Lysosomal Elements Research Articles

Disruption of the phagosomal membrane and egress of Legionella pneumophila into the cytoplasm during the last stages of intracellular infection of macrophages and Acanthamoeba polyphaga.

Although the early stages of intracellular infection by Legionella pneumophila are well established at the ultrastructural level, a detailed ultrastructural analysis of late stages of intracellular replication has never been done. Here we show that the membrane of the L. pneumophila-containing phagosome (LCP) is intact for up to 8 h postinfection of macrophages and Acanthamoeba polyphaga. At 12 h, 71 and 74% of the LCPs are disrupted within macrophages and A. polyphaga, respectively, while the plasma membrane remains intact. At 18 and 24 h postinfection, cytoplasmic elements such as mitochondria, lysosomes, vesicles, and amorphous material are dispersed among the bacteria and these bacteria are considered cytoplasmic. At 18 h, 77% of infected macrophages and 32% of infected A. polyphaga amoebae harbor cytoplasmic bacteria. At 24 h, 99 and 78% of infected macrophages and amoebae, respectively, contain cytoplasmic bacteria. On the basis of lysosomal acid phosphatase staining of infected macrophages and A. polyphaga, the lysosomal enzyme is present among the bacteria when host vesicles are dispersed among bacteria. Our data indicate that bacterial replication proceeds despite physical disruption of the phagosomal membrane. We also show that an lspG mutant that is defective in the type II secretion system and therefore does not secrete the hydrolytic enzymes metalloprotease, p-nitrophenol phosphorylcholine hydrolase, lipase, phospholipase A, and lysophospholipase A is as efficient as the wild-type strain in disruption of the LCP. Therefore, L. pneumophila disrupts the phagosomal membrane and becomes cytoplasmic at the last stages of infection in both macrophages and A. polyphaga. Lysosomal elements, mitochondria, cytoplasmic vesicles, and amorphous material are all dispersed among the bacteria, after phagosomal disruption, within both human macrophages and A. polyphaga. The disruption of the LCP is independent of the hydrolytic enzymes exported by the type II secretion system.

Polychlorinated biphenyl congener 153-induced ultrastructural alterations in rat liver: A quantitative study

Alterations in the liver of male and female Sprague-Dawley rats fed PCB congener 153 (2,2′,4,4′,5,5′-hexachlorobiphenyl) at 0.5, 5, or 50 ppm concentrations in diets for 13 weeks were determined morphometrically. A dose-dependent increase in hepatocyte volume was detected; the cytoplasmic compartment contributed to the increase in cell volume in an overwhelming fashion. Eighty percent and 250% increase in smooth endoplasmic reticulum volume and its surface area in hepatocytes were estimated in animals of both genders from 5- and 50-ppm groups, respectively; the organelle played the largest part in the increase in cytoplasmic volume. Rough endoplasmic reticulum alteration was shown to depend on gender, where the volume per hepatocyte was augmented by 40% and 45% in females of 5- and 50-ppm groups, respectively, however, 30% and 20% decreases in volume of this organelle were noted in males at those congener concentrations. A decrease of 13% in normal mitochondria volume at 50 ppm concentration was observed, which may have been a consequence of a transformation of these mitochondria to abnormal types. Two types of abnormal mitochondria, named Type I and Type II, were defined: the former comprised mitochondria that had cristae which laying parallel to the long axis of the organelle and the latter showed C- or ring-shaped profiles. Data analysis revealed a trend toward an increase in abnormal mitochondria volume in the cells as the congener concentration elevated. In addition, a threefold increase in the volume of lysosomal elements per hepatocyte was noted in 50 ppm PCB-fed rats of both genders. Also, a significant increase in peroxisome volume per cell in female rats was detected at a lower concentration than it was in the male. This study, which is a first ultrastructural quantitative investigation on the effects of a PCB that included many parameters. The methodology, and the data may prove useful to provide better understanding of pathology in the evaluation and regulation of toxic chemicals.

