PRISM :: Browsing by Author "Cavey, Michael J."

Browsing by Author "Cavey, Michael J."

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Open Access
A Morphological study of hepatic hemopoiesis in chicken embryos
(1991) Wong, Gene K.; Cavey, Michael J.
Hemopoiesis in the liver of the chicken embryo begins on day 7 of incubation (Hamburger and Hamilton Stage 30) and peaks on day 14 (Stage 40). During this time frame, the differentiation of hepatic and hemopoietic cells was studied by light microscopy and by transmission and scanning electron microscopy. Morphometric analyses were performed on the light and electron micrographs. The avian liver is a closely packed array of dendriform cords and discontinuous sinusoids. Hepatocytes are pyramidal in shape, and they ring the bile canaliculi which run through the centers of the hepatic cords. Semithin sections, made possible by infiltration and embedding in glycol methacrylate, were stained with hematoxylin and eosin to reveal the general architecture of the liver, as well as the lipid content of the hepatocytes, and by the periodic acid-Schiff reaction and hematoxylin to visualize the cytoplasmic stores of glycogen. Differentiating hepatocytes were scored for the presence or absence of glycogen and lipid. Glycogen-containing cells fluctuate during early hemopoiesis, but the cell proportion progressively increases toward the hemopoietic peak. Most hepatocytes lack lipid droplets until Stages 39 and 40. From Stage 30 to Stage 35, hepatocyte volume falls to its lowest value. Subsequently (Stages 36 to 40), cell volume increases and hepatocytes achieve a relatively constant size. Ultrastructural changes in the differentiating hepatocytes, including alterations to the mitochondria, endoplasmic reticulum, and Golgi apparatus, were documented. This cell survey was extended to the sinusoidal linings (endothelial cells and Kupffer cells) and to the perisinusoidal cells between the cords and sinusoids. Glycol methacrylate sections were used in lieu of blood smears to study hemopoietic cells, thus overcoming such undesirable traits as cell shrinkage and/or rupture. Sections proved superior to smears for detailed examinations of nuclear and cytoplasmic morphologies and for precise localization of hemopoietic cells to intravascular and extravascular sites. The avian liver, it was found, is directly involved only in erythropoiesis and granulopoiesis. Erythropoietic cells were observed throughout the hemopoietic time frame, but blood islands with granulopoietic cells did not appear until Stage 35. Endothelial cells of the sinusoidal linings are important to erythropoiesis. Asymmetric cell division can release one daughter cell, a proerythroblast, into the circulation, while retaining the other daughter cell in the sinusoidal lining as an endothelial cell. Involvement of endothelial cells in no way discounts a contribution by erythropoietic stem cells. Granulopoiesis in the liver produces only eosinophilic leukocytes. Individual granulopoietic cells appear first in the connective tissue sheaths of hepatic blood vessels, and these cells later congregate into large blood islands. From a comparative standpoint, the elements deemed critical to hemopoiesis in the mammalian liver - the hepatic vasculature, the prehepatocyte population, and the compartments for stem cell differentiation - may not hold the same relevance in the bird. Owing to an inordinate reliance on intravascular hemopoiesis, the relative importance of a prehepatocyte population and individual stem cell compartments is diminished.
Open Access
Computer-assisted Reconstruction of Vertebrate Embryos from Serial Histological Sections
(Blackwell Publishing, 1993-04) Cavey, Michael J.; Stock, David A.; Wong, Gene K.; Biological Sciences; Faculty of Science; University of Calgary
Open Access
Custom Silicone Rubber Molds for Epoxy Resin Embedding
(Blackwell Publishing, 1993) Cavey, Michael J.; Wong, Gene K.; Biological Sciences; Faculty of Science; University of Calgary
Open Access
Development of the liver in the chicken embryo. I. Hepatic cords and sinusoids
(John Wiley & Sons, Inc., 1992) Cavey, Michael J.; Wong, Gene K.; Biological Sciences; Faculty of Science; University of Calgary
Hemopoiesis in the liver of the chicken embryo begins on day 7 of incubation (Hamburger and Hamilton Stage 30) and peaks on day 14 (Stage 40). During this time frame, the differentiation of hepatic cells was examined by light microscopy, transmission and scanning electron microscopy, and morphometry. The avian liver is a closely packed mass of dendriform cords and discontinuous sinusoids. Hepatocytes are pyramidal in shape, and they ring the bile canaliculi which run through the centers of the cords. Semithin sections, made possible by infiltration and embedding in glycol methacrylate, were stained with hematoxylin and eosin to assess the general architecture of the organ and the lipid content of the hepatocytes and by the periodic acid-Schiff reaction and hematoxylin to visualize the cytoplasmic stores of glycogen. The number of hepatocytes with demonstrable glycogen fluctuates erratically in early hemopoiesis, and the proportion of glycogen-containing cells progressively increases as hemopoiesis climbs to a peak. Most differentiating hepatocytes are devoid of lipid droplets until Stages 39 and 40. From Stage 30 to 35, hepatocyte volume falls to its lowest value. Subsequently (Stages 36 to 40), cell volume increases and hepatocytes achieve a relatively uniform size. Ultrastructural changes in the differentiating hepatocytes, including alterations to the mitochondria, endoplasmic reticulum, and Golgi apparatus, are documented. These morphological and morphometric findings on the prehepatocyte population and hepatic vasculature cover 2 of the 3 elements deemed critical to hepatic hemopoiesis in many vertebrates. o 1992 Wiley-Liss, Inc.
