bluuebunny/crossref_metadata_2025 huggingface dataset:
Histological study of muscular hypoplasia in the crooked neck dwarf mutant (cn/cn) chick embryo
Authors: Wick Robert A. , Allenspach Allan L.
Published: February 2005

Tibiotarsal segments of 12‐day chick embryos homozygous for the crooked neck dwarf gene (cn/cn) were examined histologically following routine methods of preparation. The myogenic mass fails to divide into separate muscle bundles during the early stages of differentiation. Myoblasts and myotubes are observed, although the proportion favors the mononucleate cell population. Multinucleate myotubes are often wavy in appearance and many contain eosinophilic cytoplasmic inclusions. The entire tissue mass of mutants appears more compacted than in control limbs. Poor organization of muscle appears related to the lack of a suitable connective tissue system. Epimysia, perimysia, and subcutaneous connective tissue fail to develop properly. Tendons are poorly developed or absent. Comparisons between mutant and control embryos show no differences in peripheral innervation. Nerve fascicles penetrate deeply into the developing muscle of both species. The distribution of vascular elements is seemingly normal also. Skeletal muscle of cn/cn embryos is capable of differentiating to the myotube stage, after which it undergoes cellular degeneration without achieving a functional state. Comparisons of this mutant with alleged chemical phenocopies show important differences.
Seasonal ultrastructural variations in pinealocytes of the woodchuck, Marmota monax
Authors: Frink R. , Krupp P. P. , Young R. A.
Published: February 2005

The ultrastructure of the pinealocyte in the woodchuck, Marmota monax, was studied during the four seasons of the year. Fall cells have a fairly uniform cytoplasmic density, organelles consistent with synthetic and/or secretory activity and rather extensive pericapillary and intercellular spaces. Many winter pinealocytes are nearly devoid of ribosomes and granular endoplasmic reticulum but contain lipid droplets associated with mitochondria. Pericapillary and intercellular spaces are minimal. Spring glands have the greatest variation in cytoplasmic density with intercellular and pericapillary spaces similar to that seen in fall glands. Cells containing electron dense cytoplasm have Golgi zone associated, secretory granules, free ribosomes, short sections of granular endoplasmic reticulum and dense bodies. Cells with a more electron lucent cytoplasm are similar to the most frequently observed summer pinealocytes which have numerous Golgi zones but few associated secretory granules. Microtubules are prominent in the cytoplasm of these cells, the plasma membranes are smooth and intercellular and pericapillary spaces are minimal. A yearly rhythm or cyclic activity of the pinealocyte is suggested.
Fine structure and metamorphosis of the wax gland cells in a psyllid insect, Anomoneura mori schwartz (Homoptera)
Authors: Waku Yoshio
Published: February 2005

The fine structure of the wax gland of Anomoneura nymph and its metamorphic change were investigated. In the nymph, this organ encircles the anus, and consists of two kinds of cells, derived from epidermal cells: (1) very tall, slim wax cells, which produce and secrete the wax, and (2) flat interstitial cells found among the wax cells. The whole gland is covered by a wax‐secreting cuticle with a delicate surface sculpture. Each wax cell has a long, wide duct which opens at the cuticle and penetrates the entire cell. Its cytoplasm is rich in mitochondria and smooth endoplasmic reticulum while that of interstitial cells contains rough endoplasmic reticulum. During each nymphal molt, the cluster of primordial wax gland cells — derived from the epidermis — proliferates rapidly and forms the gland of the next instar. The gland of the preceding instar meanwhile degenerates. Interstitial cells play an important role in cuticle formation and shedding at each molt. These cells alone produce and deposit the new cuticle of the next instar; the wax cells, specialized for wax production, cannot produce cuticle. The apical portion of the wax cell is cut off from the main cell body by growth of the surrounding interstitial cells. Thereafter, the wax cells degenerate, resulting in the rapid disappearance of the previous instar's wax gland. Adults lack this gland entirely.
Ultrastructural features of neuromuscular junctions in the stapedius muscle of Gallus gallus
Authors: Counter S. Allen
Published: February 2005

The ultrastructure of neuromuscular junctions in the twitch fibers of the stapedius muscle of Gallus gallus (domesticus) was investigated as part of a series of neurophysiological studies. Among the morphological features observed were elongated end‐plates with numerous large and clear synaptic vesicles mixed with larger dense core vesicles and irregular or aperiodic “active sites” in the presynaptic membrane where synaptic vesicles were focused. The most remarkable features of these junctions were large synaptic clefts (50‐80 nm) and the absence of junctional folds in the sarcolemmal surface. Unlike the large periodic junctional folds seen in the neuromuscular junctions of frogs and in the fast twitch fibers of the mammalian stapedius, the preparations studied only show small aperiodic invaginations (primitive folds) in the postsynaptic membranes. This morphological feature remains essentially constant from newly hatched to adult chickens. While these smooth junctions are consistent with earlier findings of inconspicuous junctional folds in the twitch fibers of the chicken posterior latissimus dorsi they are unlike those seen in the fast twitch fibers of the mammalian stapedius muscle, or other twitch fibers in general. The morphological findings of the present study may also suggest that the simple, unmodified neuromuscular junctions in the stapedius of Gallus may be a useful preparation for studies of synaptic membrane structures that employ the freeze‐fracture technique.
Ultrastructural investigation of spermiogenesis in Peripatopsis capensis (Onychophora)
Authors: Camatini Marina , Franchi Emilia , Saita Abele
Published: February 2005

