bluuebunny/crossref_metadata_2025_split huggingface dataset:
Zymogen granule size in pancreas of nursing rats
Authors: Ermak Thomas H. , Rothman S. S. 
Published: February 2005

AbstractDramatic depression in granule volume density and size was measured in acinar cells of postnatal rat pancreas following the initiation of feeding. Volume density decreased about threefold from 45% at birth to 16% 2 days thereafter. Mean granule diameter decreased from 1.50 μm to 0.80 μm, an 85% decrease in corresponding granule volume. At the same time, numerical density approximately doubled. At 2 days after birth, cells with smaller granules had lower volume densities, and differences in mean granule volume between cells accounted for most of the differences in volume density. Although the distribution of granule diameter in newborns was lognormal, the distribution at 2 days was heavily skewed to larger sizes. This was the result of skewed distributions within individual cells and not an artifact of sampling. The results corroborate the central role of granule volume in determining changes in the volume density of zymogen granules in the pancreas and suggest that zymogen granules can act as capacitors that can change size as a function of the enzyme contained within.
Differential localization of vasopressin‐ and oxytocin‐immunoreactive cells and conventional neurosecretory cells in the ganglia of the earthworm Pheretima hilgendorfi
Authors: Kinoshita Kiyoshi , Kawashima Seiichiro 
Published: February 2005

AbstractCells containing arginine vasopressin (AVP)‐ and oxytocin (OXT)‐like substances were immunohistochemically visualized in the cerebral, subesophageal, and ventral nerve cord ganglia of the earthworm Pheretima hilgendorfi. Whether these anti‐AVP– and anti‐OXT–reactive cells are identical with classical aldehyde fuchsin (AF)‐positive neurosecretory cells was tested in serial sections. In all ganglia, groups of scattered neuronal cell bodies and axons strongly reactive to AVP and OXT antisera were observed, but AF‐positive cells consisting of type a (dark blue) and type b (purple) cells were predominantly present in the cerebral and subesophageal ganglia. In the cerebral and subesophageal ganglia anti‐AVP– and anti‐OXT–reactive cells were generally larger than AF‐positive cells. Some AF‐positive cells were reactive either to anti‐AVP or anti‐OXT serum, but some failed to react to either serum. Anti‐AVP– and anti‐OXT–reactive cells were not immunoreactive to OXT and AVP antisera, respectively. Electron microscopic observations showed that the granules of type a cells were larger and less electron dense than those of type b cells and anti‐AVP–reactive cells. The present cytological observations clearly showed that AVP‐ and OXT‐like substances were widely present in the ganglionic cells of the earthworm
Evidence of a microtrabecular cytoskeletal lattice in glandular cells of hydrozoan planulae
Authors: Walch E. Timothy , Martin Vicki J. , Archer William E. 
Published: February 2005

AbstractHydrozoan planulae of Pennaria tiarella and Podocoryne carnea were processed for transmission electron microscopy using diethylene glycol distearate (DGD). The DGD functions as a removable embedding medium to produce embedment‐free sections of intact planulae. Images of glandular cells obtained using embedment‐free sections were compared with those from conventional Spurr‐embedded sections. In unembedded sections a large number of thin anastomosing fibers were observed throughout the cytoplasm of the glandular cell. The fibers appeared to coalesce in certain areas to form thick bundles of fibers that partitioned the glandular cytoplasm into spherical compartments. The meshwork of fibers is three‐dimensional and resembles a microtrabecular lattice. Mitochondria are suspended within and attached to the network of fibers, thus suggesting a cytoskeletal role of the fibers. This study documents the presence of a cytoplasmic fiber system within cells of intact invertebrate larvae.
Ultrastructure of duvernoy's gland from the wandering garter snake, Thamnophis elegans vagrans (Serpentes, Colubridae)
Authors: Kardong Kenneth V. , Luchtel Daniel L. 
Published: February 2005

