Well-developed Golgi Apparatus Research Articles

Abortive secretion of an enamel matrix in the inner enamel epithelial cells during an enameloid formation in the gar-pike, Lepisosteus oculatus (Holostei, Actinopterygii).

The tooth in the gar-pike, Lepisosteus oculatus, an actinopterygian fish, is characterized by the occurrence of both enamel and enameloid, the former covering the tooth shaft and the latter, the tooth cap. Our previous research demonstrated that the enamel in this species was, as in the lungfish, immunoreactive for amelogenin, indicating its homologous nature with the mammalian tooth enamel, whereas the enameloid was completely immunonegative. The present study demonstrates that, during the early maturation stage of the enameloid formation, the inner enamel epithelial cells (IEECs) synthesize through a well-developed Golgi apparatus a fine-granular substance which is intensely immunoreactive for amelogenin. This substance was accumulated in a large saccule extended in a suprabasal zone of the cell; we were unable to find any morphological sign indicating a connection of the substance with the enameloid matrix. The abortive secretion of the enamel matrix-like substance in the IEEC during an enameloid formation was considered to be an instance of rudimental enamel formation. In the gar-pike, the synthesis of amelogenin in the IEEC has been demonstrated to occur independently from that of the enameloid matrix. The present findings demonstrate a prominent difference between the tooth enamel and enameloid.

S1.1 Etiopatogenia del liquen plano oral

The peltate trichomes of Bromeliaceae comprise an important feature of this plant group. Although recognized for their capacity for water and nutrient absorption, little is known concerning their secretory functions. This study aimed to identify and describe the structures observed to secrete mucilage in the inflorescences of Aechmea blanchetiana, a species of Bromeliaceae endemic to Brazil. Samples of different portions and developmental stages of inflorescences were collected and processed for study under light and electron microscopy. Mucilage is secreted by peltate trichomes covering the inflorescence axis, which have a structure typical of bromeliad scales, although often having an irregular shield commonly exhibiting a stellate outline. Secretion is performed by cells comprising the so-called wing portion of the trichome and begins even in initial stages of inflorescence expansion. In expanded portions, secretory activity ceases and the remaining secretion appears as a thin dehydrated film covering the inflorescence surface. Ultrastructural data show the presence of well-developed Golgi apparatus and endoplasmic reticulum, confirming a secretory function related to non-cellulosic polysaccharide production. We believe that the mucilage is related to protection against desiccation, especially at early stages of expansion. Such a functional role, in association with the nature and dynamics of the secretion, suggests that these structures act as colleters. As far as we know, this is the first record for exogenous secretory activity by the typical peltate trichomes of Bromeliaceae, and the first time when colleter-like functions have been considered and discussed in this family.

Somatostatin-IR neurons are a major subpopulation of the cuneothalamic neurons in the rat cuneate nucleus.

This study was aimed to localize and characterize the somatostatin-immunoreactive (SOM-IR) neurons in the rat cuneate nucleus (CN). By immuno-histochemistry, the SOM-IR neurons, which were widely distributed in the nucleus, were round, spindle or multiangular in shape (mean area = 226.1 +/ -3.1 microm(2), n = 1016). By electron microscopy, the neurons shared all the ultrastructural features of the cuneothalamic neurons (CTNs) which showed a slightly indented nucleus and a fairly rich cytoplasm containing well-developed Golgi apparatuses and rough endoplasmic reticulum (rER). The SOM immunoreaction product filled the cytoplasm of the neurons extending from the soma to the proximal and distal dendrites, which were postsynaptic to unlabeled boutons. In addition to soma and dendrites, SOM-IR boutons were also identified which made axodendritic synaptic contacts with SOM-IR dendrites. The SOM-IR neurons were characterized by using anti-SOM pre-embedding immunolabeling coupled with horseradish peroxidase (HRP) retrograde method, or SOM immunolabeling along with anti-glutamate, gamma-aminobutyric acid (GABA) or glycine post-embedding immunolabeling for identification of CTNs, glutamate-IR, GABA-IR and glycine-IR neurons, respectively. It was shown that more then 80% of the CTNs contained SOM and, furthermore, they contained glutamate but not GABA or glycine. On the basis of present findings, it is suggested the majority of the SOM-IR neurons in the rat CN are CTNs and that they may be involved in modulation of somatosensory synaptic transmission.

