Rice protein-body formation: all types are initiated by dilation of the endoplasmic reticulum

The ultrastructure of protein deposition in the starchy endosperm of developing rice (Oryza sativa L.) grains was examined in conventionally fixed (glutaraldehyde and osmium tetroxide) tissues and also in thick sections (0.3 m) of zinc iodide-osmium tetroxide post-fixed tissue. Three types of previously characterised protein body were observed and it was shown that each type was initiated by dilations of the endoplasmic reticulum. Crystalline type protein bodies were initiated by a ribosome-free dilation from rough cisternal endoplasmic reticulum and developed by inclusion of protein from dictyosome-derived vesicles. The large spherical and small spherical protein bodies developed within the cisternae of the rough endoplasmic reticulum.Abbreviations Cr crystalline protein body - DAF days after fertilization - ER endoplasmic reticulum - Ls large spherical protein body - Ss small spherical protein body - ZIO zinc iodide-osmium tetroxide     

Ultrastructural morphometric analysis of the uterine epithelium during early pregnancy in the sheep

Stereological techniques were used to quantify ultrastructural changes in the caruncular epithelium during the pre- (Day 13), peri- (Day 16) and post- (Days 19 and 22) attachment periods of placentation. Tissues from Day-13 non-pregnant ewes were used as controls. Uteri for stereological evaluation were perfused via the uterine artery with 3% glutaraldehyde and separated into proximal, middle and distal regions. Tissues from caruncular areas were processed for electron microscopy. Volume fractions (Vv) of nuclei, mitochondria, lipid and cytoplasmic granules were estimated by point-counting volumetry. Surface areas per unit tissue volume (Sv) of mitochondrial membranes and cristae, Golgi, plasmalemma, endoplasmic reticulum and nuclear membranes were estimated by line-intersection counting. The only significant difference between pregnant and non-pregnant uterine epithelium at Day 13, a time before attachment, was a lower Sv of smooth endoplasmic reticulum (SER) in tissue from pregnant ewes. This value returned to control (non-pregnant Day 13) levels at Day 16, and was again significantly reduced at Days 19 and 22. The Vv of lipid decreased significantly at Day 16 and remained at reduced levels thereafter. These changes may reflect the effects of conceptus products on lipid storage and mobilization. The Sv of rough endoplasmic reticulum (RER) significantly increased on Day 16 of gestation, and remained elevated on Day 19. These results may reflect increased synthesis of protein for export at these times. In general, several of the values measured which may be indicative of cellular metabolism were reduced at Day 22 of pregnancy, perhaps suggesting diminished metabolism by the uterine epithelium after attachment of the trophoblast.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intracellular transport of albumin through the secretory apparatus of rat liver parenchymal cells. An immunocytochemical study

The fine structural localization of albumin in rat liver parenchymal cells was determined by an improved immunocytochemical method and serial sectioning. Albumin in the secretory apparatus of the parenchymal cells was present in segments of the rough endoplasmic reticulum, interrupted with negative segments, in transport vesicles, Golgi saccules, finely anastomosed tubules and vesicles on the trans side of the Golgi complex, and in secretion granules. Horizontally sectioned Golgi saccules contained lipoprotein particles on one side and albumin on the other side. After transport, the vesicles that contained albumin fused with the so-called rigid lamellae on the trans-side of the Golgi complex. Ultrathin serial sections revealed no true structural continuity between the endoplasmic reticulum and the cis-aspect of the Golgi complex. We concluded that secretory proteins are transported from the endoplasmic reticulum to the Golgi complex by transport vesicles that bud from the endoplasmic reticulum and fuse with the Golgi saccules. These vesicles fuse regularly with the Golgi saccules on the cis-side and occasionally with tubular elements on the trans-aspect that may belong to the so-called GERL.     

