Evidence for a role of the ovarian surface epithelium in the ovulatory mechanism of the sheep: secretion of urokinase-type plasminogen activator

The extent of dissolution of tissues within the apical wall of the preovulatory ovine follicle (formative site of rupture) is greater than that of the counterpart basal hemisphere. It has been hypothesized that proteolytic enzymes released from contiguous ovarian surface epithelial cells contribute to apical follicular weakening and ovulation. Ovulation occurs from the dominant ovarian follicle of proestrous ewes at approximately 24 h after administration of luteinizing hormone-releasing hormone (LHRH). Follicular rupture was inhibited in sheep in which the ovarian surface epithelium was surgically removed at 8 (but not at 16) h following LHRH. Plasminogen activator bioactivity was greater within the follicular apex compared to basal wall at 12 h; this difference was negated by prior removal of epithelium at 8 h after LHRH. A low M_r plasminogen activator of the urokinase-type (uPA) was secreted by epithelial cells recovered from the surface of preovulatory follicles (Western blot analysis). Ovarian epithelium, not associated with a preovulatory follicle, produced very little uPA. Finally, ovulation was suppressed by intrafollicular injection (8 h post-LHRH) of uPA antibodies. It is suggested that secretion of uPA by ovarian surface epithelium and consequent plasmin up-regulation within neighboring tunica albuginea and follicular theca is a contributing factor in the mechanism of ovulation.     

Formation of the rupture site in preovulatory hamster and mouse follicles: Loss of the surface epithelium

Changes in the morphology of epithelial cells covering the sides and apex of ovarian follicles were examined in mice and hamsters during the final 13 hr before rupture using light and electron microscopy. At the time of the surge of luteinizing hormone, approximately 13 hr before follicle rupture, epithelial cells along the follicle sides are spherical, covered with microvilli, and remain so throughout the entire cycle. As ovulation approaches, cells at the apex become progressively flatter, increase in diameter, and undergo a reduction in the number and length of microvilli. By 2 hr before ovulation, the microvilli are present only along the boundary between adjacent cells and the cells are in different stages of degeneration. In some cells, the cytoplasm is electron dense and the nuclei are pyknotic. Other cells become electron lucent and cytoplasmic elements are leached from the cell. The apical plasma membrane is lost first over the center of the cell and later over the periphery. Epithelial cells detach from the apex individually until a large patch devoid of cells is formed. This includes the site of eventual rupture. The loss of epithelial cells from the apex of ovarian follicles of other species is compared with our results, and the processes involved in stretching, degeneration, and sloughing of the epithelial cells are discussed.     

Further studies of the surface epithelium covering preovulatory rabbit follicles with special reference to lysosomal alterations

Summary The fine structure of the surface epithelium over preovulatory rabbit follicles was examined parallel with visualization of acid phosphatase at the electron microscopical level. Small enzyme positive vesicles were pinched off from the Golgi cisternae and similar vesicles fused and got incorporated into larger lysosomes of dense body type. Some lysosomes appeared in direct continuity with tubular enzyme positive structures. Other possible ways of increase of the lysosomal pool are indicated and discussed.As in previous studies a maximal accumulation of lysosomes was found in the apical epithelium at 8 h after an ovulatory dose of human chorionic gonadotrophin (HCG); thereafter a gradual loss of lysosomes ensued. Before the lysosomes disappeared from the surface epithelium they changed in character. They became more electron-lucent and revealed a fine-fibrillar matrix. Dense bodies deep in the cell interior appeared to communicate with each other and with the extracellular space below the surface epithelium. Openings were never seen towards the peritoneal cavity. The loss of lysosomal content from the apical surface epithelium before follicle rupture appeared in many respects similar to the histamine release process in mast cells.The findings support our working hypothesis that the surface epithelium over Graafian follicles is an essential source of proteolytic enzymes and that these may be released extracellularly and actively contribute to the dissolution of the follicular apex before rupture.This investigation was supported by grants from the Swedish Medical Research Council (Projects No. B74-12X-78-09C and B75-12X-78-10A). The technical assistance of Miss Ingalis Fransson and Miss Kerstin Nilsson is greatly appreciated     

Fine structural demonstration of acid phosphatase in rabbit germinal epithelium prior to induced ovulation

