Golgi apparatus: influence on cell surfaces

Alteration of intracellular traffic by monensin; mechanism, specificity and relationship to toxicity

Monensin, a monovalent ion-selective ionophore, facilitates the transmembrane exchange of principally sodium ions for protons. The outer surface of the ionophore-ion complex is composed largely of nonpolar hydrocarbon, which imparts a high solubility to the complexes in nonpolar solvents. In biological systems, these complexes are freely soluble in the lipid components of membranes and, presumably, diffuse or shuttle through the membranes from one aqueous membrane interface to the other. The net effect for monensin is a trans-membrane exchange of sodium ions for protons. However, the interaction of an ionophore with biological membranes, and its ionophoric expression, is highly dependent on the biochemical configuration of the membrane itself. One apparent consequence of this exchange is the neutralization of acidic intracellular compartments such as the trans Golgi apparatus cisternae and associated elements, lysosomes, and certain endosomes. This is accompanied by a disruption of trans Golgi apparatus cisternae and of lysosome and acidic endosome function. At the same time, Golgi apparatus cisternae appear to swell, presumably due to osmotic uptake of water resulting from the inward movement of ions. Monensin effects on Golgi apparatus are observed in cells from a wide range of plant and animal species. The action of monensin is most often exerted on the trans half of the stacked cisternae, often near the point of exit of secretory vesicles at the trans face of the stacked cisternae, or, especially at low monensin concentrations or short exposure times, near the middle of the stacked cisternae. The effects of monensin are quite rapid in both animal and plant cells; i.e., changes in Golgi apparatus may be observed after only 2-5 min of exposure. It is implicit in these observations that the uptake of osmotically active cations is accompanied by a concomitant efflux of H+ and that a net influx of protons would be required to sustain the ionic exchange long enough to account for the swelling of cisternae observed in electron micrographs. In the Golgi apparatus, late processing events such as terminal glycosylation and proteolytic cleavages are most susceptible to inhibition by monensin. Yet, many incompletely processed molecules may still be secreted via yet poorly understood mechanisms that appear to bypass the Golgi apparatus. In endocytosis, monensin does not prevent internalization. However, intracellular degradation of internalized ligands may be prevented.(ABSTRACT TRUNCATED AT 400 WORDS)

The isolation, enrichment, and comparative electron microscopic characterization of cellular components of the aged rat ventral prostate

Prostate cells were isolated from 3- and 23-month-old Sprague-Dawley rats. After sequential digestion with 0.1% collagenase at 37 degrees C, a mixed population of cells was obtained. The cells were layered on a five-step discontinuous Percoll gradient (g/ml: 1.024, 1.043, 1.048, 1.060, 1.089), centrifuged at 3,000 rpm X 30 minutes, which produced six distinct cellular subpopulations and a fibromuscular stroma (FMS). Electron microscopic characterization of the 3- and 23-month-old cellular subpopulations identified the following components, g/ml: debris and nonviable cells (1.020-1.025) nonsecretory epithelial cells (1.038-1.039), secretory epithelial cells (1.047-1.048), basal epithelial cells (1.057-1.059), differentiating epithelial cells (1.070-1.075), erythrocytes (1.085-1.089). This study demonstrates that one of the effects of age on the rat ventral prostate is an intracellular disorganization of isolated and enriched cellular components.

Effect of chronic alcohol consumption on the activities of liver plasma membrane enzymes: gamma-glutamyltransferase, alkaline phosphatase and 5'-nucleotidase

