bluuebunny/crossref_metadata_2025 huggingface dataset:
New data on the immunocytochemical localization of thyrotropin‐releasing hormone in the rat central nervous system
Authors: Merchenthaler István , Csernus Valér , Csontos Csaba , Petrusz Peter , Mess Béla
Published: February 2005

An antiserum raised against the synthetic tripeptide pyroglutamyl‐histidyl‐proline (free acid) was used to localize thyrotropin‐releasing hormone (TRH) in the rat central nervous system (CNS) by immunocytochemistry. The distribution of TRH‐immunoreactive structures was similar to that reported earlier; i.e., most of the TRH‐containing perikarya were located in the parvicellular part of the hypothalamic paraventricular nucleus, the suprachiasmatic portion of the preoptic nucleus, the dorsomedial nucleus, the lateral basal hypothalamus, and the raphe nuclei. Several new locations for TRH‐immunoreactive neurons were also observed, including the glomerular layer of the olfactory bulb, the anterior olfactory nuclei, the diagonal band of Broca, the septal nuclei, the sexually dimorphic nucleus of the preoptic area, the reticular thalamic nucleus, the lateral reticular nucleus of the medulla oblongata, and the central gray matter of the mesencephalon. Immunoreactive fibers were seen in the median eminence, the organum vasculosum of the lamina terminalis, the lateral septal nucleus, the medial habenula, the dorsal and ventral parabrachial nuclei, the nucleus of the solitary tract, around the motor nuclei of the cranial nerves, the dorsal vagal complex, and in the reticular formation of the brainstem. In the spinal cord, no immunoreactive perikarya were observed. Immunoreactive processes were present in the lateral funiculus of the white matter and in laminae V‐X in the gray matter. Dense terminal‐like structures were seen around spinal motor neurons. The distribution of TRH‐immunoreactive structures in the CNS suggests that TRH functions both as a neuroendocrine regulator in the hypothalamus and as a neurotransmitter or neuromodulator throughout the CNS.
Morphological differences between secretory cells of wet and dry types of human ceruminous glands
Authors: Shugyo Yoshihlko , Sudo Naohiro , Kanai Kazuo , Yamashita Toshio , Kumazawa Tadami , Kanamura Shinsuke
Published: February 2005

Morphological differences between secretory cells of the wet and dry types of human ceruminous glands were examined. The heights of secretory cells varied from tall and medium to low in both wet‐and dry‐type glands. The two gland types differed in morphologic features of the tall cells and the cells of medium height. The Golgi apparatus was well developed in the tall cells and fairly well developed in the cells of medium height in the wet‐type gland, whereas it was generally small in the corresponding cells of the dry type. Light granules were abundant in the tall cells and in the cells of medium height in the wet‐type gland, whereas light granules were rare in these cells in the dry‐type gland. Furthermore, the light granules in the wet‐type gland cells were observed in close relation to a well‐developed Golgi apparatus, and sometimes showed a morphologic appearance suggesting exocytosis. Apical protrusions, probably related to apocrine secretion, were generally large and round and bore “microvilli and light granules” or “very few microvilli and no light granules” in the tall cells of the wet‐type gland. However, the protrusions of the tall cells of the dry‐type gland were generally large and slender and possessed no microvilli and no granules. The protrusions were not observed in the cells of medium height or in low cells in either type of gland.

The results show that eccrine secretion characterizes the wet‐type gland, but it is not clearly evident in the dry‐type gland. This differences may be related to differences in composition between the wet and dry cerumens.
Fine structure and immunocytochemistry of cells within the endocrine pancreas of larval and adult sea lampreys, Petromyzon marinus L.
Authors: Elliott W. M. , Youson J. H.
Published: February 2005

Immunocytochemistry with protein A‐gold and routine electron microscopy were used to identify cell types within the endocrine pancreas of larvae, juvenile adults, and upstream‐migrant adults of the sea lamprey, Petromyzon marinus. The larval pancreatic islets are composed only of insulin‐immunoreactive B‐cells, which are uniform in their fine structure. The cranial and caudal pancreatic tissue in both adult periods contains three cell types: B‐cells, somatostatin‐immunoreactive D‐cells, and a third cell type of unknown content. No glucagon‐immunoreactive cells are present in lampreys, but B‐and D‐cells exist in equal numbers in the pancreatic tissue of adults. The B‐cells of adults have a fine structure similar to those in larvae. D‐cells have secretory granules that are distinctly different from those both in B‐cells and in the third cell type. Although B‐ and D‐cells in lamprey pancreatic tissues have a basic morphological similarity to these cells in other vertebrates, their granules are generally of smaller dimensions. The inclusion of granules within large pleomorphic bodies in many D‐cells indicates that granule turnover is common. Immunocytochemistry will be a useful tool for showing the relationship between the cells in the degenerating bile ducts and those of the developing adult pancreas.
Preservation of the ability of dissociated quail wing bud mesoderm to elicit a position‐related differentiate response
Authors: Stocker Kate M. , Carlson Bruce M.
Published: February 2005

