[Show abstract][Hide abstract] ABSTRACT: We investigated the cellular mechanisms underlying spontaneous contractions in the mouse renal pelvis, regulated by calcitonin gene-related peptide (CGRP).
Spontaneous contractions, action potentials and Ca2+ transients in typical and atypical smooth muscle cells (TSMCs and ATSMCs) within the renal pelvis wall were recorded separately using tension and intracellular microelectrode recording techniques and Fluo-4 Ca2+ imaging. Immunohistochemical and electron microscopic studies were also carried out.
Bundles of CGRP containing transient receptor potential cation channel, subfamily V, member 1-positive sensory nerves were situated near both TSMCs and ATSMCs. Nerve stimulation reduced the frequency but augmented the amplitude and duration of spontaneous phasic contractions, action potentials and Ca2+ transients in TSMCs. CGRP and agents increasing internal cyclic adenosine monophosphate (cAMP) mimicked the nerve-mediated modulation of TSMC activity and suppressed ATSMCs Ca2+ transients. Membrane hyperpolarization induced by CGRP or cAMP stimulators was blocked by glibenclamide, while their negative chronotropic effects were less affected. Glibenclamide enhanced TSMC Ca2+ transients but inhibited ATSMC Ca2+ transients, while both 5-hydroxydecanoate and diazoxide, a blocker and opener of mitochondrial ATP-sensitive K+ channels, respectively, reduced the Ca2+ transient frequency in both TSMCs and ATSMCs. Inhibition of mitochondrial function blocked ATSMCs Ca2+ transients and inhibited spontaneous excitation of TSMCs.
The negative chronotropic effects of CGRP result primarily from suppression of ATSMC Ca2+ transients rather than opening of plasmalemmal ATP-sensitive K+ channels in TSMCs. The positive inotropic effects of CGRP may derive from activation of TSMC L-type Ca2+ channels. Mitochondrial Ca2+ handling in ATSMCs also plays a critical role in generating Ca2+ transients.
British Journal of Pharmacology 12/2009; 158(8):2030-45. DOI:10.1111/j.1476-5381.2009.00514.x · 4.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Since [Westlud, K.N., Chils, G.V., 1982. Localization of serotonin fibers in the rat adenohypophysis. Endocrinology 111, 1761-1763] initially identified the serotonin nerve fibers in the anterior pituitary gland, attention has been paid to the rostral zone of the anterior lobe into which nerve fibers enter and subsequently spread to deeper regions of the lobe. The rostral zone is the trifurcated junction of the partes tuberalis, intermedia and distalis, and has the important role(s) for hormone secretion via the "transitional zone" [Sato, G, Shirasawa, N, Sakuma, E, Sato, Y, Asai, Y, Wada, I, Horiuchi, O, Sakamoto, A, Herbert, DC, Soji, T, 2005a. Intercellular communications within the rat anterior pituitary. XI: An immunohistochemical study of distributions of S-100 positive cells in the anterior pituitary of the rat. Tissue and Cell 37, 269-280.]. The objective of this study was to focus on the ultrastructure of this "zone." All of the animals studied were fixed by perfusion with glutaraldehyde via the left ventricle of the heart and examined by electron microscopy. In the "transitional zone," a cluster of neuronal elements was observed between the folliculo-stellate cell-rich area and the anterior lobe. This cluster consisted of myelinated fibers, unmyelinated fibers, neuroendocrine fibers, large cells, and supporting cells. The large cells were perikarya of neurons which made a "ganglion-like" structure with associated satellite cells. Agranular, folliculo-stellate cells were intermingled among the elements. This is the first report that neuronal elements form clusters in the "transitional zone." A relationship of the unmyelinated and neuroendocrine fibers in the basal layer and in the "transitional zone" is discussed.
Tissue and Cell 07/2008; 40(3):157-66. DOI:10.1016/j.tice.2007.07.006 · 1.25 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Although exercise is believed to reduce the risk of rupture of the myotendinous junction, exercise-induced structural changes in this region have not been studied. We examined exercise-induced ultrastructural changes in the myotendinous junction of the lower legs in rats.
