bluuebunny/crossref_metadata_2025_split huggingface dataset:
Patterns of cells and extracellular material of the sea urchin Lytechinus variegatus (Echinodermata; Echinoidea) embryo, from hatched blastula to late gastrula
Authors: Galileo Deni S. , Morrill John B. 
Published: February 2005

AbstractScanning electron microscopy of six stages of Lytechinus variegatus embryos from hatching through gastrulation reveals changes in the shapes of the ectodermal cells and morphological changes in the extracellular material (ECM) in relation to the locations and migratory activities of mesenchyme cells. The classical optical patterns in the blastular wall (Okazaki patterns) are due to differential orientations of the cells, which bend and extend sheet‐like lamellipodia over adjoining cells toward the eventual location of the primary mesenchymal ring. The blastocoelic surfaces of the blastomeres become covered with a thin basal lamina (BL) composed of fibers and nonfibrous material. During primary mesenchyme cell (PMC) ingression, a web‐like ECM is located in the blastocoel overlying the amassed PMCs. This ECM becomes sparse in migratory mesenchyme blastulae, and is confined to the animal hemisphere. Localized regions of intertwining basal cell processes in the blastular wall are also present during PMC migration. While a distinct BL is present during early and midgastrulation, blastocoelic ECM is absent. Late gastrulae, on the other hand, have an abundance of blastocoelic ECM concentrated near secondary mesenchyme cell protrusive activity. ECM appearing at both the early mesenchyme and late gastrula stages are probably remnants of degraded BL and intercellular matrix preserved by fixation for SEM. Thus, early mesenchyme ECM is formed of BL material whose degradation is necessary for entry of PMCs into the blastocoel. Late gastrula ECM is apparently a degradation product of BL and intercellular material whose destruction is required for fusion of the gut with oral ectoderm in formation of the mouth.
Structure of the radially asymmetrical uncalcified region of the teeth of the red‐backed salamander, Plethodon cinereus (Amphibia, Plethodontidae)
Authors: Moury J. David , Curtis Sherill K. , Pav Denise I. 
Published: February 2005

AbstractThe teeth of the adult plethodontid salamander, Plethodon cinereus, were examined by light and electron microscopy with emphasis on the ringlike zone of uncalcified dentin that divides the calcified portion of each tooth into a proximal pedestal and a distal apex. The uncalcified region displays radial asymmetry, forming an integral part of the posterior wall of the tooth but bulging into the pulp cavity anteriorly, thus forming a hingelike structure. All portions of the dentin, including the uncalcified region, are composed predominantly of collagenous fibers but lack elastin. In scanning electron micrographs of teeth from which the oral mucosa has been removed, the location of the anterior uncalcified hinge is marked externally by a notch‐like articulation of the apex and pedestal. Sites of transition between calcified and uncalcified areas of the dentin show no special modifications in transmission electron micrographs, but collagenous fibers in calcified portions are associated with more electron‐dense amorphous material than are those in the uncalcified region. Odontoblasts associated with the uncalcified region possess ultrastructural features closely resembling those of odontoblasts found in calcified areas. The uncalcified region seems to afford the teeth a certain degree of flexibility, and the asymmetry of the region appears to allow the teeth to flex only in a posterior direction, thus facilitating the entry of living prey but hindering its escape. The uncalcified region also seems to permit the apex of a tooth to break away from its pedestal without damage to underlying bone.
Microcirculation in rat spleen (sinusal), studied by means of corrosion casts, with particular reference to the intermediate pathways
Authors: Schmidt E. E. , MacDonald I. C. , Groom A. C. 
Published: February 2005

