytes. Consistently, they were not found to attach organelles other than lysosomes derivatives. Both phagocytes and adrenal cortex cells in the material fixed in glutaraldehyde-paraformaldehyde did not display adhesive specializations between digestive vacuoles. This suggests that the septate junctions described herein are artifactuous structures induced by formaldehyde. There is, however, a certain degree of specificity of cells having the capability of developing these septate junctions. It is assumed that the coating material of digestive organelles in phagocytes and some other cells would be responsible for both cell specificity and organelle specificity of the formaldehyde-induced septate junctions.
tion of cytoplasmic organelles and may be induced by anoxia and other harmful condiSEPTATEjunctions between digestive vacuoles tions (Bulger and Trump, 1968; Saito ef al., have been described recently for phagocytic 1974). Such might also be the case for the ceils in a chronic inflammatory disease septate junctions between digestive vacuoles. referred to as malakoplakia (Nistal et al., These were found in tissue biopsies fixed by 1978). They resemble the septate desmosomes immersion in formaldehyde, and occur often found between cells of invertebrates. together with a variety of fixation artifacts These particular junctions would be involved (Nistal et al., 1978). However, phagocytic in cell-to-cell attachment (Friend and Gilula, cells were the only ones showing digestive 1972), but the evidence connecting them to vacuoles joined by septate junctions. Tissue low-resistance coupling is largely circumfixation may not be the sole reason involved stantial (Hudspeth and Revel, 1971). Intrain the appearance of these peculiar structures mitochondrial and intermitochondrial septate (Nistal et al., 1978). junctions have been reported for certain cells With the aim of determining whether such in mammals (Pearse and Welsch, 1968). junctions (a) are artifactuous or real comHowever, there is some evidence suggesting ponents and (b) if they are peculiar to that they are artifactuous structures. They malakoplakia phagocytes, tissue biopsies coexist, in general, with swelling and distorwere obtained from several tissues containing cells with abundant digestive organelles. It Departamento de Morfologia, Facultad de was found that septate junctions between Medicina, Universidad Autbnoma, C/Arzobispo digestive organelles occur in phagocytes from Morcillo, 4, Madrid-34, Spain. normal and pathological biopsies, as well as Received 22 May 1978. in some other formaldehyde-fixed cells. These Revised 25 June 1978. 735 Introduction
136
NISTAL.
RODRfGUEZ-ECHANDfA
peculiar attachment devices are not apparent in the cells fixed in glutaraldehyde-paraformaldehyde. Materials and Methods Human tissues containing abundant macrophages or other cell types bearing a large complement of digestive organelles were selected for study. Each biopsy or tissue sample was cut into three blocks which were processed as follows : (a) Light microscopy. One block was fixed by immersion in a solution of 10% formaldehyde with 1% ClNa (24 hr), embedded in paraffin and stained with haematoxylin and eosin for routine disease diagnosis. The material was identified with (1) Chronic granulomatous disease (two biopsies from both liver and lymphatic ganglia). (2) Lymphoma (one biopsy from a lymphatic ganglion). (3) Leiomyosarcoma (one biopsy from the small intestine). (4) Normal lymphatic ganglia (three biopsies). (5) Congenital lipoid hyperplasia of the adrenal gland and adrenal cytomegalia (tissue samples obtained from necropsies).
AND
PANIAGUA
(b) Electron microscopy. A second block from each biopsy or necropsy was fixed by immersion in the Karnovsky (1965) mixture of glutaraldehydeparaformaldehyde (4 hr at 3°C). The third block was fixed in a 10% formaldehyde solution (24 hr) with 1% ClNa added, rinsed in cacodylate buffer and immersed in the Karnovsky solution (4 hr) for additional fixation. The material from both groups was postfixed in 1% 0~04, dehydrated in ethanol and embedded in Epon-812. The ultrathin sections were stained with uranyl acetate and lead citrate and studied in a Philips EM 300. Results 1. Glutaraldehyde-paraformaldehyde-fixed material. Good preservation of cell fine structure was observed in the lymphatic ganglia and the intestinal wall biopsies that were processed with the Karnovsky fixative. The same applies to the adrenal tissue samples, though these were obtained several hours after death and showed some distortion due to postmortem phenomena. Abundant digestive bodies were observed in phagocytic cells from normal lymphatic
Fig. 1. Glutaraldehyde-paraformaldehyde-fixed phagocytic cell in a ganglion biopsy from a chronic granulomatous disease showing cluster of digestive vacuoles (D). They are close to one another (arrows) but are not joined by septate junctions. m, mitochondria. x 14,000. Fig. 2. Glutaraldehyde-paraformaldehyde-fixed from lymphoma showing different steps of vacuole are not apparent. x 70,000.