Conjugation of maturation-related wheat-germ-lectin-binding proteins to caput epididymal sperm in co-cultures with corpus epididymal epithelial cells of BALB/c mouse.

In BALB/c mice, two maturation-related wheat-germ-binding glycoproteins (GP-49 and GP-83) are synthesized and secreted by corpus and cauda epididymis. A co-culture technique was used to investigate these glycoproteins in principal cells of corpus epididymis and the conjugation of these molecules on caput sperm. The principal cells were recovered from corpus epididymides of 4-week-old mice and cultured in RPMI 1640 medium supplemented with 10% fetal calf serum. After culturing for 3-4 days, most cells revealed epithelial cell-specific keratins in immunofluorescent localization with monoclonal antibody. By electron microscopy, a prominent nucleolus with well-extended euchromatin was revealed in the nucleus and the cytoplasm contained multivesicular bodies, and a well-developed Golgi apparatus with endoplasmic reticulum. By SDS-PAGE, GP-83 and GP-49 were revealed in the cell extracts and cell culture supernatants after incubation with 35S-methionine. Radiolabeled binding sites were also found on the surface of caput sperm co-cultured with the principal cells for 4 h in the presence of 35S-methionine. WGA-binding glycoproteins may be synthesized and secreted by the principal cells of corpus epididymis and conjugated to caput sperm during the epididymal transit.

Ultrastructural features of medullary chromaffin cell cultures

The ultrastructural organization on the fourth day of culture of chromaffin cells isolated from the bovine adrenal medulla was characterized based on electron microscopic and morphological analysis. We established that medullary chromaffin cells could be divided into four morphologically different subtypes. Most cells (49.1% of those examined) had a dense cytoplasm and fine dense granules. Cells with dense cytoplasm and large granules represented a second type of chromaffin cell (21.1%). Cells of the third type had a light cytoplasm, granules with a light halo and a well-developed Golgi apparatus (26.3%). The fourth type of chromaffin cell was characterized by moderately dense cytoplasm with well-expressed varicose rough endoplasmic reticulum (about 3.5%). Among concomitant cell types, cortical adrenal cells from the zona fasciculata and zona glomerulosa, epithelial cells, fibroblasts, lymphocytes, brown lipoblasts and glial Schwann cells were present. Morphological analysis implies that cells with dense cytoplasm and fine granules and those with light cytoplasm and haloed granules (75.4% in total) are adrenaline-containing cells, whereas the cells with dense cytoplasm and large granules (26.3%) contain noradrenaline. Cells with moderately dense cytoplasm and varicose reticulum share common morphological properties with classical glandular cells and, by their properties, were closer to noradrenaline-containing cells. It is concluded that chromaffin cells, which are the main cell type among cultured cells from adult bovine adrenal medulla, are morphologically quite heterogeneous. Other cell types of different nature may also be present in the culture and can locally influence the properties of the investigated medullary chromaffin cells used in electrophysiological experiments.

Appearance of peculiar vessels with immunohistological features of high endothelial venules in the dermis of moxibustion-stimulated rat skin.

Morphological changes of the dermal blood vessels ofmoxibustion-stimulated rat skin were examined with reference to the lymphocyte migration. After long-term stimulation with direct moxibustion to the acupoint tsu-san-li (St-36), peculiar vessels that possess immunohistological features of high endothelial venules could be observed in the moxa-stimulated acupoint dermis. Endothelial cells of the vessels had well-developed Golgi apparatus in their plump cytoplasms, and they strongly expressed intercellular adhesion molecule-1 on the luminal surface. These data suggest that the appearance of the peculiar vessels in the dermis acts toward the active infiltration of blood-lymphocytes into the acupoint skin.