Open Access
Development of the liver in the chicken embryo. II. Erythropoietic and granulopoietic cells
(John Wiley & Sons, Inc., 1993) Cavey, Michael J.; G. K., Wong,; Biological Sciences; Faculty of Science; University of Calgary
Hepatic hemopoiesis is apparent in the chicken embryo on day 7 of incubation (Hamburger and Hamilton Stage 301, and a peak in hemopoietic activity occurs on day 14 (Stage 40). During this period, the differentiation of hemopoietic cells was examined by light microscopy and by transmission and scanning electron microscopy. Glycol methacrylate sections were used in lieu of smears to study hemopoietic cells, thus minimizing the problems of cell shrinkage and rupture. The sections were superior to smears for close examination of nuclear and cytoplasmic morphologies and for precise localization of hemopoietic cells to intravascular and extravascular sites. The avian liver is involved directly with erythropoiesis and granulopoiesis only. Erythropoietic cells, occurring in intravascular and extravascular locations, appear throughout the time frame examined. Blood islands with granulopoietic cells were not observed until days 8-9 (Stage 35). Granulopoiesis in the liver produces only eosinophilic leukocytes. Individual granulopoietic cells appear first in the connective tissue sheaths of hepatic vessels, and these cells subsequently congregate into blood islands. Endothelial cells of the sinusoidal linings, through asymmetric divisions, frequently release daughter cells into the circulation, and Kupffer cells are actively engaged in phagocytosis of erythrocytes. From a comparative standpoint, the elements deemed critical to hemopoiesis in the mammalian liver-prehepatocyte population, hepatic vasculature, and compartments for stem cell differentiation-may not hold the same importance in the bird, owing to an inordinate reliance on intravascular hemopoiesis in this vertebrate class. Key words: Capillaries, Chick embryo, Vascular endothelium, Hematopoiesis, Kupffer cells, Liver, Microscopy, Morphogenesis o 1993 Wiley-Liss, Inc.
Open Access
Development of the Subdigital Adhesive Pads of Ptyodactyhs guttatus (Reptilia: Gekkonidae)
(John Wiley & Sons, Inc., 1992) Cavey, Michael J.; Rosenberg, Herbert I.; Russel, Anthony P.; Biological Sciences; Faculty of Science; University of Calgary
Subdigital adhesive pads play an important role in the locomotion of many species of gekkonid lizards. These pads consist of integrated components derived from the epidermis, dermis, vascular system, subcuticular tendons, and phalanges. These components become intimately associated with each other during the developmental differentiation of the digits and the sequence of this integration is outlined herein in Ptyodactylus guttatus. The pads initially appear as paired swellings at the distal tips of the digits. Subsequently, a fan-like array of naked scansors develops on the ventral surface of each digit, at about the same time that scales differentiate over the surface of the foot as a whole. At the time of appearance of the naked scansors, the vascular sinus system of the pad also differentiates, along with subcuticular connective tissue specializations. At this stage the digits, along with the rest of the body, are clad in an embryonic periderm. Only after hatching and as the periderm is shed, do the epidermal setae and spines appear. The developmental sequence described here is consistent with predictions previously advanced about the evolutionary origin and elaboration of subdigital pads in gekkonid lizards. The paucity of available staged embryonic material leaves many questions unresolved.
