Distribution Of Cell Organelles Research Articles

Three-dimensional ultrastructural organization of the ommatidium of the minute parasitoid wasp Trichogramma evanescens

Existing information on insect compound eyes is mainly limited to two-dimensional information derived from histological or ultrathin sections. These allow a basic description of eye morphology, but are limited in z-axis resolution because of the section thickness or intervals between sections, so that accurate volumetric information cannot be generated. Here we use serial-sectioning transmission electron microscopy to present a 3-D reconstruction at ultrastructural level of a complete ommatidium of a miniaturized insect compound eye. Besides the general presentation of the three dimensional arrangement of the different cell types within the ommatidium, the reconstruction allowed volumetric measurements and numerical analyses to be undertaken, revealing new insights into the number, size and distribution of cell organelles in insect ommatidia. Morphological features that can be related to miniaturization, namely the dimensions and displacement of nuclei, reduction of average pigment granule volume and loss of pigment granules in the terminals of the cone cells, the impact of metabolic activity of cell types on miniaturization, as well as maintenance of rhabdomere volume and limits to its miniaturization, are all discussed.

Comparative ultrastructural analysis of diestrous and anestrous canine Grade 1 cumulus-oocyte complexes

The objective of the present study was to characterize, by means of transmission electron microscopy, immature Grade 1 cumulus-oocyte complexes (COCs) obtained from ovaries collected from bitches at diestrus and anestrus, after routine ovariohysterectomy. Cumulus-oocyte complexes were recovered after slicing the ovarian cortex and Grade 1 COCs were selected and prepared for transmission electron microscopy. All oocytes were at germinal vesicle stage in two different configurations. In 29 out of 37 COCs, oocytes presented a central or eccentric located nucleus (GVc), frequently containing a reticulated nucleolus, with a predominance of profound follicular cell processes (FCP), abundant endoplasmic reticulum (ER) and a moderated number of lipid droplets. In eight out of 37 COCs, oocytes had a peripheral located nucleus (GVp) containing small compact nucleolus, a thin perivitelline space, both superficial and profound FCP, moderate ER content and abundant lipid droplets. A higher ( p < 0.05) proportion of GVp was found in oocytes collected in diestrus (36.8% – 7 out of 19) than in anestrus (5.6% – 1 out of 18). In addition, distinct ultrastructure characteristics among GVc associated with estrous phase were noted. Furthermore, a number of structures, some of which had not been reported before, were present in canine prophase I oocytes at variable frequencies. The evident variation in the presence, quantity and distribution of cell organelles in canine immature Grade 1 oocytes is discussed in relation to the biological phase of the oocyte and the reproductive stage of the donor bitch.

A new type of microtubular cytoskeleton in microsporogenesis of Lavatera thuringiaca L.

In Lavatera thuringiaca, kariokinesis and simultaneous cytokinesis during the meiotic division of microsporogenesis follow a procedure similar to that which takes place in the majority of members of the class Angiospermae. However, chondriokinesis occurs in a unique way found only in species from the family Malvaceae. Chondriokinesis in such species is well documented, but the relationship between the tubulin cytoskeleton and rearrangement of cell organelles during meiosis in L. thuringiaca has not been precisely defined so far. In this study, the microtubular cytoskeleton was investigated in dividing microsporocytes of L. thuringiaca by immunofluorescence. The meiotic stages and positions of cell organelles were identified by staining with 4',6-diamidino-2-phenylindole. We observed that, during prophase I and II, changes in microtubular cytoskeleton configurations have unique features, which have not been described for other plant species. At the end of prophase I, organelles (mostly plastids and mitochondria) form a compact envelope around the nucleus, and the subsequent phases of kariokinesis take place within this arrangement. At this point of cell division, microtubules surround the organelle envelope and separate it from the peripheral cytoplasm, which is devoid of plastids and mitochondria. In telophase I, two newly formed nuclei are tightly surrounded by the cell organelle envelopes, and these are separated by the phragmoplast. Later, when the phragmoplast disappears, cell organelles still surround the nuclei but also move a little, starting to occupy the place of the disappearing phragmoplast. After the breakup of tetrads, the radial microtubule system is well developed, and cell organelles can still be observed as a dense envelope around the nuclei. At a very late stage of sporoderm development, the radial microtubule system disappears, and cell organelles become gradually scattered in the cytoplasm of the microspores. Using colchicines, specific inhibitors of microtubule formation, we investigated the relationship between the tubulin cytoskeleton and the distribution of cell organelles. Our analysis demonstrates that impairment of microtubule organization, which constitutes only a single component of the cytoskeleton, is enough to disturb typical chondriokinesis in L. thuringiaca. This indicates that microtubules (independent of microfilaments) are responsible for the reorganization of cell organelles during meiotic division.