The germinal or surface epithelium covering rabbit Graafian follicles contains occasional small, dark, lysosome-like bodies. After an ovulatory dose of human chorionic gonadotropin (HCG) such bodies gradually increase in size and number. At 8 hr after HCG there is a maximal accumulation in the apical follicle cells; then the dense bodies decrease and just prior to ovulation, 9.5 hr after HCG, only few of them remain in the attenuated surface epithelium. Most of the growing membrane-surrounded bodies probably represent lysosomes, since electron microscopy combined with cytochemistry revealed that many of them contain the lysosomal "marker" enzyme, acid phosphatase. The role of sex steroids and prostaglandins regarding lysosomal growth and LABILization is discussed. The close temporal relation between disappearance of the apical surface epithelial lysosomes and disintegration of the underlying tunica albuginea gives further support to our working hypothesis that at least part of the "ovulatory enzymes" emanate from the surface epithelium.     

Histochemical and ultrastructural features of the lingual epithelium of the rat snake (Elaphe climacophora)

The histological, ultrastructural and histochemical characteristics of the lingual epithelium of the rat snake (Elaphe climacophora) were investigated by light and transmission electron microscopy. The cells in the beta-layer of the epithelium of the bifurcated apex were filled with beta-keratin fibers and an amorphous matrix. Round projections covering the surface of the epithelial cells, namely, microfacets which contained pale granules, were clearly visible on the outer faces of Oberh?utchen cells on the epithelium, and they were identified as fine granules filled with lipid. These granules might play an important role as a coating on the surface of the bifurcated lingual apex. The lipid on the surface of the lingual apex might also serve to trap and retain odorant molecules. Keratohyalin-like granules were distributed within the a-layer of the epithelium of the bifurcated apex of the tongue in the resting phase and cellular interdigitation was well developed in this region. Evidence of a shedding line was apparent under the light microscope in the cleft between outer and inner epithelial generations. The epithelial surface of the body of the tongue appeared suitable for retention of odorant and other molecules.     

The histochemistry of complex carbohydrates in the epithelium lining the ventral prostate of the rat

Summary In the epithelium lining the ventral prostate of the rat, complex carbohydrate-containing structures have been studied by means of both light and electron microscopic histochemical methods. According to light microscopy, the free surface and granules of different sizes in the distal cytoplasm of the epithelial cells were found to exhibit positive reactions for complex carbohydrates with 1,2-glycol and acidic groups and sialic acid residues. In addition, secretory substances within the glandular lumen were shown to exhibit positive reactions for similar groups and saccharide residues of complex carbohydrates. In electron microscopy, the surface coat of the plasma membrane, certain elements of the Golgi apparatus and lysosomal dense bodies were found to exhibit positive reactions for glycoproteins with 1,2-glycol groupings. The histophysiological significances of the carbohydrate-containing structures have been discussed with special reference to the known physiological functions of the prostate in the rat.     

Ultrastructural, histochemical and cytochemical characterization of intestinal epithelial cells in Aplysia depilans (Gastropoda, Opisthobranchia)

To improve the current knowledge about the digestive system in opisthobranchs, light and electron microscopy methods were used to characterize the epithelial cells in the mid‐intestine of Aplysia depilans. This epithelium is mainly formed by columnar cells intermingled with two types of secretory cells, named mucous cells and granular cells. Columnar cells bear microvilli on their apical surface and most of them are ciliated. Mitochondria, multivesicular bodies, lysosomes and lipid droplets are the main components of the cytoplasm in the region above the nucleus of these cells. Peroxisomes are mainly found in middle and basal regions, usually close to mitochondria. Mucous cells are filled with large secretory vesicles containing thin electron‐dense filaments surrounded by electron‐lucent material in which acidic mucopolysaccharides were detected. The basal region includes the nucleus, several Golgi stacks and many dilated rough endoplasmic reticulum cisternae containing tubular structures. The granular cells are characterized by very high amounts of flat rough endoplasmic reticulum cisternae and electron‐dense spherical secretory granules containing glycoproteins. Enteroendocrine cells containing small electron‐dense granules are occasionally present in the basal region of the epithelium. Intraepithelial nerve fibres are abundant and seem to establish contacts with secretory and enteroendocrine cells.     