Immunocytochemical localization of reserve protein in the endoplasmic reticulum of developing bean (Phaseolus vulgaris) cotyledons

The ultrastructure of the storage parenchyma cells of the cotyledons of developing bean (Phaseolus vulgaris L.) seeds was examined in ultrathin frozen sections of specimens fixed in a mixture of glutaraldehyde, formaldehyde and acrolein, infused with 1 M sucrose, and sectioned at-80° C. Ultrastructural preservation was excellent and the various subcellular organelles could readily be identified in sections which had been stained with uranyl acetate and embedded in Carbowax and methylcellulose. The cells contained large protein bodies, numerous long endoplasmic reticulum cisternae, mitochondria, dictyosomes, and electron-dense vesicles ranging in size from 0.2 to 1.0 m. Indirect immunolabelling using rabbit immunoglobulin G against purified phaseolin (7S reserve protein), and ferritin-conjugated goat immunoglobulin G against rabbit immunoglobulin G was used to localize phaseolin. With a concentration of 0.1 mg/ml of anti-phaseolin immunoglobin G, heavy labeling with ferritin particles was observed ober the protein bodies, the cisternae of the endoplasmic reticulum, and the vesicles. The same structures were lightly labeled when the concentration of the primary antigen was 0.02 mg/ml. Ferritin particles were also found over the Golgi bodies. The absence of ferritin particles from other organelles such as mitochondria and from areas of cytoplasm devoid of organelles indicated the specificity of the staining, especially at the lower concentration of anti-phaseolin immunoglobulin G.Abbreviations ER endoplasmic reticulum - IgG immunoglobulin G     

The ultrastructure of mouse lung: the alveolar macrophage

Free alveolar macrophages of normal mouse lung have been studied in the electron microscope. The tissue was obtained from several young adult white mice. One other animal was instilled intranasally with diluted India ink 1(1/2) hours prior to the removal of the lung. Thin sections of the osmium-fixed, methacrylate-embedded tissue were examined either in an RCA EMU 2 electron microscope or in a Siemens and Halske Elmiskop I b. A few thick sections obtained from the same embeddings were stained for iron. The normal alveolar macrophages, which are usually in contact with the alveolar epithelium, were found to contain a variety of inclusion bodies, along with the usual cytoplasmic components like mitochondria, endoplasmic reticulum, and Palade granules. Another typical component of the cytoplasm of these cells which appears as small ( approximately 6 mmicro) very dense granules of composite fine structure is interpreted as ferritin. It is assumed that this ferritin is formed from red blood cells ingested by the alveolar macrophages. The macrophages in the alveoli were found to phagocytize intranasally instilled India ink particles. Such cells, with engulfed India ink particles, were often of more rounded form and the particles were frequently seen lying inside membrane-bound vacuoles or vesicles of the cytoplasm. The membrane of a few vesicles containing India ink particles was seen as the invaginated portion of the cell plasma membrane, and in one instance these same vesicles were seemingly interconnected with a rough surfaced cisterna of the endoplasmic reticulum. The process of phagocytosis is recognized as related to the "normal" process of pinocytosis.     

Fine Structure of Botrytis fabae Sardina Conidia

The fine structure of Botrytis fabae conidia was studied usinga variety of electron-microscope techniques. The spore walllacks conspicuous ornamentation and consists of microfibrilsembedded in a granular matrix. The two distinct wall layersseen in chemically fixed sections cannot be detected in cross-fracturedreplicas; the two layers are probably structurally similar.The outer surface of the plasmalemma is covered with branchedinvaginations and two kinds of particles. Three distinct typesof particles are present on the inner surface of the plasmalemma.In freeze-etched replicas nuclei, vacuoles, and other organellesalways appear smoothly rounded. Small vesicles pass throughthe plasmalemma into the cell wall. Particles approximately10 nm in diameter occur in compact rows on the cristae of cross-fracturedmitochondria: dense spherical particles, probably of calciumphosphate, are present in chemically fixed mitochondria. Prevacuolesand vesicles with membranous inclusions can be seen in bothcross-fractured replicas and chemically fixed sections. In cross-fracturedreplicas vacuoles and lipid bodies are frequently joined bystrands of endoplasmic reticulum.     

The Ultrastructure of Mouse Lung: The Alveolar Macrophage

Free alveolar macrophages of normal mouse lung have been studied in the electron microscope. The tissue was obtained from several young adult white mice. One other animal was instilled intranasally with diluted India ink 1½ hours prior to the removal of the lung. Thin sections of the osmium-fixed, methacrylate-embedded tissue were examined either in an RCA EMU 2 electron microscope or in a Siemens and Halske Elmiskop I b. A few thick sections obtained from the same embeddings were stained for iron. The normal alveolar macrophages, which are usually in contact with the alveolar epithelium, were found to contain a variety of inclusion bodies, along with the usual cytoplasmic components like mitochondria, endoplasmic reticulum, and Palade granules. Another typical component of the cytoplasm of these cells which appears as small (~6 mµ) very dense granules of composite fine structure is interpreted as ferritin. It is assumed that this ferritin is formed from red blood cells ingested by the alveolar macrophages. The macrophages in the alveoli were found to phagocytize intranasally instilled India ink particles. Such cells, with engulfed India ink particles, were often of more rounded form and the particles were frequently seen lying inside membrane-bound vacuoles or vesicles of the cytoplasm. The membrane of a few vesicles containing India ink particles was seen as the invaginated portion of the cell plasma membrane, and in one instance these same vesicles were seemingly interconnected with a rough surfaced cisterna of the endoplasmic reticulum. The process of phagocytosis is recognized as related to the "normal" process of pinocytosis.     