Previous studies showed that grafting wedges of fresh or cultured anterior quail wing mesoderm into posterior slits in chick wing buds resulted in the formation of supernumerary cartilage in a high percentage of cases. When anterior quail mesoderm, which had been dissociated into single cells and pelleted by centrifugation, was grafted into posterior slits of host chick wing buds, supernumerary rods or nodules of cartilage formed in 74.3% of the cases. Few supernumerary skeletal structures formed following control operations in which pelleted dissociated anterior or posterior mesoderm was grafted into homologous locations in host chick wing buds. When pelleted, dissociated anterior mesoderm was cultured in vitro for 1 or 2 days prior to being implanted in posterior locations, the incidence of supernumerary cartilage formation increased to 95.5% and 93.8%, respectively. The incidence of supernumerary cartilage formation following control orthotopic grafts of cultured mesoderm was 11.8% for 1‐day and 31% for 2‐day cultured anterior mesoderm; for 1‐ and 2‐day cultured posterior mesoderm, the incidence of supernumerary cartilage formation was 20% and 41.7%, respectively. Longer‐term culture resulted in a substantial decrease in the percentage of supernumerary cartilage after anterior to posterior grafts and an increase in the incidence of supernumerary cartilage from control grafts. The results demonstrate that quail anterior wing bud mesodermal cells do not need to maintain constant contact with one another in order to retain the ability to form or stimulate the formation of supernumerary cartilage after being grafted into a posterior location in a host wing bud. This ability is retained when the pelleted dissociated mesoderm is cultured in vitro outside the limb field for at least 1 to 2 days.
A test of positional properties of avian wing‐bud mesoderm
Authors: Carlson Bruce M.
Published: February 2005

Supernumerary wing structures are readily produced by grafting pieces of wing‐bud mesoderm into different locations of host wing buds, but the mechanism underlying their formation remains obscure. The major aim of this study was to examine the ability of posterior quail wing‐bud mesoderm, cultured in vitro long enough to lose ZPA (zone of polarizing activity) activity, to stimulate or participate in the formation of supernumerary structures when grafted into anterior slits of host chick wing buds. Small pieces of anterior and posterior quail wing‐bud mesoderm (HH stages 21‐23) were placed in in vitro culture for up to 3 days. After 2 days, ZPA activity of cultured mesoderm was lost. After the grafting of 2‐ to 3‐day cultured anterior quail wing‐bud mesoderm into posterior slits of host chick wing‐buds, a consistently high percentage (70%‐90%) of grafts result in formation of supernumerary cartilage; in this experiment, however, only a low percentage of grafts resulted in supernumerary cartilage when 2‐ to 3‐day cultured posterior mesoderm was grafted into anterior slits. Taken with controls, these results show that positional differences exist between cultured anterior and posterior wing‐bud mesoderm. Serial‐section analysis of numerous operated wings has shown several patterns of contribution to supernumerary structures by cells of graft and host. Single supernumerary digits induced by grafts of ZPA mesoderm into anterior slits were normally composed entirely of host cells, but graft cells regularly contributed to skeletal elements of more complex supernumerary structures. Cartilage rods produced by anterior‐to‐posterior grafts were composed mostly of graft cells, but cartilage nodules and the bases of some rods were often mosaics of chick and quail cells. The results support the proposition that mesodermal cells of the quail wing‐bud possess a form of anteroposterior positional memory, but its nature and the means by which the memory of grafted cells interacts with host mesoderm are still not clear.
Morphogenesis of the respiratory bronchiole in rhesus monkey lungs
Authors: Tyler Nancy K. , Hyde Dallas M. , Hendrickx Andrew G. , Plopper Charles G.
Published: February 2005

The epithelium of the respiratory bronchiole in the adult rhesus monkey consists of two populations: a pseudostratified epithelium with basal, mucous goblet, and ciliated cells located near the pulmonary artery (PA); and a simple cuboidal epithelium composed only of nonciliated bronchiolar epithelial (or Clara) cells in areas away from the PA. This study describes the pattern of differentiation of these two epithelial populations, and their relationship to the PA and to the time of appearance of alveoli. in the respiratory bronchiole of the rhesus monkey during the period of 90‐125 days gestational age (DGA). These events were related to changes in the adjacent parenchyma. Dissected airways of infusion‐fixed, critical‐point‐dried lungs were evaluated by scanning microscopy followed by light microscopy of the same airways. At 54% of gestation (90 DGA), the distal airway was lined by a mixture of ciliated and nonciliated cells. By 67% of gestation (110 DGA), the ciliated cells were confined to the epithelium over the PA. The underlying connective tissue initially was cellular containing few fibers but was fibrous by 76% of gestation (125 DGA). Alveolarization began near the most distal cartilage at 57% of gestation (95 DGA), the same period at which secondary septation occurred in the distal acinus. Thus, alveolarization occurred simultaneously in two centers: (1) the proximal centriacinar region in the vicinity of the most distal cartilage and (2) the distal lung parenchyma. The duration of centriacinar alvcolarization was short, approximately 5 days.
Ultrastructure of the osteogenesis of acellular vertebral bone in the Japanese medaka, Oryzias latipes (teleostei, cyprinidontidae)
Authors: Ekanayake Sunetra , Hall Brian K.
Published: February 2005

