Study of the myenteric and submucous plexuses after BAC treatment in the intestine of rats.

A morphological and quantitative study in the ileal and colonic myenteric and submucous plexuses of rats after BAC denervation was performed. Four groups were employed: SI--ileum control; CBI--denervated ileum; SC--colon control; and CBC--denervated colon. We used the Myosin-V immunohistochemistry technique to study the myenteric and submucous plexuses. In the submucous plexus of the ileum and colon there was not a significant decrease in the number of neurons/mm2 and of ganglia/mm2. The denervation of the myenteric plexus in the group CBI was 44.7% and in the group CBC, 68.3%. In the myenteric plexus there was also a significant decrease in the number of ganglia/mm2 (13.8% in group CBI and 52.14% in group CBC) and in the number of neurons/ganglion (33.9% in group CBI and 39.6% in group CBC). The morphological analyses showed that there was an alteration in the shape of the ganglia of the ileal and colonic myenteric plexus. The area of the cell bodies had a significant increase both in the myenteric and the submucous plexus in groups CBI and CBC. These data demonstrate that the BAC treatment causes morphologic and quantitative changes in the myenteric plexus and quantitative changes in the cell body area of the submucous plexus.     

Effect of age on the myosin-V immunoreactive myenteric neurons of rats ileum.

Alterations in the gastrointestinal neuromuscular function related to age have been demonstrated in human and animal models. This study analyzes the effects of the aging process on the area of the neuronal cell bodies of the myenteric plexus in the antimesenteric and intermediate regions of the ileal circumference of Wistar, 12 month-old in comparison 3 month-old animals. The ileum was removed and whole-mount preparations immunostained by the antibody anti-myosin-V were processed. The morphometric analyses were performed using a computerized image analysis system, with a subsequent distribution of neurons by size in intervals of 100 micro2. The cellular body morphometry revealed a significant increase in the size of the myosin-V- immunoreactive myenteric neurons from 12 month-old animals when compared with 3 month-old animals. However, significant differences between the regions were not observed; these observations were not age-dependent. The implications of these results in relation to the increase of the body weight, size of the small intestine, general organization of the myenteric plexus, staining method of neurons and the possible factors involved in the regulation and/or control of the volume of neronal cells due to aging, are discussed.     

Transplanted choroidal plexus epithelial cells can integrate with organotypic spinal cord slices into a new system

This study aimed to evaluate the integration of transplanted choroidal plexus epithelial cells with organotypic spinal cord slices. Organotypic spinal cord slices, normally cultured for 6 days, were divided into control group (Ctrl) and transplanted group (T). The choroidal plexus epithelial cells were dissociated and primary cultured (C group). The choroidal plexus epithelial cells cultured for 6–7 days were labeled by 1,1’-dioctadecyl-3,3,3’,3’-tetramethyl-indocarbocyanineperchlorate (CM-Dil), and were identified by transthyretin (TTR) in immunocytochemistry. They were adjusted to the density of 0.5–1 × 10⁷/ml, then 2 μl cells suspension were transplanted to the spinal cord slices in the T group. The same amount of basal medium was dripped on the spinal cord slices in the Ctrl group. After 14 days of transplantation, the differentiations into neurons and astrocytes, and the synapses were identified by immunofluorescence histochemistry. At the same time, the ratios of cell differentiations and synapses in new system, and the changes of MAPK signaling pathway were tested by western blotting. The choroid plexus epithelial cells were well labeled by CM-Dil and were immune-stained by TTR in immunocytochemistry. The choroid plexus epithelial cells bodies were small when transplanted on the spinal cord slices, but big when transplanted on the polyester membrane inserts. The transplanted cells could differentiate into astrocytes, and possibly differentiate into neurons, and there were a large number of synaptophysin positive vesicles between transplanted cells and organotypic spinal cord slices in immunofluorescence histochemistry. The levels of GFAP, TUB-III and synaptophysin in the T group were higher than which in the Ctrl and C groups in western blotting (P < 0.05). And the ratios of p-JNK/JNK and p-P38/P38 in the T group were significantly lower than which in the Ctrl and C groups (P < 0.05). But the ratio of p-ERK/ERK in the three groups was of no significant difference. The transplanted choroidal plexus epithelial cells can integrate with organotypic spinal cord slices into a new system.     