Ultrastructural changes in the midgut epithelium of the first larva of Allacma fusca (Insecta, Collembola, Symphypleona)

Abstract. In the newly hatched larva in Allacma fusca, the midgut epithelium was fully developed and formed by flattened epithelial cells surrounding the yolk mass in the midgut lumen. Immediately after hatching, the first larva began to feed; the migut lumen was filled with the yolk mass and food (mainly algae). Regenerative cells typical of the developing midgut epithelium of many insects were not observed. Initially, midgut cells of the larva were cuboidal but became columnar in shape with distinct regionalization in the distribution of cell organelles. Furthermore, urospherites appeared in the midgut cell cytoplasm, i.e., structures characteristic for the midgut epithelium of insects having no Malpighian tubules. As a result, cells with the capacity for digestion, absorption, and excretion were observed to be completely formed in the first larval stage.

Three-dimensional phase-contrast imaging of single floating cells

A three-dimensional phase-contrast imaging technique that does not involve fluorescent labeling has been developed for observing floating cells. In this method, a single floating cell is made to rotate and images are acquired at several orientations of the cell using a phase-contrast microscope. From these two-dimensional phase-contrast images, three-dimensional cross-sectional images are obtained using the conventional computed tomography algorithm. This proposed method enabled successful rotation of a floating cell (a breast cancer cell line) and reconstruction of three-dimensional phase-contrast images. In these reconstructed three-dimensional images, the distribution of cell organelles is obtained and the cell nucleus is clearly distinguishable.

Maturation of Three Kinds of Keratin Networks in the Absorptive Cells of Rabbit Duodenum

Keratins (Ks) expressed in the absorptive cells of rabbit duodenal epithelium were studied immunohistochemically and immunoelectron microscopically. These keratins were classified into three groups based on their distribution: keratins forming an apex network just under the terminal web, those forming a Golgi-associated network surrounding the Golgi apparatus, and those forming an entire cytoplasmic network. The apex network was composed of K5/K18 keratin filaments. The Golgi-associated network at first consisted of K8/K14 keratin filaments alone. When the cell migrated out of the crypt to the mid-villus, actin and K7/K17 keratin filaments successively entered this network. The entire cytoplasmic network was detected at the villus base, and consisted of K7/K17 keratin filaments. Thereafter, K5/K18 keratin filaments entered this network during migration of the cell. The apex network may serve to maintain cell-cell contact, since its filaments are tightly anchored to desmosomes. The Golgi-associated network may be involved in the maintenance of the complex structure of the Golgi apparatus, since its filaments constitute a three-dimensional network around the organelle. The entire cytoplasmic network may play a major role in the maintenance of cell structure and the distribution of cell organelles.

Significance of the cytoskeleton for cytoplasmic organization and cell organelle dynamics in epithelial cells of fresh-water sponges

The cytoskeleton in epithelial cells ofSpongilla lacustris is constructed of microtubules radiating from the nuclear region and terminating at the cell periphery as well as microfilaments forming a cortical layer beneath the plasma membrane and distinct fibers in the cytoplasmic matrix. Single frame analysis and in vivo labeling of mitochondria with Rh 123, endosomes or lysosomes with TRITC-BSA, endoplasmic reticulum (ER) with DiOC6 (3) and dictyosomes with C6-NBD-ceramide points to the microtubular system as a candidate for controlled cytoplasmic organization and active transport of these cell organelles. In epithelial cells with an intact microtubular system, mitochondria and endosomes or lysosomes show a regular shuttle movement between the nucleus and the cell periphery with a velocity of 1.3–1.4 μm/s; the ER forms a more or less dynamic two-dimensional network in the entire cytoplasmic matrix, and dictyosomes are arranged in a ring-like manner around the nucleus. In epithelial cells treated with colchicine or colcemid, mitochondria and endosomes or lysosomes gather in the perinuclear region and become immobile; the ER accumulates near the cell center, whereas most dictyosomes distribute randomly over the whole cytoplasm. Transformation of the microfilament system with cytochalasin D has no influence on cell organelle distribution and dynamics but impedes cell locomotion and cell surface activities.

Subcellular fractionation of rainbow trout gonads with emphasis on microsomal enzymes involved in steroid metabolism.

Rainbow trout gonads were subfractionated by differential centrifugation with emphasis on obtaining preparations suitable for the study of steroid-metabolizing enzymes. A fractionation scheme was evaluated for the mature testis and for 3 ovarian developmental stages. The distribution of cell organelles among the fractions was determined using enzyme-markers and electron microscopy. The fractionation scheme was found to be suitable for separating mitochondria and microsomes which were recovered at similar yields to those that had been reported for other extraheptic fish tissues. Fractionation of the mature ovary was fraught with problems probably because a large yolk protein cytosole fraction interfered with the recovery of microsomes. However, no difference in the specific activity of microsomal NADPH-cytochrome c-reductase between the various organ preparations was evident. The testis microsomes contained detectable amounts of cytochrome P450, whereas its content in the various ovary microsomes was too low to be detected. Progesterone 17 alpha-hydroxylase was detected in microsomes from testes and early developing ovaries, and microsomal aromatase activity was present in microsomes from early developing, mature and postovulatory ovaries. Furthermore, the testis microsomes contained a highly active UDP glucuronosyltransferase with testosterone used as a substrate.