An ultrastructural study by transmission electron microscopy (TEM) of the vertebrae of embryonic, larval, juvenile and mature medaka shows that each vertebra consists of a core of notochordal cells surrounded by a sheath of bone. The vertebral bone lacks either fully or partially embedded cells in the matrix throughout development. Bone matrix is secreted by a layer of cells that lies over the outer surface of the vertebral bone. During the early stages of osteogenesis, these cells secrete bone matrix all around themselves. However, because of the gradual flow of the newly synthesized bone matrix through intercellular spaces, matrix‐producing cells do not become trapped in their own secretion. In later stages of osteogenesis, these cells secrete matrix only toward the already‐deposited bone. This polarized matrix secretion allows the osteoblasts to stay always on the bone surface and never to become trapped in the matrix as osteocytes.
Ultrastructure of the mineralizing metacarpophalangeal joint of progressive ankylosis (ank/ank) mice
Authors: Sampson H. Wayne
Published: February 2005

The metacarpophalangeal joint of the progressive ankylosis mouse was examined at 4, 6 and 8 weeks of age by using electron microscopy and electron probe microanalysis. These studies describe the progression of the disorder, and they reveal three overlapping phases: pannus proliferation, chondrophyte formation and mineralization, and articular cartilage mineralization. The chondrophyte mineralized in a manner fairly similar to endochondrial bone, whereas articular cartilage mineralized by advancement of a calcification front across the cartilage. Synovial crystal phagocytosis was also observed. The progressive ankylosis mouse should be an important model for studying both crystal deposition and abnormal articular cartilage calcification.
Structural manifestations of diabetic cardiomyopathy in the rat and its reversal by insulin treatment
Authors: Thompson Ed W.
Published: February 2005

The structural effects of diabetes and subsequent insulin treatment upon the contractile and supporting elements of the rat myocardium were examined at progressive stages of both untreated and treated disease. Diabetes was induced by intravenous injection of alloxan, and tissue was examined after 6, 12, and 26 weeks. Insulin treatment began after 12 weeks of diabetes and tissue from these animals was examined after the same intervals. Within the cardiocytes, diabetes produced a focal yet progressive loss of myofibrils, transverse tubules, and sarcoplasmic reticulum, and separation of the fasciae adherens was evident at the intercalated disk. Mitochondrial damage was not evident. These cytoplasmic alterations were accompanied by intercellular and perivascular deposition of connective tissue, thickening of the endothelial cytoplasm with pinocytotic hyperactivity, and characteristic basal laminar changes. When insulin treatment began after 12 weeks of diabetes, most, but not all, of these changes were reversed, and this reversal was essentially complete within 6‐12 weeks. Even with longer periods of insulin treatment, cardiocytes still exhibited scattered areas of myofibril loss and extracellular matrix was retained. In contrast, diabetic changes in the intercalated disk and capillaries, including their basal laminae, were completely and rapidly reversed. It is hypothesized that the structural manifestations of diabetic cardiomyopathy consist of two major components; the first is a short‐term, physiologic adaptation to metabolic alterations, while the other represents degenerative changes for which the myocardium has only a limited capacity for repair.
Computer ranking of the sequence of appearance of 40 features of the brain and related structures in staged human embryos during the seventh week of development
Authors: O'Rahilly Ronan , Müller Fabiola , Hutchins Grover M. , Moore G. William
Published: February 2005

The sequence of events in the development of the brain in human embryos, already published for stages 8‐17, is here continued for stages 18 and 19. With the aid of a computerized bubble‐sort algorithm, 58 individual embryos were ranked in ascending order of the features present. The increasing structural complexity provided 40 new features in these two stages. The chief characteristics of stage 18 (approximately 44 postovulatory days) are rapidly growing basal nuclei; appearance of the extraventricular bulge of the cerebellum (flocculus), of the superior cerebellar peduncle, and of follicles in the epiphysis cerebri: and the presence of vomeronasal organ and ganglion, of the bucconasal membrane, and of isolated semicircular ducts. The main features of stage 19 (approximately 48 days) are the cochlear nuclei, the ganglion of the nervus terminalis, nuclei of the prosencephalic septum, the appearance of the subcommissural organ, the presence of villi in the choroid plexuses of the fourth and lateral ventricles, and the stria medullaris thalami.
Immunohistochemical renin study of DES‐induced renal tumor in the Syrian hamster
Authors: Dodge Alice H. , Brownfield Mark , Reid Ian A. , Inagami Tadashi
Published: February 2005

Diethylstilbestrol (DES) treatment of a male Syrian hamster resulted in the development of a renal tumor and its widely scattered scrosal metastases. Cells in both the primary tumor and metastatic nodules contained secretory granules. The tumors were transplanted serially into DES‐supported and non‐DES‐supported host hamsters until DES‐independent tumors developed. Rabbit antiserum to mouse salivary renin and rabbit antiserum to rat kidney resin were reacted with sections of the primary tumor, metastatic nodules, and all transport tumors. The sections were stained by the PAP and Vector‐ABC‐AP procedures. Renin‐positive material was observed in all tumors. Plasma renin activity (PRA) was determined for the host hamsters carrying the renal tumor transplants and compared to the PRA values that had been determined for normal non‐DES‐treated male and female hamsters. It was found that the average PRA values of host hamsters carrying the tumor transplants were significantly higher than the normal PRA ralues.
Innervation of the C cells of chicken ultimobranchial glands studied by immunohistochemistry, fluorescence microscopy, and electron microscopy
Authors: Kameda Yoko , Okamoto Kiyoshi , Ito Miyoshi , Tagawa Takasuke
Published: February 2005

