Tubules Of Smooth Endoplasmic Reticulum Research Articles

Патоморфологічні зміни нирок, печінки та біохімічні показники сироватки крові червоновухих прісноводних черепах (Trachemys scripta elegans) за парентерального введення гентаміцину

Principles of reptile treatment are significantly different from the drug therapy for mammals and birds, which is primarily due to anatomical and physiological peculiarities of reptiles. Gentamicin, which has a nephrotoxic effect, is used for the treatment of reptile infectious diseases. For the purpose of studying the effects of gentamicin of reptiles a serum biochemical analysis was conducted determining aspartate aminotransferase and alanine aminotransferase activity, urea and uric acid concentration. Two research groups of red-eared sliders (Trachemys scripta elegans) were formed for the study; every 48 hours they received an injection of gentamicin in a dose 10 mg/kg into thoracic limb muscles. The animals of the first research group were withdrawn from the experiment on the 7th day, and the animals of the second group were withdrawn on the 14th day of the research. As a result of parenteral administration of gentamicin in turtles, there is an increase in the concentration of uric acid and urea, as well as the activity of aspartate aminotransferases and alanine aminotransferases in blood serum. In the kidneys, structural changes of the glomeruli were found: alternative changes in podocytes, as well as degenerative and necrotic changes in the renal tubule epithelium. Degenerative changes of nephrocytes were accompanied by the dilation of smooth endoplasmic reticulum tubules, mitochondrial crista destruction, accumulation of autophagolysosomes, cytosomes and lysosomes in the cytoplasm. Furthermore, signs of nephrocyte apoptosis with the formation of apoptotic bodies were detected. A liver examination revealed dystrophic and necrotic changes in hepatocytes, expansion and overflow of the vessels of the venous beds.

Impacts of iron on ultrastructural features of NCI-H295R cell line related to steroidogenesis

The current study was intended to evaluate impacts of both iron (Fe) enrichment and overload (in the form of ferrous sulphate heptahydrate, FeSO4.7H2O) on ultrastructural characteristics of human adrenocarcinoma NCI-H295R cell line. Here, the NCI-H295R cells were treated with 0, 3.90, and 1000 µM FeSO4.7H2O, and consequently proceeded for purposes of ultrastructural studies. Micrographs taken under transmission electron microscope (TEM) were investigated from the qualitative and quantitative (unbiased stereological approaches) aspects, and obtained findings were compared among the three groups of the cells. The ultrastructural features related to the steroidogenic process were found to be similar between the untreated and both Fe-exposed cell populations, with conspicuous mitochondria with well-defined lamellar cristae (creating clusters of varying sizes in the regions of increased energy demands) and concentric whorls of smooth endoplasmic reticulum (SER) being the most noticeable characteristics. The precise estimates of the component (volume, surface) fractions of the nucleus, mitochondria, and lipid droplets (LDs), as well as of the nucleus/cytoplasm (N/C) ratio have revealed close similarities (P > 0.05) in all cell groups investigated. Nonetheless, the low concentration of FeSO4.7H2O exhibited beneficial action on ultrastructural organization of the NCI-H295R cells. In effect, these cells were distinguished by mitochondria with smoother surfaces and clearer outlines, higher density of thin, parallel lamellar cristae (deeply extending into the mitochondrial matrix), and more widespread distribution of fine SER tubules as compared to the control ones, all of them suggesting higher level of energy requirements and metabolic activity, and more intensive rate of steroidogenesis. Interestingly, no obvious ultrastructural modifications were observed in the NCI-H295R cells treated with high FeSO4.7H2O concentration. This finding can be linked to either an adaptive ultrastructural machinery of these cells to cope with the adverse effect of the element or to insufficient dose of FeSO4.7H2O (1000 µM) to induce ultrastructural signs of cytotoxicity. Purposefully, the results of the current study complement our previous paper dealing with impacts of FeSO4.7H2O on the NCI-H295R cell viability and steroidogenesis at the molecular level. Hence, they fill a knowledge gap considering structure-function coupling in this cellular model system upon the metal exposure. This integrated approach can enhance our understanding of the cellular responses to Fe enrichment and overload which can be helpful for individuals with reproductive health concerns.