Alterations of dendritic cells in the rat thymus without epithelial cell loss during cyclosporine treatment and recovery

After cyclosporine treatment, dendritic cells disappear from the rat thymic medulla. The present study was undertaken to examine the ultrastructural alterations in the dendritic cell population during 14-day cyclosporine treatment and subsequent 6-week recovery. Four dendritic cell subtypes were defined ultrastructurally by a newly developed classification system. In addition, the potential effect of cyclosporine on six medullary epithelial cell subtypes was studied. During cyclosporine treatment, a prominent reduction of dendritic cells was seen at the ultrastructural level, whereas the total number of medullary epithelial cells remained largely unchanged. These findings were confirmed by immunohistochemistry. The number of mature dendritic cells declined later than the number of immature ones. A decrease in the antigen-processing capacity of remaining dendritic cells was suggested by the disappearance of Birbeck granules and the reduced number of tubulovesicular complexes. These findings support a disturbance of clonal deletion during cyclosporine treatment. The dendritic cell alterations appeared reversible 4 weeks after the restoration of the original architecture. During recovery, dendritic cells displaying lysosomal elements outnumbered those found in the normal uninvoluted thymus. This phenomenon probably reflects an enhanced turnover of cell organelles. No treatment-related effect on epithelial cell subtypes was seen.

Cytological and biochemical response of R1 cells and isolated hepatocytes from rainbow trout ( Oncorhynchus mykiss) to subacute in vitro exposure to disulfoton

Ultrastructural, stereological and biochemical alterations in isolated hepatocytes and the permanent fibrocyte-like cell line R1 from rainbow trout (Oncorhynchus mykiss) exposed to 0, 0.2, 2 and 20 mg/l of the phosphorodithioate pesticide disulfoton (Solvirex, O,O-diethyl S-2-ethylthioethyl phosphorodithioate) for up to 5 days were investigated. In both R1 cells and isolated hepatocytes, distinct dose- and time-dependent morphological alterations including diminished amounts of heterochromatin, proliferation of lysosomal elements, dilation and vesiculation of endoplasmic reticulum cisternae, induction of concentric membrane whorls and an increased amount of lipid droplets could be detected at concentrations of > or = 2 mg/l (R1 cells) and > or = 0.2 mg/l disulfoton (hepatocytes). Additional effects in isolated hepatocytes comprised marginalization of heterochromatin, myelin-like structures attached to mitochondrial membranes, formation of ring-shaped mitochondria, proliferation of smooth endoplasmic reticulum, reduction of rough endoplasmic reticulum, induction of ring-shaped Golgi cisternae, glycogen depletion and occurrence of glycogenosomes. Structural changes in isolated hepatocytes could be correlated to suppression of lactate dehydrogenase, glucose-6-phosphate dehydrogenase, alanine aminotransferase, malic enzyme, esterase as well as glutathione S-transferase, but to a stimulation of 7-ethoxycoumarin-O-deethylase and the rate of lipid peroxidation at concentrations > or = 0.01 mg/l disulfoton. Comparison with data from in vivo experiments with rainbow trout indicate the suitability of in vitro techniques for the evaluation of the toxicological potential of a wide range of ecotoxicologically relevant substances.

Cytopathology of liver and kidney in rainbow trout Oncorhynchus mykiss after long-term exposure to sublethal concentrations of linuron