Morphoquantitative evaluation of the duodenal myenteric neuronal population in rats fed with hypoproteic ration.

The purpose of this work was to analyze the morphoquantitative behavior of the neurons of the myenteric plexus, as well as the morphometry of the duodenal wall, in adult rats fed with normoproteic (22%) and hypoproteic (8%) rations, killed at the age of 345 days. For neuronal assessments duodenal whole-mounts stained with the Giemsa method were used, and for the evaluation of the duodenal wall routine histological processing and staining with Hematoxilin-Eosin were employed. The means of the number of neurons in 80 microscopic fields (12.72 mm2) and of the size of the neuronal cell bodies did not reveal statistically significant differences between the groups, but there was a greater incidence of large neurons in the protein restriction group (RP). The duodenum was markedly smaller in the RP group and, although there was no difference in the thickness of its wall, the mucosa was larger and the muscular layer was smaller in group RP. It was concluded that the neuronal and non-neuronal components of the duodenum adjust themselves to the nutritional condition, assuring the maintenance of their functions.     

Microscopic study of certain age-related structural changes of maxillary sinus lining epithelium in albino rats

Mucociliary clearance is essential to maintain the defense function of the maxillary sinus; however, no literatures described the age changes in its lining epithelium. Therefore, the current work sought to describe the morphological postnatal age-related changes of maxillary sinus lining epithelium in rats using light, transmission, and scanning electron microscopes. Eighteen albino rats were divided into six groups according to their ages: 2-week-old, 1-month-old, 2-month-old, 3-month-old, adults, and senile rats. One-month-old-rats' group was the first to have recognizable maxillary sinus cavities that were lined by either single flat cellular layer or two distinct epithelial layers. These cells were devoid of microvilli and cilia, none of them showed evidence of differentiation into identifiable cell types. In 2- and 3-month-old rats, the mucosa of maxillary sinus started to be lined with pseudostratified epithelium with apparent increase in both microvilli and cilia. The first indication of goblet cell differentiation was observed in 3-month-old-rats. In the adult rats, the sinuses became completely lined by mature respiratory epithelium. However, in senile rats the epithelium exhibited polyps with clumped cilia and some areas of stratification and desquamation. Goblet cells were scanty and degenerating. The impaired mucociliary components (epithelium, cilia, and goblet cells' mucus) found in young and old ages of the current work might be correlated to human to explain predisposition of rhino-sinusitis in these age groups.     

Glucocorticoid-induced pnmt-immunoreactive sympathetic cells in the superior cervical ganglion of the rat

Light and electron microscopic immunocytochemical techniques were used to study the effect of glucocorticoids on the development of phenylethanolamine-N-methyltransferase (PNMT)-immunoreactive cells in the superior cervical ganglion (SCG) of early postnatal rats. Rats were injected daily with hydrocortisone acetate on postnatal days 2—6. The first PNMT-immunoreactive cells were detected 6 hours after the first glucocorticoid injection and their number increased after subsequent injections. No PNMT-immunoreactive cells were detected in uninjected controls. PNMT-immunoreactive fibres were seen in the ganglion 6 hours after the first glucocorticoid injection. The PNMT-immunoreactive cells consistently showed processes 2 days after beginning the glucocorticoid treatment, and long processes and fibre networks were seen in ganglia of 7-day-old rats. However, no PNMT-immunoreactive fibres were seen in the iris, which is innervated by the SCG. Ultrastructurally, most of the PNMT-immunoreactive cells had the look of small granule-containing (SGC) cells, including heterochromatin clumps along the nuclear envelope and in the center of the nucleoplasm as well as dense core vesicles. SGC cells, nonimmunoreactive to PNMT antiserum, also were seen. However, some PNMT-immunoreactive cells showed ultrastructural characteristics of nerve cells. In contrast to the SGC cells, these cells were characterized by a voluminous cytoplasm, dispersed nuclear heterochromatin, and a lack of granular vesicles. These results demonstrate that glucocorticoids induce PNMT immunoreactivity both in SGC cells and also in cells with characteristics of principal neurons.     