EFFECTS OF THE PHYSICAL ENVIRONMENT ON SOME LIPOPROTEIN LAYER SYSTEMS AND OBSERVATIONS ON THEIR MORPHOGENESIS

Lipoprotein membrane systems such as chloroplasts and the endoplasmic reticulum exhibit a generalized swelling response. The initial effect is an increase in interlamellar spacing, but as swelling proceeds, the membranes are transformed into closed thin-walled spherical vesicles. Available evidence suggests that morphogenesis of the endoplasmic reticulum of Nitella and the lamellar system of the Zea chloroplasts involves fusion of small spherical vesicles to yield closed double membrane structures, which subsequently undergo further differentiation. It is suggested that the vesicles comprise a convenient "micellar" form by which lipides may be transported within the cell from the sites of lipide synthesis to regions of lamellar growth. The characteristic formation of vesicles in swelling and the apparent fusion of vesicles in morphogenesis appear to represent two aspects of a fundamental plasticity of lipoprotein layer systems.     

烫伤对大鼠下丘脑视上核、室旁核AVP神经元的影响──免疫电镜观察及形态计量分析

为研究加压素与应激的关系,我们曾应用免疫细胞化学（ＰＡＰ）方法结合图像分析技术观察到烫伤应激后２小时视上核、室旁核加压素神经元免疫反应阳性物质的总体积减小最明显。本文采用免疫电镜技术,进一步观察了烫伤后２小时视上核、室旁核加压素神经元超微结构的变化,并运用体视学方法定量分析了对照组及烫伤后２小时组视上核、室分校加压素神经元各２４０张照片的粗面内质网、高尔基复合体及线粒体的体积密度（Ｖｖ）、面积密度（Ｓｖ）、面数密度（Ｎａ）等。结果显示：烫伤后２小时组视上核、室旁核加压素神经元的粗面内质网的Ｖｖ．Ｓｖ显著增大,说明合成功能已开始增强,但是,高尔基复合体的Ｖｖ、Ｓｖ及阳性分泌颗粒却显著减少,因而引起总体积的缩小。从超微结构水平进一步证实加压素参与应激过程。     

Studies on mouse liver urate oxidase

Summary The fine localization of urate oxidase was investigated with immunoferritin technique directly applied to ultrathin sections of fixed and frozen mouse liver tissue. The ferritin particles indicating the urate oxidase antigen were localized in microbodies, cisternae of rough- and smooth-surfaced endoplasmic reticulum (ER), and Golgi vacuoles and vesicles. In ER the particles were abundantly observed in dilated terminal portions. In addition, Golgi lamellae were slightly stained comparing with the vacuoles and vesicles. The staining with ferritin particles was inhibited by the treatment of unconjugated anti-urate oxidase before ferritin conjugate staining. From these results, the formation of microbody was discussed.     

Elektronenmikroskopische Untersuchungen von Differenzierungsvorgängen bei Moosen

Summary In meristematic cells of the gemma of Riella helicophylla and in young bud cells from the protonema of Funaria hygrometrica the cell plate is formed by fusion of small vesicles originating from the Golgi apparatus. These spherical vesicles of about 0.1 m diameter have an electron dense centre, probably consisting of pectic substances or their precursors. The endoplasmic reticulum producing multivesicular bodies participate in cell plate formation too. Another cytoplasmic component forming the cell plate are coated vesicles, the origin of which is the Golgi apparatus and perhaps also the endoplasmic reticulum. In view of these observations the question of whether the endoplasmic reticulum or the Golgi apparatus forms the cell plate must be answered in this way: both endoplasmic reticulum and Golgi apparatus supply material for growth of the cell plate. Multivesicular bodies, coated vesicles and other small vesicles of unknown nature participate in the formation of the primary wall.