Innervation of the ultimobranchial glands in the chicken was investigated by immunohistochemistry, fluorescence microscopy and electron microscopy. The nerve fibers distributed in ultimobranchial glands were clearly visualized by immunoperoxidase staining with antiserum to neurofilament triplet proteins (200K‐, 150K‐ and 68K‐dalton) extracted from chicken peripheral nerves. The ultimobranchial glands received numerous nerve fibers originating from both the recurrent laryngeal nerves and direct vagal branches. The left and right sides of the ultimobranchial region were asymmetrical. The left ultimobranchial gland had intimate contact with the vagus nerve trunk, especially with the distal vagal ganglion, but was somewhat separated from the recurrent nerve. The right gland touched the recurrent nerve, the medial edge being frequently penetrated by the nerve, but the gland was separated from the vagal trunk. The left gland was innervated mainly by the branches from the distal vagal ganglion, whereas the right gland received mostly the branches from the recurrent nerve. The carotid body was located cranially near to the ultimobranchial gland. Large nerve bundles in the ultimobranchial gland ran toward and entered into the carotid body.

By fluorescence microscopy, nerve fibers in ultimobranchial glands were observed associated with blood vessels. Only a few fluorescent nerve fibers were present in close proximity to C cell groups; the C cells of ultimobranchial glands may receive very few adrenergic sympathetic fibers.

By electron microscopy, numerous axons ensheathed with Schwann cell cytoplasm were in close contact with the surfaces of C cells. In addition, naked axons regarded as axon terminals or “en passant” synapses came into direct contact with C cells. The morphology of these axon terminals and synaptic endings suggest that ultimobranchial C cells of chickens are supplied mainly with cholinergic efferent type fibers. In the region where large nerve bundles and complex ramifications of nerve fibers were present, Schwann cell perikarya investing the axons were closely juxtaposed with C cells; long cytoplasmic processes of Schwann cells encompassed large portions of the cell surface. All of these features suggest that C‐cell activity, i.e., secretion of hormones and catecholamines, may be regulated by nerve stimu1i.
Growth allometry of craniomandibular muscles, tendons, and bones in the laboratory rat (Rattus norvegicus): Relationships to oromotor maturation and biomechanics of feeding
Authors: Huhov Jack , Henry‐Ward Winsome , Phillips Lisa , German Rebecca
Published: February 2005

This study addressed the problem of how growth of Craniomandibular muscles, tendons, and bones influences the acquisition of oromotor skills and biomechanics of feeding in the laboratory rat (Rattus norvegicus). Rats representing a 6.6‐fold size range were dissected, and muscles, tendons, and mandibles were weighed. Cross‐sectional areas of tendons and bones providing attachment surfaces for muscles were estimated. Ontogenetie scaling of Craniomandibular muscles, tendons, and bones was described by using linear regression models, and departures from size‐required compensations were used to characterize changes in oromotor function. A two‐dimensional model was developed which permitted calculation of mechanical advantages of four masticatory muscles; the model was used to show how mandibular growth and tooth eruption influence the biomechanics of rat feeding. Relative to mandible weight, most jaw muscles scaled either isometrically or positively, tendon cross‐sectional areas scaled isometrically or negatively, and bone surfaces scaled negatively. With the exception of the superficial masseter and internal pterygoid muscles, mechanical advantages did not change significantly during mandible growth. Growth patterns of Craniomandibular muscles, tendons, and bones contribute significantly to changes in morphology and oromotor function.
Visualization of chromosome assembly during the S and G2 stages of the cycle and chromosome disassembly during the G1 stage in semithin sections of mouse duodenal crypt cells and other cells
Authors: El‐Alfy M. , Leblond C. P.
Published: February 2005

Previous examination of dividing cells in the isthmus of the mouse pyloric antrum by using semithin (0.5‐μm‐thick) Epon sections revealed that the prophasic condensation of chromosomes began early in the DNA‐synthesizing (S) stage. In order to examine whether the same observation could be made in other proliferating cell types, the crypt base columnar ceils in mouse duodenum and the hepatocytes of the rat 48 hr after partial hepatectomy were investigated by morphologic and radioautographic techniques.

When crypt base columnar cells were studied in semi‐thin Epon sections, the four phases of mitosis showed the characteristic features described by classical cytologists. Moreover, the proportion of cells in prophase and telophase was high. To relate the mitotic phases to the stages of the cell cycle, the “frequency of labeled mitoses method” provided the duration of the cell cycle, 12.3 hr, and of the S stage, 7.3 hr. From the frequency of the occurrence of mitotic phases, it was estimated that metaphase lasted 0.3 hr and anaphase 0.11 hr, in line with previous estimates. However, the durations of prophase and telophase were long, 5.9 and 1.9 hr, respectively. The whole mitotic process took over 8 hr. From the duration of prophase and cycle stages, it was calculated that 67% of the S stage was occupied by prophasic cells. In fair agreement with this estimate, 68% of the labeled cells 10 min after a 3H‐thymidine injection were found to be in prophase.

