bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observations on the development of unusual melanization of leopard frog ventral skin
Authors: Fernandez Philip J. , Bagnara Joseph T. 
Published: February 2005

AbstractThe ontogeny of ventral pigmentation of two species of leopard frog, Rana pipiens and R. chiricahuensis, was examined by light microscopy and transmission electron microscopy to reveal how the unusual melanistic ventral pigmentation of R. chiricahuensis is achieved at the cellular level. Ventral skin of R. pipiens is always white. Ventral skin of adult R. chiricahuensis is white when frogs are background‐adapted to a white substrate, but ventral skin becomes nearly as dark colored as the dorsal skin when frogs darken in response to a black background. Skin samples from tadpoles of both species, newly metamorphosed frogs, and adult frogs were analyzed for chromatophore composition and distribution. Ventral skin of R. pipiens larvae, newly metamorphosed frogs, and adults and of R. chiricahuensis larvae was white due to abundant iridophores and no melanophores. Melanophore density in the ventral integument of R. chiricahuensis was 9.1 ± 2.8/mm2 in newly metamorphosed frogs and 87.0 ± 4.8/mm2 in adult frogs. Pigment within ventral melanophores migrated during physiological color change during background adaptation. © 1993 Wiley‐Liss, Inc.
Suboccipital muscles in the cat neck: Morphometry and histochemistry of the rectus capitis muscle complex
Authors: Selbie W. S. , Thomson D. B. , Richmond F. J. R. 
Published: February 2005

AbstractThe morphometry, histochemistry, and biomechanical relationships of rectus capitis muscles were examined in adult cats. This family of muscles contained six members on the dorsal, ventral, and lateral aspects of the upper cervical vertebral column. Three dorsal muscles (rectus capitis posterior major, medius, and minor) formed a layered complex spanning from C1 and C2 to the skull. Rectus capitis posterior major was composed predominantly of fast fibers, but the other two deeper muscles contained progressively higher proportions of slow fibers. One ventral muscle, rectus capitis anterior major, was architecturally complex. It originated from several cervical vertebrae and appeared to be divided into two different heads. In contrast, rectus capitis anterior minor and rectus capitis lateralis were short, parallel‐fibered muscles spanning between the skull and C1. The ventral muscles all had nonuniform distributions of muscle‐fiber types in which fast fibers predominated. Dorsal and ventral muscle groupings usually had cross‐sectional areas of 0.5 cm2 or more, reflecting a potential capacity to generate maximal tetanic force in excess of 9 N. Biomechanical analyses suggested that one muscle, rectus capitis lateralis, had its largest moment in lateral flexion, whereas the other muscles had large, posturally dependent moment arms appropriate for actions in flexion‐extension. The observation that most rectus muscles have relatively large cross‐sectional areas and high fast‐fiber proportions suggests that the muscles may have important phasic as well as postural roles during head movement. © 1993 Wiley‐Liss, Inc.
Organization of hematopoietic tissue in the intermolt lobster, Homarus americanus
Authors: Martin Gary G. , Hose Jo Ellen , Choi Maryanne , Provost Ron , Omori Gregg , McKrell Nancy , Lam Garrett 
Published: February 2005

AbstractHematopoiesis in the American lobster Homarus americanus, as in most decapod crustaceans, occurs in a thin tissue covering the dorsal surface of the foregut. This tissue is composed of loosely attached, ovoid lobules containing the hematopoietic precursors and maturing hemocytes. Release of hemocytes into the dorsal hemocoel is accomplished by rupture of a portion of the connective tissue capsule covering the lobule. Cross sections of the lobules contain between 6 and 40 hematopoietic cells, of which approximately 90% constitute stages in granulocyte maturation and 10% are intermediates in hyaline cell maturation. Hematopoietic precursors in these two lines are similar to those recently described in a penaeid shrimp Sicyonia ingentis. The mitotic rate averaged 5.1% (range = 0.7% to 15.8%) in intermolt lobsters, 90% comprised granulocyte precursors. © 1993 Wiley‐Liss, Inc.
Microstructure, ontogeny, and evolution of scale surfaces in xenosaurid lizards
Authors: Harvey Michael B. 
Published: February 2005

