Synthetic Organelles Research Articles

Thinning of fetal pulmonary arterial wall and postnatal remodelling: ultrastructural studies on the respiratory unit arteries of the pig.

Adaptation to extra-uterine life and postnatal remodelling of intra-acinar arteries was followed in 34 Large White pigs, from birth to adult life, applying morphometry to light and electronmicroscopic studies. After birth, percentage wall thickness decreased rapidly due to a reduction in overlap of adjacent smooth muscle cells and an increase in smooth muscle cell surface area/volume ratio, (p less than 0.01 at 12 h), without a reduction in the volume density of smooth muscle cells. Smooth muscle cells appeared immature at birth and synthetic rather than contractile organelles predominated. Between 3 weeks and 6 months myofilament volume density doubled (p less than 0.0001). At all ages, pericytes, intermediate and smooth muscle cells showed similar volume densities of contractile and synthetic organelles. Thus, the high fetal pulmonary vascular resistance appeared to be due to the shape and arrangement of smooth muscle and other contractile cells within the vessel wall, rather than an excessive contractility of these cells. After birth rapid remodelling of arterial wall structure achieved a reduction in wall thickness by 30 min, continuing during the first week of life. After 3 weeks, remodelling involved an increase in wall thickness, connective tissue deposition with more collagen than elastin (p less than 0.0001), and smooth muscle cell differentiation.

Smooth muscle phenotypic expression in human carotid arteries. II. Atherosclerosis-free diffuse intimal thickenings compared with the media.

The volume fraction of synthetic organelles in smooth muscle cells from areas of atherosclerosis-free, diffuse intimal thickenings (DIT) and media of human carotid artery has been determined morphometrically. Tissue was obtained at autopsy from men and women aged 35 to 80 years, at 6 to 12 hours after death. With both sexes, the volume fraction of synthetic organelles in smooth muscle cells from the DIT was not significantly different from the volume fraction of synthetic organelles in cells of the subjacent media (0.25 and 0.21, respectively). This is in marked contrast to our earlier study in which the volume fraction of synthetic organelles in smooth muscle cells of DIT from a similar region of artery, but adjacent to atheromatous plaques, was highly significantly different from cells of the subjacent media (0.48 and 0.23, respectively). Only in regions near atherosclerotic plaques do the majority of smooth muscle cells of DIT express a different phenotype from cells of the media.

Immunocytochemical localization of the major surfactant apoproteins in type II cells, Clara cells, and alveolar macrophages of rat lung.

The adsorptive properties of phospholipids of pulmonary surfactant are markedly influenced by the presence of three related proteins (26-38 KD, reduced) found in purified surfactant. Whether these proteins are pre-assembled with lipids before secretion is uncertain but would be expected for a lipoprotein secretion. We performed indirect immunocytochemistry on frozen thin sections of rat lung to identify cells and intracellular organelles that contain these proteins. The three proteins, purified from lavaged surfactant, were used to generate antisera in rabbits. Immunoblotting of rat surfactant showed that the IgG reacted with the three proteins and a 55-60 KD band which may be a polymer of the lower MW species. Specific gold labeling occurred over alveolar type II cells, bronchiolar Clara cells, alveolar macrophages, and tubular myelin. In type II cells labeling occurred in synthetic organelles and lamellar bodies, which contain surfactant lipids. Lamellar body labeling was increased fivefold by pre-treating tissue sections with a detergent. Multivesicular bodies and some small apical vesicles in type II cells were also labeled. Secondary lysosomes of alveolar macrophages were immunoreactive. Labeling in Clara cells exceeded that of type II cells, with prominent labeling in secretory granules, Golgi apparatus, and endoplasmic reticulum. These observations clarify the organelles and pathways utilized in the elaboration of surfactant. After synthesis, the proteins move, probably via multivesicular bodies, to lamellar bodies. Both lipids and proteins are present in tubular myelin. Immunologically identical or closely similar proteins are synthesized by Clara cells and secreted from granules which appear not to contain lipid. The role of these proteins in bronchiolar function is unknown.

