bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphology and evolution of the ectethmoid‐mandibular articulation in the meliphagidae (Aves)
Authors: Bock Walter J. , Morioka Hiroyuki 
Published: February 2005

AbstractThe ectethmoid‐mandibular articulation in Melithreptus and Manorina (Meliphagidae: Aves) consists of the dorsal mandibular process fitting into and abutting against the ventral ectethmoid fossa; it forms a brace for the mandible. This articulation in Melithreptus is a typical diarthrosis with long folded capsular walls. The mandible, thus, has two separate articulations, each with a different axis of rotation. No other genus of Meliphagidae (except Ptiloprora) or any other avian family possesses a similar feature.The jaw and tongue musculature of Melithreptus are described. The two muscles opening the jaws are well developed, while those closing the jaws are small. The tongue muscles show no special developments.A large maxillary gland, presumably muscus secreting, covers the ventral surface of the jaw muscles. Its duct opens into the oral cavity just behind the tip of the upper jaw. The frilled tip of the tongue rests against the duct opening.The ectethmoid‐mandibular articulation braces the adducted mandible against dorsoposteriorly directed forces. The mandible can be held closed without a compression force exerted by the mandible on the quadrate, permitting the bird to raise its upper jaw with greater ease and less loss of force. The tongue can be protruded through the slight gap between the jaws, moving against the duct opening and thus be coated with mucus. Presumably, these birds capture insects with their sticky tongue. Hence, the ectethmoid‐mandibular articulation is an adaptation for this feeding method; it evolved independently in three genera of the Meliphagidae.The ectethmoid‐mandibular articulation demonstrates that a bone can have two articulations with different axes of rotation, that the two articular halves can separate widely, and that articular cartilages can be flat and remain in contact over a large area. Its function suggests that the basitemporal articulation of the mandible found in many other birds has a similar function. And it demonstrates that in the evolution of the mammalian dentary‐squamosal articulation, the new hinge did not have to lie on the same rotational axis as the existing quadrate‐articular hinge.
The light and the electron microscopic studies of Peyer's patches in non germ‐free adult mice
Authors: Sobhon Prasert 
Published: February 2005

AbstractPeyer's patches of conventional adult mice are studied with light and electron microscopy. Based on cellular types and distribution, each lymphoid follicle of Peyer's patch is divisible into four zones: the germinal center, the small lymphocytic, the interfollicular and the subepithelial zones. Three distinct cell types are present in the germinal center, i.e., dendritic reticular cells; tingible body macrophages; and lymphocytes which are classifiable into large, medium and small size. The medium size lymphocytes are the great majority in this zone. The small lymphocytic zones are characterized by a predominance of small lymphocytes with a few reticular cells. The subepithelial zone has a remarkable accumulation of macrophages and plasma cells. In the interfollicular zones there are predominantly small lymphocytes with considerable round macrophages and plasma cells, and this zone is permeated with several post‐capillary venules. The distinctive characteristics of small capillaries of the patches are also described.
Aspects of the circulatory system of Pollicipes polymerus J. B. Sowerby (Cirripedia: Thoracica)
Authors: Burnett Bryan R. 
Published: February 2005

AbstractThe circulatory system of Pollicipes polymerus exhibits a high degree of organization which precludes it from being referred to as an open system. The system is arbitrarily divided into four parts: (1) the circulation of the peduncle and mantle; (2) the distributive circulation of the body, which provides hemolymph to most of the cephalic gut, to the maxillary gland, and to the cirri; (3) the peripheral circulation which distributes blood from the cirri to the peripheral areas of the thoracic region, to most of the thoracic gut, and from the scutal sinus to the peripheral areas of the cephalic region; and (4) the collecting circulation, which conveys hemolymph mostly from the peripheral circulation of the body to the peduncle. There also may be a circulation that is comparable to the vertebrate lymphatic system.Pumping of hemolymph can be attributed to three pairs of skeletal muscles that compress the dorsolateral channels. These muscles are unique for crustacean muscles in that they do not appear to be striated.The rostral vessel appears to be a vestige of a heart in which the pump muscles have been lost. There is a similarity of the rostral vessel to the heart of Calanus finmarchicus (a copepod). This is additional evidence linking the cirripeds with the copepods within the Maxillopoda.Electron microscope observations of the walls of the midsagittal vessels indicate that there is a more or less random layering of cellular and noncellular elements within the wall. Muscle cells appear to be incorporated in the vessel wall.
Ultrastructural contributions to the identification of cell types in the lizard epidermal generation
Authors: Maderson P. F. A. , Flaxman B. A. , Roth S. I. , Szabo G. 
Published: February 2005

