THE EFFECTS OF ENUCLEATION ON THE CYTOPLASMIC MEMBRANES OF AMOEBA PROTEUS

The dependence of cytoplasmic membranes upon the nucleus was studied by examining enucleated amebae with the electron microscope at intervals up to 1 wk after enucleation. Amebae were cut into two approximately equal parts, and the fine structure of the enucleated portions was compared with that of the nucleated parts and starved whole cells which had been maintained under the same conditions. Golgi bodies were diminished in size 1 day after enucleation and were not detected in cells enucleated for more than 2 days. The endoplasmic reticulum of enucleated cells appeared to increase in amount and underwent changes in its morphology. The sparsely scattered short tubules of granular endoplasmic reticulum present in unmanipulated amebae from stock cultures were replaced in 1–3-day enucleates by long narrow cisternae. In 3–7-day enucleates, similar cisternae of granular endoplasmic reticulum encircled areas of cytoplasm partially or completely. It was estimated that in most cases hundreds of these areas encircled by two rough membranes were formed per enucleated cell. The number of ribosomes studding the surface of the endoplasmic reticulum decreased progressively with time after enucleation. In contrast, the membranes of nucleated parts and starved whole cells did not undergo these changes. The possible identification of membrane-encircled areas as cytolysomes and their mode of formation are considered. Implications of the observations regarding nuclear regulation of the form of the Golgi apparatus and the endoplasmic reticulum are discussed.     

Influence of inhibitors of energy metabolism on the formation of Golgi bodies in amebae

Metabolic requirements for the formation of Golgi bodies were studied by exposing renucleated amebae to different metabolic inhibitors. Golgi bodies decline in size and number in enucleated amebae. They are regenerated and increase rapidly in size and number following the transplantation of a new nucleus into cells previously enucleated for 5 days. The size and number of Golgi bodies formed in untreated renucleates was compared with those formed in the presence of an inhibitor in samples of cells fixed 6 and 24 h after operation. Cyanide and dinitrophenol were used to inhibit mitochondrial oxidative phosphorylation, and fluoride was utilized as an inhibitor of glycolysis. The formation of Golgi bodies was decreased in the presence of cyanide and dinitrophenol. This inhibition of Golgi formation was reversible after 6 h in the inhibitor by removing the cells to normal ameba medium. In most experiments, fluoride was less effective in suppressing the formation of Golgi bodies than the inhibitors of oxidative phosphorylation. The results indicate that the formation of Golgi bodies is an energy-requiring process. They suggest that oxidative phosphorylation carried out in mitochondria is an important source of the necessary high energy compounds. Data on the survival of unmanipulated amebae in these inhibitors is also recorded.     

Enzyme synthesis and potential during induction synchrony in the fission yeast Schizosaccharomyces pombe

The fine structure of L cells is described at 30 min and 24 h after enucleation by centrifugation in cytochalasin B. The morphology of the 30-min enucleates is the same as that of the cytoplasm of nucleated cells. Centrioles, a normal Golgi apparatus, endoplasmic reticulum, mitochondria, microtubules, and some microfilaments, are present in enucleates. At 24 h after enucleation, the enucleates are extensively vacuolated. The cisternae of the Golgi apparatus are extremely dilated, and the granular ER is sometimes dilated. Microtubules, and, in particular, microfilaments, are still abundant. Nuclei removed from cells by enucleation in cytochalasin B are surrounded by a thin shell of cytoplasm containing numerous ribosomes, an occasional mitochondrion, a few pieces of endoplasmic reticulum, and an enclosing plasma membrane. Continuities between the nuclear envelope and the ER are particularly frequent. These nuclei possesses a normal fine structure.     

