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Morphogenesis of avian conjunctival papillae follows a predictable temporal and spatial pattern and is in some manner directly related to the introduction of the underlying scleral ossicles. We have been able, using Scanning Electron Microscopy (SEM), to correlate all of Murray's ('43) histological stages (1--6) of papillae development, with changes in elevation and morphology of the surface of the conjunctiva. The first indication of morphogenesis is the formation of "papillae primordia." The centers of these primordia exhibit decreased intercellular contact, and become elevated as radially symmetrical humps whose surfaces are composed of rounded cells with numerous microvillar projections. As the papillae become asymmetrical and elongate, cells near the tip of the papillae enlarge and develop microridges. During regression of the papillae, single clusters of cells appear to become lost from the surfaces of the papillae into the surrounding fluid. In contrast to normal chick embryos, those homozygous for papillae and underlying scleral ossicles (Palmoski and Goetinck, '70). SEM of the mutant conjunctival surface indicates that these papillae do not exhibit all of Murray's ('43) histological stages and are morphologically abnormal. Data from the present SEM study of the normal and scaleless conjunctiva are discussed in relation to those data of other investigators, and we suggest that Stage 4 in papillae development is critical to scleral ossicle formation.
Anat Rec 1981 Feb
PMID:Morphogenesis of conjunctival papillae from normal and scaleless chick embryos. 721 23

The density and distribution of membrane associated particles of piglet oxyntic cell tubulovesicular and apical surface membranes were investigated during resting (nonsecreting) and secreting conditions. For the resting oxyntic cell, the abundant tubulovesicles showed a highly asymmetrical distribution of particles between fracture faces, with the P face heavily studded by particles and the E face particle deficient. The apical surface, however, had a relatively symmetrical distribution of particles on both membrane fracture faces. In contrast to the resting state, the apical surface of the stimulated oxyntic cell showed a marked asymmetry of membrane particles; the P face had a high density of particles, while there was a scarcity of particles on the E face. The observed changes in apical surface membrane particle distribution support the hypothesis that, following the initiation of acid secretion, the tubulovesicles fuse with and become an integral part of the apical surface. Thus, the apical membrane P face of the stimulated cell is enriched and the E face is diluted by the incorporation of tubulovesicular membranes.
Anat Rec 1980 Feb
PMID:Structure of oxyntic cell membranes during conditions of rest and secretion of HCl as revealed by freeze-fracture. 741 10

The fine structure of the periaqueductal gray (PAG) of the rabbit was examined using the transmission electron microscope. On the basis of synaptic polarity, vesicle size, and the nature of the pre- and post-synaptic elements, 10 essentially different synaptic types could be discerned (6 axo-dendritic, 2 axo-somatic, 1 axo-axonic, and 1 dendro-dendritic). Synaptic contacts on the soma of PAG neurons were small and covered, on average, only 1.6% of the soma surface. The most striking feature of the synaptic structure of the PAG was that more than 94.1% of all synapses were axo-dendritic. Of these, 83.5% were of the symmetrical type. Most of these contacts occurred on buttons of small to medium size, and contained either round vesicles of medium size or pleomorphic vesicles of medium size. Boutons containing only flattened vesicles were quite rare. Boutons contacting larger dendrites were generally small-to-medium in size, made asymmetric-type synaptic contacts, and contained pleomorphic vesicles of medium-to-large size. Medium-sized dendrites were contacted principally by small boutons exhibiting either symmetrical or asymmetrical junctions containing medium-sized pleomorphic vesicles, and in addition a few of these boutons contained both large, and small, round vesicles. Dendritic spines were generally provided with only one synaptic contact, stretching the entire width of the spinous process. Boutons and the spines on dendrites were approximately the same size. Synapses between two vesicle-containing structures (axo-axonic or dendro-dendritic synapses) were rare (1.4%). They were generally asymmetric and contained round vesicles of medium size. Complex synapses, where a glial sheet enclosed the synapse, were occasionally observed. Also seen were multiple synapses, with up to 11 contacts on a single dendritic profile. Large dense-core vesicle were seen in approximately 40% of all synapses, whereas small dense-core vesicles were only found in about 3%. Data is provided on how different synaptic features relate to ventral, lateral, dorsal, and medial PAG. Principally this is in relation to neuron size, glia cell content, axonal characterization, and vesicular type.
Anat Rec 1993 Jul
PMID:Quantitative ultrastructural analysis of the periaqueductal gray in the rabbit. 836 62