AbstractBlood vessels and their connections in rat spleen were traced over considerable distances by scanning electron microscopy of microcorrosion casts prepared by injection of minimal amounts of casting material. The periarterial lymphatic sheath and lymphatic nodules are highly developed, containing an abundance of capillaries which terminate in the marginal sinus (MS) and marginal zone (MZ). The MS, which consists of a series of discontinuous flattened vascular spaces interconnected by short capillaries, shows circumferential filling followed by flow radially outward into the MZ. Contrary to the generally accepted view, many venous sinuses begin as open‐ended tubes at the MS or MZ, allowing free entry of blood into the venous system, thereby bypassing the reticular meshwork of the red pulp. The majority of arterial capillaries terminate in the reticular meshwork (“open” circulation), but evidence for direct connections between capillaries and venous sinuses (“closed” circulation) was also obtained. Casts of the subcapsular region reveal an elaborate system of venous sinuses in fan‐shaped arrays, superimposed on an extensive network of capillaries draining into flattened reticular spaces; such casts provide a three‐dimensional map useful in interpreting light microscopic observations of red cell flow in vivo. Sphincter‐like constrictions in venous sinuses, at points of connection with larger sinuses, indicate that these are possible sites for control of intrasplenic flow distribution.
The development and homology of the chelonian carpus and tarsus
Authors: Burke Ann C. , Alberch Pere 
Published: February 2005

AbstractThe long‐standing controversies involving the number and homologies of the elements of the carpus and tarsus of turtles are reviewed from a developmental perspective. The analysis is based on a detailed description of the chondrogenesis of the carpus and tarsus in the species Chelydra serpentina and Chrysemys picta. The first stage described is the differentiation of a Y‐shaped chondrogenetic condensation involving the humerus (femur)‐radius/ ulna (tibia/fibula). This stage is followed by the early formation of a series of connected condensations off the distal end of the postaxial element (ulna or fibula). This linear array, which we refer to as the primary axis, comprises the ulnare‐distal carpal 4‐metacarpal 4 in the carpus and the fibulare‐distal tarsal 4‐metatarsal 4 in the tarsus. There are two precondensations that branch off the primary axis. The proximal one will soon form the intermedium while the distal one will generate a digital arch that will give rise sequentially to digits 3‐2‐1, in this order. Digit 5 is not part of the digital arch and forms as an independent condensation.We emphasize that chondrogenetic foci often form as “branches” off existing condensations. This well‐defined pattern of connectivity is used to establish unambiguous homologies and allows comparisons with other vertebrates. We conclude that preaxial elements such as the radiale and tibiale are absent in the turtles examined and probably in all turtles. The observed proximal elements that form in the anterior region of the limb and that are often homologized as radiale or tibiale have clear connections to the postaxial elements. For this reason we argue that these elements should be homologized as centralia. Therefore, we find two chondrogenetic condensations in the tarsus and three in the carpus, which we consider centralia. They subsequently fuse with neighboring elements in a complex pattern. We also describe the variable presence of a late‐developing element in the tarsus of Chelydra, which, to our knowledge, has never been described. We propose this element to be an atavistic pretarsale.Comparison of the chondrogenetic pattern in turtles with those described in the literature for other vertebrates indicates that there are two invariant patterns in all tetrapods with the exception of the urodeles. These are (1) the primary axis and (2) the digital arch.
The anatomy and functional morphology of the large hermaphroditic duct of three species of Aplysia, with special reference to the atrial gland
Authors: Painter Sherry D. , Kalman Vivian K. , Nagle Gregg T. , Zuckerman Robin A. , Blankenship James E. 
Published: February 2005

AbstractThe anatomy and functional morphology of the large hermaphroditic duct of three species of gastropod mollusc (Aplysia californica, A. dactylomela, and A. brasiliana) were examined. Each duct is composed of two parallel compartments, the red hemiduct (RHD) and the white hemiduct (WHD), which are distinguishable from the outside of the duct. Four secretory regions, all exocrine in morphology, are recognizable: the RHD secretory epithelium, the atrial gland (or atrial gland‐like epithelium), the WHD secretory epithelium, and the accessory gland of the copulatory duct (AGCD). Of these regions, only the atrial gland (or atrial gland‐like epithelium) contains egg‐laying activity and only the atrial gland (or atrial gland‐like epithelium) is immunocytochemically labeled by serum antibodies generated against low molecular weight. A. californica atrial gland peptides. The RHD is the functional oviduct: the egg cordon passes through a channel lined by the RHD secretory epithelium and bordered by the atrial gland (or atrial gland‐like epithelium); the eggs are separated from both the WHD secretory epithelium and the AGCD by internal folds of the duct. The WHD is the functional copulatory duct: the penis, exogenous sperm, and endogeneous sperm pass directly by the AGCD and in close proximity to the WHD secretory epithelium; they are separated from both the RHD secretory epithelium and the atrial gland (or atrial gland‐like epithelium) by internal folds. The atrial gland (or atrial gland‐like epithelium) is thus not likely to have a prostatic function or to be directly stimulated by the penis during copulation; it may play a role in oviductal function.
Tooth replacement and growth in the young green iguana, Iguana iguana
Authors: Kline L. W. , Cullum D. R. 
Published: February 2005