To study the effect of chronic alcohol administration on the activities of liver plasma membrane enzymes such as gamma-glutamyltransferase, alkaline phosphatase and 5'-nucleotidase, female rats were pair-fed for 6 weeks nutritionally adequate liquid diets containing either ethanol or isocaloric carbohydrates as controls. Compared to the control diet, chronic alcohol administration resulted in a significant enhancement of serum activities of gamma-glutamyltransferase, alkaline phosphatase and 5'-nucleotidase by 91% (P less than 0.005), 80% (P less than 0.001) and 65% (P less than 0.01), respectively. Concomitantly, chronic alcohol intake led to a striking increase of gamma-glutamyltransferase activities in liver homogenates by 68% (P less than 0.001), in liver plasma membranes rich in bile canaliculi by 80% (P less than 0.025), and in liver plasma membranes free of bile canaliculi by 24% (P less than 0.02). However, chronic ethanol consumption had no effect on alkaline phosphatase activities in liver homogenates and liver plasma membranes but significantly suppressed 5'-nucleotidase activities. These results therefore show that chronic intake of ethanol increases serum activities of enzymes originating from liver plasma membranes but has different effects on the enzyme activity in liver plasma membranes itself, suggesting that the alcohol-mediated increase of serum activities of various enzymes originating from liver plasma membranes might be due to different mechanisms.

Inhibitory effect of colchicine on translocation of alkaline phosphatase to the plasma membrane concomitant to its induction in rat liver

A single injection of colchicine (1--3 mg/kg body weight) caused a remarkable induction of hepatic alkaline phosphatase, which increased linearly in the homogenate starting at 5--6 h and reached a maximum level (14-fold of the control activity) at 20--22 h after the drug treatment. In the plasma membrane, however, the increase in specific activity and the recovery of alkaline phosphatase were greatly inhibited up to 12 h after the treatment. Such an inhibitory effect of colchicine was confirmed by a combination experiment of the drug treatment with bile duct ligation; in the plasma membrane elevation of the enzyme induced by bile duct ligation was also greatly retarded by colchicine. The subcellular distribution of the enzyme activity in livers was determined among the four groups of rats with or without bile duct ligation and/or colchicine administration taken at 8 h after each treatment. In the control and the bile duct-ligated livers, the highest specific activity was observed in the plasma membrane fraction, while in the colchicine-treated livers, with or without bile duct ligation, the highest activity was found in the Golgi fractions. These results indicate that the Golgi membranes enriched with the induced enzyme were blocked by the drug to prevent migration toward the plasma membranes enriched with the induced enzyme were blocked by the drug to prevent migration toward the plasma membrane, thus demonstrating involvement of the Golgi complex in the translocation route of newly synthesized alklaine phosphatase to the plasma membrane.

The origin of the dendritic reticulum cell. An experimental enzyme-histochemical and electron microscopic study on the rabbit spleen

To obtain more information concerning the origin of dendritic reticulum cells, the development of germinal centers in the spleens of rabbits was investigated by conventional light microscopy, enzyme histochemistry, and electron microscopy. Washed sheep erythrocytes were used as antigen. Splenic tissue was examined on the 13th, 18th, 21st, 27th and 48th day after antigen administration. Electron microscopic investigations revealed transitional forms between typical fibroblastic reticulum cells, which formed the framework of the entire splenic white pulp, and typical dendritic reticulum cells. During this transformation, the enzyme histochemical pattern of alkaline phosphatase disappeared and a positive alpha-naphthylacetate esterase reaction appeared in the transformed cells. On the basis of these findings, it is highly likely that dendritic reticulum cells develop through transformation of fibroblastic reticulum cells during the development of germinal centers in rabbit spleens. The characteristic folding of the surface membrane of dendritic reticulum cells is probably caused by the conspicuous increase in size of the Golgi apparatus, the detachment of vesicles, and the uptake of such vesicles by the cell membrane observed electron microscopically during the cellular transformation. Receptors that are of significance in antigen trapping might reach the cell surface in this manner, i.e., with the Golgi vesicles.

