Body Granulation Research Articles

Investigation of the features of crystallization of granules of high-strength aluminum alloys of the Al-Zn-Mg-Cu system at ultra-high cooling rates

The article presents the results of studies of the process of obtaining granular materials from high-strength aluminum alloys of the Al - Zn - Mg - Cu system by centrifugation of the melt with ultra-high cooling rates of granules. The concept of a «steam jacket» is introduced, namely, a steam layer that occurs between the granule body and the cooling liquid, which prevents the intensity of heat removal and is an obstacle to increasing the crystallization rate due to the lower thermal conductivity of water vapor. It is established that the formation of a vapor layer always occurs due to the heating of the cooling liquid in contact with the melt drop to boiling temperatures and the transition of the cooler from the liquid phase to steam. The technology of increasing the rate of crystallization of granules due to the constant removal of the vapor layer is proposed. The removal (knocking down) of the vapor shell that occurs around the drop occurs due to the high speed of the drop movement in the cooling medium. Fundamentally important in the industrial implementation of this technology is not so much the design of the device for obtaining pellets by centrifugation of the melt, namely, the high required rotation speed of the spraying crucible of the device under consideration. The results of experimental data are presented to determine the necessary rotation speed of the perforated cup, which ensures the creation of a sufficient initial velocity of the drop movement, leading to a constant churning of the «steam jacket». It is determined that an increase in the rates of heat removal from the crystallized granules and, as a result, an increase in the crystallization rate leads to an increase in the strength characteristics of granular aluminum alloys of the Al-Zn-Mg-Cu system. In particular, in the production of pressed semi-finished products from alloys of the Al-Zn-Mg-Cu system, such as B95, B96c. the increase in the strength characteristics of the material of the press products is up to 15 % compared to the same granular materials obtained by traditional methods with industrial crystallization rates of melt droplets. It is established that this method, based on the removal of the vapor layer around the formed granule, is the only possible one for further increasing the cooling rate and, as a result, the crystallization rate. Reducing the size of granules to the size of powders leads to serious technological problems in the further consolidation of granules and, in fact, is a dead end branch of the further development of granulation methods.

The phases that separate RNA and transcription

RNA‐binding proteins recruited to nascent transcripts have the ability to regulate transcription and to spontaneously assemble into granule bodies through a process referred to as phase separation. These proteins, such as FUS (Fused in sarcoma) and EWS (Ewing sarcoma related 1), are endowed with these two abilities through domains that have low‐complexity amino acid sequences and are intrinsically disordered. Despite recent progress dissecting the biophysical principles underlying protein phase separation, its contribution to RNA‐processing and transcription has remained obscure. We have found that these proteins do assemble into granules that are associated with RNA polymerase II in cells. The formation of these granules and their association with the polymerase is dependent on transcription activity itself. Surprisingly, when transcription and phase separation is recombined in vitro, we have uncovered that at least one such protein, FUS, not only affecting transcription through its direct interactions with the transcription machinery but also by sequestering RNA structures that can hinder progress of the polymerase. Taken together, the role these proteins play and their peculiar RNA‐binding and phase separating properties provide a sophisticated mechanism to concentrate transcription and RNA‐processing machinery at genes and possibly to coordinate crosstalk between transcription and the maintenance of chromosome integrity.Support or Funding InformationNational Institutes of Health (NIH), American Cancer Society (ACS)Figure 1

Vacuolar degradation of chloroplast components: autophagy and beyond.

Chloroplast degradation during natural or stress-induced senescence requires the participation of both plastidic and extraplastidic degradative pathways. As part of the extraplastidic pathways, chloroplasts export stroma, envelope, and thylakoid proteins in membrane-bound organelles that are ultimately degraded in vacuoles. Some of these pathways, such as the formation of senescence-associated vacuoles (SAVs) and CV-containing vesicles (CCVs), do not depend on autophagy, whereas delivery of Rubisco-containing bodies (RCBs), ATI1-PS (ATG8-interacting Protein 1) bodies, and small starch-like granule (SSLG) bodies is autophagy dependent. In addition, autophagy of entire chloroplasts delivers damaged chloroplasts into the vacuolar lumen for degradation. This review summarizes the autophagy-dependent and independent trafficking mechanisms by which plant cells degrade chloroplast components in vacuoles.

