bluuebunny/crossref_metadata_2025_split huggingface dataset:
An ultrastructural study of the melanophages in the cerebrospinal fluid of the tadpoles of Xenopus
Authors: Kordylewski Leszek 
Published: February 2005

AbstractMelanin deposits in the brain ventricles of Xenopus tadpoles were studied with light and electron microscopy (TEM and SEM). They appeared to be aggregations of melanophages which accumulated free pigment granules excreted by ependymal cells into the cerebrospinal fluid. Whereas the meningeal melanophores contained oval melanosomes of various sizes, the melanosomes in the scavenger cells were all spherical, large (0.6–1.1 μm) and fairly uniform in size. Moreover, they were arranged in spherical groups which were never seen in the cytoplasm of the melanophores. The melanosomes within the cells were identical to the free melanosomes found in the cerebrospinal fluid and those which occurred within the ependymal cells in the young larva, suggesting a common origin from the egg cytoplasm.The number of the melanosomes in the melanophages increased with age. Fine cytoplasmic projections were involved in catching and engulfing the melanosomes. Some other features of the cytoplasm, e.g., large deposits of cell detritus, also indicated that the cells were macrophages. In the later stages, (48, 49) no projections were observed, but the cells were totally filled with melanosomes.
Ultrastructural aspects of dental tissues and their behavior in xenoplastic association (lizard quail)
Authors: Lemus D. , Fuenzalida M. , Illanes J. , De La Vega Y. Paz 
Published: February 2005

AbstractUltrastructural characteristics of tooth buds of the polyphyodont adult lizards Liolaemus tenuis and Liolaemus gravenhorsti have been elucidated. Xenoplastic combinations of lizard whole tooth buds and neural crest cells from embryos of the quail Coturnix coturnix japónica have been cultured in vitro. Mesenchymal cells (preodontoblasts) of lizard teeth early develop filopodia that contact the basal lamina. Fragments of quail neural crest isolated by dissection were recombined with isolated lizard tooth buds and cultured for 84 hours in dishes kept in an incubator at 37.8°C in air. Some identifiable quail cells in these recombinants developed a cytoplasmic extension like that of an odontoblastic process. These results suggest that lizard tooth rudiments already determined for tooth development produce some non‐species specific transmissible constituents which are capable of inducing quail cranial neural crest cells to express certain dental characteristics (odontoblastogenesis) not expressed in their normal development in vivo.
Permeable sites in the firefly lantern tracheal system: Use of osmium tetroxide vapor as a tracer
Authors: Ghiradella H. 
Published: February 2005

AbstractFlashing fireflies were permitted to breathe osmium tetroxide vapor, after which the lanterns were removed and the sites of absorption of the osmium into the tissues were detected in two ways: (1) by sonication to remove soft tissues, that is, those that had not been fixed by the osmium gas, and (2) by intensification with thiocarbohydrazide and silver nitrate, in a modification of the osmium–thiocarbohydrazide–osmium (OTO) stain technique. The results of both procedures indicate that the gas first enters into the tissues at the level of the tracheoles. These findings may be interpreted as underscoring the importance of the tracheolar cell and the tracheal end organ in the control of oxygen entry into the lantern tissues, and the implications of the results in the oxygen regulation theory of flash control are discussed.
Anatomy of external structure and musculature of thoraces in the larva of the lepidopteran Pieris rapae crucivora
Authors: Tsujimura Hidenobu 
Published: February 2005