Neurons of the periaqueductal gray (PAG) have an extensive dendritic tree which plays an important role in the neuronal circuits supporting the functional activities of this region. The complexity of the local circuits is increased by the occurrence of dendritic spines. We have compared the dendritic and spine organization in the cat with that of man in order to verify whether an inverse relationship exists between dendritic tree extension and spine density and complexity. Sections of cat and human PAG prepared according to the Golgi-Cox method were studied with the conventional light microscope (LM) and the confocal laser scanning microscope (CLSM). The cat PAG was also studied at the electron microscopic level. The light microscopic study provided the morphoquantitative characteristics of the dendritic arborization and spines of the multipolar and fusiform neurons of the human and cat PAG. The CLSM methodology, thanks to the three-dimensional reconstruction of the neurons and the rotation of the reconstructed images, brought into view dendritic branches and spines that could not have been observed at the LM, thereby showing a wider dendritic tree and more numerous spines. The data combined from LM and CLSM demonstrate that in both species most spiny neurons are multipolar and probably projection neurons. In man, the multipolar neurons show a more extensive dendritic tree due to a wider secondary ramification, which would seem to be balanced by more numerous spines in cat. At the electron microscopic level, axo-dendritic synapses are numerous and show symmetrical and asymmetrical junctions in equal proportions; furthermore, the great majority of the spines are in contact with synaptic boutons which contain round vesicles and make predominantly asymmetrical contacts features which indicate excitatory activity. The combined use of different techniques gave a complete picture of the dendritic tree and spines of the neurons of human and cat PAG and showed a wider dendritic surface available for the receipt of the synaptic contacts than had been reported previously. Furthermore, our findings demonstrate that the PAG dendritic spines are important and specific structures in the synaptic complex of the neuropil, suggesting that they might create a local device to modulate and integrate the afferent inputs, probably in an excitatory way. The differences observed in the two species suggest that afferent information might be handled in different ways in human and cat PAG.
Anat Rec 1998 07
PMID:Dendritic arborization and spines of the neurons of the cat and human periaqueductal gray: a light, confocal laser scanning, and electron microscope study. 966 58

The gross, light, and electron microscopic anatomies of the porcine intrinsic cardiac nervous system were investigated in 26 pigs to facilitate functional studies in this model. Gross anatomy: Numerous ganglia and interconnecting nerves (ganglionated plexuses) were found to be concentrated in epicardial fat in five atrial and six ventricular regions. The five atrial ganglionated plexuses identified were (1) the ventral right atrial, (2) the right vena cava-right atrial, (3) the dorsal atrial, (4) the interatrial septal, and (5) the left superior vena cava-left atrial ones. Six ventricular ganglionated plexuses were identified in close proximity to the (1) roots of the aorta and pulmonary artery (craniomedial), extending along the left main coronary artery to the (2) ventral interventricular and (3) circumflex coronary arteries. (4) A ganglionated plexus was identified around the origin of the dorsal interventricular coronary artery, as well as the (5) right main and (6) right marginal coronary arteries. Isolated neurons were identified scattered throughout the cranial interventricular septum. Microscopic anatomy: Approximately 3,000 neuronal somata were estimated to compose this intrinsic cardiac nervous system. Some ganglia contained more than 100 neurons. Neuronal somata had dimensions of roughly 33.1 (short axis) by 46.3 (long axis) microm. Most were multipolar, a small population of unipolar neurons being identified in atrial and ventricular tissues. At the electron microscopic level, asymmetrical axodendritic synapses with small clear, round vesicles were identified, some containing large dense-cored vesicles. In summary, porcine intrinsic cardiac neurons are concentrated in 11 distinct atrial and ventricular ganglionated plexuses. These extensive plexuses, along with fewer scattered neurons, display varied neuronal morphology and synaptology that represent the anatomical substrate for complex information processing within the intrinsic cardiac component of the porcine cardiac neuronal hierarchy. These anatomical data provide a framework for physiological analyses of the porcine intrinsic cardiac nervous system.
Anat Rec A Discov Mol Cell Evol Biol 2003 Mar
PMID:Porcine intrinsic cardiac ganglia. 1255 41

The body of a Japanese flounder (Paralichthys olivaceus) changes from a symmetrical to an asymmetrical form during metamorphosis. To obtain detailed information on the mechanisms of the migration of the right eye to the left side, soft and hard tissues in the head of larval flounders were examined using transmission electron microscopy (TEM). Retrorbital vesicles (Rvs) are pairs of sac-like structures under the eyes. It has been suggested that the asymmetrical development of Rvs, with the right (blind) one being bigger than the left, is the driving force behind eye migration. The present study revealed that the ultrastructure of the Rv sheath is quite similar to that of a lymphatic capillary. Thus, it is possible that the Rv is a part of the lymph system, and is probably related to the secondary vascular system in teleosts. If we assume that the Rv sheath has a high permeability to liquid, similar to lymphatic capillaries, it is not plausible that the active expansion of the Rv pushes the eyeball. On the other hand, the pseudomesial bar (Pb) is a bone that is unique to flounders and is present only on the right (blind) side. At the beginning of eye migration, an aggregation of fibroblast-like cells is observed in the dermis under the right eye, where the Pb will subsequently be formed. These cells have a well-developed rough endoplasmic reticulum (rER) and mitochondria, and are probably responsible for formation of the thick layers of collagen fibrils around them. Since it is unlikely that the active expansion of the Rv causes eye migration, the role played by the Pb and its rudiment becomes more significant in right eye migration in the Japanese flounder becomes more significant.
Anat Rec A Discov Mol Cell Evol Biol 2003 Jul
PMID:Fine structure of soft and hard tissues involved in eye migration in metamorphosing Japanese flounder (Paralichthys olivaceus). 1280 50