Early spermatids of the onychophoran Peripatopsis capensis are spherical cells with a centrally located nucleus, numerous mitochondria, Golgi complexes, microtubules and two centrioles. During spermiogenesis, Golgi vesicles migrate to one side of the cell where they form a tight aggregate, which is later shed. The mature spermatozoon has no acrosome. Several mitochondria fuse to form a middle piece containing three large mitochondria. Nucleus and middle‐piece elongate, presumably under the influence of helically twisted microtubules. Outside this set of microtubules a continuous layer of endoplasmic reticulum cisternae is formed which separates the interior portion of the cell from an external cytoplasmic rim, which is later shed. Outside the 9 + 2 complex, the tail presents nine accessory microtubules, and a peripheral layer of microtubules beneath the plasma membrane. The enforcement of the tail structure may be related to the fertilization biology of this animal, which is by “hypodermal” impregnation.
Ultrastructure of the accessory glands of the Mediterranean flour moth
Authors: Riemann John G. , Thorson Barbara J.
Published: February 2005

Five regions are recognized in the accessory glands of the Mediterranean flour moth, Anagasta kuehniella (Zeller), on the basis of cellular morphology and aggregates of secretory material in the lumen. Some variation is found in each of the posterior four regions, especially the third one. In the most anterior region (region 1) the epithelium is composed of a single type of cell, while in each of the other regions there are two classes of cells. The cells of region 1 and one class in each of the other four regions are fairly typical exocrine cells with extensive rough endoplasmic reticula. Secretion is primarily via Golgi‐derived vesicles. Apocrine secretion in the form of sloughing off of the apical cytoplasm probably also occurs in all regions but is most prominent in the posterior two regions. One class of cells is very similar in morphology in each of the posterior four regions though their secretory products form characteristic aggregates in the lumen. The second class of cells (foliate cells) occurring in the posterior four segments is most notably characterized by elongate apical projections that extend out into the lumen. The apical projections contain large quantities of glycogen, some microtubules, and, in some cases, many minute mitochondria. The membrane content of the projections is also very high. In the anterior regions, the membranes are mostly fused in pairs and typically form multilayered whorls. Fusion and whorl formation decrease in the posterior regions. The cytoplasm of the foliate cells has a high organelle content including many lysosomes and mitochondria. The latter exhibit considerable polymorphism, with particular forms occurring in the different regions of the glands. The apical projections of the foliate cells are detached during copulation, presumably as the result of nervous stimulation, and become a part of the ejaculate. Replenishment of all secretory material, including the apical projections, occurs after copulation.
Fibrous and adhesive components of the orb webs of Araneus trifolium and Argiope trifasciata
Authors: Kavanagh Edward J. , Tillinghast Edward K.
Published: February 2005

The minimum number of secretion products used by the spiders Araneus trifolium and Argiope trifasciata to construct their orb webs has been established by selective enzyme digestion and histochemical staining, as well as differential isotope localization in these webs. Three fiber types are present in the webs: (a) a major fiber found throughout the web, (b) a minor fiber found only in radial threads, and (c) the core fibers of the sticky spiral thread. Three nonfibrous secretions are found on these fibers. These include a water soluble viscid coating of the sticky spiral and two adhesives which fasten the threads of the web together; one found only at junctions of sticky spiral and radial threads and the other at all other thread connections. The possible glandular sources of these secretions are discussed.
A model to explain the posterior limit of the bite point in reptiles
Authors: Druzinsky Robert E. , Greaves W. S.
Published: February 2005

A biomechanical model of the jaw mechanism in some reptiles is presented. Symmetrical muscle activity that produces equal forces on both sides of the head is assumed. The model predicts the position of the most posterior bite point and offers a functional explanation for this prediction. Turtles are used to illustrate the idea.
The functional significance of primate mandibular form
Authors: Hylander William L.
Published: February 2005

A stress analysis of the primate mandible suggests that vertically deep jaws in the molar region are usually an adaptation to counter increased sagittal bending stress about the balancing‐side mandibular corpus during unilateral mastication. This increased bending stress about the balancing side is caused by an increase in the amount of balancing‐side muscle force. Furthermore, this increased muscle force will also cause an increase in dorsoventral shear stress along the mandibular symphysis. Since increased symphyseal stress can be countered by symphyseal fusion and as increased bending stress can be countered by a deeper jaw, deep jaws and symphyseal fusion are often part of the same functional pattern. In some primates (e.g., Cercocebus albigena), deep jaws are an adaptation to counter bending in the sagittal plane during powerful incisor biting, rather than during unilateral mastication.

The stress analysis of the primate mandible also suggests that jaws which are transversely thick in the molar region are an adaptation to counter increased torsion about the long axis of the working‐side mandibular corpus during unilateral mastication. Increased torsion of the mandibular corpus can be caused by an increase in masticatory muscle force, an increase in the transverse component of the postcanine bite force and/or an increase in premolar use during mastication.

