Novel Identification and Microscopy of the Intestinal Bulb of Molly Fish (Poecilia sphenops) with a Focus on Its Role in Immunity.

The intestinal bulb is a simple dilatation in the anterior part of the intestine of agastric fish. This study was conducted on 18 adult specimens of molly fish (Poecilia sphenops) and demonstrated the presence of an intestinal bulb. The intestinal epithelium was composed of enterocytes covered with microvilli, many mucous goblet cells, and enteroendocrine cells. Numerous intraepithelial lymphocytes, neutrophils, plasma cells, dendritic cells, stem cells, rodlet cells, and macrophages were identified in the epithelial layer. Interestingly, this study recorded the process of autophagy and formation of autophagosomes, multivesicular bodies, and dense bodies. The intestinal epithelium extended into the intestinal gland that consisted of simple columnar epithelium, mucous cells, stem cells, enteroendocrine cells, and basal cells. These glands opened to the lumen of the bulb and were surrounded by a network of telocytes. Moreover, immunohistochemistry revealed that the intestinal epithelium expressed APG5, myostatin, TGF-ß, IL-1ß, NF-κB, Nrf2, and SOX9. Leukocytes in the lamina propria-submucosa expressed APG5. The inflammatory cells in the connective tissue showed strong immunoreactivity to myostatin and TGF-ß. The smooth muscular layer also expressed myostatin. Both IL-1ß and NF-κB showed immunoreactivity in macrophages in the lamina propria-submucosa. Stem cells expressed Sox-9 and telocytes expressed NF-κB and SOX9; while astrocytes in the tunica muscularis expressed GFAP. The high frequency of immune cells in the intestinal bulb suggested an immune role of this organ. This is the first study demonstrating the absence of the stomach and its replacement with an intestinal bulb in molly fish, and consequently, this species could be reclassified as agastric fish according to this study.

Expression of Antimicrobic Peptide Piscidin1 in Gills Mast Cells of Giant Mudskipper Periophthalmodon schlosseri (Pallas, 1770).

The amphibious teleost Giant mudskipper (Periophthalmodon schlosseri, Pallas 1770) inhabit muddy plains and Asian mangrove forests. It spends more than 90% of its life outside of the water, using its skin, gills, and buccal-pharyngeal cavity mucosa to breathe in oxygen from the surrounding air. All vertebrates have been found to have mast cells (MCs), which are part of the innate immune system. These cells are mostly found in the mucous membranes of the organs that come in contact with the outside environment. According to their morphology, MCs have distinctive cytoplasmic granules that are released during the degranulation process. Additionally, these cells have antimicrobial peptides (AMPs) that fight a variety of infections. Piscidins, hepcidins, defensins, cathelicidins, and histonic peptides are examples of fish AMPs. Confocal microscopy was used in this study to assess Piscidin1 expression in Giant Mudskipper branchial MCs. Our results demonstrated the presence of MCs in the gills is highly positive for Piscidin1. Additionally, colocalized MCs labeled with TLR2/5-HT and Piscidin1/5-HT supported our data. The expression of Piscidin1 in giant mudskipper MCs highlights the involvement of this peptide in the orchestration of teleost immunity, advancing the knowledge of the defense system of this fish.

Microanalysis of the Intestinal Bulb of Grass Carp (Ctenopharyngodon Idella): Histological, Histochemical, Immunohistochemical, and Scanning Electron Microscopical Studies.

Cyprinid fishes have one of the simplest types of gastrointestinal tract among vertebrates. Those fish species do not possess a true stomach that is replaced by a simple dilatation at the anterior part of the intestine called the intestinal bulb. Twenty adult specimens of grass carp were used in the present study to identify the cellular components as well as the immunohistochemical and surface architectural characteristics of the intestinal bulb. The mucosa of the intestinal bulb shows numerous, deep longitudinal folds arranged in zigzagging-like patterns. The epithelium is composed mainly of absorptive columnar cells covered by microvilli and mucous goblet cells. Spindle-shaped enteroendocrine cells and some migratory immune cells such as intraepithelial lymphocytes and rodlet cells could be identified between the absorptive cells. The epithelium also contains many secretory granules and large numbers of vacuoles containing digestive enzymes mostly in the basal part. The immunohistochemistry revealed that CD20-positive B-lymphocytes are immunolocalized mainly in the connective tissue core lamina propria of the mucosal folds. However, CD3-immunopositive T-lymphocytes are highly concentrated in the lamina propria. In addition, intraepithelial T-lymphocytes expressed immunopositivity to CD3. The current study presented many types of immune cells and suggests their essential immunological role for the intestinal blub.