DAO Diseases of Aquatic Organisms Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials DAO 21:35-52 (1995) - doi:10.3354/dao021035 Cytopathology of liver and kidney in rainbow trout Oncorhynchus mykiss after long-term exposure to sublethal concentrations of linuron Oulmi Y, Negele R-D, Braunbeck T ABSTRACT: Hepatic and renal cytopathological alterations in fingerling rainbow trout Oncorhynchus mykiss following 5 wk exposure to 30, 120, and 240 ug l^(-1) linuron [3(3,4-dichlorophenyl)-1-methoxy-1-methylurea] were studied by electron microscopy. Ultrastructural alterations were detected in liver and kidney at >=30 ug l^(-1), 2 orders of magnitude below conventional LC_(0). The response suggested a dose-response relationship with a change from adaptive to degenerative features at 120 ug l^(-1). Hepatocyte changes included: stimulation of mitosis; segmentation of nuclei; partial reorganization of heterochromatin; multiplication of nucleoli; fractionation, vesiculation and transformation of rough endoplasmic reticulum (RER) into myelinated bodies; induction of smooth endoplasmic reticulum; moderate steatosis; apparent proliferation of mitochondria, peroxisomes, Golgi fields and lysosomal elements; depletion of glycogen; perisinusoidal lipid accumulation; elevated rate of hepatocytes in various stages of necrosis; infiltration and increased phagocytic activity of macrophages. Reactions of renal tubular cells were differentiated in different nephron segments. Major alterations by site in kidney were (1) renal corpuscle: lobulation of podocyte nuclei; (2) proximal segment I: elevated heterogeneity of all cell components, increased heterochromatin and nuclear size, rearrangement of RER, proliferation of Golgi fields, novel lysosomal elements, decreased mitochondria and lysosomes at 240 ug l^(-1); (3) proximal segment II: nuclear lobulation, binucleated cells, proliferation of lysosomes and peroxisomes (lower concentrations), decreased peroxisomes and mitochondria (240 ug l^(-1)), crystalline inclusions in lysosomal matrix, fragmentation, degranulation and circular arrangement of RER; (4) distal segment: induction of giant mitochondria with longitudinal crystalline inclusions, atypical lysosomes with long crystalline matrix inclusions, and augmentation of various lysosomal elements. Comparison of linuron-induced cellular alterations with cytopathological effects by potential linuron breakdown products, namely 4-chloroaniline and 3,4-dichloroaniline, revealed a high degree of similarity of cytopathological phenomena, indicating that part of the changes observed after linuron exposure might well be due to the action of linuron metabolites. KEY WORDS: Rainbow trout . Liver . Kidney . Ultrastructure . Linuron . 4-Chloroaniline . 3,4-Dichloroaniline . Cytopathology Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in DAO Vol. 21, No. 1. Publication date: February 02, 1995 Print ISSN:0177-5103; Online ISSN:1616-1580 Copyright © 1995 Inter-Research.

The origin and composition of peroxidase-positive granules in cysteamine-treated astrocytes in culture

Gomori astrocytes, which are prominent in periventricular regions of the brain, contain inclusions that stain with Gomori dyes, and exhibit an orange-red autofluorescence and a non-enzymatic peroxidase activity. Recently, such astrocytes have been induced in dispersed glial cultures by exposure to cysteamine. Using these cells, we have shown that the peroxidase-positive inclusions (Gomori bodies) are multicompartmental, that iron co-localizes with the peroxidase activity, and that the iron is often segregated in one of the compartments of the body. The goal of the present study was to determine the origin and process of formation of these bodies. The results indicate that cysteamine induces aberrations in mitochondrial structure associated with the acquisition of iron and the associated peroxidase activity. Mitochondria thus transformed appear to initiate an autophagic process in which they, and adjacent structures, are sequestered. The presence of acid phosphatase activity in a number of mature Gomori bodies attests to the participation of lysosomal elements in this process. These results indicate, therefore, that the Gomori body is a complex autophagosome in which the iron-containing compartments, putatively responsible for the peroxidase activity, represent undegraded transformed mitochondria.

Histochemical demonstration of acid phosphatase activity in terminal Schwann cells associated with Ruffini endings in the periodontal ligament of rat incisors

Histochemical staining for acid phosphatase, a marker for lysosomal elements, distinguished rounded, intensely reactive cells from less reactive fibroblasts and osteoblasts in the lingual periodontal ligament. The highly reactive cells were located exclusively in the alveolar half of the ligament. Double staining for acid phosphatase and S-100 protein confirmed that these reactive cells were identical with the terminal Schwann cells associated with periodontal Ruffini endings. Electron microscopically, reaction products for acid phosphatase were observed in the lysosomes and Golgi apparatus in the paranuclear cytoplasm of the terminal Schwann cells. As the terminal Schwann cells associated with the Ruffini endings are assumed to be capable of synthesizing exportable proteins, acid phosphatase in this type of cell may be involved in the processing of macromolecules in synthetic and/or secretory pathways.

Effects of inorganic ions on autophagy in hepatocytes.