Qualitative and quantitative preservation of the fine structure of absorptive cells in cultured biopsies of human small-intestine

The fine structure of the absorptive cells in human small-intestinal biopsies cultured for 6, 24, and 48 h was analyzed qualitatively and quantitatively. The findings show generally good preservation of the cultured absorptive cells and a normal distribution, size, and relative volume of their cell organelles, but there was a systematic decrease in the apical cell surface and an increase in the number of apical vesicles and tubules after culturing. Since the apical vesicles and tubules are thought to have a function in the transport of cell-coat material from the Golgi apparatus to the cell surface, these findings raise the question of whether a delayed transport or extrusion of cell surface material occurs. The diminished relative volume of the mitochondria and the increased signs of autophagy in some poorly preserved absorptive cells, are assumed to be an adaption to less favourable culture conditions.

Glucosylation of sterols and polyprenolphosphate in the Golgi apparatus of Phaseolus aureus

Cellular membranes from dark grown hypocotyls of Phaseolus aureus Roxb. were separated by centrifugation on a continuous sucrose gradient. Each gradient fraction was monitored for activity of inosine diphosphatase (EC 3.6.1.6) and the ability to transfer glucose from UDP-[(14)C]glucose to endogenous lipids in vitro. The highest incorporation of radioactivity into lipids occurred in a particulate fraction correlated with the Golgi apparatus, sedimenting at sucrose densities of 31.5-33% w/w. Three endogenous lipids were glucosylated in vitro. The two main lipids were characterized as steryl glucoside and acylated steryl glucoside; data from chromatography and hydrolysis of the third lipid suggests that it is dolichyl-monophosphate-glucoside. Steryl glucoside was found to be the main glucoside synthesized, but the proportion of the acylated form increased with time. The results are discussed in the context of the role of the Golgi apparatus as a centre of membrane modification within the plant cell.

Trends in electron microscopy of skin

Some trends in electron microscopy of skin have emerged and should be pursued in the future. The fine structure and some basic cellular reaction patterns of epidermal cells are discussed to illustrate the interplay of morphologic, cytochemical, and tracer studies. Intracytoplasmic membranes and secretory granules, lysosomes and endocytic mechanisms, cytomembranes and cell surface specialization are discussed to show how these can be used to arrive at a more meaningful interpretation of structure. Despite all advances, however, a great deal more needs to be done before the details of skin structure are completely elucidated.

Studies on the radiosensitivity of the function of the Golgi complex

The uptake of 3H-glucosamine into primary human-embryo fibroblasts and into the Golgi-rich fraction isolated from liver of mice labelled in vivo was studied, after various doses of X-radiation, by autoradiography and biochemical methods. A dose of 90 rad resulted in an increased precursor uptake in interphase cells at 24 hours and in mitotic cells at 48 hours after irradiation; 226 rad had virtually no effect on the grain counts of interphase cells, but reduced the labelling of mitotic forms. The characteristic intracellular localization of the grains were not influenced by these doses. Although no immediate radiation-induced reaction could be observed in liver cells either, significant stimulation of the 3H-glucosamine incorporation was measured in isolated Golgi-rich fractions 24 hours after whole-body irradiation with 90, 450, or 905 rad. This phenomenon is discussed as a part of the somatic regeneration of membrane structures.

Collagen deposition on a preformed grid

Appearance of collagen fibrils in the cuticle was seen by electron microscopy to be preceded by formation of a finely filamentous matrix material. At first, the fine filaments of the matrix are unorganized. However, signs of orthogonal ordering soon appear in the most superficial portion of the cuticle, and subsequently appear more basally and closer to the underlying epidermis. Meanwhile, fibrils of different staining properties and identifiable as collagen begin to be deposited in the superficial portion of the cuticle, the same region which first showed organized fine filaments. Then, like the fine filaments before them, the collagen fibrils polymerize more basally. Collagen appears to polymerize on the preformed skeleton of fine filaments as though the fine filaments lagen fibrils seems to require direct cellular intervention but occur first in that portion of the cuticle which is furthest away from the underlying epidermis. The fine filaments may be self ordering, extracellular macromolecules which in turn determine the polymerization of collagen fibrils.

