Fluazuron-induced morphophysiological changes in the cuticle formation and midgut of Rhipicephalus sanguineus Latreille, 1806 (Acari: Ixodidae) nymphs

The present study demonstrated the effects of the arthropod growth regulator, fluazuron (Acatak®), in the formation of the integument and digestive processes of Rhipicephalus sanguineus nymphs fed on rabbits treated with different doses of this chemical acaricide. For this, three different doses of fluazuron (20, 40, or 80 mg/kg) were applied “pour on” to the hosts (groups II, III, and IV), as well as distilled water to the control group. On the first day after treatment (24 h), the hosts were artificially infested with R. sanguineus nymphs. After full engorgement (7 days), the nymphs were removed, placed on labeled Petri dishes, and kept in biochemical oxygen demand incubator for 7 days. The engorged nymphs were then taken for morphological, histochemical, and histological analyses. The results showed the occurrence of cytological, morphohistological, and histochemical alterations in the integument and midgut of nymphs from all the different treated groups. These alterations occurred at cuticular level in the subdivisions of the cuticle, related to the size of the digestive cells, amount of accumulated blood elements, and digestive residues, as well as the presence of vacuoles in the cytoplasm of the digestive cells. Thus, this study demonstrated that fluazuron acts on the integument and midgut cells of R. sanguineus nymphs fed on treated rabbits and pointed out the possibility of the use of this chemical—which is more specific, less toxic, and less harmful to the environment and nontarget organisms—in the control of R. sanguineus, at least in the nymphal stage of its biological cycle.     

缢蛏泄肠吸虫病病理学和组织化学研究

食蛏泄肠吸虫幼虫期对缢蛏的病理危害,与缢蛏受感染后的时间长短有关,因此表现在与缢蛏不同发育期有一定的相关性。对1年蛏生长期危害较轻,对1年蛏成熟期危害加重,对2年蛏生长期危害最重。同时发现,食蛏泄肠吸虫幼虫期对缢蛏的危害程度与不同的组织器官也有关,对缢蛏生殖腺、消化腺危害最重。可靠成生殖腺萎缩、破损,甚至造成整个生殖腺消失;对缢蛏消化腺造成消化腺盲囊变形、萎缩、破损。此外幼虫期还可对缢蛏的鳃组织、唇瓣、外套膜、肌肉、心室和晶杆囊等许多组织器官造成不同程度的危害。组织化学分析表明,食蛏泄肠吸虫幼虫期可造成缢蛏体内多种组化成分的损失,其中,糖原类物质和蛋白质的损失最严重     

Characterization of heavy metal secretory granules in the islet tissue of adult white rats by means of the light and electron microscopy, including the high voltage electron miscroscopy and the electron microanalysis (author's transl)]

The metal secretory granules of Langerhans' islets of white rats were examined after histochemical detection by sulfide silver staining method as well as by conventional electron microscopy and high voltage electron microscopy. Zinc and calcium were determined with electron probe x-ray-microanalysis. The metals are located at the inside of cytoplasmatic vacuoles, a result, we discuss in connection with the release of pancreatic hormones.     

The expression and distribution of a leptin receptor in the central nervous system,digestive organs,and gonads of the giant freshwater prawn, Macrobrachium rosenbergii

In the present study, the presence and distribution of leptin receptor (LEP-R) in central nervous system, digestive organs, gonads of giant freshwater prawn, Macrobrachium rosenbergii, were investigated with Western blot and immunohistochemistry. By Western blot a LEP-R with a molecular weight (MW) of 100?kDa was detected in the brain, thoracic ganglia, abdominal ganglia, hepatopancreas, all parts of the gastrointestinal tract, ovaries, and testes. In hepatopancreas and foregut, another intense positive band was detected at molecular weight of 30?kDa, which could be an isotype of LEP-R. By immunohistochemistry, LEP-R-ir was detected in the neurons, and neuropils in the brain, thoracic ganglia, and abdominal ganglia. In the gastrointestinal tract, there was intense LEP-R-ir in the apical part of the epithelial cells of the foregut, midgut, and hindgut. In addition, LEP-R-ir was found in the Restzellen(R)cells and Fibrillenzellen(F) cells in the hepatopancreas. In the ovary, LEP-R-ir was detected in early stage of oocytes and mature oocytes. Intense LEP-R-ir was observed in spermatogonia and spermatocytes of the small and orange claw male prawns. In addition, LEP-R was seen in the high epithelium of spermatic ducts from all male morphotypes. In summary, the detection of the LEP-R-ir suggests the existence of a LEP-R in several organs of M. rosenbergii. Through binding with leptin peptide, LEP-R may be an important signaling molecule that has critical functions in modulating and controlling food intake, energy expenditure, and reproduction in this prawn.     

