bluuebunny/crossref_metadata_2025 huggingface dataset:
The ultrastructure of rapid‐frozen, substitution fixed parotid gland acinar cells of the mongolian gerbil (Meriones meridianus)
Authors: Ichikawa Atsushi , Ichikawa Misao , Hirokawa Nobutaka
Published: February 2005

The ultrastructure of gerbil parotid gland acinar cells studied by rapid freezing in liquid nitrogen and freeze‐substituting with OsO4 was similar in general to conventionally prepared tissue, but different in several aspects. Acceptable preservation was limited to about 10 μm of the surface; the secretory granule membrane was a single dense line, while all others were trilaminar; the dense‐cored secretory granule had a rim of low density which was homogeneous; there were many continuous profiles between the Golgi lamellae, vesicles, and vacuoles; and mitochondria were long and arborized.
The origin and differentiation of enteric neurons of the intestine of the fowl embryo
Authors: Allan I. J. , Newgreen D. F.
Published: February 2005

Neuroblasts were identified histologically in the intestine of the fowl embryo of stages 25 to 35 (Hamburger and Hamilton, ′51). These cells occurred rostral to the umbilicus at stage 26, and appeared caudally in a wave that reached the coprodeum at stage 34. The presence of histologically unidentifiable neuronal precursors was studied by grafting onto the chorio‐allantoic membrane (CAM) short lengths of gut from embryos of stage 24 to 34. After growth in isolation on the CAM, the resultant gut grafts were examined histologically for enteric neurons. In these grafts, neuronal differentiation occurred in the gut as a wave moving caudally at about 40 ḿm/hr. This wave preceded by less than 12 hours the normal appearance of neuroblasts at any particular level of the intestine.

The findings are discussed with regard to previous reports on the origin of enteric neurons. The most likely conclusion is that all enteric neurons in the fowl are derived from vagal neural crest. The results obtained with grafts containing neurons of Remak's nerve, in addition to intestine, suggest that lumbo‐sacral neural crest may give rise to some enteric supporting cells which, in the absence of normal enteric plexuses, differentiate as pigment cells. If lumbo‐sacral neural crest cells contribute to post‐umbilical enteric neurons, their differentiation requires the presence of vagal cells.

A comparison of enteric neuronal density and distribution in short and long colo‐rectal grafts suggests that only the advancing front of the neuronal precursor wave is necessary to populate the remainder of the gut. This high proliferative potential in the wave‐front appears to decline on reaching the most caudal colo‐rectum and coprodeum.
Ultrastructure of merkel cells in the hard palate of the squirrel monkey (Saimiri sciureus)
Authors: Garant P. R. , Feldman J. , Cho M. I. , Cullen M. R.
Published: February 2005

The distribution and ultrastructure of Merkel cells in the hard palate was investigated in the squirrel monkey (Saimiri sciureus) after fixation by vascular perfusion. Merkel cells were clustered at the base of the epithelial rete pegs of the hard palate. They were characterized by concentrations of dense‐cored granules and closely associated intraepithelial nerve endings. Numerous spiny processes extending from the Merkel cell were intercalated with adjacent keratinocytes, probably serving to detect and amplify movement of adjacent cells. These spiny processes contained a rigid core of parallel microfilaments which were interrelated with cytoplasmic filament bundles located beneath the cell membrane. Transitional cells containing dense‐cored granules and well developed tonofibrils appear to be related to both Merkel cells and keratinocytes.

The findings of this study suggest that Merkel cells are highly adapted for detection of movement in adjacent keratinocytes, as well as movement of the epithelium with respect to the underlying connective tissue.
The bicellular and reflexive membrane junctions of renomedullary interstitial cells: Functional implications of reflexive gap junctions
Authors: Majack Richard Allen , Larsen William James
Published: February 2005

Renomedullary interstitial cells are loosely organized within the interstitial space surrounding collecting ducts, limbs of Henle, and capillaries of the rat renal medulla. These cells possess long processes, which interact with each other and with cell bodies to form bicellular tight, intermediate, and gap junctions. In addition, both cell bodies and cell processess “reflexive” gap and intermediate junctions. Possible functions of renomedullary interstitial cell membrane junctions are discussed. Particular attention is given to a consideration of the functional significance of “reflexive” gap junctions.
Structural remodelling of bat thyroid parafollicular (C) cells during development
Authors: Nunez Eladio A. , Gershon Michael D.
Published: February 2005

The development of bat parafollicular (C) cells was evaluated by electron microscopy from the time of early thyroid formation, through the neonatal period, to young adulthood. Parafollicular cells were relatively few in number (3%) at the earliest developmental stage examined, but increased with subsequent fetal stages, reaching a relatively stable level of 28% of parenchymal cell volume just prior to birth. Fetal parafollicular cells were packed with calcitonin granules. Following birth, however, parafollicular cells were totally or almost totally depleted of calcitonin granules. Moreover, another cell type that resembled the parafollicular cell was also found. This cell contained tiny granules which often contained two dense cores. Parafollicular cells of maturing, juvenile bats were characterized by the massive accumulation of secretory material within the cisternae of the rough surfaced endoplasmic reticulum and a great deal of autophagy. Remarkably, none of these changes were found in young, adult bat parafollicular cells. In conclusion, this study provides morphological evidence to support the view that parafollicular cells play a role in developing mammals.
Calcium and the secretory cycle of prolactin cells: A cytochemical and ultrastructural study of dopamine inhibition and monobutyryl cyclic AMP‐Stimulation of prolactin secretion
Authors: Yancey S. Barbara , Weiner Richard , Schechter Joel
Published: February 2005

