bluuebunny/crossref_metadata_2025_split huggingface dataset:
Corneal morphogenesis in the Indian garden lizard, Calotes versicolor (agamidae)
Authors: Shinde S. L. , Goel Suresh C. 
Published: February 2005

AbstractThe present study traces corneal morphogenesis in a reptile, the lizard Calotes versicolor, from the lens placode stage (stage 24) until hatching (stage 42), and in the adult. The corneal epithelium separates from the lens placode as a double layer of peridermal and basal cells and remains bilayered throughout development and in the adult. Between stages 32– and 33+, the corneal epithelium is apposed to the lens, and limbic mesodermal cells migrate between the basement membrane of the epithelium and the lens capsule to form a monolayered corneal endothelium. Soon thereafter a matrix of amorphous ground substance and fine collagen fibrils, the presumptive stroma, is seen between the epithelium and the endothelium. Just before stage 34 a new set of limbic mesodermal cells, the keratocytes, migrate into the presumptive stroma. Migrating limbic mesodermal cells, both endothelial cells and keratocytes, use the basement membrane of the epithelium as substratum. Keratocytes may form up to six cell layers at stage 37, but in the adult stroma they form only one or two cell layers. The keratocytes sysnthesize collagen, which aggregates as fibrils and fibers organized in lamellae. The lamellae become condensed as dense collagen layers subepithelially or become compactly organized into a feltwork structure in the rest of the stroma. The basement membrane of the endothelium is always thin. Thickness of the entire cornea increases up to stage 38 and decreases thereafter until stage 41. In the adult the cornea is again nearly as thick as at stage 38.
Aspects of masticatory form and function in common tree shrews, Tupaia glis
Authors: Fish Dale R. 
Published: February 2005

AbstractTree shrews have relatively primitive tribosphenic molars that are apparently similar to those of basal eutherians; thus, these animals have been used as a model to describe mastication in early mammals. In this study the gross morphology of the bony skull, joints, dentition, and muscles of mastication are related to potential jaw movements and cuspal relationships. Potential for complex mandibular movements is indicated by a mobile mandibular symphysis, shallow mandibular fossa that is large compared to its resident condyle, and relatively loose temporomandibular joint ligaments. Abrasive tooth wear is noticeable, and is most marked at the first molars and buccal aspects of the upper cheek teeth distal to P2. Muscle morphology is basically similar to that previously described for Tupaia minor and Ptilocercus lowii. However, in T. glis, an intraorbital part of deep temporalis has the potential for inducing lingual translation of its dentary, and the large medial pterygoid has extended its origin anteriorly to the floor of the orbit, which would enhance protrusion. The importance of the tongue and hyoid muscles during mastication is suggested by broadly expanded anterior bellies of digastrics, which may assist mylohyoids in tensing the floor of the mouth during forceful tongue actions, and by preliminary electromyography, which suggests that masticatory muscles alone cannot fully account for jaw movements in this species.
Muscles of the masticatory apparatus in two genera of hyraces (Procavia and Heterohyrax)
Authors: Janis Christine M. 
Published: February 2005

AbstractSubungulate hyraces are similar to the condition assumed to have characterized primitive ungulates and subungulates by virtue of their small body size, relatively unspecialized cranial and postcranial anatomy, and primitive type of lophodont dentition. The muscles of mastication of Procavia habessinica and Heterohyrax brucei are here compared with those of other mammals, both with ungulates, as an example of more specialized mammals, and with opossums, as an example of more generalized mammals, to determine aspects of hyrax myology that represent the retention of a condition primitive for herbivorous mammals.The masticatory muscles of hyraces retain the primitive ungulate/subungulate condition in the large, complexly subdivided temporalis, and in the enlarged, pinnated, bilayered medial pterygoid. The medial pterygoid originates from the pterygoid hamulus, a condition that may also be primitive for this assemblage. The large complex superficial masseter is derived compared with the condition in ruminant artiodactyls, but may represent the condition primitive for perissodactyls. The architectural modifications of this muscle in hyraces may represent adaptations to allow a wide gape threat display.Hyraces possess a posterior belly of the digastric alone, paralleling the condition in some perissodactyls. They possess a large and complexly subdivided styloglossus, which may be a shared derived character of subungulates. Hyraces are unique among ungulates and subungulates in the extreme reduction of the anterior hyoid cornua, and may be unique among mammals in the development of paired lingual processes from the ceratohyal ossifications.
Ultrastructure of the exocrine pancreas in a sahelian reptile (Varanus exanthematicus) during starvation
Authors: Godet Rene , Mattei Xavier , Dupé‐Godet Mireille 
Published: February 2005