Calcium-containing,smooth-surfaced endoplasmic reticulum and vacuoles in cells of the blastopore-forming region during gastrulation of the newt,Cynops pyrrhogaster

Ultrastructural changes in cells of the blastopore-forming region (BFR) were examined during gastrulation of the newt, Cynops pyrrhogaster. Smooth-surfaced endoplasmic reticulum (sER), tubular in shape and with two types of vacuole, empty vacuoles and multilamellar vacuoles, appeared in cells of the BFR at the beginning of formation of the blastopore. The extent of the tubular sER increased during formation of the blastopore. With the deepening of the blastoporal groove, the tubular sER and multilamellar vacuoles disappeared in cells of the BFR. The empty vacuoles increased in number and appeared throughout the cytoplasm of the cells in the BFR and the marginal zone as formation of the archenteron progressed. Many large empty vacuoles were closely associated with deformed lipid droplets. Cytochemistry and X-ray microanalysis revealed the accumulation of calcium in the tubular sER and in some of the empty vacuoles. These results suggest important roles for the calcium-containing tubular sER in the regulation of the intracellular concentration of calcium during formation of the blastopore, as well as a role for empty vacuoles in the dissolution and consumption of lipid droplets during early gastrulation.     

Defect of In Vitro Digestive Ability of Polymorphonuclear Leukocytes in Paracoccidioidomycosis

Selected functions of polymorphonuclear leukocytes were studied in patients with paracoccidioidomycosis (South American blastomycosis), in healthy control individuals, and in patients with diseases unrelated to paracoccidioidomycosis. Patients with paracoccidioidomycosis were also evaluated by standard immunological techniques. Phagocytosis and digestion of Paracoccidioides brasiliensis yeastlike cells in vitro was estimated by an original method. It was based on the appearance of phagocytosed P. brasiliensis in preparations stained by a modification of the Papanicolaou method and examined with phase-contrast optics. Interpretation of such findings was confirmed by electron microscopy. Two strains of P. brasiliensis were used. Strain 8506 was freshly isolated from a patient. Strain Pb9 was known to be nonpathogenic and to have a peculiar cell wall composition. Yeastlike cells of the Pb9 strain were digested significantly better than those of strain 8506. A higher number of leukocytes per fungus cells led to a higher proportion of digested P. brasiliensis. Leukocytes from patients with paracoccidioidomycosis phagocytosed the fungus in a normal way, but had a significant lower ability to digest it in vitro. When individual cases were analyzed, there was an excellent correlation between clinical evolution and digestive ability of polymorphonuclear leukocytes. There was good correlation between both of these and immunological parameters. Leukocytes from all groups behaved comparably in tests of general leukocyte function and in their abilities to kill and digest Candida albicans. Our results indicate that, as a group, polymorphonuclear leukocytes from patients with paracoccidioidomycosis had a significant, rather specific, defect in their in vitro digestive capacity against phagocytosed P. brasiliensis. There was also an inverse correlation between strain pathogenicity and its susceptibility to in vitro digestion by polymorphonuclear leukocytes. Our findings are concordant with and relevant to clinical reality.     

Study on the Effect of Polysaccharides from Solanum Nigrum Linne on Cellular Immune Function in Tumour-Bearing Mice

We investigated the anti-tumour effect of polysaccharides from Solanum nigrum Linne, and its relationship with the immune function of tumour-bearing organisms. MTT assay was used to observe the effect of different doses of polysaccharides from Solanum nigrum Linne on proliferation of lymphocytes in tumour-bearing mice. ELISA assay was also used to detect the levels of IL-2 in mice, and a laser scanning confocal microscope was used to detect the effect of polysaccharides from Solanum nigrum Linne on intralymphocytic free calcium ion concentration in tumour-bearing mice. Different doses of polysaccharides from Solanum nigrum Linne significantly inhibited the growth of mouse H22 solid tumours, improved the survival time of tumour-bearing mice, increased the proliferation of lymphocytes, elevated the levels of IL-2, and increased the concentration of calcium ions in the lymphocytes. Polysaccharides from Solanum nigrum Linne have certain anti-tumour effect, which is related with the cellular immune function that regulates the body.     