To identify intracellular calcium pools that may be involved in the secretory process in prolactin (PRL) cells, hemi pituitaries were incubated in medium containing 10−6 M dopamine, 5 mM cyclic cAMP (experimentals), or in medium alone (controls) and then processed for electron microscopy using potassium pyroantimonate to localize intracellular calcium. PRL in the medium was measured by radioimmunoassay. The concentration of antimonate associated with mitochondria, Golgi saccules, and secretory granules was estimated. Dopamine inhibition of PRL secretion (>80% at 1, 2, 3 h) resulted in accumulation of secretory granules in all stages of maturation and dilation of Golgi saccules at 2 and 3 h, accompanied by increased mitochondrial antimonate and increased Golgi‐associated antimonate. Cyclic AMP stimulation of secretion (635% at 5 min., declining to 34% at 1 h) resulted in marked exocytosis at 5 and 15 min., declining after 30 min. Mitochondrial antimonate decreased after 30 min. Stimulated cells exhibited numerous coated membrane structures at or near exocytotic pits and an amassing of microvesicles at the margin of the Golgi apparatus. Although some secretory granules consistently exhibited reactivity to antimonate (unchanged by inhibition or stimulation), plasma membrane, and granule membrane translocated to the plasma membrane during exocytosis, were not reactive.
Three‐dimensional architecture of the cortical region of the golgi apparatus in rat spermatids
Authors: Hermo L. , Rambourg A. , Clermont Y.
Published: February 2005

Glutaraldehyde‐fixed testes were impregnated with the Ur‐Pb‐Cu technique of Thiéry and Rambourg (′76) or postfixed in ferrocyanide‐reduced osmium (Karnovsky, ′71). Thin and thick (0.5 μm) sections were examined with a Philips 400 electron microscope at 80 or 100 kv. Stereopairs were prepared from pictures of the same field after tilting the specimen every 6° from the −45 degree to the +45 degree position of EM goniometric stage. The cortex of the compact hemispherical Golgi apparatus of young spermatids (steps 2–8) was found to be composed of saccular and intersaccular regions similar to those described in the Golgi apparatus of Sertoli cells (Rambourg et al., 1979). In the saccular region, the stacks were composed of three to nine parallel saccules perforated with pores of various dimensions. On the mature or trans‐face of the stack, one or two membranous elements with a wider lumen were either closely applied to the overlying saccules or were separated from them and intermixed with the vesicular components of the medulla. On the forming or cis‐face of the stack, three or four saccules were frequently interrupted by gaps in register from one saccule to another. In three dimensions, these gaps appeared as pan‐shaped spaces or “wells,” often containing a few vesicles. Immediately overlying the first saccule on the cis‐face, a regular network of anastomotic tubules was present, corresponding to the cis‐osmiophilic element observed in other cell types. In the intersaccular region, membranous tubules connected to the edges of the saccules branched, intertwined, anastomosed, and bridged adjacent stacks of saccules. Such membranous tubules bridged saccules with the cis‐osmiophilic element or saccules of the same stack. Between the ER cisternae capping the surface of the Golgi apparatus and the cis‐network of anastomotic tubules, there was a space called the peripheral Golgi region containing small vesicles and membranous tortuous tubules. The vesicles were frequently arranged in clusters that were capped by an ER cisterna and displayed a size gradient from the periphery to the center of the cluster. Thus, although there were similarities between the three‐dimensional architectures of the Golgi apparatus in Sertoli cells and young spermatids (e.g., saccular and intersaccular regions), several structural features distinguished the spermatid's Golgi apparatus.
Ultrastructural study of a blood‐muscle spindle barrier after systemic administration of horseradish peroxidase
Authors: Dow Pierre R. , Shinn Susan L. , Ovalle William K.
Published: February 2005

The permeability of the normal muscle spindle capsule to the entrance of an exogenous protein tracer was assessed by the use of horseradish peroxidase (HRP). Adult mice were injected intravenously with a solution of HRP (MW 40,000). After varying intervals, ranging from two to 240 minutes, animals were perfused aortically with fixative, and anterior tibialis muscles were removed, processed, and examined. The results were evaluated by electron microscopic cytochemical techniques, and attention was directed to the movement of tracer and its relationship to the outer and inner capsule of the muscle spindle.

HRP was first demonstrated in cytoplasmic vesicles crossing the continuous capillary endothelium supplying the muscle spindle, and was then detected in the interstitial space surrounding the outer capsule. In polar regions, HRP had entered the periaxial space by two minutes, and it was seen in cytoplasmic vesicles of the attenuated outer capsule. Later, HRP abutted the sarcolemma of intrafusal fibers, and by 12.5 minutes there was evidence of tracer in T‐tubules of these muscle cells. Whereas at no time was tracer observed traversing any of the numerous intercellular junctions of the capsule, it appeared that polar regions were leaky and open‐ended at their distal portions.