AbstractDuring the sahelian dry season (November to June) the lizard Varanus exanthematicus fasts, and during these 8 months its pancreatic acinar cells lack zymogen granules and show an inactive Golgi body and damaged mitochondria. The main peculiarity can be observed in the granular endoplasmic reticulum (GER): Each acinar cell posesses a great number of GER vesicles (mean diameter 0.15 μm) and a large spheroid GER resulting from either the nesting of some cisternae or the rolling up of a single cisternae on itself. Attention is focused on the possible relationship between this ultrastructure and alteration of protein metabolism.
Cytological study of the cellular changes after transection of the proximal radix of the rat trigeminal ganglion
Authors: Sugiura Yasuo , Kitoh Junzoh , Sakai Hisashi 
Published: February 2005

AbstractCytological changes following transection of the proximal root of the trigeminal ganglion in adult rats were assessed by light and electron microscopy. Radices were transected about 3–5 mm from the ganglia and animals were killed from 1 to 60 days after the operation. Light microscopically, it was found that all Nissl granules became uniformly stained and evenly distributed throughout the cytoplasm within 3 days. Three types of cell alteration involving Nissl granules occurred within 3 to 12 days after the operation: (1) chromatolysis, (2) dark staining of the cytoplasm accompanied by an increase of Nissl granules, and (3) faint staining of the cytoplasm accompanied by dispersion of Nissl granules. Electron microscopically, the chromatolysis pattern was characterized by peripheral concentration of the granular endoplasmic reticulum (gER) and ribosomes in the cytoplasm. Neurons of the darkstaining type showed an increased number of polysomal complexes throughout the cytoplasm, whereas those of the faint‐staining type had diffusely dispersed cisternae of the gER which were shortened and bore reduced numbers of attached ribosomes. Perinuclear localization of profiles of Golgi complexes disappeared temporarily 1–3 days after the operation, but the normal perinuclear pattern appeared to return after 1 week. Enzyme histochemistry of acid phosphatase activity revealed an increase in the number of very fine reaction products in the cytoplasm up to 14 days following the operation. Cells recovered the normal pattern of Nissl staining by 48 days. Myelin figures, which are rarely observed in normal ganglia, were still observed in dense lysosomal bodies after 30 days. Nuclear size in affected neurons steadily increased up to about 2 weeks postoperation but returned to normal by 48 days.
Ultrastructure of the adenohypophysis in the larval anadromous sea lamprey, Petromyzon marinus L.
Authors: Wright Glenda M. 
Published: February 2005

AbstractThe ultrastructure of the adenohypophysis (AH) in the larval anadromous sea lamprey, Petromyzon marinus L., was examined. The AH is subdivided into three regions, the pro‐, meso‐, and meta‐AH. Cells of the nasopharyngeal stalk extend directly beneath the pro‐ and meso‐AH to form the ventral surface of the gland. Some cells in the pro‐ and meso‐AH are arranged into small follicles. Each region of the AH is characterized by a single granulated (secretory) cell type. Granulated cells constitute 80–90% of the pro‐AH and contain secretory granules that range from 800 to 2400 Å in diameter. Only 10–20% of the cells in the meso‐AH are granulated and they contain much smaller secretory granules (400 to 1250 Å diameter) than those in the pro‐AH. Granulated cells constitute 80–90% of the meta‐AH and contain only a few secretory granules, ranging from 1000 to 2500 Å in diameter, and many vesicles containing either a loose flocculent or dense granular material. Nongranulated (stellate) cells are found in all regions. They are characterized by their long cell processes, abundant cytoplasmic filaments, and variable electron density. The appearance of organelles in these cells suggests they are nonsecretory. They may play a role in maintaining the structural integrity of the gland and the regulation of granule release in the pro‐AH. Two types of nongranulated cells make up 80–90% of the meso‐AH. Type I are stellate cells, type II may be undifferentiated cells. The functional significance of the secretory cells in the larval AH is discussed.
Fine structure of the thymus in the adult cling fish Sicyases sanguineus (Pisces, Gobiesocidae)
Authors: Gorgollon Pedro 
Published: February 2005