Ten adult male LETO rats were used. Five rats were randomly placed in the Exercise group; the remaining five were used as controls and placed in the non-Exercise group. Running exercise was performed every day for 4 weeks. The tibialis anterior and gastrocnemius muscles were then removed from both legs from each animal in the two groups. The specimens were subsequently examined by transmission electron microscopy (TEM). Numerous finger-like processes were observed at the myotendinous junction. The changes in frequency of branching of the finger-like process (the number of times one finger-like process branched) and the direction of the processes (the angle of the major axis of a finger-like process to the longitudinal direction of the muscle fiber) were studied. To evaluate the two indicators above, each 10 fingerlike process was randomly and separately selected from the tibialis anterior and gastrocnemius muscles of rats, providing 50 finger-like processes of both muscles for evaluation per group.
In terms of the frequency of branching of the fingerlike processes, the mean values obtained in the non-Exercise group were 0.04 and 0.18 times, respectively, in the tibialis anterior and gastrocnemius muscles and were 0.38 and 1.16 times, respectively, in these two muscles in the Exercise group. Regarding the direction of the finger-like processes, the values were 4.1 degrees and 3.6 degrees, respectively in the non-Exercise group and 10.4 degrees and 14.5 degrees , respectively in the Exercise group. The differences between the two animal groups were significant.
Morphological changes in the myotendinous junction occurred as an adaptation to tension increased by exercise.
[Show abstract][Hide abstract] ABSTRACT: We investigated the effects of bladder outlet obstruction (BOO) on the distribution of interstitial cells (ICs) in the guinea-pig bladder.
Bladder overactivity of BOO animals was validated with urodynamic studies. Immunohistochemical analyses for Kit and vimentin as markers for ICs were performed on both BOO and control bladders. Morphological and functional properties of detrusor smooth muscle (DSM) were examined with alpha-smooth muscle actin staining and intracellular recording, respectively. Electron microscopy was also carried out to characterize ultrastructural morphology of ICs.
Two weeks after surgery, BOO animals showed an increased voiding frequency and a reduced voiding volume. Filling cystometry demonstrated a frequent incidence of non-voiding contractions, a reduced interval between voiding contractions and an increased voiding pressure in BOO bladders. In BOO bladders, the thickness of suburothelial and subserosal connective tissue layers was increased, whilst that of detrusor smooth muscle (DSM) layer was less affected. Population of Kit or vimentin immunoreactive ICs was increased in subserosal layers, and their distribution was altered in suburotherial layer in BOO bladders. Neither alpha-actin immunoreactivity nor spontaneous electrical activity of DSM was altered in BOO bladders. ICs were characterized by their numerous mitochondria and caveolae, and had a close contact with each other and with neighboring DSM or nerves.
These results demonstrated the increased population of ICs in the BOO guinea-pig model for the first time, and suggest that the altered distribution of ICs may contribute to the pathophysiology of bladder overactivity.
Neurourology and Urodynamics 04/2008; 27(4):330-40. DOI:10.1002/nau.20502 · 2.87 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A 92-year-old Japanese woman was found to have the sternoclavicularis anticus muscles existing bilaterally during the course of educational dissection at Nagoya City University Medical School. It was confirmed that these muscles received the nerve supply from small branches of the lateral pectoral nerves from the brachial plexus. Herein is documented the precise gross anatomical findings with some morphometric measurements. Moreover, the morphology of this muscle is discussed in relation to previously described variations of the pectoral sheet of muscles.
Anatomical Science International 01/2008; 82(4):237-41. DOI:10.1111/j.1447-073X.2007.00167.x · 0.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Although numerous investigators in 1970s to 1980s have reported the distribution of LH-RH nerve fibers in the median eminence, a few LH-RH fibers have been shown to be present in the pars tuberalis. The significance of the finding remains to be elucidated, and there are few studies on the distribution of LH-RH neurons in the pars tuberalis, especially in the dorsal pars tuberalis (DPT). Adult male Wistar-Imamichi rats were separated into two groups: one for electron microscopy and the other for immunohistochemistry to observe LH-RH and neurofilaments. Pituitary glands attached to the brain were fixed by perfusion, and the sections were prepared parallel to the sagittal plane. The typical glandular structure of the pars tuberalis was evident beneath the bottom floor of the third ventricle, and the thick glandular structure was present in the foremost region. Closer to the anterior lobe, the glandular structure changed to be a thin layer, and it was again observed at the posterior portion. Then the pituitary stalk was surrounded with the dorsal, lateral, and ventral pars tuberalis. LH-RH and neurofilaments fibers were noted in the bottom floor, and some of them vertically descended to the gland. Adjacent to the glandular folliculostellate cells in the pars tuberalis, Herring bodies with numerous dense granules invading into the gland were present between the pituitary stalk and DPT. It was postulated that the "message" carried by LH-RH might have been transmitted to the cells in the DPT to aid in the modulation of LH release.
