bluuebunny/crossref_metadata_2025 huggingface dataset:
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

The 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

The 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

Many 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

The 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

Histology 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

The 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

A 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

The 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

The 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

In 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

Ovarian 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.
Cruciate ligaments of the avian knee: Insight into a complex system
Authors: Fuss Franz K. , Gasser Chris R.
Published: February 2005

The avian cruciate ligaments were examined in Gallus domesticus, Anas platyrhynchos, Meleagris gallopavo, and Struthio camelus australis. The ligaments proved to be deviated around the intercondylar groove (cranial cruciate) and around the medial femoral condyle (caudal cruciate). Four functionally different fiber groups could be differentiated: fibers taut only in maximal extension, fibers taut only in maximal flexion, fibers taut in ranges from an intermediate position to an extreme position, and fibers taut throughout the entire range of motion (guiding bundles). Hence the cruciates serve the guiding of the joint and the restriction of motion, whereby the majority of the cranial cruciate fibers are taut in extension while those of the caudal cruciate are in flexion. No differences were found between the species examined with respect to fiber arrangement and function. The avian mechanical model proved to be more complex than the relatively simple mammalian four‐bar link model as the avian guiding bundles change their shape due to deflection during motion. © 1992 Wiley‐Liss, Inc.
Renal haemopoietic tissue of the mudskipper Periopthalmus koelreuteri (Pallas)
Authors: El‐Sayed N. K. , Safer A. M.
Published: February 2005

The renal haemopoietic tissue of the mudskipper Periophthalmus koelreuteri was examined by light and electron microscopy. Leukopoietic zone surrounding melanomacrophage center and erythropoietic zone were differentiated. The ultrastructural features of the cellular components of the haemopoietic compartments are similar to those described in other fishes. Despite the presence of lymphoid cells, this tissue is mainly myeloid, and active granulopoiesis and erythropoiesis occur, as in the red bone marrow of higher vertebrates. © 1992 Wiley‐Liss, Inc.
Comparative skeletogenesis of the forearm of the little brown bat (Myotis lucifugus) and the norway rat (Rattus norvegicus)
Authors: Adams Rick A.
Published: February 2005

This study describes, quantifies, and compares the growth and development of the volant forelimb morphology of Myotis lucifugus with that of the terretrial forelimb morphology of Rattus norvegicus. In M. lucifugus there is (1) accelerated growth in forearm length after parturition, (2) cessation in growth of the midshaft diameter of the ulna just after the onset of osteogenesis, (3) proximal fusion of the radius and ulna, which results in the radius occupying 97% of the articular surface of the elbow joint in adults, (4) fusion between the cartilaginous distal epiphyses of the radius and ulna which results in formation of a radioulnar bridge that becomes fully ossified in adults, and (5) incomplete ossification of the ulna with a section of the diaphysis becoming ligamentous. None of these events occurs during development in R. norvegicus. © 1992 Wiley‐Liss, Inc.
Specialized veins in the submucosa of the equine lleocecal junction
Authors: Kotzé Sanet H. , Soley J. T.
Published: February 2005

Spirally arranged bundles of sub‐endothelial smooth muscle enfold the small to medium‐sized submucosal veins in the equine ileocecal junction. The muscle bundles, accompanied by the endothelial lining, bulge into the lumen of the vessels, partly occluding the latter. Transmission electron microscopy of the muscle cells reveals features consistent with vascular smooth muscle ultrastructure. It is proposed that the throttling effect of the muscle bundles causes engorgement of the submucosal venous plexus, which then assists in the closing of the ileocecal orifice. © 1992 Wiley‐Liss, Inc.
Configurations of the rectus abdominis muscle of anuran tadpoles
Authors: Carr Karen M. , Altig Ronald
Published: February 2005

