bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrastructure of sperm development in the plant‐parasitic nematode Xiphinema theresiae
Authors: Kruger Johan C. De W. 
Published: February 2005

AbstractSpermatogenesis and sperm ultrastructure were studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) in the longidorid Xiphinema theresiae. All germ cell stages, except spermatogonia, are present in the testes of young adult males. The nonflagellated, slightly elongated sperm displays little intraspecific variation and, although never polarized into a head and tail region, has a remarkably precise form, with a high degree of internal organization. Incipient fingerlike pseudopodia appear in the young spermatid and increase to such an extent that the adult sperm has a conspicuous “woolly” appearance. Microfilament bundles encircle the perinuclear mitochondria in the spermatid, and seem to be closely associated with the evaginated plasma membrane, especially in the spermatozoon. A large nucleus with nuclear envelope is prominent in the spermatocyte, but the envelope is absent in the young spermatid. Mitochondria are present in all germ cell stages and undergo certain morphological changes (e.g., in size and number, presence or absence of cristae), as well as changes in intracellular movements during spermatogenesis. Membranous organelles are prominent in the spermatocyte, but disappear in the older spermatid. Annulate lamellae and a residual body (i.e., cytophore) are conspicuous in the spermatocyte and spermatid, respectively; the spermatozoon clearly lacks a refringent body (i.e., acrosome).
Kinematics of prey capture and chewing in the lizard Agama agama (squamata: Agamidae)
Authors: Kraklau David M. 
Published: February 2005

AbstractHigh speed video recordings (200 fields per second) of prey capture and food processing in Agama agama permit the identification of strikes, chews and transport movements. Ten variables from strike movements and seven variables from chewing sequences are digitized; transport movements are inspected only. Univariate and multivariate statistical analyses disclose significant interindividual differences for three variables (maximum gape distance, maximum head angle, and maximum throat distance); but neither these nor principal components analysis show differences between strikes and chews for any of the gape change and hyoid depression variables. However, strikes and chews obviously differ in tongue protrusion and body movements. Chewing may be divided into four stages, comparable to those of transport cycles of other lizards and the generalized tetrapod model. Transport differs from chewing by having a shorter power stroke and relatively more cranial and less jaw movement. The kinematics of feeding in Agama agama are compared with those of other lizards studied previously.
Brain‐capillary architecture of the newt, Triturus cristatus carnifex (Caudata: Salamandridae): Scanning electron‐microscopical study of vascular corrosion casts
Authors: Lazzari Maurizio , Ciani Franco , Franceschini Valeria 
Published: February 2005

AbstractThe brain‐microvascular architecture of the newt (Triturus cristatus carnifex) was studied by scanning electron‐microscopical examination of microvascular corrosion casts. It is characterized at the leptomeningeal level by a superficial network of single vessels that leave the meningeal sheath to form hairpin‐shaped capillary loops. These loops penetrate the nervous parenchyma to varying depths and are variously bent, inclined, and twisted. Each hairpin‐like loop consists of descending and ascending limbs connected by a distal U‐shaped segment. The limbs are of equal diameter and lack physical differentiation. Some loops branch in a secondary loop, but there are no intraparenchymal connections with analogous surrounding structures. On vascular casts we observed detailed imprints of endothelial cell nuclei. This microvascular architecture is present in the whole brain except in leptomeninx and choroidal plexuses. The vascular pattern of T. cristatus carnifex resembles that of apodans. However, it differs from the anuran condition, which is characterized by a three‐dimensional parenchymal network and from that of Ambystoma mexicanum which displays an intermediate condition between a single‐capillary network and a capillary‐loop model. At the level of paired capillaries, a counter‐current exchange system may occur between the two limbs of the same loop, an arrangement that could promote uniformity of extracellular fluid composition in parenchyma.
Cranial ontogeny in the direct‐developing frog, Eleutherodactylus coqui (anura: Leptodactylidae), analyzed using whole‐mount immunohistochemistry
Authors: Hanken James , Klymkowsky Michael W. , Summers Cliff H. , Seufert Daniel W. , Ingebrigtsen Nicole 
Published: February 2005

