bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pigment cell localizations in anuran ventral skin at climactic metamorphosis
Authors: Denèfle Jean‐Pierre , Lechaire Jean‐Pierre 
Published: February 2005

AbstractIn anuran amphibians, the specific color pattern of the skin is expressed after metamorphosis, and its formation involves pigment cell migrations. Pigment cells are differently distributed in the tadpole, larval, and froglet skin. To learn more about their fate during metamorphic climax and in the young froglet, we focused our attention on the different localizations of larval melanophores and iridophores in the ventral skin of Rana esculenta before and during skin homing. Localizations of melanophores and iridophores can be elucidated at the developmental stages suggested by Taylor and Kollros (TK stages).At TK stage II (during early premetamorphosis), large melanophores beneath the larval skin are detected. At TK stage X, dispersed melanophores lie under bundles of muscular striated fibrils near the larval skin; they are also observed at the vascular level. At TK stage XVII (prometamorphosis), melanophores are extended on the inner side of the basement lamellar collagen. At the end of prometamorphosis, iridophores are located with melanophores in the separating space between attached basement collagen and derived basement collagen. At TK stage XX (earlier climax), melanophores and iridophores are detected inside the upper extremities of fractures opened in the derived basement collagen. At TK stage XXIV (later climax), both types of larval pigment cells are observed in the inner extremities of breaks derived from the fractures. During climax, these pigment cells occupy the well‐formed breaks. At TK stage XXV in young froglet, the pigment cells remain alone in the breaks formed in the derived basement collagen.Briefly, breaks in the basement lamellar collagen are opened by invading cell processes of mesenchymal cells. The cells move through the fractures toward the epidermis, followed in later stages by melanophores and iridophores.
Clonal development of interconnected germ cells in the rat and its relationship to the segmental and subsegmental organization of spermatogenesis
Authors: Ren Hong Ping , Russell Lonnie D. 
Published: February 2005

AbstractSegments and subsegments are the smallest unit of synchrony thus far described within longitudinal sections of seminiferous tubules. It is known that cells in a clone joined by intercellular bridges are at the same phase of development and are also thought to be units of synchrony. This study was designed to determine if it is possible that the synchrony seen in cells joined by intercellular bridges is the same as that cataloged along the long axis of the seminiferous tubule. In the present study, the maximum number of rat spermatids joined by intercellular bridges (a clone) was obtained. It was hypothesized that if the clone size were larger than the smallest known units of synchrony (segments or subsegments) in the long axis of the seminiferous tubule, then intercellular bridges would most likely govern the synchronous development of segments or subsegments (or finer subdivisions thereof). If the clone size is smaller than the number of cells present in a segment or subsegment, then other factors must govern synchrony in the longitudinal aspect of the tubule. In the determination of spermatid clone size, rat testes were injected with cytochalasin D which opens intercellular bridges of a spermatid clone to produce large symplasts. The number of nuclei in the symplasts was determined from serially sectioned tissue, by drawing nuclei with a camera‐lucida, and by counting nuclei. After extensive examination of tubules, the number of spermatids found in the suspected five largest clones observed was determined to be 650, 607, 338, 240, and 177. The segment and subsegment length and the density of spermatids per given tubule length were determined from previously published data. The numbers of spermatids accommodated in the smallest segment and subsegment were 128 and 30, respectively. Our observations indicate that synchronous development of germ cells along the length of the tubule is controlled by intercellular bridges since the number of conjoined cells required to fill a segment or subsegment is more than the number of cells in the smallest arbitrarily identified units of synchrony cataloged to date.
Localization of boar sperm proacrosin during spermatogenesis and during sperm maturation in the epididymis
Authors: Bozzola J. J. , Polakoski K. , Haas N. , Russell L. D. , Campbell P. , Peterson R. N. 
Published: February 2005