Segregation of Ferritin in Glomerular Protein Absorption Droplets

Ferritin was used as a tracer to study the mechanism by which proteins are segregated into droplets by the visceral epithelium of glomerular capillaries. In glomeruli from both normal and aminonucleoside-nephrotic rats ferritin molecules introduced into the general circulation penetrated the endothelial openings and were seen at various levels in the basement membrane. Striking differences between nephrotic and controls were seen only in the amount of ferritin incorporated into the epithelium. In normal animals, a few ferritin molecules were seen in small invaginations of the cell membrane limiting the foot processes, within minute vesicles in the epithelium, or within occasional large vacuoles and dense bodies. In nephrotics, epithelial pinocytosis was marked, and numerous ferritin molecules were seen within membrane invaginations and in small cytoplasmic vesicles at all time points. After longer intervals, the concentration of ferritin increased in vacuoles and particularly within the dense bodies or within structures with a morphology intermediate between that of vacuoles and dense bodies. In nephrotic animals cleft-like cavities or sinuses were frequently encountered along the epithelial cell surface facing the urinary spaces. Some of these sinuses contained material resembling that filling the dense bodies except that it appeared less compact. The findings suggest that ferritin molecules—and presumably other proteins which penetrate the basement membrane—are picked up by the epithelium in pinocytotic vesicles and transported via the small vesicles to larger vacuoles which are subsequently transformed into dense bodies by progressive condensation. The content of the dense bodies may then undergo partial digestion and be extruded into the urinary spaces where it disperses. The activity of the glomerular epithelium in the incorporation and segregation of protein is similar in normal and nephrotic animals, except that the rate is considerably higher in nephrosis where the permeability of the glomerular basement membrane is greatly increased.     

Electron microscopic study on the epiplexus (Kolmer) cells of the cat choroid plexus

Summary A light and electron microscopic study was made of the epiplexus (Kolmer) cells of the cat choroid plexus. These polymorphic, motile cells were typically found juxtaposed to the ventricular surface of the choroidal epithelium. They have many ultrastructural features in common with free macrophages of other systems, namely, an indented nucleus with condensed chromatin, sparse mitochondria and endoplasmic reticulum, free ribosomes, multiple Golgi elements, microtubules, coated surface invaginations and microvesicles, and numerous membrane-limited vacuoles and lysosomal dense bodies. A unique feature of epiplexus cells is the manner in which they are anchored to the choroidal epithelium by the invagination of their surfaces by epithelial cell microvilli and cilia.Electron dense tracer particles (biological India ink, Thorotrast, ferritin) injected into the cerebral ventricles were ingested rapidly by epiplexus cells. Uptake of the particles was by way of coated surface invaginations which produced coated cytoplasmic microvesicles. Particle-containing microvesicles subsequently fused with each other and presumably also with pre-existent cytoplasmic vacuoles and lysosomal dense bodies to form storage vacuoles (phagosomes phagolysosomes and residual bodies).Present evidence suggests that epiplexus cells are of hematogenous origin. Under certain conditions these cells may detach from the surface of the choroid plexus to become free-floating cells in the various cerebrospinal fluid compartments of the brain.This investigation was supported by USPHS research grants 1-K04 HD20871, 5 R01 HD 02616 and NB-04456.     

Fine structure of the dorsal lingual epithelium of the lizard, Gekko japonicus (Lacertilia, Gekkonidae)

Three different types of lingual papilla were observed by scanning electron microscopy on the dorsal lingual epithelium of the lizard Gekko japonicus. Dome-shaped lingual papillae were located at the apex. Flat, fan-shaped lingual papillae were seen in the widest area of the lingual body. Long, scale-like lingual papillae were arranged on the latero-posterior dorsal surface. At higher magnification, microvilli and microridges were seen to be widely distributed over the surface of the papillae. By light microscopy, the epithelium of the dome-shaped papillae was composed of single, columnar epithelial cells filled with secretory granules. The tip of the epithelium of the fan-shaped and scale-like papillae was composed of stratified squamous epithelial cells without granules. The major part of the epithelium of these two types of papilla, except the tip area, was also composed of single, columnar epithelial cells with secretory granules. By transmission electron microscopy, a nucleus without a defined shape was seen to be located in the basal part of each of the single, columnar epithelial cells. Rough-surfaced endoplasmic reticulum and Golgi apparatus were well developed around the nucleus. The other, major part of the cytoplasm was filled with the spherical secretory granules, a large number of which had very electron-dense cores and moderately electron-dense peripheral regions. In the stratified squamous epithelium, a nucleus, which tended to be condensed on the free-surface side, was located in the center of each cell. Mitochondria, endoplasmic reticulum, and vesicles were observed in the cytoplasm.     