The Anatomical Record Advances in Integrative Anatomy and Evolutionary Biology 11/2007; 290(11):1388-98. DOI:10.1002/ar.20596 · 1.54 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A category of the spherical granules contains two types of granules such as a filled granule and a cored vesicle. The spherical granules were counted to separate the filled granule and the cored vesicle. Ten mixed-breed dogs were separated into two groups. One was the control group, and the other was experimental DM using Streptozotocin at sub cutaneous. The experimental ani-mals were selected if their blood glucose concentrations were over 300mg/dl.The obtained pancreases were then prepared for transmission electron microscope. To distinguish the granules, serial sections were employed. Each type of granule was counted and analyzed sta-tistically by the Student t-test. The β -cells of the dog pancreatic islets displayed many rod-shaped secretory granules with a few that were spherical and cored vesicles. These granules were mainly located around a well-developed Golgi apparatus. Whereas the granules extrusion of the cord vesicle were of-ten observed, the extrusion of the rod-shaped granule were observed few. No extrusion of the spherical granule were observed. The granules classified as rod-shaped, spherical, and cored vesicle were counted. Mean values of the number of granules in the β -cells were counted in 50 cells in each animal. The granule number in the experimental animals was decreased. The ratio of rod-shaped granule between the control and DM dogs was ap-proximately 6.6:1 and of the cored vesicle was 8.1:1. The ratio of both the rod-shaped and cored vesicle between the control and DM dogs was similar. Then the functional differentia-tion of two types of spherical granules was discussed.
[Show abstract][Hide abstract] ABSTRACT: The secretory granules of the ß-cells (ß-granules) in the pancreatic islets differ in shape in different animals. Whether ß-granules are made entirely of insulin or not is unknown. Ten mixed-breed dogs were used and separated into two groups. One was a control group and the other served as those with experimental diabetes mellitus (DM) and received injec- tions of Streptozotocin. After the injections, blood glucose was checked on day 14. The pan- creas was removed after fixation by perfusion and post-fixed with Caulfield's fixative. The specimens were then processed and observed under an transmission electron microscope (TEM). Immunocytochemistry using antibodies to insulin was also performed. The ß-cells in the DM animals were reduced in size and displayed fewer electron dense granules. Additionally, almost all of the cell organelles had decreased in number. Immuno- cytochemical observations of the control ß-cells showed a strong positive reaction on the rod-shaped and spherical granules. The number of rod-shaped granules in control dogs ranged from 3299 to 3559, while in DM animals they varied from 374 to 602. The spherical granules in the controls numbered between 168 and 295 as compared to the DM dogs which ranged from 394 to 706 in each animal. The ratio of rod-shaped and spherical granules in the controls was 5:1 and in the DM dogs 1:1. It was understood that the diminution in the total number of granules in the DM dogs was mainly due to a decrease of rod-shaped gran- ules. It is assumed that the rod-shaped granule corresponded to proinsulin, the storage form of the insulin, and the spherical granules to the active form of insulin. However, there have been no reports discussing this relationship. The present study demonstrated that the ß- granules, especially rod-shaped granules decreased in DM animals, whereas the percentage of spherical granules remained the same or were even elevated compared to the normal, controls. Thus, it is believed that Streptozotocin mainly attacked the pathway where pre- proinsulin is converted to proinsulin.