AbstractThe localization of proacrosin was determined by using colloidal gold labeling and electron microscopy of boar germ cells during spermiogenesis to post‐ejaculation. Proacrosin was first localized in round spermatids during the Golgi phase of spermiogenesis; it was associated with the electron‐dense granule, or acrosomal granule that was conspicuous within the acrosome. It remained within the acrosomal granule during the cap and acrosome phases of spermiogenesis. At these stages, there was no apparent association of the proacrosin molecule with the acrosomal membranes. During the maturation phase of spermiogenesis, proacrosin was seen to become dispersed into all regions of the acrosome except the equatorial segment. When sperm from different segments of the epididymis and ejaculated sperm were examined, localization was observed throughout the acrosome except for the equatorial segment. Here proacrosin appeared to be localized on both the inner and outer acrosomal membranes as well as with the acrosomal matrix, although further studies are required to verify the membrane localization. No labeling was seen on the plasma membrane. These data suggest that the synthesis and movement of proacrosin to sites in the acrosome are controlled by an as yet unknown process. The absence of proacrosin on the plasma membrane of mature ejaculated sperm makes it unlikely that this enzyme plays a role in sperm‐zona adhesion prior to capacitation.
Structural characteristics of immature rat sertoli cells in vivo and in vitro
Authors: Kelly Cheri W. , Janecki Andrzej , Steinberger Anna , Russell Lonnie D. 
Published: February 2005

AbstractThe structural properties of pelleted prepubertal Sertoli cells (pre‐culture pelleted cells) from 19‐day‐old rats and of similar cells cultured for 7 days were compared with Sertoli cells from the intact animal (testis tissue from 19‐and 26‐day‐old rats, the in vivo groups). Sertoli cells from freshly isolated pellets and those cultured for 7 days were similar in cell and nuclear volumes to their in vivo counterparts. Cell volumes, organelle volumes, and organelle volume densities of newly isolated Sertoli cells were similar to those of sectioned cells taken from the 19‐day‐old in vivo group, indicating that the procedure for isolation does not grossly alter Sertoli cells. Mean height of cells cultured for 7 days was significantly lower than that of cells from intact animals at 19 and 26 days of age. In vivo, Sertoli cells of 26‐day‐old animals displayed increased organelle volumes and organelle surface areas compared with those from 19‐day‐old animals; volume densities and surface densities remained relatively constant, indicating that in vivo, organelle growth is in proportion to growth of the cell. Most organelle volume and surface densities were not significantly different when 19‐day‐old in vivo cells and pre‐culture pelleted cells were compared. Many organelle volume and surface density values were significantly less in cells grown in culture for 7 days as compared to freshly isolated pelleted cells. After 7 days of culture, most Sertoli cell organelles were significantly less in both volume density and surface density, as compared to the in vivo cell groups (19 or 26 day). This indicates that in vitro the organelles do not develop in proportion to the growth of the cell. After 7 days in culture, the absolute volumes and surface areas of the organelles remained generally unchanged as compared to cells from 19‐day‐old animals. The data show that Sertoli cells grow in volume in vitro like their in vivo counterparts; however, their subcellular features, although well maintained, do not develop in proportion to the cell. This suggests that short‐term cultures are a more ideal system in which to study biochemical responses. Also, cultured prepubertal Sertoli cells are most appropriately used to study prepubertal Sertoli cell function. This is the first study to quantify developmental changes in Sertoli cell structure in vivo as well as to compare them with cellular changes occurring in vitro.
Chorioallantoic placenta formation in the rat: I. Luminal epithelial cell death and extracellular matrix modifications in the mesometrial region of implantation chambers
Authors: Welsh Alerick O. , Enders Allen C. 
Published: February 2005