Ultrastructural and Immunohistochemical Changes of Rat Brain after Long-Term Marijuana Inhalation.

Ultrastructural changes of the brain of rats that inhaled marijuana cigarettes for 8 weeks were examined by electron microscopy, simultaneously with immunohistochemical investigation for serotonergic neuronal activities in the nucleus accumbens (NAc), the hippocampus (CA-1) and the nucleus raphe dorsalis (NRD). In the animals that inhaled marijuana, numerous cored and coated vesicles were observed near the well-developed Golgi apparatus of the NRD neurons. The lamellar membranous structure was found frequently in the dendrite, and occasionally in the axon, and the synapse of the marijuana-smoking animals. The serotonin-immunostainability in neurons of the NRD was significantly stronger in the animals that inhaled marijuana than in the non-treated ones. The serotonin-immunostainability in nerve fibers and terminals of the NAc and the CA-1 showed an obvious decrease compared with that of the non-treated animals. These findings suggest that the neurons in the NRD that is the original nucleus of the serotonergic nerve system have become functionally hyperactive by Δ9-tetrahydrocannabinol, but it may induce the dysfunction of serotonin transmission from the original nucleus.

Fine structure of dental epithelial cells and the enameloid during the enameloid formation stages in an elasmobranch, Heterodontus japonicus.

The structural features of the dental epithelial cells and the enameloid in tooth germs of the Japanese Port Jackson shark, Heterodontus japonicus, in the stages of enameloid formation, were investigated by light and transmission electron microscopy. At the enameloid matrix-formation stage, tall columnar inner dental epithelial cells contained large numbers of glycogen particles. At the enameloid mineralization stage, when many sharply outlined crystals appeared throughout the enameloid, the inner dental epithelial cells exhibited well-developed Golgi apparatuses and many mitochondria in the proximal cytoplasm, and abundant vesicles and vacuoles in the distal cytoplasm. Marked interdigitations of the lateral membrane were visible in the inner dental epithelial cells. The outer dental epithelial cells contained many mitochondria, lysosomal bodies, vesicles and microtubules, and the capillaries usually approached the outer dental epithelial cells. At the enameloid maturation stage, large numbers of crystals occupied the enameloid, and most of the organic matrix had disappeared from the enameloid area after demineralization. The organelles in the inner and outer dental epithelial cells decreased in number, but there were still widely distributed Golgi apparatuses, abundant intermediate filaments and granules containing an electron-dense substance in the inner dental epithelial cells. It is probable that the dental epithelial cells are involved in the removal of organic matrix from the enameloid and in the process of mineralization at the later stages of enameloid formation, i.e., the mineralization and the maturation stages.

Contribution of O4+ oligodendrocyte precursors and astrocytes to the glial ensheathment of vessels in the rabbit myelinated streak.

The barrier properties and glial ensheathment of blood vessels in the retinal myelinated streak of adult New Zealand White rabbits were characterized at the ultrastructural level by intravascular injection of horseradish peroxidase (HRP) and immuno-electron microscopy with monoclonal antibody O4 and antibodies to glial fibrillary acidic protein (GFAP). Vessels within the myelinated streak did not leak HRP, and they exhibited tight junctions between adjacent endothelial cells. However, unlike their adult counterparts, the retinal blood vessels at postnatal day 18 exhibited substantial endocytotic activity. Both GFAP+ astrocytes and O4+ cells were evident surrounding the preretinal blood vessels of the myelinated streak. Furthermore, O4+ cells exhibited features indicative of high synthetic activity, including a large proportion of extended chromatin and prominent nucleoli within the nucleus, as well as a well-developed Golgi apparatus and numerous mitochondria in the cytoplasm. O4+ cells also exhibited variable quantities of heterochromatin, indicative of early stages of cellular differentiation. These observations are consistent with previous data showing that O4+ cells in the myelinated streak include oligodendrocyte precursor cells, pre-oligodendrocytes, and immature oligodendrocytes (Morcos Y, Chan-Ling T. Glia 21:163-182, 1997). The present data indicate that the preretinal vessels of the myelinated streak possess barrier properties typical of microvasculature in the central nervous system, and that both O4+ cells and astrocytes contribute to the glial ensheathment of these vessels. These vessels thus differ markedly from the leaky preretinal vessels associated with pathological conditions such as retinopathy of prematurity.