AbstractThe structure of the thymus in adult specimens of a marine teleost, the cling fish Sicyases sanguineus, has been studied by light and transmission electron microscopy. Most cling fishes have an outer thymus located beneath the opercular epithelium. A few of them, however, have a large inner thymus besides a poorly developed outer thymus. In the well‐developed outer thymus of cling fish there are three differnt zones: outer cortex, inner cortex, and medulla. The inner cortex is similar to the cortical region of the thymus in other vertebrates, whereas the outer cortex is a specialized lympho‐ephthelial zone containing cystic cells (also present in medullary region) and true Hassall's corpuscles. In accordance with the development of the thymic parenchyma, the medullary or basal region may appear either like a true thymic medulla or like a subcapsular region. In the inner thymus, a subcapsular or peripheral “medullary” region and a central area (inverted cortex) show structural features like those of the medullary (basal) and deep cortical regions of the outer thymus, respectively. In addition to the above regions, sometimes there is a lymphomyeloid perithymic infiltration that often extends along connective tissue septa into the perivascular spaces of the gland. Reticuloepithelial, mesenchymal, and unidentified types of stromal cells within the thymus are described. Some erythrocytes, granulocytes, and monocytoid cells are found, but no plasma cells nor erythropoietic foci are evident. The probable significance of these findings is discussed.
Muscle fiber types and functional demands in feeding mechanisms of fishes
Authors: Ono R. Dana , Kaufman Les 
Published: February 2005

AbstractProfiles of muscle fiber types and pharyngeal jaw dentition vary in accordance with trophic demands and skeletal organization in teleost fishes. Carnivorous, omnivorous, and molluscivorous members of the ecologically analogous Cichlidae and Centrarchidae were compared in terms of their pharyngeal jaw anatomy and branchial muscle histochemistry. The two families differed greatly in patterns of tooth form, wear, and replacement. Four muscle fiber type patterns were discoverd: (1) single fiber, (2) zoned, (3) mosaic, and (4) zoned‐mosaic. Multiple fiber type muscles were more prevalent in fishes that masticate tough foods with their pharyngeal jaws. Such muscles were also more prevalent in cichlids than in centrarchids. It appears that muscles with multiple fiber types in lower vertebrates are, as a rule, compartmentalized, whereas in higher vertebrates, multiple fiber type muscles are a musaic matrix. The occurrence of mosaic patterns in some fish branchial muscles, however, suggests that mosaic muscles are initially single fiber type muscles exposed to complex functional demands, such as food preparation. Furthermore, it is plausible that the evolutionary replacement of the lower vertebrate zoning pattern by the higher vertebrate mosaic matrix is directly related to the effects of gravity, a force more influential on terrestrial than on aquatic organisms.
The ultrastructure of venom‐producing cells in Paranemertes peregrina (Nemertea, Hoplonemertea)
Authors: Stricker Stephen A. , Cloney Richard A. 
Published: February 2005

AbstractThe nemertean Paranemertes peregrina uses its long, eversible proboscis to capture nereid polychaetes. During prey capture, the glandular epithelium of the everted proboscis secretes a sticky venom that contains a potent neurotoxin. In this study, the ultrastructure of the venom‐producing epithelium is examined before and after capture of nereid prey. Four types of cells can be distinguished in the glandular epithelium, based on the shape and staining properties of their secretory products. The cells contain fusiform or coalescent types of rhabdoids, acidophilic granules, or flocculent material. All four cell types occur in the anterior part of the proboscis, but only cells with acidophilic granules have been observed in the posterior chamber. The glandular epithelium of the anterior chamber secretes sheets of venomous mucus that are composed of the four types of secretory products fused together, while the epithelial cells of the posterior chamber produce a granulated discharge. Cells that contain flocculent material also occur in the epidermis of P. peregrina. The flocculent material is believed to contain the toxic component of the venom, as its distribution in the anterior proboscis chamber and body wall correlates with previous reports of toxin concentrations that were derived from assays of tissue extracts.
Morphological changes in the liver of the sea lamprey, Petromyzon marinus L., during metamorphosis: I. Atresia of the bile ducts
Authors: Sidon E. W. , Youson J. H. 
Published: February 2005