Preemptive Stem Cells Ameliorate Neuropathic Pain in Rats: A Central Component of Preemptive Analgesia.

The present study aims to investigate the efficacy of intravenously injected mesenchymal stem cells (MSCs) in treating neuropathic pain either before or after its induction by a chronic constriction injury (CCI) model. Rats were divided into four groups: control group, neuropathic group, and treated groups (pre and postinduction) with i.v. mononuclear cells (106 cell/mL). For these rats, experimental testing for both thermal and mechanical hyperalgesia was evaluated. The cerebral cortex of the rats was dissected, and immunohistochemical analysis using anti-proliferating cell nuclear antigen (PCNA), CD117, nestin, and glial fibrillary acidic protein was performed. Our results showed that a single injection of MSCs (either preemptive/or post-CCI) produced equipotent effects on allodynia, mechanical hyperalgesia, and thermal response. Immunohistochemical analysis showed that the stem cells have reached the cerebral cortex. The injected group with MSCs before CCI showing few stem cells expressed PCNA, CD117, and nestin in the cerebral cortex. The group injected with MSCs after CCI, showing numerous recently proliferated CD117-, nestin-, PCNA-positive stem cells in the cerebral cortex. In conclusion, our findings demonstrate that the most probable effect of i.v. stem cells is the central anti-inflammatory effect, which opens concerns about how stem cells circulating in systemic administration to reach the site of injury.

Morphological characteristic and functional dependencies of dendritic cell in developing rabbit lung during fetal and neonatal life.

Recently, pulmonary DC deserved the attention of researchers and clinicians as it was implicated in many diseases afflicting human lungs. However, there are no available data about the morphological or functional features of pulmonary dendritic cells in fetal or early neonatal life. The present study aimed to demonstrate the morphological development of DCs using light-, electron-microscopy, and immunohistochemistry. DCs showed strong immunoreactivity for both CD8 and CD56. Moreover, DCs strongly expressed CD34, VEGF, NSE, and connexin-43 within the developing pulmonary tissue. By SEM, DCs were polyhedral in shape with short cell processes in fetal life. By the advancement of the age, DCs became more numerous and exhibited rounded to oval cell bodies with many fine dendrites. TEM revealed that at early fetal life, DCs were characterized by their heterochromatic indented nuclei, few cell processes and few organelles. With the advancement of age, DCs showed dendrite-like processes and displayed signs of high endocytic activities with releasing of secretory materials. At late fetal life, DCs showed an obvious increase in the nuclear/cytoplasmic ratio and they exhibited a unique connection with type II pneumocytes and pulmonary endothelium by gap junction. In the early neonate, the DCs cells were seen in association with T-lymphocytes, neutrophils, telocytes (TCs), and air-blood barrier. They possessed many fine dendrites, the characteristic Birbeck granules and many vesicles. DCs may contribute to apoptosis, endocytosis, and angiogenesis. The difference in the maturation status may reflect different roles for DCs in the lung. The immature DCs may have an antigen-uptake role through endocytosis, while mature DCs may involve in antigen presentation to T-cells.

WITHDRAWN: Structural, ultrastructural, and immunohistochemical characteristics of the cell composition of the head kidney of grass carp (Ctenopharyngodon idella).

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Histological and Ultrastructural Studies of the Unique Hemopoietic-Endocrine Organ of the Grass Carp, Ctenopharyngodon idella (Valenciennes, 1844).