In regenerating hepatocytes, the morphological features and frequency of prophase and telophase cells were similar to those observed in duodenal crypt cells. While the cycle time was not measured and, therefore, the duration of cycle stages and mitotic phases could not be estimated, it is likely that their duration would be of the same order of magnitude.

In conclusion, the mitotic process in duodenal crypt cells takes over 8 hr. Moreover, the crypt cells, like antral isthmal cells, show features of early prophase soon after they enter the S stage of the cycle.
Cyclic modulation of sertoli cell junctional complexes in a seasonal breeder: The mink (Mustela vison)
Authors: Pelletier R.‐Marc
Published: February 2005

The development and modulation of Sertoli cell junctions was studied in newborn and adult mink during the active and inactive spermatogenic phases. The techniques used were electron microscopy of freeze‐fractured replicas and thin sections of tissues infused with horseradish peroxidase as a junction permeability tracer. In the newborn, freeze‐fractured developing junctions had either spherical or fibrillar particles. In addition, Junctional domains where particles were associated preferentially with the E‐face, and others where particles were associated preferentially with the P‐face, were found developing either singly or conjointly within a given membrane segment, thus yielding a heterogeneous Junctional segment. Coincidently with the development of a tubular lumen and the establishment of a competent blood‐testis barrier, Junctional strands were composed primarily of particulate elements associated preferentially with the E‐face. In adult mink during active spermatogenesis, cell junctions were found on the entire lateral Sertoli cell plasma membrane from the basal to the luminal pole of the cell. In the basal third of the Sertoli cell, membranous segments that faced a spermatogonium or a migrating spermatocyte displayed forming tight, gap, and adherens junctions. In the middle third, abutting membrane segments localized above germ cells were involved in continuous zonules and in adherens junctions. In the apical or luminal third, the zonules were discontinuous, and the association of Junctional particles with the E‐face furrow was lost. Gap junctions increased in both size and numbers. Junctional vesicles that appeared as annular gap and tight‐junction profiles in thin sections or as hemispheres in freeze‐fracture replicas were present. Reflexive tight and gap junctions were formed through the interaction of plasma membrane segments of the same Sertoli cell. Internalized Junctional vesicles were also present in mature spermatids. During the inactive spermatogenic phase, cell junctions were localized principally in the basal third of the Sertoli cell; Junctional strands resembled those of the newborn mink. During the active spermatogenic phase, continuous zonules were competent in blocking passage of the protein tracer. During the inactive phase the blood‐testis barrier was incompetent in blocking entry of the tracer into the seminiferous epithelium. It is proposed that modulation of the Sertoli cell zonules being formed at the base and dismantled at the apex of the seminiferous epithelium follows the direction of germ cell migration and opposes the apicobasal direction of junction formation reported for most epithelia. The arrest of spermatogenesis coincides with dramatic changes in the dynamic modifications of Sertoli cell zonules.
Synthesis of lens capsule and plasma membrane glycoproteins by lens epithelial cells and fibers in the rat
Authors: Haddad A. , Bennett G.
Published: February 2005

The lens of the eye possesses a capsule which is a greatly hypertrophied basement membrane. To investigate the synthesis of glycoproteins destined for this capsule, 3H‐fucose was iryected into the vitreous body of intact rats weighing approximately 200 gm. The animals were killed from 10 min to 14.5 months later, and their lenses were processed for electron microscope radioautography. At 10 min after injection, more than 58% of the silver grains were localized to the Golgi apparatus of the lens epithelial cells. By day 1, the heaviest sites of reaction were the plasma membrane (more than 50% of total label), the basal cytoplasm, and the adjacent lens capsule, where a heavy band of reaction was seen. The remainder of the capsule exhibited a lighter diffuse reaction. In the lens fibers, the label was at first localized to clusters of vesicles but then migrated to the plasma membrane and to the region of the capsule adjacent to the basal surface of these fibers. Light microscope radioautographs of the lens capsule at later time intervals revealed that by 1 month after injection the diffuse reaction had disappeared, and only the strongly labeled band remained. By 14.5 months after injection, this band had migrated partially across the lens capsule, but the capsule itself had increased considerably in thickness. On the other hand, the distance between the labeled band and the free edge of the capsule had decreased from that seen at the time of injection.
Myocardial cell relationships during morphogenesis in normal and cardiac lethal mutant axolotls, Ambystoma mexicanum
Authors: Fransen Margaret E. , Lemanski Larry F.
Published: February 2005

Sarcomere formation has been shown to be deficient in the myocardium of axolotl embryos homozygous for the recessive cardiac lethal gene c. We examined the developing hearts of normal and cardiac mutant embryos from tailbud stage 33 to posthatching stage 43 by scanning electron microscopy in order to determine whether that deficiency has any effect on heart morphogenesis. Specifically, we investigated the relationships of myocardial cells during the formation of the heart tube (stage 33), the initiation of dextral looping (stages 34–36), and the subsequent flexure of the elongating heart (stages 38–43). In addition, we compared the morphogenetic events in the axolotl to the published accounts of comparable stages in the chick embryo.