AbstractThe ultrastructure of the epidermis at different stages of the shedding cycle has been studied in Anolis carolinensis. Cells of the germinal layer are morphologically similar at all stages in the cycle. Immediately after leaving the germinal layer all daughter cells resemble one another closely. However, they later acquire specific ultrastructural features that enable them to be classified into six distinct fully differentiated types corresponding to the grouping previously set forth by light microscopy. A comparison of cytoplasmic filament size with the known X‐ray diffraction data suggests that the Oberhautchen and β‐layer contain a protein similar to that of avian feather; the protein in the α‐layer and lacunar tissue is similar to that in mammalian hair, and the mesos layer cells probably contain a mixture of feather and hair‐like proteins. The nature of the amorphous cytoplasmic material in the mature clear layer is as yet unknown.
The early development of substrate‐brooding cichlids (Teleostei: Cichlidae) with a discussion of a new system of staging
Authors: Jones A. J. 
Published: February 2005

AbstractThe early development of five species of substrate‐brooding cichlid (Aequidens pulcher; Cichlasoma bimaculatum; C. biocellatum; C. nigrofasciatumandHemichromis bimaculatus) is described. Heterochrony in these species renders the standard system of staging inadequate for comparative study. A new system is proposed in which the period of development is resolved into five overlapping phases, each phase corresponding to a dissociable ontogenetic process. This form of staging permits comparison in a way which neither obscures the basic uniformity of cichlid development nor masks the differences between the species.Two special features are discussed: the universal presence in substrate‐brooding cichlids of three pairs of embryonic adhesive organs; and the apparent presence of non‐neural crest pigment on the embryos and alevins.
Tail regeneration following autotomy in the adult salamander Desmognathus fuscus
Authors: Mufti Shahzad A. , Simpson S. B. 
Published: February 2005

AbstractTail regeneration occurs following autotomy of the tail in the salamander Desmognathus fuscus. Studies based on histology and autoradiography suggest that the cells of the regeneration blastema arise from the connective tissue of the tail stump. Following autotomy of the tail in Desmognathus the muscle of the regenerate is not derived from de differentiated or modulated striated muscle fibers of the autotomy stump. Possible sources of myogenic cells are discussed.
Effects of ovariectomy and steroid replacement on the genital tract of the viviparous lizard, Xantusia vigilis
Authors: Yaron Z. 
Published: February 2005

AbstractTwo glandular components are described in the genital tract of Xantusia: tubal glands in the Fallopian tube and goblet cells in the uterine villi. Sperm or seminal receptacles occur between adjacent villi in the uterus.Forty ovariectomized lizards carrying a silk loop in the wall of the left uterus were treated for two weeks with either progesterone, estradiol‐17 β, progesterone plus estradiol or vehicle. Uteri with loops serving as a local irritant, did not differ significantly from the contra‐lateral uteri in any group, hence a response similar to the deciduomal reaction of mammals is not found in this lizard.The weight of the genital tract is similar in sham‐operated and in ovariectomized lizards injected with either progesterone or the vehicle. Maximal increase in weight of the tract is noted with estradiol treatment, while simultaneous administration of both steroids is followed by a moderate increase of oviducal weight. Tubal glands and sperm receptacles in ovariectomized lizards injected with either the vehicle or progesterone are smaller than those of the sham‐operated or ovariectomized lizards treated with estradiol or with estradiol plus progesterone. Goblet cells are small and lack secretory granules in ovariectomized lizards injected with either the vehicle, or with estrogen or progesterone alone. Both steroids, given together, restore the size and apparent secretory activity of the goblet cells. It is concluded that in this viviparous species, both estrogen(s) and progestin(s) are essential for the maturation of the genital tract in the preovulatory stage.
Macrophage activity in wolffian lens regeneration
Authors: Yamada T. , Dumont James N. 
Published: February 2005