All that glitters is not gold: a stereological study of human donor oocytes

Here we report a quantitative analysis of human metaphase II (MII) oocytes from a 22-year-old oocyte donor, retrieved after ovarian-controlled hyperstimulation. Five surplus donor oocytes were processed for transmission electron microscopy (TEM), and a stereological analysis was used to quantify the distribution of organelles, using the point-counting technique with an adequate stereological grid. Comparisons between means of the relative volumes (Vv) occupied by organelles in the three oocyte regions, cortex (C), subcortex (SC) and inner cytoplasm (IC), followed the Kruskal-Wallis test and Mann-Whitney U-test with Bonferroni correction. Life cell imaging and TEM analysis confirmed donor oocyte nuclear maturity. Results showed that the most abundant organelles were smooth endoplasmic reticulum (SER) elements (26.8%) and mitochondria (5.49%). Significant differences between oocyte regions were found for lysosomes (P = 0.003), cortical vesicles (P = 0.002) and large SER vesicles (P = 0.009). These results were quantitatively compared with previous results using prophase I (GV) and metaphase I (MI) immature oocytes. In donor MII oocytes there was a normal presence of cortical vesicles, SER tubules, SER small, medium and large vesicles, lysosomes and mitochondria. However, donor MII oocytes displayed signs of cytoplasmic immaturity, namely the presence of dictyosomes, present in GV oocytes and rare in MI oocytes, of SER very large vesicles, characteristic of GV oocytes, and the rarity of SER tubular aggregates. Results therefore indicate that the criterion of nuclear maturity used for donor oocyte selection does not always correspond to cytoplasmic maturity, which can partially explain implantation failures with the use of donor oocytes.

Submicroscopic changes in the heart of adult rats under conditions of persistent hyperhomocystemia

Cardiovascular diseases are the leading cause of death and disability worldwide. It has been established that in recent years there has been a significant increase in the number of patients with this pathology, forcing researchers, scientists and physicians to look for risk factors of cardiovascular diseases, one of which is hyperhomocysteinemia (HHCys). The aim of the research is to study the features of submicroscopic changes in the heart of adult rats under conditions of HHCys. Experimental studies were performed on 22 white nonlinear adult (6-8 months) male rats in accordance with the principles of bioethics (Strasbourg, 1986; Kyiv, 2001). During the experiment, the animals were divided into two groups – control and experimental. Simulation of persistent HHCys was achieved by administering to rats the experimental group thiolactone homocysteine (HCys) at a dose of 200 mg/kg body weight intragastrally for 60 days. Ultrathin sections were studied in the PEM – 125K electron microscope. It was found that the introduction of thiolactone HCys to adult rats at a dose of 200 mg/kg causes the development of dystrophic and destructive changes in the heart of animals. Significant connective tissue edema was observed in the endocardium, and disturbances in the components of the microcirculatory tract were detected in the myocardium. Local enlightenment, cytoplasmic edema and local condensation of heterochromatin in hypertrophied nuclei were detected in hemocapillary endothelial cells. In cardiomyocytes, myofibrils are thickened, mitochondria are swollen with partial destruction of the cristae, tubules of smooth endoplasmic reticulum and T-tubules are dilated. These findings indicate that in adult rats HHCys caused the development of pathological changes in the endocardium, myocardium of experimental animals and in the microcirculatory tract.

The ER ladder is a unique morphological feature of developing mammalian axons.

The endoplasmic reticulum (ER) confronts a challenge to accommodate long, smooth ER tubules into the structural complexity of the axonal compartment. Here, we describe a morphological feature for the axonal ER network in developing neurons we termed the ER ladder. Axonal ER ladders are composed of rungs that wrap tightly around the microtubule bundle and dynamic rails, which slide across microtubules. We found that the ER-shaping protein Reticulon 2 determines the architecture and dynamics of the axonal ER ladder by modulating its interaction with microtubules. Moreover, we show that ER ladder depletion impairs the trafficking of associated vesicular axonal cargoes. Finally, we demonstrate that stromal interaction molecule 1 (Stim1) localizes to ER rungs and translocates to ER-plasma membrane contact sites upon depletion of luminal Ca2+. Our findings uncover fundamental insights into the structural and functional organization of the axonal ER network in developing mammalian neurons.