A histological and ultrastructural investigation of the female reproductive system of the water snake (Erythrolamprus miliaris): Oviductal cycle and sperm storage

We studied the structural and cellular organisation of the oviduct of Erythrolamprus miliaris including its morphological variation during the reproductive cycle using light microscopy, scanning electron microscopy and transmission electron microscopy. Four anatomically distinct regions compose the oviduct of E. miliaris including the anterior and posterior infundibulum, glandular uterus, non-glandular uterus and pouch. The cells of the oviductal epithelium secrete material by apocrine and merocrine processes, which vary between the anatomical regions and according to each phase of the reproductive cycle. The infundibular epithelium secretes electron dense vacuoles, which suggests the production of lipids, whereas the epithelial secretion of the glandular uterus, non-glandular uterus and pouch creates lucent and slightly electron dense vacuoles, indicating the production of glycoproteins. The timing of mating, vitellogenesis and sperm storage directly influences the morphofunctional alterations in the oviducts of E. miliaris. Sperm storage occurs only in the infundibular receptacles with increased production of the neutral carbohydrates in the presence of male gametes. Sperm storage happens in vitellogenic, non-vitellogenic and pregnant females of E. miliaris. Thus, females may be able to produce multiple clutches at different seasons of the year regardless of mating during autumn.     

Fine structure of the seminal vesicle epithelium of the mouse and golden hamster

The seminal vesicle epithelium of the mouse and golden hamster was examined by light microscopy and by transmission and scanning electron microscopy. By transmission electron microscopy, in the seminal vesicle epithelium of both animals secretory epithelial cells which consisted of mostly light and a few dark cells were observed. The epithelial cells possessed secretory granules which contained a densely stained core. The secretory granules in the mouse epithelium reacted weakly with periodic acid-Schiff (PAS) stain and were slightly stained with alcian blue (AB), and those in the golden hamster exhibited strongly positive reactions with PAS and AB. The nuclei in the mouse tissue were spherical or ovoid, and those in the golden hamster tissue had a few lobes. By scanning electron microscopy, the apical surfaces of most of the epithelial cells were commonly flat or domed, and those of some epithelial cells protruded into the lumen as apocrine-like processes, or possessed small and large orifices. Besides the epithelial cells, there were cells characterized by pseudopodium-like cytoplasmic projections, a few membranous structures, an irregular nucleus, and cytoplasm containing a few dense bodies, in the basal portions of the epithelial cells, or between the basal lamina and the epithelial cells. These cells of the two species were similar in their features.     

The ultrastructure of the spermatheca of Biomphalaria glabrata (gastropoda,pulmonata)

A study of the ultrastructure of the spermatheca of virgin freshwater snails Biomphalaria glabrata, kept in isolation since hatching, and in freely mating individuals maintained in colonies, shows that the spermatheca, an accessory organ of the female genital tract of pulmonate snails, is a pear-shaped blind pocket, lined with a single-layered columnar epithelium, surrounded by a thin muscle and pigmented connective. The apex of each epithelial cell may be ciliated, whereas the basis lies on a thick basement membrane. In virgin snails the spermatheca is smaller, its lumen contains a gelatinous, amorphous material; the apex of the epithelial cells contains many mitochondria but few granules. The nucleus appears in the basal third of the cell, topped by the Golgi complex and endoplasmic reticulum elements. In snails which have mated, the spermatheca is swollen, with a somewhat distended lower epithelium; its lumen contains numerous spermatozoa, in various degrees of degradation, which increases with the passage of time after copulation. The apex of the epithelial cells becomes very rich in granules with varied content, including multivesicular bodies. The latter are apparently exocytosed. Pinocytosis occurs at the base of microvilli. Glycogen can be seen accumulating in some cells. Tubular structures, ca. 60 nm in diameter, arranged regularly within the endoplasmic reticulum elements, could occasionally be seen at the basal part of the epithelial cells. It is suggested that the multivesicular bodies may contain enzymes which are secreted to the lumen. The partially digested sperm material would then be absorbed by micropinocytosis, and further digested in the secondary phagosomes at the apical portion of the epithelium.     