Effects of food restriction on motoneuronal loss with advancing age in the rat

The effects of life-long food restriction on motoneuronal cell death with advancing age was studied in male Fischer rats, which had access to food only 3 days a week after weaning (FR rats). Motoneurons innervating the medial gastrocnemius muscle were labeled with retrogradely transported HRP. The number of labeled motoneurons in FR rats and rats fed ad libitum (AL rats) was similar at the age of 16 months (131.8 +/- 1.7 for FR rats vs. 133.8 +/- 4.5 for AL rats). However, at 28 months of age, AL rats had less labeled motoneurons compared to FR rats (117.0 +/- 2.4 for FR rats vs. 124.3 +/- 7.0 for FR rats). The number of type I muscle fibers in the medial gastrocnemius muscle increased significantly in AL rats during the period from 16 to 28 months of age, which might reflect motor unit reorganization following retraction of axons and/or death of innervating motoneurons. FR rats did not show statistically significant alteration. These findings were also true for the data compiled from several different experiments including those conducted for primarily different purposes in our laboratory. The results suggest that life-long food restriction retards motoneuronal cell death occurring with advancing age.     

Cell death in the choroid plexus following transient forebrain global ischemia in the rat

Following a complete disruption of blood flow to the brain, cerebral ischemia, a specific neuronal population, namely the CA1 pyramidal neurons in the hippocampus, will die a delayed type of cell death. This is often referred to as "delayed neuronal death" (DND). It is not known why it takes around 48 hours for these cells to die. It is very often speculated that events, intrinsic to the CA1 neurons, regulate their demise, whereas it is less often considered that extrinsic mechanisms also could play an important role for the development of DND. We discovered that in addition to the CA1 pyramidal neurons, cells in the choroid plexus were TUNEL (terminaldeoxynucleotidyl-mediated biotin-dUTP nick-end labeling)-positive following transient forebrain global ischemia. The time course and the number of TUNEL-positive cells were determined. A dramatic increase in the number of TUNEL-positive cells in the choroid plexus was seen at 18, 24, and at 36 hours of recovery, but not at 48 hours of recovery following 15 minutes of transient forebrain global ischemia. No TUNEL-positive cells were seen at 24 hours of recovery in the CA1 region. The cell death in the choroid plexus thus preceded the occurrence of cell death in the CA1 region. Massive cell death in the choroid plexus will inevitably lead to a leaky blood-CSF barrier, which in turn will allow substances to enter the ventricular system and from there reach the brain parenchyma. We, therefore, conclude that choroid plexus cell death may adversely affect the outcome of CA1 pyramidal neurons following transient forebrain global ischemia, through, e.g., a disruption of the blood-cerebro spinal fluid barrier. Alternatively, the choroid plexus may produce factors, which can affect the outcome of neurons.     

Glucose‐dependent insulinotropic polypeptide–producing K cells in dexamethasone‐treated rats