AbstractIn Pieris rapae the external structure of meso‐ and metathoraces includes intersegmental folds as well as 4 transverse shallow grooves on the dorsal side and 2 on the ventral side in addition to several leg segments. The musculature of both segments is very similar, but has some segment‐specificity. Sixty‐seven muscle are common to both hemi‐mesothorax and hemimetathorax. Four are specific for the mesothorax and 3 for the metathorax. Moreover, thickness and number of subdivisions of some common muscles are specific for one segment. Attachments areas of all muscles are clearly indicated on the pattern of cuticular grooves. They have a tendency to pile up or line up to form various sizes of united attachment sites, most of which are located on or near the cuticular groove. On the other hand all grooves have some muscle attachment sites. Thus, attachments of larval muscles may relate to formation of the grooves. Comparison of the musculature with that previously reported for some lepidopteran larvae shows a major common basic plan and minor interspecific variation. Its attachment sites allow the role of each muscle to be inferred for body contraction, bending, and twisting, and for leg direction and flexion.
Changes in ovarian ultrastructure and ecdysteroid titer during the aging process of female Xyleborus ferrugineus (Coleoptera: Scolytidae)
Authors: Norris D. M. , Chu H. M. , Rao K. D. P. 
Published: February 2005

AbstractStriking ultrastructural and hormonal parameters of premature menopause and aging are reported in female Xyleborus ferrugineus fed cholesterol, rather than 7‐dehydrocholesterol, as a sole dietary sterol. The titer of free ecdysteroids in such 63‐day‐old females remained abnormally elevated through the period of the ovarian cycle. A similar plateauing of such elevated titer also occurred in 147‐day‐old, irregularly cycling females fed only cholesterol as the dietary sterol. These hormonal changes in menopausing X. ferrugineus females seem especially analogous to the maintenance of an elevated concentration of 17‐β‐estradiol through the estrous, as well as the proestrous, ovary of aged irregularly cycling rats. The highly abnormal ultrastructure of ovaries of X. ferrugineus females aged 216 days on a diet containing cholesterol as the sole sterol seems quite analogous to that of the nonovulatory follicles in older, irregularly cycling rats. Our new findings involving aging X. ferrugineus females indicate further the usefulness of an insect model to study aging processes.
Spatial organization in the saccule and lagena of a teleost: Hair cell pattern and innervation
Authors: Saidel William M. , Popper Arthur N. 
Published: February 2005

AbstractThe relationship between the hair cell orientation pattern and innervation in the saccule and lagena of the teleost Helostoma temmincki (the kissing gourami) was investigated with scanning electron microscopy and the Winkelmann‐Schmitt silver impregnation technique. The hair cell pattern in the saccule consists of four orthogonally oriented groups. The anterior two groups are oriented along the animal's rostrocaudal axis, and the posterior two are oriented along its dorsoventral axis. The pattern of hair cell orientations in the lagena is a typical bidirectional one. Two divisions of the eighth nerve innervate the saccule. The anterior division innervates the horizontally oriented hair cell groups, and the posterior division innervates the dorsoventrally oriented groups. A single nerve innervates the lagena, with the majority of fibers innervating one or the other of the two lagenar hair cell groups. The segregated pattern of innervation according to hair cell orientation groups in the saccule was confirmed in other species. Individual types of axonal terminations appear to innervate hair cells of specific ciliary bundle types.
Arterio‐Venous anastomoses in the gills of australian short‐finned eel, Anguilla australis
Authors: Donald J. A. , Ellis A. G. 
Published: February 2005

AbstractScanning electron microscopical examination of corrosion casts and critical point dried tissue of the gills of Anguilla australis showed that arterio‐venous anastomoses were present in both the afferent and efferent components of the gill vasculature. A morphometric distinction was made between anastomoses and capillaries within the gills. The origins of arteriovenous anastomoses from the filament arteries were bordered by specialized endothelial cells. The possible function of arterio‐venous anastomoses and the specialized endothelial cells is discussed.
Accuracy of bristle placement on a leg segment in Drosophila melanogaster
Authors: Held Lewis I. , Pham Tu T. 
Published: February 2005

AbstractBristle positions in two rows of bristles on the basitarsus of the second leg of the fruitfly Drosophila melanogaster were analyzed in order to determine the accuracy of bristle placement within these rows. Within each row the positions of the two terminal bristles were found to be approximately equally variable, and positional variability was found to increase toward the middle of each row. Rows having fewer bristles manifested more positional variability in their midsection. These results are interpreted in terms of a possible bristle spacing mechanism involving repulsive forces between mobile bristle cells.
Circulatory pathways in the sinusal spleen of the dog, studied by scanning electron microscopy of microcorrosion casts
Authors: Schmidt E. E. , Macdonald I. C. , Groom A. C. 
Published: February 2005