AbstractIn addition to the supralabial glands (strips of glandular tissue lying along the maxilla), most snakes of the family Colubridae possess an enlarged oral gland lying behind the eye and emptying near the rear maxillary teeth, the Duvernoy's gland. Duvernoy's gland is most probably homologous to the venom gland of viperid and elapid snakes, and occasionally has been implicated in cases of human envenomation. Although of possible medical concern, there is reason to believe that secretion from this gland serves a biological role different from that of the venom gland, namely a role primarily in digestion rather then largely in rapid prey immobilization. The parenchyma of the Duvernoy's gland comprise two cell types, a serous cell containing numerous, electron‐dense secretory granules, and myoepithelial cells. There are no mucous cells in the parenchyma; instead cells of this type are located exclusively in the lining epithelium of the main duct. Numerous unmyelinated nerves pass between secretory acini. Observations of the supralabial gland reveal that this gland, in addition to serous cells, also contains mucous cells and a putative third cell type we designate as an intermediate cell.In cellular morphology, Duvernoy's gland is closest to the venom gland of elapids, and least like the venom gland of viperids. Compared to the venom glands in both families of venomous snakes, Duvernoy's gland lacks a large luminal secretory reservoir. Emptying of Duvernoy's gland is thought to involve release of secretion granules into the lumen, and movement of the secretory product from there may be supplemented by mechanical pressure exerted externally by nearby contracting striated mucles. These differences in structure and mechanism of secretion release are taken as evidence that although they are homologous, the two types of glands, Duvernoy's and venom glands, are functionally distinct.
The vacuolar cells of Oscarella lobularis (Porifera, Demospongiae): Ulatrastructural organization, origin, and function
Authors: Gaino Elda , Burlando Bruno , Buffa Paola 
Published: February 2005

AbstractThis work is concerned with the ultrastructural organization and some histochemical features of the vacuolar cells of the demosponge Oscarella lobularis. Vacuolar cells are characterized by large clear vacuoles containing an aqueous fluid. They are commonly found in the mesohyl of this sponge and tend to constitute a sort of parenchyma in the choanosome. Mobile cells of the mesohyl appear to differetiate into vacuolar cells through the progressive formation of wide cytoplasmic lacunae. We have identified four types of cells showing progressive transformation toward the vacuolar cell type. Precursors (types 1–4) of the vacuolar cells probably derive from endopinacocytes, since they share several histochemical and ultrastructural characteristics with them. Our data support the notion that vacuolar cells are involved in the synthesis of collagen, act as a mechanical support of the sponge body, and are eventually extruded from the sponge through the canals of the aquiferous system.
Comparative studies on the histology of the ovotestis in Hypselodoris tricolor and Godiva banyulensis (Gastropoda, Opisthobranchia), with special reference to yolk formation
Authors: Medina A. , Garcia J. C. , Moreno F. J. , Lopez‐Campos J. L. 
Published: February 2005

AbstractThe histology of the ovotestis was studied by light and electron microscopy in two nudibranch gastropod species. While in Hypselodoris tricolor the ovotestis is intimately associated with the digestive gland tissue, the large gonadal mass of Godiva banyulensis is placed freely in the haemocoele. This fact results in great histological differences between both species.As is common among Mollusca, the immature yolk granule in Hypselodoris and Godiva presumably originates from membrane‐rich cytoplasmic inclusions, which we have termed dense multivesicular bodies. Such inclusions consist of an outer membrane enclosing membrane remnants and a granular, electron‐dense material. These elements are accumulated and mixed in the center of the dense multivesicular body and could be actually transformed into the paracrystalline core of the immature yolk granule, the cortex of which is made up of part of the central accumulation materials that have not spread into the crystal. During vitellogenesis, some mitochondria are subjected to a process of transformation affecting mainly their inner membrane (including mitochondrial cristae) and matrix. However, the conversion of modified mitochondria into yolk precursors, as reported for other gastropod species, could not be determined with absolute certainty on the basis of our observations on static material.The mature yolk granule consists of a central paracrystalline core, similar in structure to that of the immature yolk granule, and a peripheral membranous cortex, which seems to spread centripetally, thus permitting the crystal to grow. The cortical material consumed in synthesizing the central core appears to be restored by addition of degenerative mitochondria to the yolk granule surface.
The rete mirabile cranica in the genus Mobula: A comparative study
Authors: Schweitzer Jeff , Notarbartolo‐Di‐Sciara Giuseppe 
Published: February 2005