Some studies indicate that diabetes mellitus exerts an influence on the gastrointestinal tract and its diffuse neuroendocrine system (DNES) in regard to cellular density and neuroendocrine content. Since there is no data about relationship between experimentally induced non–insulin‐dependent (type 2) diabetes mellitus (NIDDM) on the gut K cells, the aim of our study was to investigate immunohistochemical, stereological and ultrastructural changes of rat K cells after 12 days of dexamethasone treatment. Twenty male Wistar rats aged 30 days were given daily intraperitoneally 2 mg kg^–1 dexamethasone (group DEX, 10 rats) or saline (group C, 10 rats) for 12 days. Tissue specimens were obtained from each antrum with corpus and different parts of the small (SI) and large intestine (LI) of all animals. Immunohistochemistry was carried out using antisera against the GIP and insulin. Transmission electron microscopy was also used. Although, according to the literature data, rat K cells are present in the duodenum and jejunum and, to a lesser extent, in the ileum, in the present study we observed that those cells were abundant also in all parts of the LI. We observed generally that GIP‐producing K cells were augmented in all parts of SI and decreased in the LI of DEX rats. Insulin immunoreactivity (ir) coexpressed with GIP‐ir in K cells and was stronger in the SI of DEX rats as compared with C rats. We also found by electron microscopy that small intestinal K cells have features not only of GIP‐secreted but also of insulin‐secreted cells. We concluded that dexamethasone treatment caused proliferation of K cells in the rat SI, and simultaneously transformation of GIP‐producing K cells to insulin‐synthesizing cells.     

Prenatal development and histochemical characteristics of gastrointestinal mucins in sheep fetuses

The object of this study was to describe the prenatal development and histochemical properties of mucins in the sheep gastrointestinal tract. To determine changes in the mucin profile, the sections were stained with specific histochemical stains for carbohydrates. While neutral and mixed mucins were observed in the superficial epithelial cells of the abomasal pyloric region, acidic mucins were detected in the secretory ducts and corpus of the glands. Acidic mucins consisted predominantly of sialomucins. In the duodenal villi, the number of goblet cells containing neutral mucins increased toward the end of gestation, whereas Brunner's glands contained acidic mucins until the 95th day of gestation and both acidic and neutral mucins thereafter. The jejunal goblet cells contained either acidic, neutral, or mixed mucins. Goblet cells containing acidic mucins, which were mainly localized to the ileal crypts and villi, mostly contained sulfated mucins. While villi were observed in the proximal colon until the 115th day of gestation, later the typical crypt structure emerged. During the period in which the villi were found in the proximal colon, the goblet cells containing sulphomucins were predominant, whereas the goblet cells containing sialomucins were predominant after the typical crypt structure was formed. In conclusion, gastrointestinal mucins may be involved in the formation of meconium during the prenatal period, and acidic mucins may contribute to the strength of the intestinal barrier against pathogens and digestive enzymes, as the barrier is not fully functional after birth.     

Morphological analysis of colon goblet cells and submucosa in type I diabetic rats submitted to physical training

Colon layers, especially the submucosa, as well as the secretion of goblet cells are extremely important for the functioning and transit of substances in this organ. However, the damages arising from type I diabetes and the effects of physical training, which plays crucial role in the treatment of this disease, are not yet known in these regions. To analyze the changes in colon submucosa and goblet cells of diabetic rats, as well as the effects of physical training, Wistar rats were divided into four groups: sedentary control, trained control, sedentary diabetic (SD), and trained diabetic (TD). The training protocol consisted of swimming for 60 min a day, 5 days per week, during 8 weeks. Colon samples were collected, processed, and evaluated by histochemical and ultrastructural techniques. Goblet and submucosa cells did not show alterations in shape, size, protein and carbohydrate content, in all treatment groups. Decreased amount of collagen fibers, however, was observed in the submucosa and lamina propria of SD rats, but this alteration was recovered in TDs. The ultrastructural analysis, in turn, revealed greater quantity of Golgi apparatus cisterns in SDs, distinctly than TDs, which showed improvement in this diabetic condition. Thus, physical training was responsible for the recovery of some important diabetic alterations, possibly improving the motility of substances in the large intestine. Nevertheless, it cannot be considered alone in the treatment of this disease, requiring the combined practice of other methods.     