AbstractOn days 7 and 8 of pregnancy, mesometrial regions of rat gestation sites were examined by light microscopy and transmission electron microscopy to determine what changes occur before the chorioallantoic placenta forms in that region. By day 7, gestation sites contained a uterine lumen mesometrially and an antimesometrial extension of the uterine lumen, the implantation chamber. The implantation chamber consisted of a mesometrial chamber between the uterine lumen and the conceptus, an antimesometrial chamber that contained the conceptus, and a decidual crypt antimesometrial to the conceptus. Stromal cells that formed the walls of the implantation chamber were closely packed decidual cells, while those that surrounded the uterine lumen were loosely arranged. Late on day 7, a portion of the epithelium lining the mesometrial chamber was degenerating, but this area of initial degeneration was never adjacent to the antimesometrial chamber. By early day 8, most of the epithelial cells lining the mesometrial chamber were degenerating and were being sloughed into the chamber lumen. Although degeneration of these epithelial cells morphologically resembled necrosis, it was precisely controlled, since adjacent epithelial cells lining the uterine lumen remained healthy. The space that separated the denuded luminal surface of the mesometrial chamber from underlying decidual cells became wider and was occupied by an extracellular matrix rich in cross‐banded collagen fibrils. Decidual cell processes, that earlier had penetrated the basal lamina beneath healthy epithelial cells, protruded into this matrix and penetrated the basal lamina at the luminal surface. By late day 8, large areas of denuded chamber wall were covered with decidual cell processes, little remained of the basal lamina, and cross‐banded collagen fibrils were scarce in the area occupied by decidual cell processes. During the times studied, uterine tissues that formed the walls of the mesometrial chamber were not in direct contact with the conceptus. This study indicates that trophoblast does not play a direct role in epithelial degeneration, basal lamina penetration, or extracellular matrix modifications in the mesometrial region of implantation chambers where part of the chorioallantoic placenta forms, although trophoblast may be required to trigger or modulate some of the changes.
Arrangement and innervation of the iliocostalis and longissimus muscles of the brown caiman (Caiman crocodilus fuscus: Alligatoridae, crocodilia)
Authors: Murakami Gen , Akita Keiichi , Sato Tatsuo 
Published: February 2005

AbstractThe axial musculature of the brown caiman was investigated in detail with particular attention to the nerve supply, using a binocular stereomicroscope. Due to the prominent development of the longissimus (Lo) and the iliocostalis (IC) muscles of the caiman, the pattern of distribution of the spinal nerves in the body wall was unique; there also was less differentiation of the external intercostalis. There were four primary divisions of the spinal nerves in the thoracic region of the caiman, from ventral to dorsal: the intercostal nerve, the IC nerve, the Lo nerve, and the dorsal main trunk. Thus, the classic concept of the organization of the spinal nerves may not be suitable for the caiman. These findings suggest that evolutionary changes in the dorsolateral axial musculature have brought about the rearrangement of the organization of the spinal nerves. In addition, each clearly segmented myotome of the Lo and IC was innervated by more than two segments of the spinal nerves (pluriseg‐mental innervation). The manner of formation of the myotome and its innervation is discussed from the viewpoint of comparative and developmental anatomy.
Initiation and pattern of angiogenesis in wound healing in the rat
Authors: Phillips Gregg D. , Whitehead Russell A. , Knighton David R. 
Published: February 2005

AbstractThe object of this study was to examine the initiation and pattern of capillary growth associated with wound healing. Collagen sponges were implanted subcutaneously in the hind limbs of adult male rats to stimulate the formation of granulation tissue. Blood vessels of the hind limbs of euthanized rats were perfused with Mercox (an acrylic monomer) via the abdominal aorta at selected periods of time following sponge implantation. When the perfusate was completely cured, the sponge and parajacent tissues were excised and subsequently macerated by alternating immersion in 40% KOH and distilled water. Cast replicas of the vascular lumina were coated with gold and imaged by scanning electron microscopy. At 6 hr, punctate depressions at the periphery of the replicas of vein and venule lumina were noted. The depressions represented sites of leukocyte margination. By 24 hr, the depressions increased numerically, indicating a great increase in the sites of leukocyte margination. The number of these depressions decreased by 48 hr. Concomitantly, the depressions representing endothelial cell nuclei became more pronounced, indicating nuclear hypertrophy of these cells. In addition, capillary bud formation was initiated. At 72 hr, capillary buds were quite apparent and arose solely from venules. Between 7 and 14 days, replicas of capillary lumina were longer and formed an elaborate network, presumably by end‐to‐end, side‐to‐side, and end‐to‐side anastomoses. The network was formed circumferential to the sponge and then capillary sprouts entered the sponge's interstitial spaces.
Hypophyseal angioarchitecture of common tree shrew (Tupaia glis) revealed by scanning electron microscopy study of vascular corrosion casts
Authors: Sudwan Paiwan , Chunhabundit Panjit , Bamroongwong Sirinush , Rattanachaikunsopon Pongsak , Somana Reon 
Published: February 2005