AbstractThe cell type mainly involved in the phagocytic uptake of melanosomes from iris epithelial cells during Wolffian lens regeneration in the adult newt is identified on the basis of electron and light microscopic evidence as a macrophage of monocytic origin. Appearance of macrophages in iris and ciliary epithelia following lentectomy is a part of leucocytic infiltration of the area, in which granulocytes, mast cells, and other cell types also participate. The general pattern of leucocytic infiltration was studied as a function of time after lentectomy. Infiltration of the iris epithelium by macrophages is reduced when most of the melanosomes have been removed from the cytoplasm of the epithelial cells and finally ceases when depigmentation has been completed. The possibility that an immune mechanism mediated by macrophages is involved in dedifferentiation of iris epithelial cells is discussed.
Mastication in the little brown bat, Myotis lucifugus
Authors: Kallen Frank C. , Gans Carl 
Published: February 2005

AbstractThe masticatory apparatus of the vespertilionid bat Myotis lucifugus appears generalized. Principal modifications for more efficient trituration have involved accessory tooth cusps. Chewing strokes pass through orbits (up to 7/sec) involving translations along and rotation about three axes. Direction of chewing typically reverses by at least the fifth or sixth consecutive orbit. Reversal involves modification of the downstroke at varying positions along its course. Compared to certain other bats, which do not utilize oral phonation for echolocation, Myotis chews much more rapidly, with many more degrees of freedom in orbital configuration. The overall envelope of motion is remarkably similar in all these species. The jaw muscles of Myotis act asymetrically, and in more than one direction as the orbit progresses. They overlap in their periods of activity forming a continually‐modified muscular sling. Unilateral force couples facilitate orthal rotation at the condyles and movements of them. Bilateral couples, pitting protrusors of one side against retrusors of the other, facilitate lateral translation. The pterygoids are instrumental in continuing motion across the top and bottom of the orbit. Countercontractions are particularly important in stabilizing and protecting the temporomandibular joints. The mandibular symphyseal joint appears to act passively, providing additional flexibility for the system. Higher nervous control beyond the simple jaw‐opening reflex appears necessary to explain the firing order of the digastrics and the phase relationship of orbital reversal to overall muscular firing intensity. Control mechanisms, ancillary phenomena and comparative aspects are discussed.
Secretion by ependymal cells of the neurohypophysis and saccus vasculosus of Polypterus ornatipinnis (osteichthyes)
Authors: Marquet Eugene , Sobel Harold John , Schwarz Ruth , Weiss Martin 
Published: February 2005

AbstractElectron microscopic studies of the neurohypophysis and saccus vasculosus of the bichir (Polypterus ornatipinnis) reveal an apocrine release of secretory material by ependymal cells (e.g., crown cells). The secretory material appears to migrate along the microtubular apparatus and the ciliary filaments to the cell buds. It is postulated that the formation of the buds and their release is mediated by cilial action. Secretion buds are noted in the cerebrospinal fluid and vascular sinusoids.Bulbous projections of neurohypophyseal secretory tracts extend into the ependymal lumen which also contains elementary secretion granules. Specialized “liquorkontaktneurone” are interspersed with ependymal cells.An interrelation between the hypothalamus, neurohypophysis, saccus vasculosus, and the meta‐adenohypophysis is postulated.
The relationship of early oocytes to putative neoblasts in the serpulid Spirorbis borealis
Authors: Potswald Herbert E. 
Published: February 2005