Structural identification and characterization of arteries and veins in the placental stem villi.

The vascular wall structure in the human full-term placental villi of normal pregnancy was studied by means of light and electron microscopy with an improved technique of perfusion fixation and tissue preparation. We observed 81 sections of stem villi that showed cross-sectional profiles of paired vessels in their center. Both vascular walls contained a large amount of extracellular matrix and no elastic lamina between smooth muscle cells of the media, making identification of the artery and the vein quite difficult at first sight. We then noted that the density of the smooth muscle cell population was always considerably higher in one than the other, and identified the former as artery and the latter as vein on the basis of their connection with larger arteries and veins running on the chorionic plate. Between the paired vessels, the artery had a smaller caliber than the vein, and the ratio of venous to arterial caliber was distributed from 1.0 to 2.5. The thickness of media was usually thicker in the vein than in the artery. Clusters of elastic fibers were found occasionally in the media of arteries and veins, and basement membrane-like materials were associated frequently with the elastic fibers and were distributed widely in the media as well as in the adventitia. In the veins, the smooth muscle cells of the most superficial part of the media contained well-developed rough endoplasmic reticulum and Golgi apparatus, indicating differentiation to secrete extracellular matrices. The present study revealed the difference of wall structure between arteries and veins in the placental stem villi for the first time at the ultrastructural level, and suggested differentiation of venous smooth muscle cells, possibly by some influence from the luminal side.

Morphological and immunocytochemical characterization of primary osteogenic cell cultures derived from fetal rat cranial tissue

Enzymatic digestion of bone tissue potentially releases a mixture of precursor, differentiating, and mature cells. Conceptually, early fetal osteogenic tissue should provide a more uniform population of cells than late embryonic or newborn bone in which cells have already differentiated. In this context, we have applied sequential enzymatic digestion to obtain and culture cells from 15-16-day fetal rat cranial tissue, a developmental age where deposition of bone matrix has not yet started at this site. These cultures were compared with those of osteogenic cells isolated from newborn rat calvariae and grown under similar conditions. Matrix production and composition were examined by colloidal gold immunocytochemistry using antibodies to bone sialoprotein (BSP), osteocalcin (OC), and osteopontin (OPN). The plated cells formed mineralized nodules by day 14. The presence of mineral was determined by von Kossa staining and backscattered electron imaging (BEI), and the accumulation of calcium and phosphorus within the nodules was demonstrated by X-ray microanalysis and elemental mapping. At early time intervals, cells were generally cuboidal in shape and showed a well-developed Golgi apparatus, which occasionally was immunoreactive for OPN. Labeling for BSP and OPN was found over mineralization foci and electron-dense material within, and at the periphery, of larger mineralized masses and over accumulations of afibrillar matrix at the dish surface. Osteocalcin immunoreactivity was also associated with electron-dense portions of the bone-like matrix. These data demonstrate the potential of presumptive fetal rat calvarial cells to form a bone-like matrix in vitro and suggest that the assembly and mineralization pattern show similarities to the process of intramembranous ossification. Such a culture system is of interest not only for studying cellular and matrix events of bone formation, but also factors which influence mesenchymal cells in committing themselves to the osteogenic pathway.