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Zum Teil finanziert mit Sondermitteln des Landes Niedersachsen an Prof. Dr. M. Bopp.     

Different concentrations of thyroid peroxidase and thyroglobulin in the nuclear envelope and the endoplasmic reticulum throughout the cytoplasm.

Thyroid peroxidase (TPO) and thyroglobulin (TG) represent two major glycoproteins of thyroid follicular cells performing biological functions such as iodination, transcytosis of thyroglobulin, and formation of thyroid hormones. They are involved in thyroid autoimmunity and thyroid inborn metabolic disorders. Studying these processes at a molecular level includes the determination of their precise intracellular distribution. An evaluation of the relative concentrations of TG and TPO in different subcellular compartments was carried out in stimulated human follicular cells using thin-frozen sections and the immunogold technique. It is documented that TG is transported from the endoplasmic reticulum and the Golgi apparatus to the follicular lumen by transport vesicles; most of it being present in the expanded endoplasmic reticulum throughout the cytoplasm. On the other hand, gold particles indicating TPO are adjacent to the membranes of the exocytotic pathway. They do not label the basolateral membrane but show the strongest density in the nuclear envelope and the apical membrane. The labeling density of TPO is about four times higher in the nuclear envelope than in the endoplasmic reticulum throughout the cytoplasm. In contrast, TG is concentrated three times higher in the rough endoplasmic reticulum throughout the cytoplasm than in the nuclear cisternae. Our results give the first quantitative evidence that TPO and TG are concentrated in different subcompartments of the endoplasmic reticulum. Because previous studies demonstrated the nuclear envelope as the site where the synthesis of endogenous peroxidase (Br?kelmann, J., D. W. Fawcett, Biol. Reprod. 1, 59-71 (1969)) begins, we suggest that synthesis of these functionally related proteins happens in specialized parts of the endoplasmic reticulum.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immunochemical studies on the role of the Golgi complex in protein-body formation in rice seeds

Antibodies raised against purified glutelins and prolamines were employed as probes to study the cellular routes by which these proteins are deposited into protein bodies of rice (Oryza sativa L.) endosperm. Three morphologically distinct protein bodies, large spherical, small spherical, and irregularly-shaped, were observed, in agreement with existing reports. Immunocytochemical studies showed the presence of glutelins in the irregularly-shaped protein bodies while the prolamines were found in both the large and small spherical protein bodies. Both the large and small spherical protein bodies, distinguishable by electron density and gold-labeling patterns, appear to be formed by direct deposition of the newly formed proteins into the lumen of the rough endoplasmic reticulum (ER). In contrast, glutelin protein bodies are formed via the Golgi apparatus. Small electron-lucent vesicles are often found at one side of the Golgi. Electron-dense vesicles, whose contents are labeled by glutelin antibody-gold particles, are commonly observed at the distal side of the Golgi apparatus and fuse to form the irregularly shaped protein bodies in endosperm cells. These observations indicate that the transport of rice glutelins from their site of synthesis, the ER, to the site of deposition, the protein bodies, is mediated by the Golgi apparatus.Abbreviations BSA bovine serum albumin - Da dalton - DAF days after flowering - ER endoplasmic reticulum - GL irregularly shaped - L large spherical - S small spherical (protein bodies) - PBS phosphate-buffered saline - PTA phosphotungstic acid     

LYSOSOMES AND GERL IN NORMAL AND CHROMATOLYTIC NEURONS OF THE RAT GANGLION NODOSUM

The rat ganglion nodosum was used to study chromatolysis following axon section. After fixation by aldehyde perfusion, frozen sections were incubated for enzyme activities used as markers for cytoplasmic organelles as follows: acid phosphatase for lysosomes and GERL (a Golgi-related region of smooth endoplasmic reticulum from which lysosomes appear to develop) (31–33); inosine diphosphatase for endoplasmic reticulum and Golgi apparatus; thiamine pyrophosphatase for Golgi apparatus; acetycholinesterase for Nissl substance (endoplasmic reticulum); NADH-tetra-Nitro BT reductase for mitochondria. All but the mitochondrial enzyme were studied by electron microscopy as well as light microscopy. In chromatolytic perikarya there occur disruption of the rough endoplasmic reticulum in the center of the cell and segregation of the remainder to the cell periphery. Golgi apparatus, GERL, mitochondria and lysosomes accumulate in the central region of the cell. GERL is prominent in both normal and operated perikarya. Electron microscopic images suggest that its smooth endoplasmic reticulum produces a variety of lysosomes in several ways: (a) coated vesicles that separate from the reticulum; (b) dense bodies that arise from focal areas dilated with granular or membranous material; (c) "multivesicular bodies" in which vesicles and other material are sequestered; (d) autophagic vacuoles containing endoplasmic reticulum and ribosomes, presumably derived from the Nissl material, and mitochondria. The number of autophagic vacuoles increases following operation.     