[Show abstract][Hide abstract] ABSTRACT: We encountered the co-existence of an aberrant origin of the right subclavian artery and a myocardial bridge on the left anterior descending coronary artery in the cadaver of an 80-year-old Japanese woman during the course of educational dissection at Nagoya City University Medical School. We document the precise gross anatomical findings with some morphometric measurements. Neither an aberrant origin of the right subclavian artery nor the cardial myocardial bridge is a very rare anomaly, but a case of both anomalies being found in the same body is very rare. We believe this is the first report of the simultaneous occurrence of these two anomalies.
[Show abstract][Hide abstract] ABSTRACT: We have identified a mutant human immunodeficiency virus type 1 (HIV-1) CRF01_AE that contains a single nucleotide mutation in gag gene from 4 HIV-1 seronegative drug users in Thailand. We found A to G mutation at the nucleotide position 75 of gag p17 gene (A75G) not changing the amino acid sequence. The mutant HIV-1 molecular clones were examined for their replication capability. Although the mutation dramatically reduced the level of virion production, it did not affect the amounts of viral protein synthesis within the transfected cells. In addition, this mutation did not affect the levels of Gag polyproteins. Furthermore, electron microscopic examinations have revealed a dramatic reduction of the virion production and perturbation of viral morphogenesis at the cytoplasmic membrane. These results indicate that the A75G mutation is attributable to the long-term sero-negativity of individuals at high risk of HIV-1 infection and suggest a novel mechanism that regulates HIV production.
Nucleic Acids Symposium Series 02/2005; DOI:10.1093/nass/49.1.99
[Show abstract][Hide abstract] ABSTRACT: We encountered the absence of the tendon to the fourth toe of the extensor digitorum longus muscle of the right leg in the body of a 73-year-old Japanese woman during the course of educational dissection at Nagoya City University Medical School. The tendon to the fourth toe of the extensor digitorum longus muscle was solely absent. To our knowledge, this anatomical variation has never been cited in the medical literature. We document the precise gross anatomical findings with some morphometric measurements. Moreover, we discuss the morphology of this anomaly in relation to previously described variations and anomalies of the extensor digitorum longus muscle.
Anatomical Science International 01/2005; 79(4):235-8. DOI:10.1111/j.1447-073x.2004.00082.x · 0.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Male Wistar-Imamichi rats were used for light and electron microscopic study. Prior to the appearance of the pars tuberalis (PT), a small cluster of arteries was found in the area where the gland would appear, while an array of capillaries was noted at the bottom of the median eminence (ME). The epithelial structure comprising the PT was first observed along with slender arteries approximately 1mm behind the optic chiasm on both sides of the ME. Although numerous thin capillaries were present in the hypothalamus, thick capillaries (thought to be portal vessels) showed unusually large luminal diameters and were noted attached to the ME, slightly posterior to the PT. In all specimens serially sectioned in the frontal plane, veins were not detected on either the ME or the pituitary stalk, nor was smooth muscle present in the wall of the thick capillaries. Where the pars tuberalis and the anterior lobe adjoined, clusters of agranular and a few granular cells were noted along with several thick capillaries located on the ventral side of the pituitary. Ultrastructurally, numerous capillaries, which were categorized into two groups, were observed between the agranular cells in the PT. One was thin-walled and randomly arranged while the other was thick-walled and contained fenestrations. At the inter-capillary space, connective tissue and interstitial cells were observed. In the PT, bundles of the neuroendocrine fibers, which contained many electron dense granules and mitochondria, were frequent around the capillaries. The cytoarchitecture of the portal vessels and their functional role are discussed in relation to that previously reported.
[Show abstract][Hide abstract] ABSTRACT: The distribution of LH-RH-positive nerve fibers in the median eminence was demonstrated in the 1970s and 1980s. A few LH-RH fibers have been reported to be present in the adjacent pars tuberalis of the pituitary, but their functional significance has not been clarified and still remains enigmatic. Adult male Wistar-Imamichi rats were separated into two groups: one for immunohistochemistry of LH-RH and S-100 protein (for the identification of folliculo-stellate cells) and the other for electron microscopy. For both immunohistochemistry and electron microscopy, the specimens obtained contained the pituitary gland connected with the hypothalamus. Numerous LH-RH-positive fibers were observed as tiny lines with several varicosities both on the primary vascular plexus and in the hypothalamus corresponding to the posterior half of the portal vein area. LH-RH-positive fibers were also noted around S-100-positive cells in the pars tuberalis. Weakly reactive S-100 cells were scattered in the pars tuberalis in the midsagittal plane, while clusters of strong reactive elements occurred 100-300 microm from the center. Similar observations were made using fluorescence immunohistochemistry for LH-RH and S-100, and at the electron-microscopic level. At the posterior portion of the portal vein system, bundles of the LH-RH-immunoreactive fibers invaded the pars tuberalis and terminated on agranular cells. Gap junctions were clearly seen among agranular cells corresponding to folliculo-stellate cells. It is postulated that the LH-RH message might be transmitted not only by the established hypophyseal portal vein system but also via the folliculo-stellate cells in the pars tuberalis to aid in the modulation of LH release.