AbstractDirect development in amphibians is an evolutionarily derived life‐history mode that involves the loss of the free‐living, aquatic larval stage. We examined embryos of the direct‐developing anuran Eleutherodactylus coqui (Leptodactylidae) to evaluate how the biphasic pattern of cranial ontogeny of metamorphosing species has been modified in the evolution of direct development in this lineage. We employed whole‐mount immunohistochemistry using a monoclonal antibody against the extracellular matrix component Type II collagen, which allows visualization of the morphology of cartilages earlier and more effectively than traditional histological procedures; these latter procedures were also used where appropriate. This represents the first time that initial chondrogenic stages of cranial development of any vertebrate have been depicted in whole‐mounts.Many cranial cartilages typical of larval anurans, e.g., suprarostrals, cornua trabeculae, never form in Eleutherodactylus coqui. Consequently, many regions of the skull assume an adult, or postmetamorphic, morphology from the inception of their development. Other components, e.g., the lower jaw, jaw suspensorium, and the hyobranchial skeleton, initially assume a mid‐metamorphic configuration, which is subsequently remodeled before hatching. Thirteen of the adult complement of 17 bones form in the embryo, beginning with two bones of the jaw and jaw suspensorium, the angulosplenial and squamosal. Precocious ossification of these and other jaw elements is an evolutionarily derived feature not found in metamorphosing anurans, but shared with some direct‐developing caecilians. Thus, in Eleutherodactylus cranial development involves both recapitulation and repatterning of the ancestral metamorphic ontogeny. These modifications, however, are not associated with any fundamental change in adult morphology and cannot at this time be causally linked to the evolutionary success of this extraordinarily speciose genus.
Histology, histochemistry, and ultrastructure of the harderian gland of the snake Coluber viridiflavus
Authors: Minucci Sergio , Baccari Gabriella Chieffi , di Matteo Loredana 
Published: February 2005

AbstractAnalyses of the histology, histochemistry, and ultrastructre of the Harderian gland of Coluber viridiflavus prove the gland to be compound acinar and to produce a seromucous secretion. Acinar cells (type I) contain secretory granules that are composite, consisting ultrastructurally of three distinct parts that are sharply separated. They are similar to the “special secretory granules” described in the cells of the Harderian gland of the lizard Podarcis s. sicula. Some acini of the most anterior and posterior parts of the gland are mucous. Acinar cells (type II) of this type contain secretory granules that are Alcian blue/PAS positve. At the ultrastructural level, they appear homogeneous and of low density, characteristic of mucous secretions. These mucus‐secreting anterior and posterior parts of the Harderian gland may by considered as regions of intial differentiation of the anterior and posterior lacrimal galnds.
Morphology of the tooth of the American alligator (Alligator mississippiensis): The fine structure and elemental analysis of the cementum
Authors: Shimada K. , Sato I. , Moriyama H. 
Published: February 2005

AbstractThe fine structure and the concentration of trace elements in the cementum layer in functional teeth of subadult alligators (ca. 120 cm to 160 cm total length) was studied by using scanning electron microscopy (SEM), microradiography, and electron microprobe analysis (EMPA). The cementum layer was hypertrophic and consisted of two layers: the fibrous layer and the calcified layer. The two layers undergo developmental changes as a result of resorption and replacement. During the tooth replacement in the American alligator, trace elements decreased at the base of the dentine layer; the resorption of the alveolar bone occurred simultaneously at the tooth socket. We concluded that the resorption of the cementum in the alligator provided a useful indication of the mechanism of tooth replacement in crocodilian.
Fine structure of the dorsal lingual epithelium of the little tern, Sterna albifrons pallas (Aves, Lari)
Authors: Iwasaki Shin‐Ichi 
Published: February 2005