IL-4Rα-responsive smooth muscle cells contribute to initiation of TH2 immunity and pulmonary pathology in Nippostrongylus brasiliensis infections

Nippostrongylus brasiliensis infections generate pulmonary pathologies that can be associated with strong T_H2 polarization of the host’s immune response. We present data demonstrating N. brasiliensis-driven airway mucus production to be dependent on smooth muscle cell interleukin 4 receptor-α (IL-4Rα) responsiveness. At days 7 and 10 post infection (PI), significant airway mucus production was found in IL-4Rα^−/lox control mice, whereas global knockout (IL-4Rα^−/−) and smooth muscle-specific IL-4Rα-deficient mice (SM-MHC^Cre IL-4Rα^−/lox) showed reduced airway mucus responses. Furthermore, interleukin (IL)-13 and IL-5 cytokine production in SM-MHC^Cre IL-4Rα^−/lox mice was impaired along with a transient reduction in T-cell numbers in the lung. In vitro treatment of smooth muscle cells with secreted N. brasiliensis excretory–secretory antigen (NES) induced IL-6 production. Decreased protein kinase C (PKC)-dependent smooth muscle cell proliferation associated with cell cycle arrest was found in cells stimulated with NES. Together, these data demonstrate that both IL-4Rα and NES-driven responses by smooth muscle cells make important contributions in initiating T_H2 responses against N. brasiliensis infections.     

Morphology of the midgut of Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae) adult ticks in different feeding stages

The intestinal epithelial cells of ticks are fundamental for their full feeding and reproductive success, besides being considered important sites for the development of pathogens. Rhipicephalus sanguineus ticks are known for their great medical and veterinary importance, and for this reason, the knowledge of their intestinal morphology may provide relevant subsidies for the control of these animals, either by direct acaricidal action over these cells or by the production of vaccines. Therefore, this study aimed to describe the midgut morphology of male and female R. sanguineus ticks in different feeding stages, by means of histological analysis. Significant differences were observed between the genders, and such alterations may refer mainly to the distinct demands for nutrients, much higher in females, which need to develop and carry out the egg-laying process. In general, the midgut is coated by a thin muscle layer and presents a pseudostratified epithelium, in which two basic types of cells can be observed, connected to a basal membrane—generative or stem and digestive cells. The latter was classified as follows: residual, deriving from the phase anterior to ecdysis; pinocytic, with vesicles containing liquid or pre-digested components of blood; phagocytic, with entire cells or remnants of nuclear material inside cytoplasmic vesicles; and mature, free in the lumen. Digestion is presumably intracellular and asynchronous and corresponds to a process which starts with the differentiation of generative cells into pinocytic digestive cells, which subsequently start to phagocytize intact blood cells and finally detach from the epithelium, being eliminated with feces.     

Paracoccidioides brasiliensis infection increases regulatory T cell counts in female C57BL/6 mice infected via two distinct routes

Studies that show an overview of the peripheral immune response in a model of Paracoccidioides brasiliensis (Pb) infection in females are scarce in the literature. We sought to characterize the innate and adaptive immune responses in female C57BL/6 mice infected with Pb through two distinct routes of administration, intranasal and intravenous. In addition to the lung, P. brasiliensis yeast cells were observed in liver and brain tissues of females infected intravenously. To our knowledge, our study is the first to prove the presence of this pathogenic fungus in the cerebral cortex of female mice. During the initial stages of infection, augmented expression of both MHCII and CD86 was observed on the surface of CD11c⁺ pulmonary antigen-presenting cells (APCs) in intranasally and intravenously infected females. However, CD40 expression was downregulated in these cells. Concomitantly with increasing serum IL-10 levels, we noted that splenic dendritic cells (DCs) from both intravenously- and intranasally-infected female mice had acquired an immature phenotype. Further, increased T regulatory cell counts were observed in female mice infected via both routes, along with an increase in the infiltration of IL-10-producing CD8⁺ T cells into the lungs. Moreover, we noted that P. brasiliensis infection resulted in enhanced IL-10 production – by CD11c⁺ APCs in the lung tissue – and induction of Th17 polarization. Taken together, our results suggest that P. brasiliensis could modulates the immune response in female mice by influencing the balance between regulatory T cells (Tregs) and Th17 polarization.     