The sensory equatorial zone was considerably less permeable to the entrance of tracer. Whereas HRP was visible initially in cytoplasmic vesicles of the subjacent capillary endothelium, it was not until 12.5 minutes that tracer could be demonstrated within some vesicles of equatorial outer capsule cells. At later times, a small amount of HRP was observed in the equatorial periaxial space, where it was phagocytosed and finally sequestered by cells of the inner capsule as membrane‐bound lysosomal deposits. Consequently, at no time was tracer incorporated into either intrafusal fibers or their sensory nerve terminals.

Thus, in contrast to polar regions, the muscle spindle capsule in the equatorial zone appears to be effective in preventing the indiscriminate penetration of HRP from the bloodstream. This suggests dissimilar paths of tracer movement from the microvasculature into sensory and non‐sensory regions of the muscle spindle.
EMG of the interosseous and lumbrical muscles in the chimpanzee (Pan troglodytes) hand during locomotion
Authors: Susman Randall L. , Stern Jack T.
Published: February 2005

The interosseous, lumbrical, and extensor digitorum communis muscles of the human hand constitute a complex apparatus that acts to move and stabilize the fingers during grasping and manipulation. A telemetered electromyographic study of these muscles in chimpanzees was undertaken to determine whether use of the hand in locomotion and to maintain postures might be associated with functional roles different from those in humans. The manual interossei of chimpanzees are recruited in metacarpophalangeal flexion and in rapid interphalangeal joint extension. Slow digital extension can be accomplished solely by the extensor digitorum communis and lumbricals. The highly variable activity of the interossei during knuckle‐walking is compatible with their roles as ab/adductors and rotators, but such movements could not be accurately assessed. It is concluded that the generalized suspensory and specialized terrestrial locomotion of the chimpanzee is not associated with major changes in the function of the manual interossei and lumbricals.
Scanning electron microscopic studies of the surface morphology of the vomeronasal epithelium and olfactory epithelium of garter snakes
Authors: Wang Ruu Tong , Halpern Mimi
Published: February 2005

Fixed vomeronasal and olfactory epithelia from normal adult garter snakes were microdissected, fractured, and examined with a scanning electron microscope. The method permits a detailed comparative study of the structural organization and morphological characteristics of the constituent cells of the vomeronasal and olfactory epithelia. Despite similarities in the nomenclature of the constituent cells in both epithelia, significant differences exist in their surface morphology. A unique columnar structure composed of non‐neuronal elements is present in the vomeronasal epithelium. These columns house the bipolar neurons and undifferentiated cells. Such a columnar organization is absent in the olfactory epithelium. In the vomeronasal epithelium the bipolar neurons possess microvillous terminals at their dendritic tips, while the dendritic tips of the bipolar neurons of the olfactory epithelium possess cilia. Vomeronasal supporting cells are covered with microvilli, while olfactory supporting cells are covered with cytoplasmic protuberances in addition to the microvilli. In the vomeronasal epithelium the pear‐shaped neurons have a grossly smooth surface and are organized into clusters, while in the olfactory epithelium the elliptical bipolar neurons are spinous, aligned side‐by‐side and interdigitate. The basal (undifferentiated) cell layer in the vomeronasal epithelium has a high packing density and is composed of several layers of irregularly shaped cells. In the olfactory epithelium the basal cell layer is loosely organized and composed of a single layer of oval cells. This information on the three‐dimensional cell structure of both epithelia provides a basis for experimental observations on changes in morphology of the bipolar neurons during genesis, development, maturation, degeneration, and regeneration in postnatal, adult animals.
Megakaryocytopoiesis in the spleen of growing rats
Authors: Grouls V. , Helpap B.
Published: February 2005

Age‐dependent changes in splenic megakaryocytopoiesis of Wistar rats, 1 hour to 60 days old, were investigated using autoradiograms of semithin sections. The highest values for 3H‐thymidine labeling and mitotic indices were observed immediately after birth, whereas the maximal concentration of megakaryocytes was seen on the 14th day after birth. The transit time of megakaryocytes in newly born rats was 34.5 hours and, thus, much shorter than in adult animals.
Skeletal muscle fiber splitting with weight‐lifting exercise in rats
Authors: Ho Kwok‐Wai , Roy R. R. , Tweedle C. D. , Heusner W. W. , van Huss W. D. , Carrow R. E.
Published: February 2005

Adult male albino rats were assigned randomly to control (CON) and weight‐lifting (WL) groups. The WL rats were subjected to a progressive weight‐lifting program against high resistance for 8 weeks. During the last 2 weeks, each WL rat lifted a load equal to 130% of its body weight. The mean weight of the adductor longus muscle was significantly increased in the WL group (p < 0.05). This increased muscle weight was shown to be due to an increase in the number of fibers per unit cross‐sectional area (p < 0.05), and the mean sizes of both fast‐twitch oxidative glycolytic and slow‐twitch oxidative fibers were significantly smaller in the WL rats than in the CON rats (p < 0.05). Light and electron microscopic examination showed that five out of eight WL rats exhibited longitudinally split muscle fibers, while only one CON rat had a few centrally placed nuclei. The splitting process appeared as either a “pinching‐off” of a small segment from the parent fiber or an invagination of the sarcolemma deep into the muscle fiber in a plane parallel to the sarcomeres. There were preliminary indications that this work‐induced fiber‐splitting process may be a physiological adaptation of muscle to the stress of exercise.
Ultrastructural localization of enkephalin‐like immunoreactivity in the rat adrenal medulla
Authors: Hervonen Antti , Pelto‐Huikko Markku , Linnoila Ilona
Published: February 2005