Cell and Tissue Research 08/2004; 317(1):79-90. DOI:10.1007/s00441-003-0851-9 · 3.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Since Rinehart and Farquhar reported the presence of agranulated cells in the anterior pituitary gland in 1953, the functions of the folliculo-stellate cell remain to be clarified. Intercellular junctions have been described in the monkey, rat, and teleost anterior pituitary glands, indicating the existence of cell-to-cell communication within the organ. We pointed to their possible role in the rapid dissemination of information through a complex interconnecting system of follicles involving gap junctions. The gap junctional/folliculo-stellate cellular network was essential in the maturation and regulation of the pituitary gland system such as the hypothalamic-pituitary-gonadal axis. It has been was shown that a network participated in the conduction of electrophysiological information over a long distance using the ion Ca(++), which propagates to other folliculo-stellate cells by signaling through gap junctions. Sixty-day-old male rats were used in this study for light microscopic immunohistochemistry of S-100 protein, type I collagen, and connexin 43, and for electron microscopy to observe the morphological relationships between the cellular networks of folliculo-stellate cells and granulated pituitary cells. Clusters of anti-S-100 protein-positive cells were clearly observed in a region of the hypophysis tentatively named the transition zone. Anti-S-100 protein-positive cells and their cytoplasmic processes were also present in the anterior lobe and assembled together to form follicular lumina. Type I collagen was clearly shown outlining the incomplete lobular or ductule-like structure making cell cords in the anterior pituitary gland. Numerous microvilli were present within the follicular lumen while around the lumina, junctional specializations including gap junctions were positive for the connexin 43 protein. A nonuniform distribution of the connexin 43-positive sites were observed. Small or dot-shaped positive sites were noted where two clusters of cells were connected; the cells were identified as S-100 cells. Double immunohistochemical staining of the connexin 43 and growth hormone (GH) or connexin 43 and luteinizing hormone (LH) was also performed, demonstrating no direct relationship between the connexin 43 and either the GH or LH cells. These findings indicate that there are two kinds of messages necessary for the hormone release in the pituitary gland. One is via the portal vein system, the other is through the gap junction-mediated networks of folliculo-stellate cells. The granulated cells directly associate with cell membrane of folliculo-stellate cells are able to discharge secretory granules through communication via gap junctions, while those granulated cells that are more distant from the folliculo-stellate cells are only able to discharge hormones via the pituitary hormone-releasing hormone from the portal vein system.
The Anatomical Record Part A Discoveries in Molecular Cellular and Evolutionary Biology 05/2004; 278(1):462-73. DOI:10.1002/ar.a.20040
[Show abstract][Hide abstract] ABSTRACT: The pars tuberalis has been generally understood as a simple forward elongation of the glandular pituitary that develops into an architecturally similar structure. In rats, it is also believed that the pars tuberalis completely encircles the infundibular stalk at the ventral portion of hypothalamus. Intact Wistar-Imamichi rats were used in the present study, and frontal and sagittal serial sections of the pituitary gland/brain complex were prepared. Serial sections were stained with hematoxylin-eosin and with antibodies to LH-RH, S-100 protein or LH-RH receptor. Electron microscopic analyses were also conducted. The anatomical end of the epithelial structure of the pars tuberalis was observed at approximately 1 mm behind the optic chiasm. At this point, both the capillaries and the pars tuberalis spread and interdigitated over the median eminence. The pars tuberalis did not, however, completely encircle the pituitary stalk. Electron microscopic observations revealed some profiles of neuroendocrine nerve elements that were also present between the agranular cells of the pars tuberalis. A few LH-RH-positive nerve fibers were initially found just behind the optic chiasm, while the number of LH-RH-positive reactions increased around the capillary vessels. These reactions then decreased significantly and were sparsely distributed both in the diencephalon and in the area near the pituitary stalk where the two separated. LH-RH receptors were observed on S-100 protein-positive cells in the pars tuberalis. The present observations show the significance of the pars tuberalis and its relationship between the anterior pituitary gland and the hypothalamus as organs that possibly form another collaborating mechanism for the regulation of hormone secretion of the anterior pituitary gland.