AbstractBoth scanning electron and light microscopy were used to examine the epidermal structure of scales taken from several ontogenetic stages of Xenosaurus grandis and Shinisaurus crocodilurus. In addition, scales from all xenosaurid species were examined by scanning electron microscopy to determine scale surface variation among genera, species, and subspecies. A varied and phylogenetically informative morphology characterizes the scale surfaces of xenosaurid lizards. Scale surface morphology is conservative among the species and subspecies of Xenosaurus, but is more variable between the two xenosaurid genera. Their scale surfaces are characterized by folds in the oberhautchen, beta, mesos, and alpha epidermal layers, forming polygonal ridges of a type previously described for the Iguania. The three species of Xenosaurus possess lenticular scale organs, whereas Shinisaurus has scale organs with spikes (bristles). The spikes of Shinisaurus are formed by the beta and oberhautchen layers, with the alpha layer forming a dome‐shaped cap over a dermal papilla. Shinisaurus crocodilurus exhibits a dramatic ontogenetic change in scale surface morphology, that is here reported for the first time in any lizard. © 1993 Wiley‐Liss, Inc.
Chiropteran tendon locking mechanism
Authors: Quinn Thomas H. , Baumel Julian J. 
Published: February 2005

AbstractRather than the usual mammalian scheme in which tendon and sheath surfaces provide as little friction as possible, the tendons and sheaths of many bats have a locking segment on the manual and pedal flexor tendon complex. This tendon locking mechanism (TLM) exists opposite the proximal phalanges of each toe and pollex of many bats. Its structure, similar to a ratchet mechanism, assists bats in hanging with little muscular effort. The third digit of the pelvic limb and the pollex of species representing 15 chiropteran families were studied to determine the presence or absence, morphology, and function of the TLM. Most of the species studied have a TLM consisting of a patch of tubercles on the ventral surface of the flexor tendon associated with the proximal phalanx of each pollex or toe. The sheath adjacent to this portion of the flexor tendon has a series of transverse folds or ridges, which, when engaged with the tubercles on the tendon, lock the tendon in place. The TLM is similar in megachiropterans and microchiropterans possessing it. The TLM is absent, however, in some of the microchiropterans studied, most notably in the phyllostomids. Since many birds have a TLM similar to that of bats, it is an excellent example of the convergent evolution of a feature brought about by similar functional pressures on birds and bats. © 1993 Wiley‐Liss, Inc.
Microtopography of Nippostrongylus brasiliensis (Nematoda: Heligmosomatidae): Parasitic larval stages and adults
Authors: Nembo B. , Goudey‐Perriere F. , Gayral P. , Perriere C. , Brousse‐Gaury P. 
Published: February 2005

AbstractSpecimens of the rat hookworm, Nippostrongylus brasiliensis (Nematoda) were recovered from lungs (third‐ and fourth‐stage larvae) and intestine (fourth‐stage larvae and adults). The following features were studied in the different stages by scanning electron microscopy: cephalic structures, especially sense organs, synlophe, cervical region, and caudal part. The main differences between the third and fourth stages concerned the lip‐like structures around the oral aperture, the appearance of the cephalic space with the presence of a cephalic cap in fourth‐stage larvae, the pattern of longitudinal ridges, and sexual differentiation. Pore‐like papillae, not seen in third‐stage larvae, developed in later stages. Deirids were observed only in adults, and phasmids were poorly discerned.Some of these morphological features, such as the cephalic sense organ apertures and cuticle pores and micropores, can be observed only by scanning electron microscop y. The possible functions of these different structures and their relationship with the behavior of the worms during their life cycle are discussed. © 1993 Wiley‐Liss, Inc.
Renal vasculature and excretory system of the agamid lizard, Ctenophorus ornatus
Authors: O'shea James E. , Bradshaw S. Donald , Stewart Tom 
Published: February 2005