AbstractThe dorsal surface of the tongue of the little tern, Sterna albifrons, has a distinctive anterior region for five‐sixths of its length and a terminal posterior region. The anterior region observed by scanning electron microscopy is distinguished along its forward half by a median line from which median papillae protrude. The hind half of the anterior region has a median sulcus without papillae. The deciduous epithelium on both sides of the median line and sulcus bears scattered epithelial protrusions. The posterior lingual region has neither median papillae nor deciduous epithelium. So‐called giant conical papillae are located in a transverse row between anterior and posterior regions. Delicate microridges adorn the surfaces of all outer epithelial cells in both regions.Examination of the dorsal lingual epithelium by light and electron microscopy provides histologic and cytologic criteria for distinguishing anterior and posterior regions. Basal cells are nearly alike throughout the dorsal epithelium. Intermediate layer cells of the anterior region contain numerous tonofibrils in electron‐dense bundles composed of 10 nm tonofilaments. The outer layer is composed of electron‐dense, well‐keratinized cells, and electron‐lucent epithelial protrusions are present on the expose surface of the outermost cells. Median papillae are composed of typical keratinized cells, which are nearly filled with keratin filaments. Intermediate layer cells in the posterior region of the tongue are nearly filled with unbundled tonofilaments. There is only a very thin outer keratinized layer in this region.
Functional morphology of the endomysium in series fibered muscles
Authors: Trotter J. A. , Purslow P. P. 
Published: February 2005

AbstractMany skeletal muscles, including the feline biceps femoris, are composed of short, tapered myofibers arranged in an overlapping longitudinal series. The endomysium of such muscles transfers tension between overlapping myofibers, and is thus an elastic element in series with them. The endomysium of the cat biceps femoris contains curvilinear collagen fibrils in an approximately isotropic (random) array. The collagen fibrils undergo only a modest reorientation as the myofibers shorten or lengthen within the physiological range. A geometrical model predicts no change in the thickness of the endomysium on changing muscle fiber length and quantifies the expected collagen fibril reorientation in the endomysium as a function of muscle extension. It is also demonstrated that a high proportion of the collagen fibrils will be curvilinear at all sarcomere lengths. The organization of endomysial collagen is appropriate for the transfer of loads between myofibers by means of shear. © 1992 Wiley‐Liss, Inc.
Ubiquitous perivenous smooth muscle cords in viscera of the teleost Rachycentron canadum, with special emphasis on liver
Authors: Howse Harold D. , Overstreet Robin M. , Hawkins William E. , Franks James S. 
Published: February 2005

AbstractThe liver of the cobia, Rachycentron canadum, was examined by gross dissection, histological, and ultrastructural procedures. Other visceral organs were examined by histological techniques only. Unique perivenous smooth muscle cords are associated with veins in these systems, but they are particularly prominent in their association with the hepatic portal veins and their numerous intrahepatic branches. The perivenous smooth muscle cords accompany tributaries of the portal veins to the junction of the venules with the hepatic sinusoids. The reciprocal contraction and relaxation of various segments of the smooth muscle cords appear to result in pooling of blood in temporary reservoirs and in its transport to various regions of the organ. This process might apply to other organ systems as well. Possibly this unique relationship of the smooth muscle cords with veins functions in a diving reflex. Triads are occasionally encountered in the cobia liver. © 1992 Wiley‐Liss, Inc.
Comparative anatomy and phylogeny of the cloacae of salamanders (Amphibia: Caudata). VI. Ambystomatidae and dicamptodontidae
Authors: Sever David M. 
Published: February 2005

AbstractHistology of the cloacae of Rhyacotriton olympicus and representative species from the genera Ambystoma and Dicamptodon was examined by light microscopy. Females of Ambystoma possess sperm storage glands, the spermathecae, as well as ventral glands and dorsal glands, both of uncertain function. Females of Ambystoma examined from the subgenus Linguaelapsus differ from those in the subgenus Ambystoma by possessing more extensive ventral gland clusters and a shorter cloacal tube. Females of Dicamptodon possess spermathecae and ventral glands, but differ in cloacal conformation from females of Ambystoma and lack the dorsal glands. Females of R. olympicus possess more extensive epidermal lining in the cloaca than that found in females of Ambystoma and Dicamptodon, and the only glands present are spermathecae, which cluster around a tube in the dorsal roof. Males of Ambystoma, Dicamptodon, and R. olmpicus possess five types of cloacal glands (dorsal pelvic glands, lateral pelvic glands, anterior ventral glands, posterior ventral glands, and Kingsbury's glands) that function in spermatophore formation, and vent glands that may produce a courtship pheromone. In Ambystoma and Dicamptodon, vent glands secrete along the medial borders of the cloacal orifice. Males of A. opacum and A. talpodeum differ from males of other species examined from the two genera by possessing more extensive vent glands. Males of R. olympicus possess unique vent glands in which tubules secrete onto the surface of vent lobes lateral to the posterior end of the cloacal orifice, and distal ends of the glands pass anteriorly, superficial to the fascia enclosing the other cloacal glands. The results from analysis of cloacal anatomy support other data indicating that Ambystoma and Dicamptodon are sister groups, and that Rhyacotriton olympicus is not closely related to either of the other two genera and merits placement in a separate family. © 1992 Wiley‐Liss, Inc.
External micromorphology of the frons plate and its adjacent areas in workers of the oriental hornet
Authors: Ishay Jacob S. , Ganor Eliezer 
Published: February 2005