Patterns of masticatory muscle force were estimated for galagos and macaques, demonstrating that the ratio of working‐side muscle force to balancing‐side muscle force is approximately 1.5:1 in macaques and 3.5:1 in galagos during unilateral isometric molar biting. These data support the hypothesis that mandibular symphyseal fusion is an adaptative response to maximize unilateral molar bite force by utilizing a greater percentage of balancing‐side muscle force.
Presence and development of a sensory formation in the eyestalk of the crayfish, Astacus leptodactylus (Nordmann, 1842), during its embryonic, larval and adult life
Authors: van Herp François , Bellon‐Humbert Chantal , De Groot Adrianus J. M.
Published: February 2005

A sensory papilla is described in the eyestalk of the crayfish Astacus leptodactylus during the last embryonic stages and during larval stages by light microscopy. This region was also investigated with the scanning electron microscopy, which showed sensory hairs in the postmolt adult; they disappear during intermolt and premolt. Simultaneous cyclic changes in hair papillae are observed in the hypodermis. The possibility of a chemoreceptive function is discussed.
Ultrastructure of the parathyroid gland of the japanese lizard in the spring and summer season
Authors: Isono Hideo , Shoumura Shizuko , Ishizaki Noriko , Hayashi Kazuko , Yamahira Tomo
Published: February 2005

The ultrastructure of the parathyroid glands of adult Japanese lizards (Takydromus tachydromoides) in the spring and summer season was examined. The parenchyma of the gland consists of chief cells arranged in cords or solid masses. Many chief cells contain numerous free ribosomes and mitochondria, well‐developed Golgi complexes, a few lysosome‐like bodies, some multivesicular bodies and relatively numerous lipid droplets. The endoplasmic reticulum is mainly smooth‐surfaced. Cisternae of the rough endoplasmic reticulum are distributed randomly in the cytoplasm. Small coated vesicles of 700‐800 Å in diameter are found occasionally in the cytoplasm, especially in the Golgi region. The chief cells contain occasional secretory granules of 150‐300 nm in diameter that are distributed randomly in the cytoplasm and lie close to the plasma membrane. Electron dense material similar to the contents of the secretory granules is observed in the enlarged intercellular space. These findings suggest that the secretory granules may be discharged into the intercellular space by an eruptocrine type of secretion. Coated vesicles (invaginations) connected to the plasma membrane and smooth vesicles arranged in a row near the plasma membrane are observed. It is suggested that such coated vesicles may take up extracellular proteins. The accumulation of microfilaments is sometimes recognized. Morphological evidence of synthetic and secretory activities in the chief cells suggests active parathyroid function in the Japanese lizard during the spring and summer season.
The mouthparts of female Corethrella brakeleyi and C. wirthi (Diptera: Chaoboridae)
Authors: McKeever Sturgis , Pound J. Mathews
Published: February 2005

The mouthparts of female Corethrella brakeleyi and C. wirthi were studied using light and electron microscopy. Mandibles, hypopharynx and labium are highly sclerotized and are modified for obtaining blood meals. All structures were larger in C. brakeleyi than in C. wirthi except mandibular and hypopharyngeal teeth; these were smaller and more numerous in C. brakeleyi. The labium of both species terminates in peg‐like structures which are similar to those reported from several genera of mosquitoes. Sensillae on the second segment of the maxillary palps appear to be identical to those described in both biting and nonbiting male and female blackflies.
The morphology of the sex pheromone gland in Drosophila grimshawi
Authors: Hodosh R. J. , Keough E. M. , Ringo J. M.
Published: February 2005

The morphology of a sex pheromone‐producing gland found in the abdomen of Drosophila grimshawi males was studied by light and electron microscopy. This gland, consisting of two intra‐anal lobes, contains cells that resemble those of other insect pheromone glands. However, in contrast to many other insect pheromone glands that release pheromone through the cuticle, cells of the intra‐anal lobes secrete into a canaliculi‐duct system that empties into the anal region. The liquid secretory product flows along the surface of the intra‐anal lobes and is brushed onto the substrate by fingerlike projections on the lobes' surfaces.
Ultrastructure of the sacculus and lagena in a moray eel (Gymnothorax sp.)
Authors: Popper Arthur N.
Published: February 2005

The ultrastructure of the sacculus and lagena of a moray eel, Gymnothorax sp., was investigated using scanning and transmission electron microscopy. Particular emphasis was placed on the orientation of the sensory hair cells and on the ultrastructure of the sensory cells. The ciliary bundles on the sensory hair cells are of several types, each having a different size relationship between the kinocilium and stereocilia. The cell bodies of the sensory cells are similar to the mammalian type II sensory cell. There were no apparent differences in the cell bodies between sensory cells with different ciliary bundles.