Morphological and immunocytochemical characterization of primary osteogenic cell cultures derived from fetal rat cranial tissue

Enzymatic digestion of bone tissue potentially releases a mixture of precursor, differentiating, and mature cells. Conceptually, early fetal osteogenic tissue should provide a more uniform population of cells than late embryonic or newborn bone in which cells have already differentiated. In this context, we have applied sequential enzymatic digestion to obtain and culture cells from 15–16-day fetal rat cranial tissue, a developmental age where deposition of bone matrix has not yet started at this site. These cultures were compared with those of osteogenic cells isolated from newborn rat calvariae and grown under similar conditions. Matrix production and composition were examined by colloidal gold immunocytochemistry using antibodies to bone sialoprotein (BSP), osteocalcin (OC), and osteopontin (OPN). The plated cells formed mineralized nodules by day 14. The presence of mineral was determined by von Kossa staining and backscattered electron imaging (BEI), and the accumulation of calcium and phosphorus within the nodules was demonstrated by X-ray microanalysis and elemental mapping. At early time intervals, cells were generally cuboidal in shape and showed a well-developed Golgi apparatus, which occasionally was immunoreactive for OPN. Labeling for BSP and OPN was found over mineralization foci and electron-dense material within, and at the periphery, of larger mineralized masses and over accumulations of afibrillar matrix at the dish surface. Osteocalcin immunoreactivity was also associated with electron-dense portions of the bone-like matrix. These data demonstrate the potential of presumptive fetal rat calvarial cells to form a bone-like matrix in vitro and suggest that the assembly and mineralization pattern show similarities to the process of intramembranous ossification. Such a culture system is of interest not only for studying cellular and matrix events of bone formation, but also factors which influence mesenchymal cells in committing themselves to the osteogenic pathway. Anat. Rec. 252:554–567, 1998. © 1998 Wiley-Liss, Inc.

Further observations on the gap-junction-rich cells in the deep muscular plexus of the rat small intestine.

Interstitial cells forming many large gap junctions in the region of the deep muscular plexus of the rat small intestine were studied by electron microscopy and by three-dimensional cell models reconstructed from serial ultrathin sections. Two different profiles of cells were observed. Cells of the first profile are characterized by an elongated cell shape and by less electron-dense cytoplasm, containing many mitochondria, well-developed Golgi apparatus and free ribosomes. They mainly connect with smooth muscle cells of the main circular layer. In a three-dimensional cell model, the total area of the gap junctions occupies 1.3% of the cell surface. Cells of the second profile are characterized by the frequent occurrence of slender cytoplasmic processes, higher electron-dense cytoplasm, containing mitochondria, Golgie apparatus and well-developed rough endoplasmic reticulum, and numerous caveolae on the cell membrane. In this cell model, gap junctions occupy 0.8% of the cell surface. The ratio of gap junctions with the same profile of cells to the total gap junction area is 37.7%, which is more than three times greater than the 9.9% in cells of the first profile. These cells were closely associated with nerve terminals. It is likely that these cells with different profiles constitute subtypes with each other and cooperate for regulation of intestinal motility via the transmission of nerve signals.

Immunoelectron microscopic identification of lysozyme-expressing cells in human labial salivary glands.

Although human labial gland secretions contain serous components such as the bactericidal enzyme, lysozyme, the presence of serous cells in this gland has yet to be clearly visualized under the electron microscope. The present study identifies lysozyme-expressing cells of the labial glands using microwave-fixed, Epon-Araldite-embedded specimens, which showed excellent preservation of both ultrastructural detail and antigenicity for post-embedding immunogold labeling of lysozyme. Ultrastructurally, all of the secretory cells of the glands appeared to be a mucous-type and have a serial maturation relationship, consistent with a previous report by TANDLER et al. (1969a): their secretory granules were electron-lucent and exhibited reactivity for mucus staining by the periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) method. We classified them into two immature types (I, II) and two mature types (I, II). Their distinctive features were the following: 1) relatively small (0.5-1 microm) secretory granules and well-developed basal rough endoplasmic reticulum for the immature types; 2) larger (1-2 microm) secretory granules and well-developed Golgi apparatus, which showed intense PA-TCH-SP reactivity in the 2-3 trans-cisterns, for the mature types; 3) few secretory granules in the immature type I; and 4) the darkest appearance for the mature type II. Immunogold labeling with anti-lysozyme showed specific labeling of the two immature-type cells, in which gold particles were found mainly over the secretory granules and Golgi apparatus, and moderately over the rough endoplasmic reticulum. In the secretory granules, the labeling was distributed throughout the contents and was present even if they showed strong PA-TCH-SP reactivity; in the Golgi area, it was seen over the stacked cisternae, trans-Golgi networks, and condensing vacuoles. No specific labeling was seen in the mature-type cells or in the duct cells. These immature- and mature-type cells were almost equivalent to the "serous demilune or acinus" and "mucous tubule" cells, respectively, at the light-microscopic level. These results indicate that the traditional "immature mucous-type cells" of the human labial glands produce lysozyme and should be classified as seromucous cells.