AbstractDevil rays (Mobulidae) have large brains that rest in a voluminous chondrocranium almost completely filled by a rete mirabile cranica (RMC). The RMC is a massive arterial network grossly divisible into a “caudal RMC” supplying blood to the brain, and an expanded, more complex “precerebral RMC” nested within the large cranial cavity rostral to the telencephalon.Both the caudal and precerebral retia originate from the posterior portion of the profundae cerebri arteries, which lie ventral to the brain and form the sides of a vascular triangle, the base of which is anterior and formed by the joining of the internal carotids; the vertex is posterior and median, corresponding to the anterior extreme of the spinalis impar artery. Vessels of the caudal RMC branch posteriorly from the profundae cerebri and course over and into the brain. Vessels branching more anteriorly course rostrally to form the precerebral RMC, which takes the shape of the cranial cavity and completely envelops the olfactory peduncles. Large retial arteries (1‐mm diameter) branch and taper to about 50–150 μm, forming a system of small arteries or arterioles. Many give rise to a mesh of tertiary vessels (precapillary arterioles or capillaries, ca. 20–50 μm in diameter), which, along with arterioles, are embedded in the adventitia of these arteries, with which they communicate by numerous anastomoses. Although the function of the RMC remains enigmatic, its complexity and fine structure are suggestive, and hypotheses of its role are discussed.
The ultrastructure of the morula cells of Eupentacta quinquesemita (Echinodermata: Holothuroidea) and their role in the maintenance of the extracellular matrix
Authors: Byrne Maria 
Published: February 2005

AbstractThe ultrastructure of the morula cells of Eupentacta quinquesemita and the distribution of these cells in the dermal connective tissue are described. Morula cells are abundant in the dermis and appear to function in the maintenance of the extracellular matrix (ECM) as a source of ground substance material. The synthetic activity of these cells is described in detail. Morula cells are filled with large secretory vesicles containing three electrondense materials which are derived from rough endoplasmic reticulum and Golgi activity. The synthetic product of these cells contains glycosaminoglycans and is secreted into the ECM by degranulation. The ultrastructural and histochemical similarity of the degranulation product to the ECM ground substance suggests that they are comprised of the same material. Morula cells appear to function primarily in connective tissues where ground substance predominates. The cells often contain secretory vesicles at various stages of formation, all of which eventually mature and degranulate. The synthetic pathway of the morula cells appears to result ultimately in the complete disruption and death of the cells. The function of morula cells in the holothuroid ECM is discussed, and the synthetic activity of the cells is compared with that of other secretory cells.
Fine structure of the photosensitive iris of the toad, Bufo marinus
Authors: Rubin L. , Eller P. , Nolte J. 
Published: February 2005

AbstractThe iris of the toad Bufo marinus is directly photosensitive and will constrict in response to light striking only the iris. This is true even when the iris is isolated from the rest of the eye, and therefore from reflex neuronal influences initiated in the retina. This autonomous response is probably mediated by the sphincter pupillae muscle, since no specialized photoreceptors are present in the iris, nor does the sphincter exhibit any specializations likely to subserve a purely photoreceptive function. The photosensitive sphincter appears typical of smooth muscle and, like mammalian sphincters, possesses many intercellular junctions. The iris possesses a well‐developed neuronal plexus with fibers projecting into the sphincter muscle layer. Nerve terminals contain small, agranular (30–70nm) and large, dense‐cored (80–120nm) vesicles. No consistent postsynaptic specializations are seen on any cells of the iris, including the cells of the sphincter muscle. The anterior pigment epithelial cells of the iris appear specialized and resemble the myoepithelial dilator muscle described by Kelly and Arnold ('72) for the iris of rats.
Morphometric estimates of the surface areas of the tracheal and cuticular systems in Peripatus acacioi marcus and marcus (Onychophora)
Authors: Bicudo José Eduardo Pereira Wilken 
Published: February 2005