The formation and cytochemical characterization of cortical granules in ovarian oocytes of the golden hamster (Mesocricetus auratus)

The formation and cytochemical characterization of cortical granules in the ovarian oocytes of the golden hamster have been investigated by use of light and electron microscopical techniques. Particular emphasis is given to the changing population of organelles associated with cortical granule formation. Our observations indicate that cortical granules are produced by the participation of both the Golgi complex and the rough endoplasmic reticulum. Ultrastructural cytochemistry reveals that the cortical granules are composed of glycoprotein. The cortical granules are released at fertilization by a merocrine-type of secretory process.

Golgi organelle response to the antibiotic X537A

The effects of the ionophoric antibiotic X537A on cell structure were studied with phase-contrast, fluorescence, and electron microscopy. X537A induced selective vacuolation of the Golgi apparatus of vascular and intestinal smooth muscle, epithelium, plasma cells, and cultured chick heart and guinea pig vascular smooth muscle cells. The swelling of the Golgi apparatus induced by X537A was reversible in the systems examined for reversibility: vascular smooth muscle and cultured chick heart. Myelin figures were common in the Golgi apparatus vacuolated by X537A. Fluorescence microscopy of cultured cells incubated with X537A showed the characteristic blue X537A fluorescence associated with lipid globules in the cultured cells. Incubation of cultured chick heart cells with X537A reduced the beating rate and, after 24-72 h, abolished the sarcomere pattern. The swelling of the Golgi membranes produced by X537A in cultured vascular smooth muscle was associated with inhibition of D-[6-3H]glucosamine and [35S]sulfate incorporation into glycosaminoglycans.

Ultrastructural analysis of the granulosa--luteal cell transition in the ovary of the dog

The transition from ovarian granulosa to lutein cell during the estrus cycle of 60 pregnant and non-pregnant beagle bitches was analyzed by light and electron microscopy (both 100 and 1000 KV). Early proestrus was characterized by a gradual rise in serum estrogen levels, hyperplasia of the granulosa cells, the accumulation of follicular fluid, and the development of tortuous intercellular channels. During the second half of proestrus, serum estrogen levels continued to rise, but growth, division, and differentiation of the granulosa cells was minimal. Estrus was marked by the first acceptance of the male and a well-defined LH peak In the subsequent 24 hour period, the granulosa-lutein cells hypertrophy rapidly and develop a large Golgi apparatus, small profiles of granular endoplasmic reticulum, numerous microfilaments, and large gap junctions between the cells. Mitochondria also proliferate, enlarge, and elongate, but retain lamelliform cristae. Luteinization of the cells and progesterone secretion begin just after ovulation which in turn occurs about 24 hours after the LH peak. On the third and fourth day of estrus, numerous small vesicles of agranular endoplasmic reticulum fill the extoplasm and the mitochondria swell up and round off. The vesicles rapidly fuse into whorled and flattened cisternae or anastomosing tubules of agranular endoplasmic reticulum, while the mitochondria develop tubulovesicular cristae. These structures gradually become organized with respect to the basal lamina. The Golgi apparatus is centered over the pole of the nucleus that faces the pericapillary space. Stacked and whorled cisternae of agranular ER develop in the lateral margins and avascular end of the cell while mitochondria and tubular elements of agranular ER predominate in the central medial and most basal portions of the cytoplasm. Microfilaments are ubiquitous and appear to be instrumental in this orientation process. The cell surface develops three distinct regional specializations that coincide with the underlying cellular compartments: interconnecting pleomorphic folds fill the pericapillary space; long tenous microvilli project from the lateral cell surface and form tortuous intercellular channels and canaliculi; and large gap junctions form along the margins of the cell furthest removed from the basal lamina. By the sixth day of estrus, the granulosa-luteal cell transition is nearly complete and serum progesterone levels are on the rise.