AbstractThe micromorphology of the frons and the adjacent regions in young workers (1–24 hr of age) of the Oriental hornet Vespa orientalis and some adult worker hornets is described. The young workers still lack globular secretions at the bases of the setae. Such secretions do occur at the bases of the setae in the adult workers and are composed mainly of the elements Si, Al, S, Mg, Ca, Cl, and Fe. Contiguous with each of the ocelli is a gland that also secretes minerals. Young workers usually have a relatively large concentration of Ca in the glands behind the paired ocelli. The gland associated with the median anterior ocellus opens by an elongated sutura coronalis in the frons and contains various elements, predominantly Si, but also Ca. The setae (hairs) on the frons are arranged in concentric circles around each of the ocelli; they are long in the upper part of the frons but shorten gradually toward the tip of the frons. The tip lacks hair, but the cuticle bears elevated scales that project as cuticular protuberences. It appears that the ocelli and their associated glands, and the entire frons plate with its hairs and glands at the bases of the hairs in this region, comprise an equilibrium “organ” that senses changes in gravity. © 1992 Wiley‐Liss, Inc.
Early development of the actinopterygian head. I. External development and staging of the paddlefish Polyodon spathula
Authors: Bemis W. E. , Grande L. 
Published: February 2005

AbstractA large sample of embryological material of the North American paddlefish Polyodon spathula (Acipenseriformes: Polyodontidae) confirms that early development in Polyodon is very similar to that reported for the sister group of Polyodontidae, the sturgeons (Acipenseridae). Polyodon illustrates many basic aspects of acipenseriform (and actinopterygian) head development that have not been adequately described. In this paper, we provide an overview of external features of cranial development using scanning electron microscopy. The observations are correlated with staging schemes previously proposed for paddlefishes and other acipenseriforms. Events that occur after the start of neurulation (stage 19) to the start of feeding (stage 46) are emphasized. New information on the structure and folding of the mandibular and hyoid segments permits an understanding of the early development of the pharyngeal region. In addition, we offer new descriptions of the hatching gland, the olfactory organ, the sensory barbel, and the initiation of paddle outgrowth. We also comment on the mode of origin of the hypophysis, and refute the notion that it is derived from the lips of the anterior neuropore as suggested in older literature. This information sets the stage for future comparative and experimental studies of the embryology of basal actinopterygians. © 1992 Wiley‐Liss, Inc.
Skull mechanics in the pigeon, Columba livia, a three‐dimensional kinematic model
Authors: Van Gennip E. M. S. J. , Berkhoudt H. 
Published: February 2005

AbstractThe mechanics of the skull of the pigeon are analyzed quantitatively, based on a three‐dimensional kinematic computer model that considers the skull as a mechanism (Goodman, '60). The degrees of freedom at each cranial joint are defined and translated into geometric relations, using the method of Elshoud ('80). The model predicts the positions of cranial elements from three input variables: the positions of the upper and lower bills and the length of the M. protractor quadrati et pterygoidei. Simulations with the model suggest the presence of a locking mechanism for the lower bill, which prevents its depression. High speed films of feeding pigeons confirmed that locking can occur at different upper bill positions. The locking mechanism may permit feeding pigeons to use the elastic energy stored in the hinge of the upper bill during the grasp, producing simultaneous fast closing of the upper and lower bills. Simulation of jaw muscle activity suggests that these jaw muscles should not be divided into “openers” and “closers.” © 1992 Wiley‐Liss, Inc.
Morphological gradients in the starling basilar papilla
Authors: Fischer Franz Peter , Miltz Christina , Singer Ingrid , Manley Geoffrey A. 
Published: February 2005