Cytochemical and fine structural analysis of oogenesis in the gastropod, Ilyanassa obsoleta

An analysis of differentiating oocytes of the gastropod, Ilyanassa obsoleta, has been made by techniques of light and electron microscopy. Early previtellogenic oocytes are limited by a smooth surfaced oolemma and are associated with each other by maculae adhaerentes. Previtellogenic oocytes are also distinguished by a large nucleus containing randomly dispersed aggregates of chromatin. Within the ooplasm are Golgi complexes, mitochondria and a few cisternae of the rough endoplasmic reticulum. When vitellogenesis begins, the oolemma becomes morphologically specialized by the formation of microvilli. One also notices an increase in the number of organelles and inclusions such as lipid droplets. During vitellogenesis there is a dilation of the saccules of the Golgi complexes and cisternae of the endoplasmic reticulum. Associated with the Golgi complexes are small protein-carbohydrate yolk precursors encompassed by a membrane. These increase in size by fusing with each other. The “mature” yolk body is a membrane-bounded structure with a central striated core and a granular periphery. At maturity a major portion of the ooplasmic constituents such as as mitochondria and lipid droplets occupy the animal region while the bulk of the population of yolk bodies are situated in the vegetal hemisphere. The follicle cells incompletely encompass the developing oocyte. In addition to the regularly occurring organelles, follicle cells are characterized by the presence of large quantities of rough endoplasmic reticulum and Golgi complexes whose saccules are filled with a dense substance. Associated with the Golgi saccules are secretory droplets of varied size. Amongst the differentiating oocytes and follicle cells are Leydig cells. These cells are characterized by a large vacuole containing glycogen. A possible function for the follicle and Leydig cells is discussed.     

The trans Golgi face in rat small intestinal absorptive cells

In the small intestine cell differentiation from immature crypt cells to mature absorptive cells localized along the villi is accompanied by alterations in the organization of the trans Golgi side. In immature crypt cells the transmost Golgi cisterna is usually located closely adjacent to the other cisternae thus being a component of the stack. Concomitantly with cell differentiation the transmost cisterna of an increasing number of Golgi stacks sets off from the other cisternae being then located at various distances to the stacks. This transmost cisterna has, as in several other cell types, been interpreted as "GERL" (Golgi associated endoplasmic reticulum lysosomes [20, 28]) and thus, has been postulated to represent a specialized region of the endoplasmic reticulum. Our results, however, have shown that the cytochemical staining pattern which has been used as a basis for the differentiation of GERL from Golgi components is not present in crypt cells nor in mature absorptive cells of the proximal small intestine: identical cisternae react for thiamine pyrophosphatase, inosine diphosphatase, and acid phosphatase. Thiamine pyrophosphatase and inosine diphosphatase--enzymes characteristic for Golgi cisternae--are apparent over transmost cisternae defined as GERL, too, and in addition, acid phosphatase--postulated as GERL-marker--is demonstrable over stacked Golgi cisternae. This overlapping cytochemical reaction, as well as the alterations during cell differentiation, indicate that those structures which have been described as GERL are to be interpreted as Golgi components rather than as endoplasmic reticulum. On the other hand, endoplasmic reticulum is a constant component of the trans Golgi face in undifferentiated crypt-base cells and in maturing cells of the crypt-top region. From its localization closely adjacent to trans Golgi cisternae it may be termed "Golgi-associated endoplasmic reticulum"; however, these cisternae of endoplasmic reticulum are constantly devoid of acid phosphatase. No indications exist for continuities with the thiamine pyrophosphatase-, inosine diphosphatase-, and acid phosphatase-positive transmost Golgi cisternae, and for an engagement in production of lysosomes.     

Substructure of cisternal organelles of neuronal perikarya in immature rat brains revealed by quick-freeze and deep-etch techniques