Configurations of the rectus abdominis in tadpoles of 60 anuran species in 13 families were examined. This muscle is present by Gosner stage 25 and does not change until late in metamorphosis. The anterior terminus of the r. abdominis usually is a straight, transverse front or fan‐shaped array only loosely associated with the rectus cervicis. In some suspension feeders (Rhinophrynus, Xenopus, but not microhylids), macrophagous suction feeders (Lepidobatrachus) and bromeliad inhabitants (Hyla bromeliacia) the r. abdominis is contigous with the r. cervicis which continues anterolaterally and dorsally from the wall of the spiracular cavity. Suctorial forms (Scutiger), those that live in confined spaces (burrowers, Centrolenella; bromeliad inhabitants, Hyla bromeliacia), and the taxa that have the r. cervicis and r. abdominis contiguous all have closed myosepta; the myosepta of other taxa; except for ones with large tadpoles (e.g., Rana catesbeiana), have large gaps between at least anterior myotomes. These initial data suggest that the configurations of the r. abdominis have responded to selection based on ecomorphological function and convergence among lineages are noted. © 1992 Wiley‐Liss, Inc.
Cranial osteogenesis in Monodelphis domestica (Didelphidae) and Macropus eugenii (Macropodidae)
Authors: Clark Christopher T. , Smith Kathleen K.
Published: February 2005

The pattern of onset and general rate of cranial ossification are compared in two marsupials, Monodelphis domestica (Didelphidae) and Macropus eugenii (Macropodidae). In both species a similar suite of bones is present at birth, specifically those surrounding the oral cavity and the exoccipital, and in both postnatal events follow a similar course. The facial skeleton matures more rapidly than the neurocranium, which is characterized by an extended period of ossification. Most dermal bones begin ossification before most endochondral bones. Endochondral bones of the neurocranium are particularly extended in both the period of onset of ossification and the rate of ossification. These data confirm suggestions that morphology at birth is conservative in marsupials and we hypothesize that the pattern of cranial osteogenesis is related to two distinct demands. Bones that are accelerated in marsupials are correlated with a number of functional adaptations including head movements during migration, attachment to the teat, and suckling. However, the very slow osteogenesis of the neurocranium is probably correlated with the very extended period of neurogenesis. Marsupials appear to be derived relative to both monotreme and placental mammals in the precocious ossification of the bones surrounding the oral cavity, but share with monotremes an extended period of neurocranial osteogenesis. © 1993 Wiley‐Liss, Inc.
Falciparum malaria in naturally infected human patients: I. Ultrastructural differences between malaria pigments in intraerythrocytic asexual and sexual forms
Authors: El‐Shoura Samir M. , Al‐Amari Omar M.
Published: February 2005

Venous blood samples were taken from patients naturally infected with the human malaria parasite Plasmodium falciparum. Two types of malaria pigment (MP) particles have been demonstrated in intraerythrocytic asexual forms (trophozoites and schizonts), while a single type was detected in gametocytes. Type I MP particles, found in both asexual and sexual forms, are electron‐dense. It is suggested that these are proteinaceous and may be intermediate, utilizable metabolic products that serve as a food reserve during development of the parasite in the human host and also during the growth cycle of the sexual form in the mosquito. In asexual forms, type I particles occur within food vacuoles (FV) containing semidigested hemoglobin (Hg), while they are unenveloped in the cytoplasm of the sexual forms. Type II MP particles, found in electron‐lucent residual bodies, are crystalloid and of low electron density. It is suggested that these are the final, waste product of Hg digestion in the asexual forms. © 1993 Wiley‐Liss, Inc.
Falciparum malaria in naturally infected human patients: II. Ultrastructural alterations to erythrocytes infected with asexual forms
Authors: El‐Shoura Samir M. , Al‐Amari Omar M.
Published: February 2005

Ultrastructural alterations of human erythrocytes infected with asexual forms of Plasmodium falciparum were studied in naturally infected Saudi patients. These included surface knobs and nodules as well as invaginations associated with cytopasmic vesicles observed in erythrocytes infected with asexual forms of the parasites. Such nodules and surface invaginations have been previously described only in erythrocytes infected with P. ovale and P. vivax, respectively. Within the cytoplasm of infected erythrocytes were membrane‐bound clefts, similar to those that appear to be a common characteristic in all red cells infected with malaria parasites. Vacuolations were often seen in the peripheral cytoplasm and may represent hemolyzed areas. Collapsed cells with an internal‐lucent interior and surrounded by an irregularly folded membrane may represent completely hemolyzed erythrocytes. © 1993 Wiley‐Liss, Inc.
A microscopic investigation of the lymphoid organs of the beluga, Delphinapterus leucas
Authors: Romano Tracy A. , Felten Suzanne Y. , Olschowka John A. , Felten David L.
Published: February 2005