AbstractThe vascular corrosion cast technique in conjunction with scanning electron microscopy (SEM) was used for the study of pituitary microvascularization in the common tree shrew (Tupaia glis). The pituitary vascular casts were obtained by infusion of low viscosity methyl methacrylate plastic (Batson's no. 17) mixture. It was found that the blood supplies to the pituitary complex were from branches of the circle of Willis and could be divided into two groups. The first group consisted of two to four superior hypophyseal arteries (SHAs) branching off from the internal carotid artery supplying each half of the median eminence (ME), infundibular stalk (IS), and pars distalis (PD). The SHAs supplying the ME branched into internal and external capillary plexi. The internal plexus had a larger capillary size (approximately 15 μm in diameter), was deeper in position, and had denser and more complex capillary loops than those in the external plexus. The capillaries of the external plexus were approximately 10 μm in diameter. The two plexi drained into 15–20 hypophyseal portal veins (HPVs) which were located mainly along the ventral and ventrolateral surfaces of the IS before breaking up into large capillaries (approximately 18 μm in diameter) with an anteroposterior arrangement within the PD. The second group consisted of one inferior hypophyseal artery (IHA) on each side branching off from the internal carotid artery. These arteries gave off branches to pierce the dorsolateral and ventrolateral aspects of infundibular process (IP) before branching off to form a capillary network. They also gave rise to radiating capillaries to supply the pars intermedia (PI) surrounding the cortical area of the IP. The hypophyseal cleft separating the PI from the PD was clearly seen with very few blood vessels. The capillaries in both PD and IP joined to form confluent hypophyseal veins draining the blood into the cavernous sinus.
Sensory innervation of the canine esophagus, stomach, and duodenum
Authors: Khurana Ramesh K. , Petras J. M. 
Published: February 2005

AbstractThe sensory innervation of the postpharyngeal foregut was investigated by injecting the enzyme horseradish peroxidase (HRP) into the walls of the esophagus, stomach, or duodenum. The transported HRP was identified histochemically, labeled neurons in the spinal and vagal ganglia were counted, and the results were plotted using an SAS statistical program. The spinal sensory fields of each viscus were defined using three determinations: craniocaudal extent, principal innervation field, and peak innervation field. The data revealed that innervation fields are craniocaudally extensive, the sensory field of each viscus overlaps significantly with its neighbor, yet each viscus can be characterized by a field of peak innervation density.Craniocaudal innervation of the esophagus spans as many as 22–23 paired spinal ganglia (C1‐L2). There are two peak innervation fields for the cervical (C2‐C6 and T2‐T4) and for the thoracic (T2‐T4 and T8‐T12) sectors of the esophagus. The sensory innervation of the stomach extends craniocaudally over as many as 25 paired spinal ganglia (C2‐L5). The peak innervation field of the stomach spans a large area comprising the cranial, middle, and the immediately adjoining caudal thoracic ganglia (T2‐T10). The duodenum is innervated craniocaudally by as many as 15 paired thoracolumbar ganglia (T2‐L3). Peak innervation originates in the middle and caudal thoracic ganglia and cranial lumbar (T6‐L1) ganglia. There is a recognizable viscerotopic organization in the sensory innervation of the postpharyngeal foregut; successively more caudal sectors of this region of the alimentary canal are supplied with sensory fibers from successively more caudal spinal dorsal root ganglia.Vagal afferent innervation of the esophagus, stomach, and duodenum is bilateral and originates predominantly, but not exclusively, from vast numbers of neurons in the nodose (distal) ganglia. The esophagus is innervated bilaterally and more abundantly by jugular (proximal) ganglia neurons than is either the stomach or duodenum.The physiological significance of the findings are discussed in relation to the phenomena of visceral pain and referred pain.
Early stages of trophoblastic invasion of the maternal vascular system during implantation in the macaque and baboon
Authors: Enders Allen C. , King Barry F. 
Published: February 2005