The effects of inorganic phosphate and divalent cations, Ca2+ and Mg2+, on autophagy were morphologically studied using perfused livers. High concentrations of phosphates in perfusate caused an increased number of macroautophagic vacuoles and translocation of lysosomes around a nucleus, like a glucagon solution. On the other hand, the depletion of phosphate in a glucagon solution showed no effect on the lysosomal elements or showed decreased numbers of microautophagic vacuoles. A divalent cation-free solution caused a similar decrease in the microautophagic vacuoles. There was a significant difference in the number of the macroor microautophagic vacuoles between either the high phosphate or the glucagon solution and either the phosphate-free or the divalent cation-free solution. The use of those inorganic ions in autopahgy was suggested. It has been proposed that inorganic phosphates along with Ca2+ are used for membrane fusion. The present study shows an increased number of autophagosomes in the high phosphate solution and high incidence of the autophagosomes in the phosphate-free or the divalent cation-free solution. Thus, these inoganic ions may be connected with the formation of autophagosomes and in the fusion of them with lysosomes.

The latent membrane protein-1 in Epstein-Barr virus-transformed lymphoblastoid cells is found with ubiquitin-protein conjugates and heat-shock protein 70 in lysosomes oriented around the microtubule organizing centre.

Immunofluorescence studies on Epstein-Barr virus (EBV)-transformed lymphoblastoid cells have previously shown that the latent membrane transforming protein (LMP-1) is found in patch-like inclusions which also immunostain for vimentin. We now show that EBV transformation causes a major reorganization of intermediate filaments, microtubules, mitochondria, and lysosomal elements, which generally become oriented around the microtubule organizing centre. Immunogold electron microscopy shows that LMP-1 is primarily concentrated in secondary lysosomes together with ubiquitin-protein conjugates and heat-shock protein 70. Intermediate filament inclusion formation with the above characteristics may be a general response triggered by other membrane glycoproteins; as seen, for example, in major human neurodegenerative diseases such as diffuse Lewy body disease.

Changes with senescence in the fine structure of the granular convoluted tubule of the submandibular gland of the mouse.

Cells of the granular convoluted tubules (GCTs) of the submandibular gland of senescent male mice show structural changes indicative of functional decline. In order to define the nature of these age-related changes more clearly, the fine structure of GCT cells of 12- and 28-month-old males was compared. In old mice, there was cell-to-cell variation in the extent of these changes, with some cells of senescent males appearing no different from those of young adults. In affected cells the most striking alterations were seen in secretion granules and lysosomal elements. Secretion granules varied greatly in size, with some GCT cells having only very fine apical granules. Secondary lysosomes and large lipofuscin granules were frequent in the basal cytoplasm. Very large dense bodies (3-5 micron) occurred in many cells. These possibly represent intracellular pools of released secretory materials, as they were occasionally seen in continuity with the luminal contents. Structures whose appearance was intermediate between the very large dense bodies and lipofuscin granules were common, suggesting crinophagic activity. There was an apparent decrease in numbers of polysomes and in the extent of the Golgi apparatus. These fine structural changes are consistent with impairments with advanced age in synthesis and posttranslational processing of secretory products by affected GCT cells. In addition to cell-to-cell variation in any one male, there was also interanimal variation in the degree and extent of these senescent changes.

Application of high-resolution immunocytochemistry to the study of the secretory, resorptive, and degradative functions of ameloblasts.

The distribution of enamel proteins (EP) within extracellular and subcellular compartments of the enamel organ has been characterized by use of the protein A-gold immunocytochemical technique and an antibody against mouse amelogenins. EP were immunolocalized within the protein synthetic and secretory organelles, and within lysosomal elements of ameloblasts in both the secretion and maturation stages. The results provide direct evidence that ameloblasts maintain active secretory and degradative pathways for EP throughout the secretory and early maturation stages of amelogenesis. The origin of the immunoreactive material within lysosomes is unclear and could derive from the direct shunting of newly formed EP from the synthetic organelles to the lysosomes or from endocytosis of aged proteins. These findings ultimately provide new insights into the multifunctional role which ameloblasts play throughout amelogenesis.

Cytochemical identification of lysosomal system of the rat junctional epithelium.