Specific features of the immunohistochemical and ultrastructural organization of the hemopoietic head-kidney (HK) in adult Ctenopharyngodon idella (Valenciennes, 1844) were investigated using light and transmission electron microscopy. The HK of grass carp possessed all developmental stages of leucocytes and erythrocytes, as well as dendritic cells and epithelial reticular cells. The rodlet cells were expressed α-smooth muscle actin (SMA). In addition, macrophages were the most numerous cells in the HK, which aggregated into structures called melanomacrophage centers (MMCs). On contrary, the chromaffin and interrenal cells (ICs) were mixed and organized into large anastomosing cords, which lined the posterior cardinal veins of the HK, and associated with many blood capillaries. The ICs displayed the characteristic features of steroid-producing cells. Three types of chromaffin cells: adrenaline, noradrenaline, and small granule-containing cells were observed in the HK. Glial fibrillary acidic protein (GFAP)-positive sustentacular cells were marked among the chromaffin cells. Hemopoietic cells, immune cells, MMCs, rodlet cells, in addition to three types of chromaffin cells and one type of interrenal cells in the HK were correlated with the functional significance of the fish concerned.

Patterns of Organization of Cerebellum and Spinal Cord of the Red-Tail Shark (Epalzeorhynchos bicolor): Histological, Morphometrical, and Immunohistochemical Studies.

Teleosts exhibit enormous heterogeneity in brain morphology, especially in the patterns of the organization of cerebellum. The cerebellum of a red-tail shark that we analyzed was well-developed and included three main divisions: the valvula cerebelli, the corpus cerebelli, and the vestibulolateral lobe. Characteristically, the cerebellar cortex contained three well-distinct layers: an outer molecular, intermediate ganglionic, and inner granular layer. The ganglionic layer possessed irregularly arranged Purkinje cells and eurydendroid cells that extended their processes into the molecular layer. Both Purkinje cells and eurydendroid cells showed immunoreactivity for iNOS2. Moreover, astrocytes in the cerebellum showed the expression of glial fibrillary acidic protein. The most striking observation in the cerebellum of shark was the lack of deep cerebellar nuclei and a well-identified white matter. On the other hand, the gray substance in the spinal cord displays a characteristic pattern in its organization, in which the dorsal horns lie quite close together, giving the gray substance the shape of an inverted Y and possessing large neurons. Notably, the white matter possessed myelinated nerve fibers. The current study provides the first report on the organization of layers and neurons in the cerebellum and spinal cord of red-tail shark. This research will contribute to the neuroanatomy and evolutionary studies of the brain of Cyprinidae.

Microanalysis of Fish Ovarian Follicular Atresia: A Possible Synergic Action of Somatic and Immune Cells.

The present study describes in detail the morphological characteristics of the process of ovarian follicular atresia in Redbelly tilapia (Coptodon zillii) during the nonbreeding season using light and electron microscopy and immunohistochemistry. The follicular regression process was initiated with shrinkage and disintegration of the nuclear membrane of oocytes resulting in dispersing of chromatin within the ooplasm, followed by marked hyperplasia and hypertrophy of follicular and granulosa cells, which exhibited a strong phagocytic activity to engulf the liquefied yolk particles. Rodlet cells and granulocytes were recorded on the follicular wall and invaded the regressed follicles. Rodlet cells expressed a strong immunoreactivity to matrix metalloperoxidase (MMP-9) and α-smooth muscle actin, while neutrophils expressed a strong reactivity to Myeloperoxidase-3 (MPO). In the advanced stage of follicular atresia, the yolk was almost phagocytized and resorbed and the regressed follicle lost its integrity and appeared to be formed of a cellular mass of phagocytic cells. Transmission electron microscopy revealed the presence of neutrophils, eosinophils, and dendritic cells within the atretic follicle in between these phagocytic cells. Moreover, numerous lysosomes, granules, and phagosomes were observed within the cytoplasm of both phagocytic cells and granulocytes. Telocytes were also demonstrated within the highly thickened richly vascularized theca layer during the late stages of follicular atresia. Immunohistochemical staining for caspase-3 established the participation of apoptosis in the advanced stages of follicular regression. Immune cells, rodlet cells, and telocytes in combination with follicular cells play an essential role in follicular atresia. In conclusion, the present study provides a new evidence on the role of both somatic and immune cells in the phenomenon of ovarian follicular atresia in Redbelly tilapia (Coptodon zillii) during the nonbreeding season.