Mechanisms of blood-vascular reactions of the primate lung to acute endotoxemia

Previous studies have related structural and functional changes of the lung in shock to the syndrome of pulmonary leukocytosis (SPL) which is defined as rapid sequestration, degranulation and fragmentation of PMN-leukocytes in the pulmonary vascular bed. In the present study, in vivo and in vitro experiments were performed to investigate the mechanism and significance of ultrastructural changes associated with endotoxin-induced SPL. In rhesus monkeys infused with E. coli endotoxin (5 or 10 mg/kg), sequestered PMN-leukocytes revealed numerous digestive vacuoles containing characteristic membranous particles which were positively identified as particulate endotoxin. In places endotoxin particles were found to be incorporated in the matrix of leukocytic granules as well as in digestive vacuoles released intra-vascularly from fragmented leukocytes. These changes were associated with progressive degranulation of the PMN-leukocytes as well as multifocal damage to the endothelium of capillaries and arterioles which was demonstrable before the onset of significant leukocytic fragmentation. In addition, formation of digestive vacuoles and degranulation were found to be more prominent in sequestered rather than in circulating PMN-leukocytes. Platelet aggregates and fibrinous deposits in lung capillaries were virtually absent. In vitro endotoxin-leukocyte interaction reproduced all changes seen in sequestered PMN-leukocytes with the exception of leukocyte fragmentation. The results suggest that endotoxin-induced SPL in associated with early development of endothelial damage, and it is largely a manifestation of increased phagocytosis of endotoxin by the marginating PMN-leukocytes. The findings also provide strong ultrastructural evidence that phagocytized endotoxin results in direct injury to leukocyte lysosomes, which has not been reported to occur with phagocytosis of inert particles. The above evidence is consistent with previous biochemical data which indicated that endotoxin-induced enzyme release, and potential tissue injury, is greater than that observed with simple phagocytosis.     

NO-ergic innervation of digestive tract of Japanese anchovy (Engraulis japonicus)

This investigation was aimed at the study of distribution, localization and morphological peculiarities of NO-ergic cells and fibers in the digestive tract of Japanese anchovy Engraulis japonicus. Using the histochemical method developed by B.T. Hope and S.R. Vincent (1989), NO-ergic cells and fibers were demonstrated in the intermuscular plexus and in the circular layer of the muscular tunic in all the digestive tract organs studied. Single No-ergic cells were located in the longitudinal layer of the muscular tunic in the esophagus and stomach. In the submucosal plexus NO-ergic neurons were detected only in the stomach. The greatest density of NO-ergic cell distribution was characteristic to the posterior portion of the intestine and stomach.     

Ultrastructure of Myxidium trachinorum sp. nov. from the gallbladder of the lesser weever fish Echiichthys vipera

Myxidium trachinorum sp. nov. is described from the gallbladder of the lesser weever fish Echiichthys vipera. Pseudoplasmodia attach themselves to the gallbladder epithelium by filose processes, which are inserted between host cells. Pseudoplasmodia undergo endogenous cell formation at the secondary and tertiary levels. In the proliferative cycle, primary and endogenous cells are packed with digestive vacuoles formed by phagocytosis. In the sporogonic cycle the pseudoplasmodium becomes a pericyte enclosing two secondary cells (lacking digestive vacuoles) in a vacuole. These give rise to five cells each two valvogenic, two capsulogenic and a binucleate sporoplasm, which mature into spores. Comparison of the disporic M. trachinorum with polysporic species of Myxidium revealed significant differences in plasmodial ultrastructure, especially their attachments to host cells, surface characteristics and mode of nutrition, and in formation of generative cells. These suggest that the genus Myxidium may require revision.     

Homogeneity of Trypanosoma cruzi I, II, and III populations and the overlap of wild and domestic transmission cycles by Triatoma brasiliensis in northeastern Brazil

The genetic variability of 24 Trypanosoma cruzi isolates from humans (11) and triatomines (13) in northeastern Brazil was analyzed by random amplified polymorphic DNA (RAPD) and compared with taxonomic groups, host, and geographical origin of the parasite. TcI (12.5 %), TcII (45.8 %), and TcIII (41.6 %) showed a similarity coefficient (SC) of 0.74 using the mean of three primers and 0.80, 0.75, and 0.66 for λgt11-F, M13-40F, and L15996 primers, respectively. The samples were clustered according to their phylogenetic origin in two polymorphic and divergent branches: one associated with TcI and the other with two subbranches corresponding to TcII and TcIII. TcI was only identified in humans and correlated with the Id homogenous group (0.80 SC). TcII from humans and Triatoma brasiliensis showed 0.86 SC and was clustered according monoclonal or polyclonal populations with similar RAPD profiles detected among the vector and/or humans in different municipalities. TcIII was isolated exclusively in sylvatic cycles from T. brasiliensis and Panstrongylus lutzi and showed low variability (0.84 SC) and high homology mainly among isolated populations at the same locality. The homology of T. cruzi among different hosts and locations suggests the distribution of principal clones circulating and reveals an overlapping between the sylvatic and domestic cycles in this area, where T. brasiliensis infected with TcII acts as link in both environments. This species is important to maintain TcII and TcIII in wild cycles and deserves particular attention due an emergent risk of these populations being introduced into the domestic cycle; moreover, its clinical and epidemiological implications remain unknown.     