AbstractScanning electron microscopy of microcorrosion casts was used to visualize circulatory pathways in the sinusal spleen of dog. The examination of contracted versus dilated organs and variations of the volume of material injected gave an indication of flow dynamics. Minimal injections of material into contracted spleens produced filling of mainly the fastest routes for flow, whereas injections into dilated spleens primarily filled slower routes. This procedure yielded a more complete, three‐dimensional picture of the arterial, intermediate, and venous pathways as a whole, and of the relative amounts of flow through different arterial routes. Evidence of flow from capillary lumina out into ellipsoid sheaths was plentiful in casts from dilated spleens, but rare in casts from contracted organs. The pattern of flow within and out of the marginal sinus has been elucidated: A circumferential filling occurs first, followed by a flow that radiates outward into the marginal zone and red pulp. Venous sinuses filled via two routes in addition to the generally accepted path from the reticular meshwork via fenestrations in sinus walls. First, many venous sinuses extending out from the marginal sinus and surrounding marginal zone originated as open‐ended tubes continuous with the reticular spaces of the marginal sinus or marginal zone. Second, direct connections of arterial capillaries with venous sinuses in the red pulp were found. Evidence indicating that some mechanism is controlling the flow via these routes is discussed. The strikingly different arrangement of venous sinuses in the subcapsular region is demonstrated.
The intermediate circulation in the nonsinusal spleen of the cat, studied by scanning electron microscopy of microcorrosion casts
Authors: Schmidt E. E. , Macdonald I. C. , Groom A. C. 
Published: February 2005

AbstractScanning electron microscopy of microcorrosion casts was used to visualize circulatory pathways of the intermediate circulation in nonsinusal spleen of cat. The marginal sinus (MS) around lymphatic nodules is a distinct vascular space which fills preferentially before the filling of the marginal zone (MZ) and surrounding red pulp occurs. The MS, which has a plentiful vascular supply, does not usually enclose the nodule completely. From the MS, flow occurs radially outwards into the MZ. Corrosion casts and histological sections both showed that a diversity of forms of the MZ exists: The thickness of MZ and the arrangement of its reticulum vary among nodules and between different areas of the same nodule, from a complete absence to a region of up to 50 μn width.No direct arteriovenous connections were found (in contrast to dog spleen: Schmidt et al., '83b). Aside from capillary endings in the MS and MZ, all arterial capillaries terminate in the reticular spaces of the red pulp, i.e., the circulation appears to be entirely “open.” From each capillary termination a great variety of flow pathways through the reticular meshwork to the pulp venules is available; some of these routes are quite long but others may involve distances as short as 15–25 μm. Evidence of flow into ellipsoid sheaths was abundant in casts from dilated spleens, but scarce in contracted spleens. In contrast to the extensive system of interconnected venous sinuses in dog spleen, the pulp venules found in cat spleen are nonanastomosing, shorter, and much smaller in caliber, and all receive flow freely from the reticular mesh‐work via open ends and fenestrations in their walls.
An ultrastructural study of oocyte growth within the endoderm and entry into the mesoglea in Actinia fragacea (Cnidaria, anthozoa)
Authors: Larkman Alan U. 
Published: February 2005