Summary Membrane-bounded organelles possessing cisternae, i.e., rough endoplasmic reticulum and Golgi apparatus, in immature rat central neurons were examined by quick-freeze and deep-etch techniques to see how their intracisternal structures are organized and how ribosomes are associated with the membrane of the endoplasmic reticulum. Cisternae of endoplasmic reticulum, 60–100 nm wide, were bridged with randomly-distributed strands (trabecular strands, 12.5 nm in mean diameter). Luminal surfaces of cisternae of the endoplasmic reticulum were decorated with various-sized globular particles, some as small as intramembrane particles, and others as large as granules formed by soluble proteins seen in the cytoplasm. A closer examination revealed much thinner strands (3.3. nm in mean diameter). Such thin strands were short, usually winding toward the luminal surface, and sometimes touching the luminal surface with one end. Ribosomes appeared to be embedded into the entire thickness of cross-fractured membranes of endoplasmic reticulum, that is, their internal portions appeared to be situated at almost the same level as the cisternal luminal surface. From the internal portion of ribosomes, single thin strands occasionally protruded into the lumen, suggesting that these thin strands were newly synthesized polypeptides. A horizontal separation within ribosomes appeared to occur at the same level as the hydrophobic middle of the membrane of the endoplasmic reticulum. Interiors of the Golgi apparatus cisternae, which were much narrower than cisternae of endoplasmic reticulum, were similarly bridged with trabecular strands, but the Golgi trabecular strands were thinner and more frequent. Their cisternal lumina were also dotted with globular particles. No identifiable profiles corresponding to the thin strands in the endoplasmic reticulum were observed. Golgi cisternae showed a heterogeneous distribution of membrane granularity; the membrane in narrow cisternal space was granule-rich, while that in expanded space was granule-poor, suggesting a functional compartmentalization of the Golgi cisternae.     

Effects of pinealectomy on the ultrastructure of the golden hamster parathyroid gland

Ultrastructural changes of the parathyroid glands of pinealectomized golden hamsters were investigated. The main changes in the parathyroid glands 1 hour and 1 day after pinealectomy compared with the control and sham-operated groups were an increase of the Golgi complexes, cisternae of the granular endoplasmic reticulum and large vacuolar bodies. In addition, many chief cells contained numerous prosecretory granules in the Golgi areas and many secretory granules in the peripheral cytoplasm. The morphology of the parathyroid glands 7 and 30 days after pinealectomy resembled that of the control parathyroid glands. These results suggest that pinealectomy affects the secretory activity of the parathyroid gland.     

The localization of endogenous peroxidase in the lacrimal gland of the rat during postnatal development. Electron microscope cytochemical and biochemical studies

The distribution of endogenous peroxidase activity in the lacrimal gland of the rat during postnatal development was investigated by electron microscope cytochemistry Peroxidase activity is first found 6 hr after birth in only a few acinar cells At this stage, reaction product fills only localized segments of the scant rough endoplasmic reticulum and of the perinuclear cisternae. Peroxidase activity thus develops asynchronously in a given cell as well as in the secretory cell population as a whole 2 days after birth, all cisternae of the rough endoplasmic reticulum of a peroxidase-positive cell contain reaction product, but the majority of the acinar cells is still negative During the next days, the number of peroxidase-positive cells and the amount of the rough endoplasmic reticulum increase rapidly. By 15 days postparturition, all secretory cells are peroxidase-positive. Reaction product is then found in all cisternae of the rough endoplasmic reticulum including the perinuclear cisternae, in smooth surface vesicles located mainly between the rough endoplasmic reticulum and the Golgi stacks, in condensing vacuoles, and in all secretory granules The Golgi cisternae rarely contain reaction product In total homogenates and in fractions of glandular tissue of adult rats, peroxidatic and catalatic activities are demonstrable. The microsomal fractions and the postmicrosomal supernatants were used to separate peroxidase from catalase by precipitation with ammonium sulfate, and the following parameters were determined: substrate (H₂O_2-) optimum (∼ 2.0 x 10^-4 M), pH-optimum (pH 6 5), temperature-optimum (42°C), and the absorption maximum (415 nm before and 425 nm after addition of H₂O₂) The same parameters were obtained from lacrimal fluid peroxidase. Both peroxidase from lacrimal gland and that from lacrimal fluid are almost completely inhibited by 10^-3 M aminotriazole and are possibly identical enzymes. Peroxidase is secreted into lacrimal fluid, which does not contain catalase.     