Ultrastructural observations on gastrodermal regeneration in the planarian Dugesia japonica (Turbellaria)

The earliest detectable change during regeneration of the gastrodermis in Dugesia japonica was an aggregation of regenerative cells underneath the gastrodermis remaining at the wound margin. The gastrodermal cells in experimental regenerates retained some of their original characters and presented no indication of cell dedifferentiation. The regenerative cells came into contact with the basal surface of gastrodermal cells, forming stratified cell layers. Differentiation of these cells into gastrodermal cells was initiated by the development of synthetic organelles within their cytoplasm. These differentiating cells gave rise to two different types of gastrodermal cells, namely phagocytic cells and sphere cells. In later stages, there was an apparent movement of differentiated gastrodermal cells towards the parenchyma.

Immunoelectronmicroscopic study on the transport of secretory IgA in the lower respiratory tract and alveoli.

To define the immunocytochemical localization of secretory component (SC), IgA and J chain in human bronchioles and alveoli, a direct peroxidase-labeled antibody method was used. SC was found in non-ciliated cells of the bronchioles including respiratory bronchioles and type II alveolar epithelial cells, whereas SC was rarely present in ciliated cells and type I alveolar epithelial cells and was absent from goblet cells. In the positively reacting cells, SC was found in secretory protein synthetic organelles such as perinuclear spaces and endoplasmic reticulum, Golgi complexes, and on the external surfaces of the apical and basolateral plasma membranes. IgA and J chain were localized in the epithelial cells where SC was found. Ultrastructually IgA was present on the apical and basolateral plasma membranes, in pinocytic invaginations of the membranes, and in vesicles distributed through the cytoplasm, especially in the apical cytoplasm of the epithelial cells where SC was found. In addition, IgA and J chain were found to be associated with the endothelial cells of the capillaries, plasma cells and the surrounding interstitium. These observations suggest that SC is synthesized and secreted by epithelial cells, especially non-ciliated cells of the bronchioles including respiratory bronchioles and type II alveolar epithelial cells. They also suggest that secretory IgA (sIgA) is transported into alveolar spaces and the bronchiolar lumen through these cells by SC-mediated transport mechanism. This sIgA may play an important role in defense mechanisms of the lower respiratory tract and alveoli.

Nocturnal rhabdom cycling and retinal hemocyte functions in crayfish (Procambarus) compound eyes. II. Transmission electron microscopy and acid phosphatase localization

AbstractCytoplasmic synthetic organelles (Golgi complexes, polysomes, and rough and smooth endoplasmic reticulum) are present in most photoreceptor cells of the crayfish retina in winter throughout the late‐night 24:00 to 06:00 h period. These same retinular cells contain few or no lysosome‐like bodies. There is no evidence for autophagic receptor membrane breakdown even during the degradative phase (24:00 to 02:00 h) of the late‐night quadrant.The fine structure of rhabdom microvillus bases and their continuity with retinular cell somata and endoplasmic reticulum differ characteristically in each of the three successive turnover phases between 24:00 and 06:00 h. Typical stalked attachment of microvillus clusters to retinular cell bodies is resumed by 06:00 h.A minority of retinulas are severely abnormal. Their rhabdoms are shorter and closer to the basement membrane while their receptor cell nuclei have descended proximally. During the degradative phase, the retinular somata may lack synthetic organelles altogether while their rhabdoms are disorganized, detached from their parent cytoplasm, and occasionally invaded by hemocytes. In contrast, synthetic organelles are numerous in the cytoplasm during the late synthetic phase (03:00 to 04:00 h) when photoreceptor membranes are less disrupted and cytoplasmic bridges between rhabdoms and cell bodies are intact.Both moderate late‐night degradation of the rhabdom and the less frequent catastrophic breakdown seem to be mediated by extracellular lysozymes provided in part by retinal hemocytes. Acid phosphatase localization at the beginning of the degradative phase (24:00 to 00:30 h) demonstrates that invasive granulocytes are a primary source of this enzyme. Another hemocyte function previously hypothesized is proven here by finding phagocytized fragments of rhabdom and other retinal elements in most of the retinal macrophages during late‐night synthetic and resting phases.