Pure Smooth Endoplasmic Reticulum (SER) Inclusions in Granulocytes of MYH9-Related Disorder Patients

MYH9-related disorders are a group of disorders (May-Hegglin anomaly, Fechtner syndrome, Sebastian syndrome) characterized by macrothrombocytopenia and ribosome inclusions in granulocytes. They are caused by mutations in the MYH9 gene and, depending on the location of the mutation, are associated with extrahematological pathologies (sensorineural hearing loss, progressive nephropathy, presenile cataracts) of variable intensity.The inclusions are formed by single and clustered ribosomes and are partially surrounded by segments of rough endoplasmic reticulum (RER). Typical inclusions in May-Hegglin anomaly are spindle-shaped, well-defined, and contain longitudinal filaments. Those found in Sebastian and Fechter syndromes are round or oval, have no filaments and, sometimes, show cross-striated arrangement of the ribosome aggregates.When reviewing the electron micrographs of the granulocyte inclusions of 10 patients with MYH9-related disorders previously published (Pujol-Moix et al. Haematologica 2004;89:330-337) we observed a special type of inclusion not described in the article. This inclusion has the typical appearance of smooth endoplasmic reticulum (SER) clusters, that is, a meshwork of branching tubules of SER without limiting membranes and no other structures such as ribosomes or RER. In 3 of the patients reviewed, in addition to the typical inclusions of MYH9-related disorder, some granulocytes with SER clusters were observed. These clusters were rounded or oval in shape and, when present, were 1 or 2 per cell (Fig. 1).The patients who presented granulocyte SER clusters are those identified as B4, C6 and D8 in the Haematologica article and are briefly described in Table 1. The patients presenting with SER clusters showed different characteristics such as age, bleeding, platelet counts, and proportion of giant platelets. Therefore, we cannot relate the presence of SER clusters to any clinical or biological characteristic of patients. It should be noticed that we did not find SER clusters in any patient with May-Hegglin anomaly. However, the small number of cases studied does not allow any conclusions to be drawn.SER clusters have been described in different types of cells such as hepatocytes or kidney tubular epitelial cells (Ghadially FN. Ultrastructural Pathology of the Cell and Matrix. Butterwords. London, 1988, pp 422-427). Normal granulocytes (neutrophils, eosinophils, and basophils) besides their own specific granules, also contain other general subcellular structures, including dispersed SER membranes. However, SER membranes forming clusters in these cells have not been previously described. In addition, SER clusters do not seem to correspond to evolved forms of typical MYH9 inclusions, for example by degranulation of the RER, based on the observations that typical inclusions show abundant ribosomes but few RER segments, no appreciable ribosomes are observed in the SER clusters, and the morphology of the tubules forming the SER and RER is different.We suggest that SER clusters could be considered a new type of inclusion in MYH9-related disorders. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Динамика ультраструктурных изменений хориоретинального комплекса глаз крыс, вызванных большой дозой метанола

The structure of chorioretinal complex (CRC) of rat eyes was studied by electron microscopy: choriocapillaris, retinal pigment epithelium (RPE) and retinal photoreceptor cells after 40 minutes, 1 hour and 10 minutes, on the first 1 st , 3 rd , 7 th and 14 th days after a single intraperitoneal injection of methanol in a dose of 7.0 g/kg of body weight. It was shown that the primary and significant destructive changes in the structures of the studied complex were observed in the RPE cells, which are characterized by alteration of mitochondria and tubules of smooth endoplasmic reticulum, equation of basal folds and local destruction of the apical microvilli. The destructive processes in the cells were growing in the dynamics of CRC structures research. In parallel, the features of compensatory-regenerative processes in these cells were detected.

Reversible interactions between smooth domains of the endoplasmic reticulum and mitochondria are regulated by physiological cytosolic Ca2+ levels

The 3F3A monoclonal antibody to autocrine motility factor receptor (AMFR) labels mitochondria-associated smooth endoplasmic reticulum (ER) tubules. siRNA down-regulation of AMFR expression reduces mitochondria-associated 3F3A labelling. The 3F3A-labelled ER domain does not overlap with reticulon-labelled ER tubules, the nuclear membrane or perinuclear ER markers and only partially overlaps with the translocon component Sec61alpha. Upon overexpression of FLAG-tagged AMFR, 3F3A labelling is mitochondria associated, excluded from the perinuclear ER and co-distributes with reticulon. 3F3A labelling therefore defines a distinct mitochondria-associated ER domain. Elevation of free cytosolic Ca(2+) levels with ionomycin promotes dissociation of 3F3A-labelled tubules from mitochondria and, judged by electron microscopy, disrupts close contacts (<50 nm) between smooth ER tubules and mitochondria. The ER tubule-mitochondria association is similarly disrupted upon thapsigargin-induced release of ER Ca(2+) stores or purinergic receptor stimulation by ATP. The inositol (1,4,5)-trisphosphate [Ins(1,4,5)P(3)] receptor (IP3R) colocalises to 3F3A-labelled mitochondria-associated ER tubules, and conditions that induce ER tubule-mitochondria dissociation disrupt continuity between 3F3A- and IP3R-labelled ER domains. RAS-transformed NIH-3T3 cells have increased basal cytosolic Ca(2+) levels and show dissociation of the 3F3A-labelled, but not IP3R-labelled, ER from mitochondria. Our data indicate that regulation of the ER-mitochondria association by free cytosolic Ca(2+) is a characteristic of smooth ER domains and that multiple mechanisms regulate the interaction between these organelles.