AbstractThe bile ducts in the liver of larval sea lamprey, Petromyzon marinus, undergo programmed degeneration during metamorphosis. The degenerative process is most dramatic in the middle metamorphic stages (3–5), and is asynchronous, occurring more rapidly in small peripheral biliary components than in larger, medial ducts. All classes of bile ducts within the biliary tree exhibit similar histological changes during regression.The initial evidence of degeneration in the epithelium is a folding of the basal lamina, and this is accompanied by cell shrinkage and disruption of cell order. “Shedding” of microvilli and cytoplasmic constituents then takes place at the apical surface resulting in the accumulation of periodic acid‐Schiff positive membranous debris in the lumen. The apperance of “hyalin bodies” in the lumen coincides with the depletion of intermediate‐sized filaments from the cytoplasmic matrix. Numerous, large dense bodies, myelin figures, and autophagic vacuoles are consistently observed in necrotic cells. Following cytolysis, bile duct remnants become ensheathed within regions of fibrosis. Ultimately, these fibrous regions are replaced with cords of hepatocytes. By stage 7, all bile ducts have disappeared.The events of biliary atresia in lampreys are comparable to tissue regression which is associated with normal development and pathological conditions in other vertebrates but are particularly reminiscent of those in human biliary atresia. The unique ability of the adult lamprey to survive without bile ducts enhances the value of this organism as an experimental model for studying human biliary atresia.
Mechanisms of rapid morphogenetic movements in the metamorphosis of the bryozoan Bugula neritina (Cheilostomata, Cellularioidea): II. The role of dynamic assemblages of microfilaments in the pallial epithelium
Authors: Reed Christopher G. , Woollacott Robert M. 
Published: February 2005

AbstractThe rapid morphogenetic movements that internalize the transitory larval epithelium and reorient the presumptive adult epidermis during the metamorphosis of the cellularioid cheilostome bryozoan, Bugula neritina, have been examined by light and electron microscopy and analyzed by experimentation with cytochalasin B (CB) and MgC12. The pallial epithelium is gradually drawn out over the aboral hemisphere as the larval ciliated epithelium (the corona and the pyriform organ) involutes. At the end of coronal involution the oral margin of the pallial epithelium constricts and the aboral hemisphere is pulled down against the everted sac. Ultrastructural and experimental evidence indicates that an equatorial contractile ring composed of a temporal alignment of CB‐sensitive 5.5 nm microfilaments is responsible for the constriction of the oral margin of the pallial epithelium. This morphogenetic movement, in conjunction with the compression of the aboral hemisphere, juxtaposes the pallial epithelium with the oral epithelium of the everted sac. The pallial epithelium adheres to the neck and wall regions of the everted sac and begins a progressive contraction at its aboral margin, pulling the wall epithelium up over the aboral hemisphere. Ultrastructural examination reveals that the pallial cells contain apical bands of microfilaments and associated vesicles at this stage of metamorphosis. The position and time of appearance of the microfilaments in the pallial epithelium support the hypothesis that they generate the force for wall elevation. Histological and experimental data indicate that the compression of the aboral hemisphere at the umbrella stage and the final retraction of the apical disc are muscle‐mediated morphogenetic movements. The constriction of the umbrellar margin and the elevation of the wall epithelium, on the other hand, appear to be caused by two distinct populations of microfilaments that assemble in different regions of the pallial epithelium at specific times during metamorphosis.
Anatomy of external structure and musculature of abdominal segments in the larva of the lepidopteran Pieris rapae crucivora
Authors: Tsujimura Hidenobu 
Published: February 2005