Previtellogenic development and vitellogenin synthesis in the fat body of a mosquito: An ultrastructural and immunocytochemical study

We describe two phases, previtellogenic and vitellogenic, in the activity of the trophocytes in the fat body of the mosquito Aedes aegypti. The previtellogenic phase, leading to trophocyte competence to synthesize vitellogenin (Vg), occurred during the first 3 days after eclosion. This phase was characterized by enlargement and activation of the nucleoli, proliferation of ribosomes and rough endoplasmic reticulum (RER), development of Golgi complexes, and extensive invaginations of the plasma membrane. During the vitellogenic phase, initiated by a blood meal, Vg was first detected, by immunofluorescencc, 1 hr after feeding. The intensity of the immunoreaction increased for the next 24 hr, was declining at 30 hr, and had disappeared by 48 hr. Vg synthesis was characterized ultrastructurally by the enlargement of the RER and the formation of dense secretion granules in Golgi complexes. These secretion granules were two to three times larger at the peak of Vg synthesis than at the beginning. The granules discharged their contents by exocytosis. Two electron microscopical immunocytochemical methods, immunoferritin and peroxidase-antiperoxidase, confirmed this pathway of Vg processing. For the first 12 hr after feeding, Vg synthetic organelles proliferated and the active nucleoli were multilobed; thereafter, while Vg synthesis continued, the nucleoli began to regress into compact bodies. Termination of Vg synthesis was marked by autophagical degradation of Vg synthetic and processing organelles.

Primary culture of canine prostate epithelial cells

Epithelial-cell enriched primary cultures were established from canine prostate by a collagenase digestion and selective attachment procedure. The epithelial cells in primary culture retained differentiated structure and function. The epithelial cells were attached to one another by tight junctions and desmosomes to form “lumenlike structures” that resemble the acini of the intact organ and appeared to contain typical protein synthetic organelles (1,2). The cultures contained significant levels of acid phosphatase and ornithine decarboxylase (2) and retained the ability to metabolize testosterone to dihydrotestosterone and other 5α-reduced metabolites (2–4).

Ultrastructural localization of carcinoembryonic antigen in normal intestine and colon cancer: abnormal distribution of CEA on the surfaces of colon cancer cells.

The distribution of carcinoembryonic antigen (CEA) in normal small intestine, normal colon, and colon cancer of humans was determined immunocytochemically by the peroxidase-labeled antibody method at the light and electron microscopic levels. In the small intestine, CEA was found in protein synthetic organelles, in the mucus, on the microvilli of goblet cells, and on some microvilli of columnar cells adjacent to goblet cells. In the normal colon, CEA was found in protein synthetic organelles of the fully differentiated columnar cells and goblet cells, as well as on the microvilli of the cells. In two well-differentiated colon cancers, the normal preferential surface expression of CEA on the microvilli was maintained, but in six poorly differentiated cancers, CEA was distributed equally over the entire cell surface. We conclude that CEA is a product of goblet cells in the small intestine, columnar and goblet cells in the colon, and colonic cancer cells. CEA on the surfaces of the normal epithelial cells is expressed in a polar manner. This polarity is lacking in undifferentiated neoplastic colon cells, which suggests that failure to establish or maintain the polar expression of normal cell-surface glycoproteins is a characteristic of the neoplastic cells.

Intracellular dynamics in pituitary mammotropes throughout the rat estrous cycle. II. Changes in synthetic and secretory organelles.