The PAP method was applied to adrenomedullary cells to demonstrate the subcellular localization of ELI. The labeled cell‐groups were identified from flat‐embedded virbratome sections by light microscopy. Electron microscopy showed that the precipitate was associated with the storage granules of the cells. The number of labeled granules varied greatly from cell to cell. In cells corresponding to those showing heavy staining by light microscopy, all the granules were stained with precipitate. It is suggested that the peptide responsible for the ELI might be released together with the catecholamines.
Gap junctions in early amphibian embryos
Authors: Hanna R. B. , Model P. G. , Spray D. C. , Bennett M. V. L. , Harris A. L.
Published: February 2005

Cell pairs from late cleavage and early blastula Ambystoma mexicanum embryos were found to be electrotonically coupled. Thin‐section electron microscopy revealed typical gap junctions between the cells. Freeze‐fracture electron microscopy showed the gap junctions to be comprised of aggregations of 8.5‐nm P‐face particles and corresponding E‐face pits. The conductance of the amphibian embryonic gap junction is known to be voltage‐dependent, but no obvious gating structure was resolved by these morphological techniques.
Cupular secretion by Xenopus laevis line organs: Autoradiographic evidence for incorporation of 3H‐glucose and 35S‐sulfate
Authors: Cornford Marcia E. , Barajas Luciano
Published: February 2005

Autoradiographic evidence for incorporation of 3H‐glucose and 35S‐sulfate into the cupulae of Xenopus laevis (African clawed toad) lateral line organs was obtained after injection into the dorsal lymph sacs of adult animals. Time intervals of 15 minutes to 4 hours after administration of these labeled metabolic precursors were used to examine the time course of the apparent mechanism of growth of the cupulae. Our results suggest that the two layers of accessory cells (the sustentacular cells and inner layer of mantle cells), concentrically arranged around the organ's central sensory (hair) cells, elaborate distinct cupular components. Sustentacular cells, immediately adjacent to the sensory cells, appear to produce and extrude at their exposed apices a cupular “core” substance labeled by 3H‐glucose, but not by 35S‐sulfate. The layer of inner mantle cells, external to the sustentacular cells, was labeled by both precursors and is spatially situated to secrete a cupular sheath enclosing the cupular core. Ultrastructural differences between the secretory products within the two cell types were marked. Electron microscopic autoradiography of toads killed 4 hours after 3H‐glucose injection showed that silver grains were associated with accumulations of the respective secretory products in sustentacular and inner mantle cells, and label was found over the cupular trough area, where the bases of the cupulae are attached. These results suggest that the cupular core and sheath may both contain mucopolysaccharide, and the sheath, a sulfated mucopolysaccharide.
Transplantation of brain tissue in the brain of rat. I. Growth characteristics of neocortical transplants from embryos of different ages
Authors: Das Gopal D. , Hallas Brian H. , Das Kunda G.
Published: February 2005

Differential growth of neural transplants as related to the age of the donor embryos was investigated in this study. Neocortical tissue of constant volume, obtained from embryos of 15, 16, 17, 18, 19, 20, and 21 days' gestational age, was transplanted into the cerebellum of 10‐day‐old rats. The fully grown transplants were analyzed quantitatively and qualitatively 90 days after transplantation. The ultimate volume of the transplants and the estimated total number of neurons in them followed a gradient in relation to the age of the donor embryos. At one extreme, the neural transplants from 15‐day‐old embryos grew very large, showing a 21‐fold increase in size, and at the other extreme, those from 21‐day‐old embryos grew less than two‐fold in volume. These differences were determined by the developmental history of the transplants. Neural tissue obtained from 15‐day‐old embryos contained predominantly neuroepithelial cells which continued to proliferate even after transplantation. This resulted in the large size of these transplants. At the other extreme, neural tissue from 21‐day‐old embryos contained predominantly preformed neuroblasts, and they simply differentiated after transplantation. Due to this, the transplants were small in size. Neural tissues obtained from other embryos of different gestational ages between these two extremes contained neuroepithelial cells and preformed neuroblasts in differential ratios. The number of neuroepithelial cells in the transplants and their differential proliferative activity after transplantation, and the number of neuroblasts present, determined the differential sizes of these transplants. In histological preparations, all transplants were seen to contain normal‐looking and well‐differentiated neurons, and normal‐looking neuropil. The transplants were integrated with the host brain, in that there was neither any gap nor any scar tissue between the transplants and the host neural tissue surrounding them. Neither the transplants nor the host brains showed any pathological reaction or neoplastic growth.
The subcellular localization of immunoglobulin in mouse plasma cells, as studied with immunoferritin cytochemistry on ultrathin frozen sections
Authors: Geuze Hans J. , Slot Jan W.
Published: February 2005

Cells of mineral oil‐induced plasmacytomas (MOPC) and normal plasma cells from mouse lymph nodes were used to study the intracellular localization of IgG by means of immunoferritin cytochemistry on ultrathin frozen sections. IgG was demonstrated in the rough endoplasmic reticulum, in virus‐containing smooth ER of the tumor cells, in peripheral elements at the cis‐side of the Golgi complex, and in all Golgi cisternae. It is suggested that the peripheral elements transfer IgG molecules from the RER to the Golgi complex. Vacuoles showing a strong immunoreaction occurred at the trans‐side of the Golgi complex. These vacuoles were normal in lymph node plasma cells and were occasionally seen in the tumor plasma cells. It is proposed that these vacuoles carry IgG from the Golgi complex to the cell membrane and, hence, can be considered as secretory vacuoles.
The cytologic composition of primate laryngeal chemosensory corpuscles
Authors: Idé Chizuka , Munger Bryce L.
Published: February 2005