In the axolotl (stage 33), changes in cell shape and orientation accompany the closure of the myocardial trough to form the tubular heart. The ventral mesocardium persists longer in the axolotl embryo than in the chick and appears to contribute to the asymmetry of dextral looping (stages 34–36) in two ways. First, as a persisting structure it places constraints on the simple elongation of the heart tube and the ability of the heart to bend. Second, after it is resorbed, the ventral myocardial cells that contributed to it are identifiable by their orientation, which is orthogonal to adjacent cells: a potential source of shearing effects. Cardiac lethal mutant embryos behave identically during these events, indicating that functional sarcomeres are not necessary to these processes. The absence of dynamic apical myocardial membrane changes, characteristic of the chick embryo (Hamburger and Hamilton stages 9–11), suggests that sudden hydration of the cardiac jelly is less likely to be a major factor in axolotl cardiac morphogenesis.

Subsequent flexure (stages 38–43) of the axolotl heart is the same in normal and cardiac lethal mutant embryos as the myocardial tube lengthens within the confines of a pericardial cavity of fixed length. However, the cardiac mutant begins to exhibit abnormalities at this time. The lack of trabeculation (normally beginning at stage 37) in the mutant ventricle is evident at the same time as an increase in myocardial surface area, manifest in extra bends of the heart tube at stage 39. Nonbeating mutant hearts (stage 41) have an abnormally large diameter in the atrioventricular region, possibly the result of the accumulation of ascites fluid. In addition, mutant myocardial cells have a larger apical surface area compared to normals.
Microvascular networks in tympanic membrane, malleus periosteum, and annulus perichondrium of neonatal mongrel dog: A vasculoanatomic model for surgical considerations
Authors: Maher William P.
Published: February 2005

India‐ink‐imaged blood‐vessel networks in cleared tympanic membranes and adnexa from ten neonatal dogs were examined microscopically and photographed. The major significance of the study lies in documentation of a dual source of arterial supply, a bilaminar relationship of arterial and venous plexuses intrinsic to the tympanic membrane, and a consistent major venous pathway relative to a definite locus (pars flaccida of the membrane). Illustration of all three types of blood pathways (arteries, veins, and capillaries) provides new vasculoanatomic data that are essential to ear surgery, specifically—to myringotomies and myringoplasties. A comparison was made between dog and human tympanic membrane structures and their arterial supplies. Close similarities suggested that dog tympanic membrane might serve as a suitable model for development of innovative surgical procedures and as a model for rehearsal of difficult techniques. The results of this investigation provide a valuable caveat to otologists.
Dentin resorption mediated by odontoclasts in physiological root resorption of human deciduous teeth
Authors: Sasaki Takahisa , Motegi Nobuo , Suzuki Hiroshi , Watanabe Chiaki , Tadokoro Katsumi , Yanagisawa Takaaki , Higashi Shohei
Published: February 2005

Extracted human deciduous teeth undergoing physiological root resorption were fixed with a mixture of formaldehyde and glutaraldehyde and processed for scanning (SEM) and analytical transmission electron microscopy, as well as acid trimeta‐phosphatase cytochemistry. The granulated tissues, which are rich in multinucleated odontoclasts and capillary vessels, formed various resorption lacunae on the resorbing dentin surfaces. SEM observations of dentin surfaces treated with sodium hypochlorite revealed two types of resorption lacunae: deep, round lacunae in which the peritubular matrix of dentinal tubules was strongly dissolved; and shallow, irregular lacunae with intact peritubular matrix. In trypsin‐treated materials, the resorption surfaces were characterized by the presence of numerous collagen fibers in both the peritubular and intertubular matrices, suggesting demineralization of the surface dentin. Odontoclasts were characterized by the presence of abundant mitochondria, perinuclear stacks of Golgi membranes, various lysosomes, numerous endocytotic vacuoles, and a well‐developed ruffled border against the resorption lacunae. Most endocytotic vacuoles were distributed in the cytoplasm between the ruffled border and the nuclei. In undemineralized ultrathin sections, the surface dentin of resorption lacunae consisted of collagen fibers and apatite crystals and had a lower packing density than those in unresorbed, deeper dentin. Many apatite crystals were demonstrated to be present in the extracellular channels of the ruffled border and in adjacent endocytotic vacuoles derived from it. Lysosomes located in the perinuclear cytoplasm of odontoclasts contained amorphous dense material and/or a small amount of crystals. An energy‐dispersive x‐ray micro‐analysis of apatite crystals in undemineralized sections indicated that the energy spectrum peaks of Ca and P detected from crystals in resorbing dentin were much lower than those in unresorbed dentin. Similarly, lower spectrum peaks of Ca and P were obtained from crystals found in the ruffled border and endocytotic vacuoles of odontoclasts. A slight trace Ca peak also was detected in the amorphous dense material in lysosomes of odontoclasts. The enzyme cytochemistry of lysosomal acid trimetaphosphatase indicated that odontoclasts had intense enzymatic activity in the Golgi membranes, endoplasmic reticulum cisternae, lysosomes, and endocytotic vacuoles. Dense reaction precipitates of enzymatic activity also were found along the dentin surfaces of resorption lacunae occupied by odontoclast ruffled borders. These results suggest that, during physiological root resorption of human deciduous teeth, odontoclasts perform, at least in part, extracellular demineralization of the surface dentin and subsequently resorb and dissolve some liberated apatite crystals.
Development of dermal ridges in the volar skin of fetal pigtailed macaques (Macaca nemestrina)
Authors: Okajima Michio , Newell‐Morris Laura
Published: February 2005