Ultrastructural changes in the liver of the sand lamprey,Lampetra reissneri,during sexual maturation

Ultrastructural changes of hepatocytes were examined in the sand lamprey,Lampetra reissneri, during various phases of the life cycle. In hepatocytes of ammocoetes, the rough endoplasmic reticulum was composed of short cisternae and the Golgi apparatus were scarcely developed, showing no sexual differences at this stage of life cycle. In hepatocytes of female lampreys at the metamorphic stages 4 to 5, the rough endoplasmic reticulum was developed to form long parallel cisternae and the Golgi apparatus were well-developed. The rough endoplasmic reticulum developed further to form stacks of long parallel cisternae extending over the cytoplasm in hepatocytes of females at the young adult stage, and became composed of both long parallel and vesicular cisternae in the cells of females at the adult stage. The Golgi apparatus were invariably welldeveloped in hepatocytes of young adult and adult females. No consipcuous development was observed in profiles of the rough endoplasmic reticulum and the Golgi apparatus in hepatocytes of males during and after metamorphosis. The ultrastructural changes of the rough endoplasmic reticulum and the Golgi apparatus observed in hepatocytes of female sand lampreys are considered to have an intimate relation to the activity of vitellogenin synthesis in the liver, and it is suggested that the hepatocytes begin to rapidly synthesize vitellogenin in the sand lamprey at the metamorphic stages 4 to 5.     

Effect of colchicine on the Golgi complex of rat pancreatic acinar cells

Colchicine administered to adult rats at a dosage of 0.5 mg/100 g of body weight effected a disorganization of the Golgi apparatus in pancreatic acinar cells. The results obtained after various periods of treatment (10 min to 6 h) showed (a) changes in all components of the Golgi complex, and (b) occurrence of large vacuoles that predominated in cytoplasmic areas outside the Golgi region. The alterations in Golgi stacks concerned elements of the proximal and distal side: (a) accumulation of transport vesicles, (b) formation of small, polymorphic secretion granules, and (c) alterations in the cytochemical localization of enzymes and reaction product after osmification. Transport vesicles accumulated and accompanied short, dilated cisternae, which lack mostly the reaction products of thiamine pyrophosphatase, inosine diphosphatase, and acid phosphatase, and osmium deposits after prolonged osmification. After 4 to 6 h of treatment, accumulated transport vesicles occupied extensive cellular areas; stacked cisternae were not demonstrable in these regions. The changes on the distal Golgi side included GERL elements: condensing vacuoles were diminished; they were substituted by small, polymorphic zymogen granules, which appeared to be formed by distal Golgi cisternae and by rigid lamellae. Unusually extended coated regions covered condensing vacuoles, rigid lamellae, and polymorphic secretion granules. A cytochemical distinction between Golgi components and GERL was possible neither in controls nor after colchicine treatment. The cytochemical alterations in Golgi components were demonstrable 20-30 min following administration of colchicine; at 45 min, initial morphological changes--augmentation of transport vesicles and formation of polymorphic zymogen granules--became apparent. 20 min after administration of colchicine, conspicuous groups of large vacuoles occurred. They were located mostly in distinct fields between cisternae of the endoplasmic reticulum, and were accompanied by small osmium--reactive vesicles. Stacked cisternae were not demonstrable in these fields. Vacuoles and vesicles were devoid of reaction products of thiamine pyrophosphatase, inosine diphosphatase, and acid phosphatase. The results provide evidence that formation of stacked Golgi cisternae is impaired after colchicine treatment. The colchicine--induced disintegration of the Golgi complex suggests a regulatory function of microtubules in the organization of the Golgi apparatus.     

Cytochemical localization of terminal N-acetyl-D-galactosamine residues in cellular compartments of intestinal goblet cells: implications for the topology of O-glycosylation

The O-linked oligosaccharides of mucin-type glycoproteins contain N- acetyl-D-galactosamine (GalNAc) that is not found in N-linked glycoproteins. Because Helix pomatia lectin interacts with terminal GalNAc, we used this lectin, bound to particles of colloidal gold, to localize such sugar residues in subcellular compartments of intestinal goblet cells. When thin sections of low temperature Lowicryl K4M embedded duodenum or colon were incubated with Helix pomatia lectin- gold complexes, no labeling could be detected over the cisternal space of the nuclear envelope and the rough endoplasmic reticulum. A uniform labeling was observed over the first and several subsequent cis Golgi cisternae and over the last (duodenal goblet cells) or the two last (colonic goblet cells) trans Golgi cisternae as well as forming and mature mucin droplets. However, essentially no labeling was detected over several cisternae in the central (medial) region of the Golgi apparatus. The results strongly suggest that core O-glycosylation takes place in cis Golgi cisternae but not in the rough endoplasmic reticulum. The heterogenous labeling for GalNAc residues in the Golgi apparatus is taken as evidence that termination of certain O- oligosaccharide chains by GalNAc occurs in trans Golgi cisternae.     