Open Access
Developmental changes in the inner epidermis of the bean seed coat
(Springer-Verlag, 1990) Cavey, Michael J.; Yeung, E.C.; Biological Sciences; Faculty of Science; University of Calgary
The inner epidermis of the bean seed coat shows remarkable structural changes during seed development. At the globular stage of development, a moderately electron-dense substance begins to accumulate in the outer tangential and radial walls of the cells. The staining and fluorescence characteristics, together with the localization ofperoxidase in the wall, suggest that this electron-dense material is a phenolic substance. At the same stage of embryo development, structural specialization can be detected in the cytoplasm of the epidermal cells with an increase in the abundance of organelles, especially the endoplasmic reticulum, mitochondria, and dictyosomes. These structural features are similar to those in the underlying branched parenchyma cells. As the seed rapidly expands during the maturation stage of embryo development, the epidermal cells and the inner layers of the branched parenchyma cells begin to degenerate. Small ruptures can be detected in the epidermis, exposing the branched parenchyma cells. These structural changes are discussed in relation to their possible functions during embryo development.
Open Access
The effects of Heat Shock on th Morphology and Protein Synthesis of the Epidermis of Xenopus laevis Larvae
(Rockefeller University Press, 1988-03) Cavey, Michael J.; Nickells, Robert W.; Browder, Leon W.; Biological Sciences; Faculty of Science; University of Calgary
By scanning electron microscopy, we have observed that a 20-min heat shock at 37 degrees C, although not lethal, causes extensive damage to the epidermis of 30-h and 2-d (post-fertilization) Xenopus laevis larvae. The primary effects of heat shock are the apical swelling of the epidermal cells, giving the epidermis a "cobblestone" appearance, and the selective shedding of the ciliated cells. The shed cells may be cell fragments, however, because some of them are anucleate. Shed cells also exhibit the enriched synthesis of a group of heat shock proteins of 62,000 D molecular weight, suggesting that these proteins are specific to the shed cells. Prolonged heat shock of these larvae (i.e., 30 min at 37 degrees C) results in the complete disintegration of the epidermis, followed by larval death. At later stages of development (3- d and 4-d post-fertilization), the epidermis becomes more resistant to heat-induced damage inflicted by a 20-min heat shock. This increase in resistance coincides with the development of large secretory cells and the loss of ciliated cells in the epidermis and thus parallels a change in the state of histological differentiation.
Open Access
Evolutionary derivation of the American lobster cardiovascular system: an hypothesis based on morphological and physiological evidence
(Blackwell Publishing, Inc., 1997) Cavey, Michael J.; Wilkens, J. L.; Yazawa, T.; Biological Sciences; Faculty of Science; University of Calgary
The cardiovascular system of the American lobster includes a large muscular heart that pumps blood into seven arteries, each of which ramifies extensively. Portions of the system may be viewed as relatively primitive, while others are highly derived. We have confirmed earlier findings that the sternal artery is not a single vessel, but a paired structure. The sternal artery and its partner closely resemble the medial branches of the segmental lateral vessels from the dorsal abdominal artery in anterior segments of the abdomen, and they may be homologous. We report that the walls of the dorsal abdominal artery contain blocks of striated muscle cells and that the artery can be induced to contract in response to electrical stimulation or perfusion with proctolin. These observations provide the basis for an attempt to trace the evolution of the heart and arteries from that of primitive malacostracans to its state of development in lobsters.