The morphological development of the proventriculus of Dandarawi chick: Light and electron microscopical studies.

This study was carried out on 40 chick embryos collected from incubated eggs of Dandarawi chicken (Gallus gallus domesticus) on the 5th to 19th incubation day (27 to 45 Hamburger and Hamilton, H&H stages). In addition, 15 chicks were collected on the day of hatching (stage 46 H&H), one week and two weeks post-hatching to demonstrate the histological, histochemical, and electron microscopic developmental changes of the proventriculus (of the digestive tract). Histologically, the proventriculus was observed as a narrow tube at 27 H&H stage. It was lined by pseudostratified columnar epithelium through 27-39 H&H stages and from the stage 43 till post-hatching, it was lined by simple columnar epithelium. The Lamina muscularis mucosa could be identified at stage 43. The proventricular glands were detected firstly at stage 31 and branching at stage 35. Histochemically, the surface epithelium and proventricular glands reacted positively to PAS, alcian blue and bromophenol blue from stage 31 till maturity. The glands displayed an apocrine mode of secretion at stage 39 and their cytoplasm contained abundant mitochondria, RER, secretory granules, and lipid droplets. Enteroendocrine cells could be observed among the glandular and surface epithelium at stage 45 H&H. The interstitial tissue contained fibroblasts and telocytes. The telocytes were firstly detected at stage 35 H&H and composed of a cell body and two long cell processes called telopodes. The tunica muscularis differentiated into three layers of smooth muscle fibers at stage 37 H&H. The cellular and stromal organizations of the proventriculus and their relations to the development and function were discussed.

The roles of telocytes in lung development and angiogenesis: An immunohistochemical, ultrastructural, scanning electron microscopy and morphometrical study.

Many studies have been carried out to investigate the occurrence and distribution of telocytes (TCs) in many organs. However, their morphological development is still unclear. This study was performed to demonstrate the morphological development of TCs in rabbits' lung from fetal to postnatal life using light-, electron- microscopy, immunohistochemistry, morphometrical and statistical analysis. During the fetal life, these cells formed an extensive network of telopodes (Tps) which were in close contact with developing alveoli, bronchioles, stem cells and many other interstitial components. In addition, the TCs' number was significantly increased around the neocapillaries in fetal lung. In the fetal life, TCs were stellate in shape and characterized by large cell bodies and many short Tps that contained abundant rER, mitochondria, and ribosomes. By gradual increasing of ages, TCs were spindle in shape with two Tps contained a massive amount of secretory structures (exosomes, ectosomes, and multivesicular bodies). Moreover, TCs in postnatal lung showed a significant decrease in number and diameter of their cell bodies and a significant increase in the length of Tps compared with those in fetal life. The TCs contributed with pneumocytes and endothelium in the formation of air-blood barrier. The TCs' immunohistochemical profiles for CD34, vimentin, c-kit, connexin 43, vascular endothelial growth factor (VEGF), and neuron- specific enolase (NSE) differed between ages during the lung development. This study provided an evidence that TCs contributed to angiogenesis, the formation of the air-blood barrier, lung organization, and development.

Retinoid-related orphan nuclear receptor alpha (RORα)-deficient mice display morphological testicular defects.