Spray freeze granulation of submicron alumina and its sintering behavior via spark plasma sintering

Spray freeze granulation is an improved method based on spray granulation, solving many limitations of spray granulation. In this work, spray freeze granulation of submicron alumina is performed to explore the possibility of industrial-scale production of dense alumina via spark plasma sintering. Powder pretreatment such as sedimentation and the selection of granules with the appropriate size are employed for the maximum use of the high qualified as-prepared granules and granule sliding, which would provide a guidance for the industrial-scale production. Debound granules were densified via SPS and the corresponding sintering behaviors such as the recorded shrinkage and shrinkage rate were discussed. The comparison of sintering behaviors between granulated and as-received powder are conducted to identify the role of spray freeze granulation in sinterability for dense alumina. The Vickers hardness (Hv) and the fracture toughness (KIC) of the freeze granulated body are higher than the corresponding properties of the as-received body due to the more homogenous microstructure with little agglomeration in the particle packing after freeze granulation.

Characteristics of the adsorbed heavy metals onto aerobic granules: isotherms and distributions

Biosorption experiments were performed using aerobic granules as bioadsorbent for Cd2+, Cu2+, Mn2+, Zn2+, Fe2+, and Co2+. Aerobic granule shows high adsorption capacity [Qe (mg/g) = 189 − 232]. Both Langmuir and Freundlich isotherm fitted the adsorption data well. Especially, the R2 value exceeds 0.96 in most cases when Langmuir model was adopted. In order to look into the distribution of the adsorbed heavy metal in aerobic granules and to verify metal uptake in surface layer, in middle zone and center of aerobic granule, energy dispersive X-ray (EDX) spectra were obtained. According to field emission scanning electron microscope-EDX observation, it was found that whole granule body can act as an active site for heavy metals uptake because of a lot of pore existed in the inside of aerobic granule. It is clear that the penetration of dissolved metal solution to the center of aerobic granule has occurred, which confirms that metal uptake can occur even in the center of aerobic granule. The analyses by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy showed that functional groups on aerobic granules, such as alcoholic, carboxylate and ether, would be the main binding sites for biosorption of heavy metals. The area distributions further reveal that ether and alcoholic would be the dominant carbon forms in aerobic granules, and the interaction and coordination affinity between the functional groups and metals would be more complicated than expected.

Expression of MAEL in nuage and non-nuage compartments of rat spermatogenic cells and colocalization with DDX4, DDX25 and MIWI

The functions of MAELSTROM protein (MAEL) in spermatogenesis are gradually being identified but the precise distribution of MAEL in spermatogenic cells during spermatogenesis has not yet been mapped. We studied the expression of MAEL in rat testis by immunofluorescence and immunoelectron microscopy (IEM). Immunofluorescence staining showed thatMAEL was localized in intermitochondrial cement, irregularly-shaped perinuclear granules and satellite bodies of pachytene spermatocytes, and in chromatoid bodies of spermatids. The SBs appeared exclusively in pachytene spermatocytes at stages IX-X and were stained strongly for MAEL. In step 12-19 spermatids, many granules stained for MAEL but not DDX4. These granules were confirmed to be non-nuage structures, including mitochondria-associated granules, reticulated body, granulated body by IEM. In the neck region of late spermatids and sperm, MAEL-positive small granules were found. MAEL is colocalized with MIWI in nuage and non-nuage. The results suggest that MAEL seems to function in nuage and non-nuage structures and interacts with MIWI.

Expression and Localization of NANOS1 in Spermatogenic Cells during Spermatogenesis in Rat

Expression and localization of NANOS1 in the spermatogenic cells of rat testis were studied by immunofluorescence and immunoelectron microscopy. Using immunofluorescence techniques, NANOS1 was localized in the cytoplasm and discrete granules of spermatocytes and spermatids. The staining intensity of NANOS1 signal varied depending upon the stage of the cycle of seminiferous epithelium. Double immunofluorescence staining with antibodies against NANOS1 and DDX4 showed that several DDX4-positive compartments of nuage were also stained for NONOS1. Immunoelectron microscopy revealed that the major subcellular localization sites for NANOS1 were the chromatoid body (CB) and satellite body (SB), and the minor sites were the rest of the nuage compartments, including the irregularly-shaped perinuclear granules (ISPG), and intermitochondrial cement (IMC). Non-nuage structures such as mitochondria-associated granules (MAG), granulated body (GB), and reticulated body (RB) were also labeled by theNANOS1 antibody. In addition, NANOS1 was found in the outer dense fibers of flagella of spermatids at steps 12-19, and in the head cap of late spermatids after step 15. These results suggest that NANOS1 is one of the nuage proteins and functions mainly in the CBs as well as in the cytoplasm. NANOS1 may also have additional functions in non-nuage structures such as MAGs, GBs and RBs.