Intracellular vesicles involved in the transport of Semliki Forest virus membrane proteins to the cell surface.

The route of transport of Semliki Forest virus (SFV) membrane glycoproteins to the plasma membrane was studied using immunoperoxidase electron microscopy. SFV glycoproteins were localized in cultured BHK-21 fibroblasts infected with a temperature-sensitive mutant ts-1 of SFV, which shows a temperature-dependent, reversible defect in the transport of membrane glycoproteins to the cell surface. At 39 degrees C (restrictive temperature) the viral proteins were retained in the endoplasmic reticulum and the nuclear membrane. After shift of the infected cultures to 28 degrees C (permissive temperature) the proteins were synchronously transported to the Golgi complex. In the Golgi complex the labeled proteins were first (at 2.5 min) detected in large Golgi-associated vacuoles (GAV). Subsequently, i.e., at 5-30 min, the viral glycoproteins appeared in the cisternal stack: at 5 min the label was found in one or two of the proximal cisternae whereas at 15 or 30 min also the more distal cisternae were partially or uniformly labeled. At all time points examined after the temperature-shift, peroxidase label was found in 50 nm vesicles which were frequently coated. At 30 min, in addition to the 50 nm vesicles, larger 80 nm vesicles, which often had a cytoplasmic coat were labeled in the Golgi region. These results identify two major size classes of both coated and smooth vesicles which appear to function in the transport of the viral membrane proteins from the endoplasmic reticulum via distinct GAV and the stacked Golgi cisternae to the plasma membrane.     

Micromorphological Aspects of the Development of Rubella Virus in BHK-21 Cells

Sequential effects of rubella virus infection in BHK-21 cells were studied by electron microscopy of thin sections of control and infected cells, 2 to 7 days after infection. Vacuolization of cytoplasm in Golgi areas apparently preceded budding of virions from vacuole membranes and involvement of the endoplasmic reticulum. Newly formed endoplasmic reticulum cisternae encircled and segregated virionforming vacuoles together with other cellular elements. Large vacuolar complexes with numerous virus particles developed, and virus release from these areas occurred with disruption at the cell periphery. The viral particles, with a mean diameter of about 56 nm, consisted of an electron-dense core surrounded by a less dense capsid, enveloped by a typical unit membrane derived from the vacuole membrane.     

Associated membranes in spermatocytes of the backswimmer,Notonecta glauca L. (Heteroptera : Hydrocorisae)

In secondary spermatocytes of Notonecta glauca (Heteroptera : Hydrocorisae) associated membranes occur in a certain area of the cytoplasm near the nucleus. They consist of 2 separate endomembrane systems of different origins. One component comprises parts of extended endoplasmic cisternae, the other numerous vesicles of rather uniform size and shape derived from the Golgi apparatus and attached to the endoplasmic cisternae in a very regular array. Open connections or specialized contacts between the 2 systems do not exist. The close relationship, nevertheless, indicates a functional interdependence between the 2 partners, and suggests the division of the endoplasmic reticulum into domains with structural and functional diversity.     