Transmission electron microscopy study of the effects of cadmium and copper on fetal rat liver tissue

During the entire period of their pregnancies, three groups of adult pregnant Wistar albino rats were provided with tap water (control; group I) or with tap water containing 10 mg/kg CdCl2 (group II) or 10 mg/kg CdCl2 plus 10 mg/kg CuSO4 (group III). At term, the animals were sacrificed and the fetal livers were removed and examined under electron microscopy. The liver tissue of the fetuses in maternal groups II and III showed degenerative changes to their hepatocytes. In group II, the smooth endoplasmic reticulum tubules showed dilatation, and the mitochondria showed a dense matrix. In group III, some mitochondrial degeneration was also seen, with a diluted matrix and mitochondrial dilatation. There were also more heterochromatic nuclei and an increased number of ribosomes. None of these histopathological changes were present in the fetal liver samples from the maternal group I control animals.

Synaptic ribbon plasticity, ribbon size and potential regulatory mechanisms in utricular and saccular maculae

The mean number of synaptic ribbons in type II hair cells of the rat utricular macula increased significantly in weightlessness. In contrast, ribbon synapses of saccular type I hair cells displayed a significant decline early inflight and postflight, and a late numerical overshoot. Further study indicated that the saccular macula had less ultrastructural complexly than the utricular. Additionally, synaptic ribbons were statistically larger in type II hair cells of both maculae, apparently a locus-related scaling effect. A major new finding is that mitochondria in calyces and collateral terminals were linked to vesicles, tubules of smooth endoplasmic reticulum and cell membranes by filaments, forming mitochondrial complexes (MCs). MCs predominated basally in the calyx where calyceal/type I hair cell borders were bound by filaments; at calyceal invaginations of type I hair cells; in calyces and collaterals near synaptic ribbon sites; and in collaterals near reciprocal synapses. MCs may participate in feedback mechanisms at these locations to help regulate synaptic ribbon activity and plasticity in altered gravitational environments.

Transmission electron microscopy study of the effects of zinc overdose on mouse liver tissue.

Thirty adult male mice were divided into three groups. The animals in group I were used as controls and drank only water during the entire period of experimentation. Group II animals drank water containing 1.5 g/100 mL zinc as ZnSO4, and group III animals received 2.5 g/100 mL zinc. After 3 wk supplementation with high doses of zinc, the animals were killed and the livers were removed and examined by electron microscopic techniques. After the supplementation period, the animals in groups II and II showed various degrees of degenerative changes in the hepatocytes, such as increased size and the presence of spaces and an abundance of lipid globules in the cytoplasm. The mitochondria showed a crystalline appearance, a diluted matrix, and dense aggregations. Some smooth endoplasmic reticulum tubules showed dilation and were filled with a dense substance. None of these changes were present in the group I control animals.

Three-Dimensional Organization of Smooth Endoplasmic Reticulum in Hippocampal CA1 Dendrites and Dendritic Spines of the Immature and Mature Rat