Structures taking part in the lysosomal system of rat junctional epithelium (JE) were evaluated by means of ultrastructural enzyme cytochemistry. Acid phosphatase (AcPase) and trimetaphosphatase (TMPase), both the representative lysosomal marker enzymes, were frequently detected in dense bodies which contained the homogeneous matrix and showed pleomorphic appearance. These activities were also often localized to the phagosomes with heterogeneous contents, the reaction of TMPase being much more intense than that of AcPase. Cisternal structures, most probably corresponding to GERL, also displayed AcPase activity and exhibited the close morphologic relationships with lysosomal structures. On the other hand, the localization of thiamine pyrophosphatase activity was almost limited to the innermost cisterna of the Golgi complex. Neither AcPase nor TMPase activity could be detected in the cytoplasmic vacuoles, which were characteristically numerous in rat JE and the multivesicular bodies.From the present findings, it is suggested that the lysosomal system in rat JE is composed of dense bodies (primary lysosomes), phagolysosomes (secondary lysosomes), and GERL and that some of those lysosomes are apparently derived from GERL. Different localization patterns of marker enzymes examined might reflect the enzymatic heterogeneity of various lysosomal elements.

Formation of a Morphologically Complex System by Peroxidase-Positive Lysosomal Elements in Human Monocytes

AbstractComputer-aided three-dimensional reconstruction of serial ultrathin sections revealed that freshly prepared monocytes from human blood contained endogenous peroxidase (PO) not only in cytoplasmic granules, but also in long contorted tubules and in complex elements, which consisted of both tubular and granular components. The various PO-positive elements formed an intricate system, which was separate from all other cytoplasmic structures, including the endoplasmic reticulum and the Golgi apparatus. Because the PO-positive elements in monocytes are known to be primary lysosomes, which are involved in host defense mechanisms, we suggest that the antimicrobial functions of human blood monocytes are exerted by functionally and morphologically diverse subcompartments of a complex system rather than by separate uniform granules. © 1985 by Grune & Stratton, Inc.

Formation of a morphologically complex system by peroxidase-positive lysosomal elements in human monocytes

Computer-aided three-dimensional reconstruction of serial ultrathin sections revealed that freshly prepared monocytes from human blood contained endogenous peroxidase (PO) not only in cytoplasmic granules, but also in long contorted tubules and in complex elements, which consisted of both tubular and granular components. The various PO- positive elements formed an intricate system, which was separate from all other cytoplasmic structures, including the endoplasmic reticulum and the Golgi apparatus. Because the PO-positive elements in monocytes are known to be primary lysosomes, which are involved in host defense mechanisms, we suggest that the antimicrobial functions of human blood monocytes are exerted by functionally and morphologically diverse subcompartments of a complex system rather than by separate uniform granules.

Endocytosis in nonciliated epithelial cells of the ductuli efferentes in the rat.

The nonciliated cells lining the ductuli efferentes presented three distinct cytoplasmic regions. The apical region contained, in addition to cisternae of endoplasmic reticulum and mitochondria, two distinct membranous elements. The tubulovesicular system consisted of dilated tubules connected to the apical plasma membrane and subjacent distended vesicular profiles. The apical tubules, not connected to the cell surface, consisted of numerous densely stained tubules of small size which contain a compact, finely granulated material. The supranuclear region, in addition to a Golgi apparatus and ER cisternae, contained dilated vacuoles, pale and dense multivesicular bodies, as well as numerous dense granules identified cytochemically as lysosomes. The basal region contained the nucleus and many lipid droplets. The endocytic activity of these cells was investigated using cationic ferritin (CF) and concanavalin-A-ferritin (Con-A-ferritin) as markers of adsorptive endocytosis; and native ferritin (NF), concanavalin-A-ferritin in the presence of alpha-methyl mannoside, and horseradish peroxidase or albumin bound to colloidal gold for demonstrating fluid-phase endocytosis. These tracers were injected separately into the rete testis, and animals were sacrificed at various time intervals after injection. At 1 min, CF or Con-A-ferritin were seen bound to the apical plasma membrane, to the membrane of microvilli, and to the membrane delimiting elements of the tubulovesicular system. Between 2 and 5 min, these tracers accumulated in the densely stained apical tubules and at 15 min in the dilated vacuoles. Between 30 min and 1 hr, the tracers appeared in multivesicular bodies of progressively increasing density, whereas at 2 hr and later time intervals, many dense lysosomal elements became labeled. The tracers for fluid-phase endocytosis showed a distribution similar to that for CF or Con-A-ferritin except that they did not bind to the apical plasma membrane, microvilli, or membrane delimiting the tubulovesicular system. At no time interval were any of the tracers observed in the abluminal spaces. Thus, the nonciliated epithelial cells of the ductuli efferentes are actively involved in fluid-phase and adsorptive endocytosis, both of which result in the sequestration of endocytosed material within the lysosomal apparatus of the cell.