Control of venom production and secretion by sympathetic outflow in the snake Bothrops jararaca.

Many studies have examined the morphological and biochemical changes in the secretory epithelium of snake venom glands after a bite or milking. However, the mechanisms of venom production and secretion are not yet well understood. The present study was undertaken to evaluate the role of the sympathetic nervous system in the control of venom production and secretion. Venom glands were obtained from Bothrops jararaca (Viperidae) snakes, either unmilked previously or milked 4, 7 or 15 days before they were killed. Levels of tyrosine-hydroxylase-like immunoreactivity were higher in venom glands collected 4 days after milking, coinciding with the maximal synthetic activity of the secretory cells. The only catecholamine detected by high-performance liquid chromatography was noradrenaline, indicating the presence of noradrenergic fibres in these glands. In reserpine-treated milked snakes, no venom could be collected, and electron microscopic analysis showed narrow rough endoplasmic reticulum cisternae, instead of wide cisternae, and less well-developed Golgi apparatus compared with milked untreated snakes, indicating impairment of protein synthesis and secretion. The administration of isoprenaline or phenylephrine (beta- and alpha-adrenoceptor agonists, respectively) to reserpine-treated milked snakes promoted the widening of the rough endoplasmic reticulum and restored venom production, but only phenylephrine restored the development of the Golgi apparatus and the formation of many secretory vesicles. These results provide the first evidence that the sympathetic nervous system plays an important role in venom production and secretion in the venom glands of Bothrops jararaca. Understanding the importance of noradrenergic stimulation in venom production may provide new insights for research into the treatment of snakebites.

Isolating and maintaining highly polarized primary epithelial cells from normal human duodenum for growth as spheroid-like vesicles.

A method is described for the three-dimensional (3-D) in vitro culture of nontransformed gastrointestinal epithelial cells from the human duodenal mucosa. Biopsies obtained from human duodenum were finely minced. The tissue fragments were suspended in culture medium supplemented with 5% fetal calf serum and the appropriate antibiotics. The suspended mucosal fragments generated spheroid-like multicellular vesicles consisting of highly prismatic absorptive and goblet cells retaining most of the histological features of the tissue in vivo. We performed immunocytochemical studies to determine the origin of the vesicles using monoclonal antibodies against EP4. The histochemistry of the vesicles showed alkaline phosphatase activity. Ultrastructural studies revealed that these cells exhibit characteristics of normal duodenal cells in vivo: apical microvilli, glycocalyx, tight junctions and desmosomes, lateral membrane interdigitations, mucous droplets, and a well-developed Golgi apparatus. An overgrowth of the vesicles by fibroblasts was not seen during cultivation. In contrast with the two-dimensional cell cultures grown on artificial supports, the vesicle cells show organization similar to that of natural epithelia. The polarization and cytoarchitecture of normal gastrointestinal epithelial cells cultured as 3-D vesicles are comparable to those known for the native tissue. This study was undertaken to provide a morphological baseline for subsequent infection experiments.

Ultrastructural identification of the c-kit-expressing interstitial cells in the rat stomach: a comparison of control and Ws/Ws mutant rats.