The organellar dynamics within mammotropes (prolactin secreting cells) of the anterior pituitary were examined using morphometry throughout the four-day rat estrous cycle. Two predominant periods of maximal organellar activity were found. The first period, which occurred during proestrus, resulted in two peaks of serum PRL at 6 pm and 12 m proestrus, while the second occurred during middiestrus-2 and resulted in an increase of pituitary PRL, but not a major serum PRL peak. The mitochondrial volume rose prior to that of other organelles during early proestrus, rising 110% from 4 am late diestrus-2 to 6 pm proestrus. However, the number of mitochondria per cell remained constant throughout the cycle. The volumes of rough endoplasmic reticulum (RER) and Golgi complex reached maximal proportions at 8 pm and 12 m proestrus, respectively. The RER volume was 153% greater than at 4 am late diestrus-2, while the Golgi complex had increased by 200%. We suggest that changes in the RER and Golgi complex volumes were the result of two processes: the synthesis of new membrane and the swelling of existing complexes. This study further substantiated that the serum peak of PRL at 6 pm proestrus is the result of stored mature granules being released, whereas the PRL peak at 12 m proestrus is due to the immediate release of hormone without any storage.

Development of lamellar bodies and subsurface cisterns in pyramidal cells and neuroblasts of hamster cerebral cortex

In pyramidal cells of hamster frontal cortex lamellar bodies and subsurface cisterns sequentially occurred during development from newborn to three months of age. Neither of these two specializations of the rough endoplasmic reticulum was seen in neurons of the newborn. The first specialization that we observed was the subsurface cistern, which appeared at five days and showed a significant increase both in frequency and in length throughout development. The lamellar body was first seen at ten days of age. This specialization showed a peaking of frequency, length, and number of cisterns per body at 15 days, which subsequently decreased gradually to 3-month-old levels. The occurrence of lamellar body-subsurface cistern complexes increased with age. We suggest that the lamellar body may be an ER specialization that is involved in an increased and/or stage-specific protein synthesis in the young prior to the final maturation of the usual neuronal protein synthetic organelles, and that in the 3-month-old neurons, the lamellar body may be involved in modifying, storing or transporting metabolites received from the neuropil components via the subsurface cisterns. The subsurface cistern, on the other hand, by virtue of its location subjacent to the neuronal plasma membrane and of its increased frequency from birth to maturation, may be involved in the exchange of metabolites and nonsynaptic forms of communication at all ages.

Ultrastructural and Functional Correlates of Increased Luteinizing Hormone Synthesis and Secretion in Castrated Male Mice*

AbstractThe changes in the ultrastructure of gonadotrops and in the plasma levels of LH were studied three, five, seven, ten, twenty and forty days after castration in adult male mice. Gonadotrops in sham operated animals contained numerous granules and moderately developed synthetic organelles. Castration induced mobilization of the secretory granules at three days, and degranulation of gonadotrops and a hypertrophy of the synthetic organelles at seven days. By ten days after castration gonadotrops were greatly enlarged, while in addition at forty days they frequently contained large cytoplasmic vesicles filled with lipid‐like material. These changes were paralleled by an initial three fold increase in serum LH three days after castration, and a further ten fold increase in the levels of the hormone forty days after castration. In conclusion, the castration‐induced morphologic changes in gonadotrops correlate well with increased release of LH. The subtle differences in the control of timing of LH secretion in mice and rats are discussed. A trans‐cytoplasmic route for rapid transport of gonadotropic hormones in the mouse is postulated, and the significance of cytoplasmic vesicles in the castrate discussed.

Uptake of protein by cultured human trophoblast cells

The uptake of peroxidase by cultured human trophoblast-cells was monitored ultrastructurally. There was no apparent effect on the distribution of peroxidase caused by treatment at 4 °C, with KCN or with IgG. Pinocytic channels penetrate deep into the perinuclear cytoplasm and may act to allow pinocytosis to occur within layers of microfilaments which might otherwise prevent pinosome access to the majority of the synthetic organelles.