Calcium-containing, smooth-surfaced endoplasmic reticulum and vacuoles in cells of the blastopore-forming region during gastrulation of the newt, Cynops pyrrhogaster

Ultrastructural changes in cells of the blastopore-forming region (BFR) were examined during gastrulation of the newt, Cynops pyrrhogaster. Smooth-surfaced endoplasmic reticulum (sER), tubular in shape and with two types of vacuole, empty vacuoles and multilamellar vacuoles, appeared in cells of the BFR at the beginning of formation of the blastopore. The extent of the tubular sER increased during formation of the blastopore. With the deepening of the blastoporal groove, the tubular sER and multilamellar vacuoles disappeared in cells of the BFR. The empty vacuoles increased in number and appeared throughout the cytoplasm of the cells in the BFR and the marginal zone as formation of the archenteron progressed. Many large empty vacuoles were closely associated with deformed lipid droplets. Cytochemistry and X-ray microanalysis revealed the accumulation of calcium in the tubular sER and in some of the empty vacuoles. These results suggest important roles for the calcium-containing tubular sER in the regulation of the intracellular concentration of calcium during formation of the blastopore, as well as a role for empty vacuoles in the dissolution and consumption of lipid droplets during early gastrulation.     

Inhibitory Effect of Saponins and Polysaccharides from Radix Ranunculi Ternati on Human Gastric Cancer BGC823 Cells

The effects of different Radix ranunculi ternati extracts on human gastric cancer BGC823 cells were investigated, different methods were used to extract the saponins and polysaccharides from Radix ranunculi ternati, and MTT assay and colony formation assay were used to observe the effects of saponins and polysaccharides from Radix ranunculi ternati on in-vitro cultured human gastric cancer BGC823 cells. The results found that the saponins and polysaccharides from Radix Ranunculi Ternati had certain effects on both the growth and colony formation of human gastric cancer BGC823 cells, while improving the immune function of normal mice, of which saponins had more significant effects than polysaccharides.     

Lysosomal degradation of cell organelles. IV. Heterophagocytosis and acute inflammation in liver after intravenous injection of isolated liver-cell plasma membranes.

Isolated liver-cell plasma membranes were injected intravenously into a series of highly inbred rats. The uptake and digestion by Kupffer cells were followed by ultrastructural analysis in order to evaluate the capacity of lysosomes to degrade cellular membranes. By 1 to 5 min following administration, clusters of plasma membranes appeared in the sinusoidal lumens. Invaginations of the Kupffer-cell surfaces in combination with flap-like processes embraced the aggregates and formed endocytic vacuoles. Fibrinous deposits and platelet accumulation were sometimes observed at the surface of the Kupffer cells. At later time points (10 min to 2 hr) an increased number of plasma-membrane derivatives with trilaminar structures still recognizable was observed in large digestive vacuoles. In some focal areas, an acute inflammatory response was noted in the sinusoids often surrounding clusters of fibrin deposits, trapped erythrocytes, and aggregates of plasma membranes and platelets. At 8 hr there was a clearance from some digestive vacuoles of identifiable membranes with the appearance of dense homogeneous material; plasma membranes were still present in the sinusoids together with degranulating and degenerating leukocytes also phagocytizing plasma membranes. By 24 hr most of the inflammatory response had subsided. Many Kupffer cells resembled those in control animals although the digestive vacuoles or residual bodies contained numerous lipid-like droplets presumed to be remnants of membrane lipid digestion. By 2–5 days the Kupffer cells gradually became indistinguishable from the controls and the micropinocytosis vermiformis reappeared. It is concluded that plasma membranes after being phagocytized are digested within lysosomes. In contrast to mitochondria and microsomes (Glaumann et al., 1975ab; Glaumann and Trump, 1975), intravenous injections of plasma membranes gave rise to focally occurring thrombi which were surrounded by an acute transient inflammatory response.     