Localization of BRUNOL2 in Rat Spermatogenic Cells as Revealed by Immunofluorescence and Immunoelectron Microscopic Techniques

Distribution and localization of a RNA-binding protein, BRUNOL2 in rat spermatogenic cells were studied by dot blotting of cell fractions, immunofluorescence (IF), and immunoelectron microscopy (IEM). BRUNOL2 distributed in nuclear (23%), mitochondrial (19%), microsomal (15%), and cytosol fractions (43%). BRUNOL2 was detected in all spermatogenic cells. In the cytoplasm and nucleoplasm of the spermatogonia, spermatocytes and spermatids, both diffuse and granular staining patterns were observed. Many cytoplasmic granules were stained also for DDX4 and DDX25. Large granules in the cytoplasm of elongated spermatids were stained for BRUNOL2 but not for the nuage proteins. IEM showed that gold signals for BRUNOL2 were concentrated in nuage components including loose aggregates of small particles, chromatoid body (CB), intermitochondrial cement (IMC), and satellite body (SB). In addition, many non-nuage structures such as ER-attached small granules, less dense material surrounding connecting piece of flagellum, reticulated body, mitochondria-associated granules (MAG), granulated body, ribosome aggregate, and manchette, were stained for BRUNOL2 with different staining intensities. In the nucleus, gold signals were concentrated in heterochromatin area and nucleolus. The results suggest that BRUNOL2 is one of the nuage proteins and also associated with the other non-nuage structures, suggesting multiple functions of this protein.

Expression of DDX25 in nuage components of mammalian spermatogenic cells: immunofluorescence and immunoelectron microscopic study

The localization of DDX25/GRTH and gonadotropin-stimulated RNA helicase was studied in the spermatogenic cells of rat, mouse, and guinea pig by immunofluorescence and immunoelectron microscopy (IEM). Immunofluorescence studies identified four kinds of granular staining: (1) fine particles observed in meiotic cells; (2) small granules associated with a mitochondrial marker, appearing in pachytene spermatocytes after stage V; (3) short strands lacking the mitochondrial marker in late spermatocytes; and, (4) large irregularly shaped granules in round spermatids. IEM identified DDX25 signals in nine compartments: (1) fine dense particles in the meiotic cells; (2) intermitochondrial cement; (3) loose aggregates of 70-90 nm particles; (4) chromatoid bodies; (5) late chromatoid bodies; (6) satellite bodies; (7) granulated bodies; (8) mitochondria-associated granules; and, (9) reticulated bodies. Compartments (1) to (6) were previously classified into nuage while (7) to (9) were classified as nuage components by the present study. The results suggest that DDX25 functions in these nine compartments.

Oogenesis and spermatogenesis in Paraleucilla magna (Porifera, Calcarea)

Gametogenesis in Calcarea is still poorly known; therefore, in this work, we describe the gametogenesis of Paraleucilla magna (Porifera, Calcarea) using light and electron microscopy. Male and female gametes derived from choanocytes. Oocytes grew inside a follicle-like structure composed of pinacocyte-like cells and choanocytes. They were nourished through nutrient transfer from nurse cells and through bacteria phagocytosis, which was never documented for a calcarean species. Mature oocytes were typical, spherical, with nucleolated nuclei and a cytoplasm filled with different types of inclusions and digestive vesicles. Nuage was also found. Spermatogenesis occurred in the lumen of differentiated choanocyte chambers, and spermatic cysts were never formed. Spherical spermatogonia without flagellum or collar were derived from hourglass-shaped primordial germ cells. Spermatozoa were of the ‘aberrant type’, showed a compact electron-dense nucleus and a homogeneous granulated body in its cytoplasm. The gametogenesis of P. magna is similar to what has been observed for other Porifera and Eumetazoa.