AbstractThe structure and ultrastructure of the vasculature and nephric tubules of the kidney of the Ornate Dragon Lizard, Ctenophorus (=Amphibolurus) ornatus, was investigated by light microscopy and scanning electron microscopy of resin casts. Compared with other agamid lizards, the arterial supply of only two arteries per kidney is small. The number of glomeruli per kidney in C. ornatus, at between 400 and 600, is low by reptilian standards and very low for lizards. The glomeruli are not only comparatively few in number but are also simple in the nature of their capillary configuration. These features are suggestive of a greatly reduced surface area for arterial filtration. In contrast to the small arterial supply, the afferent venous supply, the renal portal system (RPS), is substantial and forms an extensive capillary network throughout the kidneys. No venous shunts were found in the kidneys, suggesting that the venous network is functioning as a true portal system. Valves were not identified within the RPS, implying that neural control of general vascular tone could alter velocity and perhaps the direction of blood flow by changing pressure profiles. The nephroi are comparatively short and display features consistent with the production of urate precipitates as the primary nitrogenous waste product. A close association between the distal tubule (DT) and the glomerular hilus may demonstrate a simple form of a juxtaglomerular apparatus. The finding of aglomerular tubules indicates an important role for tubular secretion. The results of this study indicate that these lizards may have a reduced reliance on filtration for homoiostasis and a greater reliance on tubular secretion. © 1993 Wiley‐Liss, Inc.
Larval and adult eyes in Capitella spec. I (Annelida, Polychaeta)
Authors: Rhode Birgit 
Published: February 2005

AbstractLarval and adult eyes of the capitellid Capitella spec. I have been investigated by electron microscopy. Developing larvae possess one pair of eyespots. Each eyespot is composed of one sensory cell, one pigment cell, and one supporting cell. The sensory cell bears a photosensory apparatus, an array of parallel microvilli containing a striking form of submicrovillar cisternae (SMC). A single basal body was observed near the basal end of the SMC only in 3–4‐day‐old larvae. This basal body was not observed in older larvae. A special, thus far unreported feature of the pigment cell is a ring of microvilli‐like structures that project from the edge of the pigment cup and form a kind of diaphragm around the head of the sensory cell. Each of these microvilli‐like structures is covered with closely packed rows of tiny plates, giving them a fimbriated appearance. After metamorphosis, the larval eyespots are reduced.Adult specimens possess one pair of eyes. In juvenile worms the eye is built of 2–3 pigment cells and one sensory cell. The volume of adult eyes increases by the addition of 2–3 sensory cells. The pigment cells are deposited one upon the other, wrapping the sensory complex in the center. Each sensory cell forms a deep depression at its apical end where up to three cilia and numerous microvilli arise. The sensory processes project into a common ocular cavity. Long microvilli of the uppermost pigment cells project into an extracellular channel that reaches from the ocular cavity up to the cuticle. A single fourth sensory cell of identical structure may occur next to the eye directly beneath the cuticle and close to the opening of the ocular channel.Signs of progressive disintegration of the pigment cells can be observed in adult specimens. Sensory cells are not affected by this reduction process. Eyes resembling those of Capitella spec. I have never been reported before. Their functional qualities are discussed. © 1993 Wiley‐Liss, Inc.
Neuromuscular organization and regional EMG activity of the pectoralis in the pigeon
Authors: Boggs Dona F. , Dial Kenneth P. 
Published: February 2005