Hair cell orientation patterns on the saccular and lagenar maculae differ from patterns found in other fishes. The posterior side of the saccular macula in Gymnothorax has cells oriented dorsally and ventrally, as is typical in other non‐ostariophysan species. The anterior end of the saccular macula has alternating groups of anteriorly and posteriorly oriented cells, a situation that differs from the more typical pattern in which anteriorly oriented cells are found on the ventral side of the macula while posteriorly oriented cells cover the dorsal side of the macula. The orientation of cells on the lagena includes ventral cells that are located above a group of dorsally oriented cells. In many other non‐ostariophysans, ventrally oriented cells are generally posterior to the dorsally oriented cells.
A comparative light and electron microscopic study of the pineal complex in the deep‐sea fishes, Cyclothone signata and C. acclinidens
Authors: McNulty John A.
Published: February 2005

The pineal complexes of the two closely related deep‐sea fishes Cyclothone signata and C. acclinidens were compared both qualitatively and quantitatively. Photoreceptor and supportive cells were identified in both species. The deeper‐dwelling species, C. acclinidens, had a significantly greater number of photoreceptor‐cell outer segment saccules and a higher ratio of receptor cells to nerve fibers in the pineal stalk. It was suggested that these indicate increased photosensitivity of the pineal. Supportive cells were sometimes seen to contain arrays of undulating tubules. The functional significance of these tubules is not understood. A prominent dorsal sac is closely associated with the pineal end‐vesicle. Both structures appear to have a common vascular supply suggesting that they are functionally related. Dorsal sac cells contained abundant mitochondria, glycogen, and large filament‐like inclusions.
Cell death and optic fiber penetration in the optic stalk of the chick
Authors: Ulshafer Robert J. , Clavert André
Published: February 2005

The role of dying cells in the optic stalk in relation to retinal fiber migration was investigated in the chick embryo. Cell death was analysed at various stages of development by counting pycnotic nuclei and also by the Gomori acid phosphatase reaction, while nerve fibers were visualised by the Bodian method. A wave of cell death, beginning in the neural retina at stage 18 and advancing with time through the stalk towards the diencephalon, occurred simultaneously or slightly prior to differentiation and migration of ganglion cell axons. Cell death stopped and gliogenesis occurred in the stalk after penetration by retinal fibers. Cell death occurred in the stalk even when fiber penetration was prevented by optic cup ablation. In this case, necrosis ensued until almost complete degeneration of the stalk, usually within three days after the operation, and gliogenesis did not occur. As the stalk degenerated, its cells became heavily pigmented. These observations suggest that the onset of cell death in the optic stalk is determined prior to and independently of retinal fiber penetration. On the other hand, cessation of cell death and subsequent gliogenesis occur only in the presence of ingrowing optic fibers.
Comprehensive schemata on the histology of the liver with consequences in terminology
Authors: Preuss F. , Fricke W.
Published: February 2005

New schemata of the liver are presented to discuss the combination of the three kinds of liver lobules known until today in a chalk‐talk‐manner. Terminology is also discussed. Further investigations are needed involving the construction and the vascular pattern of compound lobules of the three individial lobules of the liver in different species.
The structural organization of the pineal complex in the domestic goose
Authors: Mahon Susan , George John C.
Published: February 2005

The light and electron microscopic structure of the pineal complex of the domestic goose was studied. The complex is tubulofollicular but there is no direct connection between the constituent system of ducts and the third ventricle of the brain. Within the pineal, blood vessels accompanied by sympathetic nerve bundles are confined to the connective tissue. Other nerve fibers and occasional nerve cell bodies, however, do occur among the pineal cells.

Three basic pineal cell types were distinguished: (1) elongate epithelial cells which are arranged around follicles and ducts and resemble degenerate photo‐receptor cells; (2) intramural supportive cells which are interspersed with elongate epithelial and intramural supportive cells; and (3) small supportive cells which lie between the bases of the elongate epithelial and intramural supportive cells. The follicular structure, vascularization, presence of secretory granules, and the nature of the elongate epithelial cells indicate that the pineal complex is primarily endocrine though a possible photoreceptive function cannot be ignored. Vesicles, 100‐300 and 40‐100 nm wide, were found within nerves and intramural supportive cells. The larger vesicles, present in pineals collected in the night, probably contain peptidic hormones. The smaller vesicles present in both day and night samples probably contain aminergic hormones.
Nature and cellular origin of the adhesive coats of the lamprey egg (Petromyzon marinus)
Authors: Yorke Marc A. , McMillan Donald B.
Published: February 2005

Cell surface coats are important in adhesion and other cellular activities. The lamprey egg possesses a surface coat that has been divided into two morphologically and functionally distinct regions. The amorphous apical tuft forms a cap over the animal pole, while the elaborately‐textured adhesive coat covers the ventral two‐thirds of the egg. This latter area is composed of saccules that form rosettes over the egg surface and is derived from the remains of specialized follicular cells which break down during ovulation. The adhesive qualities of these coats may be inhibited or abolished by various proteins and sulphydryl‐blocking agents, thereby implicating, as a possible source of this adhesion, classes of acid and sulphated glycoproteins and glycosaminoglycans which occur on the egg surface.
Structure and formation of ankylosis in Xenopus laevis
Authors: Katow Hideki
Published: February 2005

The structure of ankylotic teeth in Xenopus laevis was studied by light, transmission, and scanning electron microscopy as well as by microradiography in decalcified and undecalcified specimens.