Lymphoid organs from belugas, Delphinapterus leucas, ranging in age from less than one to 16 years, were harvested during a sanctioned hunt to investigate morphology. The spleen is divisible into red and white pulp and a stroma consisting of a reticular network, a collagenous capsule, and trabeculae containing smooth muscle bundles. White pulp areas appear to be devoid of follicles and consist mainly of periarteriolar lymphatic sheaths (PALS), that are larger in younger than in older belugas. Definitive marginal zones between red and white pulp are difficult to discern in older belugas. Lymph nodes are similar to those of other mammals; they possess a follicular cortex surrounding a vascular medulla composed of lymphatic cords and sinuses. Smooth muscle is abundant in the medullary region, usually in close proximity to sinuses. The expansive nodular mass at the root of the mesentery, often referred to as the “pseudopancreas,” is similar to lymph nodes in microscopic architecture. Pharyngeal tonsils and gut‐associated lymphoid tissue (GALT) are found along the digestive tract and display an “active” morphology. Tonsils are comprised of lobules of follicles separated by vascular connective tissue. Epithelial‐lined crypts communicate with the pharyngeal lumen. GALT consists of diffuse and follicular lymphocytes within the intestinal mucosa and submucosa. The thymus is well developed in the younger belugas, with lobules divisible into densely packed cortical zones of thymocytes and more loosely arranged medullary lymphocytes. Hassall's corpuscles are occasionally visible within the medulla. Cetaceans diverged evolutionarily from other mammals over 55 million years ago. This study investigates changes in lymphoid organ morphology in a species that now inhabits a unique ecological niche. This study also lays the groundwork for functional investigation of the beluga immune system, particularly as it relates to differences between healthy and stranded animals. © 1993 Wiley‐Liss, Inc.
Evolution and functional significance of tendon ossification in woodcreepers (Aves: Passeriformes: Dendrocolaptinae)
Authors: Bledsoe Anthony H. , Raikow Robert J. , Glasgow Angela G.
Published: February 2005

The woodcreepers, a clade of scansorial, neotropical birds, are distinctive among passerines in having extensive tendon ossification. Dissection of 42 of the 50 species indicates that such ossification in the hindlimb is limited almost entirely to tendons of insertion of the crural muscles. Most crural muscles have ossifications, and in all but one the ossified tendons are long and thin. Preliminary dissection revealed a similar pattern among ossified wing tendons. Phylogenetic analysis suggests that extensive tendon ossification is a synapomorphy of the woodcreepers. The species ofDendrocincla, which form a clade, show secondary reduction of ossification in some tendons, which may be correlated with increased intraspecific variation and with an expansion of foraging habits and postures to include nonscansorial behaviors. In contrast, the larger woodcreepers, other thanDrymornis bridgesiiandNasica longirostris, form a clade with virtually no loss in ossification or evidence of intraspecific variation, even in large series of two species. Phylogenetic losses do not occur for the primary flexor of the ankle (M. tibialis cranialis), whereas two extensors (Mm. fibularis longus and gastrocnemius pars lateralis) show a complex pattern of derivation and loss. Previous biomechanical studies demonstrate that ossification increases the stiffness of tendons, making them stretch less under a given force. These structural and phylogenetic patterns are consistent with the view that hindlimb tendon ossification in woodcreepers is an adaptation to resist increased forces that act to extend the limb during vertical climbing. © 1993 Wiley‐Liss, Inc.
In‐series fiber architecture in long human muscles
Authors: Heron Marcia I. , Richmond Frances J. R.
Published: February 2005