AbstractTrophoblastic invasion and remodeling of the uteroplacental (spiral) arteries in primates are well‐documented, but virtually nothing is known of the early stages of these phenomena. Therefore, we examined invasion of the maternal vasculature in macaques and baboons at, and immediately following, implantation. Following penetration of the uterine epithelium (day 9), trophoblast spreads along the residual epithelial basal lamina. By day 10, cytoplasmic processes penetrate the epithelial and endothelial basal laminase, and syncytial trophoblast insinuates itself between maternal endothelial cells. As lacunae develop, both syncytial and cytotrophoblast are exposed to maternal blood. Endovascular cytotrophoblast was first observed in subepithelial dilated capillaries and venules. These vessels are lined by increasingly hypertrophied endothelial cells. The spiral arterioles are unmodified at this time. Particularly interesting was the observation that there is rapid extensive endovascular trophoblast invasion of the spiral arterioles immediately beneath the implantation site. By day 14–16 nearly all of the small arterioles directly beneath the site are completely occluded. There is no invasion of the veins in this region. Somewhat later, the deeper arterioles in the principal zone are invaded. Rather than a continuous stream of cells invading the deeper arterioles, these endovascular cells occur in clusters ranging from a few cells to groups of cells that completely plug the lumen. Our results indicate that trophoblastic invasion of maternal vessels occurs very early; and, at least initially, trophoblast can migrate between and along endothelial cells without causing their lysis. The endovascular cells eventually interrupt the endothelial lining of the arterioles and penetrate the walls of the vessels. The occlusion of arterioles underneath the site suggests that circulation through the lacunae at this stage is indirect. Corresponding stages of human development were examined, and no invasion of arterioles could be observed prior to formation of an extensive cytotrophoblastic shell.
The fine structure of the elasmobranch renal tubule: Intermediate, distal, and collecting duct segments of the little skate
Authors: Lacy E. R. , Reale E. 
Published: February 2005

AbstractSharks, skates, and rays (Elasmobranchii) have evolved unique osmoregulatory strategies to survive in marine habitats. These adaptations include a complex renal countercurrent system for urea retention. The fine structure of the complete renal tubular epithelium has yet to be elucidated in any species of cartilagenous fish. The present study, which is a companion to our recent paper describing the ultrastructure of the neck and proximal segments of the elasmobranch nephron, uses thin sections and freeze‐fracture replicas to elucidate the fine structural organization of the intermediate, distal, and collecting duct segments of the little skate, Raja erinacea, renal tubule.The epithelium of the intermediate, distal, and collecting duct segments consists of two major cell types: nonflagellar cells, the major epithelial cell type; and flagellar cells, described elsewhere.The intermediate segment consists of six subdivisions lined by cuboidal–‐columuar cells with variously elaborated microvilli and interdigitations of lateral and basal cell plasma membranes, as well as some subdivisions with distinctive vesicles and granules.The distal segment consists of two subdivisions, both of which are lined by a simple epithelium, and are distinguished from each other by their distinctive contents; dense bodies and granules.The collecting duct segment also has two subdivisions, the first lined by a simple columnar epithelium and the second by a stratified columnar epithelium. Both subdivisions have apical secretory granules.The present findings show a more highly specialized and diverse epithelium lining the renal tubule of these cartilagenous fish than is found in either of the “adjacent” phylogenetic taxa, Agnatha or Ostheichthyes, suggesting significant differences among these groups in transepithelial transport mechanisms and renal function.