phagocyte in a ganglion biopsy fusion (1, 2, 3). Septate junctions
Fig. 3. Formaldehyde-fixed phagocyte in a lymphatic ganglion chronic granulomatous disease. The digestive organelles appear junctions (arrows). x 35,000.
from a patient with attached by septate
Fig. 4. Formaldehyde-fixed phagocyte in a lymphatic ganglion from a patient with chronic granulomatous disease showing the microfilamentous coat of the digestive organelles (small arrows). It is apparently involved in septate junctions formation (large arrows). x 80,000. Fig. 5. A septate junction between two digestive vacuoles (1, 2) in a formaldehydefixed phagocyte of a lymphatic ganglion biopsy from a chronic granulomatous disease. Periodical septa are seen at the cleft (arrows). x 80,000. Fig. 6. Formaldehyde-fixed phagocyte in a ganglion biopsy from a chronic granulomatous disease showing a cluster of mitochondria. Septate junctions are not apparent between these organelles (arrows). The area enclosed in the rectangle is illustrated at higher magnification by the inset. x 48,000; inset x 85,000.
738
NISTAL,
RODRfGUEZ-ECHANDiA
ganglia, chronic granulomatous disease, lymphoma and leiomyosarcoma. Such organelles are heterogeneous in shape and are comprised of lysosomes, phagolysosomes and cytolysosomes. Though most of these components appeared in close topographical relation to one another, adhesive specializations were not apparent between them (Fig. 1). Instead, direct contracts of the outer aspect of their membrane boundaries or even intermediate images of vacuole fusion were often seen (Fig. 2). Abundant lysosome derivatives were also found in the adrenal cortex cells of zona fasciculata and zona reticularis in tissue samples from congenital lipoid hyperplasia and cytomegalia. As phagocytic cells, the adrenal cells did not display adhesive specializations between the digestive vacuoles.
2. Formaldehyde-fixed material. The electron microscopy analysis of the formaldehydefixed phagocytic cells from the normal lymphatic ganglia as well as from the chronic inflammatory diseases and from the periphery of the leiomyosarcoma reported above, showed clamping of digestive vacuoles, mitochondria and other cytoplasmic organelles. Most digestive vacuoles appeared attached to one another by typical septate junctions (Fig. 3), similar to those reported for malakoplakia phagocytes (Nistal et al., 1978). In addition, nearly all phagocytes displayed lysosomes invested by radial strands of considerable electron density (Fig. 4). Such coating material is apparently involved in the attachment of these organelles to one another (Figs. 3, 5). A cluster of swollen mitochondria in a phagocytic cell fixed in formaldehyde is illustrated in Fig. 6. The cleft between these mitochondria may be as narrow as 100 A. However, septate junctions never occurred between the apposing membranes. These junctions are peculiar to digestive vacuoles. Interestingly, specialized junctions between dense bodies were found neither in the neutrophilic and eosinophilic leucocytes nor in the plasma cells interspersed with the macrophages. As to the formaldehyde-fixed adrenal tissue samples, septate junctions between digestive vacuoles were also found in the adrenal cells of zona fasciculata and zona reticularis. These adhesive devices were
similar to those phagocytes.