AbstractThe surface areas of the tracheal and cuticular systems of Peripatus acacioi individuals of different body weights were determined by morphometric analysis. The results demonstrate that both surfaces increase with body weight, although the observed increase in the surface area of the tracheal system appears to be at a greater rate. The slopes of the two regression lines obtained are statistically different. It is therefore suggested that the preferential route for water loss in P. acacioi is related to the size of the animals, i.e., smaller onychophorans would lose water mainly through the cuticle, while larger ones would lose water through the respiratory surfaces.
Embryonic development of Bithynia tentaculata L. (Prosobranchia, Gastropoda). I. Cleavage
Authors: Van Dam W. I. 
Published: February 2005

AbstractThe cell‐lineage of Bithynia tentaculata L. has been studied through the formation of the fourth quartet of micromeres, i.e., the 81‐cell stage. Up to the 28‐cell stage, the cleavage pattern is radially symmetrical, and the divisions take place synchronously in the quadrants. Bilateral symmetry is established by the formation of the mesentoblast 4d at the future dorsal side. A resting stage preceding the formation of 4d is lacking. The mesentoblast 4d is formed earlier than the other fourth quartet cells, and it divides twice before 4a‐4c are formed. Bilateral symmetry in the molluscan cross becomes apparent by different divisions of the tipcell and the basal cell in the dorsal arm. Dorsoventrality is progressively corroborated by the divisions in the second and third quartets of micromeres, which take a different course in the A and B quadrants on the one side and in the C and D quadrants on the other side.
Pigment epithelial ensheathment and phagocytosis of rod tips in the retina of Rana catesbeiana
Authors: Tsukamoto Yoshihiko 
Published: February 2005

AbstractTwo modes of shedding of rod disc membranes were observed by electron microscopy in bullfrog retinas illuminated for various periods from 10 min to 2 hr. One mode is “autonomous shedding” whereby rods shed disc packets directly into the subretinal space. Most of the discarded disc packets are subsequently brought into contact with villous apical processes of pigment epithelial (PE) cells and are ultimately engulfed by these cells. When some of the shed disc membranes remain in the subretinal space, it appears that these remanants may be phagocytized by ameboid phagocytes. The other mode is “cooperative shedding” whereby rods shed disc packets with the participation of pigment epithelial ensheathment. Shedding of a disc packet from a rod tip, and enclosing of the rod tip by a broad, sleeve‐like apical process of a PE cell, take place simultaneously. The separated disc packets may be immediately engulfed by the PE cells without risk of failure. Both villous and sleeve‐like types of apical processes of PE cells in the bullfrog lack pigment granules, in contrast to the finger‐like apical processes that do contain pigment granules. Villous and sleeve‐like apical processes that do contain pigment granules. Villous and sleeve‐like processes therefore probably belong to the same category as the leaf‐like apical processes of PE cells in mammalian retinas.
Vascularization of a lobster muscle
Authors: Govind C. K. , Guchardi John 
Published: February 2005

AbstractThe vascularization of the distal accessory flexor muscle (DAFM) in the walking legs of the lobster, Homarus americanus, was examined with dye injection and electron microscopy. Vascularization of this flat, thin DAFM is via two vessels, one supplying the tendinal region of the muscle and the other the exoskeletal region. The vessels that originate from the single major limb vessel, subdivide extensively over the DAFM and form a profuse network that has hitherto gone unnoticed. The degree of vascularization of individual fibers was determined by periodic sampling along its length with thin‐section electron microscopy. At each and every sampling station, individual fibers had several (seven to eight), small‐diameter (4 μm) blood vessels in their cross‐sectional profile. In contrast, nerve terminals of the excitor and inhibitor axon were rarely encountered. This high degree of vascularization was found amongst fibers that are from different regions of the DAFM and differ in the performance of their excitatory synapse but are similar in their structural and contractile properties.
Development of extracellular matrix in chick paravertebral sympathetic ganglia
Authors: Luckenbill‐Edds Louise 
Published: February 2005