The mature teeth of Xenopus laevis are calcified from the crown to the base, fused to the jaw bone, and have no uncalcified area, such as a fibrous ring separating the tooth into the crown and pedicle. Microradiography shows that the mature tooth and jaw bone appear as an X‐ray opaque area, except for the basal region of the dentine. This region is composed of an X‐ray translucent area and an X‐ray opaque thin layer on the lingual side of the translucent area. The mature tooth is composed of two differently calcified areas: (1) a highly calcified area, which makes up almost all of the tooth and contains a thin layer of the basal dentine on the lingual side, and (2) a lowly calcified basal dentine, which is fused to the jaw bone. Therefore, the lowly calcified area does not completely separate the dentine and jaw bone.

Repeating banding patterns among the collagen fibrils differ among the dentine‐forming area and the matrices of dentine and jaw bone. During the formation of ankylosis of the tooth germ, collagen bundles in the dentine‐forming area accumulate directly on the surface of the jaw bone. Consequently, the mature teeth of Xenopus laevis fuse to the jaw bone directly without the mediation of the other structures.
Ultrastructure of differentiated malpighian tubules from cockroach nymphs during the molting cycle
Authors: Schmidt Barbara A.
Published: February 2005

Differentiated Malpighian tubules of Periplaneta americana nymphs consist of four distinct regions. The distal, middle, and proximal regions are similar to the same regions in adult tubules. However, the transparent portion of the middle region was found to have ultrastructural characteristics different from those of the longer opaque segment of the middle region and the two other tubule regions. This newly distinguished region is called the lower middle region. Transitional zones, areas where cells show characteristics of two adjacent regions, are apparent between the distal and middle regions and between the middle and lower middle regions.

The middle region of primary tubules undergoes an increase in autophagic activity and a modification of its basal infoldings and microvilli shortly before each molt. An increase in autophagic activity is also observed in the lower middle region near the time of molting.
The wrist joint of two‐toed sloths and its relevance to brachiating adaptations in the hominoidea
Authors: Mendel Frank C.
Published: February 2005

Two‐toed sloths have evolved a wrist complex that includes the following traits: (1) diminution and distal migration of the pisiform, with a loss of contact with the ulna; (2) reduction of the distal end of the ulna to a styloid process; and (3) extremely reduced contact between the ulna and triquetrum. These traits were proposed by Lewis ('65, '74) to be indicative of brachiating habits and to be a unique adaptation of the Hominoidea. Cartmill and Milton ('77) recently found a similar complex in the wrists of the lorisines. Very similar adaptations of the wrist among the Hominoidea, lorisines, and two‐toed sloths clearly refute contentions of Lewis and strengthen the hypothesis of Cartmill and Milton that the traits common to those animals are due to similar slow, cautious, but acrobatic locomotion.
Annular bands of lymphoid tissue in the intestine of the mallard duck Anas platyrhynchos
Authors: McGarry Ronald C. , Bourns T. K. R.
Published: February 2005

The annular bands were studied by light and scanning electron microscopy in normal and hormonally bursectomized ducks (Anas platyrhynchos). The four annular bands are normal lymphoid structures of 5–10 mm wide and encircle the intestine at regularly spaced position, two on each side of Meckel's diverticulum. The anterior three are well defined, complete rings whereas the posterior‐most encompasses about one half of the gut circumference. The bands are characterized by prominent follicles in the tunica muscularis, submucosa, and lamina propria. In addition, large numbers of diffusely organized lymphocytes fill the lamina propria and villus cores. Each nodule possesses germinal centre activity, as revealed by the characteristic macrophage content seen in 1.0 μm sections.

The bands were present in rudimentary form at hatching. Lymphoid nodules began to develop at day 3 and were morphologically mature at day 98 posthatching. When viewed in the scanning electron microscope, the mucosa of the lymphoid areas was seen to be arranged in tortuous folds, often with irregular fusions. Following hormonal bursectomy, the bands were present, although difficult to detect, and lacked distinct nodules and germinal centres. The mucosal surface still appeared irregularly folded in the SEM, but the folds were more slender with convoluted surfaces.
A scanning electron microscope study of the mesothoracic and metathoracic scolopophorous organs of Lethocerus (Belostomatidae‐heteroptera)
Authors: Anderson Barry R.
Published: February 2005

The presence of scolopophorous organs in aquatic Heteroptera has been reported in a number of species. This study presents a morphological investigation of these sensory structures of Lethocerus (Belostomatidae) as observed with the scanning electron microscope (SEM). Paired mesothoracic and metathoracic organs are present. Externally, each sensory structure consists of a raised sensory membrane. The distal‐most portion consists of thickenings of this sensory membrane (sclerite). The receptor neurons of the mesothoracic organ are of two types—one discolopidial sensillum and 12 monoscolopidial sensilla. The former is attached to the internal wall and distal thickening of the sensory membrane, while the latter are dispersed throughout the interior and attached to the internal wall of the sensory membrane. The structure of the organs suggest that an effective stimulus could be a compression of the membrane. A discussion of possible functions (pressure reception and hearing) is included.
Ultrastructure of the y‐organs of Cancer antennarius in normal and de‐eyestalked crabs
Authors: Hinsch Gertrude W. , Spaziani Eugene , Vensel William H.
Published: February 2005