Recent studies have shown high levels of calcium in activated dendritic spines, where the smooth endoplasmic reticulum (SER) is likely to be important for regulating calcium. Here, the dimensions and organization of the SER in hippocampal spines and dendrites were measured through serial electron microscopy and three-dimensional analysis. SER of some form was found in 58% of the immature spines and in 48% of the adult spines. Less than 50% of the small spines at either age contained SER, suggesting that other mechanisms, such as cytoplasmic buffers, regulate ion fluxes within their small volumes. In contrast, >80% of the large mushroom spines of the adult had a spine apparatus, an organelle containing stacks of SER and dense-staining plates. Reconstructed SER occupied 0.001-0.022 microm3, which was only 2-3.5% of the total spine volume; however, the convoluted SER membranes had surface areas of 0.12-2.19 microm2, which were 12 to 40% of the spine surface area. Coated vesicles and multivesicular bodies occurred in some spines, suggesting local endocytotic activity. Smooth vesicles and tubules of SER were found in continuity with the spine plasma membrane and margins of the postsynaptic density (PSD), respectively, suggesting a role for the SER in the addition and recycling of spine membranes and synapses. The amount of SER in the parent dendrites was proportional to the number of spines and synapses originating along their lengths. These measurements support the hypothesis that the SER regulates the ionic and structural milieu of some, but not all, hippocampal dendritic spines.

Ultrastructurally different muscle cell types in Eisenia foetida (Annelida, Oligochaeta).

Muscles in the body wall, intestinal wall, and contractile hemolymphatic vessels (pseudohearts) of an oligochaete anelid (Eisenia foetida) were studied by electron microscopy. The muscle cells in all locations, except for the outer layer of the pseudohearts, are variants of obliquely striated muscle cells. Cells comprising the circular layer of the body wall possess single, peripherally located myofibrils that occupy most of the cytoplasm and surround other cytoplasmic organelles. The nuclei of the cells lie peripherally to the myofibrils. The sarcomeres consist of thin and thick myofilaments that are arranged in parallel arrays. In one plane of view, the filaments appear to be oriented obliquely to Z bands. Thin myofilaments measure 5-6 nm in diameter. Thick myofilaments are fusiform in shape and their width decreases from their centers (40-45 nm) to their tips (23-25 nm). The thin/thick filament ratio in the A bands is 10. The Z bands consist of Z bars alternating with tubules of the sarcoplasmic reticulum. Subsarcolemmal electron-dense plaques are found frequently. The cells forming the longitudinal layer of the body wall musculature are smaller than the cells in the circular layer and their thick filaments are smaller (31-33 nm centrally and 21-23 nm at the tips). Subsarcolemmal plaques are less numerous. The cells forming the heart wall inner layer, the large hemolymphatic vessels, and the intestinal wall are characterized by their large thick myofilaments (50-52 nm centrally and 27-28 nm at the tips) and abundance of mitochondria. The cells forming the outer muscular layer of the pseudohearts are smooth muscle cells. These cells are richer in thick filaments than vertebrate smooth muscle cells. They differ from obliquely striated muscle cells by possessing irregularly distributed electron-dense bodies for filament anchorage rather than sarcomeres and Z bands and by displaying tubules of smooth endoplasmic reticulum among the bundles of myofilaments. © 1995 Wiley-Liss, Inc.

Pollen wall development in Vigna vexillata II. Ultrastructural studies

Ultrastructural studies to determine the role of cytoplasmic organelles in pollen wall development in Vigna vexillata L. (Fabaceae) showed that plastids, mitochondria, and vacuoles do not directly participate in pollen wall morphogenesis, as inferred from their cytoplasmic distribution during microsporogenesis and pollen development. Spatial and temporal correlations between elements of the endomembrane system and pollen wall development suggest that dictyosomes, the endoplasmic reticulum, and multimembrane inclusions are involved in synthesis, processing, and/or transport of precursors for the various pollen wall layers. Large numbers of dictyosome‐derived vesicles appear during development of the primexine matrix, the patterned primexine, and the apertural Zwischenkörper, suggesting that dictyosomes are involved in development of these layers. Tubules of smooth endoplasmic reticulum, preferentially located under developing primexine ridges and extending to the vicinity of the plasma membrane, support the hypothesis of endoplasmic reticulum involvement in pollen wall pattern formation. Multimembrane inclusions, abundant in the cortical cytoplasm of developing microspores, may be involved in development of the lamellate endexine.

Pollen Wall Development in Vigna vexillata. II. Ultrastructural Studies

Ultrastructural studies to determine the role of cytoplasmic organelles in pollen wall development in Vigna vexillata L. (Fabaceae) showed that plastids, mitochondria, and vacuoles do not directly participate in pollen wall morphogenesis, as inferred from their cytoplasmic distribution during microsporogenesis and pollen development. Spatial and temporal correlations between elements of the endomembrane system and pollen wall development suggest that dictyosomes, the endoplasmic reticulum, and multimembrane inclusions are involved in synthesis, processing, and/or transport of precursors for the various pollen wall layers. Large numbers of dictyosome-derived vesicles appear during development of the primexine matrix, the patterned primexine, and the apertural Zwischenkörper, suggesting that dictyosomes are involved in development of these layers. Tubules of smooth endoplasmic reticulum, preferentially located under developing primexine ridges and extending to the vicinity of the plasma membrane, support the hypothesis of endoplasmic reticulum involvement in pollen wall pattern formation. Multimembrane inclusions, abundant in the cortical cytoplasm of developing microspores, may be involved in development of the lamellate endexine.