The thyroid gland of the woodchuck, Marmota monax: a morphological study of seasonal variations in the follicular cells.

The morphology of the thyroid gland of the woodchuck, Marmota monax, was studied during the four seasons of the year. In the spring the thyroid is extremely heterogenous in appearance. Some follicular cells appear quite active. They contain a well defined Golgi apparatus, abundant large colloid droplets and pseudopodia but few, if any, apical vesicles. Other less active cells have poorly defined rough surfaced endoplasmic reticulum and lack a well developed Golgi apparatus. They do not contain apical vesicles or colloid droplets. Summer thyroids have uniformly small follicles which are lined by high cuboidal cells containing numerous mitochondria, apical vesicles, abundant rough surfaced endoplasmic reticulum, and lipid droplets but few colloid droplets. There is extensive lateral and basal infolding of the cytoplasmic membranes in these cells. In the fall and winter the follicles are larger than in the summer and contain more colloid. Numerous heterogeneous dense bodies appear in the cytoplasm of the follicular cells in the fall and increase in number in the winter when there is an obvious sparsity of such glycoprotein synthetic organelles as Golgi apparatus and rough surfaced endoplasmic reticulum. These morphologic changes are compared with previous studies of thyroid structure and function in other animals and are correlated with the seasonal physiologic activities of the woodchuck.

Localization of Leukocyte Alkaline Phosphatase in Human Neutrophils

The enzymes of blood and marrow neutrophils can be used to aid in the determination of the cell’s maturity. The enzyme marker which signals the production of secondary granules, leukocyte alkaline phosphatase (LAP), was found to be inactivated by aldehyde fixation, but minimal fixation of cells gave adequate marphological preservation and good enzyme activity. Notably, LAP activity was found to be present in neutrophils from the marrow myelocyte stage to the blood neutrophil stage, and high levels were found in the synthetic organelles of some circulating matureneutrophils. These observations at the electron microscopic level confirm the classical light microscopic histochemical findings.

Keratinization of the reptilian epidermis: An ultrastructural study of the turtle skin

The turtle epidermis was studied in an effort to obtain information about differentiation products and sequential events leading to the formation of the horny layer. Reproductive basal cells contain many ribosomes, and both granular and agranular endoplasmic reticulum. Filaments are relatively few; lipid droplets and glycogen particles appear in a moderate amount. Differentiating cells are filled with synthetic organelles, lipid droplets, mucous granules, and vesicular bodies. Mucous granules reveal a variable internal structure, and they are displaced toward the cell periphery. Ultimately, mucus is discharged into the intercellular space. Vesicular bodies contain several small vesicles and a peculiar disklike component. When the cells enter the transformation stage, the plasma membrane thickens and the synthetic organelles disintegrate. The horny cells are filled with loosely packed filaments, a relatively translucent matrix, and lipid. The keratinization process is characterized by comparing these features to those seen in amphibian, avian, and mammalian epidermis.

Keratinization of the avian epidermis: An ultrastructural study of the newborn chick skin

The newborn chick skin was studied in the light and electron microscopes in an effort to obtain information about the differentiation products of epidermal cells and sequential events which lead to the formation of the horny layer. Filaments are relatively few in both basal and differentiating cells. The cytoplasm undergoes compartmentalization during cell differentiation, and specific products are formed sequentially within segregated areas. In the cortical part of the cytoplasm a fine filamentous network appears upon which keratohyalin is later deposited. In the central part of the cytoplasm numerous large lipid droplets are formed by participation of an agranular reticulum and the Golgi system. Many multigranular bodies are also formed which contain several lamellated granules. When the cells enter the horny stage, the nucleus and the synthetic organelles are decomposed, the plasma membrane thickens, and the cell content consists of lipid surrounded by a fibrous-amorphous mass. These observations indicate that the pathway of differentiation the chick epidermal cells follow is different from that seen in mammals, and the protective horny cells are both structurally and chemically different from those of other vertebrates.