The paired Y‐organs of crustaceans control the molting process. In males of C. antennarius, these glands are opalescent, lobulated, epithelioid structures embedded in brown fatty tissue. Cells in the periphery extend processes to the connective tissue capsule, an arrangement that suggests increased surface area for metabolic exchange. The processes contain mitochondria and are tipped distally with electron dense material. The cytoplasm, scarce relative to nuclear volume, contains vesicles, polymorphic mitochondria with tubular cristae, and numerous free ribosomes, but little in way of smooth or rough endoplasmic reticulum or Golgi complexes. Progressing from intermolt to the premolt stage, mitochondria, as well as vesicles, and electron‐dense particles in peripheral processes increase somewhat in number. Also, heterochromatin masses concentrate adjacent to the nuclear envelope. Eyestalk removal, which induces premolt stages in some species, did not produce consistent change in Y‐organ substructure in C. antennarius. Although evidence is accumulating that Y‐organs secrete a steroid molting hormone during late intermolt‐premolt, the substructure of the glands exhibits neither (a) striking changes with the molt cycle, nor (b) all the characteristics typical of vertebrate steroid hormone synthesizing glands. Nevertheless, the structural features, respectively, are consistent with biochemical evidence that Y‐organs (a) rapidly take up and convert sterol precursor and secrete a product without its accumulation or change in total sterol pool size, and (b) apparently cannot synthesize the sterol precursor. Y‐organ cytology closely resembles that of some vertebrate steroid hormone secreting glands in which this synthetic capacity is minimal.
Cytodifferentiation and vitellogenesis during oogenesis in arachnida: Cytological studies on developing oocytes of a harvestman
Authors: Kessel R. G. , Beams H. W.
Published: February 2005

Light and electron microscope studies were made on harvestman oocytes during the course of their origin, differentiation, and vitellogenesis. The germ cells appear to originate from the ovarian epithelium. They subsequently migrate to the outer surface of the epithelium, where they remain attached often by means of stalk cells which suspend them in the hemocoel during oogenesis. The “Balbiani bodies,” “yolk nuclei,” or “nuage” constitute a prominent feature of young, previtellogenic oocytes, and take the form of large, but variable sizes of electron‐dense cytoplasmic aggregates with small fibrogranular components. The cytoplasmic aggregates fragment and disperse, and cannot be detected in vitellogenic oocytes. The young oocytes become surrounded by a vitelline envelope that appears to represent a secretory product of the oocyte. The previtellogenic oocytes are impermeable to horseradish peroxidase under both in vivo and in vitro conditions. In addition to mitochondria, dictyosomes, and abundant ribosomes, the ooplasm of the previtellogenic oocyte acquires both vesicular and lamellar forms of the rough‐surfaced endoplasmic reticulum. In many areas, a dense homogeneous product appears within the cisternae of the endoplasmic reticulum and represents nascent yolk protein synthesized by the oocyte during early stages of vitellogenesis. Later in vitellogenesis, the oocyte becomes permeable to horseradish peroxidase under both in vivo and in vitro conditions. This change is associated with a massive process of micropinocytosis which is reflected in the presence of large numbers of vesicles of variable form and structure in the cortical ooplasm. Both spherical and tubular vesicles are present, as are coated and uncoated vesicles. Stages in the fusion of the vesicles with each other and with developing yolk platelets are illustrated. In the harvester oocytes, vitellogenesis is a process that involves both autosynthetic and heterosynthetic mechanisms.
Quantitative studies on the skin of the paired species of lampreys, Lampetra fluviatilis (L.) and Lampetra planeri (BLOCH)
Authors: Lethbridge R. C. , Potter I. C.
Published: February 2005

The number of mucous, club, and granular cells in the epidermis, and the number of rows of subcutaneous adipose cells, as well as the thickness of the epidermis and the dermal collagen layer, have been recorded for the larval and metamorphosing stages of the anadromous parasitic lamprey, Lampetra fluviatilis, and for the larval, metamorphosing, and adult stages of the nonparasitic lamprey, Lampetra planeri.

In L. fluviatilis, the mucous cells predominated in all stages but were more abundant in fully metamorphosed individuals than in larvae. During metamorphosis, the number of granular cells increased continuously, whereas the club cells showed little change. Although lampreys do not feed during metamorphosis, there was an increase in the thickness of the epidermis and in the dermal collagen sheath; the latter increase probably foreshadows the increase in activity by the adults. Simultaneously, there is a reduction in the subcutaneous fat layer, which can be attributed to mobilization of lipid as an energy source.