Ultrastructural evidence of mature Leydig cells and Leydig cell regression in the neonatal human testis

The neonatal period in male development is characterized by an acute rise in serum testosterone, which peaks at 2 to 3 months of age. The purpose of this study is to examine the neonatal human testicular interstitium at 4 months for evidence of Leydig cell maturation, as well as any morphological criteria relating to the fate of Leydig cells during this period, specifically, for signs of cell regression. Leydig cells are described with impressive development of the steroid secreting apparatus, which are consistent with the mature Leydig cells found during early fetal development and in the adult. The outstanding feature of these cells is the "organelle association" of extensive, anastamosing tubules of smooth endoplasmic reticulum (SER), pleomorphic mitochondria with a component of tubular cristae, and abundant microperoxisomes associated with the SER. Well-developed Golgi elements, regionalized RER, and diverse cell inclusions are also characteristics of these cells. Reinke crystals and paracrystalline inclusions are absent. Gap junctions are common in this system and are notable in the asymmetric nature of the adjacent cytoplasmic components. These findings provide a morphologic correlate to the reported neonatal phase of testosterone production in man. Intermediate forms of Leydig cells are described with "organelle associations" including decreased SER with increased lipid droplets, and decreased SER with prominent cytoplasmic filaments and/or dramatic mitochondrial changes supportive of mitochondrial involution. Cells consistent with immature Leydig cells are also present. The rather impressive diversity in cell morphology present during this time frame of 4 months, slightly past the peak in testosterone production, provides evidence of Leydig cell regression and a continuity of the mature neonatal Leydig cells with the immature Leydig cells of childhood (Prince, 1984). There is also some evidence of cell degeneration. Although the developmental history of Leydig cells has been described for years as biphasic, it is time to view Leydig cell development in man as a triphasic event, fetal, neonatal, and pubertal.

Stereological and functional investigations on isolated adrenocortical cells: Zona fasciculata/reticularis cells of chronically ACTH-treated rats

The morphology and function of isolated inner (zona fasciculata/reticularis) adrenocortical cells of rats pretreated with ACTH for 3, 6, 9 or 12 days were investigated. ACTH treatment induced a notable time-dependent enhancement in the steroidogenic capacity (corticosterone production) and growth of inner cells. The volumes of cells, mitochondrial compartment, membrane space [the cellular space occupied by smooth endoplasmic reticulum (SER) membranes] and lipid-droplet compartment, as well as the surface area of mitochondrial cristae and SER tubules, were increased in relation to the duration of ACTH pretreatment, and showed a highly significant positive linear correlation with both basal and stimulated corticosterone production. The acute exposure of isolated cells to ACTH provoked a striking lipid-droplet depletion, the extent of which was linearly and positively correlated with stimulated corticosterone secretion. The hypertrophy of the mitochondrial compartment and SER are interpreted as the morphological counterpart of the enhanced steroidogenic capacity of inner adrenocortical cells, inasmuch as the enzymes of steroid synthesis are located in these two organelles, and it is well known that chronic ACTH exposure stimulates the de novo synthesis of many of them in vivo. The rise in the number of lipid droplets, in which cholesterol is stored, is interpreted as being due to the fact that, under chronic ACTH treatment, the processes leading to cholesterol accumulation in adrenocortical cells (exogenous uptake and endogenous synthesis) exceed those of its utilization in basal steroid secretion. Cholesterol accumulated in lipid droplets as a reserve material may be rapidly utilized after acute ACTH exposure to meet the needs of the enhanced steroidogenic capacity of adrenocortical cells.