The role of retinoid-related orphan receptor, one of the transcription factors reported in testis, in testicular function is unclear, so this study was performed to evaluate the qualitative and quantitative changes in the testicular structure of RORα-deficient mice using light-, electron-microscopy, and immunohistochemistry. Among the most striking alterations observed in the testis of the mutant mice were hypospermatogenesis, marked reduction in volume proportions of interstitial tissues and number of Leydig cells, significant decrease in the diameter of seminiferous tubules and height of their epithelium, vacuolation in the epithelium of the seminiferous tubules with occurrence of mast cells, appearance of delay spermiation signs, and changes in sperm morphology. Moreover, the testis of mutant mice showed symplasts, in addition to appearance of multinucleated giant bromophenol-positive cells. ATPase activity was limited to spermatogonia and some primary spermatocytes, with higher alkaline phosphatase expression. Stronger vimentin reaction was immunolocalized to spermatogonia, spermatids, Leydig cells, and Sertoli cells. The expression of CD117 (C-kit, stem cell growth factor receptor) was limited to spermatogonia, primary spermatocytes, and Leydig cells. Seminiferous tubules showed overexpression of vascular endothelial growth factor (VEGF). Transmission electron microscopy examination of the mutant mice revealed abnormal Sertoli cells, hypertrophied spermatogonia, spermatocytes with degenerated mitochondria, and incompletely developed sperms. In conclusion, RORα is one of the essential proteins that regulate testicular structure.

Characterization of the fish ovarian stroma during the spawning season: Cytochemical, immunohistochemical and ultrastructural studies.

The changes in the ovarian stroma of the fish during their spawning season become it an excellent biological model for studies on cellular and vascular elements due to the intense tissue remodeling in fish occur naturally throughout this critical period. The present study aims to investigate the cellular and vascular components of the ovarian stroma of Redbelly tilapia during the spawning season by conventional, immunohistochemical stains as well as to detect the ultrastructural characteristics for each stromal component. The histological examinations revealed a series of blood vessels with special structures, include throttle artery, glomus, spirally oriented arterioles, modified arteries, and veins as well as arteriovenous anastomosis. Various types of cells were detected in the stroma include; telocytes, rodlet cells, mast cells, eosinophils, neutrophils, lymphocytes, fibroblasts, macrophages, melanocytes, adipocytes, dendritic cells, and endocrine (steroidogenic, interstitial) cells. Moreover, these stromal cells showed a broad range of staining affinity against c-kit, desmin, and s100-protein. Bundles of nerve fibers were detected between the follicles. This study exposed various cellular and vascular components with distinct functions in the ovary of Redbelly tilapia during the spawning season.

New Insight into the Development of the Respiratory Acini in Rabbits: Morphological, Electron Microscopic Studies, and TUNEL Assay.

This study investigated the histomorphological features of developing rabbit respiratory acini during the postnatal period. On the 1st day of postnatal life, the epithelium of terminal bronchiole consisted of clear cells which intercalated between few ciliated and abundant non-ciliated (Clara) cells. At this age, the rabbit lung was in the alveolar stage. The terminal bronchioles branched into several alveolar ducts, which opened into atria that communicated to alveolar sacs. All primary and secondary inter-alveolar septa were thick and showed a double-capillary network (immature septa). The primitive alveoli were lined largely by type-I pneumocytes and mature type-II pneumocytes. The type-I pneumocytes displayed an intimate contact with the endothelial cells of the blood capillaries forming the blood-air barrier (0.90 ± 0.03 µm in thickness). On the 3rd day, we observed intense septation and massive formation of new secondary septa giving the alveolar sac a crenate appearance. The mean thickness of the air-blood barrier decreased to reach 0.78 ± 0.14 µm. On the 7th day, the terminal bronchiole epithelium consisted of ciliated and non-ciliated cells. The non-ciliated cells could be identified as Clara cells and serous cells. New secondary septa were formed, meanwhile the inter-alveolar septa become much thinner and the air-blood barrier thickness was 0.66 ± 0.03 µm. On the 14th day, the terminal bronchiole expanded markedly and the pulmonary alveoli were thin-walled. Inter-alveolar septa become much thinner and single capillary layers were observed. In the 1st month, the secondary septa increased in length forming mature cup-shaped alveoli. In the 2nd month, the lung tissue grew massively to involve the terminal respiratory unit. In the 3rd month, the pulmonary parenchyma appeared morphologically mature. All inter-alveolar septa showed a single-capillary layer, and primordia of new septa were also observed. The thickness of the air-blood barrier was much thinner; 0.56 ± 0.16 µm. TUNEL assay after birth revealed that the apoptotic cells were abundant and distributed in the epithelium lining of the pulmonary alveoli and the interstitium of the thick interalveolar septa. On the 7th day, and onward, the incidence of apoptotic cells decreased markedly. This study concluded that the lung development included two phases: the first phase (from birth to the 14th days) corresponds to the period of bulk alveolarization and microvascular maturation. The second phase (from the 14th days to the full maturity) corresponds to the lung growth and late alveolarization.