Ultrastructural analysis of the morphology and function of the spermatheca of the pulmonate slug Arion subfuscus

A study of the histology, histochemistry and ultrastructure of the spermatheca of Arion subfuscus in different stages of its life cycle shows that the spermatheca, an accessory organ of the femal genital tract of pulmonates, is a spherical-shaped organ lined with a columnar and non-ciliated epithelium surrounded by a thin network of connective tissue with some muscle fibres. The narrow epithelial cells possess numerous microvilli that, excepting young specimens, are provided with long, thin and generally curved, membranous process. Golgi apparatus, RER and mitochondria are abundant. Basal infolds are not very deep. In specimens killed two days after-copula, the spermatheca is swollen and its lumen is full of degenerating spermatozoa, mucus masses and spermatophore fragments. The apex of the cell is rich in granules with varied content, including multivesicular bodies. In specimens killed two weeks after-copula there are numerous endocytic vesicles in the apex and big vacuoles containing lipid. It is considered that after mating the excess of exogenous spermatozoa and copulatory seminal fluids are digested in the spermatheca. First, there is extracellular digestion that may be carried out by the enzymes contained in the multivesicular bodies exocytosed to the lumen, as well as by the enzymes secreted in apocrine vesicles. The partially digested materials would then be absorbed by endocytosis and further digested intracellularly. The great accumulation of lipid in the epithelial cells two weeks after mating suggest that the spermatheca could be involved in lipid synthesis, acting as a reserve organ.     

Microscopic and molecular characterization of ovarian follicle atresia in Rhodnius prolixus Stahl under immune challenge

In this work we characterized the degenerative process of ovarian follicles of the bug Rhodnius prolixus challenged with the non-entomopathogenic fungus Aspergillus niger. An injection of A. niger conidia directly into the hemocoel of adult R. prolixus females at the onset of vitellogenesis caused no effect on host lifespan but elicited a net reduction in egg batch size. Direct inspection of ovaries from the mycosed insects revealed that fungal challenge led to atresia of the vitellogenic follicles. Light microscopy and DAPI staining showed follicle shrinkage, ooplasm alteration and disorganization of the monolayer of follicle cells in the atretic follicles. Transmission electron microscopy of thin sections of follicle epithelium also showed nuclei with condensed chromatin, electron dense mitochondria and large autophagic vacuoles. Occurrence of apoptosis of follicle cells in these follicles was visualized by TUNEL labeling. Resorption of the yolk involved an increase in protease activities (aspartyl and cysteinyl proteases) which were associated with precocious acidification of yolk granules and degradation of yolk protein content. The role of follicle atresia in nonspecific host-pathogen associations and the origin of protease activity that led to yolk resorption are discussed.     

The ultrastructure of the rabbit oocyte at the bilaminar follicle stage]

The electron microscope study of the nucleus and organoids of the rabbit oocytes cytoplasm during growth showed nucleoluslike bodies (RNP-granules) on the lampbrushen chromosomes to reach their maximal size at the stage of bilaminar follicle. The RNP-granules differ from the nucleoli by the time of their occurrence cytochemical characteristics, and by their ultrastructural pattern. Throughout the bilaminar follicle stage four components may be seen in the oocyte nucleolus: a dense fibrillar framework around the vacuoles, islets of the granular mass loosely dispersed, and electron dense fibrillar elements filling up the numberous electrontransparant vacuoles. The nucleolus-like bodies are round in shape and have no vacuoles, consisting to two components only: distinctly outlined granules, and weakly developed fibrillar component. The nuclear envelope is seen blebbing. Separation of two nuclear membranes forms a pocket-like enlargements of the perinuclear space. The pockets are limited by small regions between the adjacent nuclear pores. The outer membrane may bulge producing lacuma and large channels in the cytoplasm, which are interconnected making a closed branched network extending inside of the cytoplasm. The nuclear envelope is suggested to be involved in formation of the endoplasmic reticulum through the blebbing process.     

Light and electron microscopic observations of fabrication, release, and fate of biphasic secretion granules produced by epididymal epithelial principal cells of the fan-throated lizard Sitana ponticeriana cuvier

The epididymis of the fan-throated lizard Sitana ponticeriana was examined with light and transmission electron microscopy to understand the cellular mechanisms of fabrication of secretion granules in epithelial principal cells, granule release into the lumen, and the fate of the dense structured granules after reaching the lumen. Principal cells of the ductus epididymis, except at the cauda, secrete electron-dense biphasic granules copiously, which decrease in abundance from the initial segment to corpus. The principal cell possesses a prominent Golgi apparatus and all versions of endoplasmic reticulum (ER), rough, smooth, and sparsely granulated. The material of the dense portion of the secretion granules, after processing at the Golgi apparatus, appears to accumulate in large ER cisternae in the supranuclear cytoplasm. It undergoes condensation when the cisternae become condensing vacuoles. Mitochondria appear to play a role in dense granule formation. The condensing vacuoles are displaced toward the apical cytoplasm when the material of the less dense portion is added to the condensing vacuoles at the Golgi area. Thus, the less dense and dense portions of the secretion granules are secreted and added to the condensing vacuoles separately. The composite granules are released into the lumen by exocytosis when the less dense portion merges with the luminal content, whereas the dense portion maintains its structured identity. The latter, initially measuring 1-2 microm in diameter, increases in size several times. It is inferred that these granules release their content gradually, resulting in the appearance of vacuoles, and suggesting that the granules have an insoluble matrix in which there is a sparingly soluble material. The substance leaching out of the granules appears to contribute to keeping the sperm quiescent and alive during storage in the male reproductive tract.     