Open Access
Fine Structure and Differentiation of Ascidian Muscle I. DIFFERENTIATED CAUDAL MUSCULATURE OF DlSTAPLlA OCClDENTALlS TADPOLES
(John Wiley & Sons, Inc., 1972) Cavey, Michael J.; Cloney, Richard A.; Biological Sciences; Faculty of Science; University of Calgary
The structure of the caudal muscle in the tadpole larva of the compound ascidian Distaplia occidentalis has been investigated with light and electron microscopy. The two muscle bands are composed of about 1500 flattened cells arranged in longitudinal rows between the epidermis and the notochord. The muscle cells are mononucleate and contain numerous mitochondria, a small Golgi apparatus, lysosomes, proteid-yolk inclusions, and large amounts of glycogen. The myofibrils and sarcoplasmic reticulum are confined to the peripheral sarcoplasm. Myofibrils are discrete along most of their length but branch qear the tapered ends of the muscle cell, producing a Felderstmktur. The myofibrils originate and terminate at specialized intercellular junctional complexes. These myomuscular junctions are normal to the primary axes of the myofibrils and resemble the intercalated disks of vertebrate cardiac muscle. The myofibrils insert at the myomuscular junction near the level of a Z-line. Thin filaments (presumably actin) extend from the terminal Z-line and make contact with the sarcolemma. These thin filaments frequently appear to be continuous with filaments in the extracellular junctional space, but other evidence suggests that the extracellular filaments are not myofilaments. A T-system is absent, but numerous peripheral couplings between the sarcolemma and cisternae of the sarcoplasmic reticulum (SR) are present on all cell surfaces. Cisternae coupled to the sarcolemma are continuous with transverse components of SR which encircle the myofibrils at each I-band and H-band. The transverse component over the I-band consists of anastomosing tubules applied as a single layer to the surface of the myofibril. The transverse component over the H-band is also composed of anastomosing tubules, but the myofibrils are invested by a double or triple layer. Two or three tubules of sarcoplasmic reticulum interconnect consecutive transverse components. Each muscle band is surrounded by a thin external lamina. The external lamina does not parallel the irregular cell contours nor does it penetrate the extracellular space between cells. In contracted muscle, the sarcolemmata at the epidermal and notochordal boundaries indent to the level of each Z-line, and peripheral couplings are located at the base of the indentations. The external lamina and basal lamina of the epidermis are displaced toward the indentations. The location, function, and neuromuscular junctions of larval ascidian caudal muscle are similar to vertebrate somatic striated muscle. Other attributes, including the mononucleate condition, transverse myomuscular junctions, prolific gap junctions, active Golgi apparatus, and incomplete nervous innervation are characteristic of vertebrate cardiac muscle cells.
Open Access
Fine Structure and Differentiation of Ascidian Muscle II. MORPHOMETRICS AND DIFFERENTIATION OF THE CAUDAL MUSCLE CELLS OF DlSTAPLlA OCClDENTALlS TADPOLES
(John Wiley & Sons, Inc., 1974) Cavey, Michael J.; Cloney, Richard A.; Biological Sciences; Faculty of Science; University of Calgary
The locomotor function of the caudal muscle cells of ascidian larvae is identical with that of lower vertebrate somatic striated (skeletal) muscle fibers, but other features, including the presence of transverse myomuscular junctions, an active Golgi apparatus, a single nucleus, and partial innervation, are characteristic of vertebrate myocardial cells. Seven stages in the development of the compound ascidian Distaplia occidentalis were selected for an ultrastructural study of caudal myogenesis. A timetable of development and differentiation was obtained from cultures of isolated embryos in vitro. The myoblasts of the neurulating embryo are yolky, undifferentiated cells. They are arranged in two bands between the epidermis and the notochord in the caudal rudiment and are actively engaged in mitosis. Myoblasts of the caudate embryo continue to divide and rearrange themselves into longitudinal rows so that each cell simultaneously adjoins the epidermis and the notochord. The formation of secretory granules by the Golgi apparatus coincides with the onset of proteid-yolk degradation and the accumulation of glycogen in the ground cytoplasm. Randomly oriented networks of thick and thin myofilaments appear in the peripheral sarcoplasm of the muscle cells of the comma embryo. Bridges interconnect the thick and thin myofilaments (actomyosin bridges) and the thick myofilaments (H-bridges), but no banding patterns are evident. The sarcoplasmic reticulum (SR), derived from evaginations of the nuclear envelope, forms intimate associations (peripheral couplings) with the sarcolemma. Precursory Z-lines are interposed between the networks of myofilaments in the uesicutate embryo, and the nascent myofibrils become predominantly oriented parallel to the long axis of the muscle cell. Muscle cells of the papittate embryo contain a single row of cortical myofibrils. Myofibrils, already spanning the length of the cell, grow only in diameter by the apposition of myofilaments. The formation of transverse myomuscular junctions begins at this stage, but the differentiating junctions are frequently oriented obliquely rather than orthogonally to the primary axes of the myofibrils. With the appearance of H-bands and M-lines, a single perforated sheet of sarcoplasmic reticulum is found centered on the Z-line and embracing the I-band. The sheet of SR establishes peripheral couplings with the sarcolemma. In the prehatching tadpole, a second collar of SR, centered on the M-line and extending laterally to the boundaries with the A-bands, is formed. A single perforated sheet surrounds the myofibril but is discontinuous at the side of the myofibril most distant from the sarcolemma. To produce the intricate architecture of the fully differentiated collar in the swimming tadpole (J. Morph., 138: 349, 1972), the free ends of the sheet must elevate from the surface of the myofibril, recurve, and extend peripherally toward the sarcolemma to establish peripheral couplings. Morphological changes in the nucleus, nucleolus, mitochondria, and Golgi bodies are described, as well as changes in the ground cytoplasmic content of yolk, glycogen, and ribosomes. The volume of the differentiating cells, calculated from the mean cellular dimensions, and analyses of cellular shape are presented, along with schematic diagrams of cells in each stage of caudal myogenesis. In an attempt to quantify the differences observed ultrastructurally, calculations of the cytoplasmic volume occupied by the mqjor classes of organelles are included. Comparison is made with published accounts on differentiating vertebrate somatic striated and cardiac muscles.