Morphological Characteristics of the Developing Cecum of Japanese Quail (Coturnix coturnix japonica).

The current investigation was carried out to record the final stages of the development of both middle and distal parts of quail ceca, Coturnix coturnix japonica to understand the role of ceca in digestion, immune system, and absorption. The cellular and subcellular structures, including epithelial cell height, microvillus surface area, the proportion of goblet cells, the thickness of muscle layer, and cecum diameter showed great variations during the development. An undeveloped smooth muscularis mucosa was observed for the first time on the ED5. Primordia of glands were observed on the ED7. On the ED15, the middle part exhibited two shapes of mucosal villi: tongue-shaped villi and U-shaped. The plicae and crypts of Lieberkühn were demonstrated on the hatching day. The lymphatic tissues appeared in the wall of both parts of the ceca at the 4 weeks of age. Scanning electron microscopy revealed a great difference in the mucosal surface between different regions. Telocytes were observed in-between the muscle fibers and formed a network during the post-hatching period. Because of fermentation and other bacterial or chemical processes that have been shown to occur in the ceca, this study supports two hypotheses: the cecal development is related to diet and the cecal epithelium act as a site for primary absorption of nutrients or for re-absorption of electrolytes or amino acids derived from the urine.

Effect of Melatonin on Telocytes in the Seminal Vesicle of the Soay Ram: An Immunohistochemical, Ultrastructural and Morphometrical Study.

Telocytes (TCs) are a special type of interstitial cell with characteristic cellular processes that are described in many organs. The current study aimed to investigate TCs in seminal vesicles of the Soay ram responding to melatonin treatment during the nonbreeding season by conventional immunohistochemical stains, and to detect the ultrastructural and morphometrical changes of TCs. TCs in the control group showed a broad range of staining affinity and also reacted positively to CD117/c-kit, CD34, desmin, S-100 protein, and progesterone and estrogen receptors alpha, while after melatonin treatment a strong reaction against these 6 antibodies was recorded. Electron microscopically, TCs in the control group were characterized by a small cell body with distinct long cytoplasmic extensions called telopodes (Tps). Tps had alternation of the thin segment (podomers) and dilated segments (podoms), in which the latter accommodate mitochondria, rough endoplasmic reticulum and caveolae. TCs and their Tps were interconnected by homo- and heterocellular junctions and form a wide network to communicate between different cell types. Tps showed close contact with immune cells, progenitor stem cells, smooth muscle cells and other interstitial cells. Melatonin caused a significant increase in the number of TCs, length of Tps, and number and diameter of secretory vesicles. Also, the melatonin-treated group showed exaggerated secretory activity in the form of a massive release of secretory vesicles from Tps. Moreover, Tps showed an increase in their contact with blood and lymphatic capillaries, nerve endings and Schwann cells. In addition, the shedding of secretory structures (exosomes, ectosomes, and multivesicular bodies) was greater from Tps, which were involved in paracrine signaling in the melatonin-treated group. The length and ramifications of Tps together with the intercellular junctions and the releasing of shed vesicles or exosomes assumed an essential role of TCs in intercellular signaling and coordination. On the basis of their distribution and morphology, we investigated whether the different locations of TCs could be associated with different roles.

Melatonin Elicits Stimulatory Action on the Adrenal Gland of Soay Ram: Morphometrical, Immunohistochemical, and Ultrastructural Study.