The present study defines the cellular composition of chemosensory corpuscles (taste buds) present in the mucosa overlying the arytenoid cartilages of the larynx in serial sections studied by electron microscopy. Three cell types can be defined in such chemosensory corpuscles. Basal cells are relatively undifferentiated in terms of cytologic characteristics and have been identified presumptively as the stem cells for differentiation of the other two cell types. Sustentacular or supporting cells are characterized by the presence of apical electron‐opaque granules that apparently are extruded into the lumen of the pore, and are, thus, the source of the electron‐opaque extracellular material present between the microvilli protruding from the apex of the cells into the chemosensory corpuscle pore. The chemosensory cells are characterized by the presence of synaptic specializations with appended nerve fibers at the base of the cell, the presence of specific cytoplasmic secretory granules, as well as numerous clusters of typical synaptic vesicles, and apical microvilli that extend into the pore of the corpuscle. Other cell profiles encountered in chemosensory corpuscles are cells in various stages of degeneration or transition, to one of the other cell types, from undifferentiated basal cells. Two types of synaptic specializations have been identified as being associated with chemosensory cells. The first is characterized by an increased electron‐opacity of the respective plasma membranes of nerve fiber and chemosensory cell. In this situation numerous synaptic vesicles usually are present in the cytoplasm of the chemosensory cell subjacent to the membrane densities. A second type of synaptic association is characterized by the presence of subsurface cisterns of agranular endoplasmic reticulum in the cytoplasm of the chemosensory cell, and numerous synaptic vesicles often are present in the axoplasm of the subjacent neurite, suggesting a reciprocal synapse. These findings are interpreted to indicate that only one cell type is specialized for transducing chemical signals into neural activity and that this cell is modulated by activity of the nervous system.
Microvasculature of the canine heart demonstrated by scanning electron microscopy
Authors: Anderson Bettina G. , Anderson Wesley D.
Published: February 2005

In previous studies, a marked diminution in left coronary flow during systole has been demonstrated. This phenomenon has been said to result from capillary compression by the contraction of myocardium and perhaps also from active changes in the state of the smooth muscle in the wall of the coronary vessels. In order to determine the morphological factors involved in this occurrence, and to gain a three‐dimensional concept of the myocardial microvasculature, casts were prepared by perfusion of the coronary arteries with methyl methacrylate. Because of the conditions of the perfusion, these casts were considered to demonstrate a state of muscular contraction. Following maceration, portions of the casts were prepared for scanning electron microscopy (SEM).

Arterioles of larger diameter were characterized by the helical configuration of the vascular replicas. Smaller vessels were categorized according to their directional pattern and their diameter. The arterioles gave rise to numerous large‐diameter capillaries and also to short vessels that were guarded by sphincters. True capillaries, in some cases guarded by precapillary sphincters, were packed in densely stacked parallel sheets with numerous short anastomotic connections between them. Postcapillary venules were found to enter at regular intervals into larger venules arranged perpendicular to the capillary sheets.

Most of these characteristics were found to be consistent throughout the microvasculature. These structural features were considered to be factors in the active regulation of blood flow through the myocardial microvasculature.
Immunocytochemical localization of nerve growth factor, epidermal growth factor, renin and protease A in the submandibular glands of Tfm/Y mice
Authors: Gresik E. W. , Chung K. W. , Barka T. , Schenkein I.
Published: February 2005

The submandibular glands of mice with testicular feminization (Tfm/Y) and their normal adult male littermates (Ta/Y) were studied by immunocytochemical techniques for the demonstration of epidermal growth factor (EGF), nerve growth factor (NGF), renin and protease A. In the glands of both the affected and normal males, these polypeptides were restricted to cells of the granular convoluted tubules (GCT), with the exception of protease A, which was also found in small amounts in striated duct cells. Compared to those of Ta/Y males, GCTs were narrower in the glands of Tfm/Y mice and contained a markedly reduced number of cells immunoreactive for EGF, NGF and renin. However, the number of GCT cells that stained for protease A in the glands of Tfm/Y males was not as drastically decreased.
Formation of gap and tight junctions between reaggregated blastomeres of the killifish, Fundulus
Authors: Ne'Eman Z. , Spira M. E. , Bennett M. V. L.
Published: February 2005

Blastomeres from eggs of the killifish, Fundulus, were mechanically dissociated and reaggregated by pelleting in a simple saline solution. Formation of gap and tight junctions was followed by electron microscopy of freeze‐ fracture replicas. Five to eight min after pelleting, neither new nor old junctions were observed. After 10–15 min, small gap junctions were found, but these were not associated with distinct formation plaques. Larger gap junctions were observed after 45 min, and the images were consistent with growth by accretion of intramembrane particles. In aggregates, after 20 min or more, tight junctions were much more commonly found than in intact blastulae, and it seemed likely that they were being formed by cells that were not doing so in the intact embryo. Initial stages consisted of short strands that appeared to grow in length. Also, more elaborate junctions were seen than occur in situ. Particle‐free membrane often occurred near incomplete junctions, and large junctions like those in situ separated particle‐rich from particle‐free membrane. In this system, the formation of both gap and tight junctions occurs with shorter latency, and is more precisely timed, than heretofore described.
Gap junctions between sensory and supporting cells of the utricular and saccular maculae in Anolis carolinensis examined by transmission electron microscopy
Authors: Zahm D. S.
Published: February 2005