AbstractSea anemone gametes arise in the endoderm but migrate into the mesoglea at an early stage. In order to observe this process, large individuals of Actinia fragacea were collected from the same intertidal location at regular intervals over a 2‐year period, and their gonads were examined by light and electron microscopy.The cellular origin of the oocytes is unclear, but the smallest recognizable oocytes are rounded cells, 6‐8 μm in diameter, with relatively large nuclei which may contain synaptinemalcomplexes. Their cytoplasm contains numerous ribosomes, a flagellar basal‐body‐rootlet complex, and distinctive dense structures also present in male germ cells but not found in anemone nonger‐ minal cells. During the endodermal phase of growth, the density of the oocyte nucleus increases, a single nucleolus becomes prominent, and mitochondria and glycogen accumulate in the cytoplasm. Most oocytes, but not all, only begin major vitellogenesis after entry into the mesoglea. Most oocytes enter the mesoglea before they attain a diameter of 25 μm.The oocytes migrate toward and enter the mesoglea by a process resembling amoeboid movement. During entry, the oocytes are constricted into a characteristic “hourglass” shape and become covered by a basal lamina continuous with that of the gonad epithelium. The last part of the oocyte to enter the mesoglea forms an intimate relationship with the surrounding endodermal cells, which is maintained after entry is complete, and is thought to be important in the establishment of the trophonema.
Histochemical observations on the pyloric caeca of Asterias rubens (Echinodermata, asteroidea) in relation to the reproductive cycle
Authors: Van Der Plas A. J. , Voogt P. A. 
Published: February 2005

AbstractThe pyloric caeca of the starfish Asterias rubens were investigated histochemically during the reproductive cycle. The median duct and the side lobes reacted differently. The median duct reacted positively for acid phosphatases and glucose‐6‐phosphate dehydrogenase, whereas the side lobes reacted positively for alkaline phosphatases, neutral lipids, and fatty acids. In the transition zone between the median duct and the side lobes, the reaction for alkaline phosphatases and neutral lipids increased toward the side lobes. The function of the enzymes and the histochemical results are discussed in relation to the function of the pyloric caeca and to the reproductive cycle.
The development of the hexagonally structured egg envelope of the C‐O sole (Pleuronichthys coenosus)
Authors: Stehr Carla M. , Hawkes Joyce W. 
Published: February 2005

AbstractThe surface of a mature, pelagic C‐O sole egg is composed of polygonal chambers having four to eight sides, most of which are hexagonally shaped. This honeycomb pattern initially appears on primary oocytes as a thin layer of compact, electron‐dense material. Discrete thickenings begin to develop on the envelope of perinuclear stage oocytes. The thickenings lengthen and thin to form the hexagonal walls of the envelope in oocytes undergoing yolk vesicle formation. The walls of each hexagonal chamber occur in an area corresponding to the lateral margins of the adjacent follicle cell, suggesting that the hexagonal walls are produced by the follicle cells. The hexagonal layer is nearly complete at the beginning of vitellogenesis, and as vitellogenesis continues, a striated envelope layer composed of fibrillar lamellae develops between the oocyte and the hexagonal layer. The striated layer appears to be secreted by the oocyte. After vitellogenesis is completed, oocytes are ovulated and double in size during a period of maturation. Concurrently, the striated primary envelope stretches and thins into eight to nine horizontal lamellae. On the mature egg surface, the polygonal chambers are about 24–31 μm in diameter. Within each chamber there is a subpattern of polygonal areas; each polygon is 1.5–2.0 μm in diameter, and circumscribes a pore canal opening. This exceptional envelope may furnish the egg with some degree of protection, resiliency, and buoyancy, but its specific functions are not known.
The blood vascular system in the head of the herring gull (Larus argentatus)
Authors: Midtgård Uffe 
Published: February 2005

AbstractThe structure and development of the blood vascular system in the head of the herring gull (Larus argentatus) have been studied using injection techniques and histological sections. Three different but interconnected divisions of the arterial system are recognized in the adult: the cerebral carotid artery system, the external ophthalmic artery system, and the external carotid artery system. Embryologically, the arterial system is characterized by changes in the relative development of these three divisions; the cerebral carotid system being the most prominent in the first half of the embryonic period. The venous system is divided into two parts, the rostral cephalic system and the caudal cephalic system, which drain separate regions of the head. The Rete ophthalmicum, which is an arteriovenous network associated with the external ophthalmic artery system, can be identified from the fifth day of incubation, and its development appears to be coupled with changes in the arterial supply to the eye. The possibility of a homology between the Rete ophthalmicum of birds and the Rete caroticum of mammals is briefly discussed.
Fusion of ancestrulae germinated from statoblasts in plumatellid freshwater bryozoans
Authors: Mukai Hideo , Tsuchiya Masashi , Kimoto Kazuki 
Published: February 2005