Endogenous melatonin is a hormone secreted by pineal gland; it has several roles in metabolism, reproduction, and remarkable antioxidant properties. Studies on the melatonin effect on the adrenal glands which are important endocrine organs, controlling essential physiological functions, are still deficient. In this study, we attempted to investigate the effect of exogenous melatonin treatment on the adrenal cortex and medulla using several approaches. Adrenal glands of 15 Soay ram were examined to detect the effect of melatonin treatment. Our results revealed that the cells of adrenal cortex of the treated animals were separated by wide and numerous blood sinusoids and showed signs of increase steroidogenic activity, which are evidenced by functional hypertrophy with increase profiles of mitochondria, smooth endoplasmic reticulum, and lipid droplets. The most striking ultrastructural features in the medulla of the treated group were the engorgement of chromaffin cells with enlarged secretory granules enclosed within a significantly increased diameter of these cells. The cytoplasm of these cells showed numerous mitochondria, rough endoplasmic reticulum (rER), Golgi apparatus, lysosomes, and glycogen granules. Exocytosis of secretory granules to the lumen of blood vessels was evident in the treated group. Piecemeal degranulation mode of secretion was recorded after melatonin treatment. Chromaffin cells in the control group expressed moderate immunoreactivity to Synaptophysin and tyrosine hydroxylase, compared with intensified expression after melatonin treatment. The ganglion cells of the melatonin-treated group showed a significant increase in diameter with numerous rER. The most interesting feature in this study is the presence of small granule chromaffin cells (SGC) and telocytes (TCs) for the first time in the adrenal glands of sheep. Moreover, these SGC cells, Schwann cells, fibroblasts, and progenitor stem cells showed a stimulatory response. The TCs were small branched cells scattered in the adrenal glands around cortical cells, chromaffin cells, nerve fibers, and blood vessels. These cells increased significantly in number, length of their telopodes, and secretory activity after melatonin treatment. In addition, multiple profiles of unmyelinated nerve fibers were demonstrated in all treated specimens. These results indicated that melatonin treatment caused a stimulatory action on all cellular and neuronal elements of the adrenal gland. This study may act as a new direction for treatment of adrenal insufficiency.

Retinal Structure of Poecilia sphenops: Photoreceptor Mosaics, Synaptic Ribbon Patterns, and Glial Cell Expressions.

The specific arrangement and distribution of photoreceptors in the retina can vary among different fish species, with each species exhibiting adaptations related to its habitat, behavior, and visual requirements. Poecilia sphenops, a diurnal fish, was the focus of this study. The retinas of a total of eighteen Molly fish were investigated utilizing light and electron microscopy. The retina exhibited a square mosaic pattern of the inner segments of cones. This pattern comprised double cones positioned along the sides of a square, with two types of single cones situated at the center and corners of the square arrangement across the entire retina. The corner cones were slightly shorter than the central ones. Additionally, the outer plexiform layer contained both cone pedicles and rod spherules. The rod spherule consisted of a single synaptic ribbon arranged in a triad or quadrat junctional arrangement within the invaginating free ends of the horizontal and bipolar cell processes. On the other hand, cone pedicles have more than one synaptic ribbon in their junctional complex. The inner nuclear layer consisted of the amacrine, bipolar, Müller, and horizontal cell bodies. Müller cell processes, expressing GFAP, extended across all retinal layers, segmenting the deeper retina into alternating fascicles of optic axons and ganglion cells. The outer and inner plexiform layers showed many astrocyte cell processes expressing GFAP. In conclusion, the current study is the first record of the retinal structures of Molly fish. This study illustrated the mosaic arrangement of photoreceptors and GFAP expression patterns of astrocytes and Müller cells. The presence of three cone types, coupled with a sufficient number of rods, likely facilitates motion awareness for tasks like finding food and performing elaborate mating ceremonies.

Light and electron microscopic observations on retinal neurons of red-tail shark (Epalzeorhynchos bicolor H. M. Smith, 1931).