Light and electron microscopic observations on the cervical epithelium of the rabbit: II

The endocervical epithelium of long-term ovariectomized rabbits treated for 1-10 days with 5 micrograms of estradiol benzoate every 12 hr has been studied by light and electron microscopy. In addition, morphometric data on ciliated and nonciliated cells of rabbits treated for 2, 6, and 10 days are compared to those on untreated ovariectomized, estrous, and ovulatory rabbits. The percentage of ciliated cells increases after ovariectomy to 76.3% and that of secretory cells decreases to 23.7% as compared to estrous controls. Treatment of ovariectomized rabbits with estradiol results in a gradual increase in ciliated and secretory cell area, height, and nuclear area. After 10 days of treatment, cell areas are significantly larger than those in the ovulatory or estrous controls; cell height and nuclear areas have returned to preovariectomized levels; and the percentages of ciliated and secretory cells have reached those of estrous levels. Estradiol stimulates mitotic division of secretory cells but affects ciliogenesis minimally. In ciliated cells, estradiol treatment results in a modest increase in polysomes and granular endoplasmic reticulum and in striking increases in the size of the Golgi complex and in the number of lipofuscin bodies as compared to those in the ovariectomized controls. In secretory cells, estradiol treatment brings about an increase in the numbers of polysomes, Golgi complexes, and cisternae of the granular endoplasmic reticulum, in the sizes of the nucleoli, and in the amount of euchromatin. Secretory granules appear in some cells after 2 days of estradiol stimulation and increase in number through 10 days of treatment. Perinuclear granules are more pleomorphic and heterogeneous in structure and more numerous in the 6- to 10-day-estradiol-treated than in ovulatory animals, and they may function as lysosomes degrading excess secretory product. Deep apical concavities of the secretory cells occur most often after 2 and 6 days of treatment.     

Stichosome ultrastructure of the fish nematode Capillaria pterophylli Heinze, 1933

The stichosome (posterior glandular esophagus) of Capillaria pterophylli Heinze, 1933 consists of large gland cells (stichocytes) and lumenal epithelium with cuticular lining. Both structures are enclosed in a reticulum of muscle cells. The stichocyte cytoplasm contains small cisternae of rough endoplasmic reticulum, Golgi complexes, one kind of electron dense secretory granules, mitochondria and a branching system of intracellular collecting ducts without filament bundles around them.     

Development of secretory activity in the long hyaline gland of the male migratory grasshopper,Melanoplus sanguinipes (Fabr.) (Orthoptera : Acrididae)

Changes in the ultrastructure of epithelial cells from long hyaline glands of male Melanoplus sanguinipes (Fabr.) (Orthoptera : Acrididae) have been examined during sexual maturation and after allatectomy. In newly emerged males, the long hyaline gland epithelium is composed of 1–3 cell layers. The cells contain almost no rough endoplasmic reticulum, inconspicuous Golgi complexes, and large numbers of free ribosomes and polysomes. Within 24 hr, the cells undergo considerable reorganization to form a 1-cell-thick layer. Changes in cytostructure include proliferation of the rough endoplasmic reticulum and the development of several elaborate Golgi complexes. The developing lumen contains a coarse fibrous material. By 3 days postemergence, columnar epithelial cells are clearly capable of considerable synthesis and export of secretory protein. Rough endoplasmic reticulum, and large, elaborate Golgi complexes are the major structural features of the cytoplasm. From day 3 to sexual maturity (day 7), no major ultrastructural changes occur, although massive accumulation of secretion in the lumen causes the epithelium to become cuboidal or flattened. Isoelectric focusing of soluble proteins from long hyaline gland secretions shows that maturing glands contain increasing numbers and quantities of secretory proteins.Allatectomy has minor effects on long hyaline gland ultrastructure. A reduction in the density of rough endoplasmic reticulum and ribosomes suggests that glands from operated males are metabolically less active. This is confirmed by qualitative and quantitative changes in the amount of secretion as revealed by isoelectric focusing. The observations are discussed in terms of the juvenile hormone control of long hyaline gland maturation.     