The fiber architecture of adult human sartorius and gracilis muscles was examined using a combination of fiber microdissections and histological methods. Intact fibers were dissected from fascicles of muscle strips that were digested in nitric acid. All of these fibers terminate intrafascicularly by tapering to a fine strand at one or both ends. They measure 4–20 cm after correction for shrinkage. Systematic dissections of 1 cm long blocks sampled at intervals along the muscle length suggest that tapered fiber endings occur at all locations along the muscle but are most common centrally; here they accounted for up to 14% of dissected fibers in each block. Transverse sections of muscle confirm that fiber profiles with small diameters occur at all levels of the muscle but are especially common in sections more than 5 cm from its origin or insertion. The architectural arrangement demonstrated here suggests that long human muscles, like muscles in other species, are composed of relatively short, in‐series fibers. This has many implications for the neural activation and force‐developing behavior of these muscles that must be considered when paralyzed muscles are reanimated using electrical stimulation. Further, it may predispose long muscles to certain types of neuromuscular damage and dysfunction. © 1993 Wiley‐Liss, Inc.
Structure and histochemical organization of the spleen of Agama stellio (Sauria: Agamidae) and Chalcides ocellatus (Sauria: Scincidae)
Authors: Saad A.‐H. , Bassiouni W. M.
Published: February 2005

The spleen of Agama stellio is composed mainly of red pulp; the white pulp is poorly developed, and its clusters are scattered throughout the organ and contain lymphocytes, reticular cells, and some plasma cells. The red pulp consists of clear reticular cells intermingled with blood cells, sinusoids, and pigment cells. The spleen of Chalcides ocellatus is encapsulated by connective tissue and is composed of white and red pulp. The white pulp consists of lymphoid tissue that surrounds the central arterioles, forming the periarteriolar lymphocyte sheath (PALS). The red pulp is composed of a system of venous sinuses and cords. The results of various histochemical procedures designed to demonstrate mucosubstances, proteins, and nucleic acids indicate that the spleen in these species resembles the mammalian spleen. © 1993 Wiley‐Liss, Inc.
Histology of the late‐stage placentae in the matrotrophic skink Chalcides chalcides (Lacertilia; Scincidae)
Authors: Blackburn Daniel G.
Published: February 2005

Examination of late‐stage placental material of the lizard Chalcides chalcides from the Hubrecht Laboratorium (Utrecht, The Netherlands) reveals several cytological and histological specializations that appear to have been superimposed over a morphological pattern that is typical for squamates. The chorioallantoic placenta is highly vascularized and consists of a single mesometrial placentome and a generalized paraplacentomal region, both of which are epitheliochorial. The placentome is deciduate, and contains deeply interdigitating folds of hypertrophied uterine and chorioallantoic tissue. Chorionic epithelium lining the placentome comprises enlarged, microvilliated cells, a small proportion of which are diplokaryocytes. The placentomal uterine epithelium is not syncytial and consists of enlarged cells bearing microvilli. The yolk sac placenta is a true omphaloplacenta (sensu stricto), being formed by juxtaposition of uterine tissues to an avascular, bilaminar omphalopleure. Epithelium of the omphalopleure is stratified and is hypertrophied into papillae that project into detritus of the uterine lumen. The omphalopleure is separated from the yolk sac proper by a yolk cleft that is not confluent with the exocoelom and is not invaded by the allantois. Neither an omphalallantoic placenta nor a true choriovitelline placenta is present in late gestation. Morphologically, the mature placentae of C. chalcides are among the most specialized to have been described in reptiles, reflecting the substantial maternal‐fetal nutrient transfer that occurs in this species. © 1993 Wiley‐Liss, Inc.
Androgen effects on vocal muscle structure in a teleost fish with inter‐ and intra‐sexual dimorphism
Authors: Brantley Richard K. , Marchaterre Margaret A. , Bass Andrew H.
Published: February 2005