Gap junctions, related to projections of sensory cells into supporting cells, occur from supranuclear to basal levels on hair cells, in both saccular and utricular maculae of the lizard, Anolis carolinensis. The larger numbers of junctional projections observed at some levels may indicate a zonular distribution within the neuroepithelia, but only on supracalyceal parts of hair cells in the utricular striola was a series of gap junctions found to be closely associated with the reticular lamina. The dimensions of the junctions, as characterized by the distance between opposite extremities of the arciform membrane appositions, averaged 0.14, 0.19, and 0.28 μm, respectively, on non‐calyceal utricular and saccular hair cells, and calyceal cells of the utricular striola. A notable number of the junctional profiles were adjacent or contiguous to open, coated, putatively endocytotic vesicles. These findings are discussed in respect to phylogenetic, developmental, and functional considerations.
A scanning electron microscopic study of the ferret atrioventricular node
Authors: Marino Thomas A.
Published: February 2005

The atrioventricular (AV) node and surrounding transitional zone in the ferret heart were examined with scanning electron microscopy. This permitted the direct visualization of the three‐dimensional cell shape, as well as intercellular relationships. Transitional cells were roughly cylindrical with extensively branching end processes. These cells were apposed to many adjacent transitional cells. The superficial AV nodal cells were smaller than transitional cells and were fusiform in shape. Most of the cell contacts between superficial AV nodal cells were between overlapping end processes, and there was very little branching of these cells. The deep AV nodal cells were similar to the superficial AV nodal cells, but were slightly larger and also had more cell contacts with adjacent cells. The possible significance of cell size and shape and intercellular relationships as they relate to atrioventricular impulse propagation and AV nodal delay are discussed.
Ultrastructural changes in type I and type II alveolar epithelial cells in isolated perfused dog lungs after production of moderate and severe hydrostatic edema
Authors: DeFouw David O.
Published: February 2005

Volume densities of type‐I and type‐II alveloar cell cytoplasmic organelles were estimated by established stereologic procedures. The measurements were obtained from isolated‐perfused dog lungs after the onset of acute hydrostatic edema. The isolated lungs provided three successive lobar preparations: control, moderately edematous, and severely edematous. The type‐II cell lamellar body volume densities were decreased in both stages of edema. Volume density of the granular endoplasmic reticulum (including polyribosome clusters) was increased after progression to severely edematous conditions. Concomitant increases in vesicular volume densities were recorded in type‐I cells after both moderate and severe edema. In addition, the relative percentages of vesicles directly attached to the luminal and abluminal plasma membranes were increased in the edematous lungs. These marked ultrastructural changes in the alveolar epithelium are consistent with the interpretation that both the release of lamellar bodies from type‐II cells and the number of type‐I cell pinocytotic vesicles are increased in isolated dog lungs after production of edema.
Acid‐proteinase activity of rat cartilage dependent on growth hormone
Authors: Owers Noel O.
Published: February 2005

Cartilage slices from normal rats, incubated at pH 4 for 3 to 7 hours, on a gelatin‐membrane substrate, digested the membrane, whereas cartilage from rats hypophysectomized for 21 days or more did not. Injection of 15 or 45 μg of bovine growth hormone into hypophysectomized rats restored the lytic activity of the cartilage. It is concluded that an acid proteinase is present in cartilage of normal rats, that is lost after hypophysectomy, and that the enzyme is restored by injection of growth hormone.
An immunocytochemist's view of gonadotropin storage in the adult male rat: Cytochemical and morphological heterogeneity in serially sectioned gonadotropes
Authors: Childs (Moriarity) Gwen V. , Ellison Dayle G. , Garner Laura L.
Published: February 2005

This study was designed to elucidate hormone storage patterns in gonadotropes with the use of ultrastructural immunocytochemistry on serial ultrathin sections. Sets of six serial sections were stained for beta chains of LH, FSH, or the C‐Terminal sequence of ACTH, and 430 cells cut in triple or double serial section were collected from a group of seven normal adult male rats. Approximately 50‐88% of the cells contained both LH and FSH, and most of these were Type I cells which are distinguished by their round shape and heterogeneous populations of secretion granules. Cells containing only FSH or LH constituted, on average, 19% of the population. These were a mixed group, morphologically, and included Type II cells distinguished by their angular shape and population of secretion granules, 250 nm in average diameter. Also among the FSH cells (and a few LH cells in two of the rats) were Type III cells, which resemble the corticotrope. On average, 10% of the serially sectioned cells contained only ACTH. Our findings show the presence of subpopulations of gonadotropes containing only one of the hormones, in numbers large enough to support the hypothesis that they may be partly responsible for the nonparallel release of gonadotropins. Also, the FSH‐LH cells seemed to vary in their staining intensity for the two hormones, suggesting that the gondaotropes are a fluid, heterogeneous population of cells capable of storing both or only one of the hormones.
Immunocytological study of the differentiation of chick and quail adenohypophysis epithelial rudiments, grafted or cultivated in vitro: Evidence for polypeptidic hormones
Authors: Ferrand Raymond , Fremont Patrick H. , Dubois Maurice P.
Published: February 2005