AND
reported
PANIAGUA
above
for the
Discussion The occurrence of septate junctions between digestive vacuoles was reported previously for phagocytic cells in human malakoplakia (Nistal et al., 1978). Present findings extend such observations not only to phagocytes in other chronic inflammatory diseases or in the vicinity of a necrotic tumoral tissue (leiomyosarcoma) but also to macrophages in normal lymphatic ganglia. On the other hand, the occurrence of septate junctions between dense bodies in adrenal cortex cells supports the view that such devices are not unique for phagocytes. These septate junctions are similar to the septate desmosomes involved in cell-to-cell attachment (Hudspeth and Revel, 1971; Friend and Gilula, 1972). However, the septate junctions between digestive organelles were peculiar to the preparations fixed in formaldehyde; they did not appear in equivalent cells when they were fixed in glutaraldehyde-paraformaldehyde. Therefore, tissue fixation is undoubtedly involved in the appearance of such structures. When interpreting these results, two possibilities come to mind: (1) The septate junctions may be artifactuous structures induced by formaldehyde or (2) they artifactuously disappear in the cells fixed with glutaraldehyde-paraformaldehyde. The first alternative seems more likely to us. In general, great distortions having no basis in the living cells are not produced by the Karnovsky mixture of glutaraldehyde-paraformaldehyde. The formaldehyde-fixed tissue blocks, but not those fixed in the Karnovsky solution, showed organelle clamping and swelling of mitochondria. These features in other cell types are currently regarded as fixation artifacts. In addition, it has been reported that intramitochondrial and intermitochondrial septate junctions may be induced by several conditions causing tissue damage (Bulger and Trump, 1968; Saito et al., 1974). In the biopsies from the formaldehydefixed lymphatic ganglia and leiomyosarcoma, only phagocytic cells exhibited the septate junctions in question. The oesinophilic and neutrophilic leucocytes, as well as the plasma cells interspersed among them, did not show septate structures between dense bodies.
FORMALDEHYDE-INDUCED
SEPTATE
Their organelles, however, appeared just as clamped and distorted as in the phagocytic cells. This suggests the existence of some degree of especificity of cells having the capability of developing septate junctions when fixed under certain conditions. Certainly, the artifactuous clamping of cytoplasmic components by formaldehyde contributes to formation of septate junctions between digestive organelles but it is not the sole condition involved. Such would also be the case for the septate junctions between mitochondria, described by Watanabe et al. (1976). Another point which deserves to be discussed is the selectivity of these septate junctions for digestive organelles. The fact that these structures were never found between adjacent mitochondria or between mitochondria and digestive vacuoles in the formaldehyde-fixed cells. A reasonable explanation is that such organelles are invested by a material which, when reacting with formaldehyde, may produce septate junc-
JUNCTIONS
739
tions. A coating material having a honeycomb pattern was reported for lysosome derivatives in malakoplakia phagocytes fixed with formaldehyde (Nistal et al., 1978). In the present work, coating microfilaments were detected on the lysosomes. These were found to articulate with similar components investing adjacent lysosomes in a way suggesting intermediate stages in the formation of septate junctions. One tends to speculate, therefore, that in the absence of a peculiar coating material, formaldehyde fails to induce the formation of septate junctions between cytoplasmic organelles. Digestive organelles in phagocytes and other cells (adrenal cortex cells) would be invested by this matter, whereas this would not occur in adjacent cells of different types (leucocytes, plasma cells). The septate junctions described herein might be artifactuous in nature but may well be an expression of important differences between digestive vacuoles in different cell types.
740
NISTAL,
RODRIGUEZ-ECHANDfA
AND
PANIAGUA
BULGER, R. E. and TRUMP, B. F. 1968. Structure of coupled and uncoupled cell junctions. J. Cell Bid., 37, 621-632. FRIEND, D. S. and GILULA, N. B. 1972. Variations in tight and gap junctions in mammalian tissues. J. CeN Bid., 53, 758-776. HUDSPETH, A. J. and REVEL, J. P. 1971. Coexistence of gap and septate junctions in an invertebrate epithelium. J. Cd Bid., 50, 92-101. KARNOVSKY, M. J. 1965. A formaldehyde-glutaraldehyde fixative of high osmolality for use in electron microscopy. J. Cell Bid., 27, 137 A. NISTAL, M., RODRIGUEZ ECHANDIA, E. L. and PANIAGUA, R. 1978. Septate junctions between digestive vacuoles in human malakoplakia. Tissue & Cell, 10, 137-142. PEARSE, A. G. E. and WELSCH, V. 1968. Ultrastructural characteristic of the thyroid C cells in the summer, autumn and winter states of the hedgehog (Erinaceus europaeus), with some references to other mammalian species. Z. Zdforsch. mikrosk. Anat., 92, 596-609. SAITO, A., SMIGEL, M. and FLEISCHER, S. 1974. Membrane junctions in the inner-membrane space of mitochondria from mammalian tissues. J. Ceff Biol., 60, 653-663. WATANABE, H., BURNSTOCK, G., JARROT, B. and LOUIS, W. T. 1976. Mitochondrial abnormalities in human phaeochromocytoma. CeN Tiss. Res., 172, 281-288.