Endocytosis and the lysosomal apparatus of rat Leydig cells

The Leydig cells of the rat testis which are involved in testosterone production contain an abundance of smooth endoplasmic reticulum and mitochondria (Figs. 2,6). These cells also possess many peroxisomes, lysosomes and multivesicular bodies (MVB's). On the cell surface, the plasma membrane contains numerous short microvilli, small invaginations and large plasmalemmal folds which appear to engulf extracellular fluid. There are also many large dilated vacuoles adjacent to the cell surface. The purpose of the present study is to determine if these cells show endocytic activity and to differentiate by various cytochemical means lysosomal elements from peroxisomes.To identify lysosomes, tissue chopper sections of 2% glutaraldehyde-fixed testes (containing 2.5% dextran) were incubated in media containing thiamine monophosphate as a substrate (Lalli, 1983) to demonstrate the presence of acid phosphatase or in media containing P-nitrocatechol sulfate for the demonstration of arylsulfatase (Hopsu-Havu et al., 1967).

Collagen biogenesis and assembly into fibrils as shown by ultrastructural and 3H-proline radioautographic studies on the fibroblasts of the rat food pad.

To examine whether collagen is assembled into fibrils within or outside fibroblasts, the connective tissue of the rat foot pad was investigated by electron microscopy and by radioautography at times varying from 4 min to 3 days after an intravenous injection of 3H-proline. The fibroblasts of the rat food pad are long polarized cells with the nucleus at one end, the Golgi apparatus in the center, and a region with long processes at the other end. This region contains secretory granules and is considered to be the secretory pole of the cell. In the Golgi apparatus the stacks of saccules are separated from rough endoplasmic reticulum (rER) by groups of "intermediate vesicles" including similarly structured tubules which may be over 300 nm long and are referred to as "intermediate tubules." The Golgi saccules exhibit distended portions which differ at the various levels of the stack. On the cis side, the distentions tend to be spherical and contain fine looping threads; in the middle of the stack, they are cylindrical and present distinct straight threads; whereas on the trans side, they are again cylindrical, but the straight threads are grouped in parallel aggregates. Between these cylindrical distentions and the secretory granules, there are transitional forms within which thread aggregates are packaged more and more tightly. Finally, the fibroblasts are associated with two types of collagen fibrils: extracellular ones arranged into large groups between the cells and intracellular ones located within long intracytoplasmic channels. Quantitative radioautography after 3H-proline injection reveals that the number of silver grains per unit area reaches a peak over the rER at 4-10 min, Golgi apparatus at 40 min, secretory granules at 60 min, and extracellular collagen fibrils at 3 h. At no time are intracellular collagen fibrils labeled. Qualitative observations further indicate that spherical Golgi distentions are mainly labeled at 40 min, and cylindrical distentions, at 60 min. In addition, from 20 min to 3 hr, some lysosomal elements are labeled. The biogenetic pathway leading to the formation of collagen fibrils is interpreted as follows.(ABSTRACT TRUNCATED AT 400 WORDS)

Dynamics of lysosomal elements in pulmonary alveolar macrophages: II. Transitory intracytoplasmic events in activated cells