Immunohistochemical localization of albumin and in situ hybridization of albumin mRNA

Hepatocytes actively involved in albumin synthesis were identified by immunohistochemical method. In sections of perioidate-lysine-2 per cent (w/v) paraformaldehyde fixed normal rat liver, albumin was detected in all hepatocytes. At the ultrastructural level, albumin was localized in the rough endoplasmic reticulum and in Golgi complexes located near the nucleus in only a small subpopulation of hepatocytes, while all other hepatocytes contained albumin only in Golgi complexes located near the bile canaliculi. Stimulation of albumin synthesis by puromycin aminonucleoside-induced nephrosis resulted in an altered intracellular distribution of albumin at the light microscopic level. When examined at the ultrastructural level, albumin was localized in the rough endoplasmic reticulum as well as in Golgi complexes located near the nucleus in nearly all these hepatocytes. Hepatocytes with the potential to synthesize albumin were identified by in situ hybridization of albumin mRNA. In sections of 0.1 per cent (v/v) glutaraldehyde perfusion fixed normal rat liver, albumin mRNA was detected in the cytoplasm of only a few hepatocytes scattered throughout the lobule. Following stimulation of albumin synthesis by the induction of nephrosis, albumin mRNA was detected in the cytoplasm of the hepatocytes. The source of albumin in those hepatocytes which lacked albumin mRNA was identified in analbuminemic rats injected with rat albumin. At 6 h post injection, the light microscopic distribution of albumin in the liver of these animals was virtually indistinguishable from that in normal rat liver. At the ultrastructural level, injected albumin was localized in lysosomes and in Golgi complexes located near the bile canaliculi.     

Maintenance and regeneration of cytoplasmic organelles in hybrid amebae formed by nuclear transplantation

The fine structure of cytoplasmic organelles was studied in hybrid amebae that were formed by transplanting the nucleus from one kind of ameba into the cytoplasm of a different type of ameba. Four different species or strains of amebae were utilized; Amoeba proteus, A. discoides, A. dubia, and A. amazonas. The fine structure of A. discoides was indistinguishable from that of A. proteus, but A. dubia and A. amazonas had distinctive features. To determine if the fine structure of cytoplasmic organelles in hybrid cells is like that of the nuclear parent or the cytoplasmic parent, nuclei were transferred between A. proteus and A. amazonas, which differ in their cytoplasmic ultrastructure, especially in the morphology of mitochondria. The cytoplasm of these hybrids resembled most closely that of the cytoplasmic parent. The degree to which different heterologous nuclei are capable of maintaining normal cytoplasmic organization was then studied by replacing an A. proteus nucleus with a nucleus from one of the other kinds of amebae. An A. discoides nucleus maintained A. proteus cytoplasm for several weeks. A nucleus from A. dubia or A. amazonas was able to maintain A. proteus cytoplasm for a few days, but then the cytoplasm began to show ultrastructural changes characteristic of enucleated amebae. The ability of a heterologous nucleus to promote the regeneration of Golgi bodies and endoplasmic reticulum after their decline in the absence of the nucleus was tested by transplanting a heterologous nucleus into A. proteus cytoplasm that had been enucleate for 5 days. A. discoides was the most effective heterologous nucleus donor but was less successful than normal A. proteus. Insertion of a nucleus from either A. amazonas or A. dubia resulted in “reactivation” of the cytoplasm with extension of pseudopods and resumption of motility but little or no regeneration of cell organelles. Thus, the ability of a heterologous nucleus both to maintain and to regenerate normal features of cytoplasmic organelles varied with the type of heterologous nucleus and was related to the degree of morphological resemblance between the donor and recipient cells. The role of the nucleus in motility and its role in regeneration of cytoplasmic organelles were dissociated from one another in the case of some hybrid renucleates.     

Contribution of the golgi Complex—Endoplasmic reticulum system during spermiogenesis in three species of phytophagous bugs (Hemiptera : Pentatomidae)

The participation of the Golgi complex—endoplasmic reticulum system during spermiogenesis in 3 species of phytophagous bugs (Acrosternum aseadum, Euchistus heros and Nezara viridula) were analysed at the ultrastructural level, after postfixation with osmium tetroxide\potassium iodide. Intense staining was found in the nuclear envelope, endoplasmic reticulum cisternae, Golgi complex, and in a meshwork of tubules scattered throughout the cytoplasm. It is shown that these compartments present a reducing environment. The presence of this kind of staining on the spermatid suggests an important participation of these structures on the differentiation process of this cell.