Distribution and Structure of the Adrenocortical Homolog in the Reed‐Fish (Calamoichthys calabaricus Smith)

AbstractThe adrenocortical homolog (AH) was identified in the reed‐fish (Calamoichthys calabaricus Smith) using histochemistry for the enzyme δ5‐3β‐hydroxysteroid dehydrogenase (3β‐HSD) and its distribution and structure were examined with both light and electron microscopy. AH appears as yellow corpuscles which extend as isolated bodies throughout the length of both kidneys in close apposition to the posterior cardinal veins. The yellow corpuscles are composed of convoluted cords of epithelial cells and tortuous sinusoids which empty directly into the cardinal veins. Wide lateral intercellular spaces and accompanying microvilli give the impression of pseudotubules or pseudofollicles to the cords of epithelial cells. The extensive network of tubules of smooth endoplasmic reticulum, the many mitchondria with tubulo‐vesicular cristae, the conspicuous Golgi apparatus, lipid droplets, many pleomorphic granules and the presence of 3β‐HSD are indicative of the steroidogenic nature of the cells. Large, pleomorphic mitochondria and gap junctions are also typical of most cells. The fine structure of the cells in the AH of the reed‐fish most closely resembles that of other Polypteriformes, but the tissue is more widely distributed in the kidneys than in any osteichthylian so far reported.

Ultrastructural study of the alveolar‐capillary membrane and the tubular endoplasmic reticulum in alveolar type I cells of the caprine lung

The ultrastructural features of alveolar type I cells of the goat lung were studied by using vascular perfusion and direct airway instillation of fixatives. The morphological features of smooth endoplasmic reticulum (SER) were characterized by measuring the diameter of individual SER tubules which conformed in size and appearance to the tubular endoplasmic reticulum (TER) already described in various types of epithelium. The TER appeared as large tubular aggregates in a palisade arrangement; these aggregates ramified into various areas of the extended cytoplasm of alveolar type I cells. The TER also existed as a mixture of short cisternae and vesicles, and glycogen alpha particles were present in the non-perikaryonic portion of the cell. The different forms of TER had varying relationships to the plasmalemma. The interchangable configurations seen in the structure of TER indicated the functional modalities of the cells and were comparable to similar structural modifications in electrolyte-secreting cells. The role of TER, microtubules, and large populations of endocytic vesicles in the alveolar type I cells in the goat lung is examined in the context of physiological eructation of rumenal gases and the absorption of electrolyte-rich fluids which escape into the lung at each eructation in ruminants.

Structural alteration and possible growth of afferents after kainate lesion in the adult rat thalamus.

Afferents to the thalamic ventrobasal complex (VB) originating from the spinal cord, the dorsal column nuclei, and the somatosensory cortex were anterogradely labeled by WGA-HRP 30 days after an injection of kainic acid (KA), which produced a complete unilateral neuronal loss in the VB, the opposite side being used as a control. At the light microscopic level, there was no obvious rerouting of spinal afferents away from the lesioned areas towards unlesioned parts of VB. There was an apparent decrease in the number of lemniscal afferents to the lesioned side, which may indicate a progressive retrograde degeneration. At higher magnification, all three afferent systems studied demonstrated morphological changes, predominantly manifested by terminal swellings that reached up to 25 micron in diameter. Control experiments suggested that these morphological alterations were related neither to a direct action of the excitotoxin nor to the absence of a different afferent system but to the loss of neuronal postsynaptic targets. At the electron microscopic level, the normal ultrastructural features of VB were not observed after a KA lesion. No neuronal somata, dendrites, or normal presynaptic elements were observed. Neural elements, some of which were labeled from the somatosensory cortex or the dorsal column nuclei, were essentially of two types: varicosities and unmyelinated axonal profiles. Varicosities could be separated into two broad classes: The majority were large structures derived from large, sometimes myelinated, axons and containing a wealth of organelles. Since they were not completely surrounded by glial elements, we have denoted them unensheathed varicosities. Among the organelles, the most obvious features were vesicles and tubules of smooth endoplasmic reticulum, microtubules, mitochondria, and various lysosome-like inclusions. These unensheathed varicosities gave rise to large, mound-like protrusions containing large vacuoles and thin long protrusions either filled with neurofilaments or resembling unmyelinated axonal profiles. Others were completely surrounded by a glial sheet and were therefore called ensheathed varicosities. These ensheathed varicosities presented several characteristics typical of degenerating profiles, including neurofilamentous proliferation and morphological alterations of the mitochondria. Unmyelinated axonal profiles occupied a substantial territory in the lesioned area. They were most often grouped in bundles sometimes wrapped by glial processes.(ABSTRACT TRUNCATED AT 400 WORDS)