AbstractIntracytoplasmic interactions were examined in iron oxideexposed and ‐unexposed alveolar macrophages of mice by electron microscopy and ultrastructural cytochemistry. Submicronic‐sized particles are taken up by microendocytosis into 800‐Å tubules that sometimes open up into a large vacuole located midway between the plasmalemma and the Golgi complex and sometimes lead directly to that organelle, which is reactive for acid phosphatase while cells are only modestly engaged in lysosomal synthesis and then serves as the main locus for formation of heterolysosomes. In more activated cells, nascent lumbricoid lysosomes are budded directly off branches of the granular reticulum; in consequence, much of the newly synthesized acid phosphatase bypasses the Golgi apparatus, and heterolysosomes are formed throughout a widened expanse of cytoplasm. The lumbricoids exist either as free elements or as a labyrinthian network of lumbricoid units, and the two forms appear interconvertible. They are short lived in contrast to larger rounded lysosomes more commonly present, many of which are heterolysosomes as judged by their content of ingested particles. Lumbricoids readily fuse with exoplasmic structures; indeed, in some lumbricoid‐producing cells terminal segments of the reticulum may share this propetry to a degree, since they resemble transitional elements when extended along large phagosomes. Microendosomes can be taken up into lumbriciods, but if the endosome is larger, lumbricoids will adhere to its surface and become part of the digestive vacuole. A labyrinth is formed to envelop large phagosomes or regions of cytoplasm marked for autophagy. The interior is invaded by branches and digestion ensues. In active macrophages the Golgi apparatus is enlarged. The centrioles organize an array of microtubules about themselves, and individual Golgi stacks are turned outward to give the organelle better access to phagosomes and lysosomes. In less active cells the microtubules disappear, and the stacks reform in a circle about the diplosome. Alveolar macrophages therefore make a variety of lysosomes. Depending on cellular activity, one kind or another predominates. Few of them fall cleanly into “primary” and “secondary” classes, and in their interactions with other cellular structures they are influenced by mechanisms operating on microscopic as well as molecular scales.

Ultrastructure of the thyroid glands of rats FED photomirex: An 18-month recovery study

The thyroid glands, from rats which had received photomirex (0.05, 0.5, 4 or 500 ppm) or mirex (5 or 50 ppm) in their diets for 28 days and maintained for 18 months on clean diet, were examined by electron microscopy. A dose of 0.05–5 ppm photomirex resulted in an augmentation of principal follicular cell heights. Their cytoplasm exhibited a marked numerical increase of secondary lysosomes. In additionm, at 5 ppm, follicular cells in some segments of the gland contained only a few secondary lysosomes. After dietary exposure to 50 ppm photomirex the number of lysosomal elements remained elevated in epithelial cell cytoplasm. Morphological aberrations in the follicles could not be detected after the 5 ppm mirex treatment. The most remarkable alterations in this experiment occurred in the thyroid glands of animals ingesting 50 ppm mirex where columnar follicular cells were engorged with deformed lysosomal bodies. Remaining components of the follicular cell architecture in all the treated groups were unaffected and were similar to those in the control group. These results demonstrated that following a 28-day dietary exposure of rats to photomirex (0.05–50 ppm) or mirex (50 ppm), alterations in the thyroid glands persisted for at least 18 months.

Vesicular transport of cationized ferritin by the epithelium of the rat choroid plexus.

We have studied the transport of ferritin that was internalized by coated micropinocytic vesicles at the apical surface of the choroid plexus epithelium in situ. After ventriculocisternal perfusion of native ferritin (NF) or cationized ferritin (CF), three routes followed by the tracers are revealed: (a) to lysosomes, (b) to cisternal compartments, and (c) to the basolateral cell surface. (a) NF is micropinocytosed to a very limited degree and appears in a few lysosomal elements whereas CF is taken up in large amounts and can be followed, via endocytic vacuoles and light multivesicular bodies, to dark multivesicular bodies and dense bodies. (b) Occasionally, CF particles are found in cisterns that may represent GERL or trans-Golgi elements, whereas stacked Golgi cisterns never contain CF. (c) Transepithelial vesicular transport of CF is distinctly revealed. The intercellular spaces of the epithelium, below the apical tight junctions, contain numerous clusters of CF particles, often associated with surface-connected, coated vesicles. Vesicles in the process of exocytosis of CF are also present at the basal epithelial surface, whereas connective tissue elements below the epithelium are unlabeled. Our conclusion is that fluid and solutes removed from the cerebrospinal fluid by endocytosis either become sequestered in the lysosomal apparatus of the choroidal epithelium or are transported to the basolateral surface. However, our results do not indicate any significant recycling via Golgi complexes of internalized apical cell membrane.