AbstractThe fine structure of the ovary in the serpulid Spirorbis borealis has been described. The ovarian wall consists of from one to several layers of peritoneal cells. Peritoneal cell processes extend deep into the ovary and may be seen between developing oocytes. Although young oocytes may also be in close apposition to one another, intercellular bridges have not been observed. When primary oocytes at the surface of the ovary reach a diameter of about 20 μ, they start to erupt into the coelom. Ovulation results from a simple separation of overlying peritoneal cells which lack specialized cell‐to‐cell contacts. Once a free surface of an ovulating oocyte is exposed to the coelom, microvilli and primary coat develop. Previtellogenic coelomic oocytes are often observed in close proximity to putative neoblasts (perivasal cells), which suggests a possible functional relationship. The confusion that extists between germ cells, peritoneal cells, and so‐called neoblasts in polychaetes is discussed.
A new model for the structure of the centriolar satellite complex in spermatozoa
Authors: Summers Robert G. 
Published: February 2005

AbstractThe ultrastructure of the centriolar satellite complex in the spermatozoon of the hydroid, Pennaria, is presented. The complex consists of nine spoke‐like arms which emanate from the distal centriole and of nine wedgeshaped connectives which extend into the flagellum joining each of the alpha doublets and the flagellar plasmalemma. Based upon these observations a new model for the structure of the centriolar satellite complex is proposed. In addition, similar centriolar satellite complexes are reported in the spermatozoa of two echinoderms, Ctenodiscus crispatus and Thyone briareus, in support of the proposed model.
The anatomy and histology of the nasal cavities and the nasal salt gland in four species of fringed‐toed lizards, Acanthodactylus (Lacertidae)
Authors: Duvdevani Israel 
Published: February 2005

AbstractThe anatomy of the nasal cavities and lateral nasal gland (functioning as a salt gland) are similar in the four species of Acanthodactylus studies. Nasal cavities are not histologically different from those of other squamates. The vestibule is covered with a multilayered, stratified, squamous epithelium. The nasal gland is situated in the conchal space, lateral to the principal cavity and the vestibule. It is a tubular branched gland, highly vascularized. Innervation is derived from the N. trigeminus and was observed to reach only the anterior, small portion of the gland. The collecting duct opens to the vestibule, anterior to its connection to the principal cavity. Secretion of the nasal salt gland probably collects in lower anterior part of the vestibule. From there, liquid can either dry out while moistening the inspired air or be blown out by “sneezing.” Histological differences were observed between a non‐active and an active salt gland.
A cytological study of the ovary of Rhodnius prolixus. II. Oocyte differentiation
Authors: Huebner Erwin , Anderson Everett 
Published: February 2005

AbstractThis investigation presents the ultrastructural changes that occur during previtellogenic and vitellogenic growth of the oocyte of a telotrophic ovary. The ovarioles of a newly emerged adult Rhodnius have their full complement of oocytes located at the base of the tropharium. These oocytes are in cytoplasmic continuity with the syncytial tropharium via trophic cords. The nuclei of these oocytes are in prophase of meiosis I with condensed chromosoes; synaptonemal complexes are visible in many. During oocyte growth the nucleus or germinal vesicle enlarges from a 3–4 μ diameter to a 45–50 μ diameter and the chromosomes become diffuse and arrested in late prophase I. Small previtellogenic oocytes are limited by a morphologically unspecialized oolemma and contain a pair of centrioles, rough endoplasmic reticulum, a few small Golgi complexes and clusters of mitochondria. By the end of previtellogenesis there has been an increase in the volume of the oocyte due to the transport of ribosomes and mitochondria into the oocyte from the tropharium. During vitellogenesis the oolemma develops a microvillous border and yolk precursors are internalized by pinocytosis. Small stacks of annulate lamellae, numerous ribosomes and the other organelles are restricted to the thin layer of cortical ooplasm; the lipid protein‐carbohydrate yolk spheres and glycogen are located centrally. In oocytes not stimulated, autolysis occurs as dense local areas within the ooplasm.
The anatomy, physiology, functional significance and evolution of specialized hearing organs of gerbilline rodents
Authors: Lay Douglas M. 
Published: February 2005