AbstractA study using eight rapidly growing young green iguanas (Iguana iguana; initial mean weight 68.0 ± 3.8 gm) examined the changes in the wave replacement of teeth, the increased size of the teeth, and the posterior migration of tooth positions over a period of 16 weeks. The teeth increase in width as the lizards grow. The tooth positions shifted posteriorly, providing adequate space for the larger replacement teeth. These observations suggest that the wave replacement of teeth allows for growth of the dentition in length and height adequate to maintain tooth size in proportion to the overall size of the individual.
Relationship of symbiotic microorganisms to metanephridium: Phagoctic activity in the metanephridial epithelium of two species of oligochaeta
Authors: Villaro A. C. , Sesma P. , Alegría D. , Váazquez J. J. , López J. 
Published: February 2005

AbstractIt is known that a number of species in the annelid family Lumbricidae harbor symbiotic microorganisms in the lumen of their nephridia. The purpose of the present paper is the study of the relationship between microbes and epithelial cells lining the metanephridium of two species of Oligochaeta, which show two different patterns of microbial colonization. A new interesting feature, the phagocytosis and intracellular destruction of microorganisms by the nephridial epithelial cells, has been observed in our laboratory for the first time. In Scheroteca savignyi minor, the phagocytic activity takes place in the bladder, the most distal region of the nephridium, next to the nephridiopore, which may prevent the microorganisms from entering the more proximal regions. In Octolasion cyaneum the microbes reach the striated duct, where they live in symbiosis, adhere to the cell's surface, and are engulfed and destroyed by the cells of the middle tubule—the more proximal, neighboring region. The phagocytosis and intracellular degradation of microorganisms probably lead to the massive formation of lamellar bodies, which are observed in these cells and in the neighboring ones.
A microscopic examination of the male turkey proctodeal gland
Authors: Bakst Murray R. , Cecil Helene C. 
Published: February 2005

AbstractThe morphology of the dorsal proctodeal gland of the mature male turkey closely resembles that of the proctodeal gland of the mature female Japanese quail. This exocrine gland is a collection of compound, coiled, tubular units. Diffuse lymphoid tissue and germinal centers are distributed throughout the lamina propria and are closely associated with the surface and glandular epithelia. The morphology and histochemistry of the proctodeal gland mucosa suggest that it may secrete muco‐substance(s) and may have immunogenic capabilities.
Morphogenesis during molting of the setae in the statocyst sensilla of the mysid shrimp Neomysis integer (Leach, 1814) (crustacea, mysidacea)
Authors: Espeel Marc 
Published: February 2005

AbstractThe morphogenesis of the setae in the statocyst sensilla of Neomysis integer was studied. Immediately before ecdysis, a new seta lies inverted between the enveloping cells. All of the nine enveloping cells, except the first one, secrete a well defined part of the new seta. The second, third, fourth, and fifth have a trichogen function; the sixth has a trichogen‐tormogen function; and the seventh, eighth, and ninth enveloping cells have a tormogen function. It could not be established whether the dendritic sheath is replaced at molt. In the second and third enveloping cells, there is a differential secretion of cuticular material forming the wall of the distal part of the seta. As a consequence, this wall is not homogeneous. The possible role of this heterogeneity in the formation of the gutter‐like apical part of the seta is discussed. A mechanism is proposed by which the pore develops at the transition between the midpart and the apical gutter‐like part. Before ecdysis, the distal segments of the sensory cells are still connected with the wall of the old seta in the same way as during intermolt. No degeneration is apparent in the distal segments during preparation for the molt. These morphological findings suggest that sensitivity of the sensilla must be maintained until the moment of the ecdysis.
Morphological evidence for a probable secretory site of the male sex pheromones of Nauphoeta cinerea (blattaria, blaberidae). 2. electron microscope studies
Authors: Menon Maya 
Published: February 2005