AbstractIn order to improve our understanding of the neuromuscular control of the most massive avian flight muscle, we studied the innervation pattern of the pigeon pectoralis. Nine primary branches from the rostral trunk and nine to ten branches from the caudal trunk of the pectoral nerve were identified by microdissection in ten pigeons. The region of muscle that each branch innervates was delineated by nerve stimulation studies (ten pigeons) and six regions were confirmed by glycogen depletion (ten pigeons). In pigeons, branches from the rostral nerve innervate the anterior 3/5 of the sternobrachialis (SB) head of the pectoralis and branches from the caudal trunk innervate the posterior 1/2 of the SB and all of the throacobrachials (TB). In the SB, individual branches of the rostral pectoral nerve innervate wedge‐shaped muscle regions (each approximately 1.3 cm wide), collectively forming a fan shaped arrangement along the sternal carina. Adjacent muscle regions partially overlap at their boundaries. Within the thoracobrachialis (TB) head of the pectrolis, muscle regions are wider. There is a region in mid‐SB‐where the innervation territories of the rostral and caudal nerves oferlap. Electromyographic (EMG) activity patterns were recorded within ten of the identified muscle regions during take‐off, level flapping flight, and landing. Onset of EMG activity and EMG intensity within various muscle regions exhibits significant differences both within a wingbeat cycle and among different modes of flight. The innervation pattern of the pectoralis presents the anatomical substrate for neuromuscular compartmentalization and differential EMG activity within the pectoralis may reflect sensory‐motor partitioning. The extent to which the neuromuscular compartmentalization of the pectoralis corresponds to its ability to produce an array of force vectors to the wing awaits further more detailed biomechanical studies. © 1993 Wiley‐Liss, Inc.
Changes in geometry of activily shortening unipennate rat gastrocnemius muscle
Authors: Zuurbier C. J. , Huijing P. A. 
Published: February 2005

AbstractMuscle geometry of the unipennate medial gastrocnemius (GM) muscle of the rat was examined with photographic techniques during isometric contractions at different muscle lengths. It was found that the length of fibers in different regions of GM differs significantly, and proximal aponeurosis length varies significantly from distal aponeurosis length; the angle of the aponeurosis with the muscular action differs significantly among regions at short muscle lengths (full contraction). These data support the idea that the unipennate GM cannot be represented by a parallelogram in a two‐dimensional analysis. As the muscle shortens, the area of the mid‐longitudinal plane of the GM decreases by 24%, a decrease that may be explained by assuming fiber diameter to increase in all directions. The angle between fiber and aponeurosis is determined by more than fiber length. Hence, such important assumptions as a parallelogram with constant area and fiber angle γ changes determined by fiber length changes, freqently used in the theoretical analysis of the morphological mechanism of unipennate muscle contraction, do not hold for the unipennate GM of the rat.Length of the sarcomere within the mid‐longitudinal plane of GM varies from 1.92 to 2.14 μm among the different muscle regions at muscle optimum length (length at which force production is highest), whereas shortening to 6 mm less than optimum length produces a range of sarcomere lengths from 0.89 to 1.52 μm. These data suggest that fibers located in different regions of the GM reach their optimum and slack lengths at various muscle lengths. © 1993 Wiley‐Liss, Inc.
Two different patterns of interrupted spermatogenesis in winter diapause and summer quiescence in the desert beetle, Omorgus freyi
Authors: Friedländer Michael , Scholtz Clarke H. 
Published: February 2005

AbstractSpermatogenesis discontinues during both adult reproductive diapause and quiescence in the flightless males of Omorgus freyi. During both types of dormancy, spermatogenesis discontinuity is a dynamic process involving an uninterrupted supply of primary spermatocytes that undergoes partial development and lyses before spermatozoa can be formed. Notwithstanding this common feature, the pattern of discontinuity differs between the two kinds of dormancy. During reproductive diapause, spermatozoa and late spermatids are the first cells that lyse; after diapause break, spermatozoa are produced anew. During quiescence, in contrast, the first indication of discontinuity is the degeneration of late primary spermatocytes; spermatozoa apparently remain intact for a while but eventually degenerate as well. Therefore, males returning to sexual activity after a short period of quiescence may still have spermatozoa capable of fertilization. However, following a long period of quiescence, spermatozoa will be absent and must be produced anew, as in postdiapausing males. The existence of two different patterns of spermatogenesis discontinuity may indicate that each is controlled differently by the endocrine system, in response to the different environmental conditions inducing quiescence or diapause. Dual control of discontinuity may contribute to the high reproductive potential of these flightless beetles, under unpredictable and extreme desert conditions. © 1993 Wiley‐Liss, Inc.
Morphological and functional body reconstruction in a teleost of the genus Oreochromis (Cichlidae)
Authors: Fishelson Lev 
Published: February 2005