Acta histochemica et cytochemica official journal of the Japan Society of Histochemistry and Cytochemistry 01/2004; 37(4):227-239. DOI:10.1267/ahc.37.227 · 1.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The reduced function that is played by the endothelium has been suggested in the pathophysiologic condition of resistance arteries during preeclampsia. Our aim was to determine whether morphologic changes occur in these arteries in patients with preeclampsia.
The omental resistance arteries were isolated from 11 women with preeclampsia and 10 normotensive pregnant women; the preparations were analyzed by light and electron microscopy.
On light microscopic examination, no differences were apparent between both groups of women in cross-sectional preparations of the omental resistance arteries. However, after electron microscopic examination, characteristic changes were found in the subendothelial region of the resistance arteries from women with preeclampsia compared with specimens from normotensive pregnant women. The thickness of elastic lamina was irregular, and the basement membrane was, in part, incomplete. Thus, the arrangement of the location of endothelial cells was changed in the resistance arteries that were taken from women with preeclampsia.
These results indicate that ultrastructural changes develop in the subendothelial region of omental resistance arteries in women with preeclampsia.
American Journal of Obstetrics and Gynecology 08/2003; 189(1):216-21. DOI:10.1067/mob.2003.445 · 4.70 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The role of local endogenous angiotensin II (Ang II) in endothelial function in resistance arteries was investigated using rabbit mesenteric resistance arteries. First, the presence of immunoreactive Ang II together with Ang II type-1 receptor (AT1R) and angiotensin converting enzyme (ACE) was confirmed in these arteries. In endothelium-intact strips, the AT1R-blocker olmesartan (1 microM) and the ACE-inhibitor temocaprilat (1 microM) each enhanced the ACh (0.03 microM)-induced relaxation during the contraction induced by noradrenaline (NA, 10 microM). Similar effects were obtained using CV-11974 (another AT1R blocker) and enalaprilat (another ACE inhibitor). The nitric-oxide-synthase inhibitor NG-nitro-L-arginine (L-NNA) abolished the above effect of olmesartan. In endothelium-denuded strips, olmesartan enhanced the relaxation induced by the NO donor NOC-7 (10 nM). Olmesartan had no effect on cGMP production (1) in endothelium-intact strips (in the absence or presence of ACh) or (2) in endothelium-denuded strips (in the absence or presence of NOC-7). In beta-escin-skinned strips, 8-bromoguanosine 3',5' cyclic monophosphate (8-Br-cGMP, 0.01-1 microM) concentration dependently inhibited the contractions induced (a) by 0.3 microM Ca2+ in the presence of NA+GTP and (b) by 0.2 microM Ca2++GTPgammaS. Olmesartan significantly enhanced, while Ang II (0.1 nM) significantly inhibited, the 8-Br-cGMP-induced relaxation. We propose the novel hypothesis that in these arteries, Ang II localized within smooth muscle cells activates AT1Rs and inhibits ACh-induced, endothelium-dependent relaxation at least partly by inhibiting the action of cGMP on these cells.