AbstractLight and electron microscopy of the glandular epithelium of intersegmental membranes between sternites three and seven and tergites two and eight of various age groups of Nauphoeta cinerea male adults and one age group of female adults discloses differences in the epithelia of the intersternite and intertergite. The intersternal epithelium appears thicker, more glandular, and stratified. Altogether, seven cell types are recognizable, six in the male and two in the female. They are designated as types 1, 2a, 2b, 2c, 3, 4, and 5. Of these, types 1, 2a, 3, and 4 are recognizable on the sternum; types 1, 2b, and 5 on the tergum of the mature male integuments. Types 1 and 2c are found on the sternum of mature female. The cell types undergo morphological differentiation after adult emergence and show different stages of secretory activity. Type 1 are squamous cuticle‐secreting cells; type 2a, 2b, and 2c are columnar‐glandular and contain electron‐transparent secretory vesicles of various sizes, which increase greatly in number and size in the 5‐day‐old adult males when the glands are most active. The vesicular size and number also differ between types 2a, 2b, and 2c cells of the same age group. The vesicles are assumed to be derived from smooth endoplasmic reticulum. The type 2 gland cells are also provided with a secretory end apparatus lined by cuticle and bordered by microvilli through which the secretion is believed to be released by exocytosis. The end apparatus leads into a cuticular ductule that opens to the surface of the cuticle as a cup‐shaped receptacle, which is more conspicuous in the male intersternite. In the active gland cells, the mitochondria near the end apparatus are swollen and vacuolated. Type 3 cells are seen only on the intersternum and are believed to secrete the cuticular ductule that proceeds from the end apparatus. Type 4 cells are also recognizable only on the male intersternum and contain closely packed, electron‐dense bodies, which are most numerous in mature (5‐day‐old) males. Type 5 cells with their dense cytoplasm are located basally in the intertergal epithelium. The functional significance of type 4 and 5 cells in the males and type 2c cells in the female is not clear. On the basis of differences in morphology, pheromone activity, and sexual behavior, it is suggested that the pheromones secreted by the intersternal and intertergal glands in the male are different, the former secreting a seducin that attracts the female to the male and the latter an “aphrodisiac” acting as a contact pheromone important in accomplishing mating.
The effects of sex steroid treatments on sexual differentiation in a unisexual lizard, Cnemidophorus uniparens (Teiidae)
Authors: Billy Allen J. , Crews David 
Published: February 2005

AbstractCnemidophorus uniparens is a parthenogenetic unisexual species of lizard in which each individual develops as a female, making it a unique animal model for the study of sexual differentiation. In one study, administration of exogenous testosterone before and/or after hatching influenced the development of the gonads, the accessory reproductive ducts, the renal sex segment of the mesonephric kidney, and the femoral glands, a secondary sex character. Testosterone treatment also affected the cross‐sectional area of the gonad and the proportions of cortical and medullary tissues present in the developing gonad. The oviducts and femoral glands of testosterone‐treated individuals were hypertrophied; the collecting tubules of the kidney of these animals contained granules, an androgen‐dependent, sexually dimorphic character in squamate reptiles. In another study, testosterone, dihydrotestosterone, or estradiol were administered to C. uniparens embryos. No treatment effects on gonadal development were detected on the day of hatching. However, estradiol, but not testosterone and dihydrotestosterone, stimulated development of the oviducts. Taken together these studies suggest that androgen aromatization may play a role in sexual differentiation in lizards.
Proportions of mammalian‐type and reptilian‐type nephrons in the kidneys of two passerine birds
Authors: Goldstein David L. , Braun Eldon J. 
Published: February 2005