Extrusion of colonic epithelial cells in vitro

Rat colonic mucosae fixed in situ in Ussing chambers provided a model of the extrusion of absorptive enterocytes and less commonly of goblet and enteroendocrine cells. The cells were lost at extrusion zones midway between crypt mouths. Even in mucosae in which the number of extruding cells was large, epithelial continuity was maintained as evaluated morphologically and electrophysiologically. Beneath points of remaining contact between desquamating cells and the epithelial sheet, microfilaments of the terminal web formed band-like structures linking adjacent junctional complexes. Freeze-fracture replicas disclosed extensive macular regions of tight junction strands in the plasma membranes of desquamating cells. Tight junctions between newly neighboring cells were often irregular and often occurred beneath the terminal web region. Dithio-threitol enhanced cell loss and increased basal epithelial conductance, but histological continuity was maintained and the mucosae continued to respond typically to bradykinin. These observations suggest that during the loss of senescent enterocytes, tight junctions are maintained; old junctional elements are lost, and tight junctions are formed between remaining adjacent cells. This model offers a means to study the synthesis and turnover of tight junctions and the maintenance of the colonic epithelial barrier.     

Porcine Choroid plexus epithelial cells in culture: regulation of barrier properties and transport processes

The epithelial cells of the choroid plexus are the structural basis of the blood-cerebrospinal fluid (CSF)-barrier. Here we summarise our recent efforts to culture those cells mainly on permeable supports in vitro. Isolated from porcine brains, we report a simple protocol for the primary culture using cytosine arabinoside as an additive that is cytotoxic for other cells except the plexus epithelial cells. Enhanced barrier properties are obtained by withdrawal of serum from the culture medium after confluency is reached. Cells improve their polarity, permeability for hydrophilic substrates is lowered, electrical resistance is increased tenfold, and a pH-gradient is built up across the cell monolayer. Polarised secretion of proteins and most importantly fluid secretion into the apical filter compartment was attained and proven to be dependent on the Na(+),K(+)-ATPase activity. Active transport processes (penicillin G, riboflavin, myo-inositol, ascorbic acid) were studied and clearly showed the involvement of the organic anion transporter. The permeability of the barrier was found to be regulated by cyclic adenosine monophosphate (cAMP). Moreover, we report that cell proliferation and differentiation is controlled by components of the extracellular matrix. The present culture model could now be used as an in vitro system to quantify drug transport across the blood-CSF-barrier.     

Effects of the ascorbic acid supplementation on NADH-diaphorase myenteric neurons in the duodenum of diabetic rats.

We assessed the ascorbic acid (AA) supplementation on the myenteric neurons in the duodenum of rats. Fifteen rats with 90 days of age were divided into three groups: control (C), diabetics (D) and ascorbic acid treated diabetics (DA). After 120 days of daily treatment with AA, the duodenum was submitted to the NADH-diaphorase (NADH-d) histochemical technique, which allowed us to evaluate the neuronal density in an area of 8.96 mm2 for each duodenum, and also to measure the cellular profile area of 500 neurons per group. The supplementation promoted an increase on AA levels. The neuronal density (p < 0.05) was higher in the group DA when compared to group D. There were no significant differences in the neuronal areas, when we compared groups C (204 +/- 16.5) and D (146.3 +/- 35.84) to groups D and DA (184.5 +/- 5.6) (p > 0.05). The AA-supplementation avoided the density reduction of the NADHd myenteric neurons in the duodenum of diabetic rats.     

Mechanisms of CSF secretion by the choroid plexus

The epithelial cells of the choroid plexus secrete cerebrospinal fluid (CSF), by a process that involves the movement of Na(+), Cl(-) and HCO(3)(-) from the blood to the ventricles of the brain. This creates the osmotic gradient, which drives the secretion of H(2)O. The unidirectional movement of the ions is achieved due to the polarity of the epithelium, i.e., the ion transport proteins in the blood-facing (basolateral) are different to those in the ventricular (apical) membranes. Saito and Wright (1983) proposed a model for secretion by the amphibian choroid plexus, in which secretion was dependent on activity of HCO(3)(-) channels in the apical membrane. The patch clamp method has now been used to study the ion channels expressed in rat choroid plexus. Two potassium channels have been observed that have a role in maintaining the membrane potential of the epithelial cell, and in regulating the transport of K(+) across the epithelium. An inward-rectifying anion channel has also been identified, which is closely related to ClC-2 channels, and has a significant HCO(3)(-) permeability. This channel is expressed in the apical membrane of the epithelium where it may play an important role in CSF secretion. A model of CSF secretion by the mammalian choroid plexus is proposed that accommodates these channels and other data on the expression of transport proteins in the choroid plexus.     