The Journal of Physiology 06/2003; 548(Pt 3):893-906. DOI:10.1113/jphysiol.2002.034116 · 5.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Many studies have described the ultrastructure of the dorsal root ganglia in various embryonic and adult animals, but in spite of the efforts of many investigators the functional role of the satellite cells in this tissue is not clearly understood. In this study, we discuss the function of this cell type based on the concept of cell-to-cell interaction through gap junctions. Five male 60 day-old Wistar strain rats were used. All animals were anesthetized with pentobarbital and perfused with glutaraldehyde fixative, then the dorsal root ganglia in levels L4, L5 and L6 were taken from each rat. After postosmication, the specimens were prepared for observation by transmission electron microscopy. All nerve cells were completely surrounded by satellite cell cytoplasmic expansions. The boundaries between adjacent nerve cells and satellite cells were complicated due to the presence of perikaryal projections of nerve cells. Gap junctions which showed the typical trilamellar structure of plasma membranes were found mainly between satellite cell processes belonging to the same nerve cell. On the other hand, some gap junctions were found between the satellite cell projections belonging to different nerve cells. The size of the gap junctions ranged from 300 to 400 nm. No gap junctions were associated with the plasma membrane of any nerve cell. In conclusion, only satellite cells can share free transcellular exchange of cytoplasmic molecules such as ions, amino acids, sugars and several second messengers including cAMP and inositol 1,4,5-triphosphate by way of gap junctions in dorsal root ganglia.
[Show abstract][Hide abstract] ABSTRACT: The size of a substance is a major factor determining whether it can permeate the wall of synovial capillaries. The maximum diameter of particles that can move across the synovial capillary wall has generally been thought to be 50 nm. We studied the permeability of the synovial capillaries of the rat between day 20 and 30 after birth using a polystyrene particle whose diameter was 240 nm. In addition using lecithin-coated polystyrene particles, we studied the maturation of the barrier function supported by endothelial and peripheral cells against foreign bodies. Lecithin-coated particles were found within the fibroblast-like synovial cells near the capillary in the 20 day-old rats, while non-coated particles remained in the endothelial wall and in the peripheral cells of capillaries. In the 30 day-old rats, lecithin-coated particles were present in the peripheral cells and the neighboring synovial cells; however, the non-coated particles were never found in the synovial or perisynovial cells. The present study shows that the size of the transportable substance by transcytosis may be larger than previously thought. Furthermore, the synovial capillaries functionally changed between day 20 and 30 suggesting that active movement of the joint led to the functional maturation of the synovial capillaries.
[Show abstract][Hide abstract] ABSTRACT: Folliculo-stellate (FS) cell are agranular and arranged around a follicle. They contain the S-100 protein and beta-adrenergic receptors. It has been suggested that they can act as stem cells, since they show mitotic figures, and could transform into granular or chromophilic cells according to the concept of a "cell renewal system." Cell-to-cell interactions among pituitary cells have been described, and recent progress with freeze-fracture electron microscopy has provided novel observations of the cell surface and gap junctions within the rat or teleost fish pituitary gland, or in cultured rat pituitary cells. In adult rats, the anterior pituitary was composed of lobules incompletely separated by a basement membrane. Follicles consisted exclusively of FS cells. Gap junctions were observed only between adjacent FS cells, in rare cases on the tips of their cytoplasmic processes. Thus, the FS cells, connected by gap junctions, made up a dense cellular network throughout the pituitary. Gap and tight junctions were absent on granular cells. Elongated follicles with columnar FS cells were observed in 10-day-old rats and were separated into smaller units. The number of gap junctions rapidly increased with age until 40-45 days of age. Few S-100 protein positive cells were observed on day 10, along the marginal cell layer and near the so-called postero-lateral wing. The frequency of positive cells increased with age and by day 40; numerous cells were observed throughout the anterior lobe. Gap junction number also varied with the stage of the estrous cycle, and frequency; during diestrus, they were half of that during proestrus or estrus. The number of gap junctions increased in late pregnancy and in lactating rats, probably due to changes in estrogen and progesterone. Hormone (LH-RH and testosterone) treated groups of rats showed accelerated development by almost 10 days, compared with controls. In castrated male rats, the ultrastructure of the pituitary remained immature even at 40 days of age, when the number of gap junctions was a quarter or less than the number in intact rats. Testosterone treatment restored the frequency of gap junctions to a normal level. We conclude that the appearance of gap junctions in the pituitary cells and maturation of the gland are dependent to a large degree upon gonadal steroids.
Microscopy Research and Technique 10/1997; 39(2):138-49. DOI:10.1002/(SICI)1097-0029(19971015)39:2<138::AID-JEMT5>3.0.CO;2-H · 1.15 Impact Factor