The plainfin midshipman fish Porichthys notatus has both interand intra‐sexual dimorphism in the sound‐producing (vocal or sonic) muscles attached to the swimbladder wall. The “Type I” and “Type II” male morphs differ in that dramatic structural changes related to sexual maturity occur in the mass, the area of mitochondria‐filled sarcoplasm, and the myofiber number of the sonic muscles of Type I males, but not in those of Type II males (nor of females). Androgen implantation for 9 weeks markedly increased the relative sonic muscle size in juvenile males, juvenile females, and Type II males, whereas estradiol or cholesterol treatment did not. The principal androgen effect on myofiber structure was an increase in the area of mitochondria‐filled sarcoplasm. The ratio of sarcoplasm area to myofibril area (Sr/Mf) increased by 1.4‐ to 2‐fold in myofibers of all androgen‐treated groups, with the greatest structural change occurring in juvenile males. When androgen implants were removed from juvenile males, the muscle mass and Sr/Mf ratio reverted toward the unimplanted juvenile phenotype. Total fiber number in sonic muscle increased significantly in juvenile males following androgen implantation but did not detectably change in juvenile females or Type II males. These results suggest: (1) sonic muscle in Porichthys notatus is an androgen target tissue, (2) fiber structure and fiber number are androgen‐sensitive features, and (3) there exist sex‐ and morph‐specific patterns of sonic muscle responsiveness to androgen implants. © 1993 Wiley‐Liss, Inc.
Muco‐follicle cells of the jelly coat in the oocyte envelope of the sheatfish (Silurus glanis L.)
Authors: Abaham Mordechai , Hilge Volker , Riehl Rüdiger , Iger Yoni
Published: February 2005

During early vitellogenesis of the oocytes of Silurus glanis, the follicular cells proliferate, their epithelial organization becomes disrupted, and they transform into an irregularly structured large mass of cells engaged in intensive secretory activity. They contain nuclei, rough endoplasmic reticulum, Golgi bodies, and secretory inclusions termed “acorn bodies,” which are synthesized in the cytoplasm. The acorn bodies have two components: an electron‐dense cap and a moderately electron‐dense body. As development proceeds, the acorn bodies become modified into spherules of mucous material, the mucosomes. The electron‐dense part persists as a small calotte or crescent often irregularly structured at the periphery of the mucosome, and fragments of it are dispersed into the interior of the mucosomal body. The mucosomes are membrane‐bound and contain small granules, 55 nm in diameter.

At the end of vitellogenesis, the follicle cells are filled with mucosomes, and cytoplasmic residua can only sparingly be observed among them. Oocytic microvilli extend through the zona radiata and intermingle with follicular cell processes in the cleft between the zona radiata and the belt of mucosomes during growth of the oocyte. Capillaries develop in connective tissue of the theca layer as vitellogenesis proceeds. © 1993 Wiley‐Liss, Inc.
Fine structure of the nephridial muscle layer cells of Phascolosoma granulatum (Sipuncula)
Authors: Serrano Teresa , Angulo Eduardo , Mateo Antonio , Moya Jesus
Published: February 2005

The nephridial muscle layer of Phascolosoma granulatum consists of a network of longitudinal and circular cells separated by connective tissue matrix. The muscle fibers are densely packed with thick and thin myofilaments, among which are scattered cytoplasmic dense bodies. The nucleus and noncontractile cytoplasmic organelles occupy a lateral projection from the contractile portion of the fiber. Cytoplasmic dense bodies are the result of a clustering of an indeterminate number of the thin actin filaments that fill the cytoplasm between thick filaments. Attached to the cytoplasmic face of the cell membrane are membrane‐associated electron‐dense plaques. These sites are linked to the contractile myofilaments by narrow filamentous bridges. Extracellular narrow filaments extend from these plaques to collagen fibers of the connective tissue matrix. Differences in length of the dense plaques may be related to differences in thick myofilament diameter in three types of muscle fiber, types A, B and C, statistically distinguished by mean fiber size differences. The plaques may serve as connecting links for the transmission of tension from contractile units to the connective tissue of the muscle layer. © 1993 Wiley‐Liss, Inc.
Turkey embryo staging from cleavage through hypoblast formation
Authors: Gupta S. K. , Bakst M. R.
Published: February 2005