Ancinus jarocho (Isopoda: Sphaeromatidea: Ancinidae), a new species from the central Gulf of Mexico, Mexico

Ancinus jarocho n. sp. described from mesolittoral zone of sandy beaches in Veracruz State, Mexico, is the eighth species of the genus and the second record for the Gulf of Mexico coast. The new species is characterized by an antennular flagellum of 11–16 articles, single aesthetasc in 9 distal flagellar articles, uropodal endopod styliform, lightly arched and shortest than pleotelson, male pleopod 5 exopod with the distomesial margin serrated, with minutes spines. Ancinus jarocho n. sp. is morphologically similar to A. granulatus, which has a truncate pleotelson apex, densely granulated body surface and eyes on elevated swellings.

Occurrence and formation of cytoskeletal proteins in mammalian spermatozoa.

Mammalian spermatozoa are composed of specialized cytoskeletal elements, which appear to have no structural or protein counterparts in somatic cells. Most evident are the outer dense fibres (ODF) and fibrous sheath (FS) of the sperm tail and the perinuclear theca (PT) of the sperm head. The purpose of this study is to review our results on the occurrence and assembly of proteins making up these three elements during spermatogenesis. Our approach was to raise antibodies against the prominent proteins of these elements and to immunolocalize them on testicular sections prepared for histological and ultrastructural analyses. We found that all of the cytoskeletal proteins considered were expressed exclusively during the haploid phase of development and that the proteins of each element had similar if not identical patterns of expression. The PT proteins were synthesized in the first half of spermiogenesis and were associated with acrosome formation, while the ODF and FS proteins were synthesized in the second half of spermiogenesis. The ODF proteins assembled in a proximal-distal direction along the length of the axoneme, while the FS proteins assembled in the opposite direction; both assemblies eventually meeting and overlapping within the periaxonemal cytoplasmic compartment. During assembly the ODF proteins appeared to be temporarily stored in granulated bodies of the cytoplasmic lobe, while the FS proteins were randomly distributed throughout the cytoplasm. In the case of the PT, there appeared to be an interdependence between PT assembly and acrosome formation. The developmental protein distribution patterns observed for each of the elements suggest unique cellular targeting mechanisms adapted by the spermatid to regulate the assemblies of the respective cytoskeletal proteins.

Cellular and subcellular localization of kainic acid in the marine red alga Digenea simplex

Polyclonal antibodies specific for the excitatory amino acid, kainic acid (KA), were raised in rabbits. The antibody recognized KA but did not cross-react with other structurally related amino acids, including glutamate. We used this anti-KA antibody to localize KA immunohistochemically in the KA-producing red alga Digenea simplex. KA immunoreactivity was most dense in the fine cylindrical thallus, which covers the middle to upper part of the alga. The cortical cells, but not the inner layers of the main axis, and cells of the rhizoid were also stained with this antibody. The presence of KA in cells that cover the surface of the alga might reflect its role in chemical defense. At the subcellular level, KA immunoreactivity was most intense in the nucleus, pit plugs, and the electron-dense areas denoted as "granule bodies", which were found only in the pericentral cells of the thallus.

Spatiotemporal changes of levels of a moonlighting protein, phospholipid hydroperoxide glutathione peroxidase, in subcellular compartments during spermatogenesis in the rat testis.

We studied temporal changes in the subcellular localization and levels of a moonlighting protein, phospholipid hydroperoxide glutathione peroxidase (PHGPx), in spermatogenic cells and mature sperm of the rat by immunofluorescence and immunoelectron microscopy. The PHGPx signals were detected in chromatoid bodies, clear nucleoplasm, mitochondria-associated material, mitochondrial aggregates, granulated bodies, and vesicles in residual bodies in addition to mitochondria, nuclei, and acrosomes as previously reported. Within mitochondria, PHGPx moved from the matrix to the outermost membrane region in step 19 spermatid, suggesting that this spatiotemporal change is synchronized with the functional change of PHGPx in mitochondria. In the nucleus, PHGPx was associated with electron-lucent spots and with the nuclear envelope, and PHGPx in the latter region increased after step 16. In early pachytene spermatids, PHGPx signals were noted in the nuclear material exhibiting a very similar density to chromatoid bodies and in the intermitochondrial cement, supporting the previous proposal that chromatoid bodies originate from the nucleus and intermitochondrial cement. The presence of PHGPx in such various compartments suggested versatile roles for this protein in spermatogenesis. Quantitative immunoelectron microscopic analysis also revealed dynamic changes in the labeling density of PHGPx in different subcellular compartments as follows: 1). Total cellular PHGPx rapidly increased after step 5 and reached a maximum at step 18; 2). mitochondrial labeling density increased after step 1 and achieved a maximum in steps 15-17; 3). nuclear labeling density suddenly increased in steps 12-14 to a maximum; 4). in cytoplasmic matrix, the density remained low in all steps; and 5). the labeling density in chromatoid bodies gradually decreased from pachytene spermatocytes to spermatids at step 18. These spatiotemporal changes in the level of PHGPx during the differentiation of spermatogenic cells to sperm infer that PHGPx plays a diverse and important biological role in spermatogenesis.