Development of the dermal ridges in volar skin was investigated in 28 pigtailed macaque (Macaca nemestrina) fetuses of known gestational age, ranging from 51 days postconception to newborn. Histology, scanning electron microscopy, and staining of the abraded dermal surface were used in the study. Morphological features of the dermal‐epidermal system and their changes with advancing age are described. Chronology was established for stages in the development of the volar skin, i.e., the differentiation of the primary and secondary epidermal ridges (PER and SER) at the undersurface of the epidermis corresponding to the formation of primary and secondary dermal ridges (PDR and SDR) and the development of the dermal papillae. PDRs were first seen at 55 gestational days and SDRs at 93 days. Differentiation of sweat ducts occurred over the period between 60 and 119 gestational days. A regional sequence of differentiation starting with the digital apices of the hand and ending in the calcar area and the phalanges of the foot was documented. Generally, morphogenesis in the macaque was accelerated relative to that in the human fetus by approximately 3 weeks.
Innervation of developing intrafusal muscle fibers in the rat
Authors: Kucera Jan , Walro Jon M. , Reichler Judith
Published: February 2005

The chronology of development of spindle neural elements was examined by electron microscopy in fetal and neonatal rats. The three types of intrafusal muscle fiber of spindles from the soleus muscle acquired sensory and motor innervation in the same sequence as they formed—bag2, bag1, and chain. Both the primary and secondary afferents contacted developing spindles before day 20 of gestation. Sensory endings were present on myoblasts, myotubes, and myofibers in all intrafusal bundles regardless of age. The basic features of the sensory innervation—first‐order branching of the parent axon, separation of the primary and secondary sensory regions, and location of both primary and secondary endings beneath the basal lamina of the intrafusal fibers—were all established by the fourth postnatal day. Cross‐terminals, sensory terminals shared by more than one intrafusal fiber, were more numerous at all developmental stages than in mature spindles. No afferents to immature spindles were supernumerary, and no sensory axons appeared to retract from terminations on intrafusal fibers. The earliest motor axons contacted spindles on the 20th day of gestation or shortly afterward. More motor axons supplied the immature spindles, and a greater number of axon terminals were visible at immature intrafusal motor endings than in adult spindles; hence, retraction of supernumerary motor axons accompanies maturation of the fusimotor system analogous to that observed during the maturation of the skeletomotor system. Motor endings were observed only on the relatively mature myofibers; intrafusal myoblasts and myotubes lacked motor innervation in all age groups. This independence of the early stages of intrafusal fiber assembly from motor innervation may reflect a special inherent myogenic potential of intrafusal myotubes or may stem from the innervation of spindles by sensory axons.
Ultrastructural epithelial zonation of the primate endometrium (rhesus monkey)
Authors: Kaiserman‐Abramof Ita R. , Padykula Helen A.
Published: February 2005

The uterine endometrium of menstruating primates (rhesus monkey, human) consists of a germinal basalis that regenerates a transient func‐tionalis during each menstrual cycle. The endometrium is further subdivided into 4 zones that differ histologi‐cally and in epithelial mitotic rate along the longitudinal axes of the uterine glands and microvasculature (Bartelmez et al: Contrib. Embryol. Carnegie Inst., 34:99‐146, 1951; Bartelmez: Am. J. Obstet. GynecoL, 74:931–955,1957; Padykula et al.: Biol. Reprod., 32:1103–1118, 1984; Biol. Reprod., in press, 1988). The zones are defined as follows: functionalis I, luminal epithelium; functionalis II (upper straight gland segments); basalis III (middle gland segments), and basalis IV (bottoms of the glands). The surrounding stroma and microvasculature also differ zonally.

Ultrastructural epithelial differences are evident among the 4 zones during 3 distinct functional states during natural menstrual cycles and after ovariectomy: (1) basal level after ovariectomy and (2) estrogen dominance and (3) progesterone dominance. Zonal structural differences persist at a minimal level of differentiation after ovariectomy and thus zonation is an inherent property. During estrogen dominance, distinctive ultra‐structural differences are evident among the 4 zones, such as epithelial cell heterogeneity in functionalis I and homogeneity in functionalis II. Also a distinctive glandular cell type occurs in basalis III and IV that is recognized by a highly irregular cisternal rough endo‐plasmic reticulum that permeates the cytoplasm. During progesterone dominance, ultrastructural differences exist among the 4 zones except for similarity between the epithelial cells of functionalis II and basalis III. Postovulatory epithelial cells of functionalis I and II and basalis III become postmitotic via progesterone inhibition but intracellular differentiation continues progressively. Postovulatory epithelial mitotic activity in basalis IV escapes progesterone inhibition as the [3H]thymidine labeling index continues to increase from 1 to 12% during the menstrual cycle (Padykula et al.: Reprod., 30(Suppl. l).‐92 (Abstr. 123), 1984). This post‐ovulatory proliferation coupled with progressive differentiation in basalis IV may represent a stem‐progenitor set of cells for postmenstrual endometrial regeneration or alternatively for creation of the maternal placenta.
Lectin histochemistry of the embryonic heart: Expression of terminal and penultimate galactose residues in developing rats and chicks
Authors: Fazel A. R. , Thompson R. P. , Sumida H. , Schulte B. A.
Published: February 2005