Computer-aided serial section reconstruction of nerve endings on the outer hair cells of the cochlea. Semithin sections vs. ultrathin sections.

Afferent and efferent nerve endings on several outer hair cells in different turns and rows of the guinea pig cochlea were three-dimensionally reconstructed from serial semithin sections or ultrathin sections by means of a new computer system. In the basal turn, a single afferent ending was sometimes isolated from the others and surrounded by efferent endings, suggesting that this type of afferent ending may have properties different from the others. The advantages and disadvantages of semithin sections and ultrathin sections in computer-aided reconstruction were discussed and it was concluded that the semithin section technique will be useful in reconstructions of specimens from a wide range, whereas the ultrathin section technique will be better for reproducing fine structures such as the distribution of cell organelles as well as synaptic membrane specializations.

The usefulness of the high voltage electron microscope in biomedical ultrastructure analysis.

We now have the tools to quantitate and correctly interpret the size, shape, and distribution of organelles in cells. It appears likely that the results will require some changes in some basic assumptions of ultrastructural cytology. This should also result in some new biochemical hypotheses about control of cell metabolism.

Feinstrukturelle Untersuchungen an einem endokrin aktiven Carcinom der Nebennierenrinde

The fine structure of a carcinoma of the human adrenal cortex clinically displaying Cushing’s disease was studied by electron microscopy. Besides irregular shapes and sizes of cells with deep invaginations and cytoplasmatic pseudoinclusions of their nuclei, the variability in distribution of cell organelles was remarkable. In comparison to animal experiments the organelles revealed evidence of increased endocrine activity demonstrated by an extensive development of rough and smooth endoplasmic reticulum, number of mitochondria, and Golgi apparatus; moreover lipid bodies were infrequent. By means of serial sectioning a direct connection between perinuclear space, rough and smooth reticulum, and interior of the Golgi apparatus could be traced. Most mitochondria exhibited a cristae type, several showed a gigantic size with a dense, finely granulated matrix. In addition there were septate interconnections between cellular membranes, membranes of the rough endoplasmic reticulum and cristae and mitochondrial membranes.

Observations on the structure of the protonema of Adiantum capillus-veneris L. undergoing cell division following white-light irradiation

The structure and distribution of cell organelles were observed in the gametophytes of Adiantum capillus-veneris L. undergoing the first cell division induced by white-light irradiation. Under continuous red light, the nucleus is spindle-shaped, encased in a sheath of chloroplasts, and located some distance back from the tip. The apical pole of the nucleus has an invagination which contains microtubules. Two types of chloroplasts, both of which have starch and prolamellar bodies, may be distinguished. One is cigar-shaped and may be "anchored" at the cell membrane. The other is smaller, and more pleiomorphic. Two populations of microtubules may be distinguished within the cortical cytoplasm, one set aligned parallel to the long axis of the cell, the other set aligned circumferentially around the cell at the region of the dome except for the extreme apex. Some of these microtubules do not run for long distances. If cell division is induced by irradiation of the gametophytes with white light the vacuolation and swelling of the tip region begin at least 2 h after the induction and continue till 8-10 h, by which time the nucleus has reached the neck of the protonema. Very elongated and rather abnormal forms of mitochondria were noted during this period. During cell division, mitochondria aggregated at the poles of the spindle and at the equatorial plane of the spindle margin. After cytokinesis the vacuole system becomes fragmented and is redistributed uniformly throughout the tip cell, the daughter nucleus rounds up and becomes surrounded by oil droplets.

Effects of colchicine on axonal transport and ultrastructure of the hypothalamo-neurohypophyseal system of the rat

The effect of colchicine on the transport of proteins in the hypothalamo-neurohypophyseal tract of the rat was studied after injection of (35S) cysteine into the supraoptic nucleus (SON) region. Colchicine, dissolved in distilled water and administered subarachnoidally, inhibited the axonal transport of labelled proteins into the neurohypophysis: the radioactivity that was recovered in neurohypophyseal TCA precipitable material was markedly decreased and hardly any radioactivity was found in the neurohypophyseal proteins which were separated by polyacrylamide gel disc electrophoresis. As revealed by electron microscopy the SON cell bodies showed marked changes after treatment with colchicine: a deeply folded nucleolemma; a pronounced, granular nucleolus; a dispersed chromatin; a zonal distribution of cell organelles with mitochondria and lysosomes accumulated at the periphery, crowded ribosomes, often arranged as polyribosomes and richly branching short profiles of endoplasmic reticulum filled with filamentous material forming an inner perinuclear zone separated by enlarged Golgi complexes. The profiles of elongated Herring bodies in the infundibulum were increased. The axon terminals were filled with heavily osmiophilic neurosecretory granules. The neurofilaments were slightly or moderately increased in number. No apparent changes were observed with regard to the neurotubuli in the SON neurons. The glial cells of the supraopticoneurohypophyseal tract showed reactive changes with a proliferation of filamentous elements. The biochemical and ultrastructural findings are discussed especially with respect to the mechanisms of transport and release of neurosecretory granules.