Papillary cystadenofibroma of endometrium: a histochemical and ultrastructural study

The light and electron microscopic as well as the histochemical characteristics of a papillary cystadenofibroma of the endometrium are described. The neoplasm arose in the lower uterine segment and was composed of a florid fibroblastic growth arranged in club-shaped papillae projecting into clefts and cystic spaces. The epithelium lining the plicae, recesses, and cysts was exclusively of the mucous-secreting type and bore identical histochemical and subcellular characteristics to that of the normal endocervical epithelium. Essentially similar papillary lesions were recently reported in the endocervix, endometrium, and fallopian tube. The pathogenesis and differential diagnosis of this distinct neoplasm are discussed in the light of the available morphological data.

Subcellular compartmentalization of the luteal cell in the ovary of the dog

The compartmentalization of the parenchyma of the corpus luteum in the dog was studied by both 100 and 1000 KV electron microscopy. The organells within the luteal cell are oriented with a high degree of consistency towards the pericapillary space. Characteristically, the avascular pole and the lateral margins of the cell posses predominantly stacked and whorled cisternae of agranular ER. In the central medial portions of the cell, pleomorphic mitochondria with tubulo-vesicular cristae and anastomosing tubules of agranular ER predominate. However, the distribution of organelles in this compartment is graded. Mitochondria predominate in the central medial areas while tubular ER is more dominant peripherally. Microfilaments are ubiquitous in this compartment and run a longitudinal course between and around the subcellular components towards the pericapillary space. The Golgi apparatus is large and prominent and is positioned over the pole of the nucleus that faces the basal lamina. Coated vesicles are abundant in the Golgi regions and along the lateral surface of the cell. Three distinct regional specializations of the cell surface exist. The basal surface contains long pleomorphic cytoplasmic folds that fill the pericapillary space, are interconnected by small gap junctions and contain abundant multivesicular bodies. The lateral cell surface is covered with microvilli and is organized into tortuous intercellular channels and canaliculi. These are interrupted at intervals by cytoplasmic protrusions that extend from one cell well into the cytoplasm of the next. Large, well-developed gap junctions line the margins of the cells furthest removed from the pericapillary space. Finally, the individual cells exhibit heterogeneity with respect to the amount one subcellular organelle or compartment is expressed relative to another. These observations are discussed in relation to the subcellular compartmentalization of progesterone synthesis and release.

Structural and functional dynamics of oogenesis in Glossina austeni: vitellogenesis with special reference to the follicular epithelium

Morphological changes of the oocyte, follicle cells and nurse cells of the ovaries of the viviparous fly Glossina austeni during vitellogenesis and postvitellogenesis are outlined. During vitellogenesis, material is pinocytosed and incorporated into yolk spheres by subsequent fusions. Various lines of evidence are presented that indicate much of this material is derived from the follicular epithelium. The ultrastructure of the follicular cells throughout the 9 day cycle and their role in protein synthesis is presented. Subsequent to vitellogenesis, the follicle cells synthesize the secondary envelopes.

Golgi beta-glucuronidase of androgen-stimulated mouse kidney

Subcellular fractions were prepared from mouse kidney homogenates by differential and sucrose-gradient centrifugation. A fraction enriched in Golgi apparatus was obtained, which had considerably enriched galactosyltransferase and thiamin pyrophosphatase activities, and was morphologically typical of Golgi material. This preparation also had high beta-glucuronidase activity, which increased concomitantly with microsomal beta-glucuronidase activity during the specific stimulation of the enzyme in male mouse kidney after androgen administration. The degree of stimulation was much greater in the Golgi fraction. Gel-electrophoretic patterns of Golgi beta-glucuronidase resembled more closely those of the enzyme located within lysosomes, but contained minor bands similar to those described previously (Swank & Paigen, 1973) as characteristic of the microsomal enzyme. It was concluded that the Golgi complex is involved in the distribution of the enzyme after its synthesis to both lysosomal and microsomal fractions.