AbstractThe external structure of the 1st (AS1) and 4th abdominal segments (AS4) of Pieris rapae is described in terms of pattern of shallow grooves on the cuticle. Both segments have 5 dorsal costae, 3 ventral costae, and an antero‐posterior line in addiction to the dorsal and ventral intersegmental folds and a spiracle. AS4 has a pair of prolegs. The musculatures of AS1 and AS4 consist of 44 and 51 muscles, respectively. As in thoracic ones, most attachments of the muscles are located on the cuticular grooves. AS1 and AS4 have similar musculatures. Common to both segments are 89% of AS1 muscles and 84% of AS4 muscles. AS1 has 6 muscles homologous to proleg ones of AS4, including proleg retractors and plantar retractors. Comparison of the musculature of proleg‐bearing abdominal segments among different species shows that abdominal musculature of lepidopteran larvae has major homologous and minor specific muscles. From the muscle attachment sites, the role of each muscle is inferred for contraction and bending of the body, lifting up its venter, taking off the crockets from the substrate, and retraction, lateral abduction, and anterior movement of the proleg.
Miniaturization and its effects on cranial morphology in plethodontid salamanders, genus Thorius (Amphibia, Plethodontidae): II. The fate of the brain and sense organs and their role in skull morphogenesis and evolution
Authors: Hanken James 
Published: February 2005

AbstractRelative size and arrangement of the brain and paired sense organs are examined in three species of Thorius, a genus of minute, terrestrial salamanders that are among the smallest extant tailed tetrapods. Analogous measurements of representative species of three related genera of larger tropical (Pseudoeurycea, Chiropterotriton) and temperate (Plethodon) salamanders are used to identify changes in gross morphology of the brain and sense organs that have accompanied the evolution of decreased head size in Thorius and their relation to associated changes in skull morphology.In adult Thorius, relative size (area measured in frontal plane, and length) of the eyes, otic capsules, and brain each is greater than in adults of all of the larger genera; relative size of the nasal capsules is unchanged or slightly smaller. Interspecific scaling phenomena–negative allometry of otic capsule, eye and brain size, isometry or slight positive allometry of nasal capsule size, all with respect to skull length–also are characteristic of intraspecific (ontogenetic) comparisons in both T. narisovalis and Pseudoeurycea goebeli.Predominance of the brain and eyes in Thorius results in greater contact and overlap among these structures and the nasal capsules in the anterior portion of the head. This is associated with anterior displacement of both the eyes and nasal capsules, which now protrude anterior to the skull proper; a change in eye shape; and medial deformation of anterior braincase walls. Posteriorly, predominance of the otic capsules has effected a reorientation of the jaw suspensorium to a fully vertical position that is correlated with the novel presence of a posteriorly directed squamosal process and shift in origin of the quadropectoralis muscle.Many of these changes in cranical morphology may be explained simply as results of mechanical (physical) interactions among the skeletal, nervous, and sensory components during head development at reduced size. This provides further evidence of the role of nervous, sensory, and other “soft” tissues in cranial skeletal morphogenesis, and reinforces the need to consider these tissues in analyses of skull evolution.
Comparative and functional morphology of the stomach in the adult and newborn pigmy hippopotamus(Choeropsis liberiensis)
Authors: MacDonald Alastair A. , Hartman Wrister 
Published: February 2005

AbstractExamination of the topographical anatomy of the stomach complex and intestinal tract of an adult male and a newborn female pigmy hippopotamus (Choeropsis liberiensis) shows that the stomach consists of four chambers, the first three constituting the proventriculus and the fourth the glandular stomach. The proventriculus is made up of a visceral and parietal blind sac opening into a connecting chamber, which in turn opens into the glandular compartment. The walls of the proventricular chambers are covered with villi and non‐glandular mucous membrane. The significant difference between the animals is that whereas the connecting chamber of the adult stomach lies transversely deep in the cranial part of the abdomen and connects with the glandular chamber on the right side, that of the newborn lies almost vertically and connects ventrally with the glandular compartment situated on the floor of the abdomen. A groove which in the adult runs more or less horizontally from the cardia through the visceral sac and connecting chambers is aligned almost vertically in the newborn. In the adult the connecting chamber is the largest compartment, but in the neonate the visceral blind sac and the glandular compartment are proportionally larger. Functional aspects of these anatomical differences are discussed in relation to suckling behavior.The intestine consists of a continous tube. There is no caecum; instead the junction between small and large intestine is distinguished by an increase in diameter, a change in epithelial lining, and anastomoses of the jejunal and colic arteries. Large amounts of fat are present in the omentum and mesentery of the neonate.