Epithelial rudiments of adenohypohysis were removed from chick and quail embryos between days 3 and 5 of development. Chick rudiments were grafted for 11–13 days onto the chorioallantoic membrane of decapitated chick embryo hosts. Quail rudiments were cultivated in vitro for 6 days. Both grafted and cultivated Rathke's pouches differentiated into adenohypophyseal tissue. The adenohypophyseal tissue cultured on chorio‐allantoic membrane exhibited cells reacting with the following immune sera: anti‐β‐(1–24)ACTH, anti‐α‐(17–39)‐ACTH, anti‐α‐endorphin, anti‐β‐endorphin and anti‐β‐LPH, which also gave a positive reaction when applied to adenohypophysis of corresponding age which had differentiated in situ. In situ, corticotrophs were located exclusively in the cephalic lobe of adenohypophysis. Therefore, the differentiation of corticotrophs in the whole graft, i.e., from both cephalic and caudal lobes of Rathke's pouch, showed that the cells of the caudal lobe, or at least some of them, were uncommitted when the rudiment was removed. In vitro, tissue derived from Rathke's pouch contained cells reacting with antibodies to β‐(1–24)‐ACTH, α‐(17–39)‐ACTH, and β‐LPH, as did adenohypophysis from quail embryos of corresponding age (9–10 days), differentiated in situ. The differentiation of quail Rathke's pouch in vitro corroborates that differentiation can occur without influence from hypothalamus and, moreover, shows that at least some kinds of cells can differentiate without influence exerted by any other encephalic factors, and in the absence of mesenchyme. The question arises whether fibroblastic cells derived from Rathke's pouch cells act as feeder‐cells and/or secrete some factors promoting differentiation.
Maintenance of gonadotrophs in pituitary autografts under the kidney capsules of female rats given sex hormones or LRH
Authors: Shiino Masataka , Fujihara Noboru , Rennels Edward G.
Published: February 2005

Female Sprague‐Dawley rats were hypophysectomized and the anterior pituitary gland was immediately placed under the kidney capsule. For 1 week after surgery, groups of pituitary autograft‐bearing animals were treated with twice‐daily injections of estradiol 17β (E), progesterone (P), estradiol 17β and progesterone (EP), or luteinizing hormone‐releasing hormone (LRH). Within 2–4 hours following the last injection, the pituitary grafts were removed and placed into organ culture. They were maintained in culture with or without added LRH (10−7 M) for 1 hour at 37°C. The culture media were then frozen for later radioimmunoassay of FSH and LH. The tissues were kept in culture for an additional 24 hours, at which time they were fixed and prepared for immunocytochemistry or electron microscopy.

Results showed that treatment of the animals with E, EP, or LRH enhanced the release of FSH and LH into the culture media, and that the release of these hormones was increaed further by acute incubation with LRH.

The ultrastructure of the gonadotrophs was well maintained by treating the animals with E or the combination of E and P or with LRH. Graft tissue from animals treated with LRH, which was incubated subsequently for 24 hours with LRH, showed the best maintenance of gonadotroph morphology. This experimental procedure should be useful for obtaining gonadotrophs for use in establishing gonadotroph cell lines.
Immunoreactive calcitonin in the rat anterior pituitary gland and its localization in thyrotrophs
Authors: Watkins Wayne B. , Moore Robert Y.
Published: February 2005

The distribution of those cells in the anterior pituitary gland of the rat which stain immunohistochemically with rabbit anti‐human calcitonin serum has been examined. Immunoreactive cells were confined primarily to the ventral surface of the gland and possessed both a distribution and morphology distinct from the corticotrophs. Staining of serial thin sections with rabbit anti‐rat TSH‐subunit serum resulted in an immunoreaction in those cells that stained for calcitonin. However, not all the thyrotrophs gave a positive immunoreaction for calcitonin. It is concluded from this study that it is inappropriate to attribute calcitonin as being part of the 31K‐dalton precursor for adrenocorticotropin, a hypothesis that was proposed earlier. In the immunohistochemical reaction with anti‐calcitonin serum, it was found that relatively high concentrations of antigen (500 μg/ml) were required in absorption experiments in order to inhibit staining. Furthermore, the staining of thyrotrophs with the anti‐calcitonin serum was inhibited after preadsorption of the primary antiserum with excess rat β‐TSH (1000 μg/ml). Because of these immunochemical characteristics, it is questionable whether the calcitonin‐like material observed in the rat pituitary gland is chemically identical to that of thyroidal calcitonin.
Functional classification of cell types in the growth hormone‐ and prolactin‐secreting rat MtTW15 mammosomatotropic tumor with ultrastructural immunocytochemistry
Authors: Baskin Denis G. , Erlandsen Stanley L. , Parsons Jonathan A.
Published: February 2005