AbstractThe process of morphological and functional regeneration was followed on a tilapid fish, a cross of Oreochromis aureus × Oreochromis niloticus, by observations on movements and the use of X‐rays. A four‐year‐old adult fish that lost its tail as post larva, including ten vertebrae, was able to reconstruct a novel and shorter central skeleton, including a specially modified urostyle. The enlarged and strengthened pterygiophores and their junctions with the dorsal and anal spine formed a fast‐holding base for the fins, the posterior part of which largely performed the functions of the missing caudal fin. Although the fish was much shorter than usual, this male behaved and functioned normally. © 1994 Wiley‐Liss, Inc.
Characteristics of the flagellar axoneme in Neuroptera, Coleoptera, and Strepsiptera
Authors: Afzelius Björn A. , Dallai Romano 
Published: February 2005

AbstractSpermatozoa from representatives of the five insect orders in superorder Neuropteroidea were examined by electron microscopy following a new fixation method that includes tannic acid in the primary fixative but has uranyl acetate rather than osmium tetroxide as the secondary fixative. The sperm axoneme was found to be similar in the four orders Megaloptera, Raphidioptera, Neuroptera, and Coleoptera, and is characterized above all by its so‐called intertubular material being divided into two portions, one located outside, but in contact with the doublet, and the other projecting from the accessory tubule and having a beak‐like shape. These features have not been seen in insects from other orders and may be a synapomorphy for these neuropteroid orders. The accessory tubules in these four orders have 16 protofilaments. The shape of the accessory bodies adjacent to the mitochondrial derivatives is nearly the same in insects from the more primitive neuropteroid orders and in Coleoptera. The sperm tail of the examined strepsipteran deviates in several respects from that of other neuropteroids: the particle row in the wall of accessory tubules is incomplete, an intertubular material is missing, and the mitochondria contain no crystal. © 1994 Wiley‐Liss, Inc.
Anatomy of the propatagium: The great horned owl (Bubo virginianus)
Authors: Brown Richard E. , Baumel Julian J. , Klemm Robert D. 
Published: February 2005

AbstractSkinfolds and feathers form the profile of the avian airfoil. The wing of birds has a nearly flat profile from shoulder to carpus, without the presence of the propatagium. The propatagium is the largest skinfold of the wing; it fills the angle formed by the partially flexed elbow, and with its feathers forms a rounded leading edge and dorsally cambered profile added to the cranial aspect of the wing. The propatagium is variably deployed, relative to elbow extension, in flight; support for its cambered shape is maintained by multilayered collagenous and elastic tissue networks suspended between leading edge and dorsal antebrachium. The leading edge ligament (Lig. propatagiale) courses from deltopectoral crest to carpus and, with its highly distensible center section, supports the leading edge of the propatagium across a range of wing extensions. The elbow extension limiting ligament (Lig. limitans cubiti) courses from deltopectoral crest to proximal antebrachium and limits maximum elbow extension. M. deltoideus, pars propatagialis inserts on the proximal end of the common origin of the propatagial ligaments and, by way of the insertions of the two ligaments, coordinates (1) automatic flexion / extension actions of the elbow and wrist, (2) propatagial deployment, and (3) tension along the length of Lig. propatagiale supporting the leading edge. © 1994 Wiley‐Liss, Inc.
Praesomal nerves in Corynosoma hamanni (Acanthocephala: Polymorphidae)
Authors: Gee Randall J. , Holloway Harry L. 
Published: February 2005

AbstractInvestigated by light microscopic observations, nerve pathways and the Stützzellle are described in the praesoma of a species of Corynosoma. The pathways are described for 13 nerves, 6 paired and one single nerve, which originate from the cerebral ganglion and terminate in the body wall musculature and the proboscis. © 1994 Wiley‐Liss, Inc.