Rat embryos at days 10‐18 of gestation and chicken embryos at days 3‐6 of incubation were fixed and processed for lectin histochemistry. The distribution of binding sites for a lectin from the peanut Arachis hypogaea (PNA) conjugated to horseradish per‐oxidase (HRP) was determined on tissue sections both before and after enzymatic cleavage of sialic acid with neuraminidase (sialidase). Endocardial cushion tissue in the rat, but not in the chick, reacted with PNA‐HRP prior to digestion with sialidase. Endocardium of both species (12 and 13 days in rat, 5 and 6 days in chick), particularly at the level of endocardial cushions, reacted strongly with the sialidase‐PNA sequence; this staining decreased markedly after day 14 of gestation in the rat. PNA binding sites capped by sialic acid were most abundant in the developing rat heart during the critical period of endocardial cushion formation and decreased as development proceeded. The marked changes in the appearance and distribution of cardiac cell and tissue glycoconjugates during cardiogenesis support the concept that rapid changes occur in the structure of complex carbohydrates during embryonic and fetal development. The findings also suggest that such glycosylation‐related events may be species specific.
Cell death by apoptosis during involution of the lactating breast in mice and rats
Authors: Walker Neal I. , Bennett Rosemary E. , Kerr John F. R.
Published: February 2005

The role of cell death in involution of lactating breast was investigated in mice and rats by light and electron microscopy. Apoptosis, recognized by sharply demarcated compaction of chromatin against the nuclear envelope and by shrinkage and budding of the whole cell to form membrane‐bounded apoptotic bodies, was responsible for major loss of cells in both species. In the mouse, rapid involution during the first 2 days was associated with shedding of large numbers of apoptotic bodies derived from alveolar epithelial cells into alveolar lumens. This was followed by more gradual regression, during which the bodies were mostly phagocytosed by macrophages within the epithelium. In the rat, glandular involution was a more gradual and uniform process, with shedding of apoptotic epithelial cells into alveolar lumens being much less conspicuous. Apoptosis of myoepithelial cells was observed in mice, the resulting apoptotic bodies being phagocytosed by intraepithelial macrophages, but was not detected in rats. Apoptosis of capillary endothelial cells caused rapid regression of the capillary beds in both mice and rats. Intraepithelial macrophages increased in number during involution, developed cytoplasmic lipofuscin pigment, and either remained within the epithelium or migrated to the interstitium and regional nodes. Cell loss by apoptosis has been demonstrated during involution and atrophy of a variety of other glands. It characteristically results in shrinkage of a tissue without disruption of its basic architecture.
Structural changes in the luminal epithelium of the porcine uterus between days 10 and 19 of the estrous cycle
Authors: Keys J. L. , King G. J.
Published: February 2005

Light and electron microscopy were used to study the morphology of uterine lu–minal epithelium from 4 or 5 gilts slaughtered Oft each of days 10,13,16, and 19 of the estrous cycle. Ultrastructural evidence indicated that metabolic activity and accumulation of glycogen by the uterine epithelium increased between days 10 and 16 of the estrous cycle. This phase of high synthetic activity had been terminated by day 19, as evidenced by the reduction or absence of glycogen deposits and decreased incidence of organelles associated with synthetic activity. Diffuse degeneration of epithelial cells occurred throughout the period of study but was maximal between days 16 and 19. Mitotic activity indicated that cell replacement also occurred between day 16 and day 19.
Functional units in rainbow trout (Salmo gairdneri, Richardson) liver: III. Morphometric analysis of parenchyma, stroma, and component cell types
Authors: Hampton James A. , Lantz R. Clark , Hinton David E.
Published: February 2005

Hepatic stroma and parenchyma with its component cell types were quantitatively described in adult male and female actively‐spawning 5‐year‐old rainbow trout (Salmo gairdneri, Richardson). Point‐count morphometry of glycol methacrylate sections estimated volume compartments for stroma and parenchyma. Veins composed 85% of the stroma while arteries and bile ducts occupied approximately 6–7% each. Parenchyma accounted for 95% of hepatic volume. Point‐count morphometry of transmission electron micrographs estimated volume compartments as well as numerical and surface density measurements for parenchymal components. Within the hepatic parenchymal compartment, hepatocytes occupied 85% and showed significant sex differences. Female hepatocytes were significantly more numerous but were smaller, only 60% of the volume of male hepatocytes. Since hepatocyte nuclear volume was equal in both sexes, differences were due to reduced cytoplasmic volume in females. Perisinusoidal macrophages of females occupied larger volumes of their respective parenchymal compartments, and their larger mean cytoplasmic volumes suggested activation. Biliary epithelial cells of preductules and ductules were numerous. Ratios of numerical density of hepatocytes to biliary epithelial cells were consistent with a tubular arrangement of hepatocytes. Factors possibly mediating the sexual dimorphism are discussed.