Open Access
Heteromorphic Discocilia of the Phanerozonian Starfish Luida foliolata: Artifacts of Chemical Fixation
(Blackwell Publishing, 1987-01) Cavey, Michael J.; Sokoluk, Craig A.; Biological Sciences; Faculty of Science; University of Calgary
Open Access
Histological organization of the intestine in the crayfish Procambarus clarkii
(Blackwell Publishing, 2004-04) To, Terence H.; Brenner, Tracy L.; Cavey, Michael J.; Wilkens, Jerrel L.; Biological Sciences; Faculty of Science; University of Calgary
Six longitudinal ridges span the length of the intestine in the crayfish Procambarus clarkii . A simple columnar epithelium with tetralaminar cuticle lines the lumen. Folds of the epithelium overlie a dense irregular connective tissue packed with mixed acinar (alveolar) glands. Mucous secretions are probably involved with formation and lubrication of faecal strings; neither the nature nor the role of the serous secretions is immediately apparent. Aggregations of cells with large cytoplasmic vacuoles, called bladder cells, appear in the subepithelial connective tissue near the tops of the intestinal ridges. The bladder cells are suitably positioned to bolster the integrity of the ridges. Striated muscle of the intestine occurs in inner longitudinal and outer circular layers. The inner longitudinal layer consists of six strips, with one strip associated with the base of each intestinal ridge. The outer circular layer is essentially complete, but there are periodic apertures in this layer on the left and right sides of the intestine, providing nerves and haemolymph vessels with access to the interior of the gut. Based on histological features, and consistent with reports on other crayfish, we conclude that the intestine of P. clarkii has a proctodeal (ectodermal) origin.
Open Access
Microscopic anatomy of the thin-walled vessels leaving the heart of the lobster Homarus americanus: anterior lateral arteries
(Blackwell Publishing, Inc., 2006) Cavey, Michael J.; Chan, Kincaid S.; Wilkens, Jerrel L.; Biological Sciences; Faculty of Science; University of Calgary
The anterior lateral arteries are paired vessels leaving the anterior end of the lobster (Homarus americanus) heart and proceeding to the antennae and eyestalks, the stomach and hepatopancreas, the gonads, and the thoracic and branchial muscles. These vessels have a trilaminar organization, consisting of a tunica interna with elastic fibrils, a tunica intermedia represented by a bilayered cell mass, and a tunica externa with collagen fibrils. In the tunica intermedia, cells flanking the tunica interna (light cells) show less affinity for basic dyes and electron stains than those flanking the tunica externa (dark cells). Each light cell exhibits an irregularly shaped stress fiber (a bundle of closely packed microfilaments) in the region adjoining the tunica interna. Collectively, these bundles have a circumferential or slightly oblique orientation relative to the lumen of the vessel. The role of the stress fibers is unresolved. If they are static structures, they might contribute to the non-linear elasticity shown by lobster arteries. If they generate force, and small bundles of microfilaments do diverge from the stress fibers to enter filamentous mats applied to the plasmalemmata, a coordinated contraction of the cells might reduce the luminal diameter and, thus, retard the flow of hemolymph. Coordination of contraction would have to occur in the absence of nerves and without the benefit of communicating (gap) junctions between the light and dark cells.