The progressive development of the turkey embryo from first cleavage through hypoblast formation was examined in order to determine the applicability of a chicken embryo staging procedure. It was concluded that the temporal and spatial events associated with the development of the early turkey embryo are sufficiently different from those of the chicken embryo to warrant a separate staging procedure. Cleavage is asynchronous and often results in asymmetrical segmentation. Unlike the chicken embryo, which at oviposition has already formed the area pellucida and area opaca and is classified as a Stage X embryo, the turkey embryo at oviposition is only at the beginning of area pellucida formation and is classified as a Stage VII embryo. After about 3 hr of incubation and prior to completion of the area pellucida, hypoblast formation begins at the posterior end, thereby establishing the bilaterally symmetrical pattern of the embryo. When viewed from the dorsal surface, an opaque region is observed at the center of the area pellucida. This opacity is unique to the turkey embryo and is referred to as the area alba. When viewed from the ventral surface, the area alba appears to be composed of large whitish cells. To conclude, the rate of turkey embryo development through the completion of hypoblast formation, which consists of 11 stages, lags behind that of the chicken. Furthermore, the organization as well as origin of the area pellucida and hypoblast observed in the turkey embryo differ from that of the chicken embryo. © 1993 Wiley‐Liss, Inc.
Histochemical and myosin composition of vampire bat (Desmodus rotundus) pectoralis muscle targets a unique locomotory niche
Authors: Hermanson John W. , Cobb Matthew A. , Schutt William A. , Muradali Farouk , Ryan James M.
Published: February 2005

The vampire bat pectoralis muscle contains at least four fiber types distributed in a nonhomogeneous pattern. One of these fiber types, here termed IIe, can be elucidated only by adenosine triphosphatase (ATPase) histochemistry combined with reactions against antifast and antislow myosin antibodies. The histochemical and immunohistochemical observations indicate a well‐developed specialization of function within specific regions of the muscle. In parallel, analyses of native myosin isoforms and myosin heavy chain isoforms indicate two points. First, the histochemical “type IIe” fiber is predominant in cranial portions of the muscle, and myosin extracted from these regions exhibits a unique electrophoretic mobility not observed in the myosin isoforms of more traditional laboratory mammals. Second, the type I fibers are confined to the pectoralis abdominalis muscle and a small adjacent region of the caudal part of the pectoralis. This pattern of type I fiber distribution is considered a derived character state compared to muscle histochemical phenotype and isoform composition in the pectoralis muscles of other phyllostomids we have studied (Artibeus jamaicensis, Artibeus lituratus, Carollia perspicillata). We relate this to the unique locomotory needs of the common vampire bat, Desmodus rotundus. © 1993 Wiley‐Liss, Inc.
Cephalometric correlates of echolocation in the chiroptera
Authors: Pedersen Scott C.
Published: February 2005

This study suggests that the evoution of head posture is bats is constrained by the demands of vocalization during echolocation. Nasalemitting microchiropteran taxa are easily identified by their characteristic rotation of the basicranium ventrally about the cervical axis, the depression of the rostrum below the basicranial axis, and by the rotation of the lateral semicircular canals so as to maintain their horizontal orientation during flighrt. The converse is true for oral‐emitting Microchiroptera. The general form of the microchiropteran skull has been canalized along two distinct evolutionary paths, respectively, towards oral‐emitting or nasal‐emitting forms. © 1993 Wiley‐Liss, Inc.
Variable manifestations in the short toes (s) mutation of the axolotl
Authors: Washabaugh Charles H. , Del Rio‐Tsonis Katia , Tsonis Panagiotis A.
Published: February 2005

We describe a detailed histological analysis of the affected organs in the Short toes (s) mutation of the Mexican axolotl, Ambystoma mexicanum. The s mutant animals displayed a variation in the response to the mutation such as the time of death and the degree of abnormalities of the affected organs (limbs, kidney, ducts, and reproductive structures). In addition to the numerous histological abnormalities characterized here, we also examined the presence of laminin‐related molecules in s mutant kidney tissues to elucidate further the nature of the renal aplasia these animals encounter as a result of this recessive lethal mutation. Our data suggest that there may be a disruption in tissue interactions necessary for proper development and functioning of the affected tissues. © 1993 Wiley‐Liss, Inc.
Heterodonty and patterns of tooth replacement in Crocodylus niloticus
Authors: Kieser J. A. , Klapsidis C. , Law L. , Marion M.
Published: February 2005