AbstractMiddle and inner ear anatomy correlates with neurophysiological responses to a wide range of sound frequencies for species of the Gerbillinae representing generalized, intermediate, and specialized anatomical conditions. Neurophysiological data were recorded from 81 specimens of 13 species representing six genera. Anatomical parameters involved in the process of hearing were correlated with the neurophysiological data to assess the effects of different degrees of anatomical specialization on hearing. The 13 species tested in this manner have graphic curves of auditory sensitivity of remarkably similar disposition over the frequencies tested and to those published for Kangaroo Rats. Ears with anatomical specializations show greater auditory sensitivity.The natural history of the Gerbillinae, particularly the kinds of predators, degree of predation, and habitat is reviewed and utilized to interpret the significance of the degree of auditory specialization in the forms studied and to evaluate the prevailing hypothesis that these specializations enhance the ability of these rodents to survive in open desert situations by detecting and evading predators.The middle ear anatomy of five additional genera and species was also studied. Thus, data on the entire spectrum of gerbilline middle ear morphology provide an evolutionary sequence. Certain anatomical parameters of the organ of Corti show a degree of specialization parallel to that of features of the middle ear. The morphological changes and possible functional roles of these features are considered.A very high correlation exists for degree of specialization and aridity of habitat, thus specialization increases with increasing aridity. This increased specialization may result from more effective predation in open xeric environments. Auditory acuity for a wide range of low frequency sounds augmented by auditory specialization is hence more advantageous here. There does not appear to be selection for hearing at particular frequencies in this range. The peaks of greatest auditory sensitivity appear to correspond to the resonant frequencies of the different components of the middle ear transformer and cavity.
Embryology of the sheep. II. The alimentary tract and associated glands
Authors: Bryden M. M. , Evans Howard E. , Binns Wayne 
Published: February 2005

AbstractThe day‐by‐day development of the alimentary system of the sheep embryo from 14 to 34 days is documented and described. This includes development of the mouth, the pharynx and its derivatives, esophagus, stomach, intestine, cecum, pancreas and liver.This work provides standards within the normal range of development of the ovine alimentary system on which studies of abnormal development can be based.
Lymphoid tissue in the snapping turtle, Chelydra serpentina
Authors: Borysenko M. , Cooper E. L. 
Published: February 2005

AbstractThis report presents light microscopic descriptions of lymphoid organs and aggregates in the snapping turtle Chelydra serpentina. The thymus and spleen were found to be similar to those of other ectothermic vertebrates. Certain gut associated lymphoid aggregates suggest the presence of reptilian equivalents of tonsils, Peyer's patches and the avian bursa of Fabricius. Lymphoid aggregates located in the axillary and inguinal regions were apparent for the first time in an ectothermic vertebrate. These are of particular interest since they may represent ancestors of true lymph nodes in analogous locations in mammals. It is concluded that the snapping turtle is not deficient in lymphoid tissue, although there is a conspicuous absence of typical germinal centers, characteristic of mammalian organs.
Development of polarity and bilateral asymmetry in the palleal bud of Botryllus schlosseri (Pallas)
Authors: Izzard Colin S. 
Published: February 2005

AbstractThe development of the polarity and bilateral asymmetry of the future adult zooid has been traced to their earliest morphological expression in the palleal bud of Botryllus. The account is based upon continued observation of living buds. The polarized antero‐posterior and dorso‐ventral axes are first expressed by the skewing of a symmetrical, hemispherical bud towards the anterior end of the parental bud. Identification of these axes is reinforced by the development of a loop‐like blood circulation, the primary circulation, in the horizontal plane during the enlargement of the skewed hemisphere to form a stalked vesicle. Bilateral asymmetry is first expressed by the asymmetrical expansion of the vesicle stage. The right posterior corner of the vesicle expands further posteriorly and becomes more acute than the left posterior corner. This larger expansion persists throughout the development of the right atrial cavity, which finally expands across the mid‐line to partially surround the gut. The bilateral asymmetry, expressed in the expanded vesicle, is reinforced by the development in sequence of a rounded gut rudiment and a pericardial rudiment in positions that would be expected from the asymmetry of the expanded vesicle. The first appearance of the gut rudiment occurs earlier than had been recognized previously. Conflicting accounts of the time and mode of formation of the pericardial rudiment have been clarified. The results of this study are discussed in the context of determination of bud territory, polarity and bilateral asymmetry.