AbstractThe starling cochlea was studied with TEM at four locations along the basilar papilla to investigate gradients in morphological features over the papilla's length and width. Hair cell shape changes continuously from neural to abneural and from basal to apical. Unlike the situation in mammals, there are no distinct populations of hair cells; the previously described types (tall hair cells and short hair cells) are merely extremes in a continuum. Contacts between THC are a normal feature. Except at the base of the papilla, SHC have very large cuticular plates, suggesting a micromechanical function for these cells. In contrast to the THC, the SHC normally completely lack afferent innervation; this indicates that their function is restricted to within the basilar papilla itself. © 1992 Wiley‐Liss, Inc.
Ultrastructural changes in guinea pig endometrial cells during the estrous cycle
Authors: Alkhalaf M. , Propper A. Y. , Chaminadas G. , Adessi G. L. 
Published: February 2005

AbstractIn the guinea pig, the estrous cycle is characterized by constant measurable level of plasma progesterone with two peaks: the first one associated with the peak of plasma estradiol‐17β occurring at proestrus and the second, during diestrus, more pronounced at the time at which the level of estradiol‐17β is undetectable. The progesterone receptor content is the highest on day 1 and the lowest on day 10 of the estrous cycle, which lasts 16.3 · 1.5 days (n = 37; mean · SD). There is a positive correlation between the plasma level of estradiol‐17β and the progesterone receptors detected immunocytochemically in both endometrial epithelial and stromal cells. The general morphology of the endometrium during prcestrus and estrus is consistent with an estrogenic stimulation, i.e., a smooth and regular surface of the endometrium and the presence of numerous microvilli on the cell surface. However, a moderate secretory activity also occurs in proestrus and estrus. During postestrus, the glandular cells display an increase in characteristic secretory features which parallels the rise of progesterone in the plasma. © 1992 Wiley‐Liss, Inc.
A study of ovarian foilicular kinetics, oviduct, fat body, and liver mass cycles in laboratory‐maintained Rana cyanophlyctis in comparison with wild‐caught frogs
Authors: Pancharatna K. , Saidapur S. K. 
Published: February 2005

AbstractOvarian follicular dynamics and fluctuations in fat body, oviducal, and liver masses were studied in captive Rana cyanophlyctis in comparison with wild‐caught frogs, sampled at monthly intervals over a period of 12 months. In both the captive and wil‐dcaught frogs first growth phase (FGP) and second growth phase (SGP) or vitellogenic oocytes were produced throughout the period examined; however, changes in ovarian and oviducal weights were less marked in the former group.In the captive frogs SGP oocyte production was reduced by 50%, and, maximum ovarian weight and SGP oocyte number were attained 2–3 months earlier than in wild‐caught controls. The FGP oocyte pool in laboratory‐maintained frogs, however was comparable with that of the corresponding wild‐caught frogs. Captivity caused a threefold increase in atresia and reduced the number of oocytes reaching SGP. The depletion of fat stores in fat bodies during the later phases of captivity suggests that the deposition of lipids into oocytes (for SGP) was given priority over storage in the fat bodies.The low oviducal weights of captive frogs was correlated with a reduced number of SGP oocytes, which are the source of estrogen. On the other hand, liver weight remained high, indicating adequate hepatic vitellogenin synthesis. Possible reduction in its output was not detected, possibly due to the reduced number of follicles reaching SGP. The findings indicate that stress of captivity decreases gonadotrophins and estrogen levels. Oviducal growth is reduced in captive frogs. It is hypothesized that in the frog oviducts respond to estrogen in a threshold‐dependent manner, whereas the liver responds to it in relation to the length of exposure. © 1992 Wiley‐Liss, Inc.