Patterns of tooth replacement in the Nile crocodile Crocodylus niloticus were evaluated in the lateral radiographs of six dried skulls of 1‐year‐old individuals. Additionally, the ontogeny of the succession of teeth in this species was investigated in four embryos and a hatchling, which were serially sectioned. Three‐dimensional, computer‐generated reconstructions of these individuals suggested that there was a regular pattern of odontogenic progression. Three morphogenetic zones could be identified in each of the age classes: an incisor, a canine, and a molar region. It was thus concluded that the Nile crocodile is hetero‐ rather than homodont. Zahnreihen, or tooth rows, with a periodicity of one were easily identified. © 1993 Wiley‐Liss, Inc.
Quantitative investigations of spinal motoneurons and their synaptic structures in a teleost: A morphometrical analysis with special reference to axosomatic synapses
Authors: Saito K. , Matsumura A.
Published: February 2005

The ultrastructural and morphometrical synaptology of the spinal motoneurons in Carassius auratus (goldfish) was analyzed based on profiles of 23 photomontages of large motoneurons and 25 putative small motoneurons with a semiautomatic digitizing system connected with a computer. In the 23 large motoneurons (mean circumference, 142.45 ± 39.76 μm) the total linear perikaryal circumference was 3,276.28 μm, of which 1,548.9 μm (46.1 ± 13.9%) was covered by terminal boutons. In contrast, a total linear perikaryal circumference of 1,375.24 μm (55.01 ± 14.34 μm) of the 25 putative small motoneurons was covered with terminal boutons only occupying a length of 287.45 μm (19.8 ± 11.9%). There were a total of 1,045 boutons on the large motoneurons and 204 on the small ones. The distribution of S‐ and F‐type boutons may reflect excitatory and inhibitory synapses. The relative number of S‐type boutons (58%) was larger than that of F‐type boutons (42%) in the large neurons and showed similar values (S‐type, 57%; F type, 43%) in the small ones. This is in contrast to mammalian spinal motoneurons in which F‐type boutons are more prevalent than the S‐type. The total numbers of the axosomatic boutons in large and small neurons were estimated, based on geometrical assumptions and found to differ substantially (840 vs. 59). This indicates large quantitative differences in the total number of synaptic inputs with the large motoneurons having a greater more axo‐somatic bouton density. No large M‐ and C‐type boutons occur on the spinal motoneurons of goldfish, suggesting a synaptic organization which is simple compared to that of terrestrial vertebrates. © 1993 Wiley‐Liss, Inc.
Comparative microanatomy of the branchial sieve in three sympatric cyprinid species, related to filter‐feeding mechanisms
Authors: Van Den Berg Coen , Van Snik Geert J. M. , Van Den Boogaart Jos G. M. , Sibbing Ferdinand A. , Osse Jan W. M.
Published: February 2005

According to the reducible‐channel model of filter‐feeding (Hoogenboezem et al., '91), small food particles are retained in the channels between the medial gill rakers, while the mesh size can be reduced by lowering the lateral gill rakers into these channels. This movement requires that all lateral gill rakers have a m. abductor branchiospinalis (MAB). MAB runs from the radii branchiales to the raker feet. It is present on the lateral side of all four gill arches of the cyprinids Abramis brama and Cyprinus carpio but only on the first arch of Blicca bjoerkna, Rutilus rutilus, Ctenopharyngodon idella, Aspius aspius, and Scardinius erythrophthalmus. Therefore, the latter species do not fulfill the structural requirement for the reducible‐channel model, whereas A. brama and C. carpio do. Laboratory and field data confirm that A. brama and C. carpio can reduce their mesh size according to this model and are the better filter‐feeders. The seven cyprinid species studied show the same principal microanatomy of their branchial sieve. M. abductor filamenti is a sheet of muscle fibers between the lateral radii branchiales and the ceratobranchial bone. M. branchialis superficialis is a specialized region of the subepithelial muscle fiber network, with origins along both sides of the ceratobranchial bone. The lateral gill rakers of the first gill arch differ conspicuously from all other rakers. They are longer and flattened, and they are tilted anteriorly. They probably form a sieve across the wide slit between the first gill arch and the operculum. The most revealing anatomical feature is the presence of MABs on gill arches 1–4. It might be a suitable bio‐assay for identifying the better facultative filter‐feeders among cyprinids. © 1994 Wiley‐Liss, Inc.