AbstractWe compared the proportions of mammalian‐type and reptilian‐type nephrons in the kidneys of two species of passerine birds. The desert house sparrow (Passer domesticus) is relatively well adapted for water conservation, whereas the white‐crowned sparrow (Zonotrichia leucophrys) is more mesic adapted. The two species do not differ in body mass, but the kidneys of P. domesticus are significantly smaller than those of Z. leucophrys. Associated with its smaller size, the house sparrow kidney has significantly fewer glomeruli (35,700 per kidney) than does the white‐crowned sparrow kidney (53,000 per kidney). The medullary cones, which contain the loops of Henle of the mammalian‐type nephrons, are significantly longer in house sparrows than in white‐crowned sparrows (2.2 vs. 1.9 mm). The number of medullary cones, the number of nephrons per medullary cone, and, hence, the number of mammalian‐type nephrons do not differ between the two species. The smaller number of nephrons in the kidney of the house sparrow therefore represents a smaller number of reptilian‐type nephrons. Desert house sparrows have 18% mammalian‐type nephrons, whereas white‐crowned sparrows have 10% mammaliantype nephrons. The relative reduction of reptilian‐type nephrons in P. domesticus may reduce the flow of dilute urine through the collecting ducts, thereby permitting a greater concentration gradient to be established along the length of the medullary cones.
Comparative features of the surface morphology of the basilar papilla in five families of salamanders (amphibia; caudata)
Authors: White James S. 
Published: February 2005

AbstractThe surface morphology of the basilar recess and papilla was examined in 14 species of newts and salamanders selected from the five families of urodeles (Ambystomatidae, Salamandridae, Hynobiidae, Cryptobranchidae, and Amphiumidae) known to have this end‐organ. In this sampling, the general organization of basilar structures is essentially similar across species investigated. The recess forms a tubular diverticulum of the proximal part of the lagena. One wall of the recess is associated with a diverticulum of the intracapsular periotic sac, and an adjacent wall is occupied by the basilar papilla. The papilla contained from as few as five hair cells in specimens of Taricha torosa to over 200 hair cells in Cryptobranchus allegheniensis. In most species, the papilla showed a morphological continuum between tall centrally or distally placed ciliary bundles and short ciliary bundles near the papillar margins. In certain species examined, tall bundles had kinocilia with swellings near their tips. Most forms showed a tendency to have groups of ciliary bundles morphologically polarized either toward or away from the saccule. In Cryptobranchus and Dicamptodon, many bundles had a random orientation. The gross and fine structural features of the basilar complex are compared in urodeles and anurans, and “generalized” features for the amphibian basilar complex are suggested. The basilar complex of Cryptobranchus is interpreted as being most generalized, representing a structural form from which most features of the basilar complex in other urodeles and anurans can be derived.
Functional morphology of the M. Gastrocnemius medialis of the rat during growth
Authors: Woittiez R. D. , Heerkens Y. F. , Huijing P. A. , Rijnsburger W. H. , Rozendal R. H. 
Published: February 2005

AbstractLength‐force relations, both active and passive, and twitch contraction characteristics were quantified for left medial gastrocnemius muscles of four young, four adult, and four old male Wistar rats. Muscle and bundle optimum length and muscle weight were also determined and subsequently used for calculation of a number of morphological characteristics of the muscles. Fiber optimum length was derived from muscle bundle optimum length. Generally, physiological characteristics remained constant during growth. There was no change either in active tension at muscle optimum length or in active working range relative to fiber optimum length, relative passive fiber stiffness, active force relative to passive force at optimum length, twitch contraction time and twitch half relaxation time at optimum length. A number of morphological changes, however, did take place in the medial gastrocnemius muscle during growth. Fiber optimum length increased but only by about 2 mm from youth to old age, whereas muscle optimum length increased by approximately 14 mm, presumably owing to extensive hypertrophy of the muscle fibers during growth. The priority for force of the medial gastrocnemius muscle (defined as the quotient of physiological cross‐sectional area of a muscle and the cubed root of its volume, a measure independent of architecture and dimensions of muscles) increased during growth. This increase indicates that during growth the muscle shifts relatively more towards force generation than towards excursion generation. These findings are discussed in view of existing scaling theories.