The present ultrastructural investigation into osteocyte dendrogenesis represents a continuation of a previous study (Ferretti et al., Anat. Embryol., 2002; 206:21-29), in which we pointed out that, during intramembranous ossification, the well-known dynamic bone formation (DBF), performed by migrating osteoblast laminae, is preceded by static bone formation (SBF), in which cords of stationary osteoblasts transform into osteocytes in the same site where they differentiated. The research was carried out on the perichondral center of ossification surrounding the mid shaft level of various long bones of chick embryos and newborn rabbits. Transmission electron microscope observations showed that the formation of osteocyte dendrites is quite different in the two types of osteogenesis, mainly depending on whether or not osteoblast movement occurs. In DBF, osteoblasts transform into small ovoidal/ellipsoidal osteocytes and their dendrites form in an asynchronous and asymmetrical manner in concomitance with, and depending on, the advancing mineralizing surface and the receding osteogenic laminae. In SBF, stationary osteoblasts give rise to big globous osteocytes, located inside confluent lacunae, with short and symmetrical dendrites that can radiate simultaneously all around their cell body because they are completely surrounded by unmineralized matrix. Contacts and gap junctions were observed between all osteocytes (both SBF- and DBF-derived) and between osteocytes and osteoblasts. Finally, a continuous osteocyte network extends throughout the bone, regardless of its static or dynamic origin. This network has the characteristic of a functional syncytium, potentially capable of modulating, by wiring transmission, the cells of the osteogenic lineage covering the bone surfaces.
Anat Rec A Discov Mol Cell Evol Biol 2004 May
PMID:Osteocyte dendrogenesis in static and dynamic bone formation: an ultrastructural study. 1510 43

Vibrissal follicle-sinus complexes (F-SCs) are sensory receptors of the mammalian integument system. They are best developed within Pinnipedia. The objective of this study was to investigate the F-SCs of bearded seals (Erignathus barbatus) for benthic foraging adaptations. Bearded seals possessed approximately 244 mystacial F-SCs. In this species, F-SCs consisted of an outer dermal capsule (DC) surrounding a blood sinus system [upper cavernous sinus (UCS), ring sinus (RS), and lower cavernous sinus (LCS)] and concentric rings of epidermal tissue. The UCS comprised up to 62% of the F-SC length and may function as thermal protection for mechanoreceptors. A large asymmetrical ringwulst was located in the RS. A deep vibrissal nerve penetrated the DC at its base and terminated on mechanoreceptors in the epidermal tissues of the LCS and RS. The mean number of myelinated axons per F-SC was 1,314 (range, 811-1,650) and was among the highest number of axons per F-SC reported to date. An estimated mean number of 320,616 myelinated axons innervate the entire mystacial vibrissal array. Merkel-Neurite complexes (MNCs) and small simple laminated corpuscles were found in the region of the LCS. Myelinated axons also terminated on MNCs and lanceolate endings apical to the ringwulst. The number of F-SCs, their geometry in the mystacial region, the number of myelinated axons per F-SC, and the distribution of mechanoreceptors support the premise that pinniped vibrissae are sensitive active-touch receptor systems, and that structural differences in bearded seals, relative to other phocids, may be adaptations for benthic foraging.
Anat Rec A Discov Mol Cell Evol Biol 2006 Jan
PMID:Microstructure and innervation of the mystacial vibrissal follicle-sinus complex in bearded seals, Erignathus barbatus (Pinnipedia: Phocidae). 1634 12

This retrospective study evaluated the magnetic resonance (mr) images of traumatic disc extrusions in 11 dogs. The findings included a reduction in the volume and signal intensity of the nucleus pulposus, focal hyperintensity within the overlying spinal cord on T (2)-weighted mr images, and subtle spinal cord compression, extraneous material or signal change within the vertebral canal. The largest area of hyperintensity in the spinal cord was directly over or close to the affected disc space, appeared asymmetrical and in the majority of cases was less than one vertebra in length. Parenchymal spinal cord haemorrhage was identified in four of the dogs. Vacuum phenomena, evident as a signal void in the centre of the disc, were identified in two of the dogs. The mr images were distinct from those reported for other causes of spinal cord dysfunction.
Vet Rec 2007 Jun 09
PMID:Magnetic resonance imaging of traumatic intervertebral disc extrusion in dogs. 1755 27

Current hypotheses regarding vertebrate left-right asymmetry patterns are based on the presumption that genetic regulatory networks specify sidedness via extracellular morphogens and/or ciliary activity. We show empirical time-lapse evidence for an asymmetric rotation of epiblastic nodal tissue in avian embryos. This rotation spans the interval when initial symmetric expression of Shh and Fgf8 becomes asymmetrical with respect to the midline.
Anat Rec (Hoboken) 2009 Apr
PMID:Rotation of organizer tissue contributes to left-right asymmetry. 1930 Dec 78


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