Changes similar to those just described for L. fluviatilis were also found in metamorphosing L. planeri. However, the pattern altered markedly during adult stages in this nonparasitic species. There were marked declines in the number of cells, in the thickness of the epidermis, in the width of the collagen sheath, and in the quantity of subcutaneous fat.
The morphology of a harpacticoid copepod gut: A review and synthesis
Authors: Sullivan Druscilla Shirley , Bisalputra Thana
Published: February 2005

The digestive tract of a harpacticoid copepod, Tigriopus californicus (Baker), was studied by using techniques of light and electron microscopy. Four cell types could be distinguished: type 1, an embryonic cell which will replace cells worn away or lost during secretion; type 2, a cell which synthesizes and secretes proteins and also plays a role in lipid absorption; and types 3 and 4, two cell types which absorb lipids. From the abundance of each cell type, the length of microvilli, the development of basal plasma membrane (PM), and luminal projections, the following conclusions were made. (1) The midgut caecum absorbs digested nutrients. (2) The anterior midgut absorbs nutrients and more importantly functions in merocrine and exocrine secretion. The presence of concretions in cell types 2 and 3 in the anterior midgut suggests that these tissues contribute in excretion, and in water and/or ion regulation. (3) The posterior midgut absorbs nutrients and contributes some holocrine secretion.
Sense organs on the antennal flagellum of the human louse, Pediculus humanus (Anoplura)
Authors: Slifer Eleanor H. , Sekhon Sant S.
Published: February 2005

Tactile hairs are present on all three subsegments of the antennal flagellum of the human louse. There is, in addition, a single chemoreceptor (tuft organ) on subsegment 2 and 12 or 13 chemoreceptors (one tuft organ, two pore organs and nine or ten pegs) on subsegment 3. The cuticle surrounding the bases of the pegs at the tip of the antenna is unusual in that parts of it are perforated by many fine pores. This cuticle is underlain by a thin layer of dendrites. This region may also have a chemoreceptor function.
Light and electron microscopic studies of crayfish hemocytes
Authors: Sternshein David Jules , Burton Paul R.
Published: February 2005

Using light and electron microscopy, three hemocyte types are described in the hemolymph of the crayfish. The coagulocyte comprises 65% of the total hemocyte number and contains medium‐sized cytoplasmic granules, abundant dilated rough endoplasmic reticulum, and a highly developed Golgi complex. It rapidly undergoes cytolysis in vitro and participates in coagulation by releasing the contents of its granules to the hemolymph. The granulocyte comprises 31% of the total hemocyte number and is capable of phagocytosis. It contains large, irregularly shaped cytoplasmic granules, a moderately developed Golgi complex, and moderate amounts of non‐dilated rough endoplasmic reticulum. During coagulation in vitro, the cell attaches and spreads onto the substratum; this is followed by a slow intracellular granule breakdown and cytolysis. The amebocyte comprises 4% of the total hemocyte number and it is also capable of phagocytosis. It possesses small cytoplasmic granules, many vacuoles, a moderately developed Golgi complex, and large amounts of smooth endoplasmic reticulum. It is distinguished from the other two cell types by being stable and motile in vitro.
Morphometrics of the skeleton of Dermophis mexicanus (Amphibia: Gymnophiona). Part I. The vertebrae, with comparisons to other species
Authors: Wake Marvalee H.
Published: February 2005

Morphometric analysis of vertebral structure in caecilians (Amphibia: Gymnophiona) is presented. Ontogenetic variation in Dermophis mexicanus is analyzed through the 100+ vertebrae composing the column. Vertebral structure in adult D. mexicanus is compared with that in Ichthyophis glutinosus and Typhlonectes compressicauda. Centra of the atlas, second, tenth, 20th, and 50th vertebrae grow at allometrically different rates in D. mexicanus, though the 20th and 50th are not significantly different, Growth appears significantly slower in several dimensions of anterior and posterior vertebrae relative to midtrunk vertebrae in all three species. Mensural patterns throughout the entire column are similar in the terrestrial burrowers D. mexicanus and I. glutinosus; patterns in the aquatic T. compressicauda differ substantially from those of the burrowing species and are strongly influenced by allometry. Of the 112 D. mexicanus examined, 13.4% had vertebral anomalies, usually fusions.
The caudal neurosecretory system of Poecilia sphenops (Poeciliidae)
Authors: Kriebel Richard M.
Published: February 2005

The caudal neurosecretory system of the molly, Poecilia sphenops (Poeciliidae) was studied by light and electron microscopy. In this species the cell bodies form a focal nuclear group in the caudal spinal cord. The neurosecretory cells are in contact with glial elements, axon terminals, and the lumen of the central canal. The axons of the neurosecretory cells form a definitive tract, which leaves the spinal cord proper to penetrate a well defined neurohemal organ, the urophysis. The urophysis contains an abundance of neurosecretory granules within the neurosecretory axonal processes. This study is the first ultrastructural study of the caudal neurosecretory system in this family of fishes, which has been used as a neuroendocrine model. This species acclimates easily to the laboratory aquarium and may be most suitable for further studies on the effects of changes in external salinity on the caudal neurosecretory system.
The origin of protein and fatty yolk in Rana pipiens. V. unusual paracrystalline configurations within the yolk precursor complex
Authors: Ward Robert T.
Published: February 2005