Open Access
Morphology and distribution of a deep-water Narcomedusa (Solmarisidae) from the northeast Pacific
(Consejo Superior de Investigaciones Cientificas, 2000) Cavey, Michael J.; Needler Arai, Mary; Moore, Beverley A.; Biological Sciences; Faculty of Science; University of Calgary
Open Access
Organization of a phyllobranchiate gill from the green shore crab Carcinus maenas (Crustacea, Decapoda)
(Springer-Verlag, 1990) Cavey, Michael J.; Goodman, Saul H.; Biological Sciences; Faculty of Science; University of Calgary
The phyllobranchiate gills of the green shore crab Carcinus maenas have been examined histologically and ultrastructurally. Each gill lamella is bounded by a chitinous cuticle. The apical surface of the branchial epithelium contacts this cuticle, and a basal lamina segregates the epithelium from an intralamellar hemocoel. In animals acclimated to normal sea water, five epithelial cell types can be identified in the lamellae of the posterior gills: chief cells, striated cells, pillar cells, nephrocytes, and glycocytes. Chief cells are the predominant cells in the branchial epithelium. They are squamous or low cuboidal and likely play a role in respiration. Striated cells, which are probably involved in ionoregulation, are also squamous or low cuboidal. Basal folds of the striated ceils contain mitochondria and interdigitate with the bodies and processes of adjacent ceils, Pillar cells span the hemocoel to link the proximal and distal sides of a lamella. Nephrocytes are large, spherical cells with voluminous vacuoles. They are rimmed by foot processes or pedicels and frequently associate with the pillar cells. Glycocytes are pleomorphic cells packed with glycogen granules and multigranular rosettes. The glycocytes often mingle with the nephrocytes. Inclusion of the nephrocytes and glycocytes as members of the branchial epithelium is justified by their participation in intercellular junctions and their position internal to the epithelial basal lamina.
Open Access
Organization of the coelomic lining and a juxtaposed nerve plexus in the suckered tube beet of Parastichopus californicus (Echinodermata: Holothuroidea)
(John Wiley & Sons, Inc., 2006) Cavey, Michael J.; Biological Sciences; Faculty of Science; University of Calgary
The coelomic lining of the water-vascular canal in a suckered tube foot from the sea cucumber, Parastichopus californicus, is a pseudostratified myoepithelium consisting of flagellated adluminal cells and myofilament-bearing retractor cells. The bodies of adluminal cells flank the water-vascular canal and send basal processes between the underlying retractor cells to confront the podial connective tissue. Retractor cells have a contractile apparatus of unregistered thick and thin myo- filaments. The contractile apparatus is confined to the medullary sarcoplasm and oriented parallel to the primary axis of a tube foot. The bodies and processes of retractor cells intermingle with the basal processes of adluminal cells at the basal lamina of the coelomic lining. A ganglionated nerve plexus in the podial connective tissue approximates the basal lamina. Neuronal connectives link the ganglia to one another and to the nerve plexus in deep sectors of the podial epidermis. External laminae enveloping the ganglia and connectives in the podial connective tissue are continuous with the basal lamina of the epidermis. The adventitial nerve plexus, since it merges with the epidermal nerve plexus, is a component of the ectoneural division of the echinoderm nervous system. J. Morphol. 267:41–49, 2006. © 2005 Wiley-Liss, Inc.
Open Access
Ornate Setae on the Branchial Flabella ("Grill Rakers") of the Green Shore Crab Carcinus maenas (Crustacea: Decapoda)
(Blackwell Publishing, 1992) Cavey, Michael J.; Modi, Eech; Wilkens, Jerrel L.; Biological Sciences; Faculty of Science; University of Calgary
Open Access
Osmium-Fixed and Epon-Embedded Whole Mounts of Delicate Specimens
(Blackwell Publishing, 1973) Cavey, Michael J.; Cloney, Richard A.; Biological Sciences; Faculty of Science; University of Calgary
Osmium-fixed and Epon-embedded whole mounts of delicate specimens. An osmium fixative and an epoxy mountant were used to prepare delicate organisms and tissues as whole mounts for light microscopy. Fine structural details are well preserved by the technique, and common artifacts of whole mount preparation are largely eliminated. The final specimens are suitable as bright field objects or as phase/quasi-phase objects.
Open Access
Specializations for Excitation-Contraction Coupling in the Podial Retractor Cells of the Starfish Stylasterias forreri
(Springer-Verlag, 1981) Cavey, Michael J.; Wood, Richard L.; Biological Sciences; Faculty of Science; University of Calgary
Ultrastructural examination of the podium of the asteroid echinoderm Stylasterias forreri has revealed that cells of the coelomic epithelium and cells of the retractor muscle should be considered as components of a single epithelium. The podial retractor cells are, therefore, myoepithelial in nature. This report concentrates on those ultrastructural features of the retractor cells that are most likely involved with excitation-contraction coupling. The spatial arrangement of the sarcoplasmic reticulum, the couplings between the sarcoplasmic reticulum and sarcolemma, and an intramembranous specialization of the sarcolemma are documented and discussed. Current concepts regarding the innervation of the retractor cells of the podium and the protractor cells of the ampulla are reviewed; and specific proposals for further investigation of podial innervation are outlined.