Morphology of the intralobular duct of the submandibular gland in rats in case of experimental diabetes mellitus

The objective of study is to study the peculiarities of morphological changes in different subdivisions of the intralobular duct of the submandibular gland (SMG) in rats in case of experimental diabetes mellitus (DM). The study included sexually mature male Wistar rats. Experimental DM was induced by streptozotocin. Electron microscopic study of subdivisions of the intralobular duct of the SMG was carried out on the 14th, 28th, 42nd, 56th, and 70th days of the experiment. In early stages of experimental DM the intercalated ducts are characterized by a relatively unchanged structure, and in late stages vacuolization of the cytoplasm of their epithelial cells is observed. Since the 14th day vacuolization of mitochondria is observed in epithelial cells of the granular ducts being the most pronounced on the 28th day and not apparent over the subsequent periods. The degree of filling with granules reduces till 56th day, however, it increases sligthly on the last day of the experiment. On the 28th–70th days vacuolization of the cytoplasm is observed in epithelial cells of the striated ducts. In addition, on the 14th day the mitochondrial matrix of these cells condenses; over the next periods it becomes enlightened and mitochondrial cristae are clearly visualized and disorganized. Conclusion: In the intralobular duct of the SMG in experimental DM dystrophic changes of different intensity occur in the granular and striated ducts on the 14th day and in the intercalated ducts only since the 42nd day of the experiment.     

Effect of tissue non-specific alkaline phosphatase in maintenance of structure of murine colon and stomach

The gastrointestinal tract of mammals secretes a phospholipid-rich membrane that is enriched in alkaline phosphatase (AP) and surfactant proteins (surfactant-like particle, SLP). The production of this particle is stimulated in the small intestine by fat feeding and in cultured cells in vitro by transfection with intestinal alkaline phosphatase (IAP). To test whether tissue non-specific alkaline phosphatase (TNAP) was a factor in stimulating surfactant-like particle production in stomach and colon (tissues expressing TNAP), mice lacking this enzyme were studied. Mice were harvested at 8 days of life, when body weight of homozygous animals (TNAP -/-) was about half that of congenic controls (TNAP +/+) or heterozygotes (TNAP +/-), but before seizures had begun. No difference in content of the major SLP protein (65 kDa) by Western blotting or immunocytochemistry was seen in stomach or colon of TNAP -/- vs. TNAP +/+ animals, but the content was only about half in the IAP-expressing small bowel. Transmission electron microscopy of the TNAP -/- small bowel showed large dilated lysosomes and residual bodies. Colonocytes and gastric surface epithelial cells from the same animals showed mitochondria containing homogeneous dense inclusions, consistent with neutral lipid. In the underweight homozygous animals, there was a decrease in the neuronal content of submucosal ganglia in the jejunum and ileum and of myenteric ganglia in the jejunum of TNAP -/- animals. These findings suggest that (1) TNAP is not important in maintaining surfactant-like particle content of tissues that express TNAP, (2) normal fat absorption is important in maintaining SLP content in the small intestine, and (3) TNAP is important in the maintenance of some intestinal structures, and perhaps their function.     

Hypoxia induced apoptosis of rat gastric mucosal cells by activating autophagy through HIF-1α/TERT/mTORC1 pathway