The structure of photoreceptors (PR) and the arrangement of neurons in the retina of red-tail shark were investigated using light and electron microscopy. The PR showed a mosaic arrangement and included double cones, single cones (SC), and single rods. Most cones occur as SC. The ratio between the number of cones and rods was 3:1.39 (±0.29). The rods were tall that reached the pigmented epithelium. The outer plexiform layer (OPL) showed a complex synaptic connection between the horizontal and photoreceptor terminals that were surrounded by Müller cell processes. Electron microscopy showed that the OPL possessed both cone pedicles and rod spherules. Each rod spherule consisted of a single synaptic ribbon within the invaginating terminal endings of the horizontal cell (hc) processes. In contrast, the cone pedicles possessed many synaptic ribbons within their junctional complexes. The inner nuclear layer consisted of bipolar, amacrine, Müller cells, and hc. Müller cells possessed intermediate filaments and cell processes that can reach the outer limiting membrane and form connections with each other by desmosomes. The ganglion cells were large multipolar cells with a spherical nucleus and Nissl' bodies in their cytoplasm. The presence of different types of cones arranged in a mosaic pattern in the retina of this species favors the spatial resolution of visual objects. RESEARCH HIGHLIGHTS: This is the first study demonstrating the structure and arrangement of retinal neurons of red-tail shark using light and electron microscopy. The current study showed the presence of different types of cones arranged in a mosaic pattern that may favor the spatial resolution of visual objects in this species. The bipolar, amacrine, Müller, and horizontal cells could be demonstrated.

Neuron mapping in the Molly fish optic tectum: An emphasis on the adult neurogenesis process.

Teleost fish exhibit the most pronounced and widespread adult neurogenesis. Recently, functional development and the fate of newborn neurons have been reported in the optic tectum (OT) of fish. To determine the role of neurogenesis in the OT, this study used histological, immunohistochemical, and electron microscopic investigations on 18 adult Molly fish specimens (Poecilia sphenops). The OT of the Molly fish was a bilateral lobed structure located in the dorsal part of the mesencephalon. It exhibited a laminated structure made up of alternating fiber and cellular layers, which were organized into six main layers. The stratum opticum (SO) was supplied by optic nerve fibers, in which the neuropil was the main component. Radial bipolar neurons that possessed bundles of microtubules were observed in the stratum fibrosum et griseum superficiale (SFGS). Furthermore, oligodendrocytes with their processes wrapped around the nerve fibers could be observed. The stratum album centrale (SAC) consisted mainly of the axons of the stratum griseum centrale (SGC) and the large tectal, pyriform, and horizontal neurons. The neuronal cells of the SO and large tectal cells of the SAC expressed autophagy-related protein-5 (APG5). Interleukin-1ß (IL-1ß) was expressed in both neurons and glia cells of SGC. Additionally, inducible nitric oxide synthase (iNOS) was expressed in the neuropil of the SAC synaptic layer and granule cells of the stratum periventriculare (SPV). Also, transforming growth factor beta (TGF-ß), SRY-box transcription factor 9 (SOX9), and myostatin were clearly expressed in the proliferative neurons. In all strata, S100 protein and Oligodendrocyte Lineage Transcription Factor 2 (Olig2) were expressed by microglia, oligodendrocytes, and astrocytes. In conclusion, it was possible to identify different varieties of neurons in the optic tectum, each with a distinct role. The existence of astrocytes, proliferative neurons, and stem cells highlights the regenerative capacity of OT. RESEARCH HIGHLIGHTS: The OT of the Molly fish exhibited a laminated structure made up of alternating fiber and cellular layers, which were organized into six main layers. Radial bipolar neurons that possessed bundles of microtubules were observed in the stratum fibrosum et griseum superficiale (SFGS). The stratum album central (SAC) consisted mainly of the axons of the stratum griseum centrale (SGC) and the large tectal, pyriform, and horizontal neurons. Inducible nitric oxide synthase (iNOS) was expressed in the neuropil of the SAC synaptic layer and granule cells of the stratum periventricular (SPV). Also, transforming growth factor beta (TGF-ß), SRY-box transcription factor 9 (SOX9), and myostatin were clearly expressed in the proliferative neurons. The existence of astrocytes, proliferative neurons, and stem cells highlights the regenerative capacity of OT.