Cytochemical demonstration of amine-storing vacuoles and lysosomes in the chicken thrombocytes

A combined electron microscopic and cytochemical study of the thrombocytes of the chicken has clearly identified the amine-storing organelles and lysosomes. A chromaffin positive-reaction product was observed on the inner surface and the granules of the large electron-lucent vacuoles. No acid phosphatase activity was localized in these amine-storing vacuoles. However, the acid phosphatase activity was observed in the small vesicles, the primary lysosomes, and in the large electron dense inclusions with myelin which may be secondary lysosomes. The results of this study suggest that the large empty vacuoles, with one or two very dense osmiophilic peripherally-situated granules, in the chicken thrombocytes are comparable to the vesicles with electron dense materials called "dense bodies" in mammalian thrombocytes.     

COMBINED CYTOCHEMICAL AND ELECTRON MICROSCOPIC DEMONSTRATION OF β-GLUCURONIDASE ACTIVITY IN RAT LIVER WITH THE USE OF A SIMULTANEOUS COUPLING AZO DYE TECHNIQUE

Rat liver was fixed in formal-cacodylate-sucrose and frozen sections were incubated in a simultaneous-coupling medium containing naphthol AS-BI glucuronide as substrate and hexazonium pararosanilin as the diazo reagent. By light microscopy, the sections demonstrated β-glucuronidase activity as red discrete granules in the pericanalicular cytoplasm and as a generalized cytoplasmic stain in the parenchymal cells. Brief treatment of sections in cold ethanol prior to incubation markedly enhanced the staining for the enzyme and made it possible to demonstrate sufficient amounts of the reaction product in sections embedded in epoxy resin following dehydration and propylene oxide treatment. Electron microscopy revealed that the reaction product was moderately electron opaque and deposited in greater amounts in the vacuolated dense bodies and occasionally in the dense bodies which did not show obvious vacuoles. In each dense body, the deposits occurred preferentially at the edge as well as in the area surrounding the vacuoles in the matrix. Control sections incubated in the presence of glucosaccharo-1:4-lactone were devoid of the reaction product. No deposits of the reaction product were found in the nucleus, mitochondria, or microbodies. The limitations of the present cytochemical technique for use in electron microscopy are briefly discussed.     

Histochemical and ultrastructural changes in the haustorium of date (Phoenix dactylifera L.)

Summary During imbibition ofPhoenix dactylifera embryos, all cotyledon cells show the same changes: protein and lipid bodies degrade, smooth endoplasmic reticulum (ER) increases in amount, and dictyosomes appear. At germination, the distal portion of the cotyledon expands to form the haustorium. At this time, epithelial cells have a dense cytoplasm with many extremely small vacuoles. Many ribosomes are present along with ER, dictyosomes, and mitochondria. The parenchyma cells have large vacuoles and a small amount of peripheral cytoplasm. Between 2 and 6 weeks after germination, epithelial cells still retain the dense cytoplasm and many organelles appear: glyoxysomes, large lipid bodies, amyloplasts, large osmiophilic bodies, and abundant rough and smooth ER which appear to merge into the plasmalemma. A thin electron-transparent inner wall layer with many small internal projections is added to the cell walls. Starch grains appear first in the subsurface and internal parenchyma and subsequently in the epithelium. Lipid bodies, glyoxysomes, protein, and osmiophilic bodies occur in the epithelial and subepithelial cell layers but not in the internal parenchyma. At 8 weeks after germination, the cytoplasm becomes electron transparent, vacuolation occurs, lipid bodies and osmiophilic bodies degrade, and the endomembranes disassemble. After 10 weeks, the cells are empty. These data support the hypothesis that the major functions of the haustorium are absorption and storage.