Fracture toughness of bone china and hard porcelain

The fracture toughness of unglazed, commercial samples of bone china and hard porcelain produced by powder pressing spray dried granulated bodies has been determined using the Vickers indentation m...

Tpx-1 is a component of the outer dense fibers and acrosome of rat spermatozoa.

Previously we reported the cloning of a member of the cysteine-rich secretory protein family, tpx-1, from a testis expression library using an outer dense fiber (ODF)-specific antiserum. Using immunohistochemical and immunoelectron microscopic techniques and Western blotting of purified sperm tail components, we have determined that tpx-1 exists as 25 and 27 kDa proteins in two components of rat spermatid: the ODFs and the acrosome. Tpx-1 mRNA is first expressed in the late pachytene spermatocytes, but the production of these tpx-1 proteins is translationally delayed for 4-5 days before being incorporated into the developing sperm acrosome, surrounding the elongating and condensing spermatid nucleus. Concurrent with sperm head formation, tpx-1 protein was incorporated into the developing sperm tail, and specifically the ODFs. The tpx-1 protein was seen within structures resembling granulated bodies in the cytoplasmic lobe of elongating spermatids and was incorporated subsequently into the growing tail in a manner consistent with ODF development. In addition, tpx-1 protein was localized at the ultrastructural level of the connecting piece of the neck and longitudinal columns of the fibrous sheath, suggesting common protein components in these cytoskeletal structures. As such, tpx-1 may have functional significance in the processes of sperm head development and tail function.

Developmental Expression of the 84-kDa ODF Sperm Protein: Localization to both the Cortex and Medulla of Outer Dense Fibers and to the Connecting Piece

Outer dense fibers (ODF) are specialized cytoskeletal elements of the mammalian sperm tail which are composed of several prominent proteins. We previously reported the isolation of a cDNA (111-450) encoding a putative 84-kDa ODF protein. Here we demonstrate by independent cDNA isolations and by translational/immunoprecipitation of testicular mRNAs using anti-ODF 84 antibodies that 111-450 cDNA encodes the 84-kDa protein. We then analyzed the testicular expression of the ODF 84 mRNA and protein. Riboprobes generated from the clones recognized four testicular-specific transcripts of 1.6, 2.2, 2.4, and 2.8 kb in both rat and bull of which the immunoprecipitable product of the 2.4-kb mRNA comigrates with ODF 84 protein. Developmental Northerns indicated that the 2.2- and 2.4-kb mRNAs are first transcribed during meiotic prophase while the other two species are first expressed in round spermatids. The levels of all the transcripts steadily increased up to elongated spermatids. Immunocytochemistry revealed that the anti-84 reactive ODF proteins were synthesized and assembled in the cytoplasm of elongated spermatids (steps 9–18) with peak activity occurring in step 16 of spermiogenesis. Immunogold labeling was selective to the assembling ODF and connecting piece of the tail and to granulated bodies of the cytoplasmic lobe. Both the striated collar and capitulum of the connecting piece were immunolabeled as well as the basal plate of the implantation fossa. A combination of pre- and postembedding immunogold labeling provided evidence that the 84-kDa ODF protein is localized to both the cortex and medulla of the ODF in contrast to the sole medullary localization of the major 27-kDa ODF protein. Thus the 84-kDa ODF protein, encoded by the 2.4 transcript, is translationally regulated, packaged after synthesis into granulated bodies, assembled in a proximal to distal direction along the axoneme and may interact by means of leucine zippers specifically with the 27-kDa ODF protein during assembly. Its localization to both the cortex and medulla of the ODF, as opposed to exclusive medullary localization of the 27-kDa ODF protein, and the presence of two leucine zippers, only one of which interacts with the 27-kDa ODF, suggests that it could act as a link between proteins of the two regions of the ODF.

Cytoplasmic inclusions of astrocytic elements of glial tumors: special reference to round granulated body and eosinophilic hyaline droplets.

Round granulated body (RGB) and eosinophilic hyaline droplets (EHDs) have been described as cytoplasmic inclusions of certain astrocytic tumors. In the previous literature, however, these inclusions have been described using various terms or regarded as nosologically the same entity. Light microscopically, RGB appeared as a round discrete body filled with fine uniform granules, while EHDs demonstrated a cluster of bright eosinophilic, round objects of various size. They could be clearly distinguished even by conventional histochemical staining such as the Masson trichrome stain and the phosphotungstic acid hematoxylin preparation. Both RGB and EHDs expressed positive immunoreactions for glial fibrillary acidic protein, several lysosomal markers, and some stress-response proteins. The ultrastructural appearances of these inclusions were distinct, however, one common feature was that they consisted of aggregations of numerous membrane-bound electron-dense bodies. Thus, both inclusions appear to be produced by neoplastic astrocytes and are possibly related to the lysosomal system. We examined the presence of RGB and EHDs in 138 astrocytic tumors. Both inclusions occurred most frequently in pleomorphic xanthoastrocytomas, followed by gangliogliomas and pilocytic astrocytomas. Subependymal giant cell astrocytomas exhibited only RGBs. RGBs and EHDs were not seen in any abundance in glioblastomas, gliosarcomas, fibrillary astrocytomas, protoplasmic astrocytomas, or oligo-astrocytomas. Some glioblastomas, however, showed only EHDs in small numbers. Several anaplastic astrocytomas were associated with a large number of RGBs and/or EHDs, and they revealed only rare mitosis despite marked cellular pleomorphism. Although RGB and EHDs have different morphological features, the presence of these inclusions in abundance may represent either a degenerative change, a long-standing lesion, or an indolent growth of the astrocytic tumors.

Cytoplasmic inclusions of astrocytic elements of glial tumors: special reference to round granulated body and eosinophilic hyaline droplets

Cytoplasmic inclusions of astrocytic elements of glial tumors: special reference to round granulated body and eosinophilic hyaline droplets

Electron microscopy of the endometrium of camels in normal and some diseased conditions.

Ultrastructure of the camel's endometrium in normal and diseased conditions, was studied using the electron microscope. The samples were obtained from 6 normal uteri and 10 uteri with inflammatory lesions. Three ovaries of the latter 10 uteri showed ovarian cysts. All the animals were non-pregnant. No cyclic changes were taken in consideration because the camel is an induced ovulator animal. The surface and the glandular epithelium of the normal uteri consisted of one layer of tall columnar cells, resting on an undulating membrane. The free borders of cells showed microvilli, motile cilia and zeiotic blebs. Desmosomes and gap junctions were seen as means of connections between the neighboring cells. The nuclei were large, oval and situated in the lower half of the cells. Two types of mitochondria were seen. One type was small, rounded and dilated, and the other was large and elongated. Many lipid droplets and scanty glycogen granules were common findings in the normal cells. Granulated bodies similar to those described in the epithelium of the human uterus and containing acid phosphatase were found. Many other cytoplasmic organelles and granules were seen. The endometrial stroma consisted mainly of stromal cells of irregular shape, and collagen fibres. The collagen fibres were present in amounts larger than many other species. In the diseased uteri, the changes in the epithelium consisted mainly of hyperplasia of the cells and marked increase of all cytoplasmic inclusions and vacuoles. There was also marked increase in the number of the crossing lymphocytes through the epithelial layer. The collagen fibres of the stroma increased in amount and the stromal cells became similar in shape to the fibroblasts. A large number of mast cells as well as other types of inflammatory cells infiltrated the stroma. Non-specific bacterial infections were detected on bacteriological examination of the inflamed uteri. Neither bacteria nor other microbial agents could be seen ultrastructurally. In an uterus associated with ovarian cysts, the microvilli of its epithelium showed marked changes in their shape and length.