Protein Bodies at Early Stages of Development in High Lysine Mutant Notch-2 and Parent NP-113 Barley

In barley parent NP-113, endospermic protein bodies originate on rough endoplasmic reticulum, either as electron transluscent vesicles or as very small, spherical, electron dense protein bodies, These are translocated to vacuoles tor enlargement and subsequent storage, Endospermic protein bodies of Notch-2 high lysine mutant are either vacuolar, or confined to distended cisternae of smooth endoplasmic reticulum. Vacuolar protein bodies are of two types one, flocculent, which loosely fill up almost the entire vacuolar space; two, spherical, relatively compact and granular, Protein bodies, confined to smooth endoplasmic reticulum are small, spherical, electron dense or electron transluscent, These protein bodies fuse to form electron dense proteinaceous masses which are deposited in the cytosol due to disruption of the confining smooth endoplasmic reticulum.     

Calcium Transport in Sealed Vesicles from Red Beet (Beta vulgaris L.) Storage Tissue : I. Characterization of a Ca-Pumping ATPase Associated with the Endoplasmic Reticulum

Calcium transport was examined in microsomal membrane vesicles from red beet (Beta vulgaris L.) storage tissue using chlorotetracycline as a fluorescent probe. This probe demonstrates an increase in fluorescence corresponding to calcium accumulation within the vesicles which can be collapsed by the addition of the calcium ionophore A23187. Calcium uptake in the microsomal vesicles was ATP dependent and completely inhibited by orthovanadate. Centrifugation of the microsomal membrane fraction on a linear 15 to 45% (w/w) sucrose density gradient revealed the presence of a single peak of calcium uptake which comigrated with the marker for endoplasmic reticulum. The calcium transport system associated with endoplasmic reticulum vesicles was then further characterized in fractions produced by centrifugation on discontinous sucrose density gradients. Calcium transport was insensitive to carbonylcyanide m-chlorophenylhydrazone indicating the presence of a primary transport system directly linked to ATP utilization. The endoplasmic reticulum vesicles contained an ATPase activity that was calcium dependent and further stimulated by A23187 (Ca(2+), A23187 stimulated-ATPase). Both calcium uptake and Ca(2+), A23187 stimulated ATPase demonstrated similar properties with respect to pH optimum, inhibitor sensitivity, substrate specificity, and substrate kinetics. Treatment of the red beet endoplasmic reticulum vesicles with [gamma-(32)P]-ATP over short time intervals revealed the presence of a rapidly turning over 96 kilodalton radioactive peptide possibly representing a phosphorylated intermediate of this endoplasmic reticulum associated ATPase. It is proposed that this ATPase activity may represent the enzymic machinery responsible for mediating primary calcium transport in the endoplasmic reticulum linked to ATP utilization.     

Pancreatic microsomes; an integrated morphological and biochemical study

The pancreatic exocrine cell of the guinea pig has a voluminous endoplasmic reticulum distinguished by extensive association with small, dense particles, and by its orderly disposition in the basal region of the cell. In addition to the small, ( approximately 15 mmicro), dense particles attached to the limiting membrane of the endoplasmic reticulum, numerous particles of similar appearance are found freely scattered in the cytoplasmic matrix. The various cell structures of pancreatic exocrine cells can be satisfactorily identified in pancreatic homogenates. The microsome fraction consists primarily of spherical vesicles (80 to 300 mmicro), limited by a thin membrane (7 mmicro) which bears small ( approximately 15 mmicro) dense particles attached on its outer surface. The content of the microsomal vesicles is usually of high density. Pancreatic microsomes derive by extensive fragmentation mainly from the rough surfaced parts of the endoplasmic reticula of exocrine cells. A few damaged mitochondria and certain dense granules ( approximately 150 mmicro) originating probably from islet cells, contaminate the microsome fraction. Pancreatic microsomes contain RNA, protein, and a relatively small amount of phospholipide and hemochromogen. They do not have DPNH-cytochrome c reductase activity. In six experiments the RNA/protein N ratios were found grouped around two different means, namely 0.6 and 1.3. Pancreatic microsomes are more labile than liver microsomes but react in a similar way to RN-ase-(loss of the particulate component and RNA), and deoxycholate treatment (loss of the membranous component and of phospholipide, hemochromogen, and most of the protein). Postmicrosomal fractions consisting primarly of small ( approximately 15 mmicro), dense particles of ribonucleoprotein (RNA/protein N ratio = 1 to 2) were obtained by further centrifugation of the microsomal supernatant. The small nucleoprotein particles of these fractions are frequently found associated in chains or clusters.     