The aim of this study was to identify the neoplastic endocrine cells which contain growth hormone (GH) and prolactin (PRL), in the MtTW15 mammosomatotropic tumor, with ultrastructural immunocytochemistry. We used tumors recovered after 5 to 11 weeks of tumor development, from normal (untreated) rats and from rats treated with the progestin medroxyprogesterone acetate (MPA)—a stimulator of GH secretion in these tumors. Immunocytochemical staining was done with the peroxidase‐antiperoxidase technique on ultrathin sections of tumor that had been fixed in glutaraldehyde and postfixed in osmium tetroxide. Immunospecific staining for PRL was found over small (150 nm) secretion granules, whereas staining for GH was deposited on the larger secretion granules (250 nm). Tumors from MPA‐treated rats contained profuse numbers of neoplastic cells with large, GH‐positive granules. Immunocytochemical staining for GH and PRL was also found in crinophagic, lysosome‐like inclusions, particularly in cells that contained many secretion granules. The results support the hypothesis that GH and PRL are produced by separate neoplastic endocrine cell types in the MtTW15 mammosomatotropic tumor, and demonstrate the value of ultrastructural immunocytochemical analysis for functional classification of cell types in chromophobic pituitary adenomas.
Electron‐microscopic cytochemical studies on the secretory process in rat prolactin cells in primary culture
Authors: Tougard C. , Picart R. , Tixier‐Vidal A.
Published: February 2005

Three aspects of the secretory process in male rat prolactin (PRL) cells grown in primary cultures for 7–14 days have been investigated by cytochemical methods. The subcellular localization of prolactin has been studied using preembedding or postembedding immunocytochemical methods after various fixatives. With postembedding method, PRL is localized essentially in secretory granules. The maximum intensity of staining is obtained with PAF fixative. With the preembedding method, subcellular localization of the staining varies depending on the fixative. After PAF‐fixation, positive staining is observed on secretory granules, ground cytoplasm, the outer face of some RER cisternae and, in a few cells, on the innermost Golgi cisternae, as well as on masses of condensing secretory material. After Ohtsuki's hypotonic fixative followed by saponin permeabilization, PRL is visualized within the totality of RER cisternae, including the perinuclear cisternae and the peripheral saccules on the cis‐Golgi face. Secretory granules are unstained. Membrane traffic was investigated using the Con A‐HRP indirect method as a tracer of surface saccharides. Plasma membrane, coated with Con A‐HRP at 4°C, is slowly internalized at 37°C. This involves both randomly distributed invaginations and capping. The final step of endocytosis (1–2 hours) is located in the Golgi zone, where very few smooth membranes are stained. In contrast, a conspicuous deposit is found around the dense content of secretory granules. This suggests a recycling of internalized membrane and a transfer of Con A‐HRP from the inner face of smooth cisternae to the secretory material. The internalization of Con A‐HRP‐coated membrane leads to an inhibition of PRL release starting after 30 minutes. This is accompanied by a marked increase of acid phosphatase activity, mostly around forming and mature secretory granules.
Immunocytochemical demonstration of anterior pituitary hormones in the pars tuberalis of long‐term hypophysectomized rats
Authors: Ordronneau Paul , Petrusz Peter
Published: February 2005

The hormone‐containing cells of the pars tuberalis of the rat adenohypophysis were studied, 4–5 months after hypophysectomy, with a double bridge immunocytochemical technique and with antisera directed against the hormones of the pars distalis. Corticotropes, lactotropes, somatotropes, thyrotropes, and gonadotropes were found in the pars tuberalis of all animals. These cells are well situated to receive blood, nerve terminals, and tanycyte processes from the median eminence and, thus, to be influenced by the chemical messengers from the hypothalamus. It is concluded that the pars tuberalis has to be regarded as a potential source of adenohypophyseal hormones in an animal model traditionally considered to be free of such hormones.
Role of somatostatin in the modulation of hypophysial growth hormone production by gonadal steroids
Authors: Gross Douglas S.
Published: February 2005

Growth hormone‐release‐inhibiting hormone (somatostatin) has been localized in several central nervous system sites, but the contribution of somatostatin in these various loci to the control of growth hormone (GH) production is unclear. In the present study, the efficacy of castration, alone, or with subsequent gonadal steroid administration, in modulating hypophysial GH production was examined, and the response of somatostatin‐containing nerve endings in the median eminence and the organum vasculosum of the lamina terminalis (OVLT) was evaluated by means of immunocytochemistry. Orchidectomy reduced the size and number of immunoreactive GH‐cells, and testosterone administration prevented this change. Ovariectomy appeared to stimulate the somatotropes, but this effect was neither as dramatic nor as consistent as the effect of castration in the male. Administration of estradiol, however, resulted in a marked reduction in the number, size, and GH content of somatotropes in all animals examined. Somatostatin was localized in the external lamina of the median eminence and in nerve endings surrounding the core of capillaries in the OVLT. Only the median eminence responded to steroid manipulations with a visible change in the immunoreactive pool of somatostatin, with a decrease following orchidectomy, which was reversible by testosterone treatment, and an increase following ovariectomy, which was reversible by estradiol treatment. However, as in the GH responses to steroid manipulations, the somatostatin responses were more variable in females than in males.

These results suggest that: (1) testosterone promotes and estradiol, at least at high doses, inhibits storage of GH in the anterior pituitary; (2) these changes in GH production may be regulated, in part, by altered somatostatin release from the median eminence into the hypophysial portal blood; and (3) somatostatin in the OVLT may not be involved in the steroid‐induced modulation of GH production.