Cisternae Of Endoplasmic Reticulum Research Articles

The coagulating gland in the male greater cane rat (Thryonomys swinderianus): morphological and immunohistochemical features.

This study reveals the structure, ultrastructure and immunoexpression of oestrogen alpha and beta receptors (ERα and ERβ) in the coagulating glands of the greater cane rat. Gland samples from 15 adult male cane rats were processed for histological and ultrastructural studies while immunohistochemistry was also carried out. Coagulating gland in the cane rat is a paired, triangularly shaped, transparent gland weighing about 1 ± 0.48 g. Histologically, each secretory acinus is composed of folded mucosa surrounded by fibromuscular stroma. The simple columnar epithelium consists of principal cells at different stages of secretion evidenced by their apical blebs of various heights and occasional basal cells. Fine structure of the principal cells revealed the presence of apical blebs that contained secretory granules of varying electron-density, secretory vesicles and vacuoles on both their luminal surfaces and the lumen. While supranuclear cytoplasm contained Golgi apparatus with different cisternal arrangements, the infranuclear part is covered with dilated rough endoplasmic reticulum cisternae. Nuclei, apical bleb and stroma of secretory epithelium all showed positive immunostaining for ERα and ERβ. These findings revealed the prominence of apocrine secretion with no structural evidence of merocrine secretion and the uncommon ERα and ERβ distribution pattern in the coagulating gland of the cane rat.

Histological changes of the albino rat cerebellar cortex under the effect of different doses of tramadol administration

Background Tramadol hydrochloride is a centrally acting synthetic analgesic used to treat moderate to severe pain with a wide range of applications. Aim This study was designed to investigate the effect of tramadol on the histology of the cerebellar cortex in adult albino rats. Materials and methods Thirty adult male albino rats weighing about 200 g were used and divided into control and experimental groups. The latter group was subdivided into two subgroups (IIa and IIb). Rats of subgroup IIa and IIb were injected intraperitoneally with 0.7 and 1.8 mg as a single daily dose of tramadol solution for 2 weeks, respectively. Rats were killed after 2 weeks and decapitated. The cerebellum was removed and subjected to histological, immunohistochemical, and morphometric studies. Results Histological study of subgroup IIa showed mild distortion of Purkinje cells with destroyed mitochondria and cisternae of rough endoplasmic reticulum. Meanwhile, subgroup IIb showed Purkinje cells arranged in multilayer cells with obvious damage such as a small nucleus with an indented membrane. The granular layer contained small cells, most of which had lost their nuclei, whereas others showed condensed chromatin with a thin rim of cytoplasm. Results of inducible nitric oxide synthase reaction showed a moderately positive cytoplasmic reaction of granular and Purkinje cells in subgroup IIa. However, subgroup IIb showed a highly positive cytoplasmic reaction. Morphological study of the cerebellar layer thickness showed a significant decrease in the thickness of Purkinje and granular layers, with a significant increase in the thickness of the molecular layer in both experimental subgroups. The Purkinje cell count showed a significant decrease in its number in both experimental subgroups. Conclusion The results of this study provided evidence that tramadol intake exerts a neurotoxic effect on the cerebellar structure in an ascending manner according to the dose administered. Thus, the Ministry of Health should make efforts to control usage of this drug among teenagers and correct misconceptions about this medication.

Fascin - An actin binding and bundling protein in the testis and its role in ectoplasmic specialization dynamics.

In the mammalian testis such as in rats, a unique actin-rich cell-cell adherens junction (AJ) known as ectoplasmic specialization (ES) is found in the seminiferous epithelium. ES is conspicuously found between Sertoli cells near the basement membrane known as the basal ES, which together with tight junction (TJ), gap junction, and desmosome constitute the blood-testis barrier (BTB). The BTB, in turn, anatomically divides the seminiferous epithelium into the basal and the adluminal (apical) compartment. On the other hand, ES is also found at the Sertoli-spermatid interface known as apical ES which is the only anchoring device for developing step 8-19 spermatids during spermiogenesis. One of the most typical features of the ES is the array of actin microfilament bundles that lie perpendicular to the Sertoli cell plasma membrane and are sandwiched in-between the cisternae of endoplasmic reticulum and the Sertoli cell plasma membrane. While these actin filament bundles confer the adhesive strength of Sertoli cells at the BTB and also spermatids in the adluminal compartment, they must be rapidly re-organized from their bundled to unbundled/branched configuration and vice versa to provide plasticity to the ES so that preleptotene spermatocytes and spermatids can be transported across the immunological barrier and the adluminal compartment, respectively, during the epithelial cycle of spermatogenesis. Fascin is a family of actin microfilament cross-linking and bundling proteins that is known to confer bundling of parallel actin microfilaments in mammalian cells. A recent report has illustrated the significance of a fascin protein called fascin 1 in actin microfilaments at the ES, pertinent to its role in spermatogenesis (Gungor-Ordueri etal. Am J Physiol Endocrinol Metab 307, E738-753, 2004 (DOI:10.1152/ajpendo.00113.2014). In this Commentary, we critically evaluate these findings in light of the role of fascin in other mammalian cells, providing some insightful information for future investigations.