Mitotic Golgi fragments in HeLa cells and their role in the reassembly pathway

Immunoelectron microscopy and stereology were used to identify and quantitate Golgi fragments in metaphase HeLa cells and to study Golgi reassembly during telophase. On ultrathin frozen sections of metaphase cells, labeling for the Golgi marker protein, galactosyltransferase, was found over multivesicular Golgi clusters and free vesicles that were found mainly in the mitotic spindle region. The density of Golgi cluster membrane varied from cell to cell and was inversely related to the density of free vesicles in the spindle. There were thousands of free Golgi vesicles and they comprised a significant proportion of the total Golgi membrane. During telophase, the distribution of galactosyltransferase labeling shifted from free Golgi vesicles towards Golgi clusters and the population of free vesicles was depleted. The number of clusters was no more than in metaphase cells so the observed fourfold increase in membrane surface meant that individual clusters had increased in size. More than half of these had cisterna(e) and were located next to "buds" on the endoplasmic reticulum. Early in G1 the number of clusters dropped as they congregated in the juxtanuclear region and fused. These results show that fragmentation of the Golgi apparatus yields Golgi clusters and free vesicles and reassembly from these fragments is at least a two-step process: (a) growth of a limited number of dispersed clusters by accretion and fusion of vesicles to form cisternal clusters next to membranous "buds" on the endoplasmic reticulum; (b) congregation and fusion to form the interphase Golgi stack in the juxtanuclear region.     

Ontogeny of microbodies (glyoxysomes) in cotyledons of dark-grown watermelon (Citrullus vulgaris Schrad.) seedlings

The development of glyoxysomal marker enzyme activities and concomitant ultrastructural evidence for the ontogeny of glyoxysomes has been studied in cotyledons of dark-grown watermelon seedlings (Citrullus vulgaris Schrad., var. Florida Giant). Catalase (CAT, EC 1.11.1.6) was stained in glyoxysomal structures with the 3,3-diaminobenzidine procedure. Serial sections and high-voltage electron microscopy were used to analyze the three-dimensional structure of the glyoxysomal population. With early germination CAT was localized in three distinct cell structures: spherical microbodies already present in freshly imbibed cotyledons; in appendices on lipid bodies; and in small membrane vesicles between the lipid bodies. Due to their ribosome-binding capacity, both appendices and small vesicles were identified as derivatives of the endoplasmic reticulum (ER). In the following period, glyoxysome formation and lipid body degradation were found to be inseparable processes. The small CAT-containing vesicles attach to a lipid body on a restricted area. Both lipid body appendices and attached cisternae enlarge around and between tightly packed lipid bodies and eventually become pleomorphic glyoxysomes with lipid bodies entrapped into cavities. The close contact between lipid body and glyoxysomes is maintained until the lipid body is digested and the glyoxysomal cavity becomes filled with cytoplasm. During the entire period of increase in glyoxysomal enzyme activities, no evidence was obtained for destruction of glyoxysomes, but small CAT-containing vesicles were observed from day 2 through day 6 after imbibition, indicating a continuous de novo formation of glyoxysomes. This study does not substantiate the hypothesis that glyoxysomes bud directly from the ER. Rather, ER-derivatives, e.g., lipid body appendices or cisternae attached to lipid bodies are interpreted as being glyoxysomal precursors that grow in close contact with lipid bodies both in volume and surface membrane area.Abbreviations CAT catalase - DAB 3,3 diaminobenzidine tetrahydrochloride - ER endoplasmic reticulum - GOX glycolate oxidase - HPR hydroxypyruvate reductase - HVEM high-voltage electron microscopy - ICL isocitrate lyase - MS malate synthase - RER rough endoplasmic reticulum In the figures bars represent 0.1 m (if not stated otherwise)