AbstractUpon germination of a statoblast, the shell is split into two valves; a mucous pad which represents the basal portion of the body wall of the incipient zooid or ancestrula then appears from between the valves; lastly, a tiny polypide evaginates at the opposite site. When two or more contiguously located statoblasts (floatoblasts or sessoblasts) of the same species germinate simultaneously, their mucous pads often come into contact with each other. The walls of the mucous pads then disappear in the contact areas, thus uniting the coeloms of the ancestrulae. This type of fusion between mucous pads of statoblast‐derived ancestrulae was ascertained in Plumatella emarginata, P. repens, P. casmiana, and Hyalinella punctata. The fusion is clearly species specific, and shows no clone specificity or allogeneic recognition. The fusibility test reported here seems to be a useful method for the examination of conspecificity in plumatellid bryozoans.
Effects of prolonged antitubulin culture on annulate lamellae in mouse α L929 fibroblasts
Authors: Kessel Richard G. , Katow Hideki 
Published: February 2005

AbstractThe fine structure of α L929 fibroblasts cultured in colchicine or vinblastine sulfate for periods as long as 48 hr was compared to control cells not exposed to antitubulins. In response to prolonged antitubulin culture, several changes in cell ultrastructure were noted: (1) Control fibroblasts contain cytoplasmic annulate lamellae (AL), but (2) prolonged exposure to either vinblastine sulfate or colchicine results in enhanced development of AL. (3) Single pore complexes are present in the rough‐surfaced endoplasmic reticulum (rER) in both control and antitubulin‐treated cells, but stacked porous cytomembranes also occur under both conditions. (4) Polyribosomes often are closely associated or continuous with the pore complexes. (5) Many antitubulin‐treated cells become multinucleate. Some nuclei in both control and antitubulin‐treated cells contain large and multiple nucleoli. (6) The large and multiple nucleoli are either attached directly to the inner membrane of the nuclear envelope or to infoldings of the nuclear envelope. (7) Antitubulin‐treated cells, after 48‐hr exposure, appear also to contain enhanced quantities of smooth‐surfaced endoplasmic reticulum (sER) and cytoplasmic filaments (and in some cells, lysosomes and rER as well) when compared to untreated cells. (8) In both control and colchicine‐treated cells, AL can exhibit continuity with either rER or sER. Further, (9) all three membrane systems may at times be continuous, but the quantity of these membranes appears to be greater in colchicine‐treated cells than in control cells. The results are discussed with respect to possible functional significance.
Intercellular bridges in ovaries of the newborn gerbil
Authors: McReynolds H. D. , Blanchet L. J. , Bowman D. C. , Hakim A. A. , Kiely M. L. 
Published: February 2005

AbstractThis study describes intercellular bridges in the ovaries of neonatal gerbils. Electron microscopy has revealed the presence of true intercellular bridges, connecting oogonia or oocytes, in ovaries of newborn gerbils. The cytoplasm of the intercellular channels is similar to that of the connected cells, with mitochondria, smooth and rough endoplasmic reticulum, and free ribosomes present. Lysosomes are also occasionally present in the intercellular bridges and they may be involved in early waves of oocyte atresia. An electrondense substance, 350–500 Å thick, is located immediately beneath the unit membrane of the intercellular bridges. Accumulation of electron‐dense material increases the thickness of the walls of the intercellular bridges, supporting and maintaining the patency of the channels. It is suggested that the intercellular channels probably allow the interchange of nutrients, organelles, and possibly regulatory materials as well.