Interstitial cells in the circular muscle layer of the stomach of the Ws/Ws mutant rat, which lacks c-kit-expressing cells, and its siblings have been studied by electron microscopy. In the sibling control rats, two types of interstitial cells are found lying in close association with nerve bundles. Cells of the first type are characterized by electron-dense cytoplasm containing abundant mitochondria, granular endoplasmic reticulum, and Golgi apparatus. Intermediate filaments are richly distributed throughout the perinuclear region and the cell processes. Caveolae, subsurface cisterns, and indistinct basal lamina are observed along the cell membrane. The most conspicuous feature of this cell type is the existence of many large gap junctions that interconnect with the same type of cell, smooth muscle cells, or cells of the second type. Cells of the second type show an ultrastructure similar to fibroblasts, viz., a well-developed Golgi apparatus and granular endoplasmic reticulum whose cisterns often show a dilated form and contain flocculent material. Unlike typical fibroblasts, however, cells of this type also form many gap junctions with cells of the first type and smooth muscle cells. Both types of cells are observed in close apposition to nerve varicosities. Since cells of the first type are absent in the Ws/Ws mutant rat, we concluded that they correspond to c-kit-expressing cells and to interstitial cells of Cajal.

Ultrastructural morphology of the dorsal lobe of the prostate gland in cadmium and zinc-treated rats

We have demonstrated in previous study that the nucli of the cells of the posterior lobe of the prostate gland sequesters less zinc in cadmium and zinc treated rats compared to the normal ones. In this study we will evaluate if the variation in the nuclear zinc concentration is associated with a concomitant variation in ultrastructural morphology. Two groups of animals were injected with 2mg/kg and 10 mg/kg cadmium chloride and zinc sulfate, respectively. Another group served as control. Dorsal lobe of the prostate gland from the three groups were prepared for conventional E.M study. Grids were examined and photographed by Hitachi-700 electron microscope.Figure (1) shows prostatic cells from the posterior lobe of the prostate gland of a normal rat. The rough endoplasmic reticulum form a narrow continuous cisternae, most abundant at the lateral portion of the cell and sometimes acquired whorl-shaped appearance. Well-developed Golgi apparatus with abundant secretory vesicles are shown.

Characterization of the interstitial cells associated with the submuscular plexus of the guinea-pig colon.

Interstitial cells associated with the submuscular plexus of the guinea pig colon were studied by electron microscopy and by light microscopic wholemount stretch preparations. Their cytoplasmic features are similar to those of fibroblasts and they contain a well-developed Golgi apparatus, granular endoplasmic reticulum and many mitochondria. Intermediate filaments are abundantly distributed throughout the perinuclear region and processes. Numerous caveolae, a basal lamina and subsurface cisterns are observed on the cell membrane as in smooth muscle cells. The most characteristic feature of this cell type is the existence of many large gap junctions that interconnect these cells to each other and with the smooth muscle cells. Nerve varicosities containing synaptic vesicles are observed in close apposition with cells of this type. Whole-mount preparations stained by the zinc iodide-osmic acid method and by vimentin immunohistochemistry clearly demonstrated the stellate form of these gap junction-rich cells and suggested that they correspond to the interstitial cells of Cajal.

Ultrastructural study of the noninvolved urothelium of tumor-bearing patients after two years of intravesical interferon therapy.

Seventeen patients with transitional cell carcinoma of the urinary bladder were studied. Twelve patients did not have a recurrence 2 years after a transurethral resection (TUR) followed by interferon (IFN)-alpha 2b treatment. This observation led us to study the ultrastructural morphology of the noninvolved urothelium in 8 of the above 12 patients. All patients had a primary solitary grade I or II tumor. Topical therapy was started after TUR. Each patient received a total of 22 instillations of 50 MU IFN-alpha 2b in 12 months according to the standard procedure. After the first year, a repetitive dose of 50 MU IFN-alpha 2b was administered every 2 months for a period of 1 more year. At the end of therapy, certain ultrastructural modifications were observed indicating a partial restoration of the urothelium: the existence of asymmetric unit membrane, a well-developed Golgi apparatus and an increase of the filaments. The cells were joined to each other with well-developed tight junctions. Tubuloreticular inclusions were also observed. Prevention of recurrence by restoring the morphology of the noninvolved urothelium in response to IFN treatment deserves further examination.