Three unusual highly ordered configurations of yolk protein in yolk precursor bodies are described. These differ from the crystalline structure of the main body of mature yolk platelets. One of these is an aggregation of paired membranes with a spacing of about 100 Å between the members of a pair. The paired membranes of such an aggregation may be straight, parallel, and very close together; they may appear as a tight whorl; or they may display an intermediate random arrangement with varying distances between pairs. Another configuration is a tubule with a diameter of about 450 Å, whose wall appears in cross section to consist of particles measuring 50 × 100 Å. A third configuration is a crystalline array of rows of angular‐shaped particles with a spacing of about 160 Å. It is suggested that these may represent intermediates in the transition of vitellogenin to lipovitellin and phosvitin.
Fine structure of the midgut posterior caeca in the crustacean Orchestia in intermolt: Recognition of two distinct segments
Authors: Graf François , Michaut Philippe
Published: February 2005

This study carried out on the posterior caeca of Orchestia in intermolt by means of light and electron microscopy shows that the diverticula of the midgut consist of two segments which are different from an anatomical point of view. The distal segment is in close relationship to the dorsal blood vessel, whereas the proximal segment, twice as long as the distal one, only touches the haemocoel. The cells of the distal segment are characterized by a brush border, some apical extrusions, a great number of ribosomes, rough endoplasmic reticulum, often associated with the mitochondria, the matrix of which is clear, high activity of the Golgi complexes, and a great development of extracellular channels. All these features indicate an activity in synthesizing proteins and transport. In the proximal segment, the cells are characterized by a striated border, reduced intercellular space, and especially by a great development of the smooth endoplasmic reticulum sometimes associated with mitochondria having a dense matrix. These diverse features indicate absorption ion and water transport. From an ultrastructural point of view, the posterior caeca of Orchestia cannot be considered homologous to the Malpighian tubules. Whereas during molting the posterior caeca of Orchestia are sites of calcium storage, during intermolt they are probably involved in the processes of water and mineral regulation and excretion.
Spermatogenic columns, somatic cells, and the microenvironment of germinal cells in the testes of asteroids
Authors: Walker Charles Wayne
Published: February 2005

Sixty‐seven specimens of the common North Atlantic asteroid, Asterias vulgaris, were collected at seasonal intervals over a 2‐year period and their testes observed with both light and electron microscopy. In the germinal epithelium, a predictable series of interactions between versatile somatic cells and germinal cells is repeated annually in relation to sequential events in spermatogenesis. For example, massive proliferation and differentiation of spermatogenic cells depend on the elaboration of thousands of spermatogenic columns, which are distinct cellular subdivisions of the germinal epithelium. Each fully developed column is composed of at least one somatic cell surrounded by ≈︁ 400 germinal cells. Such columns form only after intensive spermatogonial mitosis begins in the germinal epithelium. Single annual periods of spermatogenic proliferation and differentiation are initiated from 1 to 3 months out of phase in different individuals and overlap incompletely. Therefore, it is possible to observe testes that are entirely in the proliferative phase, entirely in the differentiative phase, or in both phases simultaneously. Detailed ultrastructural observations and preliminary autoradiographic data demonstrate that columns maintain their height for a variable period of time as germinal cells are generated near their bases, pass along their lengths, and differentiate near their tips; therefore, simultaneous proliferation and differentiation of more than one generation of germinal cells occur in the same column. Finally, formation of primary spermatocytes ceases basally, (terminating proliferation), and remaining columns degrade completely as germinal cells composing them differentiate or are phagocytized (terminating differentiation and spermatogenesis); resulting spermatozoa ultimately accumulate in the expandable lumen. It is proposed that spermatogenic columns provide the structural basis for organization of the microenvironment of small groups of spermatogenic cells (≈︁ 400 at a time) during proliferation and differentiation. Preliminary evidence from A. vulgaris and other species also suggests that somatic cells are temporally pluripotent and are variously involved in the formation, structure, and activities of columns, in extensive phagocytosis, and probably in contributing intrinsic (e.g., 1‐methyl adenine and steroids) and mediating extrinsic (e.g., gamete shedding substance and nutrients) microenvironmental factors influential during spermatogenesis in asteroids. The prodigious spermatogenic capabilities of asteroids apparently depend on the generation of spermatogenic columns, on the progressive interaction of germinal and somatic cells before, during, and after columns form, and on the predictable effects of microenvironmental factors received and interpreted at the structural level of the spermatogenic column.
The trunk musculature of caecilians (Amphibia: Gymnophiona)
Authors: Naylor Bruce G. , Nussbaum Ronald A.
Published: February 2005

Descriptions of the trunk musculature of six species representing sex genera and five families of caecilians reveal considerable variation, which may be useful in future systematic studies. The muscle units of the external muscular sheath (M. dorsalis trunci, M. subvertebralis) of caecilians are homologous with, and closely similar in position to, those of salamanders. The major difference in trunk musculature is the presence in caecilians of an additional muscle layer ventral to the M. subvertebralis. This muscle may be a neomorphic derivative from either the M. subvertebralis or the M. transversus. Unlike burrowing reptiles, which have ball‐and‐socket intervertebral joints, caecilians have retained the primitive amphicoelous centrum and compensate for stresses associated with burrowing by the presence of intercentral ligaments and interlocking basapophyses and subcentral keels. Association of Uraeotyphlus with the Ichthyophiidae and the validity of the Rhinatrematidae are supported by data from the trunk musculature.