AbstractAlcian blue staining coupled with enzyme digestion or critical electrolyte staining revealed differences in the development of extracellular matrix (ECM) within sympathetic ganglia compared with the surrounding capsule. On day 5 of chick development (Hamburger‐Hamilton stage 26) only hyaluronic acid (HA) could be detected in the ECM surrounding condensing primary ganglia. By day 7 (st 30) the ganglionic capsule contained HA, as well as sulfated glycosaminoglycans (GAGs), and this pattern continued into the adult stage. During the later stages of embryonic life (st 41–45) satellite cells appear, showing fine structural characteristics that point to their role in the secretion of intraganglionic ECM. Only during these stages could ECM be detected histochemically within ganglia, the same stages (days 15–19) when routine electron microscopic methods reveal collagen fibrils embedded in a granular ground substance. Thus, the intranganglionic environment appears as a separate compartment free of detectable amounts of GAG until late embryonic stages when ECM is secreted around satellite cells. This developmental pattern could represent a role of ECM in the histological stabilization of ganglia during the late stages of differentiation, since the appearance of intraganglionic ECM is correlated with the appearance of small dense‐cored vesicles characteristic of adult neurons. The developmental pattern of ECM in differentiating sympathetic ganglia is compared with that of other tissues that undergo condensation and morphogenesis.
Fine structure of spermatophores of some Oribatid mites (Acari, Arachnida)
Authors: Kümmel Georg , Dobner Christa 
Published: February 2005

AbstractThe ultrastructure of spermatophores was studied in seven species of Oribatei. Each spermatophore is composed of a head and a stalk which is attached to the substratum. The spherical head consists of two distinct portions: (1) the sperm package; and (2) the head matrix. Position and structure of the sperm package are described in the different species, as well as the various structures in the head matrix. The sperm package contains sperm embedded in secretory products. The most characteristic feature of the sperm is an electron‐dense chromatin body. Mitochondria lie adjacent to it or are partly or completely incorporated into the chromatin body. The cytoplasmic surface of the plasma membrane regularly bears an electron‐dense layer; the plasma membrane is covered by a secretory sheath. The spermatophores of the Oribatei are structurally complicated and not uniform. The possible role of the spermatophore's structural elements is discussed and an attempt is made to evaluate characteristic features taxonomically.
Ultrastructure and function of the circulatory organs of Leiobunum limbatum and two other species of harvestmen (arachnida: Opiliones)
Authors: Dannhorn D. R. , Seitz K. A. 
Published: February 2005

AbstractThe ultrastructure of the circulatory organs of Leiobunum limbatum, Mitopus morio, and Rilaena triangularis (Arachnida: Opiliones) has been investigated. We studied the organization of the heart, the myocardial contractile elements, its tubular system, organelles, and cell‐junctions. The epicardium exhibits a large number of longitudinally arranged microtubules and is attached to the myocardium by special membrane complexes. Because of these structures, the epicardium is interpreted as the elastic antagonist to the heart muscle. At both ends of the heart the epicardium continues into a nonbranching aorta. Consequently the ultrastructure of the aortal wall, containing numerous microtubules, is similar to the ultrastructure of the epicardium. At the posterior end of the heart is a muscular slit‐valve, while at the anterior end is a lobe‐valve that lacks contractile elements. The heart is innervated by a dorsal ganglion. It covers the entire length of the heart and contains neural and glial cells. Two different types of neurosecretory granules and both electron‐dense and electron‐lucent synaptic vesicles are described.