Prophylactic and Therapeutic Vaccination Using Dendritic Cells Primed with Peptide 10 Derived from the 43-Kilodalton Glycoprotein of Paracoccidioides brasiliensis

Vaccination with peptide 10 (P10), derived from the Paracoccidioides brasiliensis glycoprotein 43 (gp43), induces a Th1 response that protects mice in an intratracheal P. brasiliensis infection model. Combining P10 with complete Freund''s adjuvant (CFA) or other adjuvants further increases the peptide''s antifungal effect. Since dendritic cells (DCs) are up to 1,000-fold more efficient at activating T cells than CFA, we examined the impact of P10-primed bone-marrow-derived DC vaccination in mice. Splenocytes from mice immunized with P10 were stimulated in vitro with P10 or P10-primed DCs. T cell proliferation was significantly increased in the presence of P10-primed DCs compared to the peptide. The protective efficacy of P10-primed DCs was studied in an intratracheal P. brasiliensis model in BALB/c mice. Administration of P10-primed DCs prior to (via subcutaneous vaccination) or weeks after (via either subcutaneous or intravenous injection) P. brasiliensis infection decreased pulmonary damage and significantly reduced fungal burdens. The protective response mediated by the injection of primed DCs was characterized mainly by an increased production of gamma interferon (IFN-γ) and interleukin 12 (IL-12) and a reduction in IL-10 and IL-4 compared to those of infected mice that received saline or unprimed DCs. Hence, our data demonstrate the potential of P10-primed DCs as a vaccine capable of both the rapid protection against the development of serious paracoccidioidomycosis or the treatment of established P. brasiliensis disease.     

Signals from pancreatic mesoderm influence the expression of a pancreatic phenotype in hepatic stem-like cell line PHeSC-A2 in vitro: A preliminary study

The ex vivo generation of pancreatic cells from adult hepatic stem cells for subsequent transplantation has been proposed as a novel treatment for Diabetes mellitus. The pancreas and liver, closely related developmentally, may retain a shared (hepatopancreatic) stem cell whose plasticity could be exploited to differentiate into either lineage, dependent on environmental signals. This novel study investigated whether signals from pancreatic mesoderm could induce the differentiation of adult hepatic stem cell-like cells into pancreatic endocrine cells in vitro. A porcine hepatic stem-like cell line, designated PHeSC-A2, was co-cultured with quail pancreatic mesoderm in a Growth Factor Reduced Matrigel-Ham’s F12.ITS culture system. Immunocytochemical studies revealed insulin- and glucagon-producing cells. Assessment of nuclear morphology indicated that these endocrine cells were PHeSC-A2-derived. It is thus proposed that the PHeSC-A2 cell line has a higher level of plasticity than previously indicated. These preliminary results and assessment of published data have led to the following postulations: (a) permissive signaling from pancreatic mesoderm suffices to induce hepatic stem cells to assume a pancreatic lineage, (b) the pancreatic phenotype assumed by hepatic stem cells is a default state, (c) the differentiation capacity embodied by these cells indicates the existence of a hepatopancreatic stem cell lineage.     

Immunohistochemical study of the principal pancreatic islet of the toadfish, Halobatrachus didactylus (Pisces: Batrachoididae)

The endocrine pancreas of the toadfish, Halobatrachus didactylus, consists of one large circular principal islet (Brockman body) located in the dorsal side or neck region of the gallbladder, along with various accessory islets of variable sizes and shapes, embedded in the exocrine tissue located within the digestive organs connecting mesenteries. Islet cells showed variable shapes, angular or fusiform, with long cytoplasmic processes, granular cytoplasm, and a large eccentric nucleus. Cells were found scattered or as aggregates or cords. Four primary endocrine cell types immunoreactive for glucagon (α cells), insulin (β cells), somatostatin (δ cells), and pancreatic polypeptide (F cells) were identified within the toadfish principal islet. The α, δ, and F cells were located both at the periphery and in the central regions, while β cells, which were the predominant type, were present only in the central core. α and δ cells were found in moderate frequencies, while F cells were the least abundant. Macroscopically, the Brockman body of H. didactylus is visible as a milky white nodule separated from the exocrine tissue. Its size, location, and ease of extraction suggest that H. didactylus is suitable as experimental subject for biochemical, immunological, and physiological studies of the endocrine pancreas including in vitro investigations of hormone production, storage, and release.