The pathogenesis of high altitude-related gastric mucosal injury remains poorly understood, this study aimed to investigate the role of autophagy in hypoxia-induced apoptosis of rat gastric mucosal cells. Rats were randomized into four groups which were maintained at an altitude of 400 m (P) or received no treatment (H), autophagy inducer rapamycin (H+AI) or autophagy inhibitor 3-MA (H+AB) at an altitude of 4,300 m for 1, 7, 14 and 21 days, respectively, and the morphology, ultrastructure, autophagy, and apoptosis of gastric mucosal tissues were examined. Gastric mucosal epithelial cells CC-R039 were cultured under conditions of normoxia, 2% O2 (hypoxia), or 2% O2+anti-mTORC1 for 0, 24, 48, and 72 h, respectively, and the autophagy and apoptosis were analyzed. CC-R039 cells were transfected with siHIF-1α, siTERT, or siRNA and the autophagy was examined. The results showed that the exposure to hypoxia increased the autophagy and apoptosis of gastric mucosal cells in rats, and apoptosis was aggravated by rapamycin treatment but alleviated by 3-MA treatment. Increased duration of hypoxia from 0 to 72 h could increase the autophagy and apoptosis but decrease the proliferation of gastric mucosal cells. Inhibition of mTORC1 with rapamycin led to further increase in apoptosis and even substantial cell death, and inhibition of HIF- 1α and TERT increased mTORC1 expression and reduced autophagy. Moreover, the inhibition of HIF-1α reduced TERT expression. In conclusion, hypoxia could induce apoptosis of rat gastric mucosal cells by activating autophagy through HIF-1α/TERT/mTORC1 pathway     

Surface ultrastructure of gills in relation to the feeding ecology of an angler catfish Chaca chaca (Siluriformes,Chacidae)

Surface ultrastructure of the gills of the angler catfish Chaca chaca was investigated to unravel the adaptive modifications associated with the feeding ecology of the fish. The fish is often found in mud or in soft substrates where they remain buried both for protection and to feed. Gill rakers present on the gill arch in most fish species are absent in this fish. The absence of gill rakers are associated with the feeding habit of the fish and is considered to facilitate the swallowing of captured prey smoothly without any hindrance. Highly corrugated surface of the gill arch and gill filaments could be associated to retain water/mucus to prevent dessicassion of the fish. Papillae like epithelial protuberances each bearing a taste bud at its summit toward the pharyngeal side of the gill arch is associated with the sorting of the food. Large number of mucous goblet cells on the gill arch epithelium are considered to secret copious mucus to lubricate the prey for easy swallowing. In C. chaca the gill septa between gill filaments are reduced. This could enhance the flexibility and permit the free movement of the gill filaments. Extensive secondary lamellae and infrequent mucous goblet cells on secondary lamellae are associated to increase the surface area to enhance efficiency of gaseous exchange.     

The changes of gap junctions between pituitary folliculo‐stellate cells during the postnatal development of zucker fatty and lean rats

We investigated the effect of leptin on the postnatal development of gap junctions between folliculo‐stellate cells by using Zucker fatty (fa/fa) rats that have defects of the functional leptin receptor. Male Zucker fatty rats (fa/fa) and male Zucker lean rats (+/+) were used at each of the following postnatal ages: 20, 30, 40, 50, 60, 70, 80, 90 days, and 1 year. On one of the aforementioned dates, the anterior pituitary glands were prepared for observation by transmission electron microscopy. We quantified the number of follicles and gap junctions, and calculated the rate of occurrence as the ratio of the number of gap junctions existing between folliculo‐stellate cells per intersected follicular profile. In Zucker lean male rats, the number of gap junctions remained relatively constant from days 50 to 90 (0.44 ± 0.02 to 0.49 ± 0.03), and was similar in 1 year old rats (0.47 ± 0.03). These data were statistically higher compared to Zucker fatty male rats. In Zucker fatty male rats, very few gap junctions were observed in 30‐day‐old rats (0.04 ± 0.01: mean ± SE). This disruption of gap junction formation persisted, and the number of gap junctions remained constant and showed a low level from days 40 to 90 (0.11 ± 0.02 to 0.17 ± 0.02); this finding was similar in 1‐year‐old rats (0.17 ± 0.02). These observations indicate that the effect of leptin over the gap junction formation within the anterior pituitary glands was directly mediated by interaction with the functional leptin receptor present on the folliculo‐stellate cells. Microsc. Res. Tech. 77:31–36, 2014. © 2013 Wiley Periodicals, Inc.