Transient Ca2+ depletion from the endoplasmic reticulum is critical for skeletal myoblast differentiation.

Endoplasmic reticulum (ER) stress is a cellular condition in which unfolded proteins accumulate in the ER because of various but specific causes. Physiologic ER stress occurs transiently during myoblast differentiation, and although its cause remains unknown, it plays a critical role in myofiber formation. To examine the mechanism underlying ER stress, we monitored ER morphology during differentiation of murine myoblasts. Novel ER-derived structures transiently appeared prior to myoblast fusion both in vitro and in vivo. Electron microscopy studies revealed that these structures consisted of pseudoconcentric ER cisternae with narrow lumens. Similar structures specifically formed by pharmacologically induced ER Ca(2+) depletion, and inhibition of ER Ca(2+) efflux channels in differentiating myoblasts considerably suppressed ER-specific deformation and ER stress signaling. Thus, we named the novel structures stress-activated response to Ca(2+) depletion (SARC) bodies. Prior to SARC body formation, stromal interaction molecule 1 (STIM1), an ER Ca(2+) sensor protein, formed ER Ca(2+) depletion-specific clusters. Furthermore, myoblast differentiation manifested by myoblast fusion did not proceed under the same conditions as inhibition of ER Ca(2+) depletion. Altogether, these observations suggest that ER Ca(2+) depletion is a prerequisite for myoblast fusion, causing both physiologic ER stress signaling and SARC body formation.

English

The histology and ultrastructure of thyroid gland of White Fulani (Zebu) cattle were examined during the postnatal developmental period to show if variations in morphology exist with age and in relation to tropical climate. Eight prepubertal and ten pubertal cattle of abattoir origin were used to carry out this study. Histologically, the thyroid consisted of well-developed capsule, interlobular connective tissue, follicular and parafollicular cells from prepubertal to pubertal age of 5 to 7 years. The follicular cells were cuboidal in prepubertal period with some variations, became predominantly columnar in pubertal age of 2 to 4 years and highly flattened cells were common in the older pubertal animals of  5 to 7 years. The colloid was observed in the lumen at all age and was PAS-positive with abundant peripheral vacuoles in the pubertal age of 2 to 4 years. Significant variations (pË‚0.05) in structure of the thyroids were observed at all age and the follicular size and number of follicles increased as the cattle matured. Follicular height was reduced significantly in the older pubertal cattle of 5 to 7 years. Ultrastructurally, the follicular cells showed highly dilated cisternae of rough endoplasmic reticulum which decreased with age. Flattened follicular cells seen in the older pubertal cattle contained few cytoplasmic organelles and microvilli. Apically placed pseudopods and blebs were commonly observed in the pubertal age of 2 to 4 years. Lysosomal bodies increased with age of development. The parafollicular cells were encountered frequently in the prepubertal age than in the older cattle. They consisted of numerous dense secretory granules which increased in number with age. The present results suggest an optimum thyroid function during the pubertal. Our findings would be useful in interpreting changes in thyroid morphology during experimental and pathological conditions.   Key words:  Cattle, postnatal thyroid, histology, ultrastructure.

Mapping intracellular diffusion distribution using single quantum dot tracking: compartmentalized diffusion defined by endoplasmic reticulum.

The crowded intracellular environment influences the diffusion-mediated cellular processes, such as metabolism, signaling, and transport. The hindered diffusion of macromolecules in heterogeneous cytoplasm has been studied over years, but the detailed diffusion distribution and its origin still remain unclear. Here, we introduce a novel method to map rapidly the diffusion distribution in single cells based on single-particle tracking (SPT) of quantum dots (QDs). The diffusion map reveals the heterogeneous intracellular environment and, more importantly, an unreported compartmentalization of QD diffusions in cytoplasm. Simultaneous observations of QD motion and green fluorescent protein-tagged endoplasmic reticulum (ER) dynamics provide direct evidence that the compartmentalization results from micron-scale domains defined by ER tubules, and ER cisternae form perinuclear areas that restrict QDs to enter. The same phenomenon was observed using fluorescein isothiocyanate-dextrans, further confirming the compartmentalized diffusion. These results shed new light on the diffusive movements of macromolecules in the cell, and the mapping of intracellular diffusion distribution may be used to develop strategies for nanoparticle-based drug deliveries and therapeutics.

7. Russell body gastritis – a lesser known chronic gastritis

Russell body gastritis (RBG) is an uncommon, chronic inflammatory condition consisting of a localised or diffuse collection of Russell bodies within the lamina propria of the stomach (usually antrum). Russell bodies are intracytoplasmic, eosinophilic globules of immunoglobulins (Igs) within plasma cells. They may be due to a secretory disorder, causing Ig to accumulate in the cisternae of the rough endoplasmic reticulum. The plasma cells of RBG are polyclonal (expressing kappa and lambda light chains). Russell body gastritis was first described in 1998 and there have been approximately 20 cases described to date. It causes nonspecific upper gastrointestinal symptoms such as dyspepsia, is often associated with Helicobacter pylori infection and usually resolves after elimination of the bacteria. In this case a 78 year old woman presented with anaemia and dyspepsia. At endoscopy she was found to have a large gastric antral ulcer, which on biopsy showed a moderate chronic inflammatory infiltrate with prominent Russell bodies in the lamina propria. The Russell bodies were positive for PAS, CD38, CD79a, Kappa and Lambda light chains, confirming their B-cell polyclonality. Importantly, they were negative for AE1/3, excluding signet ring cell carcinoma. Giemsa stain failed to reveal any H. pylori in this case and the symptoms resolved with treatment of her ulcer. RBG can only be diagnosed after exclusion of malignant conditions (haematological and signet ring cell carcinoma). It is often associated with H.pylori infection but more research is needed before the definite cause and long term effects are established.

Junctate boosts phagocytosis by recruiting endoplasmic reticulum Ca2+ stores near phagosomes.

Local intracellular Ca(2+) elevations increase the efficiency of phagocytosis, a process that is essential for innate and adaptive immunity. These local Ca(2+) elevations are generated in part by the store-operated Ca(2+) entry (SOCE) sensor STIM1, which recruits endoplasmic reticulum (ER) cisternae to phagosomes and opens phagosomal Ca(2+) channels at ER-phagosome junctions. However, residual ER-phagosome contacts and periphagosomal Ca(2+) hotspots remain in Stim1(-/-) cells. Here, we tested whether junctate (also called ASPH isoform 8), a molecule that targets STIM1 to ER-plasma-membrane contacts upon Ca(2+)-store depletion, cooperates with STIM1 at phagosome junctions. Junctate expression in Stim1(-/-) and Stim1(-/-); Stim2(-/-) phagocytic fibroblasts increased phagocytosis and periphagosomal Ca(2+) elevations, yet with only a minimal impact on global SOCE. These Ca(2+) hotspots were only marginally reduced by the SOCE channel blocker lanthanum chloride (La(3+)) but were abrogated by inositol trisphosphate receptor inhibitors 2-APB and xestospongin-C, revealing that unlike STIM1-mediated hotspots, junctate-mediated Ca(2+) originates predominantly from periphagosomal Ca(2+) stores. Accordingly, junctate accumulates near phagosomes and elongates ER-phagosome junctions in Stim1(-/-) cells. Thus, junctate mediates an alternative mechanism for generating localized Ca(2+) elevations within cells, promoting Ca(2+) release from internal stores recruited to phagosomes, thereby boosting phagocytosis.

Cytochemical investigations of the megasporocyte and embryo sac in Lilium regale at various stages of development

During megasporocyte and embryo sac development in <i>Lilium regale</i>, characteristic changes were noted within the cytoplasm. In the course of prophase I there appear parallel systems of endoplasmic reticulum cisternae which further transform to cytoplasmic bodies built of protein and different-sized lipid inclusions. During maturation of the embryo sac the cytoplasmic bodies and lipid inclusions synthesized during prophase I undergo hydrolysis and constitute storage material utilized during maturation of the embryo sac.

Characterization of Russell bodies accumulating mutant antithrombin derived from the endoplasmic reticulum.

The endoplasmic reticulum (ER) adjusts its size and architecture to adapt to change in the surrounding environment. Russell bodies (RBs) were originally described as dilated structures of the ER cisternae containing large amounts of mutant immunoglobulin. Similar structures are observed in a wide variety of mutant proteins accumulated in the ER. We previously prepared Chinese hamster ovary (CHO) cells in which the expression of mutant antithrombin (AT) (C95R) was controlled with a Tet-On system and showed that RBs can be conditionally formed. However the precise architecture and intracellular behavior of RBs have been as yet only poorly characterized. To characterize the properties of RB, we prepared the same system using a green fluorescent protein (GFP)-fused mutant and measured the dynamics and architecture of RBs. We observed the mobile nature of the molecule in the RB lumen and RBs were separated from the rest of the ER network by narrow tubes. Furthermore, we found that the RBs were not simply expanded ER membranes. The RB lumen is filled with misfolded proteins that are surrounded by ER membranes. In addition, RBs mostly maintain their structure during cell division, possess ribosomes on their membranes and synthesize AT(C95R)-GFP. Based on the characterization of the hydrodynamic radius of AT(C95R)-GFP and the effect of DP1, an ER-shaping protein, we propose that RBs are spontaneously formed as a result of the partitioning of the misfolded AT with the shaping protein.

Ultrastructural effects of lead acetate on the spleen of rats

In this experiment, the ultrastructural effects of orally administered lead acetate on rat (Rattus rattus) spleen were studied. Rats weighing approximately 200-250 g were used in this experiment. They were divided into five groups, each one including five rats. Group I served as the normal control group while the others served as the experimental groups. The rats were exposed to oral administrations of lead acetate of 2.5 mg dissolved in 1 mL of drinking water per day. The administration lasted 96, 144, 336, and 432 h. The animals were anesthetized using chloroform inhalation and the peritoneum was stripped open and the spleen was removed and prepared for histological observation using a staining technique. Hypocellular white pulp, enlargement of venous sinusoids, clustering of heterochromatin in nucleus, vacuolation in the cytoplasm, swelling of mitochondria, and the distortion of rough endoplasmic reticulum cisterns were observed upon electron microscopic examination of the spleen tissue cells. These cytopathologic alterations indicate that lead acetate has some drastic toxicological effects on cellular structures.

Connections between microtubules and endoplasmic reticulum in mitotic spindle

Dividing endosperm cells of <i>Haemanthus katherinae</i> Bak. were treated with an 0.025 per cent aqueous solution of an oleander glycosides mixture which produces severe disturtaances in the mitotic spindle and high hypertrophy of the endoplasmic reticulum (ER) in the whole cells. There appear between the kinetochore microtubules (MTs) numerous elongated and narrow ER cisterns, particularly well visible when the number of kinetochore MTs is reduced. Both these structures (MTs and ER) are frequently connected by cross-bridges. The presumable role of these connections is discused.

Microstructure Features of Proventriculus and Ultrastructure of the Gastric Gland Cells in Chinese Taihe Black-bone Silky Fowl (Gallus gallus domesticus Brisson).

To investigate microstructure of proventriculus and ultrastructure of the gastric gland cells from Chinese Taihe black-bone silky fowl (BSF), the proventriculus of 4-week-old BSF was sampled. Conventional histological and transmission electron microscope (TEM) methods were used in this study. The wall of the Taihe BSF proventriculus was consisted of four layers, the mucous, submucosa, muscularis externa and the serosa as others birds. The muscularis externa of the birds' proventriculus contained three layers. Much of the melanin was present in loose connective tissue of lamina propria, submucosa, and muscularis externa unlike others. In addition, the ultrastructure of the gastric gland cells was observed by TEM. There was only one kind of gland cell, for example oxynticopeptic cell in proventriculus of Taihe BSF. The oxynticopeptic cells contained numerous mitochondria, cisternae of rough endoplasmic reticulum (CRER), intracellular canaliculi (IC) that secrete hydrochloric acid and small amounts of pepsinogen granules. The rough endoplasmic reticulum (RER) was irregular cisternae with ribosomes and surrounded tightly the mitochondria along their configuration. The electron-dense pepsinogen granules were round with various sizes. The neighbouring oxynticopeptic cells were closed up with tight junction and gap junction. The inter-space between the neighbouring oxynticopeptic cells was stenosis or was filled with electron-dense extracellular substance. In conclusion, the gastric gland cells of Chinese Taihe BSF proventriculus were only oxynticopeptic cells that secrete hydrochloric acid and pepsinogen, but no parietal cells and chief cells of mammal. The gastric gland cells of proventriculus were underdeveloped compared with those of mammals.

Differences in the defective alleles E and F for the locus CSN1S1 in goats affects the profile of milk caseins

The objective in the current study was to associate different genotypes for the gene that codifies the αS1-casein with the profile of milk caseins and the morphology of the mammary gland epithelial cells in goats. The genotypes HH, HF, EE and EF for the αS1-casein gene (H=any high allele) were assessed based on the differences in the size of fragments amplified using polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism (PCR-RFLP). The milk casein fractions were measured by reversed phase HPLC. Mammary gland biopsies of animals with each of these genotypes were submitted to histological and ultrastructural microscopy analysis for the evaluation of secretory epithelial cells. The amount of total casein in milk from goats with genotype HH was only higher than in milk from those animals with the genotype EF, while the αS1-casein (αS1-Cn) fraction was different among all genotypes. The largest αS1-Cn fraction was found in milk from the animals with the genotype HH, and it progressively decreased in milk from animals with the genotypes HF, EE and EF. Other milk casein fractions (β-casein, αS2-casein and κ-casein) had a characteristic composition for each genotype. The κ-casein (κ-Cn) fraction was greater whenever the F allele was found, and the β-casein fraction was greater in EE homozygous animals. The ultrastructural analysis showed that mammary gland secretory cells from goats with the genotype EE and EF have highly dilated rough endoplasmic reticulum (RER) cisternae, whereas the dilation pattern in the animals with the genotype HF was intermediate between those with the genotype HH, and EE/EF. Although the amount of αS1-casein is critical for an efficient transport of other caseins by RER, the defective F allele affects the other milk casein fractions differently from the defective E allele, probably due to the lack of phosphorylation sites on the protein encoded by the F allele, which would affect, in turn, the way caseins interact during milk micelle formation, reflecting on casein fractions in milk.

Fine structure of the uterus in tapeworm Tetrabothrius erostris (Cestoda: Tetrabothriidea).

The uterine organization in Tetrabothrius erostris (Tetrabothriidea) was investigated by the methods of transmission and scanning electron microscopy. In sexually mature proglottids, the uterine wall consists of a syncytial epithelium (1.4-2.5 μm thick, except in regions containing nuclei). The ribosomes, mitochondria and numerous cisternae of granular endoplasmic reticulum with concentric or parallel profiles with electron lucent material are observed in the epithelium. The uterine wall is characterized by the abundance of lipid droplets that are localized inside the long protrusions of the uterine epithelium (called fungiform papillae) up to 15-17μm and in the surrounding medullary parenchyma. The protrusions with lipid droplets in the proximal ends of the uterus are located closely to each other. A basal matrix (up to 0.6 μm thick) supports the uterine epithelium. The musculature consisting of 1-2 muscle layers is well developed; large myocytons are connected with the myofibrils and have a nucleus that reaches 4μm in size. In gravid proglottids, the epithelium without nuclei is reduced to 0.2-1.6 μm thick. The number of protrusions of the uterine epithelium and lipid droplets in the epithelial layer decreases. Sparse small muscle bundles underlay the uterine wall at this stage; the basal matrix is feebly marked. The matrotrophy or the support by nutrition from the parent organism to embryos is discussed for T. erostris which belongs to oligolecital cestodes and possesses numerous lipid droplets in the uterine wall during the development of embryos.

Dietary high-fat lard intake induces thyroid dysfunction and abnormal morphology in rats.

Excess dietary fat intake can induce lipotoxicity in non-adipose tissues. The aim of this study was to observe the effects of dietary high-fat lard intake on thyroid in rats. Male Sprague-Dawley rats were fed a high-fat lard diet for 24 weeks, and then the rats were fed a normal control diet (acute dietary modification) or the high-fat lard diet for another 6 weeks. The serum lipid profile, total thyroxine (TT4), free thyroxine (FT4) and thyrotropin (TSH) levels were determined at the 12, 18, 24 and 30 weeks. High-frequency ultrasound scanning of the thyroid glands was performed at the 24 or 30 weeks. After the rats were sacrificed, the thyroid glands were collected for histological and immunohistochemical analyses. The high-fat lard diet significantly increased triglyceride levels in both the serum and thyroid, and decreased serum TT4 and FT4 levels in parallel with elevated serum TSH levels. Ultrasonic imaging revealed enlarged thyroid glands with lowered echotexture and relatively heterogeneous features in the high-fat lard fed rats. The thyroid glands from the high-fat lard fed rats exhibited enlarged follicle cavities and flattened follicular epithelial cells under light microscopy, and dilated endoplasmic reticulum cisternae, twisted nuclei, fewer microvilli and secretory vesicles under transmission electron microscopy. Furthermore, the thyroid glands from the high-fat lard fed rats showed markedly low levels of thyroid hormone synthesis-related proteins TTF-1 and NIS. Acute dietary modification by withdrawal of the high-fat lard diet for 6 weeks failed to ameliorate the high-fat lard diet-induced thyroid changes. Dietary high-fat lard intake induces significant thyroid dysfunction and abnormal morphology in rats, which can not be corrected by short-term dietary modification.

Tubuloreticular inclusions in juvenile dermatomyositis: a diagnostically useful marker?

Juvenile Dermatomyositis (JDM) is a rare life threatening disease affecting children. Symptoms include severe proximal muscle weakness and characteristic skin rashes. Vascular pathology is often a key finding in JDM including typical features of capillary drop out and abnormal blood vessel endothelial cells. We have observed that another common finding in JDM biopsies is the presence of tubuloreticular inclusions (TRI) detected by electron microscopy (EM) in blood vessel endothelial cells in muscle and the overlying skin. These are tubule-like structures within cisternae of endoplasmic reticulum.

Evidence of placental endoplasmic reticulum stress in the pathophysiology of gestational diabetes mellitus

Evidence of placental endoplasmic reticulum stress in the pathophysiology of gestational diabetes mellitus

Ultrastructural characterization of in vivo-produced ovine morulae and blastocysts.

The ultrastructure of in vivo-produced ovine embryos, at the morula, early blastocyst and late blastocyst stages, was evaluated using transmission electron microscopy. Embryonic cells were characterized by the presence of intact intercellular junctions, numerous mitochondria, smooth endoplasmic reticulum cisternae and light vesicles. Polyribosomes, rough endoplasmic reticulum cisternae, secondary lysosomes, Golgi complexes and lipid droplets were also observed in the cytoplasm. The nucleus was well defined and organized, with an intact envelope rich in nuclear pore complexes, and one or more reticular nucleoli. Microvilli were present in external blastomeres of morulae and became more abundant in trophectoderm cells of early and late blastocysts. Light vesicles seemed to be associated with small cisternae of Golgi and endoplasmic reticulum origin. These cisternae fused and created light vesicles with engulfed heterogeneous cytosolic structures, small cisternae and vesicles. Their labile membrane enabled them to rapidly coalesce into medium-sized vesicles that began to engulf mitochondria and lipid droplets, forming giant vacuoles mostly filled with fat. Incomplete matured secretory vesicles were observed to exocytose into the perivitelline space of morulae, whereas fully matured secretory vesicles appeared only in trophectoderm cells, being exocytosed into the blastocoelic cavity. These observations suggested that these endoplasmic-/Golgi-derived vesicles behave as active autophagic organelles presenting probably a maturation process from compact morulae to blastocyst.

The ultrastructure of the midgut epithelium in millipedes (Myriapoda, Diplopoda)

The midgut epithelia of the millipedes Polyxenus lagurus, Archispirostreptus gigas and Julus scandinavius were analyzed under light and transmission electron microscopies. In order to detect the proliferation of regenerative cells, labeling with BrdU and antibodies against phosphohistone H3 were employed. A tube-shaped midgut of three millipedes examined spreads along the entire length of the middle region of the body. The epithelium is composed of digestive, secretory and regenerative cells. The digestive cells are responsible for the accumulation of metals and the reserve material as well as the synthesis of substances, which are then secreted into the midgut lumen. The secretions are of three types – merocrine, apocrine and microapocrine. The oval or pear-like shaped secretory cells do not come into contact with the midgut lumen and represent the closed type of secretory cells. They possess many electron-dense granules (J. scandinavius) or electron-dense granules and electron-lucent vesicles (A. gigas, P. lagurus), which are accompanied by cisterns of the rough endoplasmic reticulum. The regenerative cells are distributed individually among the basal regions of the digestive cells. The proliferation and differentiation of regenerative cells into the digestive cells occurred in J. scandinavius and A. gigas, while these processes were not observed in P. lagurus. As a result of the mitotic division of regenerative cells, one of the newly formed cells fulfills the role of a regenerative cell, while the second one differentiates into a digestive cell